Anti-coagulation factor XI antibodies

11479615 · 2022-10-25

Assignee

Inventors

Cpc classification

International classification

Abstract

Antibodies that bind the apple 3 domain of human coagulation Factor XI and inhibit activation of FXI by coagulation factor XIIa as well as activation of FIX by FXIa are described.

Claims

1. An antibody or antigen binding fragment comprising: (i) at least the six complimentary determining regions (CDRs) of an anti-FXI antibody of the αFXI-18611 family, wherein the antibody of the αFXI-18611 family comprises an HC having the amino acid sequence shown in SEQ ID NO:37 or 39 and an LC having the amino acid sequence shown in SEQ ID NO:26.

2. The antibody or antigen binding fragment of claim 1, wherein the six CDRs of the αFXI-18611 family comprise: HC CDR1 having the amino acid sequence set forth in SEQ ID NO:1, HC CDR2 having the amino acid sequence set forth in SEQ ID NO:2, and HC CDR3 having the amino acid sequence set forth in SEQ ID NO:4, LC-CDR1 having the amino acid sequence set forth in SEQ ID NO:5, LC CDR2 having the amino acid sequence set forth in SEQ ID NO:6, and LC CDR3 having the amino acid sequence set forth in SEQ ID NO:7.

3. The antibody or antigen binding fragment of claim 1, wherein the antibody or antigen binding fragment comprises a HC variable domain comprising the amino acid sequence set forth in SEQ ID NO: 23 or 24 and a LC variable domain comprising the amino acid sequence set forth in SEQ ID NO:25.

4. The antibody or antigen binding fragment of any one of claim 1, wherein the antibody comprises a HC constant domain comprising the amino acid sequence shown in SEQ ID NO:16, 17, 18, or 19.

5. The antibody or antigen binding fragment of any one of claim 1, wherein the antibody comprises a LC constant domain comprising the amino acid sequence shown in SEQ ID NO:20.

6. The antibody or antigen binding fragment of claim 1, wherein the antibody or antibody fragment comprises: (a) a heavy chain (HC) variable domain having the amino acid sequence shown in SEQ ID NO:23 and a light chain (LC) variable domain having the amino acid sequence shown in SEQ ID NO:25; or (b) a heavy chain (HC) variable domain having the amino acid sequence shown in SEQ ID NO: 24 and a light chain (LC) variable domain having the amino acid sequence shown in SEQ ID NO:25.

7. The antibody or antigen binding fragment of claim 6, wherein the antibody further comprises a HC constant domain comprising the amino acid sequence shown in SEQ ID NO:16, 17, 18, 19.

8. The antibody or antigen binding fragment of claim 6, wherein the antibody further comprises a LC constant domain comprising the amino acid sequence shown in SEQ ID NO:20.

9. The antibody or antigen binding fragment of claim 1, wherein the antibody or antigen binding fragment binds the apple 3 domain of coagulation factor XI (FXI) and inhibits activation of FXI and/or Factor XIa-mediated activation of Factor IX.

10. The antibody or antigen binding fragment of claim 1, wherein the antibody comprises: (a) an HC having a constant domain and a variable domain wherein the variable domain comprises a heavy chain comprising a heavy chain-complementary determining region (HC-CDR) 1 having the amino acid sequence shown in SEQ ID NO: 1, a HC-CDR 2 having the amino acid sequence shown in SEQ ID NO:2, and a HC-CDR 3 having the amino acid sequence shown in SEQ ID NO:4; and (b) an LC having a constant domain and a variable domain wherein the variable domain comprises a light chain-complementary determining region (LC-CDR) 1 having the amino acid sequence shown in SEQ ID NO:5, a LC-CDR 2 having the amino acid sequence shown in SEQ ID NO:6, and a LC-CDR 3 having the amino acid sequence shown in SEQ ID NO:7.

11. The antibody or antigen binding fragment of claim 10, wherein the antibody comprises an HC constant domain comprising the amino acid sequence shown in SEQ ID NO:16, 17, 18, or 19.

12. The antibody or antigen binding fragment of claim 10, wherein the antibody comprises an LC constant domain comprising the amino acid sequence shown in SEQ ID NO:20.

13. The antibody or antigen binding fragment of claim 1, wherein the antibody comprises: an HC having the amino acid sequence shown in SEQ ID NO: 37, 39, 49, 51, 73, or 75; and an LC having the amino acid sequence shown in SEQ ID NO:26.

14. A composition comprising the antibody or antigen binding fragment of claim 1 and a pharmaceutically acceptable carrier or diluent.

15. An antibody or antibody fragment comprising a heavy chain variable domain (V.sub.H) comprising the amino acid sequence shown in SEQ ID NO: 23 or 24 and a light chain variable domain (V.sub.L) comprising the amino acid sequence shown in SEQ ID NO:25.

16. The antibody or antibody fragment of claim 15, wherein the antibody further comprises a heavy chain constant domain having the amino acid sequence shown in SEQ ID NO: 16 or 17 and a light chain constant domain having the amino acid sequence shown in SEQ ID NO:20.

17. A composition comprising the antibody or antibody fragment of claim 15 and a pharmaceutically acceptable carrier or diluent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A and FIG. 1B show the coagulation cascade, FXI, FXI mAb, and four new oral anticoagulants (NOACs). FIG. 1A is a cartoon depicting FXI in the coagulation cascade (that is composed of the intrinsic and extrinsic pathways). A FXI-targeting mAb can exert functional neutralization via blocking FXI activation by XIIa and/or thrombin, or FXIa activity on FIX. The antibodies herein may exert dual blockade on FXIa-mediated activation of FIX, and FXI conversion to FXIa mediated by at least FXIIa. The four NOACs (rivaroxaban, apixaban, edoxaban, dabigatran) targeting either FXa or thrombin are shown. FIG. 1B shows the domain structure of FXI. FXI is a dimer composed of identical 80 kDa subunits, and each subunit starting from the N-terminus consists of the four apple domains (1, 2, 3, and 4) and a catalytic domain (CAT). The antibodies disclosed herein bind the apple 3 domain.

(2) FIG. 2 shows the structure of Factor XI and the apple 3 domain with the peptides protected from deuteration by αFXI-18611 and αFXI-18623p family anti-FXI antibodies identified. Arginine 184 residue, a critical residue in the FIX binding exocite is shown. Peptides in the Apple 3 domain with no deuteration differences are light grey. Peptides where no data is available are colored dark grey. The catalytic domain is not shown.

(3) FIGS. 3A and 3B show a deuterium labeling difference heatmap of the FXI amino acid residues bound by anti-FXI antibodies αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa, respectively.

(4) FIGS. 4A, 4B, and 4C shows the amino acid sequence of the HC and LC domains of the αFXI 18611p and αFXI 18611 family antibodies. The Heavy Chain and Light Chain CDRs are identified as HC-CDR1, HC-CDR-2, HC-CDR3, LC-CDR1, LC-CDR2, and LC-CDR3, respectively.

(5) FIGS. 5A and 5B show the amino acid sequence of the HC and LC domains of the αFXI 18623p family antibodies. The Heavy Chain and Light Chain CDRs are identified as HC-CDR1, HC-CDR-2, HC-CDR3, LC-CDR1, LC-CDR2, and LC-CDR3, respectively.

(6) FIG. 6 shows the results of an activated Partial Thromboplastin Time (aPTT) assay of αFXI-18611 IgG4 HC (S228P)(E1)(L105)/LC kappa (A) and αFXI-18623p IgG4 HC (S228P)(Q1)/LC kappa (B) in human plasma, expressed as % increase over baseline.

(7) FIG. 7 shows the results of an activated Partial Thromboplastin Time (aPTT) assay of αFXI-18611 IgG4 HC (S228P)(E1)(L105)/LC kappa (A) and αFXI-18623p IgG4 HC (S228P)(Q1)/LC kappa (B) in cynomolgus monkey plasma, expressed as % increase over baseline.

(8) FIG. 8 shows the results of an activated Partial Thromboplastin Time (aPTT) assay of αFXI-18611 IgG4 HC (S228P)(E1)(L105)/LC kappa (A) and αFXI-18623p IgG4 HC (S228P)(Q1)/LC kappa (B) in rhesus monkey plasma, expressed as % increase over baseline.

(9) FIG. 9 shows a comparison of aPTT results for αFXI-18611 IgG4 HC (S228P)(E1)(L105)/LC kappa in human plasma, cynomolgus monkey, and rhesus monkey plasma expressed as % increase over baseline.

(10) FIG. 10 shows a comparison of aPTT results for αFXI-18623p IgG4 HC (S228P)(Q1)/LC kappa in human plasma, cynomolgus monkey, and rhesus monkey plasma expressed as % increase over baseline.

(11) FIG. 11 shows BIAcore Sensorgrams that show the kinetics of binding of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa to human, cynomolgus and rhesus monkey FXI and other human and NHP coagulation cascade proteins.

(12) FIG. 12 shows BIAcore Sensorgrams that show the kinetics of binding of αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa to human, cynomolgus and rhesus monkey FXI and other human and NHP coagulation cascade proteins.

(13) FIG. 13 shows a schematic of the cynomolgus monkey AV shunt test paradigm. Anesthetized monkeys previously instrumented with femoral arterial and venous catheters were administered vehicle or αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa (antibody) at 0.01-1.0 mg/kg by intravenous bolus (Test Article Administration). An AV shunt was inserted as described in the text (Insert AV shunt). Blood flowed through the AV shunt for 40 minutes. Contact between blood and the silk thread suspended inside of the tubing caused a clot to form. The clots were weighed as described in the text. Blood samples were obtained to measure circulating levels of the antibody, aPTT and PT (stars).

(14) FIGS. 14A-14D show the effects of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa (antibody) on AV shunt clot formation, aPTT and PT in the cynomolgus monkey AV shunt model. FIG. 14A, Clot weight measured after 2 consecutive AV shunts in the same animal. The animals were administered vehicle during the first shunt (Shunt #1), followed by the administration of the antibody (0.01-1.0 mg/kg IV) as shown during the second shunt (Shunt #2). Increasing doses of the antibody resulted in the formation of smaller clots. The percent inhibition of clot weight (FIG. 14B) and the percent change in aPTT (FIG. 14C) increased with increasing plasma concentration of the antibody. In contrast, PT (FIG. 14D) remained relatively unchanged at all concentrations of the antibody.

(15) FIG. 15 shows a schematic of the cynomolgus monkey template bleeding time paradigm. Template bleeding times on the buccal mucosa (inner lip), finger pad and distal tail were determined in anesthetized cynomolgus monkeys at Baseline (prior to treatment) and after the administrations of Treatment #1 (vehicle) and Treatment #2 (vehicle or αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa, 10 mg/kg IV). Blood samples to measure circulating levels of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa, aPTT and PT were collected as shown.

(16) FIG. 16A-16F show the effects of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa on template bleeding times measured in cynomolgus monkeys. Template bleeding times were measured in the buccal mucosal (FIG. 16A, 16D), finger pad (FIG. 16B, 16E) and distal tail (FIG. 16C, 16F). Treatment effects (αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa_vs vehicle) on bleeding times were assessed by comparing absolute bleeding times (left panels) and percentage changes in bleeding times (right panels), with vehicle-vehicle as Treatments #1 and 2 in study session #1, and vehicle-αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa as Treatments #1 and #2 in study session #2, using a one-tailed paired Students t-test.

(17) FIG. 17A shows the Concentration-time Profiles following αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa IV Administration in Rhesus Monkeys. Plasma concentration-time profiles for αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa in Rhesus monkeys are presented. There were 4 animals in each dose group. Each line represents a mean for a particular group.

(18) FIG. 17B shows the aPTT-time Profiles in Rhesus Monkey. The aPTT-time profiles for αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa are presented for each dose group. There were 4 animals in each dose group. Each symbol represents an individual animal's aPTT time profile at each time point. Each line represents a mean for a particular group.

DETAILED DESCRIPTION OF THE INVENTION

(19) The present invention provides anti-coagulation Factor XI antibodies that bind the apple 3 domain of coagulation Factor XI (FXI). These anti-FXI antibodies are inhibitors of FXI activation by Factor XIIa and are useful for inhibiting blood coagulation and associated thrombosis without compromising hemostasis (anti-thrombotic indications). For example, the anti-FXI antibodies may be used for treatment and prevention of venous thromboembolism (VTE), Stroke Prevention in Atrial Fibrillation (SPAF), or treatment and prevention of certain medical device-related thromboembolic disorders (e.g., stents, endovascular stent grafts, catheters (cardiac or venous), continuous flow ventricular assist devices (CF-LVADS), hemodialysis, cardiopulmonary bypass and Extracorporeal Membrane Oxygenation (ECMO), ventricular assist devices (VADS)). Therefore, the anti-FXI antibodies disclosed herein are useful in therapies for treating a thromboembolic disorder or disease in a patient or subject in need of such therapies.

(20) FXI is a homodimeric serine protease having the domain structure shown in FIG. 1B and an integral component of the intrinsic pathway of the coagulation cascade. FXI zymogen can be cleaved by Factor XIIa to its activated form FXIa. FXIa then activates Factor IX and ultimately triggers thrombin generation and clot formation. The anti-FXI antibodies disclosed herein inhibit the conversion of FXI to FXIa (See FIG. 1A).

(21) Anti-FXI antibody molecules were obtained from a fully human synthetic IgG1/kappa library displayed at the surface of engineered yeast strains. The library was screened with FXI or FXIa to identify antibodies capable of binding to human FXI at subnanomolar affinity to human and non-human primate (NHP) FXI and having no binding to human and NHP plasma kallikrein (a protein displaying 56% amino acid identity to FXI), or to other human coagulation cascade proteins (FII//IIa, FVII/VIIa, FIX/IXa, FX/Xa, and FXII/XIIa). Two antibodies were identified that had these properties: αFXI-18611p and αFXI-18623p. These antibodies are fully human antibodies comprising a human kappa (κ) light chain and a human IgG1 (γ1) isotype heavy chain. The antibodies selectively bind to an epitope of the FXI zymogen comprising SEQ ID NOs:82 and 83 located in the apple 3 domain of FXI. These antibodies also bind FXIa with comparable affinity to FXI zymogen.

(22) Antibodies of the αFXI-18611p family comprise heavy chain (HC) complimentary determining regions (CDRs) 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:1, SEQ ID NO:2, and SEQ ID NO:3, respectively, and light chain (LC) CDRs 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:5, SEQ ID NO:6, and SEQ ID NO:7, respectively. αFXI-18611p family includes antibodies comprising a heavy chain (HC) variable domain comprising the amino acid sequence shown in SEQ ID NO:21 or 22 and a light chain (LC) variable domain comprising the amino acid sequence in SEQ ID NO:25.

(23) Antibodies of the αFXI-18611 family comprise heavy chain (HC) complimentary determining regions (CDRs) 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:1, SEQ ID NO:2, and SEQ ID NO:4, respectively, and light chain (LC) CDRs 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:5, SEQ ID NO:6, and SEQ ID NO:7, respectively. αFXI-18611 family includes antibodies comprising a heavy chain (HC) variable domain comprising the amino acid sequence shown in SEQ ID NO:23 or 24 and a light chain (LC) variable domain comprising the amino acid sequence in SEQ ID NO:25.

(24) Antibodies of the αFXI-18623p family comprise HC CDRs 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:8, SEQ ID NO:9, and SEQ ID NO:10, respectively, and LC CDRs 1, 2, and 3 having the amino acid sequences shown in SEQ ID NO:11, SEQ ID NO:12, and SEQ ID NO:13, respectively. αFXI-13716p family includes antibodies comprising a heavy chain (HC) variable domain comprising the amino acid sequence shown in SEQ ID NO:28 or 29 and a light chain (LC) variable domain comprising the amino acid sequence in SEQ ID NO:30. The antibodies of this family were obtained from a different germline than the former families.

(25) The present invention further provides anti-FXI antibodies comprising at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and methods of using the antibodies for treating anti-thrombotic indications, for example SPAF.

(26) In particular aspects, the anti-FXI antibodies comprise at least the HC variable domain of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or a variant thereof wherein the HC variable domain comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(27) In particular aspects, the anti-FXI antibodies comprise at least the LC variable domain of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or a variant thereof wherein the LC variable domain comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(28) In particular aspects, the anti-FXI antibodies comprise at least the HC variable domain of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or a variant thereof wherein the HC variable domain comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and the LC variable domain of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623 family or a variant thereof wherein the LC variable domain comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(29) In particular embodiments, the antibodies herein comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and further comprise a heavy chain (HC) that is of the human IgG1, IgG2, IgG3, or IgG4 isotype and the light chain (LC) may be of the kappa type or lambda type. In other embodiments, the antibodies comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and further may be of the IgM, IgD, IgA, or IgE class. In particular embodiments, the human IgG1, IgG2, IgG3, or IgG4 isotype may include 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(30) In particular embodiments, the antibodies may comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and further comprise an HC constant domain that is of the IgG4 isotype. An IgG4 framework provides an antibody with little or no effector function. In a further aspect of the invention, the antibodies may comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and further comprise HC constant domain that is of the IgG4 isotype fused to an HC variable domain that is of the IgG1 isotype. In a further aspect of the invention, the antibodies may comprise at least the HC variable domain and LC variable domain of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or variants thereof in which the HC and LC variable domains independently comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and further comprise an HC constant domain that is of the IgG4 isotype. In a further aspect of the invention, the antibodies may comprise at least the HC variable domain and LC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or variants thereof in which the HC and LC independently comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and further comprises an HC constant domain that is of the IgG4 isotype.

(31) The antibodies of the present invention further includes, but are not limited to, monoclonal antibodies (including full length monoclonal antibodies), polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), biparatopic antibodies, fully human antibodies, and chimeric antibodies.

(32) In general, the amino acid sequence of the heavy chain of an antibody such as IgG1 or IgG4 has a lysine at the C-terminus of the heavy chain constant domain. In some instances, to improve the homogeneity of an antibody product, the antibody may be produced lacking a C-terminal lysine. The anti-FXI antibodies of the present invention include embodiments in which the C-terminal lysine is present and embodiments in which the C-terminal lysine is absent. For example, an IgG1 HC constant domain may have amino acid sequence shown in SEQ ID NO: 18 or 19 and an IgG4 HC constant domain may have the amino acid sequence shown in SEQ ID NO:16 or 17.

(33) In particular embodiments, the N-terminal amino acid of the HC may be a glutamine residue. In particular embodiments, the N-terminal amino acid of the HC may be a glutamic acid residue. In particular aspects, the N-terminal amino acid is modified to be a glutamic acid residue.

(34) The present invention further provides anti-FXI antigen-binding fragments that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(35) The present invention further provides anti-FXI Fab fragments that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(36) The present invention further provides anti-FXI antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and antigen-binding fragments thereof which comprise an Fc region and methods of use thereof.

(37) The present invention further provides anti-FXI Fab′ fragments that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(38) The present invention further provides anti-FXI F(ab′).sub.2 that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(39) The present invention further provides anti-FXI Fv fragments that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(40) The present invention further provides anti-FXI scFv fragments that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(41) The present invention further provides anti-FXI domain antibodies that comprise at least the three HC CDRs or three LC CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the HC or LC CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof. In an embodiment of the invention, the domain antibody is a single domain antibody or nanobody. In an embodiment of the invention, a domain antibody is a nanobody comprising at least the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family CDRs or embodiments wherein one or more of the CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(42) The present invention further provides anti-FXI bivalent antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(43) The present invention further provides bispecific antibodies and antigen-binding fragments having a binding specificity for FXI and another antigen of interest and methods of use thereof.

(44) Biparatopic antibodies are antibodies having binding specificity for different epitopes on the same antigen. The present invention further provides biparatopic antibodies having first heavy/light chain pair of a first antibody that comprises at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and a second heavy/light chain pair of a second antibody having specificity for an FXI epitope which is different from the epitope recognized by the first heavy/light chain pair.

(45) The present invention further provides anti-FXI antibodies and antigen-binding fragments thereof comprising a first heavy/light chain pair of an antibody that comprises at least the six CDRs of an antibody of the αFXI-18611p or aFX-18611 family or embodiments thereof wherein one or more of the CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and a second heavy/light chain pair of an antibody that comprises at least the six CDRs of an antibody αFXI-18623p family or embodiments thereof wherein one or more of the CDRs has one, two, or three amino substitutions, additions, deletions, or combinations thereof.

(46) The present invention further provides anti-FXI diabodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(47) An antibody that comprises at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof may be modified in some way such that it retains at least 10% of its FXI binding activity (when compared to the parental antibody, i.e., an antibody of the respective αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family) when that activity is expressed on a molar basis. Preferably, an antibody or antigen-binding fragment of the invention retains at least 20%, 50%, 70%, 80%, 90%, 95% or 100% or more of the FXI binding affinity as the parental antibody. It is also intended that an antibody or antigen-binding fragment of the invention can include conservative or non-conservative amino acid substitutions (referred to as “conservative variants” or “function conserved variants” of the antibody) that do not substantially alter its biologic activity.

(48) The present invention further provides isolated anti-FXI antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and antigen-binding fragments thereof and methods of use thereof as well as isolated polypeptide immunoglobulin chains thereof and isolated polynucleotides encoding such polypeptides and isolated vectors including such polynucleotides.

(49) The present invention further provides monoclonal anti-FXI antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and antigen-binding fragments thereof as well as monoclonal compositions comprising a plurality of isolated monoclonal antibodies.

(50) The present invention further provides anti-FXI chimeric antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof.

(51) The present invention includes anti-FXI fully human antibodies that comprise at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and antigen-binding fragments thereof and methods of use thereof. In an embodiment of the invention, a fully human anti-FXI antibody or antigen-binding fragment thereof is the product of isolation from a transgenic animal, e.g., a mouse (e.g., a HUMAB mouse, see e.g., U.S. Pat. Nos. 5,545,806; 5,569,825; 5,625,126; 5,633,425; 5,661,016; 5,770,429; 5,789,650; 5,814,318; 5,874,299 and 5,877,397; and Harding, et al., (1995) Ann. NY Acad. Sci. 764:536 546; or a XENOMOUSE, see e.g., Green et al., 1999, J. Immunol. Methods 231:11-23), which has been genetically modified to have fully human immunoglobulin genes; or the product of isolation from a phage or virus which expresses the immunoglobulin chains of the anti-FXI fully human antibody or antigen-binding fragment thereof.

(52) In some embodiments, different constant domains may be appended to V.sub.L and V.sub.H regions derived from the CDRs provided herein. For example, if a particular intended use of an antibody (or fragment) of the present invention were to call for altered effector functions, a heavy chain constant domain other than human IgG1 may be used, or hybrid IgG1/IgG4 may be utilized.

(53) Although human IgG1 antibodies provide for long half-life and for effector functions, such as complement activation and antibody-dependent cellular cytotoxicity, such activities may not be desirable for all uses of the antibody. In such instances a human IgG4 constant domain, for example, may be used. The present invention includes anti-FXI antibodies and antigen-binding fragments thereof which comprise an IgG4 constant domain, e.g., antagonist human anti-FXI antibodies and fragments, and methods of use thereof. In one embodiment, the IgG4 constant domain can differ from the native human IgG4 constant domain (Swiss-Prot Accession No. P01861.1) at a position corresponding to position 228 in the EU system and position 241 in the KABAT system, wherein the native serine at position 108 (Ser108) of the HC constant domain is replaced with proline (Pro), in order to prevent a potential inter-chain disulfide bond between the cysteine at position 106 (Cys106) and the cysteine at position 109 (Cys109), which correspond to to positions Cys226 and Cys229 in the EU system and positions Cys239 and Cys242 in the KABAT system) that could interfere with proper intra-chain disulfide bond formation. See Angal et al. Mol. Imunol. 30:105 (1993); see also (Schuurman et. al., Mol. Immunol. 38: 1-8, (2001); SEQ ID NOs: 14 and 41). In other instances, a modified IgG1 constant domain which has been modified to reduce effector function can be used, for example, the IgG1 isotype may include substitutions of IgG2 residues at positions 233-236 and IgG4 residues at positions 327, 330 and 331 to greatly reduce ADCC and CDC (Armour et al., Eur J Immunol. 29(8):2613-24 (1999); Shields et al., J Biol Chem. 276(9):6591-604 (2001)). In another embodiment, the IgG HC is modified genetically to lack N-glycosylation of the asparagine (Asn) residue at around position 297. The consensus sequence for N-glycosylation is Asn-Xaa-Ser/Thr (wherein Xaa is any amino acid except Pro); in IgG1 the N-glycosylation consensus sequence is Asn-Ser-Thr. The modification may be achieved by replacing the codon for the Asn at position 297 in the nucleic acid molecule encoding the HC with a codon for another amino acid, for example Gln. Alternatively, the codon for Ser may be replaced with the codon for Pro or the codon for Thr may be replaced with any codon except the codon for Ser. Such modified IgG1 molecules have little or no detectable effector function. Alternatively, all three codons are modified.

(54) In an embodiment of the invention, the anti-FXI antibodies comprising at least the six CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof comprise a full tetrameric structure having two light chains and two heavy chains, including constant regions. The variable regions of each light/heavy chain pair form the antibody binding site. Thus, in general, an intact antibody has two binding sites. Except in bispecific antibodies, the two binding sites are, in general, the same.

(55) In specific embodiments, the present invention provides the anti-FXI antibodies shown in the Table 1.

(56) TABLE-US-00002 TABLE 1 Heavy Light Chain Chain (HC) (LC) SEQ ID SEQ ID Family Antibody NO: NO: αFXI- αFXI-18611p IgG4 HC 33 26 18611P (S228P)(Q1)(M105)/LC kappa αFXI-18611p IgG4 HC 35 26 (S228P)(E1)(M105)/LC kappa αFXI-18611p IgG1 HC 45 26 (Q1)(M105)/LC kappa αFXI-18611p IgG1 HC 47 26 (E1)(M105)/LC kappa αFXI-18611p IgG4 HC 57 26 (S228P)(Q1)(M105)(K-)/LC kappa αFXI-18611p IgG4 HC 59 26 (S228P)(E1)(M105)(K-)/LC kappa αFXI-18611p IgG1 HC 69 26 (Q1)(M105)(K-)/LC kappa αFXI-18611p IgG1 HC 71 26 (E1)(M105)(K-)/LC kappa αFXI- αFXI-18611 IgG4 HC 37 26 18611 (S228P)(Q1)(L105)/LC kappa αFXI-18611 IgG4 HC 39 26 (S228P)(E1)(L105)/LC kappa αFXI-18611 IgG1 HC 49 26 (Q1)(L105)/LC kappa αFXI-18611 IgG1 HC 51 26 (E1)(L105)/LC kappa αFXI-18611 IgG4 HC 61 26 (S228P)(Q1)(L105)(K-)/LC kappa αFXI-18611 IgG4 HC 63 26 (S228P)(E1)(L105)(K-)/LC kappa αFXI-18611 IgG1 HC 73 26 (Q1)(L105)(K-)/LC kappa αFXI-18611 IgG1 HC 75 26 (E1)(L105)(K-)/LC kappa αFXI- αFXI-18623p IgG4 HC 41 31 18623P (S228P)(Q1)/LC kappa αFXI-18623p IgG4 HC 43 31 (S228P)(E1)/LC kappa αFXI-18623p IgG1 HC 53 31 (Q1)/LC kappa αFXI-18623p IgG1 HC 55 31 (E1)/LC kappa αFXI-18623p IgG1 HC 65 31 (S228P)(Q1)(K-)/LC kappa αFXI-18623p IgG4 HC 67 31 (S228P)(E1)(K-)/LC kappa αFXI-18623p IgG1 HC 77 31 (Q1)(K-)/LC kappa αFXI-18623p IgG1 HC 79 31 (E1)(K-)/LC kappa

(57) Epitope mapping by hydrogen-deuterium exchange mass spectrometry (HDX-MS) as described in Example 3 showed that the anti-FXI antibodies comprising the aforementioned HC and LC CDRs bind to a particular epitope on the apple 3 domain comprising SEQ ID NO:82 and SEQ ID NO:83.

(58) Thus, the antibodies disclosed herein bind to the apple 3 domain of FXI and inhibit FXI activation by FXIIa and also behave as allosteric, competitive inhibitors of FIX activation by FXIa. Epitope mapping results suggesting the “footprint” of the αFXI-18623p family on Apple 3 overlaps with the FIX-binding exosite in FXIa.

(59) Pharmaceutical Compositions and Administration

(60) To prepare pharmaceutical or sterile compositions of the anti-FXI antibodies or binding fragment thereof, the antibody or antigen binding fragments thereof is admixed with a pharmaceutically acceptable carrier or excipient. See, e.g., Remington's Pharmaceutical Sciences and U.S. Pharmacopeia: National Formulary, Mack Publishing Company, Easton, Pa. (1984) and continuously updated on the Internet by the U.S. Pharmacopeial Convention (USP) 12601 Twinbrook Parkway, Rockville, Md. 20852-1790, USA.

(61) Formulations of therapeutic and diagnostic agents may be prepared by mixing with acceptable carriers, excipients, or stabilizers in the form of, e.g., lyophilized powders, slurries, aqueous solutions or suspensions (see, e.g., Hardman, et al. (2001) Goodman and Gilman's The Pharmacological Basis of Therapeutics, McGraw-Hill, New York, N.Y.; Gennaro (2000) Remington: The Science and Practice of Pharmacy, Lippincott, Williams, and Wilkins, New York, N.Y.; Avis, et al. (eds.) (1993) Pharmaceutical Dosage Forms: Parenteral Medications, Marcel Dekker, NY; Lieberman, et al. (eds.) (1990) Pharmaceutical Dosage Forms: Tablets, Marcel Dekker, NY; Lieberman, et al. (eds.) (1990) Pharmaceutical Dosage Forms: Disperse Systems, Marcel Dekker, NY; Weiner and Kotkoskie (2000) Excipient Toxicity and Safety, Marcel Dekker, Inc., New York, N.Y.).

(62) In a further embodiment, a composition comprising an antibody or antibody fragment disclosed herein is administered to a subject in accordance with the Physicians' Desk Reference 2017 (Thomson Healthcare; 75st edition (Nov. 1, 2002)).

(63) The mode of administration can vary. Suitable routes of administration is preferably parenteral or subcutaneous, Other routes of administration may include oral, transmucosal, intradermal, direct intraventricular, intravenous, intranasal, inhalation, insufflation, or intra-arterial.

(64) In particular embodiments, the anti-FXI antibody or antigen binding fragment thereof can be administered by an invasive route such as by injection. In further embodiments of the invention, an anti-FXI antibody or antigen binding fragment thereof, or pharmaceutical composition thereof, may be administered intravenously, subcutaneously, intraarterially, or by inhalation, aerosol delivery. Administration by non-invasive routes (e.g., orally; for example, in a pill, capsule or tablet) is also within the scope of the present invention.

(65) Compositions can be administered with medical devices known in the art. For example, a pharmaceutical composition of the invention can be administered by injection with a hypodermic needle, including, e.g., a prefilled syringe or autoinjector.

(66) The pharmaceutical compositions disclosed herein may also be administered with a needleless hypodermic injection device; such as the devices disclosed in U.S. Pat. Nos. 6,620,135; 6,096,002; 5,399,163; 5,383,851; 5,312,335; 5,064,413; 4,941,880; 4,790,824 or 4,596,556.

(67) The pharmaceutical compositions disclosed herein may also be administered by infusion. Examples of well-known implants and modules form administering pharmaceutical compositions include: U.S. Pat. No. 4,487,603, which discloses an implantable micro-infusion pump for dispensing medication at a controlled rate; U.S. Pat. No. 4,447,233, which discloses a medication infusion pump for delivering medication at a precise infusion rate; U.S. Pat. No. 4,447,224, which discloses a variable flow implantable infusion apparatus for continuous drug delivery; U.S. Pat. No. 4,439,196, which discloses an osmotic drug delivery system having multi-chamber compartments. Many other such implants, delivery systems, and modules are well known to those skilled in the art.

(68) The administration regimen depends on several factors, including the serum or tissue turnover rate of the therapeutic antibody, the level of symptoms, the immunogenicity of the therapeutic antibody, and the accessibility of the target cells in the biological matrix. Preferably, the administration regimen delivers sufficient therapeutic antibody to effect improvement in the target disease state, while simultaneously minimizing undesired side effects. Accordingly, the amount of biologic delivered depends in part on the particular therapeutic antibody and the severity of the condition being treated. Guidance in selecting appropriate doses of therapeutic antibodies is available (see, e.g., Wawrzynczak (1996) Antibody Therapy, Bios Scientific Pub. Ltd, Oxfordshire, UK; Kresina (ed.) (1991) Monoclonal Antibodies, Cytokines and Arthritis, Marcel Dekker, New York, N.Y.; Bach (ed.) (1993) Monoclonal Antibodies and Peptide Therapy in Autoimmune Diseases, Marcel Dekker, New York, N.Y.; Baert, et al. (2003) New Engl. J Med. 348:601-608; Milgrom et al. (1999) New Engl. J. Med. 341:1966-1973; Slamon et al. (2001) New Engl. J. Med. 344:783-792; Beniaminovitz et al. (2000) New Engl. J. Med. 342:613-619; Ghosh et al. (2003) New Engl. J Med. 348:24-32; Lipsky et al. (2000) New Engl. J. Med. 343:1594-1602).

(69) Dosage regimens are adjusted to provide the optimum desired response (e.g., a therapeutic response). For example, a single bolus may be administered, several divided doses may be administered over time or the dose may be proportionally reduced or increased as indicated by the exigencies of the therapeutic situation. It is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subjects to be treated; each unit contains a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms described herein are dictated by and directly dependent on (a) the unique characteristics of the antibody or antibody binding fragment and the particular therapeutic effect to be achieved, and (b) the limitations inherent in the art of compounding such an active molecules for the treatment of sensitivity in individuals. (see, e.g., Yang, et al. (2003) New Engl. J. Med. 349:427-434; Herold, et al. (2002) New Engl. J. Med. 346:1692-1698; Liu, et al. (1999) J. Neurol. Neurosurg. Psych. 67:451-456; Portielji, et al. (20003) Cancer Immunol. Immunother. 52:133-144).

(70) Kits

(71) Further provided are kits comprising one or more components that include, but are not limited to, an anti-FXI antibody or antigen-binding fragment, as discussed herein in association with one or more additional components including, but not limited to, a further therapeutic agent, as discussed herein. The antibody or fragment and/or the therapeutic agent can be formulated as a pure composition or in combination with a pharmaceutically acceptable carrier, in a pharmaceutical composition.

(72) In one embodiment, the kit includes an anti-FXI antibody or antigen-binding fragment thereof or a pharmaceutical composition thereof in one container (e.g., in a sterile glass or plastic vial) and a further therapeutic agent in another container (e.g., in a sterile glass or plastic vial).

(73) In another embodiment, the kit comprises a combination of the invention, including an anti-FXI antibody or antigen-binding fragment thereof or pharmaceutical composition thereof in combination with one or more therapeutic agents formulated together, optionally, in a pharmaceutical composition, in a single, common container.

(74) If the kit includes a pharmaceutical composition for parenteral administration to a subject, the kit can include a device for performing such administration. For example, the kit can include one or more hypodermic needles or other injection devices as discussed above. Thus, the present invention includes a kit comprising an injection device and the anti-FXI antibody or antigen-binding fragment thereof, e.g., wherein the injection device includes the antibody or fragment or wherein the antibody or fragment is in a separate vessel.

(75) The kit can include a package insert including information concerning the pharmaceutical compositions and dosage forms in the kit. Generally, such information aids patients and physicians in using the enclosed pharmaceutical compositions and dosage forms effectively and safely. For example, the following information regarding a combination of the invention may be supplied in the insert: pharmacokinetics, pharmacodynamics, clinical studies, efficacy parameters, indications and usage, contraindications, warnings, precautions, adverse reactions, overdosage, proper dosage and administration, how supplied, proper storage conditions, references, manufacturer/distributor information and patent information.

(76) Methods of Making Antibodies and Antigen Binding Fragments Thereof

(77) The anti-FXI antibodies and fragments thereof disclosed herein may also be produced recombinantly. In this embodiment, nucleic acids encoding the antibody molecules may be inserted into a vector (plasmid or viral) and transfected or transformed into a host cell where it may be expressed and secreted from the host cell. There are several methods by which to produce recombinant antibodies which are known in the art.

(78) Mammalian cell lines available as hosts for expression of the antibodies or fragments disclosed herein are well known in the art and include many immortalized cell lines available from the American Type Culture Collection (ATCC). These include, inter alia, Chinese hamster ovary (CHO) cells, NSO, SP2 cells, HeLa cells, baby hamster kidney (BHK) cells, monkey kidney cells (COS), human hepatocellular carcinoma cells (e.g., Hep G2), A549 cells, 3T3 cells, human embryo kidney 293 (HEK-293) cells and a number of other cell lines. Cell lines of particular preference are selected through determining which cell lines have high expression levels. Other cell lines that may be used are insect cell lines, such as Sf9 cells, amphibian cells, bacterial cells, plant cells, filamentous fungus cells (e.g. Trichoderma reesei), and yeast cells (e.g., Saccharomyces cerevisiae or Pichia pastoris). In particular aspects, the host cell may be a prokaryote host cell such as E. coli.

(79) When recombinant expression vectors comprising a nucleic acid molecule encoding the heavy chain or antigen-binding portion or fragment thereof, the light chain and/or antigen-binding fragment thereof are introduced into host cells, the antibodies are produced by culturing the host cells under conditions and for a period of time sufficient to allow for expression of the antibody in the host cells or, more preferably, secretion of the antibody into the culture medium in which the host cells are grown. The antibodies may be recovered from the culture medium and further purified or processed to produce the antibodies of the invention.

(80) In particular aspects, the host cells are transfected with an expression vector comprising a nucleic acid molecule encoding an HC and an LC comprising at least the HC and LC CDRs of an anti-FXI antibody of the αFXI-18611p family, UFXI-18611 family, or UFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(81) In particular aspects, the host cells are transfected with a first expression vector comprising a nucleic acid molecule encoding an HC comprising at least the HC CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and a second expression vector comprising a nucleic acid molecule encoding an LC comprising at least the LC CDRs of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid s substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(82) In particular embodiments, the HC and LC are expressed as a fusion protein in which the N-terminus of the HC and the LC are fused to a leader sequence to facilitate the transport of the antibody through the secretory pathway. Examples of leader sequences that may be used include MSVPTQVLGLLLLWLTDARC (SEQ ID NO: 14) or MEWSWVFLFFLSVTTGVHS (SEQ ID NO:15).

(83) The HC of exemplary antibodies herein may be encoded by a nucleic acid molecule having the nucleotide sequence shown in SEQ ID NOs:34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, or 80.

(84) The LC of exemplary antibodies herein may be encoded by a nucleic acid molecule having the nucleotide sequence shown in SEQ ID NO:27 or 32.

(85) The present invention further provides a plasmid or viral vector comprising a nucleic acid molecule having the amino acid sequence of SEQ ID NOs: 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, or 80. The present invention further provides a plasmid or viral vector comprising a nucleic acid molecule encoding the HC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and a nucleic acid molecule encoding the LC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof.

(86) The present invention further provides a plasmid or viral vector comprising a nucleic acid molecule encoding the HC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family and a plasmid or viral vector comprising a nucleic acid molecule encoding the LC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family.

(87) The present invention further provides a host cell comprising one or more plasmids or viral vectors comprising a nucleic acid molecule encoding the HC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof and a nucleic acid molecule encoding the LC of an anti-FXI antibody of the αFXI-18611p family, αFXI-18611 family, or αFXI-18623p family or embodiments thereof wherein one or more of the six CDRs has one, two, or three amino acid substitutions, additions, deletions, or combinations thereof and/or wherein the HC and/or LC variable region framework comprises 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acid substitutions, additions, deletions, or combinations thereof. In particular embodiments, the host cell is a CHO or HEK-293 host cell.

(88) Antibodies can be recovered from the culture medium using standard protein purification methods. Further, expression of antibodies of the invention (or other moieties therefrom) from production cell lines can be enhanced using a number of known techniques. For example, the glutamine synthetase gene expression system (the GS system) is a common approach for enhancing expression under certain conditions.

(89) In general, glycoproteins produced in a particular cell line or transgenic animal will have a glycosylation pattern that is characteristic for glycoproteins produced in the cell line or transgenic animal (See for example, Croset et al., J. Biotechnol. 161: 336-348 (2012). Therefore, the particular glycosylation pattern of an antibody will depend on the particular cell line or transgenic animal used to produce the antibody. However, all antibodies encoded by the nucleic acid molecules provided herein, or comprising the amino acid sequences provided herein, comprise the instant invention, independent of the glycosylation pattern the antibodies may have.

(90) The following examples are intended to promote a further understanding of the present invention.

General Methods

(91) Standard methods in molecular biology are described Sambrook, Fritsch and Maniatis (1982 & 1989 2nd Edition, 2001 3rd Edition) Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.; Sambrook and Russell (2001) Molecular Cloning, 3rd ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.; Wu (1993) Recombinant DNA, Vol. 217, Academic Press, San Diego, Calif.). Standard methods also appear in Ausbel, et al. (2001) Current Protocols in Molecular Biology, Vols. 1-4, John Wiley and Sons, Inc. New York, N.Y., which describes cloning in bacterial cells and DNA mutagenesis (Vol. 1), cloning in mammalian cells and yeast (Vol. 2), glycoconjugates and protein expression (Vol. 3), and bioinformatics (Vol. 4).

(92) Methods for protein purification including immunoprecipitation, chromatography, electrophoresis, centrifugation, and crystallization are described (Coligan, et al. (2000) Current Protocols in Protein Science, Vol. 1, John Wiley and Sons, Inc., New York). Chemical analysis, chemical modification, post-translational modification, production of fusion proteins, glycosylation of proteins are described (see, e.g., Coligan, et al. (2000) Current Protocols in Protein Science, Vol. 2, John Wiley and Sons, Inc., New York; Ausubel, et al. (2001) Current Protocols in Molecular Biology, Vol. 3, John Wiley and Sons, Inc., NY, NY, pp. 16.0.5-16.22.17; Sigma-Aldrich, Co. (2001) Products for Life Science Research, St. Louis, Mo.; pp. 45-89; Amersham Pharmacia Biotech (2001) BioDirectory, Piscataway, N.J., pp. 384-391). Production, purification, and fragmentation of polyclonal and monoclonal antibodies are described (Coligan, et al. (2001) Current Protocols in Immunology, Vol. 1, John Wiley and Sons, Inc., New York; Harlow and Lane (1999) Using Antibodies, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.; Harlow and Lane, supra). Standard techniques for characterizing ligand/receptor interactions are available (see, e.g., Coligan, et al. (2001) Current Protocols in Immunology, Vol. 4, John Wiley, Inc., New York).

(93) Monoclonal, polyclonal, and humanized antibodies can be prepared (see, e.g., Sheperd and Dean (eds.) (2000) Monoclonal Antibodies, Oxford Univ. Press, New York, N.Y.; Kontermann and Dubel (eds.) (2001) Antibody Engineering, Springer-Verlag, New York; Harlow and Lane (1988) Antibodies A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., pp. 139-243; Carpenter, et al. (2000) J. Immunol. 165:6205; He, et al. (1998) J. Immunol. 160:1029; Tang et al. (1999) J. Biol. Chem. 274:27371-27378; Baca et al. (1997) J. Biol. Chem. 272:10678-10684; Chothia et al. (1989) Nature 342:877-883; Foote and Winter (1992) J. Mol. Biol. 224:487-499; U.S. Pat. No. 6,329,511).

(94) An alternative to humanization is to use human antibody libraries displayed on phage or human antibody libraries in transgenic mice (Vaughan et al. (1996) Nature Biotechnol. 14:309-314; Barbas (1995) Nature Medicine 1:837-839; Mendez et al. (1997) Nature Genetics 15:146-156; Hoogenboom and Chames (2000) Immunol. Today 21:371-377; Barbas et al. (2001) Phage Display: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.; Kay et al. (1996) Phage Display of Peptides and Proteins: A Laboratory Manual, Academic Press, San Diego, Calif.; de Bruin et al. (1999) Nature Biotechnol. 17:397-399).

(95) Antibodies can be conjugated, e.g., to small drug molecules, enzymes, liposomes, polyethylene glycol (PEG). Antibodies are useful for therapeutic, diagnostic, kit or other purposes, and include antibodies coupled, e.g., to dyes, radioisotopes, enzymes, or metals, e.g., colloidal gold (see, e.g., Le Doussal et al. (1991) J. Immunol. 146:169-175; Gibellini et al. (1998) J. Immunol. 160:3891-3898; Hsing and Bishop (1999) J. Immunol. 162:2804-2811; Everts et al. (2002) J. Immunol. 168:883-889).

(96) Methods for flow cytometry, including fluorescence activated cell sorting (FACS), are available (see, e.g., Owens, et al. (1994) Flow Cytometry Principles for Clinical Laboratory Practice, John Wiley and Sons, Hoboken, N.J.; Givan (2001) Flow Cytometry, 2nd ed.; Wiley-Liss, Hoboken, N.J.; Shapiro (2003) Practical Flow Cytometry, John Wiley and Sons, Hoboken, N.J.). Fluorescent reagents suitable for modifying nucleic acids, including nucleic acid primers and probes, polypeptides, and antibodies, for use, e.g., as diagnostic reagents, are available (Molecular Probes (2003) Catalogue, Molecular Probes, Inc., Eugene, Oreg.; Sigma-Aldrich (2003) Catalogue, St. Louis, Mo.).

(97) Standard methods of histology of the immune system are described (see, e.g., Muller-Harmelink (ed.) (1986) Human Thymus: Histopathology and Pathology, Springer Verlag, New York, N.Y.; Hiatt, et al. (2000) Color Atlas of Histology, Lippincott, Williams, and Wilkins, Phila, Pa.; Louis, et al. (2002) Basic Histology: Text and Atlas, McGraw-Hill, New York, N.Y.).

(98) Software packages and databases for determining, e.g., antigenic fragments, leader sequences, protein folding, functional domains, glycosylation sites, and sequence alignments, are available (see, e.g., GenBank, Vector NTI® Suite (Informax, Inc, Bethesda, Md.); GCG Wisconsin Package (Accelrys, Inc., San Diego, Calif.); DeCypher® (TimeLogic Corp., Crystal Bay, Nev.); Menne, et al. (2000) Bioinformatics 16: 741-742; Menne, et al. (2000) Bioinformatics Applications Note 16:741-742; Wren, et al. (2002) Comput. Methods Programs Biomed. 68:177-181; von Heijne (1983) Eur. J. Biochem. 133:17-21; von Heijne (1986) Nucleic Acids Res. 14:4683-4690).

(99) Human FXI and FIX zymogen may be obtained from Haematologic Technologies, Inc. Essex Junction, Vt.; High Molecular Weight (HMW) Kininogen may be obtained from Enzyme Research Laboratories, South Bend, Ind.; and, Ellagic acid may be obtained from Pacific Hemostasis, ThermoFisher, Waltham, Mass.

Example 1

(100) In this example, the binding kinetics of the anti-FXI antibodies αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa and either the human FXI zymogen or non-human primate (NHP) FXI zymogen was measured using the following assays.

(101) Human FXI/FXIa Binding Kinetics Assay Protocol

(102) Binding kinetics and affinity of the protein-protein interaction between anti-FXI antibodies and human FXI zymogen or FXIa were determined using the ProteOn XPR36 (Bio-Rad), an SPR-based (surface plasmon resonance) optical biosensor essentially as follows.

(103) A GLC low-density sensor chip was washed across all vertical and horizontal flow channels with 0.5% sodium dodecyl-sulfate, 50 mM sodium hydroxide, and 100 mM hydrochloric acid for 60 seconds at 30 μL/sec flow rate. The alginate chip surface for all six vertical flow channels (L1-L6) was subsequently activated with 1×EDC/sNHS at 30 μL/sec flow rate for 150 sec. A murine Fc-directed anti-human IgG polyclonal antibody (capture antibody), diluted to 1.25 μg/mL in 10 mM sodium acetate, pH 5.0, was then injected across all six vertical flow channels for 300 sec at a flow rate of 25 uL/sec to bind approximately 300 response units (RU) of capture antibody to the activated chip surface per flow channel by amine-coupling to endogenous lysine. Then, 1M ethanolamine HCl was injected across all six vertical flow channels to neutralize remaining reactive surface amines. Anti-FXI antibodies were then injected at 25 μL/min for 60 seconds, each into a distinct vertical flow channel coated with capture antibody (L2, L3, L4, L5, or L6), at a concentration of 5 μg/mL in 10 mM sodium acetate, pH 5.0, to achieve saturating capture levels of approximately 80 RU; vertical flow channel L1 was injected with 10 mM sodium acetate, pH 5.0 (buffer alone), as a reference control.

(104) After capture of anti-FXI antibodies, running buffer (1×HBS-N, 5 mM CaCl.sub.2, 0.005% P20, pH 7.4) was injected across all horizontal flow channels (A1-A6) for 5 minutes and allowed to dissociate for 20 minutes at 25 μL/min to remove any non-specifically bound anti-FXI antibodies from the chip surface. To measure on-rate (k.sub.a) of human FXI or FXa to captured anti-FXI antibodies, a 6-point titration of human FXI or FXIa (0, 0.25, 0.5, 1.0, 2.0, 4.0 nM diluted in running buffer) was subsequently injected horizontally across all six vertical flow channels for 8 minutes; the bound zymogen was then allowed to dissociate for 60 minutes in running buffer at 25 μL/min to measure off-rate (k.sub.d). Binding kinetics and affinity (K.sub.D) were determined using instrument-specific software (Bio-Rad) and are shown in Table 2.

(105) Non-Human Primate FXI Zymogen/FXIa Binding Kinetics Assay Protocol

(106) Binding kinetics and affinity of the protein-protein interaction between anti-FXI antibodies and non-human primate (NHP: cynomolgus and rhesus) FXI zymogen or FXIa were determined using the ProteOn XPR36 (Bio-Rad), an SPR-based (surface plasmon resonance) optical biosensor.

(107) A GLC low-density sensor chip was washed across all vertical and horizontal flow channels with 0.5% sodium dodecyl-sulfate, 50 mM sodium hydroxide, and 100 mM hydrochloric acid for 60 seconds at 30 μL/sec flow rate. The alginate chip surface for all six vertical flow channels (L1-L6) was subsequently activated with 1×EDC/sNHS at 30 μL/second flow rate for 150 seconds. A murine Fc-directed anti-human IgG polyclonal antibody (capture antibody), diluted to 30 μg/mL in 10 mM sodium acetate, pH 5.0, was then injected across all six vertical flow channels for 150 seconds at a flow rate of 25 μL/sec to achieve saturation-binding of approximately 4500 response units (RU) of capture antibody to the activated chip surface per flow channel by amine-coupling to endogenous lysine. Then 1M ethanolamine HCl was injected across all six vertical flow channels to neutralize any remaining reactive surface amines. Anti-FXI antibodies were then injected at 25 μL/min for 60 sec, each into a distinct vertical flow channel coated with capture antibody (L2, L3, L4, L5, or L6), at a concentration of 0.415 μg/mL in running buffer (1×HBS-N, 5 mM CaCl.sub.2), 0.005% P20, pH 7.4), to achieve capture levels of approximately 40 RU; vertical flow channel L1 was injected with running buffer alone as a reference control. After capture of anti-FXI antibodies, running buffer was injected across all horizontal flow channels (A1-A6) for 5 minutes and allowed to dissociate for 20 minutes at 25 L/minutes to remove non-specifically bound anti-FXI antibodies from the chip surface. To measure on-rate (k.sub.a) of NHP FXI to captured anti-FXI antibodies, a 6-point titration of NHP FXI or FXIa (0, 0.25, 0.5, 1.0, 2.0, 4.0 nM diluted in running buffer) was subsequently injected horizontally across all six vertical flow channels for 8 minutes; the bound FXI zymogen or FXIa was then allowed to dissociate for 60 minutes in running buffer at 25 μL/min to measure off-rate (k.sub.d). Binding kinetics and affinity (K.sub.D) were determined using instrument-specific software (Bio-Rad). The results are shown in Table 2.

(108) TABLE-US-00003 TABLE 2 Binding of αFXI-18623P and αFXI-18611 mAb to FXI/XIa FXI FXIa Affinity Mean Affinity Mean K.sub.D ± SD pM K.sub.D ± SD pM αFXI- αFXI- αFXI- αFXI- Target N 18611 18623p 18611 18623P Human 3 100 ± 38 22.6 ± 2.2 55.4 ± 12.2 37.4 ± 10.4 Cynomolgus 3 180 ± 70 13.0 ± 5.7 89.2 ± 10.4 19.5 ± 0.6  monkey Rhesus 3 52.9 ± 9.6  72.2 ± 31.7  175 ± 62.6 149 ± 3.8  monkey αFXI-18611 = αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa αFXI-18623p = αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa

Example 2

Effect of the Anti-FXI Antibodies on Activation of FXI to FXIa by FXIIa in the Presence of High Molecular Weight (HMW) Kininogen and Ellagic Acid

(109) To measure the effects of anti-FXI antibodies αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa on FXI zymogen activation, coupled enzymatic assays that measure FXIa-mediated proteolysis of a tri-peptide fluorophore (GPR-AFC) may be used to determine if the antibodies inhibit FXI activation per se. For these experiments, anti-FXI antibodies are pre-incubated with FXI zymogen for 1 hour. FXI activation to FXIa is induced by the addition of FXIIa in the presence of HMW Kininogen and ellagic acid. FXIa catalytic activity on the tripeptide fluorophore substrate is subsequently measured as a read for zymogen activation. The coupled assay is also run in the absence of HMW Kininogen as a control. 11-point dose titrations of the anti-FXI antibodies starting at 1 μM concentration with a 3-fold dilution series were pre-incubated with human FXI (Haematologic Technologies, Inc., Cat # HCXI-0150, final concentration 30 nM) and HMW kininogen (Enzyme Research Laboratories, Cat # HK, final concentration 280 nM) in 50 mM HEPES, 150 mM NaCl, 5 mM CaCl.sub.2, 0.1% PEG-8000, pH 7.4 for two hours at 25° C. in Corning 3575 non-binding surface microplate. The activation reaction was then initiated by addition of ellagic-acid-containing Pacific Hemostasis APTT-XL reagent (ThermoFisher Scientific, Cat #100403, 100 μM stock concentration, final concentration 2 μM) and freshly diluted coagulation factor XIIa (Enzyme Research Laboratories, Cat # HFXIIa, final concentration 50 μM). The reaction proceeded at 25° C. for 1 hour when it was quenched by addition of 1 μM corn trypsin inhibitor (Haematologic Technologies, Inc., Cat # CTI-01). The newly activated FXIa enzymatic activity was detected by the rate of cleavage of Z-GPR-AFC substrate (Sigma, Cat # C0980-10MG, final concentration 150 μM) by continuously monitoring the fluorescence at 400/505 nm for 10 minutes using a Tecan Infinite M200 platereader. The % Inhibition for each data point was recalculated from the RFU/min data and analyzed using the log(inhibitor) vs. response four parameters equation with the GraphPad Prism software. The results are shown in Table 3.

(110) Activation of FXI to FXIa by FXIIa in the Absence of HMW Kininogen and Ellagic Acid

(111) 11-point dose titrations of the anti-FXI antibodies of this invention, starting at 1 μM concentration with a 3-fold dilution series were pre-incubated with human FXI (Haematologic Technologies, Inc., Cat # HCXI-0150, final concentration 30 nM) in 50 mM HEPES, 150 mM NaCl, 5 mM CaCl.sub.2, 0.1% PEG-8000, pH 7.4 for two hours at 25° C. in Corning 3575 non-binding surface microplate. The activation reaction was then initiated by addition of freshly diluted coagulation factor XIIa (Enzyme Research Laboratories, Cat # HFXIIa, final concentration 15 nM). The reaction proceeded at 25° C. for 1 hour when it was quenched by addition of 1 μM corn trypsin inhibitor (Haematologic Technologies, Inc., Cat # CTI-01). The newly activated FXIa enzymatic activity was detected by the rate of cleavage of Z-GPR-AFC substrate (Sigma, Cat # C0980-10MG, final concentration 150 μM) by continuously monitoring the fluorescence at 400/505 nm for 10 minutes using a Tecan Infinite M200 platereader. The % Inhibition for each data point was recalculated from the RFU/min data and analyzed using the log(inhibitor) vs. response four parameters equation with the GraphPad Prism software. The results are shown in Table 3.

(112) TABLE-US-00004 TABLE 3 Effect of αFXI-18623p and αFXI-18611 and on FXI Activation by FXIIa FXIIa FXIIa Activation + HK Activation no HK Antibody N Inhibition (IC.sub.50, nM) Inhibition (IC.sub.50, nM) αFXI-18611 3 7.6 ± 3.5 34 ± 20  αFXI-18623p 3 6.0 ± 1.1 14 ± 9.5 αFXI-18611 = αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa αFXI-18623p = αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa IC.sub.50s are given as mean ± SD, n = 3

(113) Together, these mechanistic studies demonstrate that these anti-FXI antibodies functionally neutralize FXI by preventing FXI activation by FXIIa and by inhibiting FXIa catalytic activity on the native substrate.

Example 3

(114) Epitope Mapping of Anti-FXI Antibodies by Hydrogen Deuterium Exchange Mass Spectrometry

(115) Contact areas of αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p-IgG4 (S228P) (Q1)/LC Kappa to human FXI were determined by use of hydrogen deuterium exchange mass spectrometry (HDX-MS) analysis. HDX-MS measures the incorporation of deuterium into the amide backbone of the protein and changes in this incorporation are influenced by the hydrogen's solvent exposure. A comparison of the deuterium exchange levels in antigen-alone samples and antibody-bound samples was done to identify antigen regions that may be in contact with the antibody. Human Factor XI has the amino acid sequence shown in SEQ ID NO:81. Dimeric Factor XI was pre-incubated with the antibodies before incubation in a deuterium buffer. Deuterium incorporation into Factor XI was measured by mass spectrometry.

(116) The human Factor XI regions protected from deuteration by the antibodies are Epitope-A DIFPNTVF (Residues 185-192 of Factor XI; SEQ ID NO:82) and Epitope-B PSTRIKKSKALSG (Residues 247-259 of Factor XI; SEQ ID NO:83). FIGS. 3A and 3B show deuterium labeling difference heatmap of the Factor XI amino acid residues bound by the antibodies αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa, respectively. These amino acid sequences are located on the Apple 3 domain of Factor XI (FIG. 2). No significant deuteration changes were observed in the Apple 1, 2, 4 or catalytic domains, indicating they are not involved in αFXI-18623 binding. Thus, the epitope recognized by αFXI-18623p-IgG4 (S228P)/kappa comprises Epitope A and Epitope B.

Example 4

(117) FIX is the endogenous protein substrate of FXIa, the active protease of FXI zymogen. FXIa activates FIX to FIXa, perpetuating the coagulation cascade. Inhibition of FXIa-mediated activation of FIX is one potential mechanism of action (MOA) for FXI mAbs. To interrogate this MOA, FXIa enzymatic assays using full-length FIX zymogen was developed.

(118) FXIa Protease Activity on a Small Tripeptide Substrate

(119) Anti-FXI antibodies were pre-incubated with human FXIa (Sekisui Diagnostics, Exton, Pa., Cat #4011A, final concentration 100 μM) in 50 mM HEPES, 150 mM NaCl, 5 mM CaCl.sub.2, 0.1% PEG-8000, pH 7.4 for 2 hours at 25° C. in Corning 3575 non-binding surface microplate. FXIa enzymatic activity was determined by measuring the rate of cleavage of Z-GPR-AFC substrate (Sigma, Cat # C0980-10MG, final concentration 100 μM) by continuously monitoring the fluorescence at 400/505 nm for 10 minutes using a Tecan Infinite M200 platereader. The final concentrations of the 11-point dose titration of the antibodies started at 1 μM with a 3-fold dilution series. The % Inhibition for each data point was recalculated from the RFU/minute data and analyzed using the log(inhibitor) vs. response four parameters equation with the GraphPad Prism software. The results are shown in Table 4.

(120) Activation of FIX to FIXa by FXIa

(121) FIX is the endogenous protein substrate of FXIa, the active protease of FXI zymogen. FXIa activates FIX to FIXa, perpetuating the coagulation cascade. Inhibition of FXIa-mediated activation of FIX is one potential MOA for FXI mAbs. To interrogate this MOA, FXIa enzymatic assays using FIX full-length was developed.

(122) 11-point dose titrations of the anti-FXI antibodies, starting at 1 μM concentration with a 3-fold dilution series were pre-incubated with human FXIa (Sekisui Diagnostics, Cat #4011A, final concentration 100 μM) in 50 mM HEPES, 150 mM NaCl, 5 mM CaCl.sub.2, 0.1% PEG-8000, pH 7.4 for 2 hours at 25° C. in Corning 3575 non-binding surface microplate. The activation reaction was then initiated by addition of FIX (Haematologic Technologies, Inc., Cat #HCIX-0040-C, final concentration 300 nM) and preceded at 25° C. for 1 hour when the reaction was quenched by addition of 100 nM of an anti-FXI antibody directed to the catalytic site on the light chain of FXI (anti-FXI antibody 076D-M007-H04 disclosed in WO2013167669). The newly activated FIXa enzymatic activity was detected by the rate of cleavage of cyclohexyl-GGR-AFC substrate (CPC Scientific, Cat #839493, final concentration 300 μM) by continuously monitoring the fluorescence at 400/505 nm for 10 minutes using a Tecan Infinite M200 platereader. The % Inhibition for each data point was recalculated from the RFU/minute data and analyzed using the log(inhibitor) vs. response four parameters equation with the GraphPad Prism software. The results are shown in Table 4.

(123) TABLE-US-00005 TABLE 4 Effect of αFXI-18623p and αFXI-18611 on FXIa Catalytic Activity FXIa IC.sub.50 nM FXIa IC.sub.50 nM (tri-peptide (native, full-length Antibody N substrate) substrate) αFXI-18611 3 >1000 1.0 ± 0.3 αFXI-18623p 3 >1000 0.4 ± 0.2 αFXI-18611 = αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa αFXI-18623p = αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa IC.sub.50s are given as mean ± SD, n = 3

(124) As shown in Table 4, the antibodies did not inhibit FXIa catalytic activity in the enzymatic assay utilizing synthetic, tri-peptide fluorophore substrate, but both antibodies were potent inhibitors of the assay utilizing the native, full length substrate. This data is consistent with the antibodies behaving as allosteric, competitive inhibitors of FIX activation by FXIa, as well as the epitope mapping results of Example 3 suggesting the “footprint” of the antibodies on Apple 3 overlaps with the FIX-binding exosite in FXIa.

Example 5

(125) Autoactivation of FXI to FXIa on Dextran Sulfate

(126) 11-point dose titrations of the anti-FXI antibodies of this invention starting at 1 μM concentration with a 3-fold dilution series were pre-incubated with human FXI (Haematologic Technologies, Inc., Cat # HCXI-0150, final concentration 30 nM) in 50 mM HEPES, 150 mM NaCl, 5 mM CaCl.sub.2, 0.1% PEG-8000, pH 7.4 for 2 hours at 25° C. in Corning 3575 non-binding surface microplate. The autoactivation reaction was then initiated by addition of dextran sulfate (ACROS, Cat #433240250, approximate MW 800 kDa, final concentration 1 nM). The reaction preceded at 25° C. for 1 hour when newly activated FXIa enzymatic activity was detected by the rate of cleavage of Z-GPR-AFC substrate (Sigma, Cat # C0980-10MG, final concentration 150 uM) by continuously monitoring the fluorescence at 400/505 nm for 10 minutes using a Tecan Infinite M200 platereader. The % Inhibition for each data point was recalculated from the RFU/minutes data and analyzed using the log(inhibitor) vs. response four parameters equation with the GraphPad Prism software. The results are shown in Table 5.

(127) TABLE-US-00006 TABLE 5 Effect of αFXI-18623p and αFXI-18611 on FXI Autoactivation Antibody N FXI Autoactivation IC.sub.50 nM αFXI-18611 2 3.3 ± 0.4 αFXI-18623p 2 5.5 ± 4.0 αFXI-18611 = αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa αFXI-18623p = αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa IC.sub.50s are given as mean ± SD, n = 3

Example 6

(128) The ability of the anti-FXI antibodies to block in vitro coagulation was assessed using the activated Partial Thromboplastin Time (aPTT) assay. Activated partial thromboplastin time (aPTT) is a clotting test that measures the activity of the intrinsic and common pathways of coagulation.

(129) Activated Partial Thromboplastin Time (aPTT) Assay

(130) The test is performed in sodium citrated plasmas. Human plasma is obtained by collecting blood from healthy donors of both genders into Na citrate tubes (Sarstedt coagulation 9NC/10 mL). Blood is centrifuged at 1500×g and the plasma is collected. aPTT is checked on each individual donor and those within the normal range (28-40 seconds) are pooled, aliquoted and stored at −80 C. Plasma from other species is obtained commercially (Innovative Research, Novi, Mich.). Test samples are prepared by spiking inhibitors or vehicle into plasma. These spiked samples are incubated (60 minutes, RT) then run on a coagulation analyzer (STA-R Evolution, Stago Diagnostica, Parsippany, N.J.). In general, the analyzer performs the following steps: FXII is activated by addition of ellagic acid (Pacific Hemostasis, ThermoFisher Scientific, Waltham, Mass.), and then time to clot is measured after re-calcification of the sample. Inhibition of FXI will cause aPTT clot time to be prolonged. The results are shown in Table 6. The data is expressed as percent increase over vehicle control clot time and the concentration that causes a 100% (2×) or 50% (1.5×) percent increase of clot time are reported. The aPTT results are shown in FIGS. 6, 7, 8, 9, and 10.

(131) TABLE-US-00007 TABLE 6 Cynomolgus Rhesus Human monkey monkey 2x 1.5 2x 1.5 2x 1.5 Antibody (nM) (nM) (nM) (nM) (nM) (nM) αFXI-18623p 24 19 21 15 22 15 αFXI-18611 37 23 218 42 79 22 αFXI-18611 = αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa αFXI-18623p = αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa

Example 7

(132) Surface Plasmon Resonance Assay for Assessment of Off-Target Binding of Anti-FXI Monoclonal Antibodies to Human and NHP Coagulation Cascade Proteins

(133) A surface plasmon resonance (SPR)-based assay (Biacore T200) was used to determine the potential non-specific interaction of the anti-Factor FXI mAbs, αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa to other human and NHP coagulation cascade proteins (Table 7). Anti-FXI mAbs were captured on a CM5 sensor chip immobilized with anti-human IgG (Fc) capture kit (GE Healthcare) at approximately 500 RU to minimize potential background from co-purifying Igs in plasma derived proteins. Negative control antibody, anti-respiratory syncytial virus (RSV) monoclonal antibody (mAb), was used as a reference and to help reduce background binding of plasma-derived proteins. Binding kinetics was measured using an analyte concentration of FXI at 5 nM; all other coagulation cascade proteins were used at an analyte concentration of 500 nM. Single concentration injections (n=2) were run at 30 μL/min, 25° C., HBS-EP+, pH 7.4.

(134) TABLE-US-00008 Table 7 Recombinant and Plasma Derived Human and NHP Coagulation Cascade Proteins Lot No./ Catalogue No. Vendor Common Name Source 00AJF Merck, Sharp & Rhesus monkey Recombinant Dohme Corp., plasma Kallikrein protein Kenilworth, C-terminal NJ USA His tagged. NCBI Reference Sequence: EHH26351 65AJE Merck, Sharp & Cynomolgus Recombinant Dohme Corp., monkey protein Kenilworth, plasma Kallikrein C-terminal NJ USA His tagged NCBI Reference Sequence: XP_005556538.1 97AJY/ Enzyme Research Human plasma Isolated from HPK 1302 Laboratories preKallikrein human plasma 98AJY/ Enzyme Research Human plasma Isolated from HPKa 1303 Laboratories Kallikrein human plasma 42AHG/ Haematologic Human Factor II Isolated from HCP-0010 Technologies Inc. (α-thrombin) human plasma 50AHK/ Haematologic Human Factor VII Isolated from HCVII-0030 Technologies Inc. human plasma 51AHK Haematologic Human Factor VIIa Isolated from HCVIIA-0031 Technologies Inc. Protease human plasma 38AHG/ Haematologic Human Factor IX Isolated from HCIX-0040 Technologies Inc. human plasma 14AJZ/ Enzyme Research Human Factor IXa Isolated from HFIXa 1080 Laboratories Protease human plasma 15AJZ/ Enzyme Research Human Factor X Isolated from HFX1010 Laboratories human plasma 18AJZ/ Enzyme Research Human Factor Xa Isolated from HFXa 1011 Laboratories Protease human plasma 19AJZ/ Enzyme Research Human Factor XII Isolated from HFXII 1212 Laboratories human plasma 20AJZ/ Enzyme Research Human Factor Xlla Isolated from HFXII 1212a Laboratories Protease human plasma 23AIR/ Haematologic Human FXI Isolated from HCXI-0150-C Technologies Inc. human plasma 41AHG Haematologic Human Factor II Isolated from HCP-0010 Technologies Inc. (Prothrombin) human plasma 82AJK/ R&D Human FXI-His Recombinant 2460-SE tagged protein C-terminal His tagged. Mouse myeloma cell line, NSO derived. NCBI Reference PO3951. 23AFE Merck, Sharp & Anti-RSV SEQ ID NO: 84 Dohme Corp., mAb IgG4 (LC) and Kenilworth, SEQ ID NO: 85 NJ USA (HC)

(135) The kinetics of binding of the anti-Factor FXI mAbs, αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa to human, cynomolgus and rhesus monkey FXI, and, other human and NHP coagulation cascade proteins was measured as described above and are shown in FIG. 11 and FIG. 12). Biacore T200 evaluation software was used to fit data to a 1:1 binding model to determine the association rate constant, k.sub.a (M.sup.−1 s.sup.−1, where “M” equals molar and “s” equals seconds) and the dissociation rate constant, k.sub.d (s.sup.−1). These rate constants were used to calculate the equilibrium dissociation constant, K.sub.D (M).

(136) αFXI-18611 IgG4 HC (S228P)(E1) (L105)/LC Kappa and αFXI-18623p IgG4 HC (S228P)(Q1)/LC Kappa captured on chip showed no cross-reactivity against non-FXI coagulation cascade proteins (FIG. 11 and FIG. 12). These monoclonal antibodies showed expected levels of strong binding to human and cyno (and Rhesus) FXI proteins.

Example 8

(137) Cynomolgus Monkey Femoral Arteriovenous (AV) Shunt Thrombosis Model

(138) The antithrombotic efficacy of the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody, was characterized in vivo in a cynomolgus monkey femoral arteriovenous (AV) shunt model developed at the Merck, Sharp & Dohme Corp. Research Laboratories, Kenilworh, N.J. USA and Palo Alto, Calif. USA.

(139) Study Design:

(140) These studies used a repeated design where each animal received 2 shunts over 2 consecutive test periods (see FIG. 13 Study Schematic). The monkeys were administered non-antibody containing vehicle (20 mM sodium acetate, 9% sucrose, pH 5.5) or the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody (dose range 0.01 to 1.0 mg/kg), during the first and second test periods, respectively. The difference between the clot weight measured during the first (vehicle) and second (antibody) test sessions determined the antithrombotic efficacy. That is, a greater decrease in clot weight during αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody versus vehicle exposure would indicate greater antithrombotic effect. The use of the repeated paired design described above allows for a within animal pre- vs post-treatment assessment of antithrombotic efficacy.

(141) AV Shunt Placement Procedure Details:

(142) To execute this model, anesthetized cynomolgus monkeys were instrumented with femoral arterial and venous catheters. These catheters enabled the insertion and removal of an AV shunt. The AV shunts were composed of TYGON tubing with a piece of silk suture threaded through and suspended across the opening in the tube. To place the AV shunt, both arterial and venous catheters were closed to stop the blood flow. An AV shunt was then placed between the two catheters. The timing of catheter placement and removal is indicated in FIG. 13. Once the shunt was in place, the catheters were opened and blood flowed through the shunt circuit contacting the silk suture. The action of blood contacting the suture promoted clot formation. The AV shunt remained in place for 40 minutes. To remove the AV shunt, both arterial and venous catheters were closed to stop the blood flow through the AV shunt. Then, the shunt was removed and cut open to access the silk suture and blood clot. The blood clot was weighed. The data is reported as the net clot weight which is defined as the total clot weight minus silk suture weight.

(143) The coagulation biomarkers activated partial thromboplastin time (aPTT) and prothrombin time (PT) as well as circulating plasma levels of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody were measured from blood samples collected throughout the experiment as depicted in FIG. 13. aPTT and PT were measured from thawed frozen (−80° C.) citrated plasma collected from cynomolgus monkeys using the Sta Compact Max coagulation analyzer (Stago Diagnostic, Inc). The Stago analyzer measures the time of clot formation using an electro-magnetic mechanical clot detection system. For the aPTT assay fifty microliters of plasma was mixed with 50 μL of ellagic acid mixture (APTT-XL, Pacific Hemostasis; Fisher Diagnostics cat #10.sup.−0402) at 37° C. for 3 minutes. Fifty microliters of 0.025M Calcium Chloride (Sta-CaCl.sub.2 0.025M, Stago Diagnostic, Inc., cat #00367) was added to the mixture, and the time to clot formation was measured. For the PT assay fifty microliters of plasma was incubated at 37° C. for 4 minutes. The timing for clot formation was initiated by adding 100 μL of thromboplastin reagent (Neoplastine C1 Plus 10, Stago Diagnostic, Inc., cat #00667). Plasma was measured as follows. An electrochemiluminescence-based generic hIgG4 immunoassay was used to quantify the antibody in cynomolgus monkey plasma. The assay was established with biotinylated goat anti-human IgG(H+L) from Bethyl (cat # A80-319B) as capture reagent, and sulfoTAG labeled mouse anti-human IgG (Fc specific) from Southern Biotech (cat #9190-01) for detection reagent. This assay was qualified and the lower limit of quantification of the assay was determined to be 40 ng/mL with a minimum required dilution of 100.

(144) FIGS. 14A-14D summarizes the effects of administration of the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody on thrombus formation (FIG. 14A, FIG. 14B), aPTT (FIG. 14C) and PT (FIG. 14D). Table 8 summarizes Effect of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody on Clot Weight in the Cyno AV Shunt Model. Table 9 summarizes the effect of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody on aPTT and PT in the Cyno AV shunt Model.

(145) TABLE-US-00009 TABLE 8 Effect of αFXI-18623p IgG4 HC (S228P)(E1)/ LC Kappa antibody on Clot Weight in the Cyno AV Shunt Model Dose % Inhib. Conc. Antibody Shunt #1 Shunt #2 Clot Antibody (mg/kg) (Vehicle) (Antibody) Weight (μg/mL) 1 772.0 1.0 100%  29.13 0.1 957.0 1.0 100%  2.42 0.01 974.0 1007.0 −3% 0.17 0.03 927.0 935.0 −1% 0.54 0.04 909.0 887.0  2% 0.79 0.05 607.0 472.0 22% 0.91 0.05 710.0 147.0 79% 1.03 0.05 688 66 90% 0.83

(146) TABLE-US-00010 TABLE 9 Effect of αFXI-18623p IgG4 HC (S228P)(E1)/ LC Kappa antibody on aPTT and PT in the Cyno AV shunt Model Dose Conc. Antibody % Change % Change Antibody (mg/kg) aPTT PT (μg/mL) 1 143%  1% 29.13 0.1 93% 1% 2.42 0.01  4% 3% 0.17 0.03 10% 1% 0.54 0.04  5% −2%   0.79 0.05 17% 2% 0.91 0.05 21% 0% 1.03 0.05 42% 3% 0.83

(147) As shown in FIG. 14A, 14B and in Table 8, the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody displayed a dose- and plasma concentration-dependent decrease in clot weight with complete efficacy (90-100% clot reduction) observed at plasma [antibody] of greater than 1 μg/mL (about 10 nM). As shown in FIG. 14C and Table 9, the antibody displayed a dose- and plasma concentration-dependent increase in aPTT. A plasma concentration of 2.4 μg/mL (˜17 nM) of the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody yielded a 93% increase in aPTT, while 29 μg/mL (˜200 nM) of the αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody (at the highest dose tested) resulted in a 143% increase in aPTT. Unlike aPTT, as shown in FIG. 14D and Table 9, PT changed less than 10% across the concentrations of the antibody evaluated, consistent with a selective effect of FXI inhibition on the intrinsic coagulation pathway.

Example 9

(148) Cynomolgus Monkey Template Bleeding Time Model.

(149) The bleeding propensity of the anti-FXI mAb αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa, was characterized in vivo in a cynomolgus monkey template bleeding time model developed at the Merck, Sharp & Dohme Corp. Research Laboratories, Kenilworh, N.J. USA and Palo Alto, Calif. USA. This model has been used previously to demonstrate significant increases in template bleeding times at multiple anatomic sites with triple antiplatelet therapy (Cai et al., Eur. J. Pharmacol. 758:107-114 (2015)).

(150) To execute this model, template bleeding times were determined using spring-loaded lancets on the buccal mucosa (inner lip), finger pad and distal tail at varying time points to induce bleeding.

(151) Bleeding Time Test:

(152) The bleeding time test was performed in anesthetized cynomolgus monkeys as follows. Each test region (buccal mucosa, finger pad or distal tail) was examined to identify a suitable incision site for bleeding inducement. To induce bleeding, a spring-loaded lancet was placed firmly against the selected test site and activated to cause a uniform linear incision. The lancet specifications determined the incision dimensions. Blood from the incision site was allowed to flow freely and was monitored until the bleeding stopped for 30 continuous seconds. This defined the bleeding time (BT). The BT was recorded for each BT site. During the BT determinations, the distal tail incision site was superfused with warm sterile lactated Ringers solution, and the finger pad site was immersed in warm sterile lactated Ringers. Applying lactated ringers improved the ability to see blood flow for these sites.

(153) Study Design:

(154) Each study was comprised of three 30 minute template bleeding time tests (BT) at the three test regions (see FIG. 15 Study Schematic). The first BT determined Baseline bleeding. The second BT occurred 70 minutes after a 3 minute IV infusion (4.17 ml/kg) of non-compound containing vehicle (20 mM sodium acetate, 9% sucrose, pH 5.5)(Treatment #1). The third BT occurred 70 minutes after a 3 minute IV infusion (4.17 ml/kg) of non-compound containing vehicle or αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa (10 mg/kg)(Treatment #2). Bleeding was monitored and bleeding time recorded as described above. The time when bleeding stopped was recorded for each site. Periodic blood samples were collected to determine circulating plasma levels of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa antibody, aPTT and PT.

(155) Each test animal had two study sessions. In study session #1, vehicle followed by vehicle constituted Treatment #1 and Treatment #2 respectively. In study session #2, vehicle followed by 10 mg/kg IV αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa constituted Treatment #1 and Treatment #2 respectively.

(156) The 70 minute time period between the end of the test article infusion and initiation of bleeding time assessments mirrored the timing in the AV shunt model for thrombus mass determination (shunt placement 30 min post treatment+40 min blood flow through the shunt). The 10 mg/kg IV test dose of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa was estimated to achieve 10× the projected human Cmax for αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa based on the PK/PD primate modeling studies described previously.

(157) The coagulation biomarkers activated partial thromboplastin time (aPTT) and prothrombin time (PT) as well as circulating plasma levels of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa were measured from blood samples collected throughout the experiment as depicted in FIG. 15. aPTT and PT were measured from thawed frozen (−80° C.) citrated plasma collected from the animals using the Sta-R Evolution coagulation analyzer (Stago Diagnostic, Inc). The coagulation analyzer measures the time to clot-formation using an electro-magnetic mechanical clot detection system. For the aPTT assay, the analyzer mixes 50 μL of plasma with 50 μL of ellagic acid (APTT-XL, Pacific Hemostasis; Fisher Diagnostics cat #10.sup.−0402) in a cuvette which is then incubated at 37° C. for 3 minutes. 50 μL of 0.025M Calcium Chloride (Sta-CaCl2 0.025M, Stago Diagnostic, Inc., cat #00367) is then added to the mixture to initiate clotting, and the time to clot-formation measured. For the PT assay, 50 μL of plasma was incubated in a cuvette at 37° C. for 4 minutes; clotting was initiated by adding 100 μL of solubilized thromboplastin reagent (Triniclot PT Excel, TCoag, Inc., cat # T1106).

(158) An electrochemiluminescence-based generic hIgG4 immunoassay was used to quantify αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa in rhesus monkey plasma. The assay was established with biotinylated goat anti-huIgG(H+L) from Bethyl (cat # A80-319B) as capture reagent, and sulfoTAG labeled mouse anti-huIgG (Fc specific) from Southern Biotech (cat #9190-01) for detection reagent. This assay was qualified and the lower limit of quantification of the assay was determined to be 41 ng/mL with minimum required dilution of 100.

(159) FIG. 16A-16F summarizes the effects of vehicle and 10 mg/kg IV αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa administration in six cynomolgus monkeys on buccal mucosal (FIG. 16A, 16D), finger pad (FIG. 16B, 16E) and distal tail (FIG. 16C, 16F) template bleeding times. Effects on bleeding times were assessed by comparing absolute bleeding times (left panels) and percentage changes in bleeding times (right panels) with vehicle-vehicle as Treatments #1 and 2 in study session #1, and vehicle-αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa as Treatments #1 and #2 in study session #2. Comparisons of both vehicle vs αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa absolute bleeding times as well as vehicle-vehicle vs vehicle-αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa percentage changes in bleeding times detected no statistically significant changes in bleeding times at any of the test sites with αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa administration at this test dose.

(160) The plasma concentration of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa achieved with the 10 mg/kg IV test dose in the cynomolgus bleeding time study was 290.7±17.2 (mean±SEM) g/ml (˜1938.2 nM). Plasma aPTT values were 31.0±0.5 sec at baseline vs 71.3±1.6 sec following 10 mg/kg IV αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa (2.3-fold increase). Plasma PT values were 12.7±0.1 sec at baseline vs 12.6±0.1 sec following 10 mg/kg IV αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa (no appreciable increase).

Example 10

(161) Pharmacokinetic (PK) and Pharmacodynamic (PD) Evaluation of αFXI-18623p IgG4 HC (S228P)(E1)/LC Kappa Following Multiple Intravenous Administrations in Rhesus Monkeys

(162) The PKPD properties of αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa were characterized in vivo in rhesus monkey. The objective was to evaluate the PK properties and to establish a PK/PD relationship after a total of two weekly doses.

(163) Study Design.

(164) Rhesus monkeys (four animals per dose group) were administered (IV) non-compound vehicle (10 mM Sodium Acetate, pH 5.5, 7% Sucrose, 0.02% PS-80) or αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa at five dose levels of 0.1, 0.3, 1, 3 and 6 mg/kg. The duration of the study was 22 days and 1.5 mL of blood was collected for determination of drug levels and activated partial thromboplastin time (aPTT).

(165) The coagulation biomarker (aPTT) and circulating plasma levels of αFXI-18623p IgG4 HC (S228P)(E1)/LC were measured from blood samples collected throughout the experiment as depicted in Table 10.

(166) TABLE-US-00011 TABLE 10 Sample Collection Schedule Collection Type Time PK Day −3; Day 0: predose (−1 h) and 30 min, 3 h, 6 h, 24 (Day 1), 48 (Day 2), 96 (Day 4) Day 7: predose and 1 h, 6 h, 24 h (Day 8), 48 h (Day 9), 96 h (Day 11), 168 h (Day 14), 264 h (Day 18) and 528 h (Day 22) post second dose PD Day −3: Day 0 : predose (−1 h) and 30 min, (evaluation 3 h, 6 h, 24 (Day 1), 48 (Day 2), 96 (Day 4) of aPTT) Day 7: predose and 1 h, 6 h, 24 h (Day 8), 48 h (Day 9), 96 h (Day 11), 168 h (Day 14), 264 h (Day 18) and 528 h (Day 22) post second dose

(167) aPTT was measured from thawed frozen (−80° C.) citrated plasma collected from the animals using the Sta-R Evolution coagulation analyzer (Stago Diagnostic, Inc). The coagulation analyzer measures the time to clot-formation using an electro-magnetic mechanical clot detection system. For the aPTT assay, the analyzer mixes 50 μL of plasma with 50 μL of ellagic acid (APTT-XL, Pacific Hemostasis; Fisher Diagnostics cat #10-0402) in a cuvette which is then incubated at 37° C. for 3 minutes. 50 μL of 0.025M Calcium Chloride (Sta-CaCl2 0.025M, Stago Diagnostic, Inc., cat #00367) is then added to the mixture to initiate clotting, and the time to clot-formation measured.

(168) An electrochemiluminescence-based generic hIgG4 immunoassay was used to quantify αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa in rhesus monkey plasma. The assay was established with biotinylated goat anti-huIgG(H+L) from Bethyl (cat # A80-319B) as capture reagent, and sulfoTAG labeled mouse anti-huIgG (Fc specific) from Southern Biotech (cat #9190-01) for detection reagent. This assay was qualified and the lower limit of quantification of the assay was determined to be 41 ng/mL with minimum required dilution of 100.

(169) Individual animal plasma concentration-time data for αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa were analyzed using non-compartmental (NCA) methods (Gabrielsson and Weiner, 2000). All PK parameters were estimated or calculated using Phoenix 32 WinNonlin 6.3 (version 6.3.0.395, Certara L. P. St. Louis, Mo., 2012). Noncompartmental analyses utilized Model 201 (IV). All concentration data and PK parameters were rounded to 3 significant figures. Samples with concentration values below the lower limit of quantitation (<LLOQ) were excluded from PK analysis and mean data calculations. For graphical purposes, values<LLOQ were set to be 12 of the minimal reportable concentration for individual animal concentration-time plots.

(170) A sigmoidal E.sub.max response (PK/PD) model was used to characterize the relationship between exposure and aPTT using GraphPad Prism version 7.00 (GraphPad Software Inc). In the model, the E.sub.max value corresponds to the maximum increase in aPTT achieved from baseline and the EC.sub.50 value corresponds to the half-maximal effective concentration. Variability was reported as 95% confidence interval (CI) for the EC50 value provided by the software.

(171) Results.

(172) The individual concentration-time profiles for αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa are depicted in FIG. 17A. Non-linearity was observed for all PK parameters. The mean clearance values decreased from about 8 mL/kg day for the lowest dose tested (0.1 mg/kg) to about 4 mL/kg day for the highest dose tested (6 mg/kg). The aPTT concentration-time profiles are depicted in FIG. 17B. A dose dependent increase in aPTT was observed. The relationship between plasma concentrations of αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa and aPTT best described by the sigmoidal E.sub.max model adequately described this relationship. The estimated EC.sub.50 value for αFXI-18623p IgG4 HC (S228P)(E1)/LC kappa was about 3.6 μg/mL.

(173) TABLE-US-00012 Table of Sequences SEQ ID NO: Description Sequence  1 αFXI- YSISSGYFWG 18611p and αFXI- 18611 HC- CDR1  2 αFXI- SILHSGVTYYNPSLKS 18611p and αFXI- 18611 HC- CDR2  3 αFXI- ARDRTTVSMIEYFQH 18611p HC- CDR3  4 αFXI - ARDRTTVSLIEYFQH 18611 HC- CDR3  5 αFXI- QASQDISNYLN 18611p and αFXI- 18611 LC- CDR1  6 αFXI- DASNLET 18611p and αFXI- 18611 LC- CDR2  7 αFXI- QQFHLLPIT 18611p and αFXI- 18611 LC- CDR3  8 αFXI- GSIYSGAYYWS 18623p HC- CDR1  9 αFXI- SIHYSGLTYYNPSLKS 18623p HC- CDR2 10 αFXI- ARDVDDSSGDEHYGMDV 18623p HC- CDR3 11 αFXI- RASQGIDSWLA 18623p LC- CDR1 12 αFXI- AASSLQS 18623p LC- CDR2 13 αFXI-18623 QQYHIVPIT pLC-CDR3 14 LC Leader MSVPTQVLGLLLLWLTDARC Sequence A 15 HC Leader MEWSWVFLFFLSVTTGVHS Sequence B 16 Human ASTKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALT IgG4 HC SGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKV constant DKRVESKYGPPCPcustom character CPAPEFLGGPSVFLFPPKPKDTLMISRTPEVT domain: CVVVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVS (S228P) VLTVLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYT S at LPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP position PVLDSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKS 108 LSLSLGK replaced with P 17 Human ASTKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALT IgG4 HC SGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKV constant DKRVESKYGPPCPcustom character CPAPEFLGGPSVFLFPPKPKDTLMISRTPEVT domain: CVVVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVS (S228P) VLTVLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYT S at LPPSQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP position PVLDSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKS 108 LSLSLG replaced with P; C-terminal K-less 18 Human ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGAL IgG1 HC TSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTK constant VDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISR domain TPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREP QVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYT QKSLSLSPGK 19 Human ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGAL IgG1 HC TSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTK constant VDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLEPPKPKDTLMISR domain TPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTY C-terminal RVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREP K-less QVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFELYSKLTVDKSRWQQGNVESCSVMHEALHNHYT QKSLSLSPG 20 Human RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNEYPREAKVQWKVDNA kappa LQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQ LC constant GLSSPVTKSFNRGEC domain 21 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC- KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT variable AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSS region; (Q1) (M105) 22 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC- KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT variable AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSS region; (E1) (M105) 23 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611 HC- KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT variable AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSS region; (Q1) (L105) 24 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611 HC- KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT variable AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSS region; (E1) (L105) 25 αFXI- DIQMTQSPSSLSASVGDRVTITCQASQDISNYLNWYQQKPGKA 18611p and PKLLIYDASNLETGVPSRFSGSGSGTDFTFTISSLQPEDIATYYC αFXI- QQFHLLPITFGGGTKVEIK 18611 LC- variable region 26 αFXI- DIQMTQSPSSLSASVGDRVTITCQASQDISNYLNWYQQKPGKA 18611p and PKLLIYDASNLETGVPSRFSGSGSGTDFTFTISSLQPEDIATYYC αFXI- QQFHLLPITFGGGTKVEIKRTVAAPSVFIFPPSDEQLKSGTASVVC 18611 LLNNEYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLT kappa LC LSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC 27 DNA GACATCCAGATGACCCAGAGCCCTAGCAGCCTGAGCGCCAG encoding CGTGGGCGACAGAGTGACCATCACCTGTCAAGCCTCCCAGG αFXI- ACATCTCCAACTACCTGAACTGGTACCAGCAGAAGCCCGGC 18611p and AAGGCTCCCAAGCTGCTGATCTACGACGCCTCCAACCTGGA αFXI- GACCGGCGTGCCTAGCAGATTTAGCGGCAGCGGCTCCGGCA 18611 CAGACTTCACCTTCACCATCAGCTCCCTGCAGCCCGAGGAC kappa LC ATTGCCACCTACTACTGCCAGCAGTTTCACCTGCTGCCTATC ACCTTCGGCGGCGGCACCAAGGTGGAGATCAAAAGGACCG TCGCCGCCCCTAGCGTGTTCATCTTCCCCCCTAGCGACGAGC AGCTCAAGTCCGGCACCGCCAGCGTGGTGTGTCTGCTCAAC AACTTCTACCCCAGGGAGGCCAAGGTGCAGTGGAAGGTGG ACAACGCCCTGCAGAGCGGCAACAGCCAGGAGAGCGTGAC AGAACAGGACAGCAAGGATTCCACATACAGCCTGAGCTCC ACCCTGACCCTGAGCAAGGCCGACTACGAGAAGCACAAGG TGTACGCCTGTGAGGTGACACACCAGGGCCTCAGCTCCCCC GTGACCAAGAGCTTCAACAGAGGCGAATGCTGA 28 αFXI- QVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV variable TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSS region; (Q1) 29 αFXI- EVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV variable TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSS region; (E1) 30 αFXI- DIQMTQSPSSVSASVGDRVTITCRASQGIDSWLAWYQQKPGK 18623p LC- APKLLIYAASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYY variable CQQYHIVPITFGGGTKVEIK region 31 αFXI- DIQMTQSPSSVSASVGDRVTITCRASQGIDSWLAWYQQKPGK 18623p APKLLIYAASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYY kappa LC CQQYHIVPITFGGGTKVEIKRTVAAPSVFIFPPSDEQLKSGTASVV CLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTL TLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC 32 DNA GACATCCAGATGACCCAGAGCCCTAGCAGCGTGAGCGCCA encoding GCGTGGGCGATAGGGTGACCATCACCTGCAGAGCCTCCCAG αFXI- GGCATCGACAGCTGGCTGGCCTGGTACCAGCAGAAGCCCGG 18623p CAAGGCCCCTAAGCTGCTGATCTACGCCGCTAGCAGCCTGC kappa LC AGAGCGGCGTGCCTAGCAGGTTCAGCGGAAGCGGCAGCGG CACCGACTTCACACTGACCATCAGCAGCCTGCAACCTGAGG ACTTCGCCACCTACTACTGCCAGCAGTATCACATCGTGCCC ATCACCTTCGGCGGCGGAACCAAGGTGGAGATTAAGAGGA CCGTGGCCGCCCCCAGCGTGTTTATCTTTCCCCCCAGCGATG AGCAGCTGAAGAGCGGAACCGCCAGCGTGGTGTGCCTGCTG AACAACTTCTACCCCAGAGAGGCCAAGGTGCAGTGGAAGG TGGACAACGCCCTGCAGTCCGGAAACAGCCAGGAGAGCGT GACCGAGCAGGATTCCAAGGATAGCACCTACAGCCTGAGC AGCACCCTGACACTGAGCAAGGCCGACTACGAGAAGCACA AGGTGTACGCCTGTGAGGTGACCCATCAGGGCCTGAGCAGC CCTGTGACCAAGAGCTTCAACAGGGGCGAGTGCTGA 33 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG4 HC AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (S228P) VFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF (Q1) PAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVES (M105) KYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV SQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLGK 34 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG4 HC GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (S228P) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC (Q1) TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC (M105); GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA xxx = CAG GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCCT or CAA (Q) CCACCAAGGGCCCTAGCGTGTTTCCTCTGGCCCCCTGCTCCA GATCCACAAGCGAGAGCACCGCTGCCCTGGGCTGTCTGGTC AAGGACTACTTCCCCGAGCCCGTGACAGTGTCCTGGAACAG CGGCGCCCTGACAAGCGGCGTCCATACATTCCCCGCCGTGC TGCAGTCCAGCGGACTGTATAGCCTGAGCTCCGTGGTGACC GTGCCTTCCAGCAGCCTGGGAACCAAGACATATACCTGCAA CGTGGACCATAAGCCCAGCAACACAAAAGTCGACAAGAGG GTGGAGAGCAAGTACGGACCCCCTTGTCCCCCTTGTCCTGC TCCCGAGTTCCTCGGCGGACCTAGCGTGTTCCTGTTTCCTCC CAAGCCCAAGGATACCCTGATGATCAGCAGGACCCCTGAGG TCACCTGCGTGGTGGTCGACGTGTCCCAGGAGGACCCTGAG GTCCAGTTTAACTGGTACGTGGACGGAGTGGAGGTGCACAA CGCCAAGACCAAGCCCAGAGAGGAGCAGTTCAATTCCACCT ACAGGGTGGTGAGCGTCCTGACCGTGCTGCACCAGGACTGG CTGAATGGAAAGGAGTACAAATGCAAGGTCTCCAACAAGG GCCTCCCTAGCAGCATCGAGAAGACCATCTCCAAGGCCAAG GGCCAGCCTAGGGAGCCCCAGGTGTACACCCTGCCTCCTAG CCAGGAGGAAATGACCAAGAACCAGGTGTCCCTGACATGC CTGGTGAAGGGCTTCTATCCTAGCGACATCGCCGTGGAGTG GGAGAGCAATGGCCAGCCCGAGAATAACTACAAGACCACC CCCCCTGTGCTCGATAGCGACGGCAGCTTCTTTCTGTACAGC AGGCTGACCGTGGACAAGAGCAGGTGGCAAGAGGGCAACG TGTTTAGCTGCTCCGTCATGCACGAGGCCCTGCATAACCACT ACACCCAAAAATCCCTGTCCCTGTCCCTGGGCAAGTGA 35 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG4 HC AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (S228P) VFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF (E1) (M105) PAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVES KYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV SQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLGK 36 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG4 HC GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC S228P); CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC (E1) (M105) TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC xxx = GAA GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA or GAG (E) GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCCT CCACCAAGGGCCCTAGCGTGTTTCCTCTGGCCCCCTGCTCCA GATCCACAAGCGAGAGCACCGCTGCCCTGGGCTGTCTGGTC AAGGACTACTTCCCCGAGCCCGTGACAGTGTCCTGGAACAG CGGCGCCCTGACAAGCGGCGTCCATACATTCCCCGCCGTGC TGCAGTCCAGCGGACTGTATAGCCTGAGCTCCGTGGTGACC GTGCCTTCCAGCAGCCTGGGAACCAAGACATATACCTGCAA CGTGGACCATAAGCCCAGCAACACAAAAGTCGACAAGAGG GTGGAGAGCAAGTACGGACCCCCTTGTCCCCCTTGTCCTGC TCCCGAGTTCCTCGGCGGACCTAGCGTGTTCCTGTTTCCTCC CAAGCCCAAGGATACCCTGATGATCAGCAGGACCCCTGAGG TCACCTGCGTGGTGGTCGACGTGTCCCAGGAGGACCCTGAG GTCCAGTTTAACTGGTACGTGGACGGAGTGGAGGTGCACAA CGCCAAGACCAAGCCCAGAGAGGAGCAGTTCAATTCCACCT ACAGGGTGGTGAGCGTCCTGACCGTGCTGCACCAGGACTGG CTGAATGGAAAGGAGTACAAATGCAAGGTCTCCAACAAGG GCCTCCCTAGCAGCATCGAGAAGACCATCTCCAAGGCCAAG GGCCAGCCTAGGGAGCCCCAGGTGTACACCCTGCCTCCTAG CCAGGAGGAAATGACCAAGAACCAGGTGTCCCTGACATGC CTGGTGAAGGGCTTCTATCCTAGCGACATCGCCGTGGAGTG GGAGAGCAATGGCCAGCCCGAGAATAACTACAAGACCACC CCCCCTGTGCTCGATAGCGACGGCAGCTTCTTTCTGTACAGC AGGCTGACCGTGGACAAGAGCAGGTGGCAAGAGGGCAACG TGTTTAGCTGCTCCGTCATGCACGAGGCCCTGCATAACCACT ACACCCAAAAATCCCTGTCCCTGTCCCTGGGCAAGTGA 37 αFXI-18611 QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG IgG4 HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT S228P) (Q1) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (L105) FPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP AVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESK YGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS QEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLGK 38 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC IgG4 HC CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG S228P); CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA (Q1) (L105) CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG xxx = CAG CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG or CAA (Q) CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCC AGCACCAAGGGCCCTTCCGTCTTCCCTCTGGCCCCTTGCAGC AGAAGCACCTCCGAGTCCACAGCCGCCCTGGGATGCCTCGT GAAGGATTACTTCCCCGAGCCCGTCACAGTCTCCTGGAACT CCGGCGCTCTGACCAGCGGAGTGCACACCTTCCCCGCCGTG CTGCAAAGCAGCGGCCTGTACAGCCTGTCCAGCGTGGTCAC CGTGCCTTCCTCCAGCCTGGGCACCAAGACCTACACATGCA ACGTGGACCACAAGCCTTCCAACACCAAGGTGGACAAGAG AGTGGAAAGCAAGTACGGCCCCCCCTGCCCCCCTTGTCCTG CCCCCGAGTTTCTGGGAGGACCCTCCGTGTTCCTCTTTCCTC CCAAGCCTAAGGACACCCTGATGATCTCCAGGACCCCCGAA GTGACCTGCGTGGTCGTGGACGTGTCCCAGGAGGACCCTGA GGTGCAGTTTAACTGGTACGTGGACGGCGTGGAGGTGCACA ACGCCAAGACCAAGCCCAGGGAGGAGCAGTTCAATAGCAC CTACAGGGTGGTGTCCGTGCTGACCGTGCTGCACCAGGACT GGCTGAACGGCAAAGAGTACAAGTGCAAAGTCAGCAACAA GGGCCTGCCCTCCTCCATCGAGAAGACCATTAGCAAGGCCA AGGGCCAGCCTAGGGAGCCTCAGGTGTACACCCTGCCCCCC AGCCAGGAGGAGATGACCAAGAACCAGGTGTCCCTGACCT GCCTGGTCAAGGGATTTTACCCCAGCGACATCGCTGTGGAA TGGGAGAGCAATGGCCAGCCCGAGAACAACTACAAGACCA CCCCTCCCGTGCTCGATTCCGACGGCAGCTTTTTCCTGTACA GCAGGCTGACCGTGGATAAGAGCAGGTGGCAGGAAGGCAA CGTGTTCTCCTGTTCCGTGATGCATGAGGCCCTGCACAACCA CTACACACAGAAGAGCCTGTCCCTGTCCCTGGGCAAGTGA 39 αFXI-18611 EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG IgG4 HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (S228P) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (E1) (L105) FPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP AVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESK YGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS QEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLGK 40 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC IgG4 HC CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (S228P) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA (Q1) (L105) CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG xxx = GAA CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG or GAG (E) CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCC AGCACCAAGGGCCCTTCCGTCTTCCCTCTGGCCCCTTGCAGC AGAAGCACCTCCGAGTCCACAGCCGCCCTGGGATGCCTCGT GAAGGATTACTTCCCCGAGCCCGTCACAGTCTCCTGGAACT CCGGCGCTCTGACCAGCGGAGTGCACACCTTCCCCGCCGTG CTGCAAAGCAGCGGCCTGTACAGCCTGTCCAGCGTGGTCAC CGTGCCTTCCTCCAGCCTGGGCACCAAGACCTACACATGCA ACGTGGACCACAAGCCTTCCAACACCAAGGTGGACAAGAG AGTGGAAAGCAAGTACGGCCCCCCCTGCCCCCCTTGTCCTG CCCCCGAGTTTCTGGGAGGACCCTCCGTGTTCCTCTTTCCTC CCAAGCCTAAGGACACCCTGATGATCTCCAGGACCCCCGAA GTGACCTGCGTGGTCGTGGACGTGTCCCAGGAGGACCCTGA GGTGCAGTTTAACTGGTACGTGGACGGCGTGGAGGTGCACA ACGCCAAGACCAAGCCCAGGGAGGAGCAGTTCAATAGCAC CTACAGGGTGGTGTCCGTGCTGACCGTGCTGCACCAGGACT GGCTGAACGGCAAAGAGTACAAGTGCAAAGTCAGCAACAA GGGCCTGCCCTCCTCCATCGAGAAGACCATTAGCAAGGCCA AGGGCCAGCCTAGGGAGCCTCAGGTGTACACCCTGCCCCCC AGCCAGGAGGAGATGACCAAGAACCAGGTGTCCCTGACCT GCCTGGTCAAGGGATTTTACCCCAGCGACATCGCTGTGGAA TGGGAGAGCAATGGCCAGCCCGAGAACAACTACAAGACCA CCCCTCCCGTGCTCGATTCCGACGGCAGCTTTTTCCTGTACA GCAGGCTGACCGTGGATAAGAGCAGGTGGCAGGAAGGCAA CGTGTTCTCCTGTTCCGTGATGCATGAGGCCCTGCACAACCA CTACACACAGAAGAGCCTGTCCCTGTCCCTGGGCAAGTGA 41 αFXI- QVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG4 TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (S228P( KGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSG (Q1) VHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDK RVESKYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCV VVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLT VLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPP SQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL DSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSL SLGK 42 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI-18623 CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC pHC-IgG4 ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC (S228P( AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT (Q1) xxx = GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA CAG or AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT CAA (Q) TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCCAGCACCAAAGGACCCTCCGTCTTCCCTCTGGC CCCTTGCTCCAGGAGCACAAGCGAAAGCACAGCCGCCCTGG GCTGCCTGGTGAAGGACTACTTTCCCGAGCCCGTGACCGTG AGCTGGAATAGCGGAGCCCTCACCTCCGGAGTCCACACATT TCCCGCCGTCCTGCAGAGCAGCGGCCTGTACTCCCTGAGCT CCGTGGTGACCGTGCCTTCCTCCAGCCTGGGCACCAAGACC TACACCTGCAACGTGGACCACAAGCCTAGCAATACCAAGGT GGACAAGAGGGTGGAATCCAAGTACGGCCCCCCTTGCCCTC CTTGTCCTGCCCCCGAATTTCTGGGCGGCCCTTCCGTGTTCC TGTTCCCTCCCAAGCCCAAGGATACCCTGATGATCAGCAGG ACCCCTGAGGTGACCTGTGTGGTGGTGGACGTGAGCCAGGA GGACCCCGAGGTGCAGTTCAACTGGTACGTGGATGGCGTGG AAGTGCACAATGCCAAGACAAAGCCCAGGGAGGAGCAGTT CAATAGCACCTACAGGGTGGTCAGCGTGCTCACAGTGCTGC ACCAGGACTGGCTGAACGGAAAGGAGTACAAGTGCAAAGT GTCCAACAAGGGCCTGCCCTCCTCCATCGAAAAGACCATCT CCAAGGCCAAAGGCCAGCCCAGGGAGCCCCAAGTGTATAC CCTCCCCCCTAGCCAGGAGGAAATGACCAAAAACCAGGTCT CCCTGACCTGTCTGGTGAAGGGCTTCTATCCCAGCGACATC GCTGTGGAGTGGGAGAGCAACGGCCAACCCGAGAACAACT ATAAGACCACACCCCCCGTCCTGGACTCCGATGGCTCCTTCT TCCTGTACAGCAGGCTGACCGTCGACAAGTCCAGGTGGCAG GAAGGAAACGTGTTCTCCTGTAGCGTCATGCACGAGGCCCT GCACAACCACTATACCCAGAAGTCCCTGTCCCTGAGCCTGG GCAAGTGA 43 αFXI- EVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG4 TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (S228P( KGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSG (E1) VHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDK RVESKYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCV VVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLT VLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPP SQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL DSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSL SLGK 44 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC- ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG4 AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT (S228P( GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA (E1) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT xxx = GAA TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA or GAG (E) CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCCAGCACCAAAGGACCCTCCGTCTTCCCTCTGGC CCCTTGCTCCAGGAGCACAAGCGAAAGCACAGCCGCCCTGG GCTGCCTGGTGAAGGACTACTTTCCCGAGCCCGTGACCGTG AGCTGGAATAGCGGAGCCCTCACCTCCGGAGTCCACACATT TCCCGCCGTCCTGCAGAGCAGCGGCCTGTACTCCCTGAGCT CCGTGGTGACCGTGCCTTCCTCCAGCCTGGGCACCAAGACC TACACCTGCAACGTGGACCACAAGCCTAGCAATACCAAGGT GGACAAGAGGGTGGAATCCAAGTACGGCCCCCCTTGCCCTC CTTGTCCTGCCCCCGAATTTCTGGGCGGCCCTTCCGTGTTCC TGTTCCCTCCCAAGCCCAAGGATACCCTGATGATCAGCAGG ACCCCTGAGGTGACCTGTGTGGTGGTGGACGTGAGCCAGGA GGACCCCGAGGTGCAGTTCAACTGGTACGTGGATGGCGTGG AAGTGCACAATGCCAAGACAAAGCCCAGGGAGGAGCAGTT CAATAGCACCTACAGGGTGGTCAGCGTGCTCACAGTGCTGC ACCAGGACTGGCTGAACGGAAAGGAGTACAAGTGCAAAGT GTCCAACAAGGGCCTGCCCTCCTCCATCGAAAAGACCATCT CCAAGGCCAAAGGCCAGCCCAGGGAGCCCCAAGTGTATAC CCTCCCCCCTAGCCAGGAGGAAATGACCAAAAACCAGGTCT CCCTGACCTGTCTGGTGAAGGGCTTCTATCCCAGCGACATC GCTGTGGAGTGGGAGAGCAACGGCCAACCCGAGAACAACT ATAAGACCACACCCCCCGTCCTGGACTCCGATGGCTCCTTCT TCCTGTACAGCAGGCTGACCGTCGACAAGTCCAGGTGGCAG GAAGGAAACGTGTTCTCCTGTAGCGTCATGCACGAGGCCCT GCACAACCACTATACCCAGAAGTCCCTGTCCCTGAGCCTGG GCAAGTGA 45 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG1 (Q1) AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (M105) VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF PAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVV VDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP GK 46 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p HC CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG1 (Q1) GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (M105) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC xxx = CAG TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC or CAA (Q) GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCTA GCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAGC AAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGGT GAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAACT CCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGTG CTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGAC AGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGCA ACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAAA GGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCAC CTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTTC TGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCGG ACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACGA AGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTGG AAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGTA CAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTCC ACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGGT GAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATTA GCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATAC CCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTCA GCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATATT GCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAATT ACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTTT TTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGCA ACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCCC TCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCCA GGAAAGTGA 47 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG1 (E1) AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (M105) VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF PAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVV VDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP GK 48 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p HC CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG1 (Q1) GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (M105) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC xxx = GAA TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC or GAG (E) GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCTA GCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAGC AAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGGT GAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAACT CCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGTG CTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGAC AGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGCA ACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAAA GGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCAC CTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTTC TGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCGG ACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACGA AGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTGG AAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGTA CAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTCC ACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGGT GAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATTA GCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATAC CCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTCA GCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATATT GCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAATT ACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTTT TTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGCA ACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCCC TCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCCA GGAAAGTGA 49 αFXI-18611 QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG HC IgG1 KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (Q1)(L105) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV FPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP AVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPK SCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVL HQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP GK 50 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC HC IgG1 CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (Q1)(L105) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA xxx = CAG CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG or CAA (Q) CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCT AGCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAG CAAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGG TGAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAAC TCCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGT GCTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGA CAGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGC AACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAA AGGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCA CCTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTT CTGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCG GACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACG AAGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTG GAAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGT ACAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTC CACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGG TGAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATT AGCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATA CCCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTC AGCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATAT TGCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAAT TACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTT TTTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGC AACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCC CTCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCC AGGAAAGTGA 51 αFXI-18611 EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG HC IgG1 KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (E1)(L105) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV FPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP AVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPK SCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVL HQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP GK 52 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC HC IgG1 CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (E1)(L105) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA xxx = GAA CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG or GAG (E) CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCT AGCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAG CAAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGG TGAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAAC TCCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGT GCTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGA CAGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGC AACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAA AGGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCA CCTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTT CTGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCG GACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACG AAGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTG GAAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGT ACAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTC CACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGG TGAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATT AGCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATA CCCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTC AGCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATAT TGCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAAT TACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTT TTTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGC AACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCC CTCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCC AGGAAAGTGA 53 αFXI- QVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG1 (1Q) TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST KGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSG VHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV TCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVS VLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVY TLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPGK 54 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC  ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG1 (1Q)  AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT xxx = CAG GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA or CAA (Q) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCTAGCACAAAAGGACCAAGCGTGTTTCCACTGGC ACCTAGCAGCAAATCCACCAGCGGCGGAACAGCAGCCCTC GGGTGCCTGGTGAAGGATTACTTCCCTGAGCCAGTCACAGT GTCCTGGAACTCCGGAGCCCTGACATCCGGCGTGCACACCT TCCCCGCTGTGCTGCAATCCAGCGGACTGTATAGCCTCAGC TCCGTCGTGACAGTCCCTTCCAGCAGCCTGGGCACACAGAC TTACATTTGCAACGTGAACCACAAACCTTCCAACACTAAGG TGGACAAAAAGGTGGAACCCAAATCCTGTGATAAGACCCAT ACATGCCCACCTTGTCCCGCTCCTGAGCTGCTGGGGGGACC TTCCGTCTTTCTGTTTCCTCCAAAACCAAAAGACACACTCAT GATCAGCCGGACCCCCGAAGTCACCTGTGTGGTGGTGGACG TCAGCCACGAAGATCCAGAGGTCAAGTTCAATTGGTACGTG GATGGAGTGGAAGTCCACAACGCAAAAACCAAACCTAGAG AAGAACAGTACAATAGCACATACAGGGTGGTGTCCGTCCTG ACAGTGCTCCACCAGGACTGGCTCAATGGCAAAGAGTATAA GTGCAAGGTGAGCAACAAGGCCCTGCCTGCACCAATTGAGA AAACAATTAGCAAGGCAAAGGGGCAGCCACGGGAACCCCA GGTGTATACCCTGCCCCCAAGCCGGGATGAACTGACCAAAA ACCAGGTCAGCCTGACATGCCTGGTGAAAGGGTTTTACCCA AGCGATATTGCCGTCGAGTGGGAGAGCAACGGACAGCCAG AAAACAATTACAAAACCACCCCACCTGTGCTGGACTCCGAT GGGAGCTTTTTCCTGTACAGCAAGCTCACAGTGGACAAGTC CAGATGGCAACAGGGCAACGTGTTTTCCTGCTCCGTGATGC ACGAGGCCCTCCACAACCACTATACACAAAAGTCCCTCTCC CTCAGCCCAGGAAAGTGA 55 αFXI- EVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG1 (1E) TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST KGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSG VHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV TCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVS VLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVY TLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPGK 56 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG1 (1E) AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT xxx = GAA GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA or GAG (E) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCTAGCACAAAAGGACCAAGCGTGTTTCCACTGGC ACCTAGCAGCAAATCCACCAGCGGCGGAACAGCAGCCCTC GGGTGCCTGGTGAAGGATTACTTCCCTGAGCCAGTCACAGT GTCCTGGAACTCCGGAGCCCTGACATCCGGCGTGCACACCT TCCCCGCTGTGCTGCAATCCAGCGGACTGTATAGCCTCAGC TCCGTCGTGACAGTCCCTTCCAGCAGCCTGGGCACACAGAC TTACATTTGCAACGTGAACCACAAACCTTCCAACACTAAGG TGGACAAAAAGGTGGAACCCAAATCCTGTGATAAGACCCAT ACATGCCCACCTTGTCCCGCTCCTGAGCTGCTGGGGGGACC TTCCGTCTTTCTGTTTCCTCCAAAACCAAAAGACACACTCAT GATCAGCCGGACCCCCGAAGTCACCTGTGTGGTGGTGGACG TCAGCCACGAAGATCCAGAGGTCAAGTTCAATTGGTACGTG GATGGAGTGGAAGTCCACAACGCAAAAACCAAACCTAGAG AAGAACAGTACAATAGCACATACAGGGTGGTGTCCGTCCTG ACAGTGCTCCACCAGGACTGGCTCAATGGCAAAGAGTATAA GTGCAAGGTGAGCAACAAGGCCCTGCCTGCACCAATTGAGA AAACAATTAGCAAGGCAAAGGGGCAGCCACGGGAACCCCA GGTGTATACCCTGCCCCCAAGCCGGGATGAACTGACCAAAA ACCAGGTCAGCCTGACATGCCTGGTGAAAGGGTTTTACCCA AGCGATATTGCCGTCGAGTGGGAGAGCAACGGACAGCCAG AAAACAATTACAAAACCACCCCACCTGTGCTGGACTCCGAT GGGAGCTTTTTCCTGTACAGCAAGCTCACAGTGGACAAGTC CAGATGGCAACAGGGCAACGTGTTTTCCTGCTCCGTGATGC ACGAGGCCCTCCACAACCACTATACACAAAAGTCCCTCTCC CTCAGCCCAGGAAAGTGA 57 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG4 HC AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (S228P) VFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF (Q1) PAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVES (M105) (C- KYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV terminal K- SQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ less) DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLG 58 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG4 HC GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (S228P) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC (Q1) (M105); TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC xxx = CAG GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA or CAA (Q) GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCCT (C-terminal CCACCAAGGGCCCTAGCGTGTTTCCTCTGGCCCCCTGCTCCA K-less) GATCCACAAGCGAGAGCACCGCTGCCCTGGGCTGTCTGGTC AAGGACTACTTCCCCGAGCCCGTGACAGTGTCCTGGAACAG CGGCGCCCTGACAAGCGGCGTCCATACATTCCCCGCCGTGC TGCAGTCCAGCGGACTGTATAGCCTGAGCTCCGTGGTGACC GTGCCTTCCAGCAGCCTGGGAACCAAGACATATACCTGCAA CGTGGACCATAAGCCCAGCAACACAAAAGTCGACAAGAGG GTGGAGAGCAAGTACGGACCCCCTTGTCCCCCTTGTCCTGC TCCCGAGTTCCTCGGCGGACCTAGCGTGTTCCTGTTTCCTCC CAAGCCCAAGGATACCCTGATGATCAGCAGGACCCCTGAGG TCACCTGCGTGGTGGTCGACGTGTCCCAGGAGGACCCTGAG GTCCAGTTTAACTGGTACGTGGACGGAGTGGAGGTGCACAA CGCCAAGACCAAGCCCAGAGAGGAGCAGTTCAATTCCACCT ACAGGGTGGTGAGCGTCCTGACCGTGCTGCACCAGGACTGG CTGAATGGAAAGGAGTACAAATGCAAGGTCTCCAACAAGG GCCTCCCTAGCAGCATCGAGAAGACCATCTCCAAGGCCAAG GGCCAGCCTAGGGAGCCCCAGGTGTACACCCTGCCTCCTAG CCAGGAGGAAATGACCAAGAACCAGGTGTCCCTGACATGC CTGGTGAAGGGCTTCTATCCTAGCGACATCGCCGTGGAGTG GGAGAGCAATGGCCAGCCCGAGAATAACTACAAGACCACC CCCCCTGTGCTCGATAGCGACGGCAGCTTCTTTCTGTACAGC AGGCTGACCGTGGACAAGAGCAGGTGGCAAGAGGGCAACG TGTTTAGCTGCTCCGTCATGCACGAGGCCCTGCATAACCACT ACACCCAAAAATCCCTGTCCCTGTCCCTGGGC 59 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG4 HC AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (S228P) VFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF (E1) (M105) PAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVES (C-terminal KYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDV K-less) SQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLG 60 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG4 HC GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC S228P); CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC (E1) (M105) TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC xxx = GAA GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA or GAG (E) GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCCT (C-terminal CCACCAAGGGCCCTAGCGTGTTTCCTCTGGCCCCCTGCTCCA K-less) GATCCACAAGCGAGAGCACCGCTGCCCTGGGCTGTCTGGTC AAGGACTACTTCCCCGAGCCCGTGACAGTGTCCTGGAACAG CGGCGCCCTGACAAGCGGCGTCCATACATTCCCCGCCGTGC TGCAGTCCAGCGGACTGTATAGCCTGAGCTCCGTGGTGACC GTGCCTTCCAGCAGCCTGGGAACCAAGACATATACCTGCAA CGTGGACCATAAGCCCAGCAACACAAAAGTCGACAAGAGG GTGGAGAGCAAGTACGGACCCCCTTGTCCCCCTTGTCCTGC TCCCGAGTTCCTCGGCGGACCTAGCGTGTTCCTGTTTCCTCC CAAGCCCAAGGATACCCTGATGATCAGCAGGACCCCTGAGG TCACCTGCGTGGTGGTCGACGTGTCCCAGGAGGACCCTGAG GTCCAGTTTAACTGGTACGTGGACGGAGTGGAGGTGCACAA CGCCAAGACCAAGCCCAGAGAGGAGCAGTTCAATTCCACCT ACAGGGTGGTGAGCGTCCTGACCGTGCTGCACCAGGACTGG CTGAATGGAAAGGAGTACAAATGCAAGGTCTCCAACAAGG GCCTCCCTAGCAGCATCGAGAAGACCATCTCCAAGGCCAAG GGCCAGCCTAGGGAGCCCCAGGTGTACACCCTGCCTCCTAG CCAGGAGGAAATGACCAAGAACCAGGTGTCCCTGACATGC CTGGTGAAGGGCTTCTATCCTAGCGACATCGCCGTGGAGTG GGAGAGCAATGGCCAGCCCGAGAATAACTACAAGACCACC CCCCCTGTGCTCGATAGCGACGGCAGCTTCTTTCTGTACAGC AGGCTGACCGTGGACAAGAGCAGGTGGCAAGAGGGCAACG TGTTTAGCTGCTCCGTCATGCACGAGGCCCTGCATAACCACT ACACCCAAAAATCCCTGTCCCTGTCCCTGGGC 61 αFXI-18611 QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG IgG4 HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT S228P) (Q1) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (L105) (C- FPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP terminal K- AVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESK less) YGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS QEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLG 62 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC IgG4 HC CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG S228P); CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA (Q1) (L105) CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG xxx = CAG CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG or CAA (Q) CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC (C-terminal AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCC K-less) AGCACCAAGGGCCCTTCCGTCTTCCCTCTGGCCCCTTGCAGC AGAAGCACCTCCGAGTCCACAGCCGCCCTGGGATGCCTCGT GAAGGATTACTTCCCCGAGCCCGTCACAGTCTCCTGGAACT CCGGCGCTCTGACCAGCGGAGTGCACACCTTCCCCGCCGTG CTGCAAAGCAGCGGCCTGTACAGCCTGTCCAGCGTGGTCAC CGTGCCTTCCTCCAGCCTGGGCACCAAGACCTACACATGCA ACGTGGACCACAAGCCTTCCAACACCAAGGTGGACAAGAG AGTGGAAAGCAAGTACGGCCCCCCCTGCCCCCCTTGTCCTG CCCCCGAGTTTCTGGGAGGACCCTCCGTGTTCCTCTTTCCTC CCAAGCCTAAGGACACCCTGATGATCTCCAGGACCCCCGAA GTGACCTGCGTGGTCGTGGACGTGTCCCAGGAGGACCCTGA GGTGCAGTTTAACTGGTACGTGGACGGCGTGGAGGTGCACA ACGCCAAGACCAAGCCCAGGGAGGAGCAGTTCAATAGCAC CTACAGGGTGGTGTCCGTGCTGACCGTGCTGCACCAGGACT GGCTGAACGGCAAAGAGTACAAGTGCAAAGTCAGCAACAA GGGCCTGCCCTCCTCCATCGAGAAGACCATTAGCAAGGCCA AGGGCCAGCCTAGGGAGCCTCAGGTGTACACCCTGCCCCCC AGCCAGGAGGAGATGACCAAGAACCAGGTGTCCCTGACCT GCCTGGTCAAGGGATTTTACCCCAGCGACATCGCTGTGGAA TGGGAGAGCAATGGCCAGCCCGAGAACAACTACAAGACCA CCCCTCCCGTGCTCGATTCCGACGGCAGCTTTTTCCTGTACA GCAGGCTGACCGTGGATAAGAGCAGGTGGCAGGAAGGCAA CGTGTTCTCCTGTTCCGTGATGCATGAGGCCCTGCACAACCA CTACACACAGAAGAGCCTGTCCCTGTCCCTGGGC 63 αFXI-18611 EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG IgG4 HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (S228P) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (E1) (L105) FPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP (C-terminal AVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVESK K-less) YGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS QEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQ DWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEE MTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDG SFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSLSLG 64 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC IgG4 HC CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (S228P) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA (Q1) (L105) CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG xxx = GAA CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG or GAG (E) CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC (C-terminal AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCC K-less) AGCACCAAGGGCCCTTCCGTCTTCCCTCTGGCCCCTTGCAGC AGAAGCACCTCCGAGTCCACAGCCGCCCTGGGATGCCTCGT GAAGGATTACTTCCCCGAGCCCGTCACAGTCTCCTGGAACT CCGGCGCTCTGACCAGCGGAGTGCACACCTTCCCCGCCGTG CTGCAAAGCAGCGGCCTGTACAGCCTGTCCAGCGTGGTCAC CGTGCCTTCCTCCAGCCTGGGCACCAAGACCTACACATGCA ACGTGGACCACAAGCCTTCCAACACCAAGGTGGACAAGAG AGTGGAAAGCAAGTACGGCCCCCCCTGCCCCCCTTGTCCTG CCCCCGAGTTTCTGGGAGGACCCTCCGTGTTCCTCTTTCCTC CCAAGCCTAAGGACACCCTGATGATCTCCAGGACCCCCGAA GTGACCTGCGTGGTCGTGGACGTGTCCCAGGAGGACCCTGA GGTGCAGTTTAACTGGTACGTGGACGGCGTGGAGGTGCACA ACGCCAAGACCAAGCCCAGGGAGGAGCAGTTCAATAGCAC CTACAGGGTGGTGTCCGTGCTGACCGTGCTGCACCAGGACT GGCTGAACGGCAAAGAGTACAAGTGCAAAGTCAGCAACAA GGGCCTGCCCTCCTCCATCGAGAAGACCATTAGCAAGGCCA AGGGCCAGCCTAGGGAGCCTCAGGTGTACACCCTGCCCCCC AGCCAGGAGGAGATGACCAAGAACCAGGTGTCCCTGACCT GCCTGGTCAAGGGATTTTACCCCAGCGACATCGCTGTGGAA TGGGAGAGCAATGGCCAGCCCGAGAACAACTACAAGACCA CCCCTCCCGTGCTCGATTCCGACGGCAGCTTTTTCCTGTACA GCAGGCTGACCGTGGATAAGAGCAGGTGGCAGGAAGGCAA CGTGTTCTCCTGTTCCGTGATGCATGAGGCCCTGCACAACCA CTACACACAGAAGAGCCTGTCCCTGTCCCTGGGC 65 αFXI- QVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG4 TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (S228P( KGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSG (Q1)(C- VHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYT(NVDHKPSNTKVDK terminal K- RVESKYGPPCPPCPAPEFLGGPSVFLEPPKPKDTLMISRTPEVTCV less) VVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLT VLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPP SQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL DSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSL SLG 66 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC- ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG4 AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT (S228P( GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA (Q1) xxx = AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT CAG or TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA CAA (Q) CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG (C -terminal AGCAGCGCCAGCACCAAAGGACCCTCCGTCTTCCCTCTGGC K-less) CCCTTGCTCCAGGAGCACAAGCGAAAGCACAGCCGCCCTGG GCTGCCTGGTGAAGGACTACTTTCCCGAGCCCGTGACCGTG AGCTGGAATAGCGGAGCCCTCACCTCCGGAGTCCACACATT TCCCGCCGTCCTGCAGAGCAGCGGCCTGTACTCCCTGAGCT CCGTGGTGACCGTGCCTTCCTCCAGCCTGGGCACCAAGACC TACACCTGCAACGTGGACCACAAGCCTAGCAATACCAAGGT GGACAAGAGGGTGGAATCCAAGTACGGCCCCCCTTGCCCTC CTTGTCCTGCCCCCGAATTTCTGGGCGGCCCTTCCGTGTTCC TGTTCCCTCCCAAGCCCAAGGATACCCTGATGATCAGCAGG ACCCCTGAGGTGACCTGTGTGGTGGTGGACGTGAGCCAGGA GGACCCCGAGGTGCAGTTCAACTGGTACGTGGATGGCGTGG AAGTGCACAATGCCAAGACAAAGCCCAGGGAGGAGCAGTT CAATAGCACCTACAGGGTGGTCAGCGTGCTCACAGTGCTGC ACCAGGACTGGCTGAACGGAAAGGAGTACAAGTGCAAAGT GTCCAACAAGGGCCTGCCCTCCTCCATCGAAAAGACCATCT CCAAGGCCAAAGGCCAGCCCAGGGAGCCCCAAGTGTATAC CCTCCCCCCTAGCCAGGAGGAAATGACCAAAAACCAGGTCT CCCTGACCTGTCTGGTGAAGGGCTTCTATCCCAGCGACATC GCTGTGGAGTGGGAGAGCAACGGCCAACCCGAGAACAACT ATAAGACCACACCCCCCGTCCTGGACTCCGATGGCTCCTTCT TCCTGTACAGCAGGCTGACCGTCGACAAGTCCAGGTGGCAG GAAGGAAACGTGTTCTCCTGTAGCGTCATGCACGAGGCCCT GCACAACCACTATACCCAGAAGTCCCTGTCCCTGAGCCTGG GC 67 αFXI- EVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC- GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG4 TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (S228P( KGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSG (E1) (C- VHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDK terminal K- RVESKYGPPCPPCPAPEFLGGPSVFLEPPKPKDTLMISRTPEVTCV less) VVDVSQEDPEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLT VLHQDWLNGKEYKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPP SQEEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVL DSDGSFFLYSRLTVDKSRWQEGNVFSCSVMHEALHNHYTQKSLSL SLG 68 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC- ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG4 AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT (S228P( GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA (E1) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT xxx = GAA TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA or GAG (E) CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG (C-terminal AGCAGCGCCAGCACCAAAGGACCCTCCGTCTTCCCTCTGGC K-less) CCCTTGCTCCAGGAGCACAAGCGAAAGCACAGCCGCCCTGG GCTGCCTGGTGAAGGACTACTTTCCCGAGCCCGTGACCGTG AGCTGGAATAGCGGAGCCCTCACCTCCGGAGTCCACACATT TCCCGCCGTCCTGCAGAGCAGCGGCCTGTACTCCCTGAGCT CCGTGGTGACCGTGCCTTCCTCCAGCCTGGGCACCAAGACC TACACCTGCAACGTGGACCACAAGCCTAGCAATACCAAGGT GGACAAGAGGGTGGAATCCAAGTACGGCCCCCCTTGCCCTC CTTGTCCTGCCCCCGAATTTCTGGGCGGCCCTTCCGTGTTCC TGTTCCCTCCCAAGCCCAAGGATACCCTGATGATCAGCAGG ACCCCTGAGGTGACCTGTGTGGTGGTGGACGTGAGCCAGGA GGACCCCGAGGTGCAGTTCAACTGGTACGTGGATGGCGTGG AAGTGCACAATGCCAAGACAAAGCCCAGGGAGGAGCAGTT CAATAGCACCTACAGGGTGGTCAGCGTGCTCACAGTGCTGC ACCAGGACTGGCTGAACGGAAAGGAGTACAAGTGCAAAGT GTCCAACAAGGGCCTGCCCTCCTCCATCGAAAAGACCATCT CCAAGGCCAAAGGCCAGCCCAGGGAGCCCCAAGTGTATAC CCTCCCCCCTAGCCAGGAGGAAATGACCAAAAACCAGGTCT CCCTGACCTGTCTGGTGAAGGGCTTCTATCCCAGCGACATC GCTGTGGAGTGGGAGAGCAACGGCCAACCCGAGAACAACT ATAAGACCACACCCCCCGTCCTGGACTCCGATGGCTCCTTCT TCCTGTACAGCAGGCTGACCGTCGACAAGTCCAGGTGGCAG GAAGGAAACGTGTTCTCCTGTAGCGTCATGCACGAGGCCCT GCACAACCACTATACCCAGAAGTCCCTGTCCCTGAGCCTGG GC 69 αFXI- QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG1 (Q1) AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (M105)(C- VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF terminal K- PAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP less) KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVV VDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP G 70 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p HC CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG1 (Q1) GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (M105) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC xxx = CAG TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC or CAA (Q) GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA (C -terminal GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCTA K-less) GCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAGC AAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGGT GAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAACT CCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGTG CTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGAC AGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGCA ACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAAA GGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCAC CTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTTC TGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCGG ACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACGA AGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTGG AAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGTA CAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTCC ACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGGT GAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATTA GCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATAC CCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTCA GCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATATT GCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAATT ACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTTT TTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGCA ACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCCC TCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCCA GGA 71 αFXI- EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG 18611p HC KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT IgG1 (E1) AADTAVYYCARDRTTVSMIEYFQHWGQGTLVTVSSASTKGPS (M105)(C- VFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTF terminal K- PAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP less) KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVV VDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTV LHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP G 72 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGCCTGGTGAAGCCT encoding AGCGAGACACTGTCCCTGACCTGCGCCGTGAGCGGCTACAG αFXI- CATCTCCAGCGGCTATTTCTGGGGATGGATCAGACAGCCCC 18611p HC CTGGCAAGGGCCTGGAATGGATCGGTTCTATCCTGCACTCC IgG1 (Q1) GGCGTGACATACTATAACCCTAGCCTGAAGAGCAGGGTGAC (M105) CATCTCCGTGGATACCAGCAAGAATCAGTTCAGCCTGAAGC xxx = GAA TCAGCAGCGTGACCGCCGCCGATACCGCTGTGTACTACTGC or GAG (E) GCCAGAGACAGGACCACCGTCTCCATGATCGAGTACTTCCA (C-terminal GCACTGGGGCCAAGGCACCCTGGTCACCGTGTCCTCCGCTA K-less) GCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAGC AAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGGT GAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAACT CCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGTG CTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGAC AGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGCA ACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAAA GGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCAC CTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTTC TGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCGG ACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACGA AGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTGG AAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGTA CAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTCC ACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGGT GAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATTA GCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATAC CCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTCA GCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATATT GCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAATT ACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTTT TTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGCA ACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCCC TCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCCA GGA 73 αFXI-18611 QVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG HC IgG1 KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (Q1)(L105) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (C-terminal FPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP K-less) AVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPK SCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVL HQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP G 74 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC HC IgG1 CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (Q1)(L105) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA xxx = CAG CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG or CAA (Q) CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG (C-terminal CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC K-less) AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCT AGCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAG CAAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGG TGAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAAC TCCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGT GCTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGA CAGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGC AACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAA AGGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCA CCTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTT CTGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCG GACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACG AAGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTG GAAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGT ACAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTC CACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGG TGAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATT AGCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATA CCCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTC AGCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATAT TGCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAAT TACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTT TTTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGC AACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCC CTCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCC AGGA 75 αFXI-18611 EVQLQESGPGLVKPSETLSLTCAVSGYSISSGYFWGWIRQPPG HC IgG1 KGLEWIGSILHSGVTYYNPSLKSRVTISVDTSKNQFSLKLSSVT (E1)(L105) AADTAVYYCARDRTTVSLIEYFQHWGQGTLVTVSSASTKGPSV (C-terminal FPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFP K-less) AVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPK SCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVV DVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVL HQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPS RDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDS DGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSP G 76 DNA xxxGTCCAGCTGCAGGAGAGCGGCCCTGGACTCGTGAAGCC encoding CTCCGAAACCCTGAGCCTCACATGCGCCGTCTCCGGATACA αFXI-18611 GCATCAGCAGCGGATACTTCTGGGGCTGGATCAGACAGCCC HC IgG1 CCCGGCAAAGGCCTGGAGTGGATCGGTTCTATTCTCCACAG (E1)(L105) CGGCGTGACATACTACAACCCCTCCCTGAAGAGCAGGGTGA xxx = GAA CCATCAGCGTGGACACCTCCAAGAACCAGTTTTCCCTCAAG or GAG (E) CTGAGCAGCGTGACCGCCGCTGACACAGCCGTGTATTACTG (C-terminal CGCCAGGGACAGGACCACCGTGTCCCTGATTGAGTACTTCC K-less) AGCATTGGGGCCAGGGCACACTGGTGACCGTCAGCAGCGCT AGCACAAAAGGACCAAGCGTGTTTCCACTGGCACCTAGCAG CAAATCCACCAGCGGCGGAACAGCAGCCCTCGGGTGCCTGG TGAAGGATTACTTCCCTGAGCCAGTCACAGTGTCCTGGAAC TCCGGAGCCCTGACATCCGGCGTGCACACCTTCCCCGCTGT GCTGCAATCCAGCGGACTGTATAGCCTCAGCTCCGTCGTGA CAGTCCCTTCCAGCAGCCTGGGCACACAGACTTACATTTGC AACGTGAACCACAAACCTTCCAACACTAAGGTGGACAAAA AGGTGGAACCCAAATCCTGTGATAAGACCCATACATGCCCA CCTTGTCCCGCTCCTGAGCTGCTGGGGGGACCTTCCGTCTTT CTGTTTCCTCCAAAACCAAAAGACACACTCATGATCAGCCG GACCCCCGAAGTCACCTGTGTGGTGGTGGACGTCAGCCACG AAGATCCAGAGGTCAAGTTCAATTGGTACGTGGATGGAGTG GAAGTCCACAACGCAAAAACCAAACCTAGAGAAGAACAGT ACAATAGCACATACAGGGTGGTGTCCGTCCTGACAGTGCTC CACCAGGACTGGCTCAATGGCAAAGAGTATAAGTGCAAGG TGAGCAACAAGGCCCTGCCTGCACCAATTGAGAAAACAATT AGCAAGGCAAAGGGGCAGCCACGGGAACCCCAGGTGTATA CCCTGCCCCCAAGCCGGGATGAACTGACCAAAAACCAGGTC AGCCTGACATGCCTGGTGAAAGGGTTTTACCCAAGCGATAT TGCCGTCGAGTGGGAGAGCAACGGACAGCCAGAAAACAAT TACAAAACCACCCCACCTGTGCTGGACTCCGATGGGAGCTT TTTCCTGTACAGCAAGCTCACAGTGGACAAGTCCAGATGGC AACAGGGCAACGTGTTTTCCTGCTCCGTGATGCACGAGGCC CTCCACAACCACTATACACAAAAGTCCCTCTCCCTCAGCCC AGGA 77 αFXI- QVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG1 (1Q) TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (C-terminal KGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSG K-less) VHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV TCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVS VLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVY TLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPG 78 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG1 (1Q) AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT xxx = CAG GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA or CAA (Q) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT (C-terminal TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA K-less) CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCTAGCACAAAAGGACCAAGCGTGTTTCCACTGGC ACCTAGCAGCAAATCCACCAGCGGCGGAACAGCAGCCCTC GGGTGCCTGGTGAAGGATTACTTCCCTGAGCCAGTCACAGT GTCCTGGAACTCCGGAGCCCTGACATCCGGCGTGCACACCT TCCCCGCTGTGCTGCAATCCAGCGGACTGTATAGCCTCAGC TCCGTCGTGACAGTCCCTTCCAGCAGCCTGGGCACACAGAC TTACATTTGCAACGTGAACCACAAACCTTCCAACACTAAGG TGGACAAAAAGGTGGAACCCAAATCCTGTGATAAGACCCAT ACATGCCCACCTTGTCCCGCTCCTGAGCTGCTGGGGGGACC TTCCGTCTTTCTGTTTCCTCCAAAACCAAAAGACACACTCAT GATCAGCCGGACCCCCGAAGTCACCTGTGTGGTGGTGGACG TCAGCCACGAAGATCCAGAGGTCAAGTTCAATTGGTACGTG GATGGAGTGGAAGTCCACAACGCAAAAACCAAACCTAGAG AAGAACAGTACAATAGCACATACAGGGTGGTGTCCGTCCTG ACAGTGCTCCACCAGGACTGGCTCAATGGCAAAGAGTATAA GTGCAAGGTGAGCAACAAGGCCCTGCCTGCACCAATTGAGA AAACAATTAGCAAGGCAAAGGGGCAGCCACGGGAACCCCA GGTGTATACCCTGCCCCCAAGCCGGGATGAACTGACCAAAA ACCAGGTCAGCCTGACATGCCTGGTGAAAGGGTTTTACCCA AGCGATATTGCCGTCGAGTGGGAGAGCAACGGACAGCCAG AAAACAATTACAAAACCACCCCACCTGTGCTGGACTCCGAT GGGAGCTTTTTCCTGTACAGCAAGCTCACAGTGGACAAGTC CAGATGGCAACAGGGCAACGTGTTTTCCTGCTCCGTGATGC ACGAGGCCCTCCACAACCACTATACACAAAAGTCCCTCTCC CTCAGCCCAGGA 79 αFXI- EVQLQESGPGLVKPSQTLSLTCTVSGGSIYSGAYYWSWIRQHP 18623p HC GKGLEWIGSIHYSGLTYYNPSLKSRVTISVDTSKNQFSLKLSSV IgG1 (1E) TAADTAVYYCARDVDDSSGDEHYGMDVWGQGTTVTVSSAST (C-terminal KGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSG K-less) VHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDK KVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEV TCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVS VLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVY TLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTP PVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKS LSLSPG 80 DNA xxxGTCCAGCTGCAGGAATCCGGACCCGGCCTGGTGAAGCCT encoding AGCCAGACCCTGAGCCTGACCTGTACCGTGTCCGGCGGAAG αFXI- CATCTATTCCGGCGCCTACTACTGGTCCTGGATTAGGCAGC 18623p HC ACCCCGGCAAGGGCCTGGAATGGATCGGCTCCATCCACTAC IgG1 (1E) AGCGGCCTGACCTATTACAACCCCTCCCTGAAGTCCAGGGT xxx =GAA GACCATCAGCGTCGACACAAGCAAGAACCAGTTCTCCCTCA or GAG (E) AGCTGAGCAGCGTGACCGCCGCCGACACCGCCGTGTATTAT (C-terminal TGCGCCAGAGACGTGGACGACTCCTCCGGAGACGAGCACTA K-less) CGGCATGGACGTCTGGGGCCAGGGCACAACAGTGACAGTG AGCAGCGCTAGCACAAAAGGACCAAGCGTGTTTCCACTGGC ACCTAGCAGCAAATCCACCAGCGGCGGAACAGCAGCCCTC GGGTGCCTGGTGAAGGATTACTTCCCTGAGCCAGTCACAGT GTCCTGGAACTCCGGAGCCCTGACATCCGGCGTGCACACCT TCCCCGCTGTGCTGCAATCCAGCGGACTGTATAGCCTCAGC TCCGTCGTGACAGTCCCTTCCAGCAGCCTGGGCACACAGAC TTACATTTGCAACGTGAACCACAAACCTTCCAACACTAAGG TGGACAAAAAGGTGGAACCCAAATCCTGTGATAAGACCCAT ACATGCCCACCTTGTCCCGCTCCTGAGCTGCTGGGGGGACC TTCCGTCTTTCTGTTTCCTCCAAAACCAAAAGACACACTCAT GATCAGCCGGACCCCCGAAGTCACCTGTGTGGTGGTGGACG TCAGCCACGAAGATCCAGAGGTCAAGTTCAATTGGTACGTG GATGGAGTGGAAGTCCACAACGCAAAAACCAAACCTAGAG AAGAACAGTACAATAGCACATACAGGGTGGTGTCCGTCCTG ACAGTGCTCCACCAGGACTGGCTCAATGGCAAAGAGTATAA GTGCAAGGTGAGCAACAAGGCCCTGCCTGCACCAATTGAGA AAACAATTAGCAAGGCAAAGGGGCAGCCACGGGAACCCCA GGTGTATACCCTGCCCCCAAGCCGGGATGAACTGACCAAAA ACCAGGTCAGCCTGACATGCCTGGTGAAAGGGTTTTACCCA AGCGATATTGCCGTCGAGTGGGAGAGCAACGGACAGCCAG AAAACAATTACAAAACCACCCCACCTGTGCTGGACTCCGAT GGGAGCTTTTTCCTGTACAGCAAGCTCACAGTGGACAAGTC CAGATGGCAACAGGGCAACGTGTTTTCCTGCTCCGTGATGC ACGAGGCCCTCCACAACCACTATACACAAAAGTCCCTCTCC CTCAGCCCAGGA 81 Human FXI ECVTQLLKDTCFEGGDITTVFTPSAKYCQVVCTYHPRCLLFTFT AESPSEDPTRWFTCVLKDSVTETLPRVNRTAAISGYSFKQCSH QISACNKDIYVDLDMKGINYNSSVAKSAQECQERCTDDVHCH FFTYATRQFPSLEHRNICLLKHTQTGTPTRITKLDKVVSGFSLK SCALSNLACIRDIFPNTVFADSNIDSVMAPDAFVCGRICTHHPG CLFFTFFSQEWPKESQRNLCLLKTSESGLPSTRIKKSKALSGFSL QSCRHSIPVFCHSSFYHDTDFLGEELDIVAAKSHEACQKLCTNA VRCQFFTYTPAQASCNEGKGKCYLKLSSNGSPTKILHGRGGIS GYTLRLCKMDNECTTKIKPRIVGGTASVRGEWPWQVTLHTTS PTQRHLCGGSIIGNQWILTAAHCFYGVESPKILRVYSGILNQSEI KEDTSFFGVQEIIIHDQYKMAESGYDIALLKLETTVNYTDSQRP ICLPSKGDRNVIYTDCWVTGWGYRKLRDKIQNTLQKAKIPLVT NEECQKRYRGHKITHKMICAGYREGGKDACKGDSGGPLSCKH NEVWHLVGITSWGEGCAQRERPGVYTNVVEYVDWILEKTQA V 82 Epitope A DIFPNTVF 83 Epitope B PSTRIKKSKALSG 84 anti-RSV MAPVQLLGLLVLFLPAMRCDIQMTQSPSTLSASVGDRVTITCKCQLS Kappa Light VGYMHWYQQKPGKAPKLLIYDTSKLASGVPSRFSGSGSGTEFTLTIS Chain SLQPDDFATYYCFQGSGYPFTFGGGTKLEIKRTVAAPSVFIFPPSDEQL KSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSL SSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC 85 anti-RSV MAVVQLLGLLVLFLPAMRCQVTLRESGPALVKPTQTLTLTCTFSGFS IgG4 HC LSTSGMSVGWIRQPPGKALEWLADIWWDDKKDYNPSLKSRLTISKD S228P TSKNQVVLKVTNMDPADTATYYCARSMITNWYFDVWGAGTTVTV SSASTKGPSVFPLAPCSRSTSESTAALGCLVKDYFPEPVTVSWNSGALTSG VHTFPAVLQSSGLYSLSSVVTVPSSSLGTKTYTCNVDHKPSNTKVDKRVES KYGPPCPPCPAPEFLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSQED PEVQFNWYVDGVEVHNAKTKPREEQFNSTYRVVSVLTVLHQDWLNGKE YKCKVSNKGLPSSIEKTISKAKGQPREPQVYTLPPSQEEMTKNQVSLTCLV KGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFLYSRLTVDKSRWQE GNVFSCSVMHEALHNHYTQKSLSLSLGK Constant regions are shown in italics. Amino acid sequences underlined are CDRs.

(174) While the present invention is described herein with reference to illustrated embodiments, it should be understood that the invention is not limited hereto. Those having ordinary skill in the art and access to the teachings herein will recognize additional modifications and embodiments within the scope thereof. Therefore, the present invention is limited only by the claims attached herein.