AMYLOID INHIBITORY PEPTIDES

Abstract

The present invention relates to peptides, in particular amyloid inhibitory peptides, and to pharmaceutical compositions comprising such peptides. Furthermore, the present invention relates to such peptides, in particular such amyloid inhibitory peptides, for use in methods of treating or diagnosing neurodegenerative diseases such as Alzheimer's disease, or for use in a method of treating or diagnosing type 2 diabetes. Furthermore, the present invention also relates to a kit for the in-vitro or in-vivo detection and, optionally, quantification of amyloidogenic polypeptides, amyloid fibrils or amyloid aggregates, and/or for the diagnosis of Alzheimer's disease or type 2 diabetes in a patient.

Claims

1. A method for treating Alzheimer's disease or type 2 diabetes, wherein said method comprises administering, to a patient in need of such treatment, a peptide having an amino acid sequence according to formula 0 ##STR00011## wherein Z1 and Z2 are selected from the following pairs a) cysteine and cysteine, b) aspartic acid and lysine, or lysine and aspartic acid, c) aspartic acid and ornithine, or ornithine and aspartic acid, d) aspartic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and aspartic acid, e) aspartic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and aspartic acid, f) glutamic acid and lysine, or lysine and glutamic acid, g) glutamic acid and ornithine, or ornithine and glutamic acid, h) glutamic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and glutamic acid, i) glutamic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and glutamic acid; with denoting a covalent bond between Z1 and Z2, thus providing for a cyclization of the peptide; X1, X2, X3, X4, X5, X6, and X7 are, independently at each occurrence, selected from glycine, asparagine, valine, histidine, leucine, serine, alanine, and threonine; F is, independently at each occurrence, phenylalanine; L is leucine; U is, independently at each occurrence, selected from arginine, homoarginine, citrulline, ornithine, lysine, and norleucine; G is glycine; I is isoleucine; wherein Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues or D-amino acid residues, or some of Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues and others are D-amino acid residues; and pharmaceutically acceptable salts, esters, solvates, polymorphs and modified forms thereof.

2. The method according to claim 1, wherein the peptide has an amino acid sequence according to formula 1 ##STR00012## or an amino acid sequence according to formula 1* ##STR00013## wherein C is cysteine; X1, X2, X3, X4, X5, X6, and X7 are, independently at each occurrence, selected from glycine, asparagine, valine, histidine, leucine, serine, alanine, and threonine; F is, independently at each occurrence, phenylalanine; L is leucine; R is arginine; G is glycine; I is isoleucine; is a disulfide bond; ##STR00014##  is N-methyl; wherein C, X1-X7, F, L, R, G and I are L-amino acid residues or D-amino acid residues, or some of C, X1-X7, F, L, R, G and I are L-amino acid residues and others are D-amino acid residues; and pharmaceutically acceptable salts, esters, solvates, polymorphs and modified forms thereof.

3. The method according to claim 1, wherein either f) X1 and X4 are asparagine, X2 is valine, X3 is histidine, X4 is glycine, X5 is glycine, X6 and X7 are glycine; g) X1-X7 are glycine, alanine or serine; h) X1-X7 are glycine; i) X1-X3 are glycine, X4 is asparagine, X5 is alanine, X6-X7 are glycine; or j) X1-X3 are glycine, X4 is asparagine, X5 is alanine, X6 is leucine, X7 is serine.

4. The method according to claim 1, wherein Z1, Z2, C, X1-X7, F, L, U, R, G, and I are L-amino acid residues.

5. The method according to claim 1, wherein R is, at each occurrence, D-arginine, and/or wherein F is, at each occurrence, D-phenylalanine, and/or wherein L is D-leucine, and/or wherein Z1, Z2 and C are D-amino acid residues, and/or wherein I is D-isoleucine or N-methyl-D-isoleucine.

6. The method according to claim 1, wherein the peptide has a sequence according to a formula selected from the following formulae 2a-2e, and 2a*-2e*: ##STR00015## wherein upper case letters represent L-amino acid residues or D-amino acid residues, and lower case letters represent D-amino acid residues.

7. The method according to claim 6, wherein the upper case letters represent L-amino acid residues.

8. The method according to claim 6, wherein the peptide has a sequence according to a formula selected from 2e and 2e* ##STR00016##

9. The method according to claim 1, wherein the peptide consists of a sequence according to any of formulae 0, 0a, 1, 1*, 2a-2e, and 2a*-2e*: ##STR00017## wherein upper case letters represent L-amino acid residues or D-amino acid residues, and lower case letters represent D-amino acid residues.

10. The method according to claim 6, wherein the upper case letters represent L-amino acid residues.

11. The method, according to claim 1, wherein the peptide has an amino acid sequence according to formula 0a ##STR00018## wherein Z1, Z2, X1-X7, F, L, U, G, I are as defined in claim 1, and ##STR00019##  is N-methyl.

12. The method according to claim 1, wherein the peptide is an amyloid inhibitory peptide that binds to Aß340(42) and/or to islet amyloid polypeptide (IAPP), or wherein the peptide is a peptide that binds to Aß40(42) and/or to islet amyloid polypeptide (IAPP), but is not an amyloid inhibitory peptide.

13. A method for diagnosing Alzheimer's disease or type 2 diabetes wherein said method comprises administering to a subject to be tested for Alzheimer's disease or type 2 diabetes, a peptide having an amino acid sequence according to formula 0 ##STR00020## wherein Z1 and Z2 are selected from the following pairs a) cysteine and cysteine, b) aspartic acid and lysine, or lysine and aspartic acid, c) aspartic acid and ornithine, or ornithine and aspartic acid, d) aspartic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and aspartic acid, e) aspartic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and aspartic acid, f) glutamic acid and lysine, or lysine and glutamic acid, g) glutamic acid and ornithine, or ornithine and glutamic acid, h) glutamic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and glutamic acid, i) glutamic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and glutamic acid; with denoting a covalent bond between Z1 and Z2, thus providing for a cyclization of the peptide; X1, X2, X3, X4, X5, X6, and X7 are, independently at each occurrence, selected from glycine, asparagine, valine, histidine, leucine, serine, alanine, and threonine; F is, independently at each occurrence, phenylalanine; L is leucine; U is, independently at each occurrence, selected from arginine, homoarginine, citrulline, ornithine, lysine, and norleucine; G is glycine; I is isoleucine; wherein Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues or D-amino acid residues, or some of Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues and others are D-amino acid residues; and pharmaceutically acceptable salts, esters, solvates, polymorphs and modified forms thereof.

14. The method according to claim 13, wherein the peptide is linked to or administered together with a suitable reporter molecule that allows detection of Aß40(42), islet amyloid polypeptide (IAPP) and/or amyloid aggregates thereof by a suitable detection methodology and wherein said subject, after administration of said peptide, is subjected to said suitable detection methodology.

15. The method, according to claim 14, wherein the suitable detection methodology is selected from positron emission tomography (PET), nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), and PET-MRI.

16. The method according to claim 13, wherein the peptide has an amino acid sequence according to formula 1 ##STR00021## or an amino acid sequence according to formula 1* ##STR00022## wherein C is cysteine; X1, X2, X3, X4, X5, X6, and X7 are, independently at each occurrence, selected from glycine, asparagine, valine, histidine, leucine, serine, alanine, and threonine; F is, independently at each occurrence, phenylalanine; L is leucine; R is arginine; G is glycine; I is isoleucine; is a disulfide bond; ##STR00023##  is N-methyl; wherein C, X1-X7, F, L, R, G and I are L-amino acid residues or D-amino acid residues, or some of C, X1-X7, F, L, R, G and I are L-amino acid residues and others are D-amino acid residues; and pharmaceutically acceptable salts, esters, solvates, polymorphs and modified forms thereof.

17. The method according to claim 13, wherein the peptide has a sequence according to a formula selected from the following formulae 2a-2e, and 2a*-2e*: ##STR00024## wherein upper case letters represent L-amino acid residues or D-amino acid residues, and lower case letters represent D-amino acid residues.

18. The method according to claim 17, wherein the peptide has a sequence according to a formula selected from 2e and 2e* ##STR00025##

19. The method according to claim 13, wherein the peptide consists of a sequence according to any of formulae 0, 0a, 1, 1*, 2a-2e, and 2a*-2e*: ##STR00026## wherein upper case letters represent L-amino acid residues or D-amino acid residues, and lower case letters represent D-amino acid residues.

20. A method for the detection of monomeric islet amyloid polypeptide (IAPP), monomeric Aß40(42), amyloid fibrils, or amyloid aggregates wherein said method comprises the use of a peptide having an amino acid sequence according to formula 0 ##STR00027## wherein Z1 and Z2 are selected from the following pairs a) cysteine and cysteine, b) aspartic acid and lysine, or lysine and aspartic acid, c) aspartic acid and ornithine, or ornithine and aspartic acid, d) aspartic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and aspartic acid, e) aspartic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and aspartic acid, f) glutamic acid and lysine, or lysine and glutamic acid, g) glutamic acid and ornithine, or ornithine and glutamic acid, h) glutamic acid and 2,4-diaminobutyric acid, or 2,4-diaminobutyric acid and glutamic acid, i) glutamic acid and 2,3-diaminopropionic acid, or 2,3-diaminopropionic acid and glutamic acid; with denoting a covalent bond between Z1 and Z2, thus providing for a cyclization of the peptide; X1, X2, X3, X4, X5, X6, and X7 are, independently at each occurrence, selected from glycine, asparagine, valine, histidine, leucine, serine, alanine, and threonine; F is, independently at each occurrence, phenylalanine; L is leucine; U is, independently at each occurrence, selected from arginine, homoarginine, citrulline, ornithine, lysine, and norleucine; G is glycine; I is isoleucine; wherein Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues or D-amino acid residues, or some of Z1, Z2, X1-X7, F, L, U, G and I are L-amino acid residues and others are D-amino acid residues; and pharmaceutically acceptable salts, esters, solvates, polymorphs and modified forms thereof.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0094] Furthermore, reference is made to the figures, wherein

[0095] FIG. 1 shows an embodiment of the inhibitor design strategy employed by the present inventors. a) shows the sequences of Aβ40(42) and IAPP. b) shows a partial sequence from IAPP, R3-GI (1) (a peptide based on residues 8-28 of IAPP) and designed peptides with lower-case-letters denoting D-amino acid residues. There are amide bond N-methylations at G12 and 114.

[0096] FIG. 2 shows the effects of effects of peptides 1-2a on amyloid self-assembly of Aβ40 and IAPP and CD studies on their conformations. a) Fibrillogenesis of Aβ40 (16.5 μM) or its mixtures (Aβ40/peptide, 1/1 or 1/2 (2)) by ThT binding (means (±SD), 3 assays). b) Effects on cell viability: Solutions from 1a (7 day-aged) added to PC12 cells; cell damage determined by MTT reduction (means (±S.D.), 3 assays (n=3 each)). c) Fibrillogenesis of LAPP (6 μM) and its mixtures (IAPP/peptide, 1/2 (1a, 2a) or 1/10 (i, 2) by ThT binding (means (±S.D.), 3 assays). d) Cell-damaging effects of IAPP or its mixtures (from 1c; 7 day-aged) on RIN5fm cells via MTT reduction (means (±S.D.), 3 assays (n=3 each)). e) TEM images of Aβ40, IAPP and their mixtures with 1a and 2a (7 days aged) (bars 100 nm). f) CD spectra (5 μM, pH 7.4).

[0097] FIG. 3 shows effects of peptides 2b and 2e versus 2a on fibrillogenesis and cytotoxicity of Aβ40 and IAPP and CD studies on inhibitor conformations. a) Fibrillogenesis of Aβ40 (16.5 μM) or its mixtures with 2a (1/1) and 2b or 2e (1/5) by ThT binding (means (±S.D.), 3 assays). b) PC12 cell viability following treatment with 7 day-aged solutions (from 2a) by MTT reduction (means (±S.D.), 3 assays (n=3 each)). c) Fibrillogenesis of IAPP (6 μM) or its mixtures with 2a (1/2) and 2b or 2e (1/10) determined by ThT binding (means (±S.D.), 3 assays). d) RIN5fm cell viability following treatment with 7 day-aged solutions (from 2c) by MTT reduction (means (±SD), 3 assays (n=3 each)). e) TEM images of Aβ40 or IAPP and their mixtures with 2b and 2e (7 day-aged) (bars 100 nm). f) CD spectra (5 μM, pH 7.4).

[0098] FIG. 4 shows proteolytic stabilities of inhibitors in human blood plasma in vitro (a), effects on Aβ42 amyloid self-assembly (b,c) and on Aβ42-induced impairment of synaptic LTP ex vivo (d,e), and permeability across a human BBB model in vitro (f,g). a) Peptides were incubated in plasma and quantified by HPLC and MALDI-TOF-MS; remaining intact peptide (% of total) is plotted over incubation time. b) Fibrillogenesis of Aβ42 (16.5 μM) or its mixtures with peptides (1a & 2a, 1/1; 2b & 2e, 1/5) by ThT binding (means (±SD), 3 assays). c) PC12 cell viability after treatment with 7 day-aged solutions from 3b by MITT reduction (means (±SD), 3 assays (n=3)). d,e) Amelioration of Aβ42-induced (50 nM) LTP impairment in murine acute hippocampal slices by 2b (d) or 2e (e) (500 nM). Time course of synaptic transmission (means (±SEM), n=7 (Aβ42/inhibitor mixtures), n=4 (Aβ42) and n=9-11 (control). Inset: LTP in presence of Aβ42, Aβ42/inhibitor mixture, or inhibitor alone (control) as above; bars show average from the last 5 min of recordings (means (±SEM), n=7-14); * indicates significant effects for the mixtures or controls versus Aβ42 (p<0.05, n=7-11 (unpaired t-test). f) Relative permeability of 2e (Fluos-2e; 10 μM) across the BBB cell model; plot shows Fluos-2e amount in acceptor chamber at various time points (means (±SEM), n=3-4). g) RP-HPLC chromatogram of solution in acceptor chamber at 2 h (from 30 (left) and MALDI-TOF spectrum (right) of peptide eluted at ˜18 min (*, Fluos-2e, calculated [M+H].sup.+=2053.20, found 2053.38); additional peaks are from assay medium.

[0099] Moreover, reference is made to the following examples which are given to illustrate and not to limit the present invention.

EXAMPLES

Example 1—Materials and Methods

[0100] Peptides and Peptide Synthesis

[0101] Aβ40 (TFA salt) was synthesized by Fmoc-based solid phase synthesis (SPPS) on Tentagel R PHB resin (Rapp Polymere) using previously published protocols, purified by RP-HPLC and treated as described. Aβ40 stocks were freshly prepared in 1,1,3,3,3,3-hexafluoro-2-isopropanol (HFIP) (4° C.); their concentrations were determined by the bicinchoninic acid (BCA) assay (Pierce). IAPP was synthesized by SPPS and the Fmoc-strategy on RINK resin, subjected to air oxidation and purified by RP-HPLC. Freshly made IAPP stocks in HFIP (200-500 μM) were filtered over 0.2 μm filters (Millipore) (4° C.); concentrations were determined by UV spectroscopy. Na-terminal fluorescein-labeled IAPP (Fluos-IAPP) and N-terminal 7-diethylaminocoumarin-3-carbonyl-labeled Aβ40 (Dac-Aβ40) for fluorescence spectroscopic titrations were synthesized by Fmoc-based SPPS, purified and handled. Synthetic Aβ42 (TFA salt) was from PSL (Heidelberg) and its HFIP stocks were made. Synthetic N-terminal FITC-β-Ala-labeled Aβ42 (FITC-Aβ42) (FITC, fluorescein isothiocyanate) for fluorescence titrations was from Bachem; its HFIP stock solutions were always freshly made (4° C.) and their concentrations determined by UV spectroscopy. ISMs, MCIPs, control peptides (analogs of 2a and 2b), THRPPMWSPVWP-amide (Trfb) and their N-terminal fluorescein-labeled analogs (C-terminal amides) were synthesized by Fmoc-based SPPS on Rink-resin and cleaved from the resin using previously published protocols. Disulphide bridge formation of MCIPs and control peptides was performed by dissolving crude peptide (after cleavage and lyophilization) at 1 mg/ml in aqueous 0.1 M NH.sub.4HCO.sub.3 solution containing 40% DMSO; the progress of the oxidation reaction was followed by RP-HPLC. Peptides were purified by RP-HPLC using previously described protocols and characterized by MALDI-TOF mass spectrometry (MS) Stock solutions of all peptides were freshly made in HFIP (4° C.) and concentrations were determined by peptide weight and by UV spectroscopy in the case of fluorescently labeled peptides.

[0102] Thioflavin T (ThT) Binding Assays

[0103] To study the effects of peptides on Aβ40(42) and IAPP fibrillogenesis previously established ThT binding assay systems were used. Briefly, Aβ40 (16.5 μM) or IAPP (6 μM) and their mixtures with peptides were incubated for up to 7 days in ThT assay buffer at room temperature. The ThT assay buffer consisted of aqueous 50 mM sodium phosphate buffer, pH 7.4, containing 100 mM NaCl and 1% HFIP (Aβ40(42) related studies) or 0.5% HFIP (IAPP related studies). Each experimental set contained incubations of Aβ40(42) or IAPP alone as controls. At indicated time points, aliquots were gently mixed with a ThT solution (20 μM ThT in 0.05 M glycine/NaOH, pH 8.5); ThT binding was determined immediately by measuring fluorescence emission at 486 nm upon excitation at 450 nm using a 2030 Multilabel Reader VictorX3 (PerkinElmer Life Sciences). Effects of peptides added at specific pre- and post-nucleation time points of Aβ40 amyloidogenesis were studied by adding aliquots of Aβ40 solutions (16.5 μM; incubation conditions as above) aged for the indicated time points to the peptide (in dry form) as previously described and ThT binding was determined as above. To determine the effects of peptides on already nucleated IAPP fibrillogenesis, aliquots of IAPP (16.5 μM; incubation conditions as above), which was aged for the indicated time points and contained significant amounts of IAPP fibrils (as confirmed by ThT binding and TEM (data not shown)) was added to the peptide (in dry form) as described and ThT binding was determined as above.

[0104] Transmission Electron Microscopy (TEM)

[0105] 10 μl aliquots of solutions of the ThT binding and MTI assays were applied on carbon-coated grids at indicated time points, washed with distilled water and stained with aqueous 2% (w/v) uranyl acetate as described. Grids were examined using a JEOL JEM 100CX (at 100 kV) or a JEOL 1400 Plus electron microscope (at 120 kV).

[0106] Assessment of Cell Damage by MTT Reduction Assay

[0107] Effects of peptides on the formation of cell-damaging IAPP or Aβ40(42) assemblies were studied using the solutions applied for the ThT binding assays as previously described. Briefly, for effects on the formation of cell-damaging Aβ40(42) aggregates, the inventors used cultured PC-12 cells while for effects on IAPP-mediated cell damage cultured RIN5fm cells were used. Both cell lines were cultured and plated in 96-well plates as described. Solutions consisting of Aβ40(42) or IAPP alone (16.5 and 6 μM, respectively) versus their mixtures with the potential inhibitors were made as described under “ThT binding assays” and incubated for 7 or 8 days at room temperature. At the incubation time points of 24 h or 72 h and 7 (or 8) days (identical results were obtained from solutions aged for 7 or 8 days), aliquots were diluted with cell culture medium and added to the cells at the indicated final concentrations. Following incubation with the cells for ˜20 h (37° C., humidified atmosphere with 5% CO.sub.2), the MTI reduction assay was used to assess cell damage/metabolic activity as previously described. To determine IC.sub.50 values, Aβ40 (500 nM) or IAPP (100 nM) were titrated with different amounts of peptides under the conditions of the ThT binding assays and cell-damaging effects were determined using 24 h-aged solutions (IAPP-related effects) or 72 h-aged solutions (Aβ40-related effects) by the MTT assay as described. Of note, studies with selected MCIPs (incubated under the same conditions as in their mixtures with Aβ40(42) or IAPP) showed that they were, as expected, non-amyloidogenic and not cytotoxic (data not shown). These results were in line with the fact that the sequences of the MCIPs were derived from the non-amyloidogenic and non-cytotoxic ISM R3-GI and with results of previous studies showing the lack of amyloidogenicity and cell-damaging effects of related N-methylated IAPP analogs or segments.

[0108] To determine the effects of peptides on preformed cell damaging assemblies of Aβ40 or IAPP, aliquots of Aβ40 or IAPP solutions (16.5 μM; incubation conditions as above), aged for the indicated time points and containing significant amounts of cell damaging assemblies (as shown by the MTT reduction assay in this and previous studies (data not shown)) were added to the peptide (in dry form) as described and following incubation for the indicated time points solutions were added to PC12 or RIN5fm cells. Following incubation with the cells for ˜20 h, the MTT reduction assay was performed as described. Of note, our assay system allows following in parallel formation of both fibrils (by the ThT binding assay) and cell damaging assemblies of Aβ40(42) and IAPP starting from non-fibrillar and non-toxic states as previously described.

[0109] Far-UV CD Spectroscopy

[0110] Far-UV CD measurements were performed with a Jasco 715 spectropolarimeter as described. Spectra were measured immediately following solution preparation between 195 and 250 nm, at 0.1 nm intervals, a response time of 1 sec, each spectrum being the average of 3 spectra and at room temperature. CD measurements were performed using freshly made 5 μM solutions of ISMs in aqueous 10 mM sodium phosphate buffer, pH 7.4, containing 1% HFIP (CD assay buffer); peptides were diluted from freshly made stock solutions in HFIP into the aqueous assay buffer. Of note, the magnitudes of the CD spectra of all peptides/inhibitors depend on their concentrations due to the inherently strong self-association potential of peptides derived from the human IAPP sequence (data not shown). The spectrum of the buffer was subtracted from the CD spectra of the peptide solutions prior conversion of the raw data to mean residue ellipticities.

[0111] Fluorescence Spectroscopic Titration Studies

[0112] A JASCO FP-6500 fluorescence spectrophotometer was used for the fluorescence spectroscopic titrations, which were performed by using previously described experimental protocols. Briefly, for titrations of Fluos-IAPP and FITC-labeled Aß42, excitation was at 492 nm and fluorescence emission spectra were recorded between 500 and 600 nm, while for titrations of Dac-Aβ40, excitation was at 430 nm and emission spectra were collected between 440 and 550 nm. App. K.sub.ds of interactions of IAPP, Aβ40 and Aβ42 with the peptides were determined by titrating freshly made solutions of Fluos-IAPP (5 nM), Dac-Aβ40 (10 nM) and FITC-Aβ42 (5 nM) with peptides as described. Of note, this assay system has been previously used for the determination of the affinities (app. K.sub.d) of interactions of a number of inhibitors of IAPP and Aβ40(42) amyloid self-assembly with these highly amyloidogenic polypeptides and the affinity of the Aβ40(42)-IAPP interactions as well. Briefly, freshly made stock solutions of peptides and fluorescently labeled analogs in HFIP were used. Measurements were performed in 10 mM sodium phosphate buffer, pH 7.4 (1% HFIP) at room temperature within 2-5 min following solution preparation. Under these experimental conditions, freshly made solutions of Fluos-IAPP, Dac-A40 and FITC-Aβ42 at the herein-applied low nanomolar concentrations contain mostly monomers. App. K.sub.ds were estimated using 1/1 binding models as previously described. Of note, due to the inherently high self-assembly potentials of IAPP-derived peptides more complex binding models may also apply. Determined app. K.sub.ds are means (±SD) from three binding curves.

[0113] Cross-Linking, NuPAGE and Western Blot Analysis

[0114] Cross-linking studies were performed using a previously established assay system used for the characterization of hetero-assemblies of Aβ40 and IAPP with IAPP and IAPP-derived inhibitors including ISMs as described..sup.[1, 4] Briefly, Aβ40 or IAPP were incubated alone (30 μM) or in the presence of peptides (IAPP/peptide and Aβ40/peptide 1/10) in aqueous 10 mM sodium phosphate buffer, pH 7.4, at room temperature for 3 h (Aβ40 related studies) or 30 min (IAPP related studies). Thereafter, samples were cross-linked with aqueous glutaraldehyde (25%) (Sigma-Aldrich) and cross-linked hetero-complexes were precipitated with aqueous trichloroacetic acid (TCA) (10%); pellets were dissolved in NuPAGE sample buffer (w/o reducing agent), boiled (5 min) and NuPAGE electrophoresis in 4-12% Bis-Tris gels with MES running buffer was performed according to the manufacturer's (Invitrogen) recommendations. Equal amounts of Aβ40 or IAPP were loaded in all lanes. For peptide blotting onto nitrocellulose, a XCell II Blot Module blotting system (Invitrogen) was used. Aβ40 and Aβ40-containing complexes were revealed by Western blotting and a polyclonal rabbit anti-Aβ40 antibody (Sigma-Aldrich) while IAPP and IAPP-containing complexes by a polyclonal rabbit anti-IAPP antibody (Bachem) in combination with peroxidase (POD)-coupled secondary antibody (Amersham) and the Super Signal Duration ECL staining solution (Pierce).

[0115] Peptide Stability in Human Plasma (In Vitro)

[0116] Peptides were dissolved in human blood plasma (obtained from voluntary healthy donors) at a concentration of 200 μM and incubated at 37° C. for various time intervals. Following quenching (1/1) with aqueous trichloroacetic acid (10%), solutions were incubated on ice for 10 min, subjected to centrifugation to precipitate plasma proteins (20200 g; 4 min), and the supernatants were mixed (1/2) with a solution consisting of 80% HPLC buffer B and 20% HPLC buffer A (see below). To quantify intact peptide at different time points, solutions containing the supernatants were analyzed by RP-HPLC (detection at 214 nm) by using a Nucleosil 100 C18 column (Grace) (length 33 mm length, ID 8 mm, 7 μm particle size) with a flow rate of 2.0 ml/min and eluting buffers A, 0.058% (v/v) TFA in water, and B, 0.05% (v/v) TFA in 90% (v/v) CH.sub.3CN in water. The elution gradient was 10-90% B in A over 8 min; this step was followed by a 90-10% B in A over 3 min step to establish starting conditions. HPLC fractions were collected, lyophilized, and analyzed by MALDI-TOF-MS using a Bruker Daltonik MALDI-TOF MS instrument.

[0117] Peptide Stability Toward Degradation by Human Neprilysin (In Vitro)

[0118] Stabilities of 2e and 2b toward degradation by neprilysin was studied based on a previously published protocol: Briefly, peptides were incubated (100 PM) with recombinant human neprilysin (NEP) (500 ng/ml) (Sigma-Aldrich) in 10 mM Tris buffer, pH 6.5 and at 37° C. At indicated time points aliquots were quenched (1/1) with aqueous trichloroacetic acid (10%) and solutions were subjected to HPLC analysis and HPLC fractions were collected and analyzed by MALDI-TOF-MS as described under “Peptide stability in human plasma” (above).

[0119] Determination of Surface Neprilysin/CD10 Levels by Flow Cytometry

[0120] Both the human cerebral microvascular endothelial cell line hCMEC/D3 and human umbilical vein endothelial cells (HUVEC) were cultured on collagen type I-coated plates (BD Biosciences) in EndoGRO™-MV Complete Media Kit (Merck) supplemented with 1 ng/mL fibroblast growth factor-basic (bFGF) (Merck) and maintained at 37° C. in a humidified atmosphere of 5% CO.sub.2. Cell culture medium was routinely replaced every 2-3 days. The cell surface expression of human CD10, also termed CALLA or neprilysin, on hCMECs and HUVECs was monitored by flow cytometry. Briefly, 1×10.sup.6 cells were washed three times with ice-cold phosphate-buffered saline (PBS) supplemented with 0.5% bovine serum albumin (BSA) and subsequently stained with phycoerytherin (PE)-conjugated anti-CD10 antibody (eBioscience) or the corresponding isotype control IgG for 1 h at 4° C. After incubation, the cells were washed and analyzed by a BD FACSVerse™ flow cytometer (BD Biosciences). The quantification of the measurements was performed using FlowJo software.

[0121] Hippocampal Long-Term Potentiation (LTP) Measurements (Ex Vivo)

[0122] LTP measurements were performed as follows: Briefly, sagittal hippocampal slices (thickness: 350 μm) were obtained from adult (2 months) C57/BL6 male mice. Protocols were approved by the ethical committee on animal care and use of the government of Bavaria, Germany. Mice were anaesthetized by inhalation of isoflurane before decapitation and brains were rapidly removed. Hippocampal slices were prepared in ice-cold Ringer solution, placed in a holding chamber for at least 90 min—the first 30 min at 35° C., the following 60 min cooled down to room temperature—and then transferred to an immersion superfusing chamber for extracellular recordings. The flow rate of the solution through the chamber was 5-8 ml/min. The composition of the Ringer solution was 124 mM NaCl, 3 mM KCl, 26 mM NaHCO.sub.3, 2 mM CaCl.sub.2, 1 mM MgSO.sub.4, 25 mM D-glucose, and 1.24 mM NaH.sub.2PO.sub.4; solution was bubbled with a mixture of 95% O.sub.2 and 5% CO.sub.2, and its pH was 7.3±0.1. Extracellular recordings were made by glass microelectrodes (2-3 Mμ) filled with artificial cerebrospinal fluid (ACSF) and all measurements were performed at room temperature. Synthetic Aβ42 was freshly dissolved in ACSF and added to the bath solution (50 nM).

[0123] Field excitatory postsynaptic potentials (fEPSPs) were evoked by stimulating the Schaffer collateral commissural pathway (Sccp) in the dendritic region of hippocampal CA1 as described. For LTP induction, high-frequency stimulation (HFS; 100 Hz/100 pulses) conditioning pulses were delivered to the same Sccp inputs. For most recordings, both stimulating electrodes were used to utilize the input specificity of LTP and allowing the measurement of an internal control within the same slice. Aβ42 alone (50 nM) was applied for 90 min before high-frequency stimulation (HFS), providing time for its oligomerisation. Mixtures of Aβ42 (50 nM) with each of the tested peptides 2a, 2b and 2e (500 nM) were also applied for 90 min before HFS. Peptides alone (500 nM) were applied to the slices 1 h before HFS. Responses were measured for 60 min after HFS. Recordings were processed and data re-analysed as described. fEPSP slopes measurements were taken between 20 and 80% of the peak amplitude and EPSP slopes are presented as % EPSP slope of baseline (20 min control period before tetanic stimulation (100%)). Data were analysed by paired t-test.

[0124] Human BBB Transwell Permeability Assay (In Vitro)

[0125] Human cerebral microvascular endothelial (hCMEC/D3) cells (Merck) were cultured in collagen type I-coated dishes in EndoGro-MV complete culture media kit supplemented with 1 ng/mL fibroblast growth factor-2 (FGF-2) (all reagents from Merck) (at 37° C. and 5% CO.sub.2). Of note, confluent hCMEC monolayers in Transwell filters represent a suitable model of the human blood-brain-barrier (BBB) with reasonable transendothelial electrical resistance (TEER) values of 30-100 Ωcm.sup.2. Briefly, this cell model has been extensively characterized and found to maintain a brain endothelial phenotype; despite lower complexity due to lack of co-cultured astrocytes/pericytes or application of flow-based shear stress, hCMEC monolayers have suitable barrier characteristics with high junctional integrity, restricted permeability to paracellular tracers, and reasonable transendothelial electrical resistance (TEER) values of 30-100 Ωcm.sup.2. The Transwell permeability assay was then performed based on a previously established assay using 24-well plates (Sigma-Aldrich) containing 6.5 mm Transwell inserts (0.4 μm pore polycarbonate membrane (Corning)) as follows:

[0126] hCMEC/D3 cells were grown in endothelial cell medium (ECM), containing EndoGro-MV complete media, 10% fetal bovine serum (FBS), 1% penicillin-streptamycine (P/S), and 1 ng/mL FGF-2 on the membranes of the Transwell inserts (2×10.sup.5 cells/insert) (37° C. and 5% CO.sub.2) until full confluency was reached (normally after 5-7 days of culture). Confluency and BBB-type tightness was verified by TEER analysis; TEER values of 60-80 Ωcm.sup.2 were obtained. The upper and lower chambers then were reconstituted with 200 μl and 800 μl, respectively, of ECM containing 2% FBS. The N-terminal fluorescein-labeled 12 amino acid-long peptide THRPPMWSPVWP-amide (Fluos-Trfb) known to readily cross the BBB via binding to the transferrin receptor, was used as a positive control for BBB permeability in this model. Synthetic N-terminal fluorescein-labeled 2e (Fluos-2e) (10 μM), Fluos-Trfb (10 μM), or Lucifer yellow (20 μM) (control for BBB tightness) were added to the upper (donor) chamber of the Transwell device (n=3 for each incubation time point and reagent) and incubated (37° C., 5% CO.sub.2) with the cells for the indicated time points.

[0127] For quantification of fluorescently labeled peptides present in the lower (acceptor) chamber, 100 μl of medium was transferred from the lower chamber to a well of a 96-well black polystyrene plate (Greiner) and fluorescence at 519 nm (excitation at 495 nm) was measured with a fluorescence microplate reader (Perkin Elmer Enspire). As a reference point for the maximum fluorescence intensity, 100 μl of medium from the upper chamber at 0 h was also transferred and quantified. Of note, fluorescence of Fluos-2e or Fluos-Trfb was directly proportional to their concentrations as determined by calibration curves. Lucifer yellow in the lower chamber was quantified by measuring the fluorescence at 530 nm (excitation at 485 nm). Relative permeability (FIG. 31) was calculated by dividing the fluorescence value of the aliquot from the lower chamber at each time point by the fluorescence value of the 0 h-lower chamber aliquot.

[0128] Apparent permeability (P.sub.app) at 2 h was calculated by the following equation:

P.sub.app(cm/s)=(dQ/dt)(1/A)(1/C.sub.0)(cm/s)

[0129] where (dQ/dt) is the amount of peptides or Lucifer yellow present in the lower chamber at the 2 hour time point (nmol/s), A is the membrane area of the upper chamber (0.33 cm.sup.2) and C.sub.0 is their initial concentration in the upper chamber (nmol/ml). Reported P.sub.app values are means (±SEM) from at least 3 transport assays (each of them performed in triplicates).

[0130] Of note, studies on the transport rate of Lucifer yellow (P.sub.app=5.3×10.sup.−6 (±2.7) cm/s at 2 h) were performed in parallel to the studies on the peptide transport and were consistent with a good tightness or integrity of the hCMEC monolayer, confirming the TEER measurements. In addition, a P.sub.app of 20.8×10.sup.−6 (±1.9) cm/s was found (at 2 h) for Fluos-Trfb, which further confirmed the validity of the results of the permeability assay.

[0131] Finally, to confirm the above results and the intact nature of the Fluos-2e molecule after crossing the hCMEC BBB-type cell layer, aliquots of upper and lower chambers were analysed by RP-HPLC and MALDI-TOF-MS (FIG. 4g). RP-HPLC (detection at λ=214 nm) was performed using a YMC basic column (length 250 mm; ID 4.6 mm; 5 μm particle size), flow rate 1.0 ml/min and eluting buffers A, 0.058% (v/v) TFA in water, and B, 0.05% (v/v) TFA in 90% (v/v) CH.sub.3CN in water. The elution gradient was 10-90% B in A over 30 min.

Example 2—Design of Peptides and Experiments

[0132] Macrocyclic Inhibitory peptides (“MCIPs”) were designed using R3-GI (1), a partial sequence peptide of IAPP (residues 8-28 of IAPP), containing an RRR tripeptide instead of the three residues 19-21 of the IAPP sequence (see also FIG. 1), as a template, conformational restriction by cyclization, sequence truncation, specific N-methylations, and multiple amino acid substitutions with Gly or D-residues (FIG. 1). Notably, 1 of FIG. 1 is able to inhibit A40(42) but not IAPP amyloidogenesis.

[0133] As interaction surfaces mimicking surfaces of β-hairpins/β-sheet folds of IAPP are likely required for inhibitory function, the present inventors first asked whether cyclization of partially disordered 1 would affect its function and synthesized its cyclic analog ta (FIG. 1). Amyloid formation of Aβ40 and IAPP alone or with ta were followed by ThT binding assay and results confirmed by TEM (FIG. 2). In addition, aged solutions were added to cells and cell-damage studied by the 3-[4,5 dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTI) reduction assay in rat pheochromocytoma (PC12; Aβ40) or rat insulinoma (RIN5fm; IAPP) cells. 1a strongly suppressed amyloidogenesis and cell-damaging effects of Aβ40 (FIGS. 2a,b,e). Titrations of cytotoxic Aβ40 species with 1a yielded an IC.sub.50 of 79.8 (±30.3) nM which was nearly identical to the IC.sub.50 of 1(Table 1). Moreover and in contrast to 1, 1a also strongly suppressed amyloid self-assembly and cell damage by IAPP; an IC.sub.50 of 126 (±39.1) nM was determined (FIGS. 2c,d,e; Table 1). The cyclic constraint of 1a is thus fully compatible with potent amyloid inhibitory function toward both Aβ40 and IAPP.

TABLE-US-00001 TABLE 1 IC.sub.50 of inhibitory effects on cell-damaging amyloid self-assembly of Aβ40 or IAPP. IC.sub.50 (±SD) IC.sub.50 (±SD) (nM) Aβ40 (nM) IAPP Peptide inhibition.sup.[a] inhibition.sup.[a] R3-GI (1)    116 (±11).sup.[5] n.d..sup.[b] 1a  79.8 (±30.3)   126 (±39.1) 2  n.d..sup.[b] n.d..sup.[b] 2a  125.1 (±73.4)  47.6 (±15.5) 2b 654.3 (±227.8) 425.7 (±77.7) 2c   204 (±83.6) n.d..sup.[b] 2d 702.6 (±339.3) n.d..sup.[b] 2e 542.5 (±240.7) n.d..sup.[b] .sup.[a]IC.sub.50s, means (±SD) from 3-4 titration assays (n = 3 each) (Aβ40, 500 nM; IAPP, 100 nM). .sup.[b]n.d., non-determined (non-inhibitor).

[0134] To reduce the size of 1, the inventors synthesized its analog 2 lacking region IAPP(8-13). N-terminal truncation was based on the suggestion that IAPP(14-18) and IAPP(22-28) mediate key interactions for both IAPP self- and hetero-assembly. However, 2 was unable to block amyloid self-assembly of the two polypeptides (FIGS. 2a-d).

[0135] The inventors hypothesized that conformational restriction of 2 via cyclization might restore inhibitory function and synthesized 2a with two flanking disulfide-bridged cysteines (FIG. 1). In fact, 2a blocked Aβ40 cytotoxic self-assembly with an IC.sub.50 of 125.1 (±73.4) nM which is close to the IC.sub.50 of 1 (FIGS. 2a,b,e; Table 1). Moreover, 2a blocked IAPP cytotoxic self-assembly as well; an IC.sub.50 of 47.6 (+15.5) nM was determined consistent with 2a being even more potent (˜3-fold) than the longer ta (FIGS. 2c,d,e, Table 1). Interestingly, the far-UV CD spectra of both cyclic and linear peptides had similar shapes and were indicative of random coil and β-sheet/β-turn contents at ˜1/1 ratio (FIG. 2f). Differences between inhibitory activities might thus be due to stabilization of specific folds enabling specific side chain topologies and high affinity functional interactions with Aβ40 or IAPP. Indeed, fluorescence spectroscopic titrations revealed mid-nanomolar app. K.sub.ds for interactions of cyclic inhibitors ta and 2a with N-terminal fluorescently labeled Aβ40 or IAPP as previously found for 1, whereas much weaker binding was found for the non-inhibitor 2.

[0136] Recent findings suggest that IAPP residues Phe15, Leu16, Phe23 and Ile26 are key residues of IAPP-IAPP and IAPP-Aβ40(42) interactions and that the nature of the linker tripeptide determines ISM function. Aiming at minimizing IAPP-derived elements, the inventors next asked if these 4 residues and the RRR linker would be sufficient for amyloid inhibitory function and synthesized analog 2b with 7 out of the 11 non-Gly residues of 2a substituted with Gly (except for Cys); only the side chains of the above 4 residues were maintained (FIG. 1).

[0137] Remarkably, 2b strongly suppressed amyloid self-assembly and cell-damaging effects of both Aβ40 (IC.sub.50, 654.3 (±227.8) nM) and IAPP (IC.sub.50, 425.7 (±77-7) nM) (FIG. 3, Table 1). Such suppressive effect was not, or to a much lesser degree, seen for mutant peptides in which one or several of residues F15, L16, F23 and 126 had been replaced by Ala (data not shown). In addition, fluorescence spectroscopic titrations yielded mid-nanomolar app. K.sub.ds for the interactions of 2b with fluorescently labeled Aβ40 and IAPP which were in a similar range to the IC.sub.50s (data not shown). The CD spectrum of 2b exhibited one major minimum at 230 nm, which was indicative of stabilized turn structures (FIG. 3f). The 4 IAPP key residues and the RRR tripeptide arranged within the cyclic oligoglycine scaffold of 2b may thus comprise a motif mediating cross-amyloid inhibitor function; moreover, the potent inhibitory effects of 2b toward amyloid self-assembly of both Aβ40 and IAPP make it a lead for anti-amyloid drugs.

[0138] Resistance toward plasma proteases is an important requirement for any drug candidate. Therefore, the inventors determined the proteolytic stabilities of the above peptides in human plasma in vitro using RP-HPLC and MALDI-TOF-MS. Unfortunately, all of them were rapidly degraded; half-life times (t.sub.1/2) were <1 h (FIG. 4a).

[0139] To improve the proteolytic stability of 2b, 3 rounds of sequence optimization were performed next (FIG. 1). First, analog 2c with 3 D-Arg in the linker region instead 3 L-Arg was synthesized followed by 2d in which, in addition, Phe and Leu residues were replaced by D-ones. However, t.sub.1/2 values were only slightly improved (˜1-2 h) (FIG. 4a). Thus, 2e in which additionally the two L-Cys were replaced by D-Cys was synthesized. Most importantly, 2e exhibited highly improved proteolytic stability also in comparison to other peptides (t.sub.1/2>11 h) being >30-fold more resistant than 1 (t.sub.1/2˜20 min) and >15-fold more resistant than its L-precursor 2b (t.sub.1/2˜45 min) (FIG. 4a).

[0140] The inventors next asked whether switching chiralities may have affected 2b structure and function. In fact, the shapes of the CD spectra of 2c-2e were similar to 2b but their minima were blue-shifted indicative of different types of turns and/or .sub.β-strand contents (data not shown). However, 2c, 2d, and 2e bound both A.sub.β40 and IAPP with similar high affinities to 2b (data not shown). Notably, all three peptides were nanomolar inhibitors of A.sub.β40 amyloid self-assembly; their IC.sub.50 values were similar to the IC.sub.50 of 2b (FIGS. 3a-e, Table 1). Most remarkably, all of them lost the ability of 2b to block IAPP amyloidogenesis, which rendered them into A.sub.β40-selective inhibitors; notably, 2e selectivity was maintained for up to an at least 50-fold molar excess to IAPP (FIGS. 3c,d,e).

[0141] Next, the inventors studied effects of MCIPs on Aβ42 amyloidogenesis. In fact, all of them strongly suppressed formation Aβ42 fibrils and cell-damaging assemblies (FIGS. 4b,c). Titrations of N-terminal fluorescently labeled Aβ42 (FITC-Aβ42) (5 nM) with MCIPs revealed mid-to-low nanomolar binding affinities (data not shown). Most importantly, ex vivo electrophysiological studies in mouse brains showed that 2a, 2b and 2e ameliorated Aβ42-mediated inhibition of hippocampal synaptic long term potentiation (LTP) which is linked to loss of memory and cognitive functions in AD; these results support the physiological relevance of the in vitro results (FIGS. 4d,e).

[0142] Blood-brain-barrier (BBB) crossing is a highly desirable property for drug candidates targeting the amyloid cascade in AD. However, the highly restrictive nature of the BBB allows for only very few neuropharmaceuticals to be delivered to the brain. MCIP 2e is a quite small (<2 kDa) macrocyclic peptide containing an RRR segment, two amide bond N-methylated residues, 4 aromatic/large hydrophobic residues, and 8 flexible Gly residues; these are all features linked to membrane permeability. Thus, the inventors next studied whether N-terminal fluorescein-labeled 2e (Fluos-2e) can cross the BBB by using a well-established cell model of human cerebral microvascular endothelial cells (hCMECs) grown as confluent monolayers on Transwell membranes. In fact, Fluos-2e crossed the monolayer with an apparent permeability (P.sub.app) at 2 h of 14.6×10.sup.−6 (±3.36) cm/s (mean (±SEM), n=3), which is similar to the P.sub.app of other BBB crossing peptides (FIGS. 4f,g). Of note, hCMECs express substantial surface levels of the prominent brain protease neprilysin and 2e was fully resistant to degradation in an in vitro human neprilysin digestion assay (data not shown).

[0143] The present inventors were thus able to design and produce highly potent amyloid inhibitors of both Aβ40(42) and IAPP, or of Aβ40(42) alone. They also showed that the chirality of these inhibitors controls inhibitor selectivity. Furthermore, a systematic sequence optimization led to inhibitor 2e, which is a nanomolar Aβ40(42)-selective inhibitor which exhibits high proteolytic stability in human plasma and human blood-brain-barrier crossing ability in a cell model which are two highly desirable properties for anti-amyloid drugs in Alzheimer's disease.