IMIDAZOLE DERIVATIVES AS PRODRUGS OF DICLOFENAC

Abstract

The present invention relates to a compound of formula (I):

##STR00001## wherein R.sub.1 is R.sub.3-IPU and R.sub.2 is the acyloxy residue of diclofenac, and specified by the following structures:

##STR00002## wherein OH—R.sub.3-IPU is selected from

##STR00003## and R.sub.4 and R.sub.5 may be the same or different selected from H and CH.sub.3 and salts, solvates and hydrates thereof.

Claims

1. (canceled)

2. The composition according to claim 13, wherein the compound is selected from the group consisting of: ##STR00011## and salts, solvates and hydrates thereof.

3. The composition according to claim 1, wherein the compound has the following structure ##STR00012## or a salt, solvate or hydrate, thereof.

4. The composition according to claim 1, wherein the compound has the following structure ##STR00013## or a salt, solvate or hydrate, thereof.

5. The composition according to claim 3, further comprising at least one pharmaceutically acceptable carrier, vehicle and/or adjuvant.

6. The composition according to claim 5, wherein the composition is suitable for intra-articular injection.

7.-12. (canceled)

13. A composition comprising a compound of a formula: ##STR00014## wherein R.sub.3 is —CH.sub.2—CH.sub.2— or —CH.sub.2—CH.sub.2—CH.sub.2—; and R.sub.4 and R.sub.5 are independently selected from H and CH.sub.3; and salts, solvates and hydrates thereof.

14. The composition according to claim 4, further comprising at least one pharmaceutically acceptable carrier, vehicle and/or adjuvant.

15. The composition according to claim 14, wherein the composition is suitable for intra-articular injection.

16. A method of treating pain and/or inflammation in a joint, comprising: injecting into the synovial fluid of the joint a solution having a pH of 6 or less and comprising a dissolved compound of a formula: ##STR00015## wherein R.sub.3 is —CH.sub.2—CH.sub.2— or —CH.sub.2—CH.sub.2—CH.sub.2—; and R.sub.4 and R.sub.5 are independently selected from H and CH.sub.3; or a salts, solvates or hydrates thereof; and forming a precipitate of the compound in the joint.

17. The method of claim 16, wherein the pain and/or inflammation in the joint is postoperative pain following arthroscopic surgery.

18. The method of claim 16, wherein the solution further comprises a local anesthetic agent.

19. The method of claim 18, wherein the local anesthetic agent is selected from the group consisting of: amethocaine, chlorprocaine, etidocaine, lidocaine, bupivacaine, mepivacaine, prilocaine, ropivacaine, and procaine.

20. The method of claim 16, wherein the solution further comprises an opiod or an analgesic agent.

21. The method of claim 20, wherein the opiod or strong analgesic agent is selected from the group consisting of: alfentanil, alphaprodine, anileridine, buprenorphine, buturphenol, codeine, dextromoramide, dextroproproxyphene, dihydrocodeine, fentanyl, dydrocodone, hydromorphone, ketobemidone, meptazinol, methadone, morphine, oxycodone, oxymorphone, pentazocine, pethidine, phenazocine, phenoperidine, and sulfentanil.

22. The method of claim 16, wherein the compound has the following structure ##STR00016## or a salt, solvate or hydrate, thereof.

23. The method of claim 16, wherein the compound has the following structure ##STR00017## or a salt, solvate or hydrate, thereof.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0068] FIG. 1 shows factors influencing the pharmacokinetic fate of the prodrug/drug after administration of the prodrug into the joint. The prodrug dissolved is converted into the active drug by enzymatic cleavage of the prodrug bond.

[0069] FIG. 2 shows the X-ray powder diffraction diagram of PPX-1-0018.

[0070] FIG. 3 shows the X-ray powder diffraction diagram of PPX-1-0023.

[0071] FIG. 4. Mean±SEM ipsilateral joint compression thresholds in vehicle, DPX-1-0018, or Diclofenac-treated animals during the pharmacological assessment period. All animals received an intra-articular injection of vehicle (0.01% Tween 80 in phosphate buffer) or DPX1-0018 (0.3 mg) on day 0, or Diclofenac via oral gavage on day 8 (n=10). ++/+++: p<0.01/0.001 vs. day 8 baseline value/vehicle.

[0072] FIG. 5. Mean±SEM ipsilateral joint compression thresholds in vehicle, DPX-1-0023, or Diclofenac-treated animals during the pharmacological assessment period. All animals received an intra-articular injection of vehicle (0.01% Tween 80 in phosphate buffer) or DPX1-0023 suspension (0.3 mg) on day 0, or diclofenac via oral gavage on day 8 (n=10). +: p<0.05 vs. vehicle-treated animals; ++/+++: p<0.01/0.001 vs. day 8 baseline value.

[0073] FIGS. 6 and 7. Particle size distribution of DPX-1-0023.

[0074] The invention is illustrated in, but not limited to, the following examples.

EXAMPLES

[0075] General Procedure for Synthesis of Compounds According to the Invention

##STR00008##

[0076] General procedure for the synthesis of prodrugs: Diclofenac free acid (2.96 g, 10 mmol), alcohol (10 mmol) and DMAP (122 mg, 1 mmol) was dissolved in CH.sub.2Cl.sub.2 (25 mL) and cooled to 0° C. in an ice-bath. A solution of DCC (4.12 g, 20 mmol) in CH.sub.2Cl.sub.2 (25 mL) was added dropwise over the course of 30 minutes. After complete addition the reaction was allowed to reach room temperature over 3 hrs. The reaction was filtered and the filtrate was evaporated to give a pale yellow oil which was purified by flash chromatography (0-10% 2M methanolic NH.sub.3 in EtOAc) to give the desired ester.

Example 1—Synthesis of DPX-1-0018

[0077] ##STR00009##

[0078] Prepared from 4-(1H-imidazol-1-yl)butan-1-ol by general procedure A in 70% yield. The free base was dissolved in EtOH (0.1 g/mL) and treated with 1.2 equiv. of PhSO3H in EtOH. Dilution with Et2O resulted in precipitation of crystals which was isolated by filtration to give the besylate salt as colorless crystals.

[0079] Characterization of DPX-1-0018

[0080] 2.1 1H NMR Data

[0081] 1H NMR (600 MHz, CDCl3) δ 7.46 (s, 1H), 7.28 (d, J=8.1 Hz, 2H), 7.15 (dd, J=7.6, 1.5 Hz, 1H), 7.06 (td, J=7.8, 1.5 Hz, 1H), 6.99 (s, 1H), 6.92 (t, J=8.1 Hz, 1H), 6.88 (td, J=7.4, 1.0 Hz, 1H), 6.78 (s, 1H), 6.75 (s, 1H), 6.48 (d, J=8.0 Hz, 1H), 4.10 (t, J=6.4 Hz, 2H), 3.85 (t, J=7.1 Hz, 2H), 3.74 (s, 2H), 1.78-1.70 (m, 2H), 1.62-1.54 (m, 2H). 13C NMR (151 MHz, CDCl3) δ 172.4, 142.8 (2C), 137.8, 137.0, 131.0, 129.7, 129.1 (3C), 128.3, 124.3 (2C), 122.2, 118.9, 118.4, 64.4, 46.8, 38.8, 27.7, 25.8.

[0082] 2.2 XRPD

[0083] Crystallilne—see FIG. 2.

Example 2—Synthesis of DPX-1-0023

[0084] ##STR00010##

[0085] DPX-1-0023 is prepared from 2-(4,5-dimethyl-1H-imidazol-1-yl)ethanol by general procedure A in 75% yield.

[0086] Characterization of DPX-1-0023

[0087] The compound is obtained in the base form.

[0088] 2.2 NMR Data

[0089] .sup.1H NMR (free base, 600 MHz, CDCl.sub.3) δ 7.28 (s, 1H), 7.27 (d, J=8.1 Hz, 2H), 7.12 (d, J=7.5 Hz, 1H), 7.07 (t, J=7.7 Hz, 1H), 6.92 (t, J=8.1 Hz, 1H), 6.90 (t, J=7.6 Hz), 6.63 (s, 1H), 6.48 (d, J=8.0 Hz, 1H), 4.26 (t, J=5.6 Hz, 2H), 4.00 (t, J=5.6 Hz, 2H), 3.74 (s, 2H), 2.07 (s, 3H), 2.03 (s, 3H). .sup.13C NMR (free base, 150 MHz, CDCl.sub.3) δ 172.1, 142.8 (2C), 137.8, 135.3, 133.9, 131.1, 129.6, 129.0 (2C), 128.4, 124.3, 123.9, 122.4, 122.1, 118.5, 63.8, 43.6, 38.5, 12.7, 8.5.

[0090] 2.3 XRPD

[0091] Crystalline—see FIG. 3.

[0092] 2.4 Melting Point (DSC), CHN-Analysis and TGA

TABLE-US-00001 Batch Form MP (DSC) MHX075 base 129.3 MHX113 base 129.2

[0093] 2.5 pKa-Value

[0094] The pKa-value for DPX-1-0023 at 25° C. using a GLpKa meter was found to 7.92.

[0095] 2.6 HPLC Analysis

[0096] HPLC System A

[0097] Samples were analyzed on an Elite LaChrom HPLC system (VWR International, Tokyo, Japan) employing a Merck-Hitachi L-2130 pump connected to a Merck Hitatchi L-2450 diode array detector and a VWR-Hitachi L-2200 autosampler. Reversed phase chromatography was performed using a Gemini C18 column (150×4.60 mm; 5 μm particles, Phenomenex, Allerød, Denmark) equipped with a Gemini C18 precolumn (4×3.0 mm, Phenomenex, Allerød, Denmark) heated at 30° C. by a VWR Hitachi L-2300 column oven. The mobile phase consisted of methanol and 0.02 M acetate buffer pH 4.4 in ratio (v/v) of 65:35. The flow rate was set at 1 ml/min and the column effluent was monitored at 275 nm. Retention time 3.9 min for DPX-1-0023, 8.0 min for diclofenac.

[0098] The retention time is strongly dependent on pH and thus changes must be expected between batches of mobile phases and also the matrix the prodrug is dissolved in.

[0099] 2.7 Solubility

[0100] A surplus of prodrug was added to either PBS pH 7.4 or H.sub.2O. 0.1 M HCl was added to the H.sub.2O to decrease pH to around 3-4. The mixtures were rotated at 37° C. and a sample was withdrawn after approximately 24 and 48 hours or later. The withdrawn sample was filtered through a 0.45 μm Millex®-HV (Millipore, Japan) low protein binding filter (the first 0.5 mL discarded) and a known volume of the sample was diluted. The pH 7.4 samples were diluted with PBS and the acidic samples with mobile phase A (section 2.5). A standard dissolved in PBS was made for the pH 7.4 samples and a standard dissolved in mobile phase A for the acidic samples. The PBS standards used for the standard curves were treated like the samples to avoid false results caused by adsorption. The standard curves were made to cover the concentration interval of the samples after dilution.

[0101] From the observed relatively stable concentration of dissolved prodrugs measured in the suspensions after 8-9 day up to 23 days, the solubilities of the prodrugs (S.sub.prodrug) were determined. In this time interval, the rate of appearance of parent drug was determined and an apparent pseudo-zero-order rate constant (k.sub.0) was obtained. By assuming that the dissolution rates were much faster than the conversion of the prodrugs to the parent drug, pseudo first-order rate constants (k.sub.hyd) for cleavage of the prodrugs were calculated according to:

[00001]$-\frac{d\left[\mathrm{Prodrug}\right]}{\mathrm{dt}}=\frac{d\left[\mathrm{Drug}\right]}{\mathrm{dt}}=k_{\mathrm{hyd}}.Math.S_{\mathrm{prodrug}}=k_0$

[0102] All data are summarized in Table 1.

TABLE-US-00002 TABLE 1 Solubilities of DPX-1-0023 in 67 mM phosphate buffer pH 7.4 and in hydrochloride solutions at pH 4.35 at 37° C. n = 6 (equal solubilities were obtained after 1 and 2 days of rotation). pH S (μg/ml) S (mM) 4.35 3019 ± 62 7.2 ± 0.1 7.4  2.7 ± 0.2 0.0064 ± 0.0005

[0103] 2.8 Stability

[0104] Stability in PBS 7.4, 80% (v/v) Plasma, 80% (v/v) SF and 80% (v/v) Rat Serum

[0105] The stability of the prodrugs was determined in PBS, 80% human SF, 80% human plasma and 80% rat serum at 37° C. 10, 20 or 50 μL of prodrug solution in MeOH was added to 1.0 mL 80% rat serum, 2.5 mL 80% SF or human plasma or 10.0 mL PBS, respectively to give a final prodrug concentration corresponding to the solubility at pH 7.4 at 37° C. Samples were withdrawn at appropriate intervals depending on the rate of degradation. The samples from the biological medias were added to MeCN (1:2 (v:v)) vortexed and centrifuged (5 min, 10000 RPM) and the supernatant analyzed by HPLC. The 700 μL PBS samples were added to 100 μL PBS and mixed before analysis by HPLC. First a pilot study was performed with n=1 to find the appropriate sampling times and thereafter an experiment with n=3. The stability was determined from the decrease in the area of prodrug.

TABLE-US-00003 TABLE 2 Half-lifes of DPX-1-0023 in 80% plasma, spinal fluid (SF), rat serum and phosphate buffer solution (PBS) at 37° C. SF batch Plasma 210513 Rat serum PBS T.sub.1/2 (min) 5.1 ± 0.5 39.8 ± 2.8 6.1 ± 0.4 1083 ± 164 (0.75 days)

[0106] The data reveal that that the prodrug is much instable in the 3 biological media (same pH as PBS) as compared with the stability in PBS. Thus, in the 3 biological media, prodrug cleavage to yield active diclofenac involves catalysis by hydrolytic enzymes present in these matrices.

Example 3

[0107] Animal Studies

[0108] The aim of the animal study is given in the following.

[0109] Osteoarthritis is the most common form of joint disease. Nearly one third of adults in the United States suffer from osteoarthritis and it is the most common cause of disability in adults in the United States. The monosodium iodoacetate (MIA) model of osteoarthritis described here produces changes in the structure and integrity of the affected cartilage that is very similar to what is seen in human osteoarthritis. Sodium iodoacetate is a metabolic inhibitor that, when injected into the joint space, selectively kills chondrocytes, the cells that form cartilage. Over a period of 2-3 weeks, the loss of cartilage produces a state highly analogous to human osteoarthritis characterized by joint instability, loss of cartilage, and decreased bone quality around the affected joint. These physiological changes are also accompanied by pain in the affected joint.

[0110] In this study, osteoarthritis was induced by a single injection of MIA (2 mg) into the synovium of the left knee, which results in increased sensitivity to pressure. For this particular study, the test compounds were given 14 days post-MIA injection to determine if the test compound can reduce the sensitivity.

[0111] Study Design

[0112] Vehicle (0.01% Tween 80 in phosphate buffer) administered intra-articularly at a dose volume of 30 μl on day 0.

[0113] Test articles DPX-1-0008, DPX-1-0011, DPX-1-0018, DPX-1-0020, DPX-1-0023, and DPX-1-0024, administered intra-articularly at a dose of 0.3 mg on day 0.

[0114] Diclofenac, administered orally at a dose of 10 mg/kg on day 8 to the vehicle group.

[0115] Methods

[0116] A total of 82 male, Sprague-Dawley rats underwent MIA injection with the goal of having 70 animals available for the pharmacology treatment due to 15% failure of developing a pain state. Fourteen days after MIA injection, animals met the inclusion criteria were assigned to one of seven groups (vehicle, test article DPX-1-0008, DPX-1-0011, DPX-1-0018, DPX-1-0020, DPX-1-0023, and DPX-1-0024) and received the assigned treatment. Joint compression thresholds were assessed prior to MIA injection, prior to dosing with control/test articles, and 1, 2, 4, and 7 days post-dosing. Diclofenac served as the positive control for the study. On day 8, animals in the vehicle group received diclofenac (10 mg/kg, PO) and joint compression were assessed prior to, 1 and 2 hours after dosing for all the animals. All animals were euthanized on day 8 following the behavioral assessment.

[0117] Results

[0118] Injection of 2 mg MIA into the knee significantly decreased joint compression thresholds 14 days after injection. Intra-articular administration of DPX-1-0018 (0.3 mg) significantly increased mean joint compression thresholds 8 days post-dosing compared to the vehicle group. Intra-articular administration of DPX-1-0020 (0.3 mg) significantly increased mean joint compression thresholds 8 days post-dosing compared to the vehicle group. Intra-articular administration of DPX-1-0023 (0.3 mg) significantly increased mean joint compression thresholds 1 day post-dosing compared to the vehicle group.

[0119] Oral administration of the positive control, diclofenac (10 mg/kg), significantly increased mean joint compression thresholds 1 and 2 hours post-dosing compared to baseline values on day 8.

[0120] A graphic presentation of the results is shown in FIGS. 4 and 5.

CONCLUSION

[0121] A single intra-articular administration of 0.3 mg test articles DPX-1-0018, or DPX-1-0023 significantly reversed osteoarthritis pain induced by a single injection of MIA compared to vehicle treated animals.

Example 4

[0122] Characterization of Suspension for Animal Studies

[0123] The suspension was made by adding a known volume of a solution consisting of 0.01% Tween 80, 0.4% NaCl and 67 mM PBS pH 7.4 to a known amount of DPX-1-0023 to give a final prodrug concentration of 10 mg/mL (min 3.5 mL). This was then given 5×60 s ultrasound in a Covaris S2 with all parameters at max.

[0124] The resulting suspension was vortexed and 2×750 μL transferred by a 200-1000 μL pipette to a capped vial. The vial was closed with a Teflon coated rubber lid and sealed with an aluminum cap. This was done twice. One vial was used in animal studies and the other was used for characterizing the suspension.

[0125] Repetition of Injections:

[0126] Method: After 20 s mixing on a Vortex mixer 30 μL suspension was withdrawn with a 27 G×20 mm injection needle equipped with a 100 μL Hamilton glass syringe and diluted to 10.00 mL with mobile phase. This was repeated 10 times.

[0127] 8.3±0.4 mg/mL DPX-1-0023 was found.

[0128] Particle Size Distribution:

[0129] Method: The particle size distribution was measured by laser diffraction with Malvern Mastersizer 2000 particle size analyzer using the Hydro 2000S wet sample dispersion unit (Malvern Instruments Ltd, Worcestershire, UK). After 20 s vortexing approximately 500 μL 10 mg mL.sup.−1 suspension was added to 67 mM phosphate buffer pH 7.4 (120 mL) in the dispersion unit until the laser obscuration range was maintained between 2 and 5%. The suspension was stirred at 1015 rpm and a measurement time of 12 s applied. The results are shown in FIGS. 6 and 7.

[0130] Diclofenac Content:

[0131] Method: 300 μL of the suspension (no vortexing) was centrifuged (5 min, 13.500 RPM, RT) and 2×100 μL of the supernatant was transferred to 200 μL mobile phase A, mixed and analyzed by HPLC.

[0132] Result:

[0133] 3.6 μg/mL diclofenac was found in the suspension on the day of injection.

Example 5

[0134] Pharmaceutical Composition—Dispersion/Suspension

[0135] The dispersion/suspension contains:

from about 2 to about 50 mg/ml of diclofenac prodrug,
sufficient isotonic adjusting substance to obtain an isotonic composition (eg glycerol or sodium chloride), eg from about 0.4 to about 0.9% w/v of sodium chloride,
optionally, from about 0.001 to about 0.1 mg/ml of a surfactant,
buffer solution pH 7.4.

[0136] A specific example is given in the following.

[0137] A suspension was made by adding a known volume of a solution consisting of 0.01% Tween 80, 0.4% NaCl and 67 mM PBS pH 7.4 to a known amount of DPX-1-0023 to give a final prodrug concentration of 10 mg/mL (min 3.5 mL). This was then given 5×60 s ultrasound in a Covaris S2 with all parameters at max.

[0138] The resulting suspension was vortexed and 2×750 μL transferred by a 200-1000 μL pipette to a capped vial. The vial was closed with a Teflon coated rubber lid and sealed with an aluminum cap. This was done twice. One vial was used in animal studies and the other was used for characterizing the suspension.

Example 6

[0139] Pharmaceutical Composition—in Solid Form to be Reconstituted with Aqueous Medium Before Application

[0140] A well-defined amount of diclofenac prodrug, preferably in lyophilized form, is contained in a vial. The vial may also contain one or more solubilizers, one or more buffering agents, one or more pH adjusting agents and/or one or more isotonic adjusting agents.

[0141] Before administration an aqueous medium is added. The aqueous medium may have a pH value of from 1 to 4 in those cases where a solution is desired. The aqueous medium may contain one or more solubilizers, one or more buffering agents, one or more pH adjusting agents, one or more isotonic adjusting agents and/or one or more co-solvents. In the event the ready-to-use composition is a solution,

[0142] The composition may also be provided in the form of a kit containing eg two vials, one containing lyophilized prodrug and the other containing an aqueous medium. Before administration the aqueous medium is added to the vial containing the lyophilized prodrug.

REFERENCES

[0143] Ref. 1: Reuben et al. [0144] Reuben S. S., Connelly N. R. (1995) Postoperative analgesia for outpatient arthroscopic knee surgery with intraarticular bupivacaine and ketorolac. Anesth Analg 80: 1154-1157 [0145] Ref 2: Rasmussen et al. [0146] Rasmussen S., Larsen A. S., Thomsen S. T., Kehlet H. (1998) Intra-articular glucocorticoid, bupivacaine and morphine reduces pain, inflammatory response and convalescence after arthroscopic meniscectomy. Pain 78: 131-134 [0147] Ref 3: R. Williams [0148] pKa Data Compiled by R. Williams (downloadable from http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf) [0149] Ref 4: Caballero et al. [0150] Caballero et al. (2006) “Theoretical prediction of relative and absolute pKa values of aminopyridines”, Biophysical Chemistry 124(2), p 155-160 (Ref. 3). [0151] Ref 5: Drustrup et al. [0152] Drustrup et al. (1991) “Utilization of prodrugs to enhance the transdermal absorption of morphine”, International Journal of Pharmaceutics 71, 105-116