NEW IMPROVED FORMULATION FOR TREATMENT OF THROMBOEMBOLISM

Abstract: A new pharmaceutical formulation comprising the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab in combination with medium chain glycerides, a process for the preparation of such a pharmaceutical formulation, the use of such formulation in the treatment of thromboembolism as well as a method of treating a patient in need of such a treatment by using said formulation.

Description: NEW IMPROVED FORMULATION FOR TREATMENT OF THROMBOEMBOLISM Field of the invention The present invention relates to a new pharmaceutical formulation comprising the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab in combination with one or more absorption enhancing medium chain glyceride lipid agents, a process for the preparation of such a pharmaceutical formulation, the use of the thrombin inhibitor and the absorption enhancing agent for the preparation of a pharmaceutical formulation for the treatment of thromboembolism as well as a method of treating a patient in need of such a treatment by using said formulation. Background Blood coagulation is the key process involved in both haemostasis (i.e. prevention of blood loss from a damaged vessel) and thrombosis (i.e. the pathological occlusion of a blood vessel by a blood clot). Coagulation is the result of a complex series of enzymatic reactions, where one of the final steps is conversion of the proenzyme prothrombin to the active enzyme thrombin. Thrombin plays a central role in coagulation. It activates platelets, it converts fibrinogen into fibrin monomers, which polymerise spontaneously into filaments, and it activates factor XLπ, which in turn crosslinks the polymer to insoluble fibrin. Thrombin further activates factor V and factor VIII in a positive feedback reaction. Inhibitors of thrombin are therefore expected to be effective anticoagulants by inhibition of platelets, fibrin formation and fibrin stabilization. By inhibiting the positive feedback mechanism they are expected to excert inhibition early in the chain of events leading to coagulation and thrombosis. Peptidic or peptidic like thrombin inhibitors as many other peptide like substances, are prone to limited or variable absorption when administered orally. This is due to the influence from different barriers of metabolic and physical character, like enzymatic degradation, tendencies of complex formation with components from the formulation or the biological environment, limitations in transport over the intestinal membranes etc. One object of the pharmaceutical formulation is to facilitate the active agent in overcoming such barriers, and to obtain an enhanced and reproduceable absoφtion of the active agent. Formulation components that have such influence and thus can help the active agent are called absoφtion enhancers. Prior Art Concerning the use of absoφtion enhancers of lipidic origin in pharmaceutical formulations, several reports and reviews in the literature exist. Comprehensive reviews have been presented by E J van Hoogdalem et al., Pharmac Theor vol 44, 407-443 (1989), by S Muranishi, Crit Rev Ther Drug Carrier Syst vol 7, 1-33 (1990), by E S Swenson and W J Curatolo, Adv Drug Deliv Rev vol 8, 39-92 (1992), and in drug Absoφtion Enhancement (Ed.: A B G de Boer), Harwood Academic Publishers 1994. Specifically, medium chain glycerides have been studied and reported as absoφtion enhancers in a number of papers, see references above and references therein. The main interest has been to utilize mixtures of mono-, di-, and triglycerides with 6 - 12 carbon atoms in the chains, i e mono-, di-, and triacylglycerides. More or less well defined samples of glycerides have been used, e g glyceryl mono-octanoate (Tramedico), Capmul MCM (Karlshamns Lipidteknik), Nikkol MGK (Nikko Chemicals), SunSoft (Taiyo Kagaku), Imwitor (Huls), Labrasol (Gattefosse), LAS (Gattefosse), and Labrafac Lipo (Gattefosse). Only a few reports deal with effects obtained when the glycerides have been perorally administered (Sekine et al. J Pharmacobio-Dyn 8, 286 ( 1985); Beskid et al. Chemotherapy 34, 77 ( 1988)). Several other studies report results when liquid formulations of the glycerides have been administered rectally (Sekine et al. J Pharmacobio-Dyn 7, 856 (1984); ibid 8, 633, 645, and 653 (1985); van Hoogdalem et al. J Pharm Pharmacol 40, 329 (1988), Pharm Res 5, 453 (1988); Unowsky et al. Chemotherapy 34, 272 (1988); Watanabe et al. J Pharm Sci 77, 847 (1988); Matsumoto et al. Chem Pharm Bull 37, 2477 (1989)), or directly as solutions or emulsions by infusion or bolus into different parts of the small intestine (Petty et al. at "Interci Conf on Antimicrobial Agents and Chemotherapy", New Orleans 1986, abstract 1245; Higaki et al. J Pharmacobio-Dyn 9, 532 (1986), Int J Pharm 36, 131 (1987); Yeh et al. Proceed Intern Symp Control Rel Bioact Mater (CRS), 20, 176 (1993); Constantinides et al. CRS 20, 184 (1993); CRS 21, 62 (1994); Marks et al. CRS 22 (1995); Yeh et al. Pharm Res 11, 1 148 (1994); Constantinides et al. Pharm Res 11, 1385 (1994), J Controlled Release 34, 109 (1995); Yeh et al. J Controlled Release 36, 109 (1995); Constantinides et al. Pharm Res 12, 1561 (1995)). The glycerides were used either as such, or in mixtures with dispersing agents like lecithins and surfactants to form aggregates like mixed micelles, microemulsions, dispersed lamellar phases etc, or to form self-emulsifying systems. A few patents have also claimed the use of such glycerides in formulations, e g as components in microemulsions (Constantinides WO 94/19003 and references therein), and in selfemulsifying systems with lecithins (Herslδf WO 92/05771 and references therein). Disclosure of the invention It has been found that the absoφtion of the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze- Pab (disclosed in EP 701 568) can be modified beneficially by incoφorating medium chain glyceride lipid agent in the pharmaceutical formulations containing said therapeutically active compound. Therefore, an object of the present invention is to provide novel pharmaceutical formulations comprising the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab in combination with one or more medium chain glyceride lipid agents, and a process for the preparation of such pharmaceutical formulations. The improved formulations of this therapeutically active drug are based on the use of medium chain glycerides to obtain positive synergistic effects which result in an enhanced and/or less variable absoφtion when the therapeutically active agent is given by different administration routes, such as the oral, the rectal, the buccal, the nasal or the pulmonary route etc. The formulation may be manufactured with the active peptidic thrombin inhibitor HOOC- CH2-(R)-Cgl-Aze-Pab as commonly used salt or in its base form. The thrombin inhibitor may also be in other stereoisomeric configurations than the one above. The novel pharmaceutical formulations disclosed in this invention are unique combinations of the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab and the medium chain glyceride lipid agents as enhancing agents. Thus, first the use of these absoφtion enhancing agents in combinations with thrombin inhibitors have not presented before. Second, it has been found that glycerides from different sources behave differently, the most effecient enhancing effect being obtained with the pure glyceryl mono-octanoate (1- monocaprylin). Tentatively, the enhancing effects are considered to be due to combinations of several interactions, both between the glycerides and the gastro-intestinal membranes, and between the glycerides and the thrombin inhibitor. Thus, the (water-soluble) thrombin inhibitor is soluble in such glycerides without the use of (extra-added) water. Also, the phase diagram displayed by, e g the glyceryl monooctanoate in water (Larsson, Zeitschrift Phys Chem Neue Folge 56, 173 - 198 (1967), shows that a fluid isotropic phase (L2) is formed at a low water content. These inverted micelles will then provide aggregates with the thrombin inhibitor ready for absoφtion, the absoφtion events being enhanced by the presence of the fusogenic lipids. From the phase diagrams of longer medium chain glycerides, e g 1-monocaprin, it can be concluded that the higher temperature needed to obtain a fluid isotropic phase at low water content would make it more difficult for such glycerides to act as enhancers. Third, it has been found in experiments with different species (rat, dog, human) that a substantial enhancing effect is observed only when the thrombin inhibitor together with the medium chain glyceride lipid agents are administered directly to the small intestine, that is intraduodenal administration by the use of a duodenal tube, Hg - or tungsten - weighted tube or an endoscopy tube or by enteric coated formulations. On the other hand, direct administration to either the stomach or the colon results in negligable enhancing effects. This is in shaφ contrast to most other reports on enhancing effects from medium chain glycerides. Fourth, the formulations disclosed here are based on the use of medium chain glycerides, and mixtures thereof, without the requirements of dispersing the lipids with other agents such as emulsifiers for producing microemulsions, lecithins to provide self-emulsifying systems, or any other similar agent. Further, it is worth to emphazise that no water is needed in the formulation according to the invention. Medium chain glycerides according to the present invention is defined as compounds of the formula ChL-O-R, I CH-0-R 2 I CH 2 -0-R 3 wherein Rl, R2 and R3 are the same or different and each represent an hydrogen atom or acyl group having 6 - 12 carbon atoms provided that at least one of Rl, R2 and R3 is an acyl group. The dosage form used may be a solid, semisolid or liquid preparations prepared by per se known techniques. Usually the active substance will constitute between 0.1 and 99 % by weight of the preparation. Suitable daily doses of the therapeutically active drug in therapeutical treatment of humans are about 0.001 - 100 mg/kg body weight at peroral administration. The enhancing agent, or combinations of enhancing agents, will constitute between 0.1 and 99 % by weight of the preparation. The formulations thus obtained will increase the absoφtion and/or minimize the variability of the absoφtion of the therapeutically active drug by different mechanisms. The pharmaceutical formulations of the present invention comprising the modified dipeptide HOOC-CH2-(R)-Cgl-Aze-Pab and the absoφtion enhancing agent are intended for prophylaxis and treatment in arterial as well as venous thromboembolism. Detailed description of the invention The following description is illustrative of aspects of the invention. Experimental part Preparation of the formulations Formulation A: HOOC-CH 2 -(R)-Cgl-Aze-Pab (base) 0.43 mg/ml Akoline (Capmul MCM) Phosphate buffer 0.1 M , pH 8.0 1 ml of formulation contains 0.9 g of akoline + 0.1 g of buffer + 0.43 g of drug. Akoline was heated to 30°C and was mixed with the buffer containing the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab in the proportion of akoline: water 90:10. Formulation B: HOOC-CH 2 -(R)-Cgl-Aze-Pab (base) 0.43 mg/ml Akoline (Capmul MCM) 1 ml of formulation contains 1 g of akoline + 0.43 g of drug. Akohne was heated to 30°C and was mixed with the thrombin inhibitor HOOC-CH2-(R)- Cgl-Aze-Pab (base). Formulation C: HOOC-CH 2 -(R)-Cgl-Aze-Pab (base) 0.43 mg/ml Monoglyceride C8:0 Monoglyceride C10:0 Phosphate buffer 0.1 M, pH 8.0 1 ml of formulation contains 0.7 g of C8:0 + 0.26 g of C10:0 + 0.04 g of buffer + 0.43 g of drug. Monoglyceride C8:0 was heated to 35°C and the monoglyceride C10:0 was heated to 70°C. The mono-C10:0 was added to the mono-C8:0 in the proportions 26:70 respectively and the buffer solution containing the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab was added into the mixture to a total of 4%. The mixture was then shaken and kept warm (30°C) before administration. Formulation D: HOOC-CH 2 -(R)-Cgl-Aze-Pab (base) 0.43 mg/ml Monoglyceride C8:0 Phosphate buffer 0.1 M, pH 8.0 1 ml of formulation contains 0.95 g of C8:0 + 0.05 g of buffer + 0.43 g of drug. Monoglyceride C8:0 was heated to 30°C and the thrombin inhibitor HOOC-CH2-(R)-Cgl- Aze-Pab in phosphate buffer was added to the mixture to a total amount of 5%. The mixture was then shaken before administration. The formulations, A to D, respectively, were tested in vivo in the rat model using intraduodenally catheterised non-anaesthetised animals. Formulations were given as a bolus. Blood samples were withdrawn at certain time points for up to 4 hours after administration of the different formulation. The concentration of HOOC-CH2-(R)-Cgl-Aze-Pab were analysed in the plasma and the bioavailability calculated from the Area under the curve (AUC) using standard pharmacokinetic methods (Rowland and Tozer, Clinical Pharmacokinetics, concepts and applications, 1980). The results from the tested formulations A to D in vivo in the rat are presented in Table 1 as formulations 2-5. The bioavailability increase between tenfold to twentyfold using the different formulations mentioned in the invention as compared to control experiment where only phosphate buffer of pH 8 was used (1). Formulation B was also tested in human healthy subjects using enteric coated capsules for administration directly to the duodenum. The results from the human study also indicate a tenfold increased absoφtion as compared to a control tablet or solution of the thrombin inhibitor base only. All formulations tested containing the mono and / or di glycerides C8 and CIO increased the bioavailability of the thrombin inhibitor HOOC-CH2-(R)-Cgl-Aze-Pab suφrisingly well from the upper GI tract. Abbreviations Aze = (S) -Azetidine-2-carboxylic acid Cgl = (S) -Cyclohexyl glycine Pab = l-Amidino-4-aminomethyl benzene Table 1. Bioavailability of HOOC-CH2-(R)-Cgl-Aze-Pab in vivo in the rat after administration intraduodenally with formulations containing monoglycerides or mono- and diglyceride mixtures described in the invention. Numbers represent the mean values +- SD, where N indicates the number of animal used. Formulation Bioavailability (%) mean SD N 1. Phosphate buffer 0.1 M, pH 8.0 3.0 2.5 4 2. Capmul:water 90:10 37.2 9.2 4 3. Capmul 100% 55.5 14.6 4 4. Mono- C8/C10 : water 96:4 47.8 8.6 3 5. Mono C8 :water 95:5 73 5.1 3

Claims: CLAIMS 1. A pharmaceutical formulation comprising the therapeutically active compound HOOC- CH2-(R)CgI-Aze-Pab or a physiologically acceptable salt thereof and one or more absoφtion enhancing agents selected from the group of a mono-, di- or triglyceride comprising at least one acyl group of chain length of 6 to 12 carbon atoms. 2. A pharmaceutical formulation according to claim 1 wherein the acyl group contains 8 to 10 carbon atoms. 3. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of mono-, di- or triglycerides with acyl groups containing 8 carbon atoms. 4. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agents is selected from mixtures of mono- or diglycerides having acyl groups of 6 to 12 carbon atoms. 5. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of mono- or diglycerides having acyl groups of 8 to 10 carbon atoms. 6. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of mono- or diglycerides having acyl groups of 8 carbon atoms. 7. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of monoglycerides having acyl groups of 6 to 12 carbon atoms. 8. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of monoglycerides having acyl groups of 8 to 10 carbon atoms. 9. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a monoglyceride having its acyl group of 6 carbon atoms. 10. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a monoglyceride having its acyl group of 8 carbon atoms. 1 1. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a monoglyceride having its acyl group of 10 carbon atoms. 12. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a monoglyceride having its acyl group of 12 carbon atoms. 13. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of diglycerides having acyl groups of 6 to 12 carbon atoms. 14. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is selected from mixtures of diglycerides having acyl groups of 8 to 10 carbon atoms. 15. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a diglyceride having acyl groups of 6 carbon atoms. 16. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a diglyceride having acyl groups of 8 carbon atoms. 17. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a diglyceride having acyl groups of 10 carbon atoms. 18. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent is a diglyceride having acyl groups of 12 carbon atoms. 19. A mixture comprising the therapeutically active compound HOOC-CH2-(R)Cgl-Aze- Pab or a physiologically acceptable salt thereof and one or more absoφtion enhancing agents selected from the group of a mono-, di- or triglyceride comprising at least one acyl group of chain length of 6 to 12 carbon atoms. 20. Use of the thrombin inhibitor and the absoφtion enhancing agent as defined in any of the preceding claims 1 to 19 for the preparation of a pharmaceutical formulation for the treatment of thromboembolism by administration directly to the small intestine. 21. Use according to claim 20 wherein the formulation is adapted for the administration by a duodenal tube, a mercury or tungsten weighted tube or an endoscopy tube. 22. Use according to claim 20 or claim 21 wherein the formulation is enteric coated. 23. A method of treating a patient in need of antithrombolic treatment comprising administering to said patient a pharmaceutical formulation as defined in any one of the claims 1 to 19 by administration directly to the small intestine. 24. A method according to claim 23 wherein the administration is by use of a duodenal tube, mercury or tungsten weighted tube or an endoscopy tube. 25. A method according to claim 23 or claim 24 wherein the formulation is enteric coated. 26. A pharmaceutical formulation according to claim 1 wherein the absoφtion enhancing agent forms micelles which provides aggregates with the thrombin inhibitor.

Inventors: LINDFORS LENNART, LOEFROTH JAN-ERIK, UNGELL ANNA-LENA, LINDFORS, LENNART, LOEFROTH, JAN-ERIK, UNGELL, ANNA-LENA
Applicants: ASTRA AB, LINDFORS LENNART, LOEFROTH JAN ERIK, UNGELL ANNA LENA, ASTRA AKTIEBOLAG (PUBL), LINDFORS, LENNART, LOEFROTH, JAN-ERIK, UNGELL, ANNA-LENA
Application year: 1997
Main classification: A61K38
IPC codes: A61K9, A61K31, A61K38, A61K45, A61K47, A61P7