The present invention relates to a novel crystalline form of nelfinavir mesylate and processes for its preparation. The crystalline form of nelfinavir mesylate is designated as Form I. The present invention also relates to pharmaceutical compositions comprising the crystalline Form I of nelfinavir mesylate and use of said compositions for treatment of HIV-1 infections. The present invention further relates to a process for the preparation of nelfinavir or a salt thereof.
Nelfinavir is chemically, [3S-[2(2S*,3S*),3α,4αß,8αß]]-A/-(1,1-dimethylethyl)decahydro-2-[2-hydroxy-3-[(3-hydroxy-2-methylbenzoyl)amino]-4-(phenylthio)butyl]-3-isoquinoline carboxamide. It is commercially available in the form of its mono-methanesulfonate salt of structural Formula I.
(Formula Removed)
FORMULA I
Nelfinavir belongs to the class of HIV-protease inhibitors indicated for the treatment of HIV infection when antiretroviral combination therapy is warranted. It was originally used in combination with antiretroviral nucleoside analogues for the treatment of HIV-1 in adults, adolescents and children. Nelfinavir is a member of the group of drugs referred to as protease inhibitors (Pls). This class of drug combats viral replication of HIV by blocking HIVs protease protein. This protein or enzyme is used by HIV to break up large viral proteins into smaller particles from which new HIV particles can be formed. Protease inhibitors ensure that these new particles are immature and incapable of infecting new cells, thus inhibiting the HIV replication process.
Several processes have been reported for the preparation of nelfinavir for example, in International (PCT) Publication Nos. WO 95/09843; 98/09951; 98/09952; and 01/29013; and European Patent No. 983,999. All the processes provide amorphous nelfinavir mesylate.
The present inventors have found a new crystalline form of nelfinavir mesylate and have developed a process for preparation thereof. The new crystalline form of nelfinavir mesylate is designated as Form I.
The present inventors have further developed one-pot process for the preparation of nelfinavir or salts thereof.
A first aspect of the present invention provides crystalline Form I of nelfinavir mesylate. The crystalline Form I of nelfinavir mesylate may be characterized by X-ray diffraction having peaks at 20 (°) of about 7.74, 9.54, 10.84, 11.16, 12.00, 12.40, 12.90, 13.42, 13.56, 15.40, 16.54, 17.26, 17.66, 18.14, 18.60, 19.20, 19.60, 20.08, 20.86, 21.82, 22.16, 22.96, 23.46, 23.84, 24.42, 25.04, 25.24, 25.70, 26.08, 26.24, 26.70, 27.08, 27.42, 27.98, 28.20, 28.58, 29.28, 29.40, 30.08, 30.22, 30.78, 31.82, 32.34, 32.76, 32.92, 33.44, 33.62, 34.32, 34.62, 34.72, and 36.12. The crystalline Form I of nelfinavir mesylate may also be characterized by Differential Scanning Calorimetric (DSC) thermogram as depicted in Figure II having characteristic endothermic peak between 118°C and 128°C.
A second aspect of the present invention provides a process for the preparation of crystalline Form I of nelfinavir mesylate wherein the said process comprises of,
a) obtaining a solution of nelfinavir in one or more organic solvents:
b) contacting the solution with methanesulphonic acid; and
c) isolating the crystalline Form I of nelfinavir mesylate by the removal of the solvents.
A solution of nelfinavir was obtained by dissolving nelfinavir in a suitable solvent. Alternatively, a reaction mixture comprising nelfinavir can also be employed. The solution of nelfinavir may be obtained by heating. Heating can be carried out from about 30°C to about reflux temperature of the solvent used, for example from about 50°C to about 100°C for about 10 minutes to about 24 hours, more particularly for about 1-2 hours. The solution of nelfinavir was contacted with methanesulphonic acid. The resultant mixture may be optionally cooled and seeded with crystals of Form I of nelfinavir mesylate. Cooling can be carried out from about 50°C to about 10°C, for example from about 40°C to about 20°C. The crystalline Form I of nelfinavir mesylate may be obtained by removing the solvent(s) by filtration, filtration under vacuum, decantation, centrifugation, distillation and distillation under vacuum. It may be further dried to achieve the desired moisture content. For example, the product may be further dried in a tray drier, dried under vacuum and/or in a Fluid Bed Dryer. The resulting crystalline Form I is pure and stable at normal and accelerated stability conditions.
Nelfinavir used as the starting material in the present process can be prepared according to the process of the present invention or by the methods disclosed in International (PCT) Publication Nos. WO 95/09843; 98/09951; 98/09952; and 01/29013; and European Patent No. 983,999.
The term "obtaining" includes dissolving, slurrying, stirring or a combination thereof.
The term "suitable solvents" includes any solvent or solvent mixture in which nelfinavir can be solubilized. Suitable solvents can be selected from the group comprising alkanols, ketones, nitriles, chlorinated hydrocarbons, polar aprotic solvents, esters, ethers, or mixtures thereof. The alkanol may be selected from the group comprising of methanol, ethanol, n-propanol, isopropanol, butanol or mixtures thereof. The ketone may be selected from the group comprising of acetone, ethyl methyl ketone, methyl isobutyl ketone, diisobutyl ketone or mixtures thereof.
The crystalline Form I of nelfinavir mesylate may be formulated into ordinary dosage forms such as, for example, tablets, capsules, pills, solutions, etc. by conventional methods with conventional pharmaceutical excipients, carriers or diluents.
The crystalline Form I of nelfinavir mesylate can be administered for the treatment of HIV-1 infections in combination with other antiretroviral agents, in a warm-blooded animal. For the purpose of this disclosure, a warm-blooded animal is a member of the animal kingdom possessed of a homeostatic mechanism and includes mammals and birds.
A third aspect of the present invention provides a process for the preparation of nelfinavir or a salt thereof
wherein the said process comprises of,
a) reacting a compound of Formula II or a salt thereof,
(Formula Removed)
FORMULA II
wherein R, and R2 are independently hydrogen or amino protecting group with the provisos that both R, and R2 are not hydrogen or R-, and R2 do not combine together to form a divalent amino protecting group, with 3-t-butylcarboxamide perhydroisoquinoline of Formula III,
(Formula Removed)
FORMULA III
to get a compound of Formula IV,
(Formula Removed)
FORMULA IV
wherein R! and R2 are as described above;
b) deprotecting the compound of Formula IV to get a compound of Formula V;
(Formula Removed)
FORMULA V
c) condensing the compound of Formula V with a compound of Formula VI,
(Formula Removed)
FORMULA VI
wherein R3 represents hydroxy protecting group, to get protected nelfinavir;
d) deprotecting the hydroxy protecting group of protected nelfinavir; and
e) isolating the nelfinavir or a salt thereof from the reaction mixture thereof, wherein all the above steps
are carried out in-situ without isolation of any intermediate.
The above one-pot process for the preparation of nelfinavir or salts thereof involves reacting a compound of Formula II or a salt thereof with 3-t-butylcarboxamide perhydroisoquinoline of Formula III to get a compound of Formula IV; deprotecting the compound of Formula IV to get a compound of Formula V; condensing the compound of Formula V with a compound of Formula VI to get protected nelfinavir; deprotecting the hydroxy protecting group of the protected nelfinavir; and isolating the nelfinavir or a salt thereof from the reaction mixture thereof. The process does not involve isolation of any intermediates thereby reducing the work-up time as well as the cost of production and affords good yield of nelfinavir mesylate.
A solution of (2S,3R)-1,2-epoxy-3-N-(protected)-amino-4-phenylthiobutane of Formula II and 3-t-butylcarboxamide perhydroisoquinoline of Formula III was stirred in a suitable solvent, including, for example alkanols, ketones, polar aprotic solvents, chlorinated hydrocarbons, non-polar aprotic solvents, esters, ethers and mixtures thereof. The solution may be stirred for about 1 hour to about 24 hours at about 30°C to about 100°C and the reaction was monitored for the formation of the compound of Formula IV. After completion of the reaction, an aqueous solution of a suitable deprotecting agent was added to deprotect the protected-amino group in the compound of formula IV to get the compound of formula V. The resulting suspension was heated from about 30°C to reflux temperature for about 1-30 hours after which water and a suitable organic solvent, including, for example chlorinated hydrocarbons, non-polar aprotic solvents, esters, ethers and mixtures thereof were added. The organic layer was separated and treated with a base. To the resultant mixture a solution of 3-O-protected-2-methyl benzoyl chloride (compound of formula VI) in an organic solvent, including, for example chlorinated hydrocarbons, non-polar aprotic solvents, esters or ethers was added at about 5°C to about 30°C and the reaction mixture stirred for about 0.5-1 hour. Water was added to the reaction mixture and the organic layer was separated. The solvent was evaporated under vacuum at about 25°C to about 40°C to obtain O-protected nelfinavir. To the resulting residue a suitable organic solvent, including, for example alkanols, ketones, polar aprotic solvents, chlorinated hydrocarbons, non-polar aprotic solvents, esters, and ethers was
added and the mixture treated with a suitable deprotecting agent to deprotect the O-protected nelfinavir. The pH of the reaction mixture was adjusted to about 7-8 and water was charged. The resulting mass was heated to about 40°C to about 70°C, filtered, washed and dried to obtain nelfinavir free base. Nelfinavir free base may be converted to its salts.
The term "deprotecting agent" refers to those used in the art for removing the protecting groups. Suitable deprotecting agents are known to a person skilled in the art. Examples of deprotecting agents include, but not limited to, inorganic and organic bases such as hydroxides, alkoxides, carbonates, or bicarbonates of alkali and alkaline earth metals, ammonia, triethylamine, dicyclohexylamine amine, diisopropylamine, and the like.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention. For example, the compounds described herein can be formulated into dosage forms that are suitable for administering to patients in need of the compound for treating a medical condition for which the compound is indicated, approved, or otherwise beneficial. Specifically, the Form I of nelfinavir can be formulated with one or more pharmaceutically acceptable excipients, carriers or diluents and/or with one or more active ingredients into a dosage form and administered to treat HIV-1 infections.
Example 1: Preparation of nelfinavir free base
A solution of (2S,3R)-1,2-epoxy-3N-(benzyloxycarbonyl)-amino-4-phenylthiobutane (50 g) and 3-t-butylcarboxamide perhydroisoquinoline (39.9 g) in ethanol (100 ml) was stirred at 40°C for 15 hours and the progress of the reaction was monitored (Thin Layer Chromatography/High Performance Liquid Chromatography). After the completion of reaction, a solution of sodium hydroxide (12.1 g) in water (12.1 ml) was added. The resulting suspension was heated to reflux for 20 hours. Water (250 ml) and dichloromethane (250 ml) were added and the mixture was stirred for 10 minutes and allowed to settle. The lower dichloromethane layer was collected. Triethylamine (42 ml) was added to the dichloromethane layer under stirring. This mixture was added dropwise to a solution of 3-acetoxy-2-methyl benzoyl chloride (32.3 g) in dichloromethane (100 ml) at 5-25°C in 30 minutes. The reaction mixture was stirred for 30 minutes and monitored (Thin Layer Chromatography/High Performance Liquid Chromatography). Water (250 ml) was charged followed by stirring for 10 minutes. This mixture was allowed to settle for 5 minutes and the dichloromethane layer was collected. The solvent was evaporated at 35°C under vacuum. To the resulting paste, ethanol (100 ml) and a solution of sodium hydroxide (12.1 g) in water (12.1 ml) were added and the mixture was stirred for 2 hours and the reaction monitored (Thin Layer Chromatography/High Performance Liquid Chromatography). The pH of the mixture was adjusted to 7.5 by adding a mixture of acetic acid (15 ml) in water (15 ml). Water (750 ml) was charged and the resulting
white mass was heated to 60°C and stirred for 1 hour. The white solid was filtered and slurry washed with water. The solid so obtained was dried in air at 80°C to afford nelfinavir free base. Purity = 80% (by HPLC).
Example 2: Preparation of crystalline Form I of nelfinavir mesylate
Nelfinavir obtained in Example 1 was suspended in acetone (600 ml) and the suspension heated to 55°C. Methane sulphonic acid (14.2 g) was added and the reaction mixture was stirred for 15 minutes at 55°C. Active carbon was charged at 55°C with stirring for 15 minutes followed by filtration through hyflo. The resulting clear filtrate was stirred for 2.0 hours at room temperature and heated to reflux for 1 hour. After this period, heating was stopped and the reaction mixture was allowed to attain a temperature of 40°C, filtered and slurry washed with acetone (50 ml x 2). The solid so obtained was dried under vacuum at 80°C for 24 hours to obtain crystalline Form I of nelfinavir mesylate. Yield = 65 g Purity = 99.5% (by HPLC).

WE CLAIM:
1. Crystalline Form I of nelfinavir mesylate.
2. Crystalline Form I of nelfinavir mesylate having characteristic X-ray diffraction peaks at 2-theta (°)
values of about 7.74, 9.54, 10.84, 11.16, 12.00, 12.40, 12.90, 13.42, 13.56, 15.40, 16.54, 17.26,
17.66, 18.14, 18.60, 19.20, 19.60, 20.08, 20.86, 21.82, 22.16, 22.96, 23.46, 23.84, 24.42, 25.04,
25.24, 25.70, 26.08, 26.24, 26.70, 27.08, 27.42, 27.98, 28.20, 28.58, 29.28, 29.40, 30.08, 30.22,
30.78, 31.82, 32.34, 32.76, 32.92, 33.44, 33.62, 34.32, 34.62, 34.72, and 36.12.
3. Crystalline Form I of nelfinavir mesylate having differential scanning calorimetric endothermic
peak at about 118°C to about 128°C.
4. A process for the preparation of crystalline Form I of nelfinavir mesylate, the process comprising:

a) obtaining a solution of nelfinavir in one or more organic solvents
b) contacting the solution obtained in step a) with methanesulphonic acid
c) isolating the crystalline Form I of nelfinavir mesylate by removal of the solvents.
5. The process according to claim 4, wherein:
i) the organic solvent in step (a) is selected from the group comprising of alkanols, ketones, nitriles, chlorinated hydrocarbons, polar aprotic solvents, esters, ethers or mixtures thereof; ii) removing the solvent in step (c) comprises one or more of filtration, filtration under vacuum, decantation, centrifugation, distillation and distillation under vacuum; and iii) the process comprises additional drying of the product obtained.
6. The process according to claim 4 wherein the crystalline Form I of nelfinavir mesylate has the X-
ray diffraction pattern of Figure 1.
7. A process for the preparation of nelfinavir or a salt thereof, wherein the process comprising:
a) reacting a compound of Formula II or a salt thereof,
FORMULA II (Formula Removed)
FORMULA(Formula Removed)
wherein R, and R2 are independently hydrogen or amino protecting group with a proviso that both R! and R2 are not hydrogen or R! and R2 do not combine together to form a divalent amino protecting group, with 3-t-butylcarboxamide perhydroisoquinoline of Formula III,
to get a compound of Formula IV,
(Formula Removed)
FORMULA IV
wherein RI and R2 are as described above;
b) deprotecting the compound of Formula IV to get a compound of Formula V;
(Formula Removed)
FORMULA V
c) condensing the compound of Formula V with a compound of Formula VI,
(Formula Removed)
FORMULA VI
wherein R3 represents a hydroxy protecting group, to get protected nelfinavir;
d) deprotecting the hydroxy protecting group of the protected nelfinavir; and
e) isolating the nelfinavir or a salt thereof from the reaction mixture thereof, wherein all the above
steps are carried out in-situ without isolation of any intermediates.
The process according to claim 7, wherein:
i) the reaction in step a) is carried out in an organic solvent comprising one or more of alkanols,
ketones, polar aprotic solvents, chlorinated hydrocarbons, non-polar aprotic solvents, esters,
ethers or mixtures thereof;
ii) the condensation in step c) is carried out in the presence of a base; and
iii) the deprotection in steps b) and d) is carried out in the presence of a base.
9. A pharmaceutical composition comprising a therapeutically effective amount of crystalline Form I of nelfinavir mesylate, and one or more pharmaceutically acceptable carriers, excipients or diluents.
10. A method of treating HIV-1 infections in a warm blooded animal, the method comprising providing a dosage form comprising crystalline Form I of nelfinavir mesylate to the warm blooded animal.