DESC:Field of invention
This present invention relates to darunavir n-propanol solvate and process for preparation thereof. Further, invention relates to pharmaceutical compositions comprising darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients and process for preparation thereof.

Background of invention
The protease inhibitors are a class of antiviral drugs that are widely used to treat HIV/AIDS and hepatitis caused by hepatitis C virus. Protease inhibitors prevent viral replication by selectively binding to viral proteases (e.g. HIV-1 protease) and blocking proteolytic cleavage of protein precursors that are necessary for the production of infectious viral particles.

Darunavir is a new HIV protease inhibitor and approved by the FDA under the name of Prezista®. Prezista® is administered in combination with a low-dose of ritonavir and other active anti-HIV drugs.

Figure - 1
Prezista® is presented with darunavir ethanolate as a film coated tablets. Darunavir ethanolate (as described in Figure-1) is in white to off-white hygroscopic powder. It is chemically known as [(1S,2R)-3-[[(4-aminophenyl)sulfonyl](2-methylpropyl)-amino]-2-hydroxy-1-(phenylmethyl)propyl] carbamic acid (3R,3aS,6aR)-hexahydrofuro-[2,3-b]furan-3-yl ester monoethanolate.
U.S.Pat. Nos. 7,700,645 and 8,518,987 refer to ethanolate and hydrate solvate of darunavir respectively.

The approved Product Information for PREZISTA®disclosesthat during storage of darunavir ethanolate tablets, partial conversion from ethanolate solvate to hydrate solvate might occur.No test data is provided in such Product Information to substantiate this occurrence, whether in whole or in part.
Nevertheless, accepting the assertions in the above made by the authors of the patent documents and Product Information as true, we have prepared. The present invention provides a pharmaceutical composition of darunavir n-propanol solvate which is stable throughout its shelf life and is clinically bioequivalent under FDA standards to the marketed compositions of darunavir.
Further, darunavir n-propanol solvate of invention is more stable, cost-effective, and viable at plant scale.
The present invention also providesa pharmaceutical composition comprising darunavir n-propanol solvate which isstable throughout shelf life. Further, these compositions are clinically bioequivalent under FDA standards to the marketed dosage forms of darunavir, PREZISTA®. The present compositions are further free of any solvate forms of darunavir as depicted in U.S. Pat. Nos.7,700,645, U.S. Pat. Nos. 8,518,987 or PCT Application no. WO/2011/083287 A1.

Summary of invention
This invention provides a new solvate form of darunavir i.e. darunavir n-propanol solvate. The invention additionally provides a method for preparing darunavir n-propanol solvate, which is viable at plant scale and also helpful for achieving higher stablility. Further, present invention provides pharmaceutical compositions of darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients and a process for preparation thereof.

Brief Description of the drawings
Figure 2 depicts TG thermogram of darunavir n-propanol solvate.
Figure 3 depicts DSC pattern of darunavir n-propanol solvate.
Figure 4 depicts 1H- NMR pattern of darunavir n-propanol solvate.
Figure 5 depicts powder X-ray diffraction pattern of darunavir n-propanol solvate.
Figure 6 depicts TG thermogram of darunavir n-propanol solvate.

Detailed description
The present invention provides solvate form of darunavir i.e. darunavir n-propanol solvate and process for preparation thereof. Further, invention relates to pharmaceutical compositions comprising darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients and process for preparation thereof.
In one aspect of the invention, the process for preparation of novel solvate of darunavir comprising the step of: a) reacting darunavir with n-propanol; b) heating the reaction mass and gradually cooling; and c) isolating darunavir n-propanol solvate.
In the present invention,darunavir used as a starting material is obtained by the processes known in the art.
The mixture typically is heated to a temperature of about 50°C to about 100°C preferably 70°C to 80°C for a period of time of about 10 minutes to about 1 hour or longer. The resulting solution is gradually cooled to about 25°C to about 30°C i.e. ambient temperature, for minimum three hours and stirred for an hour at ambient temperature and darunavir n-propanol solvate precipitates and can be collected by filtration. The crystalline product generally is dried for about 1 hour or more, preferably in a vacuum, at about 20°C to about 60°C. The product so formed is highly stable and crystalline.
Molar equivalents of n-propanol employed for this invention varies with respect to darunavir equivalents.
The present invention has checked the content of n-propanol in darunavir n-propanol solvate and it shows 7.9% to 11.9%. The isolation of the crystalline solid is carried out by the conventional techniques known in the prior art such as filtration, concentration, and evaporation etc.
According to another aspect of the present invention, there is provided a solid darunavir n-propanol solvate by the following properties:
i) a thermogravimetric analysis curve (TGA) obtained after heating the sample from 20°C to 300°C at a scan rate of 10°C/minute shows in FIG. 2 & 6;
ii) a differential scanning calorimetric (DSC) thermogram as depicted in FIG. 3;
iii) a H-NMR spectrogram as depicted in FIG. 4;
iv) a powder X-ray diffraction pattern as described in FIG. 5.

Analytical Methods
(1) 1H-NMR
The 1H-NMR spectrums was recorded in CDCl3 using Bruker, 400 MHZ NMR Spectrometer.
(2) Powder X-ray Diffraction
Using a PANalytical X’Pert powder diffraction meter, the powder x-ray diffraction pattern was measured at room temperature using a Cu Ka filled tube (45 kV 40 mA) as the x-ray source. Data collection was done in 2theta continuous scan mode in the range of 3.5° to 40°.
(3) Thermogravimetric analysis
Thermogravimetric analysis was performed using a Pyris 1 TGA PERKIN ELMER measurement unit. 2-5 mg samples were placed in open Platinum pans and heated from 20 °C to 300 °C in a dry nitrogen atmosphere at a heating rate of 10 °C/min.
(4) Differential Scanning Calorimetry
Differential Scanning Calorimetry was performed using a Diamond DSC PERKIN ELMER differential instrument. 2-3 mg samples were placed in crimped aluminum pans and heated from 50 °C to 280 °C in a dry nitrogen atmosphere at a heating rate of 10 °C/minute.
(5) Gas Chromatography (GC)
Gas Chromatography studies were performed using a PERKIN ELMER CLARUS – 600, 680, 500 & auto system XL with headspace sampler and Shimadzu GC-2010.
(6) Melting Point
Melting point was measured using a LABIndia- MR-VIS measuring unit.
The present invention will now be further illustrated by reference to the following examples, which do not limit the scope of the invention any way.

Example 1
In a round bottom flask, 1500 ml of n-propanol was added followed by 100 gms of darunavir. The reaction temperature was raised to 70°C to 80°C and was cooled to room temperature. This reaction mass was stirred. After stirring, the resultant solid was filtered and washed with 100ml n-propanol twice. The solid was dried at 50°C under reduced pressure. Yield: 97gms. The melting point of darunavir n-propanol solvate was 99.7°C to 102.5°C and the content of n-propanol measured by GC was 9.72 (%). The TG thermogram, DSC pattern, 1H- NMR pattern and powdered X-ray diffractogram of the obtained product as described in Fig. 2, 3, 4, 5 and 6 respectively.
Example 2
In a round bottom flask, ethyl acetate (3780 ml), methanol (420 ml), triethyl amine (67.5 ml) and nitro-darunavir (280 gm) were charged. The reaction mass was warmed to dissolve the solid, and then cooled the reaction mass to 25 to 30°C and was hydrogenated the reaction by using 10% Palladium on carbon (28 gm; 50% wet) and water (210 ml) in autoclave at 5-6Kg/cm2 hydrogen pressure. After completion of the reaction, the reaction mass was filtered to remove catalyst and solvent was distilled out under reduced pressure and the concentrated mass was stripped out with n-propanol (2X840 ml). The n-propanol (2520 ml) was added into the reaction mass. The reaction mass was warmed to dissolve the solid. Gradually it was cooled to room temperature and filtered under reduced pressure. The product was dried under reduced pressure. The solid weighted 255 gms., Melting point:101.7 to102.2°C, n-propanol: 9.9%.
According to another aspect of the present invention, pharmaceutical compositions of darunavir n-propanol solvate comprise but are not limited to suspensions, solutions, emulsions, ointments, liniments, lotions, creams, gels, suppositories, transdermal patches, powders and osmotic pumps, tablets (single layered tablets, multilayered tablets, mini tablets, bioadhesive tablets, caplets, matrix tablets, tablet within a tablet, mucoadhesive tablets, modified release tablets, pulsatile release tablets, and timed release tablets), pellets, beads, granules, sustained release formulations, capsules, microcapsules, tablets in capsules, microspheres, matrix formulations, microencapsulation.
In another embodiment, pharmaceutical compositions of invention are in the form of tablet comprising 1 mg to 1600 mg of darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients. More preferably the composition comprises 800 mg, 600 mg, 300 mg, 150 mg or 75 mg of darunavir n-propanol solvate.
In another embodiment, a pharmaceutical composition comprising darunavir n-propanol solvateand one or more pharmaceutically acceptable excipients.
In another embodiment, a pharmaceutical composition comprising darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients, wherein Darunavir n-propanol solvate having a powder X-ray diffraction pattern as described in FIG. 5.
The term “pharmaceutically acceptable excipients” used in the pharmaceutical compositions of invention comprise but not limited to diluents, binders, pH stabilizing agents, disintegrants, surfactants, glidants and lubricants known in the art.
The amount of excipient employed will depend upon how much active agent is to be used. One excipient(s) can perform more than one function.
In yet another embodiment, the pharmaceutical composition may optionally be coated wherein the coating can be film coating, sugar coating, extended release coating, enteric coating, partial enteric coating or leaky enteric coating, bioadhesive coating and other coatings known in the art. These coatings may help the pharmaceutical composition to release the drug at and for the required time. The coating comprises a hydrophilic or hydrophobic substance(s) or the combinations thereof.
In another embodiment, pharmaceutical compositions of inventions can be used for the treating of HIV infection or preventing AIDS.
,CLAIMS:1. Darunavir n-propanol solvate.
2. The darunavir n-propanol solvate according to claim 1, having a thermogravimetric analysis curve (TGA) obtained after heating the sample from 20°C to 300°C. at a scan rate of 10°C/minute as shown in FIG. 2.
3. The darunavir n-propanol solvate according to claim 1, having a differential scanning calorimetric (DSC) thermogram as depicted in FIG. 3;
4. The darunavir n-propanol solvate according to claim 1, having 1H-NMR spectrogram as depicted in FIG. 4.
5. The darunavir n-propanol solvate according to claim 1, having a powder X-ray diffraction pattern as described in FIG. 5.
6. A process for the preparation of darunavir n-propanol solvate according to claim 1, comprising the steps of: a) reacting darunavir with n-propanol; b) heating the reaction mass and gradually cooling; and c) isolating the darunavir n-propanol solvate.
7. A process for the preparation of darunavir n-propanol solvate according to claim 2, wherein the heating temperature ranges from about 50°C to about 100°C.
8. A process for the preparation of darunavir n-propanol solvate according to claim 2, wherein the cooling temperature ranges from about 25°C to about 30°C.
9. A pharmaceutical composition comprising darunavir n-propanol solvate and one or more pharmaceutically acceptable excipients.
10. The pharmaceutical composition according to Claim 9, wherein the darunavir n-propanol solvate has a powder X-ray diffraction pattern as depicted in FIG. 5.