The present invention discloses new salts of (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6- dihydro[l.2.4]-triazo!o[4,3-a]pyrazin-7(8H)-yl]-l-(2,4,5-trifluorophenyl)butan-2-amine i.e. gentisate. adipate and trifluoro acetic acid salts. The invention also describes the new crystalline and amorphous forms of (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[l,2,4]-triazolo[4.3-a]pyrazin-7(8H)-yl]-l-(2.4.5-trifluorophenyl)butan-2-amine gentisate. The present invention also discloses novel crystalline salt form of (2R)-4-oxo-4-[3-(trifluoromethyl)-5.6-dihydro[l.2.4]-triazolo[4,3-a]pyrazin-7(8H)-yl]-i-(2.4.5-trifluorophenyl)butan-2-arnine hydrochloride and novel crystalline and amorphous salt forms of besylate and process for their preparation and isolation.
