The present invention related to novel crystalline forms of methyl [(2S)-1-{(6S)-6-[5-(9,9-difluoro-7-{2-[(1R,3S,4S)-2-{(2S)-2- [(methoxycarbonyl)amino]-3-methylbutanoyl}-2-azabicyclo [2.2.1]hept-3-yl]-1H-benzimidazol-6-yl}-9H-fluoren-2-yl)-1H- imidazol-2-yl]-5-azaspiro[2.4] hept-5-yl}-3-methyl-1-oxobutan-2-yl]carbamate compound of formula (I) and their process for the preparation thereof.