The invention relates to a crystalline form of (S)-2-(8-((5-chloropyrimidin-2-yl)(methyl)amino)-2-fluoro-6,7,8,9-tetrahydro-5H-pyrido[3,2-b]indol-5-yl)acetic acid, processes for the preparation thereof, pharmaceutical compositions comprising said crystalline forms, pharmaceutical compositions prepared from such crystalline forms, and their use as a medicament, especially as CRTH2receptor modulators.本發明係關於一種(S)-2-(8-((5-氯嘧啶-2-基)(甲基)胺基)-2-氟-6,7,8,9-四氫-5H-吡啶并[3,2-b]吲哚-5-基)乙酸之結晶型式、其製備方法、包含該結晶型式之醫藥組合物、自此結晶型式製備之醫藥組合物及其等作為藥物,尤其是作為CRTH2受體調節劑之用途。