The invention relates to a stable amorphous form of (5-Fluoro-2-methyl-3-quinolin-2-ylmethyl-indol-l-yl)-acetic acid and its use in the treatment of conditions mediated by the action of PGD2 at the CRTH2 receptor.本發明有關於一種(5-氟-2-甲基-3-喹啉-2-基甲基-吲哚-1-基)-乙酸的穩定非晶形式以及其在治療由PGD2在CRTH2受體上作用所媒介的病症上的用途。