Compound of formula I are antagonists of the PGD2 receptor, CRTH2, and as such are useful in the treatment and/or prevention of CRTH2-mediated diseases such as asthma in combination with a second active ingredient such as a leukotriene antagonist.화학식 (I)의 화합물은 PGD2 수용체인 CRTH2의 길항제이고, 따라서 CRTH2-매개 질환 예를 들면 천식의 치료 및/또는 예방에 있어서 유용하다.<;화학식 I>;