Disclosed is a method for stabilizing a pharmaceutically active bi-cyclic compound of formula (I):comprising the step of: admixing the same with a polyol and/or a fatty acid ester other than glyceride and a composition obtained by the method. In addition a soft gelatin capsule formulation of the compound of formula (I) obtained by incorporating the compound in a soft gelatin capsule shell comprising gelatin and a polyol plasticizer.
