Sustained-release composition comprising lactic acid-glycolic acid copolymer and process for producing the same

Disclosed herein is a sustained-release composition which contains a physiologically active substance of a LH-RH derivative in a high content, and a lactic acid-glycolic acid polymer which even when gelatin is not included, suppresses its initial excessive release and, thus can achieve a stable release rate over about one month. The polymer having a ratio of weight average molecular weight to number average molecular weight of about 1.40 to 1.90, a weight average molecular weight of about 8,000 to 15,000 and a molar ratio of lactic acid to glycolic acid of from up to but not including 100:0 to about 40:60. The polymer is prepared by adding water to an organic solvent containing a lactic acid-glycolic acid polymer having a weight average molecular weight of about 5,000 to 15,000 at a ratio of about 10 to about 45 (ratio by volume) relative to 100 of the organic solvent. The composition is useful for preventing or treating prostate cancer, prostatomegaly, endometriosis, hysteromyoma, metrofibroma, precocious puberty, dysmenorrheal and breast cancer.