Pharmaceutical manipulation of leuprorelin acetate to improve clinical performance

Leuprorelin acetate, a highly potent luteinizing hormone releasing hormone agonist, was originally launched in the USA to be administered once daily by self-injection for the treatment of metastatic prostatic cancer. A once-monthly intramuscularly or subcutaneously injectable depot form of leuprorelin acetate has, subsequently, been developed. Biodegradable copoly(DL-lactic acid/glycolic acid) was chosen as the release-controlling polymer and the microcapsules containing leuprorelin acetate were prepared by an in-water drying method. Results of studies in rats showed that a copolymer with a molecular weight of 14,000 and a lactic acid/glycolic acid ratio of 75/25 had the most satisfactory releasing properties. Microcapsules given once monthly reduced serum testosterone levels in rats, dogs and man. In clinical studies, the depot preparation effectively reduced the dose of leuprorelin acetate required to up to one-eighth of that needed when injected daily. A sophisticated manufacturing system has now been developed and a very reliable controlled-release product is now available that has many advantages.