[Studies on hormone-polymer composites in urological field--their application in prostatic cancer therapy]

Our studies on the application of hormone-polymer composites in urological field are discussed in this review. We first studied the modes of in vivo and in vitro release of testosterone from vinyl polymer-testosterone composites prepared by radiation-induced polymerization. It was ascertained by our group that in vivo and in vitro release of testosterone from biodegradable copolypeptide -testosterone composites as well as vinyl polymer composites was well controlled. Using this system, we were successful in preparing a testicular prosthesis, which was made of vinyl polymer-testosterone composites and was ascertained to release testosterone constantly for a long period in the dose range of clinical usage. We also applied this sustained release drug delivery system to the method of administration of an LH x RH agonist, which was one of the best therapeutic drugs for androgen dependent prostatic cancer. Sustained release of the LH x RH agonist in the dose range of clinical usage over a period of several months from copolymer-LH x RH agonist composites was confirmed in both male rats and in prostatic cancer patients. Prostatic cancer cells contain a major secretion protein (alpha-protein or estramustine-binding protein) and estramustine has a high affinity for alpha-protein. Therefore, we examined the effect of an estramustine-microsphere containing anticancer drugs, namely, the missile therapy for prostatic cancer. The missile therapy should open the way to specific and selective chemotherapy for prostatic cancer.