[Clinical phase I and phase II study on a sustained release formulation of leuprorelin acetate (TAP-144-SR), an LH-RH agonist, in patients with prostatic carcinoma. Collaborative++ Studies on Prostatic Carcinoma by the Study Group for TAP-144-SR]

Abstract

TAP-144-SR is a sustained release formulation of an LH-RH agonist, leuprorelin acetate (TAP-144), that has been newly developed in Japan. As a phase I study, a single subcutaneous dose of TAP-144-SR was given to 15 patients with prostatic cancer to investigate the safety, endocrinological effects, and serum levels of the drug. The patients were divided into four groups according to the dosage levels of 1.88 mg, 3.75mg, 7.5 mg and 15 mg. No serious side effects were noted in any of the patients treated with any dose. No patients exhibited signs of a local reaction at the site of injection. In two patients transient exacerbation of clinical symptoms owing to "flare up" was observed. Serum testosterone levels decreased to the castration level (less than 1.0 ng/ml) in all of the patients, although the time required to attain the castration level tended to be longer in the patients receiving 1.88 mg. Serum TAP-144 levels increased on the first day and gradually decreased thereafter. In the groups of patients that received 3.75 mg or more of TAP-144-SR, TAP-144 was detected in the serum up to 4 weeks after administration. Based on the results of the phase I study, 3.75 mg and 7.5 mg of TAP-144-SR were selected as the doses for the phase II study. The phase II study was carried out as a multi-center open trial. Patients with stage B-D prostatic cancer received subcutaneously either 3.75 mg (3.75 mg group) or 7.5 mg (7.5 mg group) of TAP-144-SR once every 4 weeks for a total of 3 doses over a period of 12 weeks. TAP-144-SR 3.75 mg was administered to 51 patients and 7.5 mg to 50 patients. Both of these doses were adequate to suppress serum LH and FSH levels. Serum testosterone was decreased to the castration level within 22 days after the first dose, and this suppression was maintained throughout the treatment period. Clinical response rate (CR + PR) was 21% in the 3.75 mg group and 22-24% in the 7.5 mg group according to the Criteria for Evaluating the Direct Response to Chemotherapy in Solid Carcinomas and NPCP criteria. The response rate by the criteria of Japanese Prostatic Cancer Study Group was 51% in the 3.75 mg group and 62% in the 7.5 mg group. Adverse reactions were noted in 26% of patients in the 3.75 mg group and 34% in the 7.5 mg group.(ABSTRACT TRUNCATED AT 400 WORDS)