Clinical phase III study on TAP-144-SR, an LH-RH agonist depot formulation, in patients with prostatic cancer

A randomized controlled phase III clinical trial comparing TAP-144-SR (TAP) and diethylstilbestrol diphosphate was conducted for patients with prostatic cancer. Patients with Stage B, C, or D disease, who were previously untreated, were enrolled. TAP-144-SR 3.75 mg was administered subcutaneously at 4-week intervals for 12 weeks (a total of 3 injections) in the TAP-144-SR group, while 100 mg of diethylstilbestrol diphosphate was administered orally three times a day (before meals) for 12 weeks in the control group. A total of 141 patients were enrolled using a centralized telephone registration system. Four of these patients were ineligible, and there were 3 drop-outs who never received drugs because they withdrew their consents to participate in the trial. These 7 were excluded from the evaluation, and as a result, 134 patients (66 in the TAP group and 68 in the control group) were evaluable in safety and efficacy. Between the two groups, there were no significant differences in patient characteristics, except the age distribution. Clinical response rates (CR+PR) in evaluable patients according to the criteria of Japanese Prostatic Cancer Study Group were 54.5% in the TAP group and 47.1% in the control group. In addition, the rates according to the criteria for Evaluating the Direct Response to Chemotherapy in Solid Carcinomas and NPCP criteria were 7.6% in the TAP group and 8.8% in the control group and 18.2% in the TAP group and 20.6% in the control group, respectively. Using any of the three criteria, there were no significant differences in response rate between the two groups. The incidence of side effects was 64.1% in the TAP group and 95.4% in the control group; the incidence being significantly higher in the control group (p less than 0.001; chi 2-test). Therefore, the overall safety was significantly greater in the TAP group than in the control group (p less than 0.001; chi 2-test). On the basis of the efficacy and safety the clinical usefulness rate of TAP-144-SR was significantly higher than that of diethylstilbestrol diphosphate (p = 0.038; U-test). In conclusion, TAP-144-SR was confirmed to be more useful than diethylstilbestrol diphosphate as a standard drug for hormonal therapy of prostatic cancer.