Pharmacodynamic equivalence of a decapeptyl 3-month SR formulation with the 28-day SR formulation in patients with advanced prostate cancer

Aims: The objective of the study was to assess the pharmacodynamic equivalence of LHRH analogue triptorelin 3-month and 28-day SR formulations. Methods: Patients with documented locally advanced or metastatic prostate cancer were randomized to receive one injection of the 3-month formulation ( n = 63) or three injections at 28-day intervals of the 28-day formulation ( n = 68). Group-chemical castration rates defined as the percentage of patients reaching a testosterone plasma level less than or equal to 0.5 ng/ml were compared at D84 ( i. e., 3 x 28 days). Testosterone, LH and triptorelin plasma profiles, and change from baseline in plasma PSA were assessed over 3 months ( from baseline to D91). Results: Chemical castration rates were 98 and 96% in the 3-month and 28-day formulation groups, respectively, with confidence interval (two-sided 94.2% CI) of [ - 8.1%; 9.6%]. Median times to reach chemical castration were 18.8 and 18.5 days ( p = 0.86, log rank), respectively. Ratios for mean peak plasma levels and AUC(91) of the two formulations for both testosterone and LH fell within the [0.80; 1.25] equivalence interval. Mean PSA decreases from baseline at D91 were 91.0 and 91.7%, respectively ( p = 0.73). Conclusion: Treatments with the two triptorelin formulations over 3 months are pharmacologically equivalent. Copyright (C) 2004 S. Karger AG, Basel.