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Source: Asco Online, #1307 - Publication Year: 2000

Abarelix-Depot (A-D) Versus Leuprolide Acetate (L) Plus Bicalutamide [Casodex (C)], for Prostate Cancer: Results of a Multi-Institutional, Randomized, Phase III Study in 255 Patients

John Trachtenberg, Marc Gittelman, Chris Steidle, Winston Barzell, William Friedel, Dennis Pessis, Nick Fotheringham, Marilyn Campion, Marc B. Garnick, for the Abarelix-Depot Study Group, Univ of Toronto, Toronto, Canada; South Florida Medical Research, Aventura, FL; North Indiana Urology, Fort Wayne, IN; Urology Treatment Ctr, Sarasota, FL; San Diego Urology Ctr, La Mesa, CA; Affiliated Urologists, Chicago, IL; Amgen, Inc, Thousand Oaks, CA; Praecis Pharmaceuticals, Inc, Cambridge, MA.

Introduction and Objectives: Abarelix-Depot (A-D), a GnRH antagonist, has shown promising endocrinologic and clinical results in phase I/II trials in prostate cancer patients (pts), including absence of testosterone (T) surge and clinical flare. We therefore compared A-D 100 mg and leuprolide acetate (L) 7.5 mg plus bicalutamide (C), 50 mg (L plus C) in a multicenter phase III study in 255 prostate cancer pts who were candidates for initial hormonal therapy.

Methods: Using 2:1 allocation, 170 pts were randomized to A-D and 85 pts to L plus C. A-D or L was given by IM injection on days (D) 1, 29, and 57; A-D pts received an additional injection on D15. C was given orally at 50 mg/day throughout the study. Serum levels of T, dihydrotestosterone, and gonadotropins were assessed throughout. Efficacy measures included avoidance of T surge (T notł10% of baseline); rapidity of achieving medical castration in the first week of treatment (TŁ50 ng/dL on D8); and achievement and maintenance of castration from D 29 through 85 (T > 50 ng/dL on two consecutive readings at least 2 weeks apart counted as failures). Safety events and detailed laboratory values were monitored throughout.

Results: 168 A-D patients and 83 L plus C were evaluable. Median age was 73 years and 80% of pts were Caucasian. A-D was significantly more effective in avoidance of T surge (p<0.001) and rapidity of achieving medical castration (p ><0.001). A-D and L plus C achieved and maintained medical castration in > 90% of patients. Both leuprolide plus bicalutamide and Abarelix-Depot were well tolerated. {see table}

Conclusions: In this phase III study, Abarelix-Depot, a GnRH antagonist, achieved medical castration more rapidly than leuprolide plus bicalutamide, without any evidence of the initial testosterone surge characteristic of GnRH superagonists. Greater than 90% of patients on this study achieved and maintained medical castration through 12 weeks.


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