A six-month, open-label study assessing a new formulation of leuprolide 7.5 mg for suppression of testosterone in patients with prostate cancer

Abstract

Objective: The safety, efficacy, and pharmacokinetics of monthly subcutaneous injections of a new leuprolide acetate (LA) depot formulation were investigated in patients with advanced prostate cancer. Methods: The 2-part, 6-month (168-day), open-label, multicenter study enrolled male patients diagnosed with adenocarcinoma of the prostate (Jewett stage C or D). LA-2500 7.5-mg (a new subcutaneous depot formulation containing 7.5 mg of LA) injections were administered at monthly (28-day) intervals. The primary efficacy parameter was total serum testosterone level. A breakthrough response was defined as a single testosterone measurement >50 ng/dL after achieving castration testosterone levels. Testosterone was isolated from sera by alumina column chromatography and measured by radioimmunoassay (RIA). LA was purified by solid-phase extraction and high-performance liquid chromatography and was then quantitated by RIA. Results: One hundred seventeen of the 120 enrolled patients completed the 6-month study. Three patients withdrew for reasons not related to treatment. LA had a mean (SD) maximal concentration of 26.3 (12.6) ng/mL at 4.66 (1.44) hours and was detected for a mean of 37 days (range, 28–49 days). By day 28, 94.1% (112/119) of the patients achieved medical castration (serum testosterone ≤50 ng/dL). By day 42, 100.0% (118/118) of the patients remaining in the study had serum testosterone levels ≤50 ng/dL and 97.5% (115/118) had levels ≤20 ng/dL. At study completion, the mean (SD) serum testosterone level was 6.12 (4.3) ng/dL (range, 3.0–27.0 ng/dL). No breakthrough or acute-on-chronic responses were reported throughout the study. From baseline to month 6, mean (SD) luteinizing hormone level decreased from 8.0 (7.3) mIU/mL to 0.09(0.1) mIU/mL, and mean (SD) prostate-specific antigen level decreased from 32.9 (86.3) ng/mL to 3.2 (12.0) ng/mL. Treatment-related adverse events were reported by 74.2% (89/120) of patients, the most common being hot flashes (56.7%). Conclusion: This 6-month, open-label, noncontrolled study showed LA-2500 7.5-mg depot was well tolerated and maintained testosterone suppression ( ≤50 ng/dL) in the patients completing the study without any testosterone breakthrough responses.