A New Sustained-release, 3-Month Leuprolide Acetate Formulation Achieves and Maintains Castrate Concentrations of Testosterone in Patients With Prostate Cancer.

PURPOSE: This clinical trial investigated the effectiveness, pharmacokinetic properties, and safety profile of leuprolide acetate 22.5-mg depot, a new 3-month leuprolide depot formulation, as androgen deprivation therapy for patients with prostate cancer.
METHODS: A Phase III, open-label, multicenter study design for patients with prostate cancer, with patient inclusion assessed by the investigative site as patient's appropriate for androgen deprivation therapy. Patients received 2 separate intramuscular injections of leuprolide acetate 22.5-mg depot for a 3-month depot interval of therapeutic effect. Plasma testosterone concentrations were determined throughout the study. The primary efficacy analysis was the percentage of patients who achieve and maintain castrate testosterone levels (≤50 ng/mL) from days 28-168. Secondary end points included luteinizing hormone, follicle-stimulating hormone, prostate-specific antigen, and safety assessments. A pharmacokinetic study was also conducted in a subset of 30 patients.
FINDINGS: All 163 patients enrolled in the study received at least 1 dose of study drug; 162 of them were fully evaluable and 151 completed the study. Castrate levels of testosterone were achieved and maintained from days 28-168 in 96.8% (95% CI, 92.5%-98.7%) of patients. Five patients presented with sporadic testosterone levels >50 ng/dL. By day 28, of the 161 patients, 150 (99.4%) had achieved castrate levels, and 127 (78.9%) had achieved testosterone concentrations ≤20 ng/dL. At study end, 149 of 151 patients (98.7%) patients achieved castrate testosterone levels, with 142 of 151 (94.0%) having testosterone levels ≤20 ng/dL. At study end, mean luteinizing hormone and follicle-stimulating hormone concentrations had decreased from baseline to below the lower limit of quantitation and below baseline levels, respectively, whereas mean serum prostate-specific antigen was reduced by 94.7% from baseline. Most patients (>96%) had no change in their World Health Organization/Eastern Cooperative Oncology Group score, whereby 84.0% of patients had a baseline score of 0. Bone pain, urinary pain, and urinary symptoms were infrequent and remained so throughout the study. After administration, leuprolide concentrations increased rapidly. The peak was followed by a decline up to day 28, maintaining sustained drug levels until the following dose on day 84. The most common related treatment-emergent adverse events, detected in >5% of patients, were hot flushes, fatigue, and injection site pain reported by 77.3%, 9.8%, and 9.2% of patients, respectively. IMPLICATIONS: Leuprolide acetate 22.5-mg depot was effective in achieving and maintaining testosterone suppression. Safety and tolerability profiles were consistent with established profiles of androgen deprivation therapy. Clinical Trials.gov identifier: NCT01415960.