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

Abstract

PurposeThis 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. MethodsA 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. FindingsAll 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. ImplicationsLeuprolide 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.