Onset and Maintenance of Testosterone Suppression in 4 Pivotal Trials of Subcutaneously Administered Leuprolide Acetate Formulated with Biodegradable Polymer Delivery System

November 2018 Vol 9, NO 11
Julie Prettyman, RN, BSN, CCRC
AdvanceMed Research, Lawrenceville, NJ
John A. McLane, PhD
TOLMAR, Inc., Fort Collins, CO
Stuart N. Atkinson, MB, ChB
Tolmar Pharmaceuticals, Inc.
Buffalo Grove, IL
Allison Tyler, RN, BSN, OCN, CCRP
TOLMAR Pharmaceuticals, Inc., Lincolnshire, IL; Cleveland Clinic, Cleveland, OH
Deborah M. Boldt-Houle, PhD
Tolmar Pharmaceuticals, Inc.
Buffalo Grove, IL

Background: In prostate cancer therapy, achieving and maintaining effective testosterone (T) suppression to the level attained with surgical castration is the cornerstone of androgen deprivation therapy (ADT). Subcutaneously administered leuprolide acetate (SC-LA) formulated with a biodegradable polymer delivery system has demonstrated efficacy in suppressing T levels to achieve and maintain medical castration (T <50 ng/dL) in patients with advanced prostate cancer (PCa). However, <20 ng/dL may be a more appropriate standard for T castration level compared with <50 ng/dL. Increasing evidence suggests that reaching and sustaining the lowest T level possible is desirable during ADT and correlates with disease-specific survival. Therefore, lowering the T level as much as possible should be the goal of ADT in patients with metastatic PCa.

Objective: Data were pooled from 4 pivotal trials to determine the onset and maintenance of T levels at or lower than castrate levels with SC-LA treatment.

Methods: Eugonadal PCa patients received either 7.5- (6 doses), 22.5-, 30-, or 45-mg (2 doses each) injections of SC-LA lasting 1, 3, 4, or 6 months, respectively, in 4 open-label, fixed-dose, pivotal trials. T level was measured 2 to 4 times on day 0 and once on days 1, 2, 3, and 7 and every week until the next dose through the end of the studies; the 45-mg group had an additional measurement taken on day 2. Target T levels were 50, 20, and 10 ng/dL. The onset of T suppression and the proportion of time serum T remained below the target levels were calculated for each patient by extrapolating the time point when T first crossed the target. Proportion of time below target was calculated as total time T remained below target divided by time after target first achieved to end of study.

Results: In the pooled population (N = 437), median onset of T levels ≤50, ≤20, and ≤10 ng/dL were 21, 28, and 35 days, respectively. Once target T was achieved, the mean proportion of time that patients maintained T suppression below each target level was 100%, 94% to 99%, and 66% to 85% for T ≤50, 20, and 10 ng/dL, respectively.

Conclusions: SC-LA achieved effective onset of T ≤50, ≤20, and ≤10 ng/dL at 3, 4, and 5 weeks, respectively. SC-LA maintained consistently low T levels, with over 66% and 94% of the treatment period remaining below 10 and 20 ng/dL, and 100% of the treatment period remaining below 50 ng/dL. This T suppression profile may have implications for improved patient survival and extended time to disease progression.

Disclosures: Sponsor: Tolmar, Inc. Previously presented at ASCO Genitourinary Cancer Symposium 2018.

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Last modified: April 22, 2021

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