Head-to-head pharmacokinetic and pharmacodynamic comparison of subcutaneous versus intramuscular leuprorelin acetate formulations in male patients.

Abstract

e589 Background: Leuprolide acetate (LA) is the standard-of-care luteinizing hormone-releasing hormone (LHRH) agonist used to suppress serum testosterone (T) in the treatment of advanced prostate cancer. There are currently two LA formulations available: a controlled-release implant injected subcutaneously (SC) or a microsphere intra-muscular (IM) injection. The study compared the pharmacokinetics/pharmacodynamics of both formulations at the same one-month dose. Methods: Thirty-two healthy men were randomized to receive a single 7.5 mg injection of SC-LA (n = 16) or IM-LA (n = 16) in this phase 1, open-label, parallel-group study. Serum LA, T, and luteinizing hormone (LH) were assessed. Results: The initial surge of LA was higher for IM-LA than SC-LA (Cmax 27±4.9 vs. 19±8.0 ng/mL, respectively), with a shorter tmax (1.0±0.4 vs. 2.1±0.8 hrs). Mean serum LA remained above the level of quantification (LOQ, 50 pg/mL) through Day 49 for SC-LA, whereas for IM-LA, mean serum LA dropped below the LOQ after Day 28. Median LH concentration remained low at Day 56 in the SC-LA group, whereas LH levels began to rise after Day 35 in the IM-LA group. Consequently, serum T began to increase by Day 42 in the IM-LA group. By Day 56, 13 SC-LA subjects maintained serum T levels ≤ 50 ng/dL vs. 0 in the IM-LA group. Both SC-LA and IM-LA were well tolerated, however SC-LA subjects experienced more mild injection site disorders compared to IM-LA. Conclusions: The initial surge of LA was higher for IM-LA than SC-LA (Cmax 27±4.9 vs. 19±8.0 ng/mL, respectively), with a shorter tmax (1.0±0.4 vs. 2.1±0.8 hrs). Mean serum LA remained above the level of quantification (LOQ, 50 pg/mL) through Day 49 for SC-LA, whereas for IM-LA, mean serum LA dropped below the LOQ after Day 28. Median LH concentration remained low at Day 56 in the SC-LA group, whereas LH levels began to rise after Day 35 in the IM-LA group. Consequently, serum T began to increase by Day 42 in the IM-LA group. By Day 56, 13 SC-LA subjects maintained serum T levels ≤ 50 ng/dL vs. 0 in the IM-LA group. Both SC-LA and IM-LA were well tolerated, however SC-LA subjects experienced more mild injection site disorders compared to IM-LA.