Efficacy and safety of once-weekly somatrogon in adults with growth hormone deficiency: a randomized phase 3 study

This study assessed the efficacy and safety of once-weekly somatrogon, a long-acting growth hormone, in adults with growth hormone deficiency (aGHD). A phase 3 randomized, double-blind, placebo-controlled study consisted of a 26-week double-blind period (Period 1), a 26-week open-label extension (OLE; Period 2), and a multi-year OLE (Period 3). Patients were randomized 2:1 to somatrogon or placebo in Period 1, with dosing adjusted for gender, age, and estrogen therapy. All patients received somatrogon in Periods 2 and 3. Primary endpoint was change in trunk fat mass (FM; baseline-Week 26). Secondary endpoints included changes in total FM, lean body mass (LBM), percentage change in trunk FM, and trunk FM. Changes in percent trunk FM relative to total trunk mass (FM + LBM), trunk LBM, and appendicular skeletal muscle mass were also evaluated in a post-hoc supplemental analysis. Safety assessments included adverse events (AEs) and laboratory evaluations. Of 389 patients screened, 202 were randomized, and 198 received treatment (somatrogon:133; placebo:65). Mean IGF-I SDS normalized following somatrogon initiation. There was no significant difference between somatrogon and placebo in change in trunk FM from baseline to Week 26 (-0.37 vs 0.03 kg; p=0.0821; primary endpoint) or in total FM. However, somatrogon significantly improved LBM, trunk FM as a percentage of total FM and the three supplemental endpoints. AE incidence was similar between groups, with most being mild to moderate in severity. Somatrogon significantly improved several body composition parameters and was well tolerated overall in adults with GHD. NCT01909479; registration date: 25/07/2013