34-OR: The Effect of Combined Activin A and Myostatin Blockade on Body Composition—A Phase 1 Trial

Introduction: Preclinical data suggest myostatin and activin A are important negative regulators of muscle mass. Trevogrumab (a monoclonal antibody [mAb]) binds and blocks myostatin signalling, while garetosmab (a mAb) binds and blocks activin A, AB and AC signalling. Here, the effects of administering trevogrumab and garetosmab, alone or in combination, on body composition in healthy participants was assessed. Methods: This Phase 1, double-blind, placebo-controlled study randomized healthy males and postmenopausal females to single-dose or multiple-dose parts of the study. For single-dose, females received: trevogrumab 6 mg/kg (n=6); garetosmab 10 mg/kg (n=6); combination trevogrumab 6 mg/kg and garetosmab (1 mg/kg, n=6; 3 mg/kg, n=6; 10 mg/kg, n=12); or placebo (PBO; n=12). For multiple‑dose, females received: garetosmab 10 mg/kg every 4 weeks (Q4W; n=6) or PBO (n=2); combination trevogrumab 6 mg/kg and garetosmab 10 mg/kg every 2 weeks (n=6) or PBO (n=4). In the multiple dose part, males received garetosmab 10 mg/kg Q4W (n=8) or PBO (n=8). Results: Thigh muscle volume (TMV) increased from baseline 7.7% with trevogrumab 6 mg/kg + garetosmab 10 mg/kg (nominal P