Nature Medicine has published EMBRAZE, a randomised, double-blind, placebo-controlled phase 2 trial in 102 adults with overweight or obesity. Every participant received tirzepatide; half also received apitegromab, an antibody that selectively blocks the activation of myostatin.
At week 24 the apitegromab arm had lost about 1.9 kg less lean mass than placebo while total bodyweight loss was similar between groups — reported as retaining roughly 55% of the lean mass otherwise lost. Adverse event rates were broadly balanced, and serious adverse events occurred in one participant in each arm. The work was run with Scholar Rock.
Catalogue note
This is the axis that RGF-17, recombinant GDF-8, and RGF-18, the soluble ActRIIB-Fc decoy, exist to let a laboratory interrogate, and it is unusual to see it sitting in the same protocol as an incretin agonist. Tirzepatide is MET-02. All three are reagents for laboratory research, supplied Research Use Only, and we publish no protocols for administration.
Source: Pratley RE and colleagues, Nature Medicine, July 2026. PubMed 42260100.