Stamulumab
Muscle Growth & Body CompositionAlso known as: MYO-029, Anti-Myostatin Antibody
Mechanism
Stamulumab was the first anti-myostatin antibody tested in humans, developed by Wyeth (now Pfizer) for muscular dystrophy. While it demonstrated proof-of-concept that myostatin blockade was safe in humans, it showed disappointing efficacy — no significant muscle strength or function improvements — leading to its discontinuation. It paved the way for more potent successors.
Technical detail
Stamulumab (MYO-029) is a recombinant human IgG1 monoclonal antibody that neutralizes myostatin (GDF-8) by binding circulating myostatin and preventing its interaction with ActRIIB. A Phase 2 trial in Becker muscular dystrophy, facioscapulohumeral dystrophy, and limb-girdle muscular dystrophy demonstrated safety and tolerability but failed to show significant improvements in muscle strength or function over 6 months. The lack of efficacy was attributed to insufficient target engagement and/or compensatory upregulation of other TGF-β ligands (activin A, GDF-11) that signal through the same receptor. Development was discontinued.