Activin receptor type IIB (ActRIIB) (ActRIIB)

Activin receptor type IIB (ActRIIB) is a high-affinity cell surface receptor for several ligands in the transforming growth factor-beta (TGF-beta) superfamily, most notably myostatin (GDF-8) and activins. It is primarily expressed on the surface of skeletal muscle cells, where it plays a critical role as a negative regulator of muscle mass. Upon ligand binding, ActRIIB forms a complex with type I receptors (such as ALK4 or ALK5), triggering a SMAD-dependent signaling cascade that inhibits protein synthesis and promotes muscle protein degradation. Due to its central role in muscle homeostasis, ActRIIB has become a major therapeutic target for treating muscle-wasting conditions such as Duchenne muscular dystrophy, sarcopenia, and spinal muscular atrophy. Drugs targeting this pathway, including monoclonal antibodies like bimagrumab and apitegromab, aim to block ligand-receptor interactions to enhance muscle growth and physical function. The term "undisclosed" in the target name likely refers to its status in specific early-stage drug development pipelines where the protein identity was initially withheld by the developer.

Other names

ACVR2BActivin A receptor type IIBMyostatin receptorSkeletal muscle cell surface receptor

Inhibition of myostatin and activin signaling to promote muscle growth and prevent atrophy.