IMNM is a rare, severe, inflammatory myopathy characterized by necrosis of skeletal muscle fibers. On biopsy, IMNM is associated with prominent complement activation and diffuse deposition of C5b-9 membrane attack complex (MAC) with minimal or no inflammatory cell infiltrate. Three disease subtypes have been identified based on the presence of autoantibodies: anti-SRP (signal recognition particle) myopathy; anti-HMGCR (hydroxy-3-methylglutaryl-CoaA reductase) myopathy; and seronegative IMNM. A recent study established a protective role for C3-deficiency in an IMNM passive transfer model. Ra Pharma is developing zilucoplan, a convenient, subcutaneously self-administered macrocyclic peptide that is designed to bind and inhibit the cleavage of complement component 5 (C5). Zilucoplan is currently in Phase 2 development for IMNM, as well as in Phase 3 development for acetylcholine receptor-positive generalized myasthenia gravis (gMG).