CYR241

CYR241 is an engineered proteolytic enzyme designed to degrade immunoglobulin G (IgG) antibodies. It is a next-generation variant of the IgG-degrading endopeptidase (IdeS) originally derived from *Streptococcus pyogenes*. Developed by Cyrus Biotechnology, CYR241 has been optimized for reduced immunogenicity and extended half-life compared to wild-type IdeS. The drug is intended for the treatment of IgG-mediated autoimmune diseases, where pathogenic IgG antibodies drive disease pathology. Unlike wild-type IdeS, which elicits strong anti-drug antibody (ADA) responses after dosing and loses efficacy upon redosing, CYR241 demonstrates potent activity even after multiple doses and does not induce detectable ADA responses in preclinical rabbit models. This improved profile is achieved through glycosylation optimization and sequence reengineering to minimize MHC binding and immune activation. The drug can be titrated for different levels of IgG reduction and shows rapid, sustained depletion of serum IgG with potential for convenient subcutaneous administration in chronic autoimmune indications such as immune thrombocytopenia (ITP) and generalized myasthenia gravis (gMG)[1][2][3][7][8].