Stage: Preclinical
Indication:Diseases of Complement Dysregulation
Therapeutic Modality: Novel small protein
Mechanism of Action: Inhibitor of Complement Factor 5 (C5)

The Role of the Complement System in Disease

The complement system plays a central role in innate immunity as well as shaping adaptive immune response. Dysregulation of this pathway has been implicated in the pathogenesis of a growing number of diseases, making it an attractive target for therapeutic interventions.


RLYB116 is an innovative antibody mimetic with small molecular size designed to produce rapid, complete, and sustained inhibition of C5. Specifically, RLYB116 is a fusion protein with specificity for C5 and albumin and is suitable for subcutaneous administration. The Affibody® domain of RLYB116 binds with high affinity to C5, thereby inhibiting terminal complement activation, while the Albumod™ technology, including the albumin-binding domain (ABD), binds to serum albumin thereby extending the plasma half-life of the protein.

Rallybiois investigating RLYB116 for the treatment of patients with severe and rare diseases of complement dysregulation.

Rallybio acquired RLYB116 from Swedish Orphan Biovitrum (Sobi™). RLYB116 was designed by Affibody AB in collaboration with Sobi.