Rhapsogen is a biotechnology company developing precision biologics for IgG-mediated autoimmune diseases. Founded in early 2025 and headquartered in Cambridge, MA, the company was founded by leaders in antibody effector biology and autoimmunity—Professors Jeff Ravetch (Rockefeller University) and Eric Sundberg (Emory University)—and seeded by Catalio Capital Management.
Rhapsogen is advancing a best-in-class enzymatic approach that rapidly and selectively abrogates IgG Fc effector function while preserving Fab-mediated antigen binding, thereby maintaining protective humoral immunity. This differentiated mechanism enables broad suppression of pathogenic IgG activity without global immunosuppression and has the potential to redefine the treatment paradigm for IgG-driven autoimmune diseases. In parallel, second-generation programs targeting selective neutralization of pathogenic autoantibodies are in early development.

Rhapsogen, Inc.

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