Zag Bio emerged from stealth with $80 million in disclosed funding to advance bifunctional antibodies that traffic tolerizing antigens to the thymus and promote regulatory T cell (Treg) development. Backers include big biopharma names—AbbVie, Regeneron and Sanofi—which also participated in the company’s Series A and seed financings. Zag’s platform aims to induce central tolerance by presenting antigens in the thymic milieu to retrain the immune repertoire—a strategy positioned for autoimmune disease indications. The company intends to progress lead assets toward IND‑enabling studies while expanding the antibody engineering toolbox for thymus targeting. The launch highlights renewed investor interest in tolerance‑inducing biologics and thymic biology as a therapeutic axis. For readers: thymus‑directed approaches seek durable immune resetting by altering T cell selection rather than peripheral immunosuppression.