Zag Bio

About Zag Bio

Zag Bio, Inc. is a biotechnology company based in Cambridge, Massachusetts, that is developing therapies for autoimmune diseases by targeting the thymus to induce central immune tolerance. The company was incubated by Polaris Partners in 2022 and publicly launched in October 2025 with $80 million in financing. The Series A round was co-led by Polaris Partners and the T1D Fund, with participation from AbbVie Ventures, Lightspeed Ventures, Sanofi Ventures, and others.

The company's scientific foundation is inspired by the work of co-founder Dr. Diane Mathis, a Professor of Immunobiology at Harvard Medical School, whose research has been pivotal in the field of immunologic tolerance. Other co-founders include Chief Scientific Officer John Kulman, PhD, a seasoned drug developer; Jo Viney, PhD, a biotech entrepreneur; and Alan Crane, an entrepreneur partner at Polaris Partners who serves as Zag Bio's chairman. The company appointed biotech industry veteran Jason F. Cole, J.D., as its Chief Executive Officer. Cole was previously the CEO of SalioGen Therapeutics and held leadership roles at bluebird bio.

Zag Bio's core technology involves designing thymus-targeting bifunctional antibodies to deliver specific self-antigens directly to the thymus. This process harnesses the body's natural mechanism for T cell tolerance, expanding antigen-specific regulatory T cells (Tregs) while depleting effector T cells (Teff) that cause autoimmune attacks. These stabilized thymic Tregs then migrate to diseased tissues to provide long-lasting protective effects, effectively creating an immune reset. The company's lead program, ZAG-101, is a bifunctional antibody that delivers pancreatic beta cell antigens to the thymus. It is being developed to prevent or delay the onset of Type 1 diabetes by protecting insulin-producing beta cells from destruction. Zag Bio is advancing ZAG-101 toward clinical development, with plans to initiate clinical trials in late 2026. The company is also leveraging its modular platform to develop a pipeline of therapies for other autoimmune diseases.