Zag Bio launches with $80M to reprogram the immune system against autoimmune diseases

Zag Bio has emerged from stealth with $80M in funding to develop bifunctional antibodies that deliver antigens to the thymus, aiming to retrain the immune system and treat autoimmune diseases.

Why it matters: Autoimmune diseases affect millions and often lack precise, durable treatments. Zag Bio’s approach could create a new class of therapies that prevent the immune system from attacking healthy cells, without the risks of broader immune suppression.

Backstory: Inspired by a research paper detailing the thymus’s role in immune tolerance, co-founder and CSO John Kulman saw potential for targeting the thymus to induce immune tolerance. That insight sparked a collaboration with biotech veterans and led to the creation of Zag Bio, incubated by Polaris Partners in 2022.

Big picture: Zag’s strategy parallels the growing focus on regulatory T cells (Tregs), which won a Nobel prize for their role in immune regulation. By delivering “tolerizing” antigens directly to the thymus, Zag aims to bypass the complexity of cell therapy and use the body’s own systems to prevent autoimmune responses.

Zoom in: Zag Bio´s lead program, ZAG-101, targets Type 1 diabetes. ZAG-101 functions by targeting beta cell antigens to the thymus to halt immune attack and restore insulin production.