Zag Bio Emerges with $80M Series A Funding for Novel Thymus-Targeted Autoimmune Therapies

Zag Bio, a Cambridge, Massachusetts-based startup, has burst onto the biotech scene with an $80 million series A financing round, backed by pharmaceutical giants AbbVie, Regeneron, and Sanofi. The company is pioneering a unique approach to treating autoimmune diseases by targeting the thymus, a critical organ in the immune system.

Innovative Platform Draws Big Pharma Interest

Led by T1D Fund and Polaris Partners, the funding round attracted significant attention from major players in the pharmaceutical industry. Zag Bio's thymus-targeting platform sets it apart in the burgeoning field of regulatory T-cell (Treg) therapies, an area that has gained prominence following the 2025 Nobel Prize in Physiology or Medicine awarded to three immunologists for their work on Tregs.

Jason Cole, the newly appointed CEO of Zag Bio, explained the company's distinctive approach: "The name Zag Bio shows that we are intentionally moving in a new direction to treat autoimmunity by targeting the natural mechanisms in the thymus. When others in the autoimmune space are zigging, we are zagging."

Thymus-Targeted Medicines: A New Frontier

Zag Bio's platform aims to develop antibodies that deliver antigens to restore central immune tolerance in patients with various autoimmune diseases. The company's initial focus is on Type 1 diabetes, with plans to advance a candidate into phase 1 clinical trials next year.

The thymus-targeted approach engages the body's natural mechanism for T-cell tolerance, expanding antigen-specific Tregs while depleting antigen-specific T effector cells. These thymic Tregs then migrate to diseased tissues, offering protection and potentially resetting the immune system.

Alan Crane, partner at Polaris and co-founder and chairman of Zag Bio, highlighted the company's potential: "Zag Bio is trailblazing an unprecedented therapeutic pathway for medicines to target the thymus, and this positions the company to be an innovator in autoimmune disease treatment."

The Race for Treg Therapies Intensifies

Zag Bio's emergence comes at a time of heightened interest in Treg therapies across the pharmaceutical industry. With over 200 clinical trials currently underway, companies are racing to bring Treg-based treatments to market. Orca Bio currently leads the pack, with an FDA decision expected in April for its blood disease candidate, Orca-T.

The field has seen significant investment and collaboration in recent years. In a similar financing arrangement last year, Eli Lilly, Johnson & Johnson, and Pfizer invested in TRex Bio's $84 million series B round. Two years ago, AstraZeneca partnered with Quell Therapeutics in an $85 million deal to collaborate on Treg candidates, including one for Type 1 diabetes.

As Zag Bio joins the ranks of well-funded Treg therapy developers, the pharmaceutical industry eagerly anticipates the potential of these innovative approaches to transform the treatment landscape for autoimmune diseases.