ai3Bio Raises $48M to Target Autoimmune T Cells

ai3Bio has launched with a $48M Series A to develop therapies that directly eliminate disease-causing Th17 cells. Founding investors UPMC Enterprises and Ziff Capital Partners led the financing, with Cockrell Interests and Tanis Ventures participating.

The Watertown, Massachusetts biotechnology company is advancing 2 preclinical platforms, STARx and T Deplete, around the same cellular thesis. Rather than only interrupting inflammatory signals after they are produced, ai3Bio wants to remove selected T cells associated with autoimmune disease while preserving the rest of the immune system. The company plans to use the capital for IND-enabling work toward an initial patient trial in 2027.

What ai3Bio Announced

The $48M financing is ai3Bio's launch round and was announced on September 29, 2026. The company describes UPMC Enterprises and Ziff Capital Partners as founding investors. It did not disclose a valuation, individual check sizes, or a prior financing history under the ai3Bio name.

ai3Bio is led by CEO Steven Altschuler, scientific co-founder Jonathan Kagan, CTO Michael Lyman, and Chief Financial and Business Officer Nick Seaver. Fabian Tenenbaum, executive vice president at UPMC Enterprises, chairs the board. Kagan is also the Marian R. Neutra Professor of Pediatrics at Harvard Medical School and director of basic research and the Shwachman Chair in Gastroenterology at Boston Children's Hospital.

The company says its name reflects advanced immunology, autoimmunity, and artificial intelligence. The AI component is part of a discovery platform used to study diseased tissue and identify a cellular marker shared across the T-cell populations the company wants to target.

The Cellular Thesis Behind the Round

Th17 cells are a type of helper T cell involved in immune defense and inflammatory signaling. Research has connected dysregulated Th17 biology with autoimmune conditions including psoriasis, inflammatory bowel disease, rheumatoid arthritis, and multiple sclerosis, although the role of these cells varies by disease and patient. A 2025 U.S. prevalence study estimated that about 15M Americans had at least 1 of 105 autoimmune diseases between 2011 and 2022.

Many established autoimmune therapies inhibit cytokines such as IL-17, IL-23, or TNF, while several newer approaches deplete B cells. ai3Bio is testing whether selected pathogenic T cells can be removed directly. The company says its computational work identified CD161 as a marker shared by malfunctioning Th17 and related inflammatory T-cell populations, giving both platforms a target for selective depletion.

That target is scientifically plausible, but the therapeutic conclusion remains to be established in people. CD161 appears across multiple T-cell subsets, and preclinical selectivity does not automatically translate into a safe clinical window. ai3Bio's next work is therefore less about defending the elegance of the target and more about proving dose control, tissue reach, durability, and preservation of healthy immune function.

How STARx and T Deplete Work

STARx stands for Selective T cell Apoptosis Therapy. It uses an antibody-guided lipid nanoparticle to deliver engineered mRNA into CD161-positive T cells. The payload is designed to activate the cGAS-STING pathway inside the targeted cell and trigger apoptosis, a programmed cell-death process intended to clear the cell without the inflammatory damage associated with other forms of cell death.

T Deplete uses a different mechanism. Its antibody binds to the targeted cells and recruits natural killer cells to eliminate them through antibody-dependent cellular cytotoxicity, an immune mechanism already used by multiple approved antibody medicines. Running 2 platforms against the same cellular thesis gives ai3Bio more than one development path, but it also creates separate manufacturing, safety, and clinical-program demands.

The company reports that its lipid-nanoparticle technology removed disease-causing Th17 cells in tests using blood samples from patients with autoimmune disease. It also reports that T Deplete showed efficacy in a non-human-primate autoimmune model. Both claims are preclinical and company-reported; ai3Bio has not yet disclosed human safety or efficacy data.

Why the Investor Mix Matters

UPMC Enterprises is the innovation, commercialization, and venture arm of the UPMC health system. Its involvement fits a company that will eventually need translational science, clinical-development discipline, and a route from academic immunology into patient testing. Ziff Capital Partners supplied more than capital: Altschuler and Seaver have direct ties to the firm and bring company-building and financial experience into ai3Bio's operating team.

Cockrell Interests and Tanis Ventures broaden the financing syndicate, while the scientific advisory board adds experience across immunology and therapeutic development. It includes Alnylam founding CEO John Maraganore and immunologists Vijay Kuchroo, Ruslan Medzhitov, Alexander Rudensky, Arlene Sharpe, Dario Vignali, and Greg Delgoffe. The concentration of scientific credibility raises the standard for how clearly ai3Bio will need to separate mechanistic promise from clinical proof.

What the $48M Changes

The financing gives ai3Bio room to advance STARx and T Deplete through IND-enabling studies and prepare for an initial patient trial targeted for 2027. That work typically includes manufacturing development, toxicology, dose selection, regulatory preparation, and the assays needed to show whether the intended immune cells were depleted without unacceptable effects elsewhere.

The broader wager is that autoimmune treatment can move from managing recurring inflammatory signals toward a more durable reset of selected immune-cell populations. ai3Bio has assembled capital, leadership, and 2 technical routes around that wager. The clinical program now has to determine whether the selectivity that makes the science compelling can survive contact with the immune system it is trying to edit.