Company lands $17.2m to preserve, regenerate and manipulate the thymus to combat immune diseases and extend healthy lifespan.
US biotech Tolerance Bio has launched with $17.2 million in seed financing to develop thymus-based therapies for immune-mediated diseases. The company focuses on preserving, regenerating and manipulating the thymus, an organ central to immune tolerance.
Philadelphia-based Tolerance Bio is developing an allogeneic cell therapy platform based on induced pluripotent stem cells (iPSCs) as well as pharmacological treatments aimed at immune diseases. By focusing on the thymus, the company addresses the core of immune regulation, seeking to preserve thymic function and restore it where it has declined or been lost.
Tolerance describes the thymus as “the school for T cells” due to its role in educating our immune cells, which defend the body against infections and cancers while preventing autoimmunity. However, the thymus naturally atrophies after the early years of life, increasing susceptibility to immune disorders and mortality.

Thymic dysfunction is linked to various immune diseases due to age-related decline, congenital defects, or damage from medical interventions like surgery, chemotherapy, and infection. Tolerance Bio aims to reverse these effects by developing artificial thymuses from stem cells, targeting disease-specific treatments such as thymic organoids. The company also seeks to delay thymic involution with drugs to prevent both natural and accelerated thymic decline. Restoring thymic function could not only combat immune diseases but also extend healthy lifespan by improving the body’s immune response.
“Defeating immune diseases has been the lifelong quest of this exceptional team we have assembled, with patients and their families always front and center for us,” said Dr Francisco Leon, co-founder and CEO of Tolerance Bio. “We intend to rapidly advance and validate our pioneering concepts in a rare disease and then assess proof-of-concept in multiple major indications, advancing these novel therapeutics to target immune disease at its core.”
Tolerance Bio joins a number of companies seeking to harness the power of the thymus against aging and disease, including ARPA-backed Thymmune, Vidaregen and Thymox. In 2015, Dr Greg Fahy, renowned aging researcher and CSO of Intervene Immune, commenced the first clinical trial to explore if thymus regeneration could reverse aspects of human aging, with results showing participants’ epigenetic age was “significantly decreased” by the treatment.
Tolerance Bio’s scientific approach is rooted in iPSC technologies initially developed at the University of Colorado and the University of Florida, led by Dr Holger Russ.
“After pioneering the generation of bioengineered thymuses from iPSC in vitro and in vivo, I am very excited for the opportunity to advance this technology to benefit patients,” said Russ.
The oversubscribed financing was led by Columbus Venture Partners, with participation from Criteria Bio Ventures, Sessa Capital, BioAdvance, Ben Franklin Technology Partners, and others. The funds will enable Tolerance Bio to advance its pioneering therapies toward clinical trials.
“With Tolerance Bio, we not only have the prospect of preventing and treating immune disease but also possibly extending longevity, a tremendously exciting opportunity,” said Damia Tormo, Managing Partner of Columbus Venture Partners.


