
Third Rock debuts immunometabolism startup Rheos with $60M launch round
Third Rock is pushing one of its stealthy startups into the limelight this morning, with $60 million in fresh capital and a platform tech that operates in the increasingly popular field of immunometabolism.
The startup, called Rheos Medicines, has a drug discovery tech that’s already churned out two leads for the company that are both moving into preclinical development.

Rheos, founded last summer, is digging into the new field of immunometabolism, which basically tries to understand — and later harness — how a cell’s metabolism affects disease progression.
“We want to understand which cells are driving which diseases, and which metabolic pathways are being dysregulated by cells,” said Abbie Celniker, a Third Rock partner who’s currently serving as the startup’s interim CEO.
The company hopes to learn how to “tune” the metabolic pathways to bring patients with immune system-related diseases “back into balance.”
The company has recruited Larry Turka, an expert in the field of regulatory T cell biology, from his post at Harvard Medical School and Massachusetts General Hospital, to serve as the startup’s CSO.
“I’ve been seeing patients with autoimmune disease my whole professional life, and the opportunity to bring drugs into the clinic to help patients with tremendous unmet need was too good to pass up,” Turka tells me.
Turka said Rheos is building a catalogue of comparisons between immune cells in different states, focusing on the metabolic differences of those cell types.
“If we understand the difference between an immune cell that causes inflammation versus an immune cell that suppresses inflammation, then we can use that data to develop products,” Turka says.
Rheos is calling its catalogue the Immune Cell Encyclopedia (ICE), and the platform has already delivered two targets to pursue. Celniker said the company isn’t yet disclosing details of the programs, but noted the company is focusing on therapeutics that target CD4 and CD8 T cell subtypes, which are involved in autoimmune diseases like inflammatory bowel disease, psoriasis, vitiligo, and could have applications in immuno-oncology.

Other than pursuing its own drug programs, Rheos will also use its tech platform to better define subsets of autoimmune disease patients, creating biomarkers that will help create more tailored drugs for individual patients.
“Cellular physiology is something we understand pretty well, and now we’re learning to modulate individuals’ metabolic pathways instead of the one-size-fits-all approach that most drugs for autoimmune diseases take now,” Celniker said. “It’s a much more sophisticated approach.”
Celniker said the company just recruited Ryan Cohlhepp, a former VP at Takeda, to lead Rheos’ R&D. Now the company is on the hunt for a more permanent CEO.
Abbie Celniker. Third Rock Ventures