HexemBio has publicly launched with a $10.4 million seed round led by Draper Associates, with participation from SOSV, Seraphim, and other investors. The Berkeley and New York-based company is developing what it describes as the first blood stem cell rejuvenation therapy, built around a platform called the Synthetic Human Yolk Sac.
Rather than editing or chemically reprogramming aged haematopoietic stem cells, the technology temporarily places a patient's own cells into a recreated version of the developmental environment where blood stem cells first emerge in the embryo, then returns them via standard IV infusion.
Haematopoietic stem cells sit deep in the bone marrow and give rise to every blood and immune cell in the human body. Their decline with age is linked to weakened immunity, chronic inflammation, and increased susceptibility to conditions including blood cancers and neurodegeneration.
Previous attempts to reverse this decline have typically involved transcription-factor reprogramming, cytokine treatments, or gene editing, approaches that can push cells into unstable states or carry safety risks HexemBio says its method sidesteps.
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The Synthetic Human Yolk Sac recreates the microenvironment that generates the body's first blood stem cells during early embryonic development. Foundational work supporting the platform was published in Nature in February 2024, by a team led by Mo Ebrahimkhani at the University of Pittsburgh, with Samira Kiani and Joshua Hislop among the authors. All three are now co-founders of HexemBio.
The company's lead clinical programme targets bone marrow transplant in patients with blood cancers including acute myeloid leukaemia and acute lymphoblastic leukaemia.
HexemBio received FDA Orphan Drug Designation for this indication in July 2025 and completed its FDA Pre-IND meeting in January 2026. First-in-human trials are targeted for 2027.
Regulatory strategy focuses on bone marrow transplant outcomes because ageing itself is not currently recognised as a regulatory indication, a constraint that has shaped how several longevity-adjacent biotechs have structured their early clinical programmes.
The founding team spans MIT, UC Berkeley, Harvard, and Y Combinator. Gabriel Levesque Tremblay, a former YC founder and UC Berkeley postdoc, serves as CEO. Samira Kiani, a Presidential Early Career Award recipient who trained at MIT, is CTO.
Mo Ebrahimkhani, the inventor of the underlying technology and a pioneer in synthetic developmental biology, is CSO. Joshua Hislop, whose doctoral work contributed directly to the Nature publication, leads the company's AI platform, which includes proprietary tools called YolkGPT and YolkScore. Samet Yildirim, a former YC founder with drug development experience at Boehringer Ingelheim, is chief business officer.
The advisory board includes Robert S. Langer, Institute Professor at MIT and co-founder of Moderna, who called the approach “fundamentally different from transcription-factor reprogramming or gene editing' and said the early data were ‘extremely compelling.”
Further advisors include Peter Barton Hutt, former chief counsel of the FDA and current Moderna board member; Joanne Kurtzberg of Duke University, one of the leading bone marrow transplant clinicians in the US; David Harris, founder of the first public cord blood bank in the United States; Felipe Sierra, former director of the Division of Aging Biology at the NIH; Jens Nielsen, CEO of the BioInnovation Institute; and George Church, professor of genetics at Harvard Medical School and co-founder of Colossal Biosciences.
Seed funding will be used to complete IND-enabling studies and GMP manufacturing ahead of the 2027 trial target.