The Berkeley biotech is adopting a Nature-published strategy that mimics the embryonic environment where blood stem cells first originate, rather than chemically or genetically reprogramming aged cells. Its primary program targets bone marrow transplant in blood cancers and has received FDA Orphan Drug Designation.
HexemBio has officially launched with a $10.4 million seed round led by Draper Associates, with SOSV, Seraphim, and other investors participating. The company, based in Berkeley and New York, is developing the first blood stem cell rejuvenation therapy, utilizing a platform called the Synthetic Human Yolk Sac.
Instead of editing or chemically reprogramming aged hematopoietic stem cells, the technology places a patient’s own cells in a recreated developmental environment where blood stem cells first form in the embryo, then reintroduces them through a standard IV infusion.
Hematopoietic stem cells are located deep in the bone marrow and are responsible for producing all blood and immune cells in the body. Their age-related decline is associated with weakened immunity, chronic inflammation, and higher susceptibility to blood cancers and neurodegenerative diseases.
Past efforts to reverse this decline typically involved transcription-factor reprogramming, cytokine treatments, or gene editing, which could make cells unstable or pose safety risks that HexemBio claims its technique avoids.
The Synthetic Human Yolk Sac replicates the microenvironment that generates the first blood stem cells during early embryonic development. Foundational work supporting this 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 leading clinical program focuses on bone marrow transplant for patients with blood cancers like acute myeloid leukemia and acute lymphoblastic leukemia.
HexemBio received FDA Orphan Drug Designation for this application in July 2025 and had its FDA Pre-IND meeting in January 2026. Initial human trials are planned for 2027.
Their regulatory strategy centers on bone marrow transplant outcomes due to ageing not being recognized as a regulatory indication, influencing the structure of early clinical programs in some longevity-related biotechs.
The founding team includes members from MIT, UC Berkeley, Harvard, and Y Combinator. Gabriel Levesque Tremblay, a former YC founder and UC Berkeley postdoc, is the CEO. Samira Kiani, a Presidential Early Career Award recipient trained at MIT, is the CTO.
Mo Ebrahimkhani, the inventor of the core technology and a leader in synthetic developmental biology, serves as CSO. Joshua Hislop, whose doctoral work significantly contributed to the Nature publication, leads the company’s AI platform, which includes proprietary tools named YolkGPT and YolkScore. Samet Yildirim, a former YC founder with experience in drug development at Boehringer Ingelheim, is the chief business officer.
The advisory board features Robert S. Langer, an MIT Institute Professor and Moderna co-founder, who described the approach as “fundamentally different from transcription-factor reprogramming or gene editing” and noted that the early data is “extremely compelling.”
Additional advisors include Peter Barton Hutt, former FDA chief counsel and current Moderna board member; Joanne Kurtzberg of Duke University, a prominent bone marrow transplant clinician 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, a professor of genetics at Harvard Medical School and co-founder of Colossal Biosciences.
Seed funding will be allocated to complete IND-enabling studies and GMP manufacturing in preparation for the 2027 trial goal.