George Church

George Church earned his PhD in biochemistry and molecular biology at Harvard in 1984, working under Nobel laureate Walter Gilbert on mobile genetic elements, and joined the Harvard Medical School faculty as an assistant professor in 1986 [1]. By his own team's count, published on Colossal Biosciences' site, he has published 673 papers, secured 159 patents, and helped found more than 50 companies over his career [3].

In 2018 Church co-founded Rejuvenate Bio with the explicit goal of using gene therapy to reverse aging, initially in dogs, as a translational step toward human aging interventions [2]. The company gave mice three genes associated with longevity, either alone or in combination: FGF21, soluble TGF-beta receptor 2, and alpha-Klotho [2]. Rejuvenate Bio reported that mice overexpressing these genes showed improved health and lifespan measures in earlier work, and by 2018 the company said it had compelling early evidence the combination could reverse multiple age-related conditions at once in further mouse experiments [2]. The company has since run trials of similar gene therapy in dogs with the stated long-term aim of a human aging therapy, though as of the most recent public reporting available it has not published a completed human trial [2].

Church is also a founding advisor to Colossal Biosciences, the company attempting to use genome-editing tools to recreate traits of the extinct woolly mammoth in Asian elephant embryos, a project that intersects with his longevity work through shared genome-engineering and stem-cell technology [3][4]. In March 2024 NPR reported a stem-cell milestone in Colossal's mammoth program, and the New York Times had covered the company's 2021 launch as "a wild mission" combining de-extinction ambitions with genetic engineering tools originally developed for medical and agricultural use [4].

Separately, Church has collaborated with transhumanist entrepreneur James Clement on the Supercentenarian Research Study, sequencing the genomes of people who lived past 110 in search of protective genetic variants associated with exceptional longevity [1]. Since 2023 he has also served on the scientific and ethical advisory commission of the Enhanced Games, an event permitting athletes to use performance-enhancing drugs under medical supervision, a role that has drawn criticism from parts of the sports-science and bioethics community for lending a Harvard geneticist's credibility to a doping-permissive competition [1].

Church's approach across his career has been to found or advise a very large number of companies simultaneously rather than concentrate on a single therapeutic bet, which is itself a point critics raise: with dozens of active company affiliations spanning genome sequencing, de-extinction, aging reversal, and performance enhancement, no single venture receives the kind of sustained, singular scrutiny that a more narrowly focused biotech founder would face. Rejuvenate Bio's own public claims have moved from mouse data to dog trials over roughly six years without a published completed human trial, a pace that is not unusual for gene therapy development but that means the core claim, that the FGF21/TGF-beta receptor/Klotho combination reverses aging, remains unconfirmed in humans as of 2026.

The plain takeaway: Church is one of the most prolific founders in biotech history, and Rejuvenate Bio's mouse and dog data on multi-gene therapy for aging are real published early-stage results, but the leap from those results to a human anti-aging therapy has not yet been made, and his simultaneous involvement in de-extinction and doping-permissive sports raises separate questions about how his name and credibility are deployed commercially.