David Sinclair (@davidasinclair)

For twenty years, "reversing aging" meant a conference slide and a mouse study, and then on 9 June 2026, a company put a partial-reprogramming therapy into a living person for the first time, so here is the race, ranked by closeness to a dosed human: 1. ER-100 (@lifebiosciences). A virus carries OSK, three of the four Yamanaka factors, into the retina, and eight weeks of doxycycline switch them on, winding a cell's age markers backward without erasing what the cell is. Same factors restored sight in old mouse eyes in 2020, @davidasinclair's lab. Phase 1, 18 people, glaucoma and optic-nerve stroke. Safety only, no efficacy yet. 2. NewLimit (@brian_armstrong). Not yet in anyone. In lab-grown human liver, its candidate pushed old cells toward a younger gene pattern, no damage at high doses. Company-reported. Trial guided 2027. 3. TRN-001 (@turn_bio). Skin, still in a dish. Rolled back human skin cells' aging signature by a decade. Company-reported. Cleared FDA pre-IND, hasn't dosed. 4. SB000 (@ShiftBioscience). Flips one gene instead of all four. A preprint reports it matched or beat the full set on aging clocks, without switching on the pluripotency that makes reprogramming risky. It won't say which gene, which drew doubt. @RetroBio_ is dosing people, but with an autophagy drug, not reprogramming. @altos_labs raised $3 billion and has nobody dosed. Nobody has reversed aging in a person. The fourth Yamanaka factor is a cancer gene. Switch all four on in a mouse and leave them on, and it's dead inside four days, but leave that fourth one out and the same mouse carries the other three for eighteen months with no extra tumours. That gap is why a person was allowed to try this.