The clock turns back in a human eye

In March 2026 a glaucoma patient received an injection of ER-100, a therapy that does something no approved medicine attempts: it tells aged cells to partially rewind their own age. The tool is three of the four "Yamanaka factors," the molecular switches that can return any adult cell to an embryonic state. Used at full strength they erase a cell's identity entirely — the basis of stem-cell science. Used briefly and partially, the bet is that a cell sheds the marks of age while still remembering it is a retinal neuron.

Three of the four factors, not all four — the omitted one is the cancer-linked switch.

Until now this idea — partial epigenetic reprogramming — existed only in mice and monkeys, most famously in a 2020 experiment that restored sight in glaucomatous mice. The FDA cleared ER-100 for human testing on January 28, 2026, the first time the approach has been dosed in a person. The whole field's central fear is written into the eye-first choice and into one deliberate omission: the therapy uses three factors, not four, dropping the one (c-Myc) most linked to cancer, and starts in the eye because it is sealed off from the body and easy to inject — the safest place to test a technology whose nightmare is a cell that forgets to stop growing.

This is a Phase 1 safety trial in a handful of patients, dosed one at a time with a month between them; there is no efficacy data, and may be none that matters for years. What changed is the category. Aging as something you intervene on directly — rather than its individual diseases — left the animal lab and entered a human body, with the regulator's permission.

A second thread is converging from the opposite end. In 2025, OpenAI and Retro Biosciences used a purpose-built model to redesign two of these same reprogramming factors from scratch, reporting protein variants over fifty times better at flipping cells toward youth than the natural versions — though that result is a lab measurement of marker activity, not peer-reviewed and not yet near a clinic. One line of work is carrying a six-year-old mouse recipe into a person; the other is engineering better ingredients before they ever get there.