The first human test of epigenetic reprogramming is an eye trial in 18 people
Three of the four Yamanaka factors, delivered to one eye and switched on with an antibiotic for eight weeks. The mouse data are striking; the trial is a safety study and will not measure ageing.
Partial epigenetic reprogramming is the most theatrical idea in ageing biology. Take three of the four transcription factors that turn an adult cell back into a stem cell, express them briefly, and the cell is supposed to reset its epigenetic state to a younger configuration without losing its identity. It has been demonstrated repeatedly in mice. As of March 2026 it is being tried in people.
The trial is small and it is not about ageing. It is a phase 1 safety study of a gene therapy called ER-100 in 18 participants with two optic nerve conditions [s1]. Understanding what it can and cannot show is the whole point.
What is actually being given
ER-100 is delivered by a modified adeno-associated virus vector, injected once into the vitreous of one eye [s1]. The vector carries instructions for producing three transcription factors — OCT4, SOX2 and KLF4, collectively OSK — intended to reverse age-related epigenetic changes in retinal cells [s1]. It does not alter a participant's existing genes, and the viral vector has been engineered so that it cannot cause infectious disease [s1].
The switch is an antibiotic. OSK expression is activated by systemic doxycycline taken for eight weeks — 56 days — and then stopped [s1]. That is the control mechanism the whole approach depends on: reprogramming that runs indefinitely does not rejuvenate cells, it turns them into tumours.
The design is sequential rather than randomised, and unmasked [s1]. Participants with open-angle glaucoma are enrolled first, in a dose escalation at 2 × 10¹¹ vector genomes per eye and then 6 × 10¹¹, each dose level starting with a single sentinel participant before a safety review committee allows more [s1]. Only after that cohort completes is a dose selected for participants with non-arteritic anterior ischaemic optic neuropathy, beginning with three people and expanding to six after review by a data safety monitoring board [s1]. Eligible participants are aged 40 to 85 [s1].
The primary outcomes are treatment-emergent adverse events, dose-limiting toxicities and changes in liver function tests, measured from baseline to day 56 and day 112 [s1]. Participants are followed for up to five years, and the trial's estimated completion date is March 2032 [s1].
Why the eye, and why these two conditions
The eye is the standard first target for this kind of therapy because a single injection reaches an enclosed compartment, the untreated eye acts as an internal comparison, and vision is measurable with instruments that already exist.
Non-arteritic anterior ischaemic optic neuropathy is the sharper test of the two. Participants must have had sudden, painless vision loss in one eye within 14 days before receiving ER-100, confirmed by a specialist, with swelling of the optic nerve head and visual field loss worse than −3.0 dB [s1]. It is an acute injury with a defined onset, and there is no approved treatment. The glaucoma cohort is a chronic, slowly progressive condition, and the trial requires moderate to advanced field loss between −6 and −20 dB with reasonably preserved acuity of at least 20/80 [s1].
What the mouse data show
The foundational result appeared in Nature in 2020. Expressing OSK in mouse retinal ganglion cells restored youthful DNA methylation patterns and transcriptomes, promoted axon regeneration after injury, and reversed vision loss both in a mouse model of glaucoma and in aged mice [s2]. The benefits required the DNA demethylases TET1 and TET2 — evidence that the effect runs through the methylation machinery rather than around it [s2].
A year-long follow-up study extended it. In mice in which glaucoma-induced vision damage had already occurred, two months of OSK expression fully restored impaired vision, and vision remained restored for 11 months with prolonged expression [s3]. Significant improvement persisted for a month after OSK was switched off, then gradually diminished while staying better than baseline [s3]. No adverse effects on retinal structure or body weight were observed in glaucomatous mice with OSK expressed continuously for 21 months [s3].
That last point is the safety claim the human trial is built on, and it comes from mice.
What this trial will not answer
It will not tell anyone whether epigenetic reprogramming slows human ageing. The primary endpoints are toxicity measures over 112 days in 18 unblinded participants across two different diseases [s1]. Vision outcomes are secondary, there is no placebo arm, and NAION in particular can recover spontaneously — which is precisely why an open-label study of six people cannot attribute improvement to the treatment.
It will also not resolve the oncology question. Reprogramming factors are, by construction, tumour-associated genes; the five-year follow-up period in the protocol [s1] is a reasonable acknowledgement that eight weeks of expression is not the timescale on which that risk would declare itself.
Both underpinning mouse studies were conducted with commercial involvement: several authors hold equity in or are inventors on patents licensed to the company sponsoring the trial [s2][s3]. That is normal in translational science and it is not a criticism, but it is a reason to want the human results read by people with no stake in them.
What the trial does establish, if it completes without serious toxicity, is that the approach can be tested at all. That is a real milestone, and it is a smaller one than the phrase "cellular rejuvenation" implies.
Sources
- [s1] A Phase 1 Single Dose Study to Evaluate the Safety and Tolerability of ER-100 in Optic Neuropathies. ClinicalTrials.gov registry record NCT07290244, last updated May 2026. https://clinicaltrials.gov/study/NCT07290244
- [s2] Reprogramming to recover youthful epigenetic information and restore vision. Nature, published online December 2, 2020. https://doi.org/10.1038/s41586-020-2975-4
- [s3] Sustained Vision Recovery by OSK Gene Therapy in a Mouse Model of Glaucoma. Cellular Reprogramming, published online December 7, 2023. https://doi.org/10.1089/cell.2023.0074
Sources
- A Phase 1 Single Dose Study to Evaluate the Safety and Tolerability of ER-100 in Optic Neuropathies (NCT07290244) — ClinicalTrials.gov , May 19, 2026
- Reprogramming to recover youthful epigenetic information and restore vision — Nature , December 2, 2020
- Sustained Vision Recovery by OSK Gene Therapy in a Mouse Model of Glaucoma — Cellular Reprogramming , December 7, 2023
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