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Issue #1
Partial reprogramming gets its first human safety readout, a single splicing factor extends lifespan in old mice, and a brain protein seems to set the pace of aging body-wide. Early, small, and worth knowing.
First human reprogramming data, a 14% mouse lifespan signal, and an astrocyte lever on whole-body aging
In this issue
- First people dosed with a Yamanaka-factor rejuvenation therapy: well tolerated so far HumanPhase 1
- A splicing factor rejuvenates cells without erasing their identity, and extends mouse lifespan MouseCellsPreclinical
- Boosting one protein in brain astrocytes slows aging across the mouse body MousePreclinical
First people dosed with a Yamanaka-factor rejuvenation therapy: well tolerated so far
Life Biosciences reported interim Phase 1 data for ER-100, an AAV gene therapy injected into the eye that switches on three Yamanaka factors (OSK) while patients take oral doxycycline for 8 weeks.
In 3 people with open-angle glaucoma at the lowest dose, there were no dose-limiting toxicities or serious adverse events through day 56, and 2 of 3 showed visual-field gains. The safety board cleared escalation to a dose three times higher.
Evidence
HumanPhase 1
Model Adults with open-angle glaucoma | Stage Open-label Phase 1, interim, day 56 |
Sample size n = 3 (lowest dose) | Review Company-reported, not peer reviewed |
Key caveat. No control arm and only 56 days of follow-up, far too short to judge durability or tumor risk; visual-field tests are noisy.
Why it matters for LEV
Partial epigenetic reprogramming has moved from mice to humans for the first time, and the first readout is a clean safety signal.
My take. Three patients and eight weeks tells us almost nothing about efficacy, but the first human dose of a reprogramming therapy is a huge milestone. Getting through it without a safety scare is exactly what the field needed.
Source: Life Biosciences, ER-100 Phase 1 trial (NCT07290244). ClinicalTrials.gov (2026).
A splicing factor rejuvenates cells without erasing their identity, and extends mouse lifespan
Wyss Institute researchers built a gene-expression age predictor for human fibroblasts and screened for genes that push old cells toward a young profile. The top hit, the RNA-splicing factor SRSF1, matched OSK in transcriptomic rejuvenation and lowered senescence, proteostatic stress and inflammation, while the cells stayed fibroblasts.
Switching SRSF1 on in already aged mice cut frailty progression by 44% and was associated with a 14% longer median lifespan.
Evidence
MouseCellsPreclinical✓ Peer reviewed
Model Human fibroblasts; aged mice | Stage Preclinical, late-life gene activation |
Sample size n = 9 to 10 mice per lifespan group | Review Nature Aging, 2026 |
Key caveat. Lifespan groups were tiny, so the 14% figure needs independent replication; expression mostly reached the liver.
Why it matters for LEV
A possible single-factor route to reprogramming-style rejuvenation without the dedifferentiation and cancer risk of Yamanaka factors, with a lifespan effect started late in life.
My take. Late-life start, both a frailty and a lifespan signal, and no identity loss: that's the profile I want from a rejuvenation lead. I'm filing the 14% under 'promising' until another lab repeats it.
Source: Plesa et al., Transcriptomic reprogramming screen identifies SRSF1 as a regulator of aging. Nature Aging 6, 2057-2073 (2026).
Boosting one protein in brain astrocytes slows aging across the mouse body
Raising FGF13 in the astrocytes of old mice restored maze performance close to young levels, lowered blood IL-6 and IFN-gamma, and modestly reduced senescence in skin, liver, spleen and kidney; knocking it out did the opposite.
The authors propose that aged astrocytes broadcast aging signals to the rest of the body.
Evidence
MousePreclinical✓ Peer reviewed
Model Mice treated from 16 months of age | Stage Preclinical, astrocyte gene overexpression and knockout |
Sample size n = 10 per group (behaviour); 6 to 10 (blood cytokines) | Review Aging Cell, 2026 |
Key caveat. No lifespan data, most peripheral effects were modest, and the gene-delivery intervention is not yet drug-like.
Why it matters for LEV
Adds to the evidence that the brain helps set the pace of whole-body aging, a lever that could be targeted centrally.
My take. The brain-as-pacemaker idea keeps getting more support, and this is another piece. No lifespan data and a gene-delivery intervention, so it's a direction to watch rather than a result.
Source: Zheng et al., FGF13 Alleviates the Aging Process in Mice by Regulating Astrocyte Function in the Medial Prefrontal Cortex via Phafin2 Signaling Pathway. Aging Cell 25, e70784 (2026).
That's the issue. If I got something wrong, reply and tell me; corrections go at the top of the next one.
David