Two caveats govern every page on this site. (1) Telomere length is a contested aging biomarker — it is measured differently by different methods, varies between tissues, and "longer" is not straightforwardly "healthier"; changing a telomere-length or telomerase-activity number in a trial is not the same as slowing human aging. (2) Activating telomerase is not risk-free — telomerase is silenced in most somatic cells and reactivated in most cancers, so its activation raises an unresolved cancer-risk question. Tellingly, the only FDA-approved telomerase drug — imetelstat (RYTELO, 2024) — inhibits telomerase to treat cancer (lower-risk MDS), the opposite direction from the anti-aging "activation" narrative.
○ Evidence tier 5 — Animal lifespan study

Record

DesignPreclinical AAV-TERT gene-therapy lifespan study (mouse)
PMID22585399
DOI10.1002/emmm.201200245
Citation statusdoi + PMID verified via Crossref 2026-07-12 (EMBO Mol Med 2012;4(8):691-704, Bernardes de Jesus, Vera, Schneeberger, Tejera, Ayuso, Bosch, Blasco, 'Telomerase gene therapy in adult and old mice delays aging and increases longevity without increasing cancer'; PMID 22585399).

Five-qualifier claim

Species / populationAdult (1-year) and old (2-year) mice.
Exposure, route, scheduleSingle intravenous dose of an AAV9 vector expressing mouse TERT (AAV9-Tert).
Comparator / durationAAV9 empty-vector / untreated controls; followed to end of life.
Endpoint / numeric resultMedian lifespan increased ~24% when treated at 1 year of age and ~13% when treated at 2 years, with delayed aging markers and NO reported increase in cancer incidence.
What it did NOT establishA mouse result. Mouse telomere biology differs from human; there is no human lifespan, disease, or safety evidence, and the human cancer-risk question is unresolved.

Primary reference

https://doi.org/10.1002/emmm.201200245

Exact identifier confirmed against the primary record via Crossref/ClinicalTrials.gov where stated in the citation status; anything marked needs_primary_fulltext is not yet confirmed.