Longevity Science

Senolytics

A class of drugs that selectively induce death of senescent cells — aged, non-dividing cells that accumulate with age and secrete inflammatory signals. Senolytic therapy aims to reduce chronic inflammation and tissue dysfunction associated with aging.

Senolytics are pharmaceutical or nutraceutical compounds that selectively kill senescent cells — cells that have permanently exited the cell cycle but remain metabolically active, secreting a cocktail of pro-inflammatory cytokines, proteases, and growth factors known as the senescence-associated secretory phenotype (SASP).

Why Target Senescent Cells

Senescent cells accumulate with age in virtually all tissues. While they represent a small fraction of total cells (estimated 2-5% in aged tissues), their SASP has outsized effects:

  • Driving chronic low-grade inflammation (inflammaging)
  • Degrading extracellular matrix and tissue structure
  • Impairing stem cell function and tissue repair
  • Creating a pro-tumorigenic microenvironment
  • Spreading senescence to neighboring cells through paracrine signaling

Landmark mouse studies (Baker et al., Nature 2011, 2016) demonstrated that genetic clearance of senescent cells extended median lifespan by 17-35% and delayed onset of age-related diseases including cancer, kidney dysfunction, and cardiac hypertrophy.

Key Senolytic Compounds

Dasatinib + Quercetin (D+Q)

The most studied senolytic combination. Dasatinib (a tyrosine kinase inhibitor originally developed for leukemia) targets senescent preadipocytes and endothelial cells. Quercetin (a plant flavonoid) targets senescent bone marrow stem cells and other cell types. Together they cover a broader range of senescent cell populations.

In mice, intermittent D+Q dosing (not daily — senolytics work through periodic “hit and run” administration) improved physical function, reduced frailty markers, and extended lifespan.

Fisetin

A strawberry-derived flavonoid with senolytic activity. Fisetin showed the strongest senolytic effect of 10 flavonoids tested in a 2018 screen (Yousefzadeh et al., EBioMedicine). Advantages include a favorable safety profile and availability as a dietary supplement. The AFFIRM-LITE trial in humans is evaluating fisetin for age-related frailty.

A BCL-2/BCL-XL inhibitor that is among the most potent senolytics known. However, it causes thrombocytopenia (platelet depletion), limiting clinical utility.

Canine Research Status

The Dog Aging Project’s TRIAD (Test of Rapamycin in Aging Dogs) study focuses on rapamycin rather than senolytics specifically, but senolytic research in dogs is advancing:

  • Unity Biotechnology has explored senolytic approaches for canine osteoarthritis
  • Fisetin supplementation is being evaluated informally by veterinary longevity practitioners
  • The biological rationale is strong: senescent cell burden increases with age in dogs just as in other mammals

Practical Considerations

Senolytics are not yet approved for veterinary use. Key unknowns include optimal dosing schedules, long-term safety in dogs, interaction with existing medications, and whether benefits demonstrated in mouse models translate to canine physiology. Dog owners interested in senolytic approaches should work with veterinarians experienced in longevity medicine and follow emerging clinical evidence rather than extrapolating from rodent studies.