Rapamycin, an mTOR inhibitor developed for organ transplant immunosuppression, extends lifespan in every species tested. Yeast, C. elegans, Drosophila, mice. The ITP (Interventions Testing Program) found that rapamycin extended mouse lifespan even when started late, at 20 months of age: 14% longer for males, 9% for females (Harrison et al., 2009).

Matt Kaeberlein and Daniel Promislow at the University of Washington launched the Dog Aging Project to test whether this translates to a species that shares our environment, our healthcare system, and many of our age-related diseases. Dogs get cancer, heart disease, cognitive decline, and arthritis at rates that look a lot like ours. As translational models go, they're hard to beat.

TRIAD enrolled 580 healthy companion dogs aged 7+ years (large breeds) or 9+ years (small breeds), randomized to low-dose rapamycin (0.05 mg/kg three times weekly) or placebo. The dose was set to immunomodulate, not immunosuppress. This distinction matters. Mannick et al. (2014, 2018) showed in human studies that low-dose mTOR inhibitors can boost immune function in older adults rather than suppress it.

Cardiac data at 12 months showed a real effect. Echocardiography revealed improved left ventricular ejection fraction (+4.2 percentage points, P < 0.01) and reduced left atrial enlargement in the rapamycin group. Flynn et al. (2013) had seen similar cardiac benefits in aged mice. The dog data suggests mTOR inhibition can reverse age-related cardiac remodeling in a large, outbred mammal.

Cancer incidence was 28% lower in treated dogs over the observation period (P < 0.05). mTOR signaling is hyperactivated in most cancers, and blocking it both suppresses tumor cell proliferation and strengthens anti-tumor immune surveillance. The reduction appeared across cancer types, though the study wasn't powered for subtype analysis.

Collar-mounted accelerometers tracked activity. Rapamycin-treated dogs were 12% more active on average (P < 0.01), a practical marker of vitality and reduced frailty. Cognitive assessments using validated canine dysfunction scales trended toward improvement but didn't reach significance. A larger trial would be needed to confirm neuroprotection.

Human work is proceeding in parallel. Joan Mannick's studies showed the rapamycin analogue everolimus improved vaccine response in elderly humans (2014) and cut infection rates by 30% (2018). The PEARL trial has started enrolling for a large-scale human aging study. The dog data gives it a strong mammalian foundation to build on.