Karl Pfleger proposed a measure of success for aging therapies beyond lifespan and attributed stalled progress to funding rather than science
Karl Pfleger proposed a measure of success for aging therapies beyond lifespan and attributed stalled progress to funding rather than science
On September 18, 2026, investor Karl Pfleger answered a question from João Pedro de Magalhães, a professor of molecular biogerontology: how can we determine whether an aging therapy works using a measure other than lifespan? Pfleger proposed an alternative criterion and described an experiment by LEV Foundation, the only organization testing such combinations in practice. Two of its three approaches failed, and a second, larger experiment cannot begin because of insufficient funding.
On August 9, 2026, de Magalhães wrote that humanity was getting no closer to overcoming aging: after almost a hundred years, calorie restriction remained the only reliable way to extend lifespan in mice. On August 10, Pfleger disagreed: judging the field's progress by its single best therapy was a mistake. Aging involves at least seven distinct types of molecular damage, each requiring a different therapy, just as different cancers require different treatments. One example is the accumulation of senescent cells, which have stopped dividing and damage surrounding tissues.
De Magalhães disagreed that same day: lifespan was the only reliable criterion, because other measures could easily lead researchers to mistake treatment of a symptom for treatment of aging. On September 7, Pfleger responded with an analogy: this was like telling Kennedy in 1960 that physics could not get him to the Moon, then demanding that he fly there himself immediately instead of in ten years. On September 17, de Magalhães acknowledged the need for combinations but asked a direct question: what evidence would establish that an intervention works, and what would establish that it does not?
The next day, Pfleger answered: a therapy supports the “geroscience hypothesis” if it treats, alleviates, or prevents several distinct age-related diseases, even if it does not extend lifespan on its own. Individual interventions may show no effect when used alone, with benefits emerging only when they are combined.
Pfleger then cited the only practical example he knew of: LEV Foundation (LEVF), the organization led by gerontologist Aubrey de Grey after his departure from SENS Research Foundation. LEVF had enough money and time for one experiment testing three interventions against age-related damage: the RMR1 experiment in a thousand mice. Its full report showed that the effects of a single round of repair did not last beyond a year. Two of the three approaches had problems: Pfleger called one “broken” and another “partially broken.” A second experiment, involving eight interventions, is still seeking funding.
“It is pretty dismal that only one group is even trying combinations. The field should do better, but unfortunately, structural incentives matter: neither academia nor biotech has an incentive to combine what already exists,” Pfleger wrote.
The idea of combining therapies that repair damage dates back to the SENS program, which de Grey has promoted since the early 2000s. In April, Pfleger described two strategies for longevity: slowing aging and targeted repair of damage that has already accumulated, cautioning that the second requires a different measure of success.