A Popular Science View of the Development of Senolytic Therapies
Over the last decade, an increasing diversity of research groups and companies are working towards the clinical use of senolytic therapies to reverse aspects of aging in older patients by clearing harmful senescent cells. Of the early senolytic therapies, the dasatinib and quercetin combination is the only one with published data in human clinical trials showing clearance of senescent cells. This treatment is in fact easily accessible to self-experimenters, and even being prescribed off-label by more adventurous physicians. The biotech industry is working to produce a next generation of (probably) better approaches, and obtain regulatory approval for their use. A decade from now, clearance of senescent cells in older people will be widespread, and the incidence of serious age-related disease will decrease by some noticeable amount as a result.
There is a growing research movement to halt chronic disease by protecting brains and bodies from the biological fallout of aging. If these researchers are successful, they'll have no shortage of customers: People are living longer, and the number of Americans age 65 and older is expected to double, to 80 million, by 2040. One of their targets is decrepit cells that build up in tissues as people age. These "senescent" cells have reached a point - due to damage, stress or just time - when they stop dividing, but don't die. While senescent cells typically make up only a small fraction of the overall cell population, they don't just sit there quietly. Senescent cells can release a slew of compounds that create a toxic, inflamed environment that primes tissues for chronic illness. Senescent cells have been linked to diabetes, stroke, osteoporosis, and several other conditions of aging.
These noxious cells, along with the idea that getting rid of them could mitigate chronic illnesses and the discomforts of aging, are getting serious attention. The National Institutes of Health is investing $125 million in a new research effort, called SenNet, that aims to identify and map senescent cells in the human body as well as in mice over the natural lifespan. And the National Institute on Aging has put up more than $3 million over four years for the Translational Geroscience Network that is running preliminary clinical trials of potential antiaging treatments. Drugs that kill senescent cells - called senolytics - are among the top candidates. Small-scale trials of these are already underway in people with conditions including Alzheimer's, osteoarthritis, and kidney disease.
Numerous medical companies have jumped on the anti-senescence bandwagon. But results have been mixed. One front-runner, Unity Biotechnology dropped a top program in 2020 after its senolytic medication failed to reduce pain in patients with knee osteoarthritis. More recently, however, the company reported progress in slowing diabetic macular edema, a form of swelling in the back of the eye due to high blood sugar. Despite the excitement, senolytic research remains in preliminary stages. A lot of basic and clinical research must happen first, but if everything goes right, senolytics might someday be part of a personalized medicine plan: The right drugs, at the right time, could help keep aging bodies healthy and nimble.