Senolytics demonstrably clear senescent cells and reduce inflammatory markers in the blood, but this has so far only been shown in a pilot study of nine people. The animal research is impressive but not definitive for humans. Large-scale clinical evidence is still lacking, and the cancer biology of senescent cells makes indiscriminate use risky.
Senescent cells are cells that have stopped dividing but do not die. They accumulate as we age and continuously secrete inflammatory substances known as the SASP. In animal models, removing these cells with senolytics has been remarkably successful: more than 40 conditions, including heart, kidney, lung, bone and brain diseases, appeared to improve or slow down. But results in animals do not always translate to humans, and that is also the case here.
In humans, the evidence is still in its infancy. The most widely cited human study tested a combination of the cancer drug Dasatinib (100 mg) and the natural flavonoid Quercetin (1000 mg) for 3 days in only 9 people with diabetic kidney disease. Within 11 days, the number of senescent cells in fat tissue and skin decreased measurably, and blood levels of various inflammatory substances also fell. That sounds promising, but this was a pilot study with no control group and only nine participants. Moreover, several of the researchers involved have a financial interest in senolytics through patents held at the Mayo Clinic, which is relevant when interpreting the results.
Senescent cells in the brain accumulate with brain ageing and in diseases such as Alzheimer's. Whether senolytics can also make a difference there in humans is an open question. Researchers stress that many limitations and uncertainties remain before any application in the brain is possible. Clinical studies into senolytics for diabetes, pulmonary fibrosis, Alzheimer's, osteoarthritis and osteoporosis are under way, but large-scale evidence of safety and effectiveness in humans is still lacking.
One important safety consideration deserves separate attention: senescent cells are not simply harmful. Shortly after they arise, they can actually suppress tumours. Only when they persist for a long time do they become cancer-promoting through their inflammatory secretions. Senolytics could in theory help, but timing and context are crucial. This makes indiscriminate self-use risky, not least because Dasatinib is a cancer drug with known side effects.
Attention is also being directed towards the skin: there is a hypothesis that senescent skin cells can damage other organs via the bloodstream, and that a senolytics cream might be able to protect the whole body. This is, however, speculative and has not been demonstrated clinically. Experts are unanimous: senolytics are not yet ready for use outside clinical studies. Quercetin is freely available as a dietary supplement, but the available human data are too limited to support a safe or effective dose in healthy people.
Seven claims based on six PMID sources (31542391, 32686219, 35015337, 35953721, 38030088, 36045302, 33262144, 35012887). The only direct human intervention study (PMID 31542391) involves N=9 with no placebo group. The remaining sources are predominantly review articles on animal data and mechanistic research. No randomised controlled trials in humans are available in this collection of sources.