What are senolytics, and can clearing out old cells slow ageing?

Senolytics are a class of small molecules under basic research to test whether they can selectively kill senescent cells and improve health in humans. Senescent cells are cells that have stopped dividing but have not died. They contribute to the ageing phenotype, including frailty syndrome, sarcopenia and age-associated diseases, so a goal of the research is to find agents that delay, prevent, alleviate or reverse age-related diseases.

Why would clearing them help? Senescent cells have a characteristic secretory phenotype, called the SASP, made of inflammatory cytokines, growth factors and proteases. That means they send signals that can feed inflammation. Yet senescence also has a protective role: its importance has been attributed to preventing cancer, and more recently to development and tissue repair. The SASP itself has distinct effects depending on the cellular context. So the aim is to remove senescent cells selectively, not to abolish senescence.

The status of the evidence is early. Possible senolytic agents are under preliminary research, including some in early-stage human trials. Most candidates are repurposed anti-cancer molecules, such as the chemotherapy drug dasatinib and the experimental molecule navitoclax. In a 2011 study in mice, Baker and colleagues found that removing senescent cells could delay age-associated disorders, while trials in people are at an early stage.

That is where caution comes in. In 2023 the US Food and Drug Administration stated that no medication has been proven to slow or reverse the ageing process. Senolytics are a promising research area, not an established treatment.