Drug To Clear ‘Zombie Cells’ In Humans Produces Disappointing Results – But Hope Is Not Lost

Senescent cells are cells that have stopped dividing as a result of damage or age, and instead release signals and inflammatory molecules that harm other cells. They are thought to contribute to all known diseases of ageing. Senolytic drugs are drugs that kill senescent cells while leaving normal cells untouched. They have shown promise in animals and humans for various conditions but human trials are still in their early stages.

These trials suffered a fairly significant setback this week. UNITY Biotechnologies is one of the companies investigating the use of senolytics to treat human diseases. Back in 2020, they announced that their senolytic treatment failed to produce significant benefits in knee osteoarthritis patients during a 12 week clinical trial.

Now, a phase II trial for the treatment of macular degeneration with senolytics has also led to disappointing results. The drug inhibits a protein that prevents senescent cells from self-destructing, but did not have nearly as much of an effect on participants’ vision as was hoped. While participants taking the gold standard treatment aflibercept unexpectedly gained visual acuity, those receiving senolytics generally maintained visual acuity (with a slight decline on average).

Though these results may sound discouraging, they probably have more to do with how the treatments were administered than with the potential of senolytics to treat age related disease. In all trials mentioned, senolytics were introduced locally into the diseased area. This improves the safety of the treatment and makes it easier to get a clinical trial approved. Unfortunately, senescent cells exist throughout the body and drive ageing in large part through the molecules that they secrete. This means that removing senescent cells from the diseased area alone might not be enough, and that is what many scientists are concluding based on these failures.