In the new paper, the researchers wrote that potential clinical trial scenarios include testing whether senolytic drugs could alleviate multiple chronic diseases in a single patient or whether such drugs could treat conditions that involve senescent cell accumulation in one location in the body, such as osteoarthritis.
They also suggest testing whether the drugs could treat diseases for which there are no medicines proven to slow the progression of that disease, such as idiopathic pulmonary fibrosis
, a cell senescence-associated disease that affects the lungs.
Other potential clinical trial scenarios include testing whether the drugs could alleviate frailty in older adults or could treat conditions associated with chemotherapy or radiotherapy, since radiation can produce cellular senescence, Kirkland said.
For instance, "in mice, if you treat one leg with enough radiation, after three months, the mouse has trouble walking. If you give a single dose of these drugs, they're able to walk quite well, and that persists for two years," he said. "These drugs could mitigate the effects of therapeutic radiation."
Certain experimental cancer drugs already undergoing clinical trials, such as navitoclax
, have been shown to have some senolytic properties
, Kirkland said. If senolytic drugs prove to be efficient in treating humans and end up available for use, he said, they could cost about the same as some cancer drugs.
"Some of the drugs at the moment are moderately expensive," he said.
Cancer drugs can range in cost from about $20 a month to thousands a month. Venclexta or venetoclax
, which has been approved by the Food and Drug Administration and has been studied in combination with navitoclax
, has a monthly price tag of about $8,000, according to the Memorial Sloan Kettering Cancer Center
"If we're able to reduce hospitalizations ... the savings on the medical care and hospital side might more than offset the cost of these drugs by a longshot," Kirkland said, though it remains unclear what the dosage options would be for senolytic drugs for short- or long-term use.
What the future holds for senolytic drugs
As for how soon he thinks human clinical trials might commence, Kirkland said doctors could have an idea of how well senolytic drugs work for serious health conditions in about a year and a half or two years.
Once the drugs are tested in humans, researchers expect many companies to be lining up to develop or manufacture senolytic drugs. Some have already expressed interest.
One company, Unity Biotechnology
, aims to be the first to demonstrate that removing senescent cells can cure human diseases, said its president, Nathaniel David.
"In the coming decades, I believe that health care will be transformed by this class of medicine and a whole set of diseases that your parents and grandparents have will be things you only see in movies or read in books, things like age-associated arthritis," said David, whose company was not involved in the new paper.
Yet he cautioned that, while many more studies may be on the horizon for senolytic drugs, some might not be successful.