(Reuters) – New therapies that clinical data show can eliminate blood cancers such as leukemia and lymphoma in 40 percent to 90 percent of patients may have to be genetically modified to include a switch that shields healthy cells from attack.
The therapies could generate tens of billions of dollars in annual sales for drugmakers including Kite Pharma and Juno Therapeutics Inc, once they are approved.
The therapies involve using what are known as CAR T cells, which are white blood cells taken from the body and genetically modified to have the cancer-spotting traits of antibodies. These cells can circulate inside a person for years, even a lifetime, relentlessly seeking out cancerous growth.
But a third of the patients in some trials given CAR T cells have developed life-threatening fevers and inflammation. Doctors say the reason is that the modified T cells cause inflammation because they kill so many cancer cells so quickly. Another concern is that when the therapies are eventually targeted at solid tumors such as lung or kidney cancer, they could also attack healthy cells containing the same protein that’s the target of the anti-cancer therapy.
As a result, some drugmakers are building in “switches” to suppress CAR T cells if serious side effects emerge, or to make them self-destruct if they attack healthy tissue, according to Reuters interviews with company executives. The switches involve an additional receptor on the CAR T cell that can be controlled by giving the patient a second medication, such as the widely-used cancer drug Rituxan.
The so-called suicide switches being developed for CAR T cells are a refinement of the body’s own natural process of apoptosis, by which defective or unneeded cells are programmed to self-destruct.
Approval of the new therapies to combat blood cancers are not expected for perhaps another three or four years, analysts said. Approval for therapies to fight solid tumors will take years longer, they said.
Intrexon Corp and Cellectis SA are among the leading switch makers and could become acquisition targets or licensing partners for drugmakers that need their technology, according to analysts.
