Bristol-Myers Squibb Co and Merck & Co are assessing which patients will most benefit from new cancer treatments based on a protein found in their tumors, but that guide, known as a biomarker, may be too unreliable, researchers and health experts said.
Bristol’s Opdivo and Merck’s Keytruda are both therapies aimed to block a protein known as Programmed Death receptor (PD-1) that tumors use to avoid the body’s natural defenses.
Pfizer, Roche Holding and AstraZeneca have also similar drugs in an earlier stage of development. The drug makers are performing clinical trials that test patient tumors for a related protein called PD-L1.
The new drugs are mainly aimed at patients with so-called solid tumors suffering from diseases, including lung cancer and liver cancer. The most common type, lung cancer, claims 1.8 million new cases each year worldwide. According to Morningstar, sales of drugs to block PD-1 could reach $33 billion a year by 2022.
New data released last Friday showed that Opdivo was most helpful to lung cancer patients with the highest levels of PD-L1 in their tumors, adding to evidence of a link. That would suggest that doctors routinely test for the protein before giving a patient Opdivo. The tactic is already exercised for some cancer drugs that are prescribed only if a patient has a specific genetic mutation.
Test results can differ depending on which part of the tumor was biopsied and the degree of which the cancer has spread. Besides, tests developed by drug makers don’t follow the same standards.
Hence, while clinical trials exhibit that drugs like Opdivo and Keytruda work best in people who test positive for PD-L1, however some patients who test negative have also benefited from the treatment.
Dr Roy Herbst, Yale Cancer Center chief of medical oncology in New Haven, Connecticut, referring to Opdivo said, “We don’t even know if PD-L1 is the right biomarker.”
The U.S. Food and Drug Administration’s oncology chief, Dr. Richard Pazdur, alerted that there is still a great deal of uncertainty about how to best measure for PD-L1.
He said, “The key issue is whether the biomarker is essential for safe and effective use of the drug. If not, then it is probably not going to be an essential element in the indications for the drug. But it would be useful information.”