Drugs that prod the body’s immune system to fight cancer are the talk of the medical community, with scientists and doctors hailing these “immunotherapy” treatments as breakthroughs.
But hidden beneath the hype is the problem that scientists don’t fully understand how they work.
“We can’t say the C-word yet,” said Dr. Carl June with the University of Pennsylvania Medical Center, referring to “cure,” on a recent Ken Burns documentary on cancer.
So, when can the medical community get comfortable using the C-word?
Apparently after a lot more research.
Immunotherapy is a radical break from targeted therapies such as the leukemia drug Gleevec. Those drugs can stop working over time as cancer cells mutate and become resistant.
Immunotherapy drugs, however, enable the immune system to adapt and attack cancer even after it mutates, said Dr. James Gulley, head of the National Cancer Institute’s immunotherapy section.
Currently three immunotherapy drugs are available that use antibodies to attack melanoma and lung cancer cells. However, it is a mystery why immunotherapy products for other cancers such as colon or prostate don’t work.
Researchers believe a tool to help solve this mystery is biomarkers, which are basically tests to determine which treatment is right for a patient.
A blood test for cholesterol is a biomarker to determine whether the patient is at risk for cardiovascular disease.
“We’d know the best way to use new drugs if we had biomarkers,” Dr. Lisa Butterfield, a professor of medicine at the University of Pittsburgh, told the Examiner.
Biomarkers can also help researchers determine the best patient to enroll in a clinical trial.
Currently early trials enroll patients with all types of late-stage cancer and look for signals that an experimental drug works, Butterfield said.
Say the drug works on lung cancer patients but not for those with colon cancer. Researchers would have to conduct another clinical trial to find out why.
That takes up valuable time that most cancer patients don’t have, Butterfield said.
Instead, researchers can use biomarkers to place a patient in a trial studying the best drug for them. Instead of conducting multiple trials, researchers will know much faster whether an immunotherapy is working.
This can reduce the length and uncertainty of drug development, a large hurdle in pursuing new therapies.
Biomarkers can also be used to determine whether an immunotherapy is working, which is difficult to measure, as an immunotherapy can take months to shrink a tumor, as opposed to weeks for chemotherapy, Butterfield said.
The problem is immunotherapy cancer biomarkers aren’t as ubiquitous as cholesterol tests.
“We don’t really have validated, agreed-upon immunotherapy biomarkers,” Butterfield said. “We have hints, suggestions, trends.”
There are several reasons such biomarkers aren’t available. There aren’t standardized methods for measuring or qualifying a new biomarker, said Lyndsay Meyer, a spokeswoman for the Food and Drug Administration.
There is also inadequate scientific information on the “causes, biochemical pathways and natural histories of certain diseases,” she added.
There is currently a mad dash among government agencies and drug companies to identify cancer biomarkers.
The National Institutes of Health has funded studies on cancer biomarkers, but Butterfield said the agency is hamstrung by a lack of funding. NIH Director Francis Collins told Congress recently that the sequestration has resulted in $19 billion in reduced funding over the next decade.
As a result, pharmaceutical companies are forced to fund not only their own research but also projects at universities, Butterfield said.
“The money for this sort of thing is very tight, and it is difficult to get expensive [tests] funded,” she added.
The FDA does have a program to qualify biomarkers developed by research institutes. A pharmaceutical company can also apply for agency approval to use a biomarker in a clinical trial, Meyer said.
Despite the setbacks, Butterfield is confident that there will be immunotherapy biomarkers within the next five years.
Gulley, of the National Cancer Institute, is also optimistic that soon these immunotherapies can be the breakthrough the cancer field has been looking for.
“Yes, we have seen a lot of hype before with different therapies,” he said. But now we are “seeing in randomized, controlled studies strong evidence that these agents work.”
