New Drug May Help Immune System Fight Cancer
Early study found tumor reduction in several forms of the disease
Pardoll is testing a drug that targets PD-1 for Bristol-Myers Squibb. He was not involved in the current study.
The drugs are part of a wave of new treatments that work by spurring the immune system to take on tumors. These drugs are building on the successes of medications like Provenge, the first cancer immunotherapy, which was approved in 2010 to treat prostate tumors, and Yervoy, which was approved in 2011 to treat metastatic melanoma.
Yervoy works early in the immune reaction to wake up T-cells that are essentially napping on the job, Pardoll said. The PD-1 and PD-L1 drugs work later, at the cellular level.
"This is a whole new kind of treatment, and the early data has looked so impressive," Pardoll said. "I think this just reflects the excitement among biotechnology companies and big pharma in this field."
To understand why researchers are excited, it helps to understand how poorly most cancer drugs perform in early trials. A study published in the journal Clinical Cancer Research in August 2005 found that middle-of-the-road response rates for cancer drugs in early trials was just 3 percent, with the best response rate topping out at 18 percent.
Response rates are so dismal in part because doctors usually don't try unproven drugs in cancer patients until they have run out of other options. All the patients in this study had seen their cancer progress despite several prior treatments. Most had seen their cancer spread beyond its original site.
Pardoll said he also has been impressed with the length of time that patients continue to see benefits from the medications in the new study.
"Among the patients that did respond to anti-PD-1, who had been followed for more than a year, roughly two-thirds were still in a response a year out," he said. "That's something you don't see with chemotherapy; you don't see it with current targeted therapies.
"We think this is because the immune system is being re-educated," Pardoll said. "If that's the case, will we be able to discontinue the antibody and have the patient's immune system take over and keep the cancer at bay?"