Melanoma Treatment Harnesses Immune System to Combat Cancer Cells

Melanoma Treatment Harnesses Immune System to Combat Cancer Cells

By ANDREW POLLACK

Published: May 15, 2013

Researchers reported on Wednesday that a combination of two drugs from Bristol-Myers Squibb shrank tumors significantly in about 41 percent of patients with advanced melanoma in a small study. In few of the 52 patients in the study, tumors disappeared completely, at least as could be determined by imaging.

“I think it was really the rapidity and the magnitude of the responses that was impressive to us,” Dr. Jedd D. Wolchok of the Memorial Sloan-Kettering Cancer Center, said in a telephone news conference organized by the American Society of Clinical Oncology.

Dr. Wolchok’s study, and others on the immune system drugs, will be perhaps the most closely watched items at the society’s annual meeting, which begins on May 31 in Chicago.

The drugs are also generating huge interest on Wall Street, which projects billions of dollars in annual sales. While Bristol is generally considered to have a lead, Merck and Roche are not far behind with similar drugs.

Data released Wednesday from an early-stage study of Roche’s drug, which is known as MPDL3280A, showed significant tumor shrinkage in 21 percent of 140 patients who had a variety of cancers including lung, melanoma and kidney cancer.

The studies are small and they did not compare the drugs with a placebo or with another treatment, and it is unclear if they will lengthen lives. Moreover, it is unclear how long the effects will last, though there are signs that for many patients, it could be a year or more.

Cancer cells often successfully hide from the body’s immune system by preventing T-cells from attacking them. The new drugs basically work by disabling brakes on the immune system, allowing the T-cells to attack the tumors.

One of the drugs in Bristol-Myers’ combination is Yervoy, which was approved as a treatment for melanoma in 2011. Yervoy disables an immune system brake called CTLA-4. It shrinks tumors in only about 10 percent of patients, but the effects can last for a long time.

The other drug in its combination is nivolumab, which is not yet on the market. It disables a brake known as PD-1, which sits on the surface of T-cells. Tumors can produce a protein called PD-L1, which binds to PD-1 and makes the T-cells inactive.

Nivolumab, and the drug being developed by Merck, called MK-3475, are antibodies that bind to PD-1, while Roche’s drug binds to PD-L1. It is not clear yet which approach is better.

It may be possible to test tumors for the presence of PD-L1, and use the drugs mainly for those patients, where it is expected to work more effectively.

It is also not clear yet how many types of tumors the drugs will work for. All the companies are targeting melanoma, a deadly skin cancer, because there is evidence that it is sometimes controlled spontaneously by the immune system. The companies also have data for lung and kidney cancer. Roche’s study showed some effect in colorectal and head and neck cancer as well.

Bristol-Myers’s stock rose 5 percent on Wednesday, even though the results of the study were not released until 6 p.m., after the close of regular trading.

Mark Schoenebaum, the pharmaceutical analyst at ISI Group, said investors were hoping the combination of the two Bristol drugs would significantly shrink tumors in at least 50 percent of patients.

He said in a note on Wednesday that the overall shrinkage rate was perhaps a bit below expectations but added that for many patients, the shrinkage was more than 80 percent.

“The point is that the depth of those responses is pretty incredible,” he wrote.

Some experts say that tumor shrinkage, a measure that evaluates conventional chemotherapy drugs that poison cancer cells, may understate the effect of these new drugs.

“Sometimes it takes awhile for the immune system to be revved up,” said Dr. Gary Gilliland, who leads cancer drug development at Merck.