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By Julie Steenhuysen
CHICAGO, May 15 (Reuters) - Melanoma patients treated withtwo Bristol-Myers Squibb drugs fared much better thanthose who received either of the medications individually, a newadvance for treatments that harness the body's immune system tofight cancer.
Bristol released preliminary data from the early-stage trialon Wednesday, with more detailed results expected to highlightthe American Society of Clinical Oncology's annual meeting inChicago that starts at the end of the month.
Patients in the study received Bristol's immunotherapyYervoy, which is already on the market, and an experimentaltreatment called Nivolumab that attacks animmune-system-inhibiting protein called PD-1. The combinedtreatment shrank tumors in a majority of patients.
"We have never seen this with immunotherapy before," said DrJedd Wolchok of New York's Memorial Sloan-Kettering CancerCenter. "The vast majority of patients have a decrease in tumorburden. In melanoma, we're used to seeing the opposite," he saidof the notoriously difficult-to-treat form of skin cancer.
Investors have been eager to see results of the study, withBristol shares reaching a 10-year high on Wednesday in advanceof the data release.
Both drugs are designed to target different parts of theimmune system that act as brakes even when cancer is present,preventing immune cells from attacking tumors. By gumming upthese brakes, the drugs free the immune system to attack andkill tumor cells.
Approved in 2011, Yervoy, or ipilimumab, was the first drugto significantly extend survival in patients with advancedmelanoma, the most deadly form of skin cancer. It boosts theimmune system by blocking the action of a protein called CTLA-4.
Nivolumab, which is in late-stage testing, targets a proteincalled PD-1, or Programmed Death receptor, a new class ofimmune-system drugs that shows promise not only in melanoma butalso in lung and kidney cancer.
Typically, only about 11 percent of patients respond toYervoy, and recent studies in melanoma suggest Nivolumabproduces a response rate of about 41 percent, Wolchok told anews briefing.
The current study looked at the combination of the two drugs based on animal studies suggesting that together they mightwork better than either drug alone.
Wolchok reported results for 86 patients in the trial as ofFebruary 2013, including 52 patients who were on both drugs atthe same time. In one of the treatment groups, which will likelyadvance to late-stage trials, 53 percent of patients treatedwith both Yervoy and Nivolumab simultaneously had an objectiveresponse - defined as at least a 50 percent reduction in tumorsize.
RAPID RESPONSE
Dr Sandra Swain, president of ASCO, called the findingsremarkable. "This combination treatment led to a very rapid andprofound lasting tumor shrinkage. Ninety percent of patients arestill responding," she said.
Three out of four patients who responded to the dualtreatment had tumor shrinkage in the first three months.
Among the most advanced melanoma patients, Wolchok said thecombination of the two drugs produced "rapid and deepregressions, with many showing more than 80 percent tumorregression by the time of the first scan."
Overall, most patients had some decrease in tumor size. In31 percent of all patients taking the dual therapy, tumorsshrank by greater than 80 percent, Wolchok said.
In 18 percent of patients, the drug combination produced acomplete response, meaning tumors were no longer detectable,Wolchok said in an interview. He said they do not yet have anydata on relapse because 90 percent of patients who responded tothe treatment are continuing to benefit.
The combination also appeared to be safe. About half ofpatients who got both treatments had a drug-related side effect,but in most cases it was linked to elevations in enzymes relatedto the pancreas and liver.
"These are reversible, sometimes without treatment," Wolchoksaid, although some patients did need a short course of thesteroid prednisone. There were no drug-related deaths.
"We really didn't see anything new with the combination"related to safety, he said.
Bristol-Myers plans a late-stage clinical trial that looksat both drugs in combination, as well as each separately, inpatients with melanoma. It has also begun testing the samecombination in lung cancer and renal-cell cancer.
"We view the combination of immunotherapy as a significantone that we'll be pursuing," Michael Giordano, Bristol-Myers'senior vice president of global development for oncology and immunology, said in an interview.
So far, Bristol-Myers is furthest ahead in its developmentof a PD-1 inhibitor, but Merck & Co Inc last month wondesignation from the U.S. Food and Drug Administration as a"breakthrough therapy," which could speed development andregulatory review of the product.
In a recent note, Bernstein Research analyst Tim Andersonsaid Bristol's anti-cancer drug PD-1 "is the major driver ofinvestor interest at the moment," but said awareness is buildingthat competitors "may not be very far behind."
Last November, Merck reported results from a trial of itsdrug in patients with advanced melanoma and saw a 47 percentresponse rate. In that trial, the drug benefited patients whohad previously been treated with ipilimumab but had notresponded, said Dr. Gary Gilliland, a Merck senior vicepresident for oncology.
Merck plans to present an update of this study on June 2 atthe ASCO meeting. Gilliland said the company also is studyingits treatment in so-called triple-negative breast cancer, ahard-to-treat form of the disease, as well as head and neckcancer and bladder cancer.
Other companies pursuing the PD-1 or related pathwaysinclude Roche, GlaxoSmithKline and Teva.
"PD-1 is arguably the most exciting breakthrough in cancertherapy in a decade," said ISI Group analyst Mark Schoenebaum."There is speculation that it might offer a cure for somepatients with solid tumors. This is unprecedented." (Additional reporting by Bill Berkrot in New York; Editing byMichele Gershberg and Prudence Crowther)
