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By Bill Berkrot
June 2 (Reuters) - New data on Bristol-Myers Squibb Co's melanoma drug Yervoy, including updated results from an effort to combine it with another promising cancer immunotherapy, suggest it can improve treatment for patients with both advanced and slightly earlier stage disease, according to findings released on Monday.
Yervoy, which takes natural brakes off the immune system to help it more effectively attack cancer, is approved to treat metastatic, or stage 4, melanoma - the deadliest form of skin cancer. Cowen and Co expects the drug to capture annual sales of $1.95 billion by 2020, as it is approved in new indications and combinations with other treatments.
During the annual American Society of Clinical Oncology meeting in Chicago, Bristol-Myers presented several studies on Yervoy and nivolumab, its experimental cancer immunotherapy from a highly promising class called PD-1 inhibitors, both as standalone treatments and in combination.
In one late-stage study on Yervoy alone, the drug reduced the risk of melanoma recurrence by 25 percent following surgery compared with a placebo. The median recurrence-free survival (RFS), or average time to disease return, following successful surgery to remove cancerous tumors was 26.1 months for Yervoy compared with 17.1 months for the placebo group. The result was deemed to be statistically significant.
Patients in this study had stage 3 disease in which the cancer had spread to regional lymph nodes but not yet to other parts of the body.
"This benefit was observed across all patient sub-groups, including those who were at highest risk of recurrence," Alexander Eggermont, the study's lead investigator, said in a statement.
The result could pave the way for the drug's use earlier in the disease and boost future sales. Current treatment options to reduce the risk of recurrence following surgery are very limited, Eggermont said.
The 951-patient Phase III study was the first large trial to look at Yervoy's effect following complete resection surgery.
Overall survival data was not yet available. But three years after beginning treatment, an estimated 46.5 percent of Yervoy patients were free of disease recurrence compared with 34.8 percent in the placebo group.
Nearly half of the Yervoy patients stopped treatment due to side effects, which are common with the drug, and there were five drug-related deaths, or 1.1 percent, researchers reported.
Bristol shares were down 2 percent to $48.65 with some experts expressing concern about side effects.
"There is a delay in recurrence, however I would argue that the delay is comparable to interferon. And there was toxicity," said Dr Steven O'Day, director of the Los Angeles Skin Cancer Institute, noting the five deaths.
Ron Peck, Bristol's global development leader for Yervoy, said a high 10 milligram dose was used in the study and may have contributed to the side effect rate. A 3 mg dose is being used in later studies.
Data from a separate, early-stage study of advanced melanoma patients demonstrated compelling survival data for Yervoy combined with nivolumab.
At two years, the overall survival rate for the first 53 patients in the study was estimated to be 79 percent, down only a bit from the 85 percent survival rate reported after one year.
"If this survival data is confirmed in Phase III trials, it's unprecedented. This is really exciting data," said Dr. Mario Sznol, a professor of medicine at Yale Cancer Center in New Haven, Connecticut, and the study's lead investigator.
Among the 17 patients who received the two drug doses that Bristol chose to test in its larger, later stage trials the two-year survival rate was 88 percent.
Seventeen percent of patients in the study had a complete response, or no detectable cancer. Sznol expects that number to rise. Immunotherapy results often improve over time as the immune system learns to fight the disease.
The results were consistent whether or not a patient's tumors expressed the PD-L1 protein, which helps camouflage them against the immune system. Patients who are deemed negative for PD-L1 tend to get little benefit from drugs like nivolumab alone, suggesting the addition of Yervoy may also help them.
The incidence of serious side effects among the first 53 patients in the study was about 53 percent and rose to 62 percent with an additional group of 41 more patients.
There was a 23 percent discontinuation rate due to side effects and one drug-related death, researchers reported.
"These toxicities really are manageable in the clinic," Sznol said. "If you're getting 79 percent overall survival at two years, the side effects are clearly worth it."
BMO Capital Markets analyst Alex Arfaei expressed disappointment about separate kidney cancer data for the combination that could be contributing to the Bristol stock downturn. "We remain uncertain that the incremental benefit of adding Yervoy to nivo is worth the additional toxicity," he said. (Reporting by Bill Berkrot, additional reporting by Deena Beasley in Chicago; Editing by Michele Gershberg, Eric Walsh and Cynthia Osterman)