By Deena Beasley
CHICAGO (Reuters) - Data from a pivotal trial of Amgen Inc's experimental melanoma therapy shows that it improved survival by 21 percent for patients with advanced forms of the deadly skin cancer compared with a standard white blood cell-boosting drug.
Final survival results are not expected until later this year, but Wall Street has been awaiting the interim trial details to help assess the drug's commercial potential within a new market of promising melanoma treatments.
RBC Capital Markets analyst Michael Yee said recently that the Amgen drug - talimogene laherparepvec, or T-Vec - will ultimately need to demonstrate that it improves overall survival by more than 15 percent.
T-Vec is an engineered virus designed to be injected into tumors, where it replicates until membranes of the cancer cells rupture and die. The drug is then expected to activate a systemic immune response to kill tumor cells throughout the body.
Other new drugs in the field include "immunotherapies," such as Yervoy from Bristol-Myers Squibb, which is designed to harness the body's immune system to fight the skin cancer.
Amgen had said in March that the trial met its main goal of showing that T-Vec shrank tumors for at least six months in significantly more patients, 16 percent, than a comparison treatment, where the so-called durable response rate was 2 percent.
Other new details of the trial, presented on Saturday at the annual meeting of the American Society of Clinical Oncology, included an overall T-Vec response rate, meaning tumor shrinkage without the six-month requirement, of 26 percent. That compares with 6 percent for patients treated with GM-CSF, a type of white blood cell-booster. Eleven percent of T-Vec patients had their tumors eradicated.
The trial also showed that patients with earlier-stage disease had the highest rates of durable response. That rate was 33 percent for stage III patients, compared with 8 percent for patients with the most advanced cancer.
David Chang, head of global oncology development at Amgen, said the company is currently in discussions with the U.S. Food and Drug Administration about how to move forward and seek regulatory approval. Melanoma is diagnosed in about 132,000 people worldwide each year.
He also said the company is interested in testing its drug in combination with Yervoy and other new melanoma therapies.
The most common side effects seen in the trial of over 400 patients were mild flu-like symptoms.
Chang said Amgen is still evaluating whether to study T-Vec as a treatment for other types of cancer.
(Reporting by Deena Beasley; editing by Michele Gershberg and Matthew Lewis)