CHICAGO, June 5 (Reuters) - A clinical trial from Roche Holding AG combining the company's newer targeted drug for breast cancer with an older treatment resulted in a modest benefit for women with a specific type of disease, according to data presented on Monday.
Roche has sought to shield its lucrative breast cancer franchise from cheaper copies of its drugs by showing the combination would provide a greater benefit.
After surgery to remove their tumors, nearly 5,000 women with HER2-positive, early breast cancer were treated with either chemotherapy followed by a year of standard treatment with Roche's Herceptin and the newer drug, Perjeta, or with Herceptin and a placebo.
After three years, 93.2 percent of women on Herceptin alone had not developed invasive cancer compared with 94.1 percent of those given Perjeta - a difference of less than one percentage point. For patients whose disease had not spread to lymph nodes, Perjeta did not make a difference, the researchers said.
Both Perjeta and Herceptin are antibody drugs used for breast cancer patients whose tumors generate a protein called HER2, accounting for around 25 percent of breast cancer cases.
Cancer specialists said the early results indicate that doctors should consider adding Perjeta only for post-surgery patients with the worst prognosis - cancer that has spread to the lymph nodes or cancer not eligible for hormone therapies.
"For those patients who do have a worse anatomic prognosis, the combination is probably better than the single agent," said Dr. Bruce Johnson, chief clinical research officer at Boston's Dana-Farber Cancer Institute and the American Society of Clinical Oncology's (ASCO) incoming president.
Roche executives said the trial, slated to run for 10 years, will likely show a wider advantage for Perjeta over time.
Daniel O'Day, head of pharmaceuticals at Roche, estimated that 70 percent, or 350,000, of breast cancer patients are diagnosed as "high-risk," meaning their cancer has spread or does not respond to hormone therapy.
The U.S. list price for a one-year course of the Perjeta/Herceptin regimen in the post-surgery setting is around $158,000, while Herceptin alone costs around $74,500.
Serious side effects seen in the trial included heart failure or heart-related death in 0.7 percent of patients in the Perjeta group and 0.3 percent of the placebo group.
In March, Roche said the trial found that the Perjeta cocktail kept patients alive longer, but full details were released here on Monday at the annual ASCO meeting.
"It's clear this approach may not be advantageous for women with a lower risk for recurrence," said Dr. Harold Burstein, a clinical investigator at Dana-Farber's Breast Oncology Center, who was not involved in the study.
The study researchers said they are trying to find biomarkers that may predict which patients benefit from Perjeta as well as doing research to see if the length of treatment could be shortened to six months.
Herceptin, approved in 1998, is losing patent protection, exposing it to eventual competition. A partnership of Mylan NV and Biocon Ltd has filed for U.S. and European Union approval of their biosimilar version, while Celltrion Inc and Samsung Bioepis Co, a joint venture of Samsung Biologics Co and Biogen Inc, are each seeking approval in Europe.
Roche said it expects competition from biosimilar Herceptin in Europe late this year, but patent coverage will prevent a U.S. version until 2019. (Reporting by Deena Beasley; Editing by Phil Berlowitz)