Breast cancer biosimilar shows equivalency to brand

Two new major studies on a biosimilar to trastuzumab (Herceptin, Genentech) to treat HER2-positive metastatic breast cancer and HER2-positive gastric cancer demonstrated equivalency.

In the Heritage study, published in JAMA online December 1, researchers also found that “a potential biosimilar”-which was not named-to Herceptin was equivalent.

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The objective response rate (ORR) was 69.6% for the proposed biosimilar versus 64% for trastuzumab. The ORR ratio and the ORR difference were within the equivalence boundaries, wrote the researchers from the University of California-San Francisco and universities in several countries, including India, Thailand, Russia and the Philippines.

At week 48, there was no statistically significant difference with the proposed biosimilar versus Herceptin for time to tumor progression (41.3% versus 43%), progression-free survival (44.3% versus 44.7%) or overall survival (89.1% versus 85.1%). In the proposed biosimilar and Herceptin groups, 98.6% and 94.7% had at least one adverse event, the most common including neutropenia, peripheral neuropathy and diarrhea.

“The data from the Heritage study demonstrate that the proposed trastuzumab biosimilar meets the criteria for establishing equivalence with trastuzumab. In answer to the proverbial question ‘Would you use the trastuzumab biosimilar for your mother if she had ERBB2-positive breast cancer?’, the answer should be ‘Yes’,” wrote Harold J. Burstein, MD, associate professor of medicine at Harvard Medical School and Deborah Schrag, MD, associate editor of JAMA in an editorial accompanying the study.

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In a separate study, Pfizer said its double-blind clinical trial of the investigational biosimilar drug, PF-05280014,  demonstrated equivalence in the primary end point of objective response rate (ORR) of PF-05280014 versus Herceptin, taken in combination with paclitaxel, in first line patients with HER2-positive metastatic breast cancer.

“Favorable comparative clinical data between proposed biosimilars and their respective reference product contribute to physician and patient understanding of and confidence in the value and importance of biosimilars,” said Sumant Ramachandra, MD, PhD, head of research and development for Pfizer Essential Health. “We are encouraged by these data and look forward to sharing the complete results with health authorities and the oncology community once available.”

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