CHICAGO — MYL-1401O, a biosimilar trastuzumab antibody, is comparable in efficacy and safety to the anti-HER2 monoclonal antibody trastuzumab as frontline therapy in patients with advanced, HER2-positive breast cancer, researchers reported at the 2016 American Society of Clinical Oncology (ASCO) Annual Meeting.1

The Food and Drug Administration considers a biosimilar to be a biologic product that is highly similar to an already approved product in regard to potency, safety, and purity. To date, no biosimilars for the treatment of cancer have been approved in the United States; however, filgrastim-sndz was approved last year as a biosimilar to filgrastim.

The phase 3 HERITAGE study  enrolled 500 patients with centrally confirmed, measurable HER2-positive metastatic breast cancer who had not received prior chemotherapy or trastuzumab for metastatic disease. Participants were randomly assigned 1:1 to receive MYL-1401O or trastuzumab in addition to docetaxel or paclitaxel for at least 8 cycles, followed by trastuzumab alone until disease progression.

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Data indicated that the objective response rate at 24 weeks was 69.6% with the biosimilar compared with 64% with trastuzumab. The rates of serious adverse events were 38% and 34%, respectively. The most frequently reported serious adverse event was neutropenia in both arms, and there was no difference in the incidence of cardiotoxicity in either group. Of note, 4 treatment-related deaths occurred in each group.

“To our knowledge, this is one of the first clinical trials to show equivalency of a trastuzumab biosimilar to the branded cancer drug,” said lead study author Hope S. Rugo, MD, a Professor of Medicine at the University of California, San Francisco.

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“Trastuzumab has markedly improved survival of women with HER2-­positive breast cancer, but many women around the world can’t benefit from trastuzumab due to its high cost,” said Dr Rugo. “We hope that the introduction of biosimilars will expand patient access to this effective drug, which has already benefited the lives of thousands of people across the globe.”


  1. Rugo HS, Barve A, Waller CF, et al. Heritage: A phase III safety and efficacy trial of the proposed trastuzumab biosimilar Myl-1401O versus Herceptin. J Clin Onco. 2016; 34 (suppl; abstr LBA503).