Proposed trastuzumab biosimilar MYL-1401O demonstrated equivalent activity compared with trastuzumab among women with metastatic breast cancer, according to a study published in JAMA.1

Although biological agents like trastuzumab and rituximab have substantially improved outcomes for a variety of cancers, patient access to these immunotherapies is hindered by high costs. With patents expected to expire for some of these drugs, drug developers and health authorities have prioritized the development of biosimilars, a biological product highly similar to a licensed biological drug with no clinically meaningful differences with respect to potency or safety.

To evaluate the activity and safety of the proposed trastuzumab biosimilar MYL-1401O, researchers enrolled 458 women with previously untreated ERBB2 (HER2)-positive metastatic breast cancer and randomly assigned them to receive MYL-14010 or trastuzumab with a taxane. Patients received chemotherapy for at least 24 weeks followed by the biological agent alone until disease progression or unacceptable toxicity.

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Results of the phase 3 HERITAGE trial ( Identifier: NCT02472964) showed that 69.6% (95% CI, 63.62-75.51) of patients given the proposed biosimilar and 64.0% (95% CI, 57.81-70.26) of those who received trastuzumab achieved an overall response by week 24.

At week 48, researchers observed no statistically significant difference in time to tumor progression, progression-free survival, or overall survival between the proposed biosimilar arm and the trastuzumab arm.

In the proposed biosimilar and trastuzumab groups, 99% and 95% of patients reported at least 1 adverse event, respectively. The most common adverse events were neutropenia, peripheral neuropathy, and diarrhea in both arms.

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The findings suggest that MYL-1401O may represent an alternative to trastuzumab that is sufficiently inexpensive to enable women in non-high-income countries to access this therapy, though the authors noted that additional safety and long-term clinical outcome data are needed.


  1. Rugo HS, Barve A, Waller CF, et al. Effect of a proposed trastuzumab biosimilar compared with trastuzumab on overall response rate in patients with ERBB2 (HER2)–positive metastatic breast cancer. JAMA. 2016 Dec 1. doi: 10.1001/jama.2016.18305 [Epub ahead of print]