This confirmatory efficacy and safety study was performed as the final step in assessing bioequivalence of a proposed trastuzumab biosimilar, Mylan®.

The anti-ERBB2 humanised monoclonal antibody trastuzumab (Herceptin®) is well known to improve of progression-free survival and overall survival in patients with ERBB2-positive breast cancer. However, trastuzumab is not widely available around the world, and a biosimilar treatment option may increase global access. This confirmatory efficacy and safety study was performed as the final step in assessing bioequivalence of a proposed trastuzumab biosimilar, Mylan®.

Development of biosimilars is a high priority for drug developers and health authorities throughout the world to provide access to high-quality alternatives to approved biologics including monoclonal antibodies. Trastuzumab (Herceptin®) is a monoclonal antibody that, in combination with chemotherapy, markedly improves survival in metastatic and early-stage HER2-positive breast cancer compared with chemotherapy alone. The Heritage Study was designed to compare efficacy, safety, and immunogenicity of a proposed biosimilar, Mylan®, versus reference trastuzumab, each combined with a taxane, in patients with HER2-positive metastatic breast cancer.

Findings

After 24 weeks’ treatment, overall response rate was 69.9% for the biosimilar and 64% for trastuzumab. This result was within the predefined equivalence boundaries for efficacy of the proposed biosimilar versus trastuzumab. There were no statistically significant differences between the two treatment groups for any of the secondary endpoints (time to tumour progression, progression-free survival, and overall survival at 48 weeks). Population pharmacokinetics parameters were comparable for the proposed biosimilar and trastuzumab, as were the respective safety profiles. There were no changes of left ventricular ejection fraction in any patients at week 24, and low immunogenicity was confirmed for both drugs.

This confirmatory safety and efficacy study demonstrated that 24-week treatment with proposed biosimilar, Mylan®, results in equivalent objective response rate compared with trastuzumab in women with HER2-positive metastatic breast cancer receiving taxanes. This clinically effective biosimilar may help increase access to trastuzumab therapy.

Key takeaway

The trastuzumab biosimilar Mylan® had similar efficacy, pharmacokinetic parameters, and safety profiles as the reference product. This may help increase access to trastuzumab therapy for patients with HER2-positive metastatic breast cancer.