Questions remain regarding cost of trastuzumab biosimilar, role in combination with pertuzumab

The biosimilar trastuzumab antibody MYL-1401O appeared to have comparable safety and efficacy to its FDA–approved reference product, indicating that the biosimilar “is the therapeutic equivalent to trastuzumab as a single agent,” according to Adam M. Brufsky, MD, PhD, professor of medicine, associate chief of hematology/oncology and co-director of the comprehensive breast cancer center at the University of Pittsburgh.

Results of the randomized, phase 3 HERiTAge trial presented at the ASCO Annual Meeting included data from 458 women treated at 95 sites worldwide. Hope S. Rugo, MD, professor of medicine at the University of California, San Francisco, and colleagues randomly assigned patients to receive MYL-1401O (Mylan Inc.; n = 230) or trastuzumab (n = 228) with docetaxel or paclitaxel every 3 weeks for at least eight cycles. All participants had HER-2–positive, metastatic breast cancer.

Adam M. Brufsky

Overall response rate at week 24 served as the primary endpoint. Secondary endpoints included PFS, OS and safety.

At week 24, ORR was 69.6% for MYL-1401O and 64% for trastuzumab. Median PFS had not yet been reached at the time of the presentation.

Safety appeared comparable between treatment arms, with no significant changes in cardiac function in either cohort. Serious adverse events — which were primarily hematologic and related to taxane therapy — occurred in 38.1% of those assigned the biosimilar and 36.2% of those assigned the reference product.

“The clinical course of these patients was identical, and there were very few additional side effects with the biosimilar,” Brufsky said.

Moving forward, questions regarding cost and the ways in which the biosimilar interacts with other monoclonal antibodies will need to be addressed, according to Brufsky, who is also a HemOnc Today editorial board member.

“The study will lead to adoption of this therapy,” he said. “I think, really, it’s going to be a cost issue now. Hopefully, in areas of the world where the cost of trastuzumab is an issue, this may be an option for the treatment of HER-2–positive, metastatic breast cancer.”

In addition, it remains to be seen how the agent interacts with other monoclonal antibodies, particularly pertuzumab (Perjeta, Genentech), according to Brufsky.

“This will need to be explored, because most of the regimens now for first-line therapy for metastatic breast cancer involve pertuzumab, with a significant PFS as well as OS benefit,” he said. – by Julia Ernst, MS

Reference:

Rugo HS, et al. Abstract LBA503. Presented at: ASCO Annual Meeting; June 3-7, 2016; Chicago.

Disclosures: Brufsky and Rugo report no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.