New Long-term Safety and OS Data for Trazimera Show Similarity to Reference Trastuzumab

Pfizer gained FDA approval for its biosimilar trastuzumab, Trazimera, in March 2019, and is slated to launch in the United States on February 15, 2020. Ahead of that milestone, researchers last week reported long-term safety and overall survival (OS) data for the Herceptin biosimilar in patients with HER2-positive metastatic breast cancer.

During the San Antonio Breast Cancer Symposium in San Antonio, Texas, a research team reported findings from the study, a multinational, randomized, double-blind, parallel-group study of the biosimilar in comparison with EU-licensed reference Herceptin, each in combination with paclitaxel for the first-line treatment of HER2-positive metastatic breast cancer.

The equivalence between the biosimilar and the reference was previously demonstrated for the primary end point of objective response rate, evaluated at week 25 and confirmed at week 33; the new data report the cumulative safety and OS data up to year 5 after the first patient’s screening.

At the time of the data cutoff, February 25, 2019, 83 (11.7%) of the 707 randomized patients continued in the study. Of these patients, 41 received the biosimilar and 42 received the EU reference product.

The most frequent reason for discontinuing trastuzumab was objective progression (69.6% of the biosimilar group and 69.0% of the reference group). Estimated median time to discontinuation was 12.25 months for the biosimilar group and 12.06 months for the reference group (stratified hazard ratio [HR], 1.014; 95% CI, 0.867-1.186; P = .569).

In total, 16.5% of patients in the biosimilar group and 18.9% in the reference group died during the period studied; there was no statistically significant difference in OS (stratified HR, 0.888; 95% CI, 0.624-1.264; P =.254). Estimated 2- and 3-year survival rates were 82.26% and 77.17% for those receiving the biosimilar and 77.50% and 75.33% for those receiving the reference.

No notable differences in treatment-emergent adverse events (AEs), including grade 3 or higher events or serious AEs, were observed. Rates of cardiac failure, infusion-related reactions, and decreased ejection fraction were similar between groups.

According to the authors, these long-term data are consistent with previous results in the ongoing study, underscoring the fact that the biosimilar and its reference have no clinically meaningful differences.

Reference

Li RK, Lipatov O, Adamchuk H, et al. Trazimera (a trastuzumab biosimilar) in HER2-positive metastatic breast cancer: long-term safety and overall survival data. Presented at: San Antonio Breast Cancer Symposium, December 10-14, 2019; San Antonio, TX. Abstract P1-18-08.