SB3 Shows Comparable Efficacy and Safety to Reference Trastuzumab at 1 Year

Samsung Bioepis has announced that a 1-year follow-up study comparing event-free survival (EFS) in patients treated with SB3, a biosimilar trastuzumab (approved in Europe as Ontruzant) showed that the biosimilar has similar safety and efficacy profiles to the reference Herceptin.

The study results, presented in an abstract at the 2018 San Antonio Breast Cancer Symposium, held in San Antonio, Texas, from December 4 to 8, 2018, reported on a study of patients with HER2-positive early breast cancer or locally advanced breast cancer who were randomized to receive either the biosimilar or its reference concurrently with chemotherapy.

Patients underwent surgery, then received treatment with either SB3 or its reference. Afterward, 367 patients—181 of whom had been treated with the reference trastuzumab and 186 of whom had been treated with SB3—were enrolled in a long-term follow-up study.

Within the group of patients treated with the reference, 126 patients had been exposed to lots of trastuzumab, with expiry dates from August 2018 to December 2019, that had a lower antibody-dependent cell-mediated cytotoxicity (ADCC) than other lots of the reference product. The remaining 55 patients given the reference therapy were unexposed to these lots.

After 30.1 months of treatment with the biosimilar and 30.2 months of treatment with the reference, there was no statistically significant difference in EFS between the biosimilar arm (96.7%) and the patients who were unexposed to the lower-ADCC activity lots of the reference (98.2%) (hazard ratio [HR], 1.19; 95% CI, 0.23-6.18; P = .8376). However, there was a statistically significant difference in EFS between the unexposed and exposed (92.5%) patients taking the reference drug (HR, 0.07; 95% CI, 0.01-0.58; P = .0137).

Furthermore, while no statistically significant difference in events (defined as disease recurrence, progression, or death) emerged between the SB3 arm (4.8%) and the unexposed reference arm (3.6%), there was a difference in events between the unexposed and exposed (10.3%) reference arms.

"This study builds on the robust evidence for SB3, and demonstrates the trastuzumab biosimilar candidate's comparable efficacy and safety profiles to the reference biologic over a longer time period," said Chul Kim, senior vice president and head of clinical science at Samsung Bioepis, in a statement. "We remain committed to advancing our strong pipeline of biosimilar candidates, so that more patients and healthcare systems may be able to benefit from biosimilar medicines."

Reference

Pegram MD, Pivot X, Cortes J, et al. Event-free survival by ADCC status from a follow-up study comparing SB3 (trastuzumab biosimilar) with reference trastuzumab for HER2 positive breast cancer in neoadjuvant setting. Presented at the 2018 San Antonio Breast Cancer Symposium, December 408, 2018; San Antonio, Texas. Abstract P6-17-09. https://www.sabcs.org/Program/Poster-Sessions/Poster-Session-6.