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Longest Follow-Up Data on Trastuzumab Biosimilar Presented at 2021 SABCS

05:00 PM ON DEC 8, 2021 CT

• Five-year follow-up results reconfirm comparable long-term efficacy of SB3 (ONTRUZANT®, trastuzumab-dttb) versus Herceptin® through additional analysis with a larger group of patients with HER2-positive early or locally advanced breast cancer.

INCHEON, Korea – December 8, 2021 – Samsung Bioepis Co., Ltd. today announced that SB3 (ONTRUZANT®, trastuzumab-dttb), a biosimilar to Herceptin® (trastuzumab), demonstrated comparable long-term survival results between SB3 and reference trastuzumab (TRZ) after a median follow-up of 68 months from the randomization of the SB3 Phase 3 study. These five-year results are known to be the longest monitored data to date, as of December 2021, for a trastuzumab biosimilar used in patients with HER2-positive early or locally advanced breast cancer. These data were presented during the 2021 San Antonio Breast Cancer Symposium, which is taking place both in-person in San Antonio, Texas, and virtually, from December 7 to 10, 2021. 

The cardiac safety and efficacy results after a median 68-month follow-up with 367 patients who participated in the same study were presented at the European Society for Medical Oncology (ESMO) Congress held in September 2021.  Additional analysis results presented at the 2021 SABCS assessed five-year follow-up survival results in a larger group of patients, which included additionally enrolled 171 patients, and also included subgroup analyses based on which TRZ lots (“Drifted”  or “Non-drifted” ) patients were treated with.

The survival analysis showed that five-year event-free survival (EFS) was comparable between SB3 and TRZ group, with EFS rate of 79.8% and 75.0% for each group, respectively. (Hazard Ratio [HR] 0.84, 95% Confidence Interval [CI]: 0.58-1.20, p=0.335) The five-year overall survival (OS) was also comparable, with OS rate of 92.5% for SB3 group and 85.4% for TRZ group. (HR 0.61, 95% CI: 0.36-1.05, p=0.073). 

When SB3 was compared with “Non-drifted” TRZ in the post-hoc analysis, EFS was comparable between two groups, with SB3 showing EFS rate of 79.8% and the “Non-drifted” TRZ group showing 82.5% rate (HR 1.28, 95% CI: 0.73-2.22, p=0.391). Similar outcome was observed in OS as well, with SB3 and the “Non-drifted” TRZ group showing OS rate of 92.5% and 91.4%, respectively (HR 0.99, 95% CI: 0.42-2.31, p=0.975). However, there was a meaningful difference within TRZ arm depending on the ADCC-drift status; the five-year EFS for "Drifted" and "Non-drifted" TRZ group was 70.3% and 82.5%, respectively (HR 2.57, 95% CI: 1.28-5.14, p=0.008), while OS for each group was 81.3% and 91.4%, respectively (HR 3.87, 95% CI: 1.37-10.93, p=0.011).

“For HER2-positive breast cancer treatment, monitoring long-term outcome is important, and we hope these five-year follow-up study results in a large group of patients provide meaningful value to the oncology society by demonstrating robust comparable long-term safety and efficacy profile of a trastuzumab biosimilar,” said Dong-hoon Shin, Vice President and Medical & Lifecycle Safety Team Leader, Samsung Bioepis. He continued, “We will continue to do our part to bring updated clinical and real-world evidence on biosimilars to the medical society so that health care providers and patients feel confident when using biosimilars for treatment of oncologic conditions.”

The final five-year follow-up results of the Phase 3 study for SB3 (ONTRUZANT®, trastuzumab-dttb) were presented at the 2021 SABCS as follows:
Abstract title: Final survival analysis of a Phase 3 study comparing SB3 (trastuzumab biosimilar) and reference trastuzumab
        in HER2-positive early or locally advanced breast cancer
Abstract number: P2-13-04
Format: poster presentation
Time and Date: Wednesday, December 8, 2021, 5:00 pm – 6:30 pm Central Time (CT)
Authors: Xavier Pivot, Mark Pegram, Javier Cortes, Diana Lüftner, Gary Lyman, et al.

In the United States, SB3 was first approved as a 150 mg single-dose vial by the U.S. Food and Drug Administration under the brand name ONTRUZANT® (trastuzumab-dttb) in January 2019, and as a 420 mg multi-dose vial in March 2020. The product is being marketed in the United States by Organon.

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About the SB3 Phase 3 Study
The five-year follow-up of the Phase 3 study evaluated SB3 and TRZ in patients with HER2 positive early or locally advanced breast cancer for comparable cardiac safety profiles, and efficacy at 4 years after randomization in the Phase 3 study. Of 875 patients randomized in the Phase 3 study, 367 patients (SB3, N=186; TRZ, N=181) were enrolled in the follow-up study and were randomly assigned to receive 8 cycles of either SB3, or TRZ with concurrent neoadjuvant chemotherapy (4 cycles of docetaxel followed by 4 cycles of 5-fluorouracil/epirubicin/cyclophosphamide). Patients then underwent surgery followed by 10 cycles of SB3 or TRZ according to the previous treatment allocation to complete 1 year of treatment. After completing the adjuvant treatment, patients from selected countries were asked for consent to enroll in a five-year follow-up study. 

During the follow-up study, the protocol was amended to include additional patients who originally were enrolled in the Phase 3 study but had not been followed in the observational study, in order to collect a larger sample of survival data, and 171 patients were additionally enrolled. For post-hoc analysis, 271 patients in the TRZ arm were stratified into two subgroups (Drifted, N=164; Non-drifted, N=107). Efficacy endpoints were EFS and OS; EFS was defined as the time from the date of randomization to the date where an event (disease recurrence, progression, or death) occurred, and OS was defined as the time from the date of randomization to the date of death. EFS and OS were estimated by treatment groups and subgroups using the Kaplan-Meier method; hazard ratio with 95% CI from stratified Cox regression model.

About Samsung Bioepis Co., Ltd.
Established in 2012, Samsung Bioepis is a biopharmaceutical company committed to realizing health care that is accessible to everyone. Through innovations in product development and a firm commitment to quality, Samsung Bioepis aims to become the world's leading biopharmaceutical company. Samsung Bioepis continues to advance a broad pipeline of biosimilar candidates that cover a spectrum of therapeutic areas, including immunology, oncology, ophthalmology, hematology, endocrinology, and gastroenterology. For more information, please visit: and follow us on social media – Twitter, LinkedIn.

Anna Nayun Kim, Global Communications, Samsung Bioepis