The efficacy and safety of trastuzumab biosimilar HLX02 compared with reference trastuzumab plus pertuzumab in combination with chemotherapy as the first-line treatment for HER2 positive metastatic breast cancer: A real-world study in China.

e13016 Background: Dual-targeted anti-HER2 therapy with trastuzumab (H) and pertuzumab (P) significantly improves outcomes in HER2-positive breast cancer and has become the first-line standard treatment for patients with advanced HER2-positive breast cancer in China in 2019 based on the results of the CLEOPATRA and PUFFIN study. HLX02 (Zercepac) was the first trastuzumab biosimilar manufactured in China. Here, we present the first real-world comparison of HLX02 versus reference trastuzumab (RTZ) and pertuzumab with chemotherapy as the first-line treatment for HER2-positive metastatic China.Between January 2019 and August 2023, 121 patients with HER2-positive MBC patients were enrolled at Beijing Cancer Hospital in China. These patients received HLX02 or RTZ in combination with pertuzumab and various chemotherapies as first-line treatment. We retrospectively analyzed survival outcomes, efficacy, and adverse events. Methods: Between January 2019 and August 2023, 121 patients with HER2-positive MBC patients were enrolled at Beijing Cancer Hospital in China. These patients received HLX02 or RTZ in combination with pertuzumab and various chemotherapies as first-line treatment. We retrospectively analyzed survival outcomes, efficacy, and adverse events. Results: Both groups, 68 received RTZ and 53 received HLX02, showed similar characteristics of age, disease status (de novo or recurrent), metastatic sites (visceral or non-visceral), and treatment history. A total of 118 (97.5%) received trastuzumab plus pertuzumab combined with chemotherapy as the first-line palliative therapy, with a median number of 6 cycles in each group. Taxanes were the most commonly used chemotherapy regimen in both groups (91.2 vs. 92.5%), including nab-paclitaxel (44.1 vs. 45.3%), docetaxel (41.2 vs. 17.0%), paclitaxel (5.9 vs. 30.2%). With a median follow-up of 15.0 months (range 1.0 - 58.0), the results showed no significant difference in PFS between the RTZ and HLX02 arms (median PFS: 22.0 vs. 19.0 months, p=0.900). Additionally, the efficacy outcomes, including objective response rate (ORR), disease control rate (DCR), and safety profiles did not show significant differences between the two groups. Among 121 patients, 20 patients (16.5%) experienced CNS progression. For these patients, the median time from the first-line therapy to the CNS progression was 15.0 months (95% CI 12.8 - 17.2). Conclusions: The real-world data suggest similar efficacy and safety of HLX02 and RTZ plus pertuzumab with different chemotherapy regimens as the first-line treatment for patients with HER2-positive advanced breast cancer patients in China. Overall, the PFS was consistent with the CLEOPATRA trial in both groups, and there was no new safety signal.