Abstract PO1-04-04: Inetetamab combined with pyrotinib and oral vinorelbine for patients with HER2-positive metastatic breast cancer: a single-arm phase 2 trial

Abstract Aim: The efficacy and safety of inetetamab in combination with pyrotinib and oral vinorelbine was investigated in patients with human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer. Methods: In this prospective, single-arm, phase 2 trial, patients with HER2-positive metastatic breast cancer after progression on trastuzumab were recruited. Patients received combined treatment of inetetamab (loading dose of 8 mg/kg, subsequent doses 6 mg/kg, intravenously once every 3 weeks) plus pyrotinib (400 mg orally once daily) plus vinorelbine (60 mg/m2 orally once weekly) until disease progression or intolerable toxicity. The primary endpoint was progression free survival (PFS). Secondary endpoints included objective response rate (ORR), overall survival (OS), disease control rate (DCR) and safety. The study was retrospectively registered in ClinicalTrials.gov on March 23rd, 2023. The registration number is NCT05823623. Results: Between Jan 1, 2022, and Dec 31, 2022, thirty patients were screened and enrolled to this study. The patients’ median age at enrollment was 54 years, twelve patients (40.0%) had hormone receptor-positive disease and 23 patients (76.7%) had visceral metastasis. The median PFS was 8.63 months (95% confidence interval CI 4.15 to 13.12 months). ORR was 53.3% (16/30) and DCR reached 96.7% (29/30). The most common grade III/IV adverse events included leukopenia (516.7%), neutropenia (413.3%) and diarrhea (310%). No treatment-related serious adverse events or treatment-related deaths occurred. Conclusions: The combination regimen of inetetamab plus pyrotinib plus oral vinorelbine showed an encouraging efficacy and favorable safety in patients with HER2 positive metastatic breast cancer. Citation Format: Xiang Huang, Nan Jin, Chunxiao Sun, Xueqi Yan, Fan Yang, Yan Liang, Wei Li, Yongmei Yin. Inetetamab combined with pyrotinib and oral vinorelbine for patients with HER2-positive metastatic breast cancer: a single-arm phase 2 trial abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-04-04.