Abstract
BACKGROUND: We explored the efficacy and safety of inetetamab combined with sirolimus and chemotherapy for the treatment of human epidermal factor receptor 2 (HER2)-positive metastatic breast cancer patients with abnormal activation of the PI3K/Akt/mTOR (PAM) pathway after trastuzumab treatment. METHODS: For this prospective multicenter clinical study, HER2-positive metastatic breast cancer patients with PAM pathway mutations confirmed by histology or peripheral blood genetic testing were enrolled from July 2021 to September 2022. Patients were randomly assigned to a trial or control group. The patients in the trial group received inetetamab combined with sirolimus and chemotherapy, while the control group patients received pyrotinib and chemotherapy. The RECIST v1.1 standard was used to evaluate efficacy. Descriptive statistics were used to summarize the clinicopathological features, and the Kaplan-Meier method was used to generate survival curves. The log-rank test was used to compare progression-free survival (PFS) between the two groups. RESULTS: A total of 59 HER2-positive metastatic breast cancer patients with abnormal activation of the PAM pathway were included, of which 37 received inetetamab combined with sirolimus and chemotherapy treatment and 22 received pyrotinib and chemotherapy treatment. The median PFS was 4.64 months in the inetetamab group and 5.69 months in the pyrotinib group, with no statistically significant difference (p = 0.507). The objective response rates were 27.3% for the inetetamab group and 29.4% for the pyrotinib group. The safety assessment indicated that the adverse event (AE) incidences were 86.1% (31/36) in the inetetamab group and 78.9 (15/19) in the pyrotinib group, with 9 (25%) and four (21.1%) Grade 3/4 AEs in the inetetamab and pyrotinib groups, respectively. CONCLUSIONS: For metastatic HER2-positive breast cancer patients with abnormal PAM pathway activation and previous trastuzumab treatment, the combination of inetetamab with sirolimus and chemotherapy is equivalent to the combination of pyrotinib and chemotherapy. Therefore, this regimen could be a treatment option for PAM pathway-activated metastatic HER2-positive breast cancer patients.