331P - Neoadjuvant intetamab in combination with standard chemotherapy for locally advanced HER2-positive breast cancer

Background

Inetetamab is a novel anti-HER2 monoclonal antibody with modified Fc segment region, optimized production process, and enhanced antibody-dependent cellular cytotoxicity effect. There is currently a lack of reliable evidence to evaluate the treatment of inetetamab in combination with chemotherapy for neoadjuvant treatment. This study aims to evaluate the efficacy and safety of inetetamab combined with pertuzumab, paclitaxel, and carboplatin (TCbIP) as neoadjuvant therapy for HER2-positive locally advanced breast cancer (LABC) patients.

Methods

This phase II trial included female patients with histologically confirmed stage IIA to IIIC HER2-positive primary invasive breast cancer. Eligible patients received TCbIP treatment once every three weeks. The maximum number of treatment cycles, ranging from six to eight, was determined by the efficacy assessment conducted by the physician, after which surgery was performed. The primary endpoint was pathologic complete response (pCR, ypT0/is ypN0) rate. Key secondary endpoints included near-pCR (npCR, residual breast disease <1cm) rate, objective response rate (ORR) and safety.

Results

From November 2021 to April 2024, 49 patients were enrolled in the trial. In the population capable of efficacy and safety assessment (44 pts, 86.4% in stage III), 39 patients completed the study treatment and surgery (PP population) and five patients were still undergoing neoadjuvant treatment. The ORR and pCR was 92.3% (36/39) and 53.8% (21/39) in the PP population. For patients with hormone receptor (HR) negative and positive tumors, the pCR rates were 77.8% (14/18) and 33.3% (7/21), respectively. A total of five patients (12.8%) achieved near-pCR. The most common grade 3 adverse event was neutropenia (19.0%). No significant reduction in left ventricular ejection fraction was observed.

Conclusions

Administering the TCbIP regimen prior to surgery for HER2-positive LABC patients has led to favorable therapeutic outcomes with toxicity that are within a manageable scope.

Clinical trial identification

NCT05749016.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.