Neoadjuvant inetetamab combined with pertuzumab, paclitaxel, and carboplatin (TCbIP) for locally advanced HER2-positive breast cancer: Primary analysis of a phase II study.

Abstract

e12597 Background: Inetetamab (Cipterbin) is a neotype HER2-targeted monoclonal antibody with amino acids modified Fc segment which optimizes the antibody-dependent cellular cytotoxicity (ADCC) effect. Unfortunately, no robust evidence evaluating the combination of inetetamab combined with pertuzumab, paclitaxel and carboplatin (TCbIP) exists for neoadjuvant therapy. This study aimed to evaluate the efficacy and safety of TCbIP as a neoadjuvant therapy of patients with locally advanced (LA) HER2-positive breast cancer. Methods: This phase II trial included patients with histologically confirmed stage IIA to IIIC HER2-positive primary invasive breast cancer. Eligible patients receive TCbIP treatment every 3 weeks for a maximum of 6 cycles, followed by surgery. 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. Efficacy was analyzed in the intention-to-treat (ITT) and per-protocol (PP) populations. The ITT population included patients who received at least 2 cycles of TCbIP treatment but excluded those who were lost to follow-up without surgery and those who received other targeted therapy. The PP population included patients who met all the trial criterias, complianted with the protocol, and did not violate any major protocol. The safety population included all patients who received at least one dose of the study drugs and had available safety data. Results: A total of 24 patients were enrolled from November 2021 to February 2023. Of 24 patients, 1 patient received 1 cycle of study treatment and was lost to follow-up without surgery, and 4 patients received 1 cycle of study treatment and were still in treatment, leaving 19 patients in the ITT population. Among 19 patients in the ITT population (median age, 50 years; 78.9% in stage III), 12 patients completed the study treatment and surgery (PP population) and 7 patients were still in neoadjuvant treatment. ORR was achieved 78.9% in the ITT population (15 of 19 patients) and 91.7% in the PP population (11 of 12 patients). Among 12 patients of PP population, 8 patients (66.7%) achieved pCR and 10 patients (83.3%) achieved npCR. For patients with hormone receptor negative and positive tumors, the pCR rates were 71.4% (5/7) and 60.0% (3/5) ( P = 0.771), and the npCR rates were 85.7% (6/7) and 80.0% (4/5) ( P = 0.793), respectively. The most common grade ³3 adverse events were hair loss (41.7%) and neutropenia (12.5%). No significant reduction in the left ventricular ejection fraction was observed in any patient. No patients withdrew from the treatment due to adverse drug reactions. Conclusions: TCbIP displays a promising efficacy (pCR rate of 66.7%) and manageable toxicity in patients with HER2-positive LA breast cancer in the neoadjuvant setting. Clinical trial information: NCT05749016 .