Efficacy, safety and exploratory analysis of neoadjuvant tislelizumab (a PD-1 inhibitor) plus nab-paclitaxel followed by epirubicin/cyclophosphamide for triple-negative breast cancer: a phase 2 TREND trial

The optimal chemotherapy backbone and specific population of triple-negative breast cancer (TNBC) patients that benefit from neoadjuvant immunotherapy are not well established. This prospective, single-arm, phase II TREND trial assessed the efficacy and safety of tislelizumab plus nab-paclitaxel and epirubicin/cyclophosphamide-based chemotherapy as a neoadjuvant treatment for TNBC (ChiCTR2000035262). The primary endpoint was pathological complete response (pCR), with the secondary endpoints including safety assessment and objective response rate (ORR). ScRNA-seq, bulk RNA-seq, TCR-seq, cyTOF and WES were performed on pre-treatment and post-treatment samples. Among 53 total enrolled patients, 44 completed the combined neoadjuvant therapy, and 30 of 44 patients (68.18%) achieved pCR. Additionally, 14 out of 44 patients had a complete response (31.82%), with an ORR of 93.18%. The most commonly observed treatment-related adverse events (TRAEs) were alopecia, nausea and liver injury with 6 cases classified as grade 3 or higher adverse events. Immune response-related pathways, including TNF signaling pathway, T cell receptor signaling pathway, were enriched in pCR group. Pre-treatment model was identified and construct to predict response to immunotherapy. CDKN1A+ CD8 T lymphocytes were enriched in pCR group after neoadjuvant immunotherapy. Dynamic change of immune-related pathways at an early stage during the neoadjuvant immunotherapy may be associated with the treatment efficacy. In conclusion, neoadjuvant treatment of tislelizumab with nab-paclitaxel and anthracycline-based chemotherapy showed promising clinical activity and was well-tolerated among TNBC patients, without high incidence of TRAEs. These findings provide evidence supporting neoadjuvant tislelizumab with chemotherapy as an effective rational approach for treating TNBC.