e12592 Background: Although neoadjuvant chemotherapy (NAC) is currently the best therapy for triple-negative breast cancer (TNBC), resistance still occurs in a considerable proportion of TNBC patients, making it crucial to understand resistance mechanisms and identify predictive biomarkers for patient selection. Methods: Biopsy samples were collected from 21 patients with TNBC who underwent NAC. Whole-exome sequencing, targeted sequencing, and multiplex immunohistochemistry (mIHC) were carried out on the all clinical samples and used to identify and validate potential biomarkers associated with response to NAC. In addition, data on 190 TNBC patients who had undergone chemotherapy were obtained from The Cancer Genome Atlas (TCGA) and analyzed to further validate our findings. Results: Both the tumor mutational burden (TMB) and tumor neoantigen burden (TNB) were significantly higher in responders than in non-responders. Higher response rates and longer survival rates were observed in patients with higher TMB. Patients with higher ratios of CD8 to M2 macrophages had higher response rates and improved survival rates. Finally, integrated analysis demonstrated that the combination of TMB and the ratio of CD8 T cells to M2 macrophages could further distinguish responders from non-responders in both enrolled patients and from public data. Conclusions: The findings of this study indicated that the combination of TMB and the ratio of CD8 T cells to M2 macrophages may be a potential biomarker for improving the recognition of NAT responders, thereby providing a basis for developing precision NAT regimens.