Fovinaciclib Plus Aromatase Inhibitors and Dual HER2 Blockade in a Response-Adapted Neoadjuvant Strategy for HR-Positive/HER2-Positive Early Breast Cancer

This is a prospective, response-adapted, phase II study designed to evaluate an individualized neoadjuvant treatment strategy based on fovinaciclib in combination with aromatase inhibitors and dual HER2 blockade in patients with HR-positive/HER2-positive early breast cancer. The study incorporates an adaptive treatment algorithm guided by early on-treatment assessment of tumor response, with the aim of optimizing therapeutic efficacy while minimizing unnecessary chemotherapy exposure. All eligible patients initially receive neoadjuvant treatment with fovinaciclib plus endocrine therapy and HER2-targeted therapy according to the study protocol. Following completion of the predefined initial treatment phase, tumor response is assessed according to protocol-defined evaluation methods. Patients who achieve an adequate response continue the same neoadjuvant regimen to complete the planned course of therapy. In contrast, patients demonstrating a suboptimal response are transitioned to standard neoadjuvant chemotherapy combined with HER2-targeted therapy prior to surgery. Postoperative treatment selection and management are conducted according to protocol-defined principles and investigator assessment. By tailoring treatment intensity according to early response, the study seeks to maximize therapeutic benefit in responsive patients while facilitating timely treatment modification for those less likely to benefit from the initial regimen. Primary and secondary objectives include evaluation of clinical efficacy, safety and tolerability of the response-adapted neoadjuvant strategy, and the feasibility of treatment modification based on early response assessment. Exploratory analyses will investigate potential biomarkers associated with treatment response and resistance, with the goal of informing future individualized treatment approaches.