e12613 Background: The chemotherapy-free neoadjuvant regimens of dual HER2 blockade has showed encouraging rates of pathological complete response (pCR) in patients with HER2-positive breast cancer. Additionally, combining cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors with anti-HER2 therapy has shown synergistic effects in hormone receptor (HR)-positive and HER2-positive breast cancer. However, there is limited data regarding this combination strategy in HR-negative/HER2-positive settings. The objective of this study was to evaluate the efficacy and safety of a chemotherapy-free regimen consisting of the CDK4/6 inhibitor dalpiciclib, and dual anti-HER2 components of pyrotinib and trastuzumab in patients with HR-negative/HER2-positive early breast cancer (EBC). Methods: This open-label, single-arm, phase II study was designed using the Simon two-stage method (Registration number: Chi-CTR-2200060748). Patients with HR-negative/HER2-positive operable EBC (tumor stage T1-3 and nodal stage N0-2) were enrolled. Eligible patients received trastuzumab (HLX02, 8 mg/kg loading dose, followed by 6 mg/kg every 3 weeks intravenously) for 15 weeks, plus pyrotinib (240 mg daily orally) and dalpiciclib (125 mg daily orally for 3 weeks, followed by 1 week off) for 16 weeks. Surgery was performed 3-6 weeks after the completion of the last cycle of study treatment. The primary endpoint was pCR (ypT0/Tis ypN0) at surgery, and secondary endpoints included objective response rate (ORR), change of Ki-67 labeling index, biomarker analysis, survival and safety. Results: Between Jun 24, 2022, and Sept 14, 2023, a total of 30 patients with a median age of 54.5 years (range: 35-66) were enrolled and treated in this ongoing trial. As of the data cutoff date on Jan 20, 2024, 26 patients underwent surgery, and pCR was achieved in 18 (69.2%) cases. Out of the 29 patients with evaluable response, 26 achieved partial response and 3 achieved stable disease, resulting in an ORR of 89.7%. The most common grade 3 or more treatment-related adverse events (AEs) were diarrhea (66.7%), decreased neutrophil count (33.3%), and decreased white blood cell count (20.8%). Most AEs were tolerable, and no treatment-related deaths occur. Conclusions: In patients with HR-negative/HER2-positive EBC, a dual HER2-targeted combination of pyrotinib and trastuzumab, along with dalpiciclib in the absence of chemotherapy showed promising efficacy with encouraging pCR and ORR rates, as well as a favorable safety profile in the neoadjuvant setting. Clinical trial information: Chi-CTR-2200060748.