Sino Biopharmaceutical Limited (SBP Group) reported that Phase II study TQB3616-II-04 of culmerciclib (TQB3616, brand name 賽坦欣®) combined with fulvestrant met its primary endpoint in hormone-receptor-positive, HER2-negative advanced breast cancer previously treated with CDK4/6 inhibitors. The findings were presented at the 2026 American Society of Clinical Oncology Annual Meeting.
The multicenter, single-arm trial enrolled 35 patients as of 15 April 2026, with a median follow-up of 10.8 months. The cohort reflected real-world post-resistance characteristics: median age 56 years and 71.40 % with visceral metastases (liver 45.70 %, lung 45.70 %, brain 5.70 %). All participants had progressed on prior CDK4/6 inhibitor plus endocrine therapy, and 37.10 % had also received chemotherapy.
Among 34 evaluable patients, the confirmed objective response rate reached 32.40 % (95 % CI: 17.40–50.50; p < 0.0001). Disease control rate was 88.20 % (95 % CI: 72.60–96.70) and clinical benefit rate stood at 82.40 % (95 % CI: 65.50–93.20). Median time to response was 3.7 months. Median progression-free survival and duration of response had not been reached; the 10-month PFS rate was 61.80 % (95 % CI: 42.30–76.40).
Safety remained consistent with prior studies. Grade ≥ 3 treatment-related adverse events occurred in 40.00 % of patients, while grade ≥ 3 neutropenia—a common concern with conventional CDK4/6 inhibitors—was limited to 5.70 %. No treatment-related deaths or discontinuations were reported.
Culmerciclib is the first oral CDK2/4/6 triple inhibitor, designed to curb resistance by targeting both CDK2 and CDK4 while limiting CDK6-related myelosuppression. The drug gained National Medical Products Administration approval in December 2025 (combination with fulvestrant after endocrine therapy progression) and received a first-line indication in April 2026. A Phase III adjuvant study is fully enrolled.
The Phase II data suggest culmerciclib delivers durable tumor control with a manageable safety profile for patients who have exhausted prior CDK4/6-based regimens, reinforcing its potential role in the evolving treatment landscape for advanced HR+/HER2– breast cancer.
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