Novel CKD4/6 Inhibitor Under Study in Advanced Breast Cancer

By: Jenna Carter, PhD
Posted: Thursday, November 7, 2024

Preliminary findings have revealed that tibremciclib (BPI-16350), a novel CDK4/6 inhibitor, added to fulvestrant has shown antitumor activity in patients with advanced breast cancer. In a recent study presented at the European Society for Medical Oncology (ESMO) Congress 2024 (Abstract 320MO), Shusen Wang, MD, of State Key Laboratory of Oncology in South China, Guangzhou, and colleagues reported longer progression-free survival with the investigational combination than with placebo and fulvestrant in patients with hormone receptor–positive, HER2-negative locally recurrent or metastatic advanced breast cancer.

A total of 275 patients with breast cancer were included in this phase III study. Patients were randomly assigned to receive daily tibremciclib at 400 mg orally plus fulvestrant at 500 mg intramuscularly on days 1, 15, 29, and then every 28 days. The primary endpoint was investigator-assessed progression-free survival, and the secondary endpoints included progression-free survival assessed by an independent review committee, investigator-assessed objective response rate, clinical benefit rate, overall survival, and safety.

At a median follow-up of 5.6 months, the investigator-assessed progression-free survival was 11.1 months (95% confidence interval [CI] = 9.2–12.9 months) in the tibremciclib group vs 5.5 months (95% CI = 4.2–7.4 months) in the placebo group (hazard ratio [HR] = 0.31; 95% CI = 0.21–0.47; P < .0001). Additionally, the investigator-assessed objective response rate was 28.8% vs 6.7% in the placebo group. Further, the disease control rate was 89.1% vs 76.7%, and the clinical benefit rate was 46.2% vs 21.1% with tibremciclib plus fulvestrant vs placebo plus fulvestrant, respectively.

Safety findings revealed that the most common grade ≥ 3 treatment-emergent adverse event with the investigational combination therapy was neutropenia (13%). Moreover, no drug-related deaths were reported in the tibremciclib group; however, one death was reported in the placebo group, and treatment was discontinued in three patients because of adverse events.

Disclosure: The study authors reported no conflicts of interest.

ESMO Congress 2024

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