More good news for Cumociclib Capsules (Saitanxin^®), the world's first CDK2/4/6 inhibitor! Following its official marketing approval, on December 17, a randomized, double-blind, Phase III clinical trial study of Saitanxin^® combined with Fulvestrant for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer was officially published in the "Nature" sub-journal "Signal Transduction and Targeted Therapy" (STTT, IF: 52.7). The study results^[1] showed that the median Progression-Free Survival (mPFS) for patients receiving this regimen reached 16.6 months, with a significant 64% reduction in the risk of disease progression or death compared to the control group. 

mPFS Reaches 16.6 Months, Risk of Disease Progression/Death Reduced by 64%

This study was a randomized, double-blind, parallel-controlled, Phase III clinical trial, with Professor Zefei Jiang from the Fifth Medical Center of the Chinese PLA General Hospital and Professor Yongmei Yin from the Jiangsu Province Hospital serving as co-Leading PIs. The primary endpoint was investigator-assessed progression-free survival (INV-PFS). Secondary endpoints included independent review committee-assessed progression-free survival (IRC-PFS), overall survival (OS), objective response rate (ORR), clinical benefit rate (CBR), and duration of response (DOR), among others. 

Between March 18, 2022, and March 3, 2023, a total of 293 eligible patients were enrolled. The median age of the enrolled patients was 53 years. All had previously received endocrine therapy, 23.3% had received systemic chemotherapy for recurrent or metastatic disease, 21.5% had primary endocrine resistance, and 59% had visceral metastases. Enrolled patients were randomized in a 2:1 ratio to receive either Cumociclib plus Fulvestrant or placebo plus Fulvestrant. The two groups were generally balanced in terms of demographics and baseline characteristics. 

As of the interim analysis for this report, a total of 134 PFS events had occurred (68 in the experimental group and 66 in the control group). The mPFS in the Cumociclib group was 16.6 months (95%CI: 13.8-NE), compared to 7.5 months (95%CI: 5.3-11) in the control group, with an HR of 0.36 (95%CI: 0.26-0.51, p<0.001). The results of the PFS subgroup analysis indicated that all subgroups benefited from Cumociclib treatment. 

INV-Assessed PFS Curve

PFS Subgroup Analysis

The median follow-up time was 13.8 months, at which point the median overall survival (mOS) had not been reached in either group. The 18-month OS rate was 79.0% in the Cumociclib group versus 73.9% in the placebo group (p=0.188). The ORR was 40.2% (95% CI: 33.3–47.5) in the Cumociclib group, compared to 12.1% (95% CI: 6.4–20.2) in the control group. 

In terms of safety, the incidence of treatment-emergent adverse events (TEAEs) was similar between the experimental group and the control group (98.5% vs. 96.0%). Common TEAEs in the Cumociclib group were mainly diarrhea (87.1%), neutropenia (80.4%), and leukopenia (79.9%). No serious adverse events such as pulmonary embolism or interstitial lung disease occurred, and no new safety signals were observed compared to other CDK4/6 inhibitors. 

This study showed that Cumociclib combined with Fulvestrant significantly prolonged the progression-free survival of patients with endocrine-resistant HR+/HER2− advanced breast cancer, reducing the risk of disease progression or death by 64%. It demonstrated consistent efficacy advantages across all subgroups, providing significant clinical benefits. Meanwhile, the adverse reactions of Cumociclib were generally manageable, with no new safety signals emerging. 

As the world's first CDK2/4/6 inhibitor, Saitanxin^® is demonstrating promising applications across different treatment stages of advanced breast cancer. On December 11, Cumociclib Capsules (Saitanxin^®) received drug registration approval for use in combination with Fulvestrant for the treatment of HR+/HER2- locally advanced or metastatic breast cancer in patients who have previously received endocrine therapy. In July of this year, an application for Cumociclib combined with Fulvestrant for the initial endocrine treatment of patients with HR+/HER2- locally advanced or metastatic breast cancer was accepted by the CDE. 

References:
[1] Yin Y,et al. Novel CDK2/4/6 inhibitor culmerciclib (TQB3616) plus fulvestrant in previously treated, HR-positive, HER2-negative advanced breast cancer: a randomized, double-blind, phase 3 trial. Signal Transduct Target Ther.2025; 10(1): 414. Published 2025 Dec 18.

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