Carrick Therapeutics Reports Promising Phase 2 Results for CDK7 Inhibitor Samuraciclib in Advanced Breast Cancer
核心洞察
Carrick Therapeutics (搜索) announced positive Phase 2 results for samuraciclib combined with fulvestrant in hormone receptor-positive, HER2-negative advanced breast cancer (搜索) patients previously treated with CDK4/6 (搜索) inhibitors.
The combination achieved a 55% overall response rate and 14.5-month median progression-free survival in patients without TP53 (搜索) mutations, compared to 29% and 6.8 months with fulvestrant alone.
Samuraciclib represents a first-in-class oral CDK7 (搜索) inhibitor that could provide a new treatment option for the 70% of second-line patients who are TP53 (搜索) wild-type.
Carrick Therapeutics (搜索) announced positive results from its Phase 2 SUMIT-BC clinical trial evaluating samuraciclib, a first-in-class oral CDK7 (搜索) inhibitor, in combination with fulvestrant for patients with hormone receptor-positive (HR+), HER2-negative advanced breast cancer (搜索) who previously received CDK4/6 (搜索) inhibitor therapy. The results were presented at the 2025 San Antonio Breast Cancer Symposium.
Clinical Trial Results Show Significant Efficacy
The randomized Phase 2b trial demonstrated notable improvements in clinical outcomes. Among all patients receiving samuraciclib at 360mg plus fulvestrant, the overall response rate (ORR) reached 33% with a median progression-free survival (mPFS) of 7.8 months, compared to 14% ORR and 5.6 months mPFS for fulvestrant alone.
The most compelling results emerged in patients without TP53 (搜索) gene mutations, a pre-specified stratification group. In this population, the combination achieved a 55% ORR and 14.5-month mPFS, versus 29% and 6.8 months respectively with fulvestrant monotherapy - representing a 7.7-month improvement in median progression-free survival.
"These Phase 2 trial results show that samuraciclib in combination with fulvestrant provided a very notable and clinically meaningful benefit in a broad patient population with HR positive, HER2 negative metastatic breast cancer (搜索) whose disease progressed following treatment with a CDK4/6 (搜索) inhibitor," said Tim Pearson, Chief Executive Officer of Carrick Therapeutics (搜索).
Addressing a Significant Clinical Challenge
The trial enrolled 60 patients with HR+, HER2- locally advanced or metastatic breast cancer (搜索) who had previously been treated with CDK4/6 (搜索) inhibitors and aromatase therapy. Dr. Sonia Pernas, Breast Medical Oncologist at the Catalan Institute of Oncology and lead author of the study, noted that "identifying the optimal treatment strategy for patients with HR positive, HER2 negative breast cancer following progression on CDK4/6 inhibitor therapy remains a significant clinical challenge."
The clinical benefit rate at 24 weeks (CBR24) also showed improvement, reaching 69% in TP53 (搜索) wild-type patients receiving the combination versus 46% with fulvestrant alone. Importantly, Carrick estimates that approximately 70% of patients in the second-line setting are TP53 wild-type, making this a substantial patient population.
Safety Profile and Biomarker Strategy
The safety profile appeared manageable, with diarrhea and nausea being the most common adverse events. Grade 3 diarrhea occurred in 10% of patients and grade 3 nausea in 15% of those receiving the 360mg dose. Two cases of grade 3 liver enzyme elevations were observed with the higher dose, and only one of 39 samuraciclib-treated patients discontinued due to adverse events.
Dr. Stuart McIntosh, Chief Medical Officer of Carrick Therapeutics (搜索), emphasized the biomarker approach: "SUMIT-BC is now the third study to demonstrate enhanced efficacy in the TP53wt patient population, which makes up 70% of patients in second line setting. The use of baseline ctDNA means this selection biomarker should be straightforward to integrate into clinical practice."
Mechanism and Development Pipeline
Samuraciclib works by inhibiting CDK7 (搜索), which regulates transcription of cancer-causing genes, promotes uncontrolled cell cycle progression, and contributes to anti-hormone therapy resistance. The mechanism also involves CDK7's suppression of the TP53 (搜索) gene, so when CDK7 is inhibited, p53 activity is restored, further contributing to tumor suppression.
The drug has received Fast Track designation from the FDA for use in combination with fulvestrant for treating CDK4/6 (搜索) inhibitor-resistant HR+, HER2- advanced breast cancer (搜索). Carrick plans to initiate Phase 3 trials in 2026.
Competitive Landscape
Among CDK7 (搜索) inhibitors in clinical development, samuraciclib appears to be the most advanced. Other companies developing CDK7 inhibitors include Recursion Pharmaceuticals with REC-617 and Qurient (搜索) with mocaciclib, though both have produced only single partial responses in their respective Phase 1/2 trials.
The company is also exploring samuraciclib in combination with other selective estrogen receptor degraders (SERDs), including ongoing trials with Roche's giredestrant, Menarini's Orserdu, and Arvinas's vepdegestrant, potentially expanding treatment options across different patient populations.