Trial results for the Phase 2 study (NCT04251169) investigating pembrolizumab in combination with paclitaxel for patients with HR+/HER2- non-luminal advanced breast cancer after CDK4/6 inhibitor progression were posted on ClinicalTrials.gov on 2025-06-03. The study reported a median progression-free survival (PFS) of 8.1 months.
Background
This study evaluated pembrolizumab in combination with paclitaxel for patients with locally advanced or metastatic non-luminal hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer. Participants had experienced recurrence or progression while receiving previous therapy with a cyclin-dependent kinase (CDK) inhibitor in the adjuvant setting or for advanced disease.
Trial design
The study (NCT04251169) was an open-label, single-arm, multicenter Phase 2 trial that enrolled 20 participants. It investigated pembrolizumab in combination with paclitaxel in patients with locally advanced or metastatic non-luminal hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer, as defined by the PAM50 assay. Participants had experienced recurrence or progression while receiving previous therapy with a cyclin-dependent kinase (CDK) inhibitor in the adjuvant setting or for advanced disease. The trial's overall status was TERMINATED.
Key results
The trial reported several key outcomes for the Pembrolizumab + Paclitaxel treatment arm:
- The Overall Response Rate (ORR) was observed in 7 out of 11 evaluable participants.
- The Clinical Benefit Rate (CBR) was observed in 1 out of 17 evaluable participants.
- Median Progression Free Survival (PFS) was 8.1 months.
- Median Duration of Response (DoR) was 6.3 months.
- Median Time to Response (TtR) was 3.9 months.
- Median Overall Survival (OS) was 26 months.
- The mean ratio of PFS on study treatment compared to PFS on prior line of therapy (Pre-PFS) was 1.10 (Standard Deviation: 0.64).
What this means
The results from this Phase 2 trial provide insights into the activity of pembrolizumab in combination with paclitaxel for patients with HR+/HER2- non-luminal advanced breast cancer who have progressed on CDK4/6 inhibitors. The observed median Overall Survival of 26 months and median Progression Free Survival of 8.1 months suggest potential clinical benefit in this challenging patient population. The Overall Response Rate of 7 out of 11 evaluable participants indicates a proportion of patients experienced tumor shrinkage, while the Clinical Benefit Rate of 1 out of 17 evaluable participants provides a broader measure of disease control. The mean ratio of PFS on study treatment to prior PFS of 1.10 suggests that the combination therapy may offer an improvement in progression-free survival compared to the immediate prior line of treatment.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT04251169, titled "Pembrolizumab + Paclitaxel in HR+/HER2- Non-luminal (by PAM50) Advanced Breast Cancer After CDK4/6 Inhibitor Progression," were posted on 2025-06-03 on clinicaltrials.gov.