Trial results for the Phase 2 study NCT03747120, investigating pembrolizumab in HER2-positive breast cancer, were posted on ClinicalTrials.gov on 2025-05-08. The study evaluated neoadjuvant regimens, with the THP-Pembrolizumab arm showing 39 participants achieving pathological complete response (pCR), compared to 28 participants in the THP arm.
Background
Pembrolizumab (Keytruda) is an immunotherapy drug. The trial investigated its use in HER2-positive breast cancer, a subtype of breast cancer where cancer cells have too much of a protein called HER2. The trial aimed to evaluate the efficacy and safety of adding pembrolizumab to established HER2-targeted therapies and chemotherapy.
Trial design
The study NCT03747120, titled "Neoadjuvant Her2-targeted Therapy and Immunotherapy With Pembrolizumab [IIT2018-04-MCARTHUR-NEOHP]," was a Phase 2 open-label, randomized, multi-center trial. It enrolled 138 chemo-naive patients with invasive HER2-positive breast cancer whose primary tumors were > 2 cm and/or clinically lymph node positive. The trial compared three neoadjuvant treatment arms:
- Arm A: THP (trastuzumab, pertuzumab, and weekly paclitaxel)
- Arm B: THP-Pembrolizumab (trastuzumab, pertuzumab, pembrolizumab, and weekly paclitaxel)
- Arm C: TH-Pembrolizumab (trastuzumab, pembrolizumab, and weekly paclitaxel)
Key results
The trial reported results for several pathological response outcomes across the three treatment arms:
- Pathological Complete Response (pCR):
- Arm A: THP: 28 Participants
- Arm B: THP-Pembrolizumab: 39 Participants
- Arm C: TH-Pembrolizumab: 5 Participants
- Pathological Complete Invasive and in Situ Response Rate (Breast and Axilla):
- Arm A: THP: 25 Participants
- Arm B: THP-Pembrolizumab: 30 Participants
- Arm C: TH-Pembrolizumab: 4 Participants
- Pathological Complete Response Rate (pCR) in Breast Only:
- Arm A: THP: 28 Participants
- Arm B: THP-Pembrolizumab: 39 Participants
- Arm C: TH-Pembrolizumab: 5 Participants
- Residual Cancer Burden (RCB):
- Arm A: THP: 39 Participants
- Arm B: THP-Pembrolizumab: 44 Participants
- Arm C: TH-Pembrolizumab: 13 Participants
What this means
The results indicate that the addition of pembrolizumab to the trastuzumab, pertuzumab, and paclitaxel (THP) regimen in Arm B was associated with a higher number of participants achieving pathological complete response (pCR) compared to the THP regimen alone in Arm A. Specifically, 39 participants in the THP-Pembrolizumab arm achieved pCR, versus 28 participants in the THP arm. Conversely, the regimen in Arm C, which included pembrolizumab but omitted pertuzumab, showed a substantially lower number of participants achieving pCR, with only 5 participants.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT03747120, titled "Neoadjuvant Her2-targeted Therapy and Immunotherapy With Pembrolizumab [IIT2018-04-MCARTHUR-NEOHP]," were posted on 2025-05-08 on clinicaltrials.gov.