Trial results for the Phase 3 study investigating coformulated favezelimab/pembrolizumab (MK-4280A) in previously treated metastatic PD-L1 positive colorectal cancer were posted on ClinicalTrials.gov on 2025-09-17. The combination therapy demonstrated an objective response rate (ORR) of 6.0%, while the standard of care arm showed an ORR of 0.0%.
Background
The study, titled "A Study of Coformulated Favezelimab/Pembrolizumab (MK-4280A) Versus Standard of Care in Subjects With Previously Treated Metastatic PD-L1 Positive Colorectal Cancer (MK-4280A-007)-China Extension Study," aimed to assess the safety and efficacy of the coformulated therapy in adult Chinese participants with metastatic colorectal cancer.
Trial design
The Phase 3 study (NCT05600309) was completed with an enrollment of 94 participants diagnosed with colorectal cancer. The trial compared coformulated favezelimab/pembrolizumab against a standard of care arm consisting of either regorafenib or TAS-102 (trifluridine and tipiracil). The primary study hypothesis was that coformulated favezelimab/pembrolizumab (MK-4280A) would be superior to standard of care with respect to overall survival.
Key results
For the primary outcome of Overall Survival (OS):
- The median OS for the favezelimab/pembrolizumab group was 9.6 Months.
- The median OS for the Standard of Care (Regorafenib or TAS-102) group was 9.2 Months.
A Log Rank analysis for OS showed a Hazard Ratio (HR) of 0.94 (95.0% CI: 0.59 to 1.5), with a p-value of 0.3914.
For Progression-Free Survival (PFS) as assessed by Blinded Independent Central Review (BICR) per RECIST 1.1:
- The median PFS for the favezelimab/pembrolizumab group was 2.1 Months.
- The median PFS for the Standard of Care (Regorafenib or TAS-102) group was 2.1 Months.
A Log Rank analysis for PFS showed a Hazard Ratio (HR) of 1.23 (95.0% CI: 0.78 to 1.92), with a p-value of 0.8091.
Regarding Objective Response Rate (ORR) per RECIST 1.1 as assessed by BICR:
- The ORR for the favezelimab/pembrolizumab group was 6.0 Percentage of Participants.
- The ORR for the Standard of Care (Regorafenib or TAS-102) group was 0.0 Percentage of Participants.
A Miettinen & Nurminen Method analysis showed a difference in percentage of 6.0 (95.0% CI: -2.3 to 16.3), with a p-value of 0.0502.
In terms of safety:
- 46 Participants in the favezelimab/pembrolizumab group experienced at least one adverse event (AE).
- 44 Participants in the Standard of Care (Regorafenib or TAS-102) group experienced at least one AE.
- 5 Participants in the favezelimab/pembrolizumab group discontinued study treatment due to an AE.
- 4 Participants in the Standard of Care (Regorafenib or TAS-102) group discontinued study treatment due to an AE.
What this means
The results of this Phase 3 study indicate that the coformulated favezelimab/pembrolizumab did not demonstrate superiority in overall survival compared to standard of care, which was the primary hypothesis. Both overall survival and progression-free survival outcomes were similar between the two treatment arms. While the objective response rate showed a numerical difference favoring the combination therapy, with 6.0% versus 0.0% for standard of care, the p-value of 0.0502 was borderline. The safety profiles, as measured by the number of participants experiencing adverse events and discontinuing treatment due to AEs, were comparable between the two groups.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT05600309, titled "A Study of Coformulated Favezelimab/Pembrolizumab (MK-4280A) Versus Standard of Care in Subjects With Previously Treated Metastatic PD-L1 Positive Colorectal Cancer (MK-4280A-007)-China Extension Study," were posted on 2025-09-17 on clinicaltrials.gov.