Trial results for the Phase 1b study of pembrolizumab in patients with relapsed myelodysplastic syndromes (MDS) and acute leukemias were posted on ClinicalTrials.gov on 2025-05-11. The single-arm study reported that 6 of 16 participants demonstrated clinical benefit, while 9 participants experienced graft-versus-host disease (GvHD) or other significant immune-mediated toxicities.
Background
The study investigated pembrolizumab for patients with myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), and acute lymphoblastic leukemia (ALL) whose disease had relapsed after receiving an allogeneic hematopoietic stem cell transplant.
Trial design
The study, titled "Augmentation of the Graft vs. Leukemia Effect Via Checkpoint Blockade With Pembrolizumab" (NCT03286114), was a single-arm, open-label, Phase 1b trial. It enrolled 16 participants with myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), or acute lymphoblastic leukemia (ALL) who had relapsed after an allogeneic hematopoietic stem cell transplant. The study aimed to evaluate pembrolizumab in this population, though specific primary outcome measures were not detailed in the posted results.
Key results
The trial reported the following key measurements for participants receiving pembrolizumab:
- For the outcome "The Number of Patients That Demonstrate Clinical Benefit From Treatment", 6 participants showed clinical benefit.
- For the outcome "The Number of Patients That Respond to Treatment", 3 participants responded to treatment.
- Regarding "Graft Versus Host Disease (GvHD) or Other Significant Immune Mediated Toxicities", 9 participants experienced these events, and another measurement for the same outcome reported 2 participants.
- Overall Survival was reported as 37.5% of participants.
- Event-Free Survival was reported as 31.3% of participants.
What this means
The results from this Phase 1b study provide initial insights into the use of pembrolizumab in a challenging population of patients with relapsed hematologic malignancies after allogeneic hematopoietic stem cell transplant. While some participants demonstrated clinical benefit and response, the reported incidence of GvHD or other significant immune-mediated toxicities in a substantial portion of the cohort highlights the complex risk-benefit profile in this setting. The overall survival and event-free survival rates offer preliminary efficacy signals for future research. The termination of the study suggests that further investigation may be warranted with careful consideration of patient selection and toxicity management.
Source
The information regarding these trial results was obtained from ClinicalTrials.gov, a public database of clinical studies. The results for study NCT03286114, titled "Augmentation of the Graft vs. Leukemia Effect Via Checkpoint Blockade With Pembrolizumab," were posted on 2025-05-11 on clinicaltrials.gov.