OXFORD, UK, May 22, 2026
Greywolf Therapeutics announced encouraging clinical results from the Phase 1b portion of its ongoing EMITT-1 trial, demonstrating durable anti-tumor activity for GRWD5769, a first-in-class oral ERAP1 inhibitor, in combination with the anti-PD-1 therapy cemiplimab. The data, presented during an oral session at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, showed objective responses across six difficult-to-treat solid tumor types, including patients with documented secondary resistance to prior anti-PD-1 therapy. The findings support the potential of GRWD5769 as a novel immunotherapy approach designed to enhance tumor visibility and overcome immune resistance mechanisms.
Phase 1b Trial Demonstrates Clinical Activity Across Multiple Tumor Types
The EMITT-1 study evaluated GRWD5769 plus cemiplimab in patients with non-small cell lung cancer (NSCLC), urothelial carcinoma, hepatocellular carcinoma (HCC), microsatellite stable colorectal cancer without liver metastases (MSS-CRC NLM), squamous cell carcinoma of the head and neck (SCCHN), and cervical cancer. Across the six expansion cohorts, objective response rates (ORR) ranged from 13% to 36%, despite patients having received a median of two prior lines of therapy and experiencing disease progression following previous immunotherapy. Researchers also reported durable clinical benefit rates ranging from 18% to 55%, highlighting the therapy’s ability to generate sustained anti-tumor responses in heavily pretreated populations.
Durable Responses and Progression-Free Survival Signal Potential Benefit
The study demonstrated long-lasting responses, with several patients remaining progression-free for more than six months. Median progression-free survival reached 33 weeks in NSCLC, 16 weeks in HCC, and 33 weeks in MSS-CRC NLM, with follow-up data continuing to mature. Investigators noted that achieving durable benefit in these patient populations is particularly significant because treatment options are limited after failure of prior anti-PD-1 therapies. The results suggest that ERAP1 inhibition may help reactivate immune responses against tumors that have previously developed resistance to checkpoint inhibitors.
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Novel Mechanism and Favorable Safety Profile Support Further Development
GRWD5769 targets Endoplasmic Reticulum Aminopeptidase 1 (ERAP1), a key regulator of antigen presentation on MHC-I molecules. By modulating tumor antigen presentation, the therapy aims to broaden T-cell recognition of cancer cells and reduce immune exhaustion. The combination treatment was generally well tolerated, with no major safety signals identified and most adverse events reported as Grade 1. Based on the positive Phase 1b findings, Greywolf is advancing the program into Stage 2 cohort expansions to support the design of a future randomized Phase 2 study. The company believes GRWD5769 has the potential to address major unmet needs in oncology by improving immune system recognition of tumors and enhancing responses to immunotherapy.
Source: Greywolf Therapeutics, press release
