Biomedicine · global
ERAP1 Inhibitor Combined With Immunotherapy Shows Anticancer Signal in Early Trial
Phase 1 data presented at ASCO show that Greywolf Therapeutics’ GRWD5769, combined with cemiplimab, was associated with tumor shrinkage across multiple advanced cancers that had previously failed immunotherapy; however, the study remains early, and it is not yet possible to determine whether the approach can extend survival or become routine treatment.
An early clinical trial presented at the American Society of Clinical Oncology annual meeting has brought attention to an experimental drug targeting a mechanism of tumor immune escape. GRWD5769, an oral ERAP1 inhibitor developed by Greywolf Therapeutics, was combined with the immune checkpoint drug cemiplimab, and tumor shrinkage was observed in some patients with difficult-to-treat cancers.
The Phase 1 trial enrolled 83 patients with cancer types including cervical cancer, bladder cancer, liver cancer, bowel cancer, lung cancer, and head and neck cancer. These participants had responded poorly to prior treatment, with the key background being that immunotherapy had previously been ineffective or had lost effect. As a result, the study focus was not first-line treatment, but whether immune attack could be reawakened.
The research team observed signs of tumor shrinkage in 26 patients, including 15 whose tumors shrank by at least 30%. The report also noted that some degree of response signal was seen across all six cancer types, leading GRWD5769 to be viewed as an immuno-oncology platform worth following, rather than simply a new-drug story in a single cancer type.
The core concept behind GRWD5769 is inhibition of an enzyme called ERAP1. Tumors can reduce T-cell recognition by altering antigen presentation; if this pathway can be interrupted, in theory, cancer cells that were previously “invisible” could be re-exposed to the immune system, with immunotherapies such as cemiplimab then helping T cells launch an attack.
However, these results still require cautious interpretation. The primary purpose of Phase 1 trials is usually to assess safety, dosage, and early activity. Sample sizes are limited, and such trials may not directly answer whether patients can live longer, how long responses may last, or which patients are most likely to benefit. Seeing signals across cancer types is notable, but it also requires confirmation in larger and more rigorously designed studies.
Current reports state that the treatment was well tolerated in the trial, and the drug is an oral tablet. If later studies support the findings, it may be easier to deploy clinically than some complex cell therapies. But before the evidence matures, it remains an experimental treatment and cannot be regarded as a proven effective standard cancer therapy.
The key next step is to expand the trial and clarify biomarkers: which tumors truly depend on ERAP1-related escape mechanisms, which patients whose immunotherapy has failed may still have a chance of having their immune response restarted, and whether tumor shrinkage can translate into durable disease control. The answers to these questions will determine whether GRWD5769 can move from an early highlight to a practical treatment option.