An experimental drug being developed as a medical countermeasure for radiation injury has passed an early safety check in mice. A second mouse study, funded by the National Institute of Allergy and Infectious Diseases (NIAID), will test whether the drug works, with survival as its primary endpoint and results expected in early December. The candidate, entolimod, is intended to treat acute radiation syndrome (ARS), the illness that follows being exposed to a large dose of radiation.
San Antonio-based Valion Bio announced the safety results on Oct. 28, 2026 and the follow-on efficacy study on Oct. 30. Both studies are run by the Armed Forces Radiobiology Research Institute (AFRRI) and funded by NIAID’s Radiation and Nuclear Countermeasures Program, under an interagency agreement with the Uniformed Services University.
Entolimod is a biologic designed to activate Toll-like Receptor 5, an immune pathway the company associates with cell protection and tissue recovery. The company is developing it as a potential medical countermeasure against both the bone marrow and gastrointestinal forms of ARS. The FDA has granted it Fast Track and Orphan Drug designations. Because testing ARS treatments in people would be unethical, the company is pursuing approval under the FDA’s Animal Rule, which allows approval based on animal efficacy studies when human trials are not feasible. Valion holds an exclusive license to the drug from Statera Biopharma.
What the Efficacy Study Will Test
The second study is designed to test whether the drug works in a mouse model of gastrointestinal ARS, with survival as the primary measure. The mice will be exposed to partial-body radiation, with roughly 2.5% of each animal’s bone marrow shielded. The company says this design helps researchers tell apart effects tied to reducing gastrointestinal injury from effects tied to recovery.
Mice will receive a single dose of entolimod or saline 24 hours after radiation exposure and be monitored for 30 days. The primary endpoint is survival, comparing treated and control animals. The company also describes the study as looking at gastrointestinal tissue recovery.
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This article was researched and sourced by Global Biodefense editors and reported with Claude AI assistance for drafting and editing.