Valion Bio (NASDAQ: VBIO) has announced that the Armed Forces Radiobiology Research Institute (AFRRI), in partnership with the National Institute of Allergy and Infectious Diseases (NIAID), has completed design of the survival efficacy protocol that will be used to evaluate the company’s lead candidate, Entolimod, a potential first and only treatment for gastrointestinal acute radiation syndrome (GI-ARS).
The partial body irradiation with 2.5% bone marrow sparing/shielding (PBI-BM2.5) at lethal radiation dose (LD50/30 of 14.6 Gy) murine model that the AFRRI/NIAID partnership selected to evaluate Entolimod is scientifically rigorous and meets the FDA’s Animal Rule criteria, which allows the Agency to approve new drugs and biological products based on animal efficacy studies when human clinical trials are unethical or not feasible, such as in the case of internal radioactive contamination.
Entolimod is a recombinant deletion variant of Salmonella FliC flagellin engineered to activate TLR5 selectively. Upon engagement, Entolimod triggers specific pathways that ultimately promote multi-tissue cytoprotection and inhibit apoptosis in radiosensitive hematopoietic and gastrointestinal tissues. By utilizing a proprietary murine model that spares only 2.5% of bone marrow (one hind leg and tail) from a lethal radiation dose, the study will isolate GI pathophysiology from overwhelming hematopoietic failure — creating a cleaner efficacy signal for a mechanism targeting intestinal epithelial recovery and immune restoration.
Currently, no FDA-approved medical countermeasures exist to mitigate GI-ARS. According to Valion, this Entolimod protocol advancement comes as the broader ARS medical countermeasures market accelerates, with global market valuations reaching an estimated $5.47 billion in 2025 and projected to expand to $7.80 billion by 2032, growing at a compound annual growth rate of 5.2%. North America, where government stockpiling and biodefense spending concentrate, accounts for 46% of market revenue.
In a statement, Michael Handley, CEO of Valion, commented, “The AFRRI protocol finalization represents a key inflection point for Entolimod as a radiation/nuclear countermeasure and for Valion as a company. We are now positioned to generate the high-quality non-clinical efficacy data that the FDA and the government require to support future licensure under the Animal Rule. The gastrointestinal subsyndrome of ARS is the market’s greatest unmet need—it is lethal, it is currently untreated, and it is precisely where Entolimod’s TLR5 agonist mechanism has the greatest potential to differentiate from incumbent G-CSF therapy.”
