Acute radiation syndrome (ARS) is a severe illness that occurs when a person is exposed to high levels of ionizing radiation, typically within a relatively short period. Radioprotector medical countermeasures (MCMs) against ARS are designed to be administered prior to IR exposure to prevent harmful impacts, increase survival, and reduce the recovery time and cost. U.S. military personnel may be exposed to IR during military operations in known radiologically contaminated areas, thus effective, safe prophylactic MCMs against ARS are clearly urgent medical demands. Nevertheless, there is no licensed ARS prophylactic thus far. Given the real-world scenarios that military operations in radiologically contaminated areas may last for hours, an ideal prophylactic MCM must be able to provide sufficient protection in the entire duration of operations. Moreover, the hematopoietic subsyndrome could be the primary concern due to the high IR exposure sensitivity of the hematopoietic system. Based on the comprehensive understandings on the product requirements, herein, Zymeron purposes to utilize its advanced techniques to reformulate amifostine, aiming to develop a safe and easy-to-use prophylactic MCM with prolonged protective effects on the hematopoietic system.