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Expanding the Treatment Window for the FDA-Approved Radiation Countermeasure Nplate
Gregory P Holmes-Hampton1, Venkateshwara Rao Dronamraju1,2, Vidya P Kumar1,2
1Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, MD 20889, United States.
Military Medicine
|August 6, 2026
Summary
Nplate (romiplostim) shows significant survival benefits for acute radiation syndrome (ARS) when administered as a delayed mitigator or prophylaxis. This expands its potential use as a medical countermeasure for radiological emergencies.
Area of Science:
- Radiation Biology
- Medical Countermeasures
- Hematology
Background:
- Radiological emergencies pose significant health risks, with limited medical countermeasures (MCMs) for acute radiation syndrome (ARS).
- Nplate (romiplostim), a thrombopoietin receptor agonist, is approved for post-radiation exposure but not as a prophylaxis.
- Expanding Nplate's utility for delayed administration and prophylactic use is critical for medical readiness.
Purpose of the Study:
- To evaluate the efficacy of Nplate as both a delayed mitigator and a prophylaxis for ARS.
- To explore the potential of Nplate in mitigating radiation effects beyond its current approved window.
- To assess Nplate's protective capabilities for first responders and military personnel.
Main Methods:
- Two studies in C57BL/6 mice evaluated Nplate's efficacy against radiation exposure.
- Nplate was administered as a mitigator at 24, 48, and 72 hours postirradiation.
- Nplate was administered as a prophylaxis at 6 and 12 hours preirradiation, using gamma and mixed neutron-gamma radiation sources.
Main Results:
- Delayed Nplate administration significantly improved survival rates in a dose-dependent manner.
- Nplate treatment restored blood cell counts, increased bone marrow colony-forming units, and enhanced megakaryocyte production.
- Prophylactic Nplate administration demonstrated even more pronounced survival benefits, highlighting its protective potential.
Conclusions:
- Nplate is effective as a mitigator when administered up to 72 hours postirradiation, supporting expanded use.
- Nplate shows potent prophylactic effects against radiation exposure, offering significant protection.
- These findings support broadening Nplate's indications for use as an MCM in radiological or nuclear incidents.
