No radioprotector that can be administered prior to exposure has been approved for ARS. All FDA-approved radiation countermeasures (filgrastim, a recombinant DNA form of the naturally occurring granulocyte colony-stimulating factor, G-CSF pegfilgrastim, a PEGylated form of the recombinant human G-CSF sargramostim, a recombinant granulocyte macrophage colony-stimulating factor, GM-CSF) are classified as radiomitigators.
To date, no new chemical entity has been approved by the FDA as a radiation countermeasure for acute radiation syndrome (ARS). Early development of such agents focused on thiol synthetic compounds, e.g., amifostine (2-(3-aminopropylamino) ethylsulfanylphosphonic acid), approved as a radioprotector by the Food and Drug Administration (FDA, USA) but for limited clinical indications and not for nonclinical uses. Because ionizing radiation-induced cellular damage is primarily attributed to free radicals, radical scavengers are promising as potential radioprotectors. However, effective (ideal) radioprotectors and radiomitigators remain an unsolved problem. The development of protective agents against harmful radiations has been a subject of investigation for decades.
