A polypeptide derived from the Salmonella filament protein flagellin with potential radioprotective and anticancer activities. As a toll-like receptor 5 (TLR5) agonist, entolimod binds to and activates TLR5 thereby stimulating tumor necrosis factor production and activating nuclear factor kappa B (NF-kB). This induces NF-kB-mediated signaling pathways and inhibits the induction of apoptosis. This may prevent apoptosis in normal, healthy cells during radiotherapy of cancerous cells and may allow for increased doses of ionizing radiation. In addition, entolimod may inhibit radiation-independent proliferation in TLR5-expressing tumor cells.