(S)-6-Phenyl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole phosphate is the phosphate salt of levamisole, the levo-enantiomer of tetramisole. It is primarily used as a broad-spectrum anthelmintic in veterinary medicine to treat nematode infections in livestock and poultry by acting as a nicotinic acetylcholine receptor agonist, inducing spastic paralysis in parasites. Additionally, levamisole exhibits immunomodulatory properties, enhancing T-cell activation and macrophage function, and has been used as an adjuvant in human cancer therapy (e.g., with 5-fluorouracil for colorectal cancer), though its use is limited due to risks of agranulocytosis and neutropenia. This compound is a specialty chemical serving as a pharmaceutical reference standard or intermediate in medicinal chemistry.