Pyrvinium (Viprynium) is an anthelmintic effective for pinworms. Pyrvinium is used in the treatment of enterobiasis caused by Enterobius vermicularis (pinworm). Pyrvinium has being shown to be a potent inhibitor of Wnt signaling (EC(50) of ∼10 nM). Pyrvinium binds all casein kinase 1 (CK1) family members in vitro at low nanomolar concentrations and pyrvinium selectively potentiates casein kinase 1α (CK1α) kinase activity. Pyrvinium pamoate (PP) is a potent noncompetitive inhibitor of the androgen receptor (AR). A noncompetitive AR inhibitor pyrvinium has significant potential to treat CRPC, including cancers driven by ligand-independent AR signaling.