An antihelmintic that is active against most tapeworms. (From Martindale, The Extra Pharmacopoeia, 30th ed, p48)

An orally bioavailable chlorinated salicylanilide, with anthelmintic and potential antineoplastic activity. Upon oral administration, niclosamide specifically induces degradation of the androgen receptor (AR) variant V7 (AR-V7) through the proteasome-mediated pathway. This downregulates the expression of the AR variant, inhibits AR-V7-mediated transcriptional activity, and reduces AR-V7 recruitment to the prostate-specific antigen (PSA) gene promoter. Niclosamide also prevents AR-V7-mediated STAT3 phosphorylation and activation. This inhibits AR/STAT3-mediated signaling and prevents expression of STAT3 target genes. Altogether, this may inhibit growth of AR-V7-overexpressing cancer cells. The AR-V7 variant, which is encoded by contiguous splicing of AR exons 1/2/3/CE3, is upregulated in a variety of cancer cell types, and is associated with both cancer progression and resistance to AR-targeted therapies.