AR and prostate cancer: AR‐V7 is a well‐known AR splice variant in prostate cancer characterized by the absence of the C‐terminal ligand‐binding domain while retaining the N‐terminal transcriptional elements that activate AR signaling independently of ligands.[29] As expected, given that UBX‐390 targets the AR ligand‐binding domain, UBX‐390 could not directly induce degradation of AR‐V7 24 h post‐treatment in VCaP cells, a CRPC cell line expressing the splice variant, AR‐V7.[30] Therefore, this result confirms that UBX‐390 specifically targets the ligand binding site of AR (Figure S6A, Supporting Information).