Warhead compound 4, a small molecule inhibitor of AKR1C3, at concentration from 0.001 to 10 μM affords no reduction of cell viability in 22Rv1 prostate cancer cells after 72 h of treatment (Fig. 9a), despite its AKR1C3 IC50 = 62 nM. The gene discussed is AKR1C3; the disease is prostate carcinoma.