ASP-9521

ASP-9521 is a potent, selective and orally available AKR1C3 inhibitor with an IC₅₀ of 11 nM for human AKR1C3. IC50 & Target: IC50:11 nM (human AKR1C3), 49 nM (monkey AKR1C3)^[1] In Vitro: AKR1C3 is a promising therapeutic target in castrationresistant prostate cancer, as combination of an AKR1C3 inhibitor and a gonadotropin-releasing hormone analogue may lead to complete androgen blockade.ASP-9521 inhibits conversion of androstenedione (AD) into androstenediol and testosterone (T) by recombinant human or cynomolgus monkey AKR1C3 in a concentrationdependent manner (IC₅₀, human: 11 nM; IC₅₀,monkey: 49 nM). ASP-9521 shows more than 100-fold selectivity for AKR1C3 over the isoform AKR1C2. In LNCaP-AKR1C3 cells, ASP-9521 suppresses AD-dependent PSA production and cell proliferation^[1]. In Vivo: In CWR22R xenografts, single oral administration of ASP-9521 (3 mg/kg) inhibits AD-induced intratumoural T production and this inhibitory effect is maintained for 24 h. After oral administration, ASP-9521is rapidly eliminated from plasma, while its intratumoural concentration remained high. The bioavailability of ASP-9521 after oral administration (1 mg/kg) is 35 %, 78 % and 58 % in rats, dogs and monkeys, respectively^[1].