ASP-9521

ASP-9521 is a potent, selective and orally available AKR1C3 inhibitor with an IC50 of 11 nM for human AKR1C3.

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 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].

[1]. Kikuchi A, et al. In vitro and in vivo characterisation of ASP9521: a novel, selective, orally bioavailable inhibitor of 17β-hydroxysteroid dehydrogenase type 5 (17βHSD5; AKR1C3).Invest New Drugs. 2014 Oct;32(5):860-70.