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

AKR1C3:11 nM

METHODS: H9c2 cells were preincubated in the presence of ASP9521 (25 μM) for 3 h. Then, DOX/DNR were added for the next 24 h. Cell viability was determined using the MTT assay.
RESULTS The viability of H9c2 cells treated with DOX was 79%, while that of H9c2 cells preincubated with ASP9521 was 93%. ASP9521 almost completely protected cardiomyocytes from the toxic activity of DOX. [2]
METHODS: Human lung cancer cell line A549 cells were treated with ASP9521 (0.1, 1, 10, 25, 50, 100 μM) and DNR (0.05–1 μM), and the IC50 of DNR alone or in combination with ASP9521 (25 μM) was calculated and compared.
RESULTS The IC50 values ​​obtained were 0.442 μM (DNR alone) and 0.379 μM (in combination with ASP9521). [2]

ASP9521 inhibits the conversion of AD to T by recombinant human or cynomolgus monkey AKR1C3 in a concentration-dependent manner (IC50, human: 11 nM; IC50, monkey: 49 nM); ASP9521 is more than 100-fold more selective for AKR1C3 than for the isoform AKR1C2; a single oral dose of ASP9521 (3 mg/kg) inhibits AD-induced intratumoral T production in CWR22R xenografts, and this inhibitory effect persists for 24 hours; after oral administration, ASP9521 is rapidly eliminated from plasma, while its intratumoral concentration remains high; the bioavailability of oral ASP9521 (1 mg/kg) in rats, dogs, and monkeys is 35%, 78%, and 58%, respectively. [1]

LNCaP-AKR1C3 cells stably expressing human AKR1C3 are seeded in 96-well plates at 10000 cells/100 μL/well in RPMI-1640 medium supplemented with heat-inactivated charcoal-dextran-stripped FBS (1 % for the PSA expression assay and T measurement and 5 % for the cell proliferation assay). After 24 h incubation, AD is added to each well with or without ASP-9521 (0.3-100 nM). The cell culture media are collected 24 h after administration of AD to measure T concentration and 6 days after administration of AD to measure cell proliferation using Cell-Titer Glo assay.

ASP-9521 is prepared in 0.5 % methyl cellulose.Mice carrying HEK293 or HEK293-AKR1C3 tumors with similar sizes are selected and randomly divided into 5 groups (N=3 for each group). All groups are treated with ASP-9521 (single oral administration; 3 mg/kg). Plasma (from the central vein) and tumor tissues are collected at 0.25, 0.5, 1, 2 and 4 h after administration of ASP-9521, and ASP-9521 concentrations are determined using the HPLCMS/MS method.