Coumarin-Based Aldo-Keto Reductase Family 1C (AKR1C) 2 and 3 Inhibitors

A series of 7-substituted coumarin derivatives have been characterized as pan-aldo-keto reductase family 1C (AKR1C) inhibitors. The AKR1C family of enzymes are overexpressed in numerous cancers where they are involved in drug resistance development. 7-hydroxy coumarin ethyl esters and their corresponding amides have high potency for AKR1C3 and AKR1C2 inhibition. Coumarin amide 3 a possessed IC₅₀ values of 50 nM and 90 nM for AKR1C3 and AKR1C2, respectively, and exhibits ‘drug-like’ metabolic stability and half-life in human and mouse liver microsomes and plasma. Compound 3 a was employed as a chemical tool to determine pan-AKR1C2/3 inhibition effects both as a radiation sensitizer and as a potentiator of chemotherapy cytotoxicity. In contrast to previously reported pan-AKR1C inhibitors, 3 a demonstrated no radiation sensitization effect in a radiation-resistant prostate cancer cell line model. Pan-AKR1C inhibition also did not potentiate the in vitro cytotoxicity of ABT-737, daunorubicin or dexamethasone, in two patient-derived T-cell ALL and pre-B-cell ALL cell lines. In contrast, a highly selective AKR1C3 inhibitor, compound K90, enhanced the cytotoxicity of both ABT-737 and daunorubicin in the T-cell ALL cell line model. Thus, the inhibitory profile required to enhance chemotherapeutic cytotoxicity in leukemia may be AKR1C isoform and drug specific.