Repositioning Food and Drug Administration-Approved Drugs for Inhibiting Biliverdin IXβ Reductase B as a Novel Thrombocytopenia Therapeutic Target

Biliverdin IXβ reductase B (BLVRB) has recently been proposed as a novel therapeutic target for thrombocytopenia through its reactive oxygen species (ROS)-associated mechanism. Thus, we aim at repurposing drugs as new inhibitors of BLVRB. Based on IC₅₀ (<5 μM), we have identified 20 compounds out of 1496 compounds from the Food and Drug Administration (FDA)-approved library and have clearly mapped their binding sites to the active site. Furthermore, we show the detailed BLVRB-binding modes and thermodynamic properties (ΔH, ΔS, and K_D) with nuclear magnetic resonance (NMR) and isothermal titration calorimetry together with complex structures of eight water-soluble compounds. We anticipate that the results will serve as a novel platform for further in-depth studies on BLVRB effects for related functions such as ROS accumulation and megakaryocyte differentiation, and ultimately treatments of platelet disorders.