Structure-Based Discovery of Novel Cyclophilin A Inhibitors for the Treatment of Hepatitis C Virus Infections.

Hepatitis C virus (HCV) is a major cause of end-stage liver disease. Direct-acting antivirals (DAAs), including inhibitors of nonstructural proteins (NS3/4A protease, NS5A, and NS5B polymerase), represent key components of anti-HCV treatment, but these are associated with increased drug resistance and toxicity. Thus, the development of host-targeted antiviral agents, such as cyclophilin A inhibitors, is an alternative approach for more effective, selective, and safer treatment. Starting with the discovery of a bis-amide derivative 5 through virtual screening, the lead compound 25 was developed using molecular modeling-based design and systematic exploration of the structure-activity relationship. The lead 25 lacked cytotoxicity, had potent anti-HCV activity, and showed selective and high binding affinity for CypA. Unlike cyclosporin A, 25 lacked immunosuppressive effects, successfully inhibited the HCV replication, restored host immune responses without acute toxicity in vitro and in vivo, and exhibited a high synergistic effect in combination with other drugs. These findings suggest that the bis-amides have significant potential to extend the arsenal of HCV therapeutics.

Carbonyl reductase 1 offers a novel therapeutic target to enhance leukemia treatment by arsenic trioxide.

Arsenic trioxide (As2O3) is used, in current practice, as an effective chemotherapeutic agent for acute promyelocytic leukemia (APL). However, the side effects and relatively low efficacy of As2O3 in treating other leukemias have limited its wider use in therapeutic applications. In the present study, we found that the expression of carbonyl reductase 1 (CBR1) affects the resistance to As2O3 in leukemias, including APL; As2O3 upregulated CBR1 expression at the transcriptional level by stimulating the activity of the transcription factor activator protein-1. Moreover, CBR1 overexpression was sufficient to protect cells against As2O3 through modulation of the generation of reactive oxygen species, whereas the attenuation of CBR1 was sufficient to sensitize cells to As2O3. A combination treatment with the specific CBR1 inhibitor hydroxy-PP-Me remarkably increased As2O3-induced apoptotic cell death compared with As2O3 alone, both in vitro and in vivo. These results were confirmed in primary cultured human acute and chronic myeloid leukemia cells, with no significant cell death observed in normal leukocytes. Taken together, our findings indicate that CBR1 contributes to the low efficacy of As2O3 and, therefore, is a rational target for the development of combination chemotherapy with As2O3 in diverse leukemias including APL.