Synthesis, biological evaluation and in silico modeling of novel pan-genotypic NS5A inhibitors

Discovery of In Vivo Active Sphingosine-1-phosphate Transporter (Spns2) Inhibitors

Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with five G-protein-coupled receptors (S1P1-5) to regulate cellular signaling pathways. S1P export is facilitated by Mfsd2b and spinster homologue 2 (Spns2). While mouse genetic studies suggest that Spns2 functions to maintain lymph S1P, Spns2 inhibitors are necessary to understand its biology and to learn whether Spns2 is a viable drug target. Herein, we report a structure-activity relationship study that identified the first Spns2 inhibitor 16d (SLF1081851). In vitro studies in HeLa cells demonstrated that 16d inhibited S1P release with an IC50 of 1.93 μM. Administration of 16d to mice and rats drove significant decreases in circulating lymphocyte counts and plasma S1P concentrations, recapitulating the phenotype observed in mice made deficient in Spns2. Thus, 16d has the potential for development and use as a probe to investigate Spns2 biology and to determine the potential of Spns2 as a drug target.

Recent advancement in small molecules as HCV inhibitors

Hepatitis C virus (HCV) has caused a considerable threat to human health. To date, no treatments are without side effects. The proteins and RNA associated with HCV have specific functions during the viral life cycle. The vulnerabilities to virus are associated with those proteins or RNA. Thus, targeting these proteins and RNA is an efficient strategy to develop anti-HCV therapeutics. The treatment for HCV-infected patients has been greatly improved after the approval of direct-acting antivirals (DAAs). However, the cost of DAAs is unusually high, which adds to the economic burden on patients with chronic liver diseases. So far, many efforts have been devoted to the development of small molecules as novel HCV inhibitors. Investigations on the inhibitory activities of these small molecules have involved the target identification and the mechanism of action. In this mini-review, these small molecules divided into four kinds were elaborated, which focused on their targets and structural features. Furthermore, we raised the current challenges and promising prospects. This mini-review may facilitate the development of small molecules with improved activities targeting HCV based on the chemical scaffolds of HCV inhibitors.

Pleiotropic Effects of Influenza H1, H3, and B Baloxavir-Resistant Substitutions on Replication, Sensitivity to Baloxavir, and Interferon Expression

Baloxavir is an anti-influenza endonuclease inhibitor that targets the polymerase acidic (PA) protein of influenza A and B viruses. Our knowledge regarding the pleiotropic effects of baloxavir resistance-associated substitutions is limited. We generated recombinant A/California/04/09 (H1N1)-, A/Hong Kong/218849/2006 (H3N2)-, and B/Victoria/504/2000-like viruses that contained PA substitutions identified in baloxavir clinical trials and surveillance that could potentially be associated with baloxavir resistance. We characterized their susceptibility to baloxavir, impact on polymerase activity, viral growth, and ability to induce interferon (IFN) and IFN-stimulated genes expression in vitro. Four PA substitutions, H1N1 I38L/T, E199D, and B G199R, significantly reduced the sensitivity of the recombinant viruses to baloxavir (14.1-fold). We confirmed our findings by using the luciferase-based ribonucleoprotein minigenome assay and by using virus yield reduction assay in Calu-3 and normal human bronchial epithelial (NHBE) cells. We observed that I38L and E199D resulted in decreased viral replication of the H1N1 wild-type virus (1.4-fold) but the H1N1 I38T and B G199R substitutions did not significantly alter replication capacity in Calu-3 cells. In addition, H1N1 variants with PA I38L/T and E199D induced significantly higher levels of IFNB1 gene expression compared to the wild-type virus (4.2-fold). In contrast, the B variant, G199R, triggered the lowest levels of IFN genes in Calu-3 cells (1.6-fold). Because baloxavir is a novel anti-influenza therapeutic agent, identifying and characterizing substitutions associated with reduced sensitivity to baloxavir, as well as the impact of these substitutions on viral fitness, is paramount to the strategic implementation of this novel countermeasure.