Enhancing the antiviral potency of ER α-glucosidase inhibitor IHVR-19029 against hemorrhagic fever viruses in vitro and in vivo.

Targeting host functions essential for viral replication has been considered as a broad spectrum and resistance-refractory antiviral approach. However, only a few host functions have, thus far, been validated as broad-spectrum antiviral targets in vivo. ER α-glucosidases I and II have been demonstrated to be essential for the morphogenesis of many enveloped viruses, including members from four families of viruses causing hemorrhagic fever. In vivo antiviral efficacy of various iminosugar-based ER α-glucosidase inhibitors has been reported in animals infected with Dengue, Japanese encephalitis, Ebola, Marburg and influenza viruses. Herein, we established Huh7.5-derived cell lines with ER α-glucosidase I or II knockout using CRISPR/Cas9 and demonstrated that the replication of Dengue, Yellow fever and Zika viruses was reduced by only 1-2 logs in the knockout cell lines. The results clearly indicate that only a partial suppression of viral replication can possibly be achieved with a complete inhibition of ER-α-glucosidases I or II by their inhibitors. We therefore explore to improve the antiviral efficacy of a lead iminosugar IHVR-19029 through combination with another broad-spectrum antiviral agent, favipiravir (T-705). Indeed, combination of IHVR-19029 and T-705 synergistically inhibited the replication of Yellow fever and Ebola viruses in cultured cells. Moreover, in a mouse model of Ebola virus infection, combination of sub-optimal doses of IHVR-19029 and T-705 significantly increased the survival rate of infected animals. We have thus proved the concept of combinational therapeutic strategy for the treatment of viral hemorrhagic fevers with broad spectrum host- and viral- targeting antiviral agents.

Ester Prodrugs of IHVR-19029 with Enhanced Oral Exposure and Prevention of Gastrointestinal Glucosidase Interaction.

IHVR-19029 (6) is a lead endoplasmic reticulum α-glucosidases I and II inhibitor, which efficiently protected mice from lethal Ebola and Marburg virus infections via injection route, but suffered from low bioavailability and off-target interactions with gut glucosidases when administered orally. In an effort to improve efficacious exposure levels and avoid side effects, we designed and synthesized ester prodrugs. Not only were the prodrugs stable in simulated gastric and intestinal fluids and were inactive against glucosidases but they also exhibited antiviral activities against dengue virus infection in a cell based assay. Further in vitro evaluation showed that the bioconversion of the prodrugs is species dependent: in mice, the prodrugs were converted to 6 in the plasma and liver; while in human, the conversion occurred mainly in liver. An in vivo pharmacokinetic study in mice demonstrated that the tetrabutyrate prodrug 8 achieved the most improved overall exposure of 6 upon both oral and intravenous administration.

Novel substituted aminothiazoles as potent and selective anti-hepatocellular carcinoma agents.

Based on our previous identification of a disubstituted aminothiazole termed HBF-0079 with promising selective toxicity for HCC-derived cell lines versus non-HCC liver lines, a series of tri-substituted aminothiazole derivatives were prepared and evaluated. This work resulted in the discovery of isopropyl 4-(pyrazin-2-yl)-2-(pyrimidin-2-ylamino)thiazole-5-carboxylate, 14, which displayed EC50 value of 0.11µM and more than 450times of selectivity, and its methyl carbonate prodrug 24 with improved solubility in organic solvents. Furthermore, 14, was shown to reduce the proliferation of several liver cancer cells derived directly from patients.

2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one: a potent human NK1 receptor antagonist with multiple clearance pathways.

Hydroisoindoline 2 has been previously identified as a potent, brain-penetrant NK1 receptor antagonist with a long duration of action and improved profile of CYP3A4 inhibition and induction compared to aprepitant. However, compound 2 is predicted, based on data in preclinical species, to have a human half-life longer than 40 h and likely to have drug-drug-interactions (DDI), as 2 is a victim of CYP3A4 inhibition caused by its exclusive clearance pathway via CYP3A4 oxidation in humans. We now report 2-[(3aR,4R,5S,7aS)-5-{(1S)-1-[3,5-bis(trifluoromethyl)phenyl]-2-hydroxyethoxy}-4-(2-methylphenyl)octahydro-2H-isoindol-2-yl]-1,3-oxazol-4(5H)-one (3) as a next generation NK1 antagonist that possesses an additional clearance pathway through glucuronidation in addition to that via CYP3A4 oxidation. Compound 3 has a much lower propensity for drug-drug interactions and a reduced estimated human half-life consistent with once daily dosing. In preclinical species, compound 3 has demonstrated potency, brain penetration, and a safety profile similar to 2, as well as excellent pharmacokinetics.

Tetrahydroindolizinone NK1 antagonists.

A new class of potent NK(1) receptor antagonists with a tetrahydroindolizinone core has been identified. This series of compounds demonstrated improved functional activities as compared to previously identified 5,5-fused pyrrolidine lead structures. SAR at the 7-position of the tetrahydroindolizinone core is discussed in detail. A number of compounds displayed high NK(1) receptor occupancy at both 1 h and 24 h in a gerbil foot tapping model. Compound 40 has high NK(1) binding affinity, good selectivity for other NK receptors and promising in vivo properties. It also has clean P(450) inhibition and hPXR induction profiles.