Described herein are the discovery and structure-activity relationship (SAR) studies of the third-generation 4-H heteroaryldihydropyrimidines (4-H HAPs) featuring the introduction of a C6 carboxyl group as novel HBV capsid inhibitors. This new series of 4-H HAPs showed improved anti-HBV activity and better drug-like properties compared to the first- and second-generation 4-H HAPs. X-ray crystallographic study of analogue 12 (HAP_R01) with Cp149 Y132A mutant hexamer clearly elucidated the role of C6 carboxyl group played for the increased binding affinity, which formed strong hydrogen bonding interactions with capsid protein and coordinated waters. The representative analogue 10 (HAP_R10) was extensively characterized in vitro (ADMET) and in vivo (mouse PK and PD) and subsequently selected for further development as oral anti-HBV infection agent.

Targeting the capsid protein of hepatitis B virus (HBV) and thus interrupting normal capsid formation have been an attractive approach to block the replication of HBV viruses. We carried out multidimensional structural optimizations based on the heteroaryldihydropyrimidine (HAP) analogue Bay41-4109 (1) and identified a novel series of HBV capsid inhibitors that demonstrated promising cellular selectivity indexes, metabolic stabilities, and in vitro safety profiles. Herein we disclose the design, synthesis, structure-activity relationship (SAR), cocrystal structure in complex with HBV capsid proteins and in vivo pharmacological study of the 4-methyl HAP analogues. In particular, the (2S,4S)-4,4-difluoroproline substituted analogue 34a demonstrated high oral bioavailability and liver exposure and achieved over 2 log viral load reduction in a hydrodynamic injected (HDI) HBV mouse model.

ATG4B or autophagin-1 is a cysteine protease that cleaves ATG8 family proteins. ATG4B plays essential roles in the autophagosome formation and the autophagy pathway. Herein we disclose the design and structural modifications of a series of fluoromethylketone (FMK)-based peptidomimetics as highly potent ATG4B inhibitors. Their structure−activity relationship (SAR) and protease selectivity are also discussed.KEYWORDS: ATG4B, autophagy, covalent inhibitor, fluoromethylketone, peptidomimetics A utophagy is an evolutionarily conserved process essential for cell homeostasis and housekeeping by catabolizing aggregated proteins and damaged cellular components. 1 The hallmark of autophagy is the formation of autophagosomes and subsequent fusion with lysosomes to achieve degradation of their contents. Dysregulation of autophagy has been recently described in the pathogenesis of a variety of diseases such as cancer, neurodegenerative and metabolic disorders, and viral infections. 2,3 Modulation of autophagy has become a very active area of preclinical and clinical research, and particularly, there is high interest to identify potent and specific autophagy inhibitors. 4 ATG4 or autophagins are a class of cytosolic cysteine proteases that cleave ATG8 family proteins, such as light chain 3 (LC3). ATG4 plays essential roles in the formation and maturation of autophagosomes. 5,6 Among all four human ATG4 orthologues, ATG4B is functionally dominant, and it is the sole enzyme reported to efficiently cleave LC3 precursors and to deconjugate lipid from membrane bound LC3-phosphatidylethanolamine (LC3-PE). 7 ATG4B has been considered as a potential therapeutic target in the development of chemosensitizer for the treatment of certain cancer types. Recently, a number of small molecule ATG4B inhibitors such as Z-L-Phe-chloromethylketone and NSC185058 were reported to have modulatory effects on the autophagy process. 8−10 However, because of its high chemical reactivity, the chloromethylketone moiety is usually associated with significant cytotoxicity. NSC185058, however, is only a weak ATG4B inhibitor with an IC 50 of 51 μM in an assay detecting the cleavage of LC3-GST. 10 Previously, we reported the identification of Z-FA-FMK (1, Figure 1) as a covalent active-site directed ATG4B inhibitor from a TR-FRET based focused library screening. 11 The hit expansion of 1 led to the discovery of Z-FG-FMK (2), which was 10-times more potent than 1 with an IC 50 of 1.2 μM in the biochemical assay. 11 Herein we disclose the structure-guided optimization of 2 toward highly potent fluoromethylketone (FMK)-based ATG4B inhibitors.As an early step in the autophagosome formation, ATG4B cleaves proLC3 to expose the C-terminal Gly120 for subsequent PE-conjugation and autophagosome membrane insertion. 5 The cocrystal structures of catalytically inert C74S or

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Hemagglutinin (HA) of the influenza virus plays a crucial role in the early stage of the viral life cycle by binding to sialic acid on the surface of host epithelial cells and mediating fusion between virus envelope and endosome membrane for the release of viral genomes into the cytoplasm. To initiate virus fusion, endosome pH is lowered by acidification causing an irreversible conformational change of HA, which in turn results in a fusogenic HA. In this study, we describe characterization of an HA inhibitor of influenza H1N1 viruses, RO5464466. One-cycle time course study in MDCK cells showed that this compound acted at an early step of influenza virus replication. Results from HA-mediated hemolysis of chicken red blood cells and trypsin sensitivity assay of isolated HA clearly showed that RO5464466 targeted HA. In cell-based assays involving multiple rounds of virus infection and replication, RO5464466 inhibited an established influenza infection. The overall production of progeny viruses, as a result of the compound's inhibitory effect on fusion, was dramatically reduced by 8 log units when compared with a negative control. Furthermore, RO5487624, a close analogue of RO5464466, with pharmacokinetic properties suitable for in vivo efficacy studies displayed a protective effect on mice that were lethally challenged with influenza H1N1 virus. These results might benefit further characterization and development of novel anti-influenza agents by targeting viral hemagglutinin.