Certain nucleoside/nucleotide reverse transcriptase (RT) inhibitors (NRTIs) are effective against HIV-1 and HBV. However, both viruses often acquire NRTI resistance, making it crucial to develop more potent agents that offer profound viral suppression. We report here that 4′-C-cyano-2-amino-2′-deoxyadenosine (CAdA) is a novel highly potent inhibitor of both HBV (IC50=0.4 nM) and HIV-1 (IC50=0.4 nM). In contrast, the approved anti-HBV NRTI entecavir (ETV) potently inhibits HBV (IC50=0.7 nM) but is much less active against HIV-1 (IC50=1,000 nM). Similarly, the highly potent HIV-1 inhibitor 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA) (IC50=0.3 nM) is less active against HBV (IC50=160 nM). Southern analysis using Huh-7 cells transfected with HBV-containing plasmids demonstrated that CAdA was potent against both wild-type (IC50=7.2 nM) and ETV-resistant HBV (IC50=69.6 nM for HBVETV-RL180M/S202G/M204V), whereas ETV failed to reduce HBVETV-RL180M/S202G/M204V DNA even at 1 μM. Once daily peroral administration of CAdA reduced HBVETV-RL180M/S202G/M204V viremia (p=0.0005) in human-liver-chimeric/HBVETV-RL180M/S202G/M204V-infected mice, while ETV completely failed to reduce HBVETV-RL180M/S202G/M204V viremia. None of the mice had significant drug-related body-weight or serum human-albumin concentration changes. Molecular modeling suggests that a shallower HBV-RT hydrophobic pocket at the polymerase active site can better accommodate the slightly shorter 4′-cyano of CAdA-triphosphate (TP), but not the longer 4′-ethynyl of EFdA-TP. In contrast, the deeper HIV-1-RT pocket can efficiently accommodate the 4′-substitutions of both NRTIs. The ETV-TP’s cyclopentyl ring can bind more efficiently at the shallow HBV-RT binding pocket. Conclusion: These data provide insights on the structural and functional associations of HBV- and HIV-1-RTs and show that CAdA may offer new therapeutic options for HBV patients.

These findings indicate that cardiac chymase plays an important role after MI and this finding may provide a novel therapeutic target in post-MI treatment.

No abstract

COVID-19 caused by SARS-CoV-2 has continually been serious threat to public health worldwide. While a few anti-SARS-CoV-2 therapeutics are currently available, their antiviral potency is not sufficient. Here, we identify two orally available 4-fluoro-benzothiazole-containing small molecules, TKB245 and TKB248, which specifically inhibit the enzymatic activity of main protease (Mpro) of SARS-CoV-2 and significantly more potently block the infectivity and replication of various SARS-CoV-2 strains than nirmatrelvir, molnupiravir, and ensitrelvir in cell-based assays employing various target cells. Both compounds also block the replication of Delta and Omicron variants in human-ACE2-knocked-in mice. Native mass spectrometric analysis reveals that both compounds bind to dimer Mpro, apparently promoting Mpro dimerization. X-ray crystallographic analysis shows that both compounds bind to Mpro’s active-site cavity, forming a covalent bond with the catalytic amino acid Cys-145 with the 4-fluorine of the benzothiazole moiety pointed to solvent. The data suggest that TKB245 and TKB248 might serve as potential therapeutics for COVID-19 and shed light upon further optimization to develop more potent and safer anti-SARS-CoV-2 therapeutics.

Accession no.Y00433 cDNAs encoding human glutathione peroxidase were isolated from a liver library prepared as described (1) by hybridization with a synthetic oligonucleotide (shown with the closed bar) to the 5' and 3' ends of the mouse genomic DNA sequence reported elsewhere (2). The sequence of 1134 bp minus the poly A tail of the longest cDNA clone is presented below with the predicted amino acid sequence. An asterix indicates the selenocystein at the position of the in-frame TGA codon. Comparison of our data with those of mouse (2) revealed 84% homology at the nucleotide level and 87% homology at the amino acid level.