Marco Leusciatti

The continuous emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has challenged the durability of vaccine-mediated protection, reinforcing the need for broad-spectrum antiviral agents. Herein, we performed a structure- and dynamics-driven virtual screening to identify novel small-molecule inhibitors of SARS-CoV-2 cell entry by targeting a conserved pocket within the S2 subunit of the spike glycoprotein domain. Extensive molecular dynamics simulations of the S2 domain revealed a druggable binding pocket close to the fusion peptide site. Consensus pharmacophore-guided virtual screening of ∼900,000 compounds yielded 11 candidates selected for biological evaluation. The selected compounds reduced SARS-CoV-2 infection in vitro at nanomolar concentrations against different variants with an increased selectivity index. Moreover, viral-cell entry and mechanistic experiments support the selective inhibition of the early steps of viral fusion. Finally, in silico evolutionary analyses showed good conservation of the pharmacophore region among different SARS-related coronaviruses. Our results provide a basis for further optimization studies on novel antifusion SARS-CoV-2 inhibitors with potential cross-clade antiviral activity.

From July 2022, a novel Echovirus 11 (E11) variant has been associated with severe neonatal infections and liver failure. Currently, there are no vaccines or antiviral options for the targeted treatment of non-polio enterovirus (EV) infections; therefore, anti-EV drugs are urgently needed. In this study, the putative anti-E11 activity of two isoxzoline-carbocyclic monophosphate nucleotides (4a and 4b) was evaluated in vitro by cytopathic effect (CPE) reduction in VERO 76 cells and qRT-PCR. Treatment with nucleotide 4a at 25 and 50 μM successfully diminished the CPE caused by E11 by 90% and 75%, respectively, and induced a reduction in viral RNA in the supernatant by 72% and 89%. In contrast, the treatment with 25 and 50 μM of 4b caused a minor inhibition of CPE (58 and 38%), and no significant E11 RNA level changes were observed. A time course viral progeny production assay was performed to assess the inhibitory effect of nucleotide 4a on E11 infection progression. Compared to the control, the treated group showed a significant drop in viral RNA levels, with reductions of 43% at 10 h, 65% at 24 h, and 96% at 48 h post-infection. The results showed the extensive antiviral properties of the monophosphate nucleotide 4a in vitro. Moreover, a retrospective molecular docking study strongly supports that nucleotide 4a is an RdRp inhibitor capable of decreasing E11 genome replication and virus particle formation in VERO 76 cells.

Cyclopenta[d]isoxazoline aminols were used for the synthesis of β-turn mimics. The peptide chain choice ascertained the influence of their structural features on the applicability/reliability/robustness of these scaffolds as β-turn inducers and their limitations. The amino acid selection as well as steric demands can favor or disfavor the structure folding and the correct design of the peptide chains deeply influences the potential use of these nitrosocarbonyl-based compounds as turn-inducers.

The generation and trapping of two new nitrosocarbonyl intermediates bearing carbohydrate-based chiral substituents is achieved by the mild oxidation of the corresponding nitrile oxides with tertiary amine N-oxides. Their capture with suitable dienes and alkenes afforded the corresponding hetero Diels–Alder cycloadducts and ene adducts from fair to excellent yields. The entire methodology looks highly promising by the easy conversion of aldoximes into hydroxymoyl halides, widening the access to nitrosocarbonyls, versatile tools in organic synthesis.