Broad-spectrum coronavirus 3C-like protease peptidomimetic inhibitors effectively block SARS-CoV-2 replication in cells: Design, synthesis, biological evaluation, and X-ray structure determination.

Despite the approval of vaccines, monoclonal antibodies and restrictions during the pandemic, the demand for new efficacious and safe antivirals is compelling to boost the therapeutic arsenal against the COVID-19. The viral 3-chymotrypsin-like protease (3CLpro) is an essential enzyme for replication with high homology in the active site across CoVs and variants showing an almost unique specificity for Leu-Gln as P2-P1 residues, allowing the development of broad-spectrum inhibitors. The design, synthesis, biological activity, and cocrystal structural information of newly conceived peptidomimetic covalent reversible inhibitors are herein described. The inhibitors display an aldehyde warhead, a Gln mimetic at P1 and modified P2-P3 residues. Particularly, functionalized proline residues were inserted at P2 to stabilize the ß-turn like bioactive conformation, modulating the affinity. The most potent compounds displayed low/sub-nM potency against the 3CLpro of SARS-CoV-2 and MERS-CoV and inhibited viral replication of three human CoVs, i.e. SARS-CoV-2, MERS-CoV, and HCoV 229 in different cell lines. Particularly, derivative 12 exhibited nM-low µM antiviral activity depending on the virus, and the highest selectivity index. Some compounds were co-crystallized with SARS-CoV-2 3CLpro validating our design. Altogether, these results foster future work toward broad-spectrum 3CLpro inhibitors to challenge CoVs related pandemics.

Efficacy of selective histone deacetylase 6 inhibition in mouse models of Pseudomonas aeruginosa infection: A new glimpse for reducing inflammation and infection in cystic fibrosis.

The latest studies identified the histone deacetylase (HDAC) class of enzymes as strategic components of the complex molecular machinery underlying inflammation in cystic fibrosis (CF). Compelling new support has been provided for HDAC6 isoform as a key player in the generation of the dysregulated proinflammatory phenotype in CF, as well as in the immune response to the persistent bacterial infection accompanying CF patients. We herein provide in vivo proof-of-concept (PoC) of the efficacy of selective HDAC6 inhibition in contrasting the pro-inflammatory phenotype in a mouse model of chronic P. aeruginosa respiratory infection. Upon careful selection and in-house re-profiling (in vitro and cell-based assessment of acetylated tubulin level through Western blot analysis) of three potent and selective HDAC6 inhibitors as putative candidates for the PoC, we engaged the best performing compound 2 for pre-clinical studies. Compound 2 demonstrated no toxicity and robust anti-inflammatory profile in a mouse model of chronic P. aeruginosa respiratory infection upon repeated aerosol administration. A significant reduction of leukocyte recruitment in the airways, in particular neutrophils, was observed in compound 2-treated mice in comparison with the vehicle; moreover, quantitative immunoassays confirmed a significant reduction of chemokines and cytokines in lung homogenate. This effect was also associated with a modest reduced bacterial load after compound 2-treatment in mice compared to the vehicle. Our study is of particular significance since it demonstrates for the first time the utility of selective drug-like HDAC6 inhibitors in a relevant in vivo model of chronic P. aeruginosa infection, thus supporting their potential application for reverting CF phenotype.

Chasing a Breath of Fresh Air in Cystic Fibrosis (CF): Therapeutic Potential of Selective HDAC6 Inhibitors to Tackle Multiple Pathways in CF Pathophysiology.

Compelling new support has been provided for histone deacetylase isoform 6 (HDAC6) as a common thread in the generation of the dysregulated proinflammatory and fibrotic phenotype in cystic fibrosis (CF). HDAC6 also plays a crucial role in bacterial clearance or killing as a direct consequence of its effects on CF immune responses. Inhibiting HDAC6 functions thus eventually represents an innovative and effective strategy to tackle multiple aspects of CF-associated lung disease. In this Perspective, we not only showcase the latest evidence linking HDAC(6) activity and expression with CF phenotype but also track the new dawn of HDAC(6) modulators in CF and explore potentialities and future perspectives in the field.