The COVID-19 pandemic, driven by the rapid evolution of the SARS-CoV-2 virus, presents ongoing challenges to global public health. SARS-CoV-2 is characterized by rapidly evolving mutations, especially in (but not limited to) the spike protein, complicating predictions about its evolutionary trajectory. These mutations have significantly affected transmissibility, immune evasion, and vaccine efficacy, leading to multiple pandemic waves with over half a billion cases and seven million deaths globally. Despite several strategies, from rapid vaccine development and administration to the design and availability of antivirals, including monoclonal antibodies, already having been employed, the persistent circulation of the virus and the emergence of new variants continue to result in high case numbers and fatalities. In the past four years, immense research efforts have contributed much to our understanding of the viral pathogenesis mechanism, the COVID-19 syndrome, and the host–microbe interactions, leading to the development of effective vaccines, diagnostic tools, and treatments. The focus of this review is to provide a comprehensive analysis of the functional impact of mutations on diagnosis, treatments, and vaccine effectiveness. We further discuss vaccine safety in pregnancy and the implications of hybrid immunity on long-term protection against infection, as well as the latest developments on a pan-coronavirus vaccine and nasal formulations, emphasizing the need for continued surveillance, research, and adaptive public health strategies in response to the ongoing SARS-CoV-2 evolution race.

It has been more than four years since the first report of SARS-CoV-2, and humankind has experienced a pandemic with an unprecedented impact. Moreover, the new variants have made the situation even worse. Among viral enzymes, the SARS-CoV-2 main protease (M^pro) has been deemed a promising drug target vs. COVID-19. Indeed, M^pro is a pivotal enzyme for viral replication, and it is highly conserved within coronaviruses. It showed a high extent of conservation of the protease residues essential to the enzymatic activity, emphasizing its potential as a drug target to develop wide-spectrum antiviral agents effective not only vs. SARS-CoV-2 variants but also against other coronaviruses. Even though the FDA-approved drug nirmatrelvir, a M^pro inhibitor, has boosted the antiviral therapy for the treatment of COVID-19, the drug shows several drawbacks that hinder its clinical application. Herein, we report the synthesis of new thiazolidine-4-one derivatives endowed with inhibitory potencies in the micromolar range against SARS-CoV-2 M^pro. In silico studies shed light on the key structural requirements responsible for binding to highly conserved enzymatic residues, showing that the thiazolidinone core acts as a mimetic of the Gln amino acid of the natural substrate and the central role of the nitro-substituted aromatic portion in establishing π-π stacking interactions with the catalytic His-41 residue.

Background: Antimicrobial resistance is a growing global health concern that requires multiple strategies to be tackled effectively. While the discovery of new antimicrobial molecules is essential, the repurposing of existing compounds also plays a significant role. Standard methods to evaluate antimicrobial efficacy, regulated by the Committee on Antimicrobial Susceptibility Testing (EUCAST) and the Clinical and Laboratory Standards Institute (CLSI), such as the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), are available. However, several potential antimicrobics show interference with these standard methods, resulting in underestimated activity and their premature dismissal from further studies. This work compares reference methods in evaluating different compounds with unique physico-chemical characteristics. We aim to demonstrate that combining different susceptibility tests is mandatory for a successful preclinical screening of antimicrobial compounds. Methods: A selection of substances including natural extracts, both free and in the form of nanocomposites with fumed silica, ionic liquids, ozonated oils, commercial and pure antibiotics, was tested using broth microdilution, disk diffusion, and agar dilution. These methods were chosen following EUCAST and CLSI guidelines, and comparisons were made to evaluate their applicability and limitations for non-conventional substances. Results: The study highlighted significant variability in the outcomes depending on the method used, especially for substances with intrinsic properties such as high viscosity, poor solubility, or specific interactions with the testing medium. In several cases, the use of a single standard method failed to accurately reflect the real antimicrobial activity, leading to potential misinterpretation of effectiveness. Conclusions: A combined methodological approach is recommended to overcome the limitations of individual techniques. The integration of multiple reference methods offers a more accurate screening strategy for identifying and characterizing new and repurposed antimicrobials.

The spread of Human Immunodeficiency Virus (HIV) still represents a global public health issue of major concern, and would benefit from unveiling unique viral features as targets for drug design. In this respect, HIV-1 integrase (IN), due to the absence of homologs in human cells, is a popular target for the synthesis of novel selective compounds. Moreover, as drug-resistant viral strains are rapidly evolving, the development of novel allosteric inhibitors is acutely required. Recently, we have observed that Kuwanon-L, quinazolinones and thienopyrimidinones containing at least one polyphenol unit, effectively inhibited HIV-1 IN activity. Thus, in the present research, novel dihydroxyphenyl-based thienopyrimidinone derivatives were investigated for their LEDGF/p75-dependent IN inhibitory activity. Our findings indicated a close correlation between the position of the OH group on the phenyl moiety and IN inhibitory activity of these compounds. As catechol may be involved in cytotoxicity, its replacement by other aromatic scaffolds was also exploited. As a result, compounds 21–23, 25 and 26 with enhanced IN inhibitory activity provided good lead candidates, with 25 being the most selective for IN. Lastly, UV spectrometric experiments suggested a plausible allosteric mode of action, as none of the thienopirimidinones showed Mg²⁺ chelation properties otherwise typical of IN strand transfer inhibitors (INSTIs).