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.

It has been more than four years since the first report of SARS‐CoV‐2, the virus responsible for the coronavirus disease 2019 (COVID‐19) pandemic, the scientific community is focused on vaccine development in an exceptionally rapid time frame, as well as the evaluation of a wide range of potential treatments in clinical trials, a few of which have also reached the market. However, these drugs are characterized by several limits (including low response to treatment in some patients, low effectiveness against the new variants, severe side effects, etc.), thus underscoring the need to speed up the research. Among potential antiviral targets, the SARS‐CoV‐2 nonstructural protein 13 (nsp13) is highly promising thanks to its pivotal role in viral replication. Pursuing the studies on the development of nsp13 inhibitors, herein, the design, synthesis, and biological evaluation of new SARS‐CoV‐2 nsp13 inhibitors are reported. In general, the newly designed dikehexenoic derivatives are proven active against both the enzymatic activities showing measurable IC₅₀ under 30 μM concentration, while the diketobutanoic series shows less promising results. Moreover, the tested compounds are capable of blocking viral replication without exerting cytotoxicity. Docking studies predict their binding into an allosteric pocket within the RecA2 domain.

COVID-19 pandemic stimulated tremendous efforts to develop therapeutic strategies targeting SARS-CoV-2, leading to the evaluation of a wide range of potential treatments in clinical trials. However, effective therapeutics remain elusive when the development of new variants and the limits of antiviral drugs is considered. Therefore, the development of antiviral drugs against SARS-CoV-2 is of paramount importance. Among potential drug targets, the SARS-CoV-2 nsp13 is highly attractive thanks to its pivotal role in viral replication. Pursuing our studies on the development of nsp13 inhibitors, in this work we describe the design, synthesis, and biological evaluation of novel inhibitors targeting SARS-CoV-2 nsp13. The newly designed N-benzyl indole derivatives were active against both enzymatic activities showing measurable IC₅₀ under 30 μM concentration, while N-alkyl derivatives showed less promising results. Interestingly, the tested compounds blocked viral replication with no cytotoxicity. Docking studies predicted their binding into an allosteric conserved site located in the RecA2 domain.

The SARS-CoV-2 pandemic has posed a tremendous burden globally, highlighting the urgent need for new effective antivirals that are possibly useful against future emerging Coronaviruses (hCoVs). In this context, major efforts were focused on the inhibition of highly conserved and essential targets playing a pivotal role in viral replication. Among them, SARS-CoV-2 nsp13 stands out, being the most conserved enzyme within hCoVs. Following our previous reports describing the identification of indole-based diketo acid (DKA) derivatives as SARS-CoV-2 nsp13 inhibitors endowed with antiviral activity, we applied a scaffold hopping strategy to identify new nsp13 inhibitors. Therefore, we investigated a series of 4-phenyl pyrrolyl DKAs and their structural analogs characterized by molecular simplification or DKA isosteric replacement. The derivatives showed potency against both nsp13-associated activities exhibiting measurable IC₅₀s in the low micromolar/submicromolar range, highlighting a promising dual inhibitory profile accordingly. Structure–activity relationship (SAR) studies were performed, highlighting the main structural features increasing the activity of the different compound classes. Interestingly, SAR trends were confirmed in the presence of the BSA/TCEP system despite variations in potency. To shed light on the interaction of the best acting compounds 13b, 15a, and 17d, docking studies were performed, suggesting a putative binding mode in agreement with our previous findings.

Given its pivotal role in the viral life cycle, blocking integrase (IN) through IN strand transfer inhibitors (INSTIs) represented a breakthrough in the treatment of HIV infection, establishing these antiretroviral regimens as first‐line options against AIDS. However, the onset of drug‐resistant strains has challenged the efficacy of INSTIs, demanding new efforts in the search for therapeutic tools that work through alternative modes of action. In this context, the discovery of allosteric IN inhibitors (ALLINIs) has highlighted new opportunities to target IN beyond its active site, enhancing antiviral efficacy and the genetic barrier to resistance. Extensive drug discovery campaigns have resulted in the development of effective ALLINIs with both in vitro and in vivo efficacy, two of which are advancing in clinical trials as next‐generation therapeutic tools. Nevertheless, advancements in structural biology have critically aided in elucidating the underlying effects of ALLINIs, highlighting a complex, multimodal mode of action that ultimately yields defects in virion maturation. This review focuses on ALLINIs, providing a comprehensive overview of major drug discovery efforts devoted to this field, with an emphasis on the medicinal chemistry and structural biology findings that have revealed unprecedented opportunities for developing innovative and effective anti‐HIV drugs.