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.

Terminal deoxynucleotidyl transferase (TdT) is overexpressed in some cancer types, where it drives the mutagenic repair of double strand breaks through non canonical non-homologous end joining pathway. The TdT enzyme belongs to the X family of polymerases, together with the DNA polymerase λ (pol λ) and β (pol β). However, TdT exclusively displays template-independent nucleotide polymerisation. Pursuing our studies in developing TdT inhibitors, herein we deepened the structure-activity relationships of new structural analogues of our previously identified hit compounds. The diketo hexenoic acid derivatives here analysed showed high selectivity towards TdT and inhibition potencies spanning from the low micromolar range to the nanomolar. Docking studies highlighted the chemical features involved in the TdT binding, well contributing to the rationalisation of the structural requirements needed for the enzymatic inhibition.

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.