Widespread latent herpes viral infections within a population can lead to the development of co-infections in HIV-infected patients. These infections are not particularly dangerous for healthy individuals and often occur with minimal symptoms, but for those who are immunocompromised, these infections can accelerate the acute phase of HIV infection and AIDS. Thus, the idea of designing compounds that could combine activity against HIV and co-infections would seem promising. In that regard, eleven compounds were synthesized that represent conjugates of non-nucleoside HIV reverse transcriptase inhibitors and nucleoside inhibitors of the herpes family viruses with the hope that these novel heterodimers will result in dual activity against HIV and concomitant herpes virus infections.
The SARS-CoV-2 betacoronavirus pandemic has claimed more than 6.5 million lives and, despite the development and use of COVID-19 vaccines, remains a major global public health problem. The development of specific drugs for the treatment of this disease remains a very urgent task. In the context of a repurposing strategy, we previously screened a library of nucleoside analogs showing different types of biological activity against the SARS-CoV-2 virus. The screening revealed compounds capable of inhibiting the reproduction of SARS-CoV-2 with EC50 values in the range of 20–50 µM. Here we present the design and synthesis of various analogs of the leader compounds, the evaluation of their cytotoxicity and antiviral activity against SARS-CoV-2 in cell cultures, as well as experimental data on RNA-dependent RNA polymerase inhibition. Several compounds have been shown to prevent the interaction between the SARS-CoV-2 RNA-dependent RNA polymerase and the RNA substrate, likely inhibiting virus replication. Three of the synthesized compounds have also been shown to inhibit influenza virus. The structures of these compounds can be used for further optimization in order to develop an antiviral drug.
The great interest in studying the structure of human purine nucleoside phosphorylase (hPNP) and the continued search for effective inhibitors is due to the importance of the enzyme as a target in the therapy of T-cell proliferative diseases. In addition, hPNP inhibitors are used in organ transplant surgeries to provide immunodeficiency during and after the procedure. Previously, we showed that members of the well-known fleximer class of nucleosides are substrates of E. coli PNP. Fleximers have great promise as they have exhibited significant biological activity against a number of viruses of pandemic concern. Herein, we describe the synthesis and inhibition studies of a series of new fleximer compounds against hPNP and discuss their possible binding mode with the enzyme. At a concentration of 2 mM for the flex-7-deazapurines 1–4, a decrease in enzymatic activity by more than 50% was observed. 4-Amino-5-(1H-pyrrol-3-yl)pyridine 2 was the best inhibitor, with a Ki = 0.70 mM. Docking experiments have shown that ligand 2 is localized in the selected binding pocket Glu201, Asn243 and Phe200. The ability of the pyridine and pyrrole fragments to undergo rotation around the C–C bond allows for multiple binding modes in the active site of hPNP, which could provide several plausible bioactive conformations.
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