Deuremidevir and Simnotrelvir-Ritonavir for the Treatment of COVID-19

Novel compounds with dual inhibition activity against SARS-CoV-2 critical enzymes RdRp and human TMPRSS2

COVID-19 caused major worldwide problems. The spread of variants and limited treatment encouraged the design of novel anti-SARS-CoV-2 compounds. A series of compounds RH1-23 were designed to dually target RNA-dependent RNA polymerase (RdRp) and transmembrane serine protease 2 (TMPRSS2). Compared to remdesivir, in vitro screening indicated the highest selectivity and potent activity of RH11-13 with half maximum inhibitory concentration (IC50) 3.9, 5.7, and 19.72 nM, respectively. RH11-12 showed superior inhibition activity against TMPRSS2 and RdRP with IC50 (1.7 and 4.2), and (6.1 and 4.42) nM, respectively. WaterMap analysis and molecular dynamics studies demonstrated the superior enzyme binding activity of RH11 and RH12. On Vero-E6 cells, RH11 and RH12 significantly inhibited the viral replication with 66 % and 63.2 %, and viral adsorption with 44 % and 65 %, alongside virucidal effect with 51.40 % and 90.5 %, respectively. Furthermore, the potent activity of RH12 was tested on TMPRSS2-expressing cells (Calu-3) compared to camostat. RH12 exhibited selectivity index (26.05) similar to camostat (28.01) and comparable to its SI on Vero-E6 cells (22.6). RH12 demonstrated also a significant inhibition of the viral adsorption on Calu-3 cells with 60 % inhibition at 30 nM. The designed compounds exhibited good physiochemical properties. These findings indicate a broad-spectrum antiviral efficacy of the designed compounds, particularly RH12, with a promise for further development.

Nonpeptidic Irreversible Inhibitors of SARS-CoV-2 Main Protease with Potent Antiviral Activity

SARS-CoV-2 infections pose a high risk for vulnerable patients. In this study, we designed benzoic acid halopyridyl esters bearing a variety of substituents as irreversible inhibitors of the main viral protease (Mpro). Altogether, 55 benzoyl chloro/bromo-pyridyl esters were synthesized, with broad variation of the substitution pattern on the benzoyl moiety. A workflow was employed for multiparametric optimization, including Mpro inhibition assays of SARS-CoV-2 and related pathogenic coronaviruses, the duration of enzyme inhibition, the compounds' stability versus glutathione, cytotoxicity, and antiviral activity. Several compounds showed IC50 values in the low nanomolar range, kinact/Ki values of >100,000 M-1 s-1 and high antiviral activity. High-resolution X-ray cocrystal structures indicated an important role of ortho-fluorobenzoyl substitution, forming a water network that stabilizes the inhibitor-bound enzyme. The most potent antiviral compound was the p-ethoxy-o-fluorobenzoyl chloropyridyl ester (PSB-21110, 29b, MW 296 g/mol; EC50 2.68 nM), which may serve as a lead structure for broad-spectrum anticoronaviral therapeutics.

Deuteration-Driven Photopharmacology: Deuterium-Labeled for Controlling Alpha 7 Nicotinic Acetylcholine Receptors

Photopharmacology is a powerful approach to investigate biological processes and overcomes the common therapeutic challenges in drug development. Enhancing the photopharmacology properties of photoswitches contributes to extend their applications. Deuteration, a tiny structural modification, makes it possible to improve the photopharmacology and photophysical properties of prototype compounds, avoiding extra complex chemical changes or constructing multicomponent systems. In this work, we developed a series of D-labeled azobenzenes to expand the azobenzene photoswitchable library and introduced the D-labeled azobenzene unit into the photoagonist of α7 nicotinic acetylcholine receptors (α7 nAChRs) to investigate the effects of deuteration in photopharmacology. Spectral data indicated that deuteration maintained most of the photophysical properties of azobenzenes. The D-labeled photoagonist exhibited good control of the activity of α7 nAChRs than the prototype photoagonist. These results confirmed that deuteration is a promising strategy to improve the photopharmacological properties.

Development of an active-site titrant for SARS-CoV-2 main protease as an indispensable tool for evaluating enzyme kinetics

A titrant for the SARS-CoV-2 main protease (Mpro) was developed that enables, for the first time, the exact determination of the concentration of the enzymatically active Mpro by active-site titration. The covalent binding mode of the tetrapeptidic titrant was elucidated by the determination of the crystal structure of the enzyme-titrant complex. Four fluorogenic substrates of Mpro, including a prototypical, internally quenched Dabcyl-EDANS peptide, were compared in terms of solubility under typical assay conditions. By exploiting the new titrant, key kinetic parameters for the Mpro-catalyzed cleavage of these substrates were determined.

Simnotrelvir as a potential treatment for COVID-19

INTRODUCTION

Simnotrelvir is a selective 3-chymotrypsin-like oral protease inhibitor with activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

AREAS COVERED

On 18 January 2024, results of a double-blind, randomized, placebo-controlled trial of simnotrelvir as a treatment for mild-to moderate COVID-19-were published, indicating the drug, when given in combination with ritonavir, shortened the time to resolution of symptoms.

EXPERT OPINION

Treatment options for most outpatients with mild-to-moderate COVID-19 are limited. The protease inhibitor nirmatrelvir in combination with ritonavir has proven effective in patients who are high risk for progression to severe COVID-19, but there are no approved therapies for standard-risk patients, who now comprise the majority of the population. Simnotrelvir appears to be effective in standard-risk patients, including those who have completed primary vaccination against COVID-19 and have received a booster dose. This manuscript examines the rationale for the development of simnotrelvir and explores how this drug may be used in the future to treat COVID-19.

On the origins of SARS-CoV-2 main protease inhibitors

In order to address the world-wide health challenge caused by the COVID-19 pandemic, the 3CL protease/SARS-CoV-2 main protease (SARS-CoV-2-Mpro) coded by its nsp5 gene became one of the biochemical targets for the design of antiviral drugs. In less than 3 years of research, 4 inhibitors of SARS-CoV-2-Mpro have actually been authorized for COVID-19 treatment (nirmatrelvir, ensitrelvir, leritrelvir and simnotrelvir) and more such as EDP-235, FB-2001 and STI-1558/Olgotrelvir or five undisclosed compounds (CDI-988, ASC11, ALG-097558, QLS1128 and H-10517) are undergoing clinical trials. This review is an attempt to picture this quite unprecedented medicinal chemistry feat and provide insights on how these cysteine protease inhibitors were discovered. Since many series of covalent SARS-CoV-2-Mpro inhibitors owe some of their origins to previous work on other proteases, we first provided a description of various inhibitors of cysteine-bearing human caspase-1 or cathepsin K, as well as inhibitors of serine proteases such as human dipeptidyl peptidase-4 or the hepatitis C protein complex NS3/4A. This is then followed by a description of the results of the approaches adopted (repurposing, structure-based and high throughput screening) to discover coronavirus main protease inhibitors.

Small-molecule anti-COVID-19 drugs and a focus on China's homegrown mindeudesivir (VV116)

The coronavirus disease 2019 (COVID-19) pandemic has stimulated tremendous efforts to develop therapeutic agents that target severe acute respiratory syndrome coronavirus 2 to control viral infection. So far, a few small-molecule antiviral drugs, including nirmatrelvir-ritonavir (Paxlovid), remdesivir, and molnupiravir have been marketed for the treatment of COVID-19. Nirmatrelvir-ritonavir has been recommended by the World Health Organization as an early treatment for outpatients with mild-to-moderate COVID-19. However, the existing treatment options have limitations, and effective treatment strategies that are cost-effective and convenient for tackling COVID-19 are still needed. To date, four domestically developed oral anti-COVID-19 drugs have been granted conditional market approval in China. These drugs include azvudine, simnotrelvir-ritonavir (Xiannuoxin), leritrelvir, and mindeudesivir (VV116). Preclinical and clinical studies have explored the efficacy and tolerability of mindeudesivir and supported its early use in mild-to-moderate COVID-19 cases at high risk for progression. In this review, we discuss the most recent findings regarding the pharmacological mechanism and therapeutic effects focusing on mindeudesivir and other small-molecule antiviral agents for COVID-19. These findings will expand our understanding and highlight the potential widespread application of China's homegrown anti-COVID-19 drugs.

Remdesivir Derivative VV116 Is a Potential Broad-Spectrum Inhibitor of Both Human and Animal Coronaviruses

Coronaviruses represent a significant threat to both human and animal health, encompassing a range of pathogenic strains responsible for illnesses, from the common cold to more severe diseases. VV116 is a deuterated derivative of Remdesivir with oral bioavailability that was found to potently inhibit SARS-CoV-2. In this work, we investigated the broad-spectrum antiviral activity of VV116 against a variety of human and animal coronaviruses. We examined the inhibitory effects of VV116 on the replication of the human coronaviruses HCoV-NL63, HCoV-229E, and HCoV-OC43, as well as the animal coronaviruses MHV, FIPV, FECV, and CCoV. The findings reveal that VV116 effectively inhibits viral replication across these strains without exhibiting cytotoxicity, indicating its potential for safe therapeutic use. Based on the results of a time-of-addition assay and an rNTP competitive inhibition assay, it is speculated that the inhibitory mechanism of VV116 against HCoV-NL63 is consistent with its inhibition of SARS-CoV-2. Our work presents VV116 as a promising candidate for broad-spectrum anti-coronavirus therapy, with implications for both human and animal health, and supports the expansion of its therapeutic applications as backed by detailed experimental data.

Efficacy and safety evaluation of Azvudine in the prospective treatment of COVID-19 based on four phase III clinical trials

Azvudine (FNC) is a synthetic nucleoside analog used to treat adult patients living with human immunodeficiency virus-1 (HIV-1) infection with high viral load. After phosphorylation, Azvudine inhibits RNA-dependent RNA polymerase, leading to the discontinuation of RNA chain synthesis in viruses. In addition, Azvudine is the first dual-target nucleoside oral drug worldwide to simultaneously target reverse transcriptase and viral infectivity factors in the treatment of HIV infection. On 9 August 2022, Azvudine was incorporated into the Guidelines for the Diagnosis and Treatment of Coronavirus Disease 2019 (version ninth) issued by the National Health Commission and the National Administration of Traditional Chinese Medicine. The recommended oral dose of Azvudine for the treatment of moderate coronavirus disease 2019 (COVID-19) is 5 mg once daily, and the duration of Azvudine treatment should not exceed 14 days. Four phase III clinical trials were performed during 2020-2022 to evaluate the efficacy and safety of Azvudine in the treatment of COVID-19. The results revealed that Azvudine could reduce nucleic acid-negative conversion time, viral load, and time to improvement in clinical conditions in patients with moderate COVID-19. In addition, Azvudine exhibited good safety and tolerance. Thereafter, Azvudine was incorporated into the Chinese guidelines and expert consensus for the treatment of COVID-19 and was highly approbated. Furthermore, Azvudine was also included in the Chinese guidelines for HIV infection.