Serial viral load analysis by DDPCR to evaluate FNC efficacy and safety in the treatment of mild cases of COVID-19.

Introduction: The SARS-CoV-2 outbreak has threatened the human population globally as the numbers of reinfection cases even after large-scale vaccination. Trials have been carried out to find drugs effective in fighting the disease, as COVID-19 is being considered a treatable disease only after we have antivirals. A clinical candidate originally developed for HIV treatment, AZVUDINE (FNC), is a promising drug in the treatment of COVID-19. Methods: To predict the clinical outcome of COVID-19, we examined the course of viral load, every 48 h, by RT-PCR, and disease severity using an antiviral drug, FNC, with 281 participants. A randomized clinical trial was performed to evaluate the efficacy of FNC added to standard treatment, compared with placebo group added to standard treatment, for patients with mild COVID-19. RT-qPCR and ddPCR were applied to estimate the viral load in samples from patients. Also, the clinical improvement was evaluated as well as the liver and kidney function. Results and discussion: Notably, the FNC treatment in the mild COVID-19 patients may shorten the time of the nucleic acid negative conversion (NANC) versus placebo group. In addition, the FNC was effective in reducing the viral load of these participants. The present clinical trial results showed that the FNC accelerate the elimination of the virus in and could reduce treatment time of mild patients and save a lot of medical resources, making it a strong candidate for the outpatient and home treatment of COVID-19. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT05033145, identifier NCT05033145.

4'-Modified Nucleosides for Antiviral Drug Discovery: Achievements and Perspectives.

Modified nucleosides show therapeutic promise for antiviral therapies. However, issues including the emergence of drug resistance, toxicity, and coinfections have posed new challenges for nucleoside-based antiviral drug discovery, particularly in the era of the coronavirus disease 2019 (COVID-19) pandemic. Chemical manipulation could impact the antiviral potency, safety, and drug resistance of nucleosides. Generally, modified nucleosides are difficult to recognize by intracellular important enzymes as substrates and thus exhibit low toxicity. 4'-Modified nucleosides represent an important subclass of modified nucleosides for antiviral therapies. To prevent the occurrence of drug resistance, 4'-modified nucleosides should have 3'-OH, which should also be chemically unreactive for proviral DNA biosynthesis. The absence of 3'-OH may explain the occurrence of drug resistance for censavudine. The introduction of 4'-substituents improves enzymatic and acidic stability and makes the nucleosides more lipophilic, thus improving cell permeability and bioavailability. Steric hindrance between the 4'-substituent and 3'-OH changes the furanose conformation to the 3'-endo type, in which the oxygen lone pair on the furanose ring could not form an oxocarbonium ion for glycolysis. Currently, seven 4'-modified nucleoside drug candidates such as azvudine (also known as FNC), islatravir, censavudine, balapiravir, lumicitabine, AL-335, and 4-azidothymidine have progressed into clinical stages for treating viral infections. Of note, FNC was officially approved by NMPA in July 2021 for use in adult patients with high HIV-1 virus loads (nos. H20210035 and H20210036), providing an alternative therapeutic for patients with HIV-1. The long-term cellular retention of FNC suggests its potential as a long-lasting pre-exposure prophylaxis (PrEP) agent for preventing HIV-1 infection. Mechanistically, FNC not only inhibited HIV-1 reverse transcription and replication but also restored A3G expression in peripheral blood CD4+ T cells in HIV-1 patients receiving FNC. The 4'-azido group in azvudine stabilizes the 3'-C-endo (north) conformation by steric effects and the formation of an intramolecular hydrogen bond with the 3'-OH group, thus decreasing the nucleophilicity of 3'-OH. The north conformation may also enhance the phosphorylation efficiency of FNC by cellular kinases. Encouragingly, FNC, islatravir, and balapiravir show promise for the treatment of coronaviruses, of which FNC has advanced to phase 3 clinical trials in different countries to treat patients with COVID-19 (clinical trial numbers: NCT04668235 and NCT04425772). FNC cured the COVID-19 disease in almost all patients and showed better therapeutic efficacy than remdesivir. In this Account, we provide an overview of 4'-modified nucleoside analogs in clinical stages for antiviral therapies, highlighting the drug discovery strategies, structure-activity relationship studies, and preclinical/clinical studies and also give our perspectives on nucleoside-based antiviral drug discovery.

SARS-CoV-2-triggered mast cell rapid degranulation induces alveolar epithelial inflammation and lung injury.

SARS-CoV-2 infection-induced hyper-inflammation links to the acute lung injury and COVID-19 severity. Identifying the primary mediators that initiate the uncontrolled hypercytokinemia is essential for treatments. Mast cells (MCs) are strategically located at the mucosa and beneficially or detrimentally regulate immune inflammations. In this study, we showed that SARS-CoV-2-triggered MC degranulation initiated alveolar epithelial inflammation and lung injury. SARS-CoV-2 challenge induced MC degranulation in ACE-2 humanized mice and rhesus macaques, and a rapid MC degranulation could be recapitulated with Spike-RBD binding to ACE2 in cells; MC degranulation altered various signaling pathways in alveolar epithelial cells, particularly, the induction of pro-inflammatory factors and consequential disruption of tight junctions. Importantly, the administration of clinical MC stabilizers for blocking degranulation dampened SARS-CoV-2-induced production of pro-inflammatory factors and prevented lung injury. These findings uncover a novel mechanism for SARS-CoV-2 initiating lung inflammation, and suggest an off-label use of MC stabilizer as immunomodulators for COVID-19 treatments.

Azvudine is a thymus-homing anti-SARS-CoV-2 drug effective in treating COVID-19 patients.

Azvudine (FNC) is a nucleoside analog that inhibits HIV-1 RNA-dependent RNA polymerase (RdRp). Recently, we discovered FNC an agent against SARS-CoV-2, and have taken it into Phase III trial for COVID-19 patients. FNC monophosphate analog inhibited SARS-CoV-2 and HCoV-OC43 coronavirus with an EC50 between 1.2 and 4.3 µM, depending on viruses or cells, and selective index (SI) in 15-83 range. Oral administration of FNC in rats revealed a substantial thymus-homing feature, with FNC triphosphate (the active form) concentrated in the thymus and peripheral blood mononuclear cells (PBMC). Treating SARS-CoV-2 infected rhesus macaques with FNC (0.07 mg/kg, qd, orally) reduced viral load, recuperated the thymus, improved lymphocyte profiles, alleviated inflammation and organ damage, and lessened ground-glass opacities in chest X-ray. Single-cell sequencing suggested the promotion of thymus function by FNC. A randomized, single-arm clinical trial of FNC on compassionate use (n = 31) showed that oral FNC (5 mg, qd) cured all COVID-19 patients, with 100% viral ribonucleic acid negative conversion in 3.29 ± 2.22 days (range: 1-9 days) and 100% hospital discharge rate in 9.00 ± 4.93 days (range: 2-25 days). The side-effect of FNC is minor and transient dizziness and nausea in 16.12% (5/31) patients. Thus, FNC might cure COVID-19 through its anti-SARS-CoV-2 activity concentrated in the thymus, followed by promoted immunity.

A Randomized, Open-Label, Controlled Clinical Trial of Azvudine Tablets in the Treatment of Mild and Common COVID-19, a Pilot Study.

Coronavirus disease 2019 (COVID-19) has spread worldwide. To date, no specific drug for COVID-19 has been developed. Thus, this randomized, open-label, controlled clinical trial (ChiCTR2000029853) was performed in China. A total of 20 mild and common COVID-19 patients were enrolled and randomly assigned to receive azvudine and symptomatic treatment (FNC group), or standard antiviral and symptomatic treatment (control group). The mean times of the first nucleic acid negative conversion (NANC) of ten patients in the FNC group and ten patients in the control group are 2.60 (SD 0.97; range 1-4) d and 5.60 (SD 3.06; range 2-13) d, respectively (p = 0.008). The mean times of the first NANC of four newly diagnosed subjects in the FNC group and ten subjects in the control group are 2.50 (SD 1.00; range 2-4) d and 9.80 (SD 4.73; range 3-19) d, respectively (starting from the initial treatment) (p = 0.01). No adverse events occur in the FNC group, while three adverse events occur in the control group (p = 0.06). The preliminary results show that FNC treatment in the mild and common COVID-19 may shorten the NANC time versus standard antiviral treatment. Therefore, clinical trials of FNC treating COVID-19 with larger sample size are warranted.

Current and future therapeutical approaches for COVID-19.

We review the evolution of our clinical understanding of COVID-19, possible therapeutic targets, and prospects for COVID-19 management.