Remdesivir Metabolite GS-441524 Effectively Inhibits SARS-CoV-2 Infection in Mouse Models.

The outbreak of coronavirus disease 2019 (COVID-19) has resulted in a global pandemic due to the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). At the time of this manuscript's publication, remdesivir is the only COVID-19 treatment approved by the United States Food and Drug Administration. However, its effectiveness is still under question due to the results of the large Solidarity Trial conducted by the World Health Organization. Herein, we report that the parent nucleoside of remdesivir, GS-441524, potently inhibits the replication of SARS-CoV-2 in Vero E6 and other cell lines. Challenge studies in both an AAV-hACE2 mouse model of SARS-CoV-2 and in mice infected with murine hepatitis virus, a closely related coronavirus, showed that GS-441524 was highly efficacious in reducing the viral titers in CoV-infected organs without notable toxicity. Our results support that GS-441524 is a promising and inexpensive drug candidate for treating of COVID-19 and other CoV diseases.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and nucleotide analog GS-441524 conjugates with potent in vivo efficacy against coronaviruses.

Coronaviruses (CoVs) infect a broad range of hosts, including humans and various animals, with a tendency to cross the species barrier, causing severe harm to human society and fostering the need for effective anti-coronaviral drugs. GS-441524 is a broad-spectrum antiviral nucleoside with potent anti-CoVs activities. However, its application is limited by poor oral bioavailability. Herein, we designed and synthesized several conjugates via covalently binding NSAIDs to 5'-OH of GS-441524 through ester bonds. The ibuprofen conjugate, ATV041, exhibited potent in vitro anti-coronaviral efficacy against four zoonotic coronaviruses in the alpha- and beta-genera. Oral-dosed ATV041 resulted in favorable bioavailability and rapid tissue distribution of GS-441524 and ibuprofen. In MHV-A59 infected mice, ATV041 dose-dependently decreased viral RNA replication and significantly reduced the proinflammatory cytokines in the liver and the lung at 3 dpi. As a result, the MHV-A59-induced lung and liver inflammatory injury was significantly alleviated. Taken together, this work provides a novel drug conjugate strategy to improve oral PK and offers a potent anti-coronaviral lead compound for further studies.

Aloe polymeric acemannan inhibits the cytokine storm in mouse pneumonia models by modulating macrophage metabolism.

The cytokine storm is highly associated with inflammatory-type disease severity and patients' survival. Plant polysaccharides, the main natural phytomedicine source, have a great potential to be an effective drug to treat cytokine storm. Herein we found that a polymeric acemannan (ABPA1) isolated from Aloe Vera Barbadensis extract C (AVBEC) exerted prominent inhibitory effects on inflammation-induced cytokine storm. The results displayed that ABPA1 effectively suppressed LPS-induced proinflammatory cytokines release in vitro. Moreover, ABPA1 treatment alleviated the cytokine storm and tissue damage in LPS- and IAV-induced mouse pneumonia models, and altered the phenotypic balance of macrophages in lung tissues. Functionally, ABPA1 enhanced macrophage M2 polarization and phagocytosis in RAW264.7 cells and inhibited LPS-induced M1 polarization. Mechanistically, ABPA1 enhanced mitochondrial metabolism and OXPHOS through activated PI3K/Akt/GSK-3ß signalling pathway. Overall, our findings suggest that ABPA1 may modulate macrophage activation and mitochondrial metabolism by targeting PI3K/Akt/GSK-3ß signalling pathway, thereby alleviating cytokine storm and inflammation.

Establishment of a recombinase polymerase amplification (RPA) fluorescence assay for the detection of swine acute diarrhea syndrome coronavirus (SADS-CoV).

BACKGROUND: Swine acute diarrhea syndrome coronavirus (SADS-CoV) causes acute vomiting and diarrhea in piglets, leading to significant financial losses for the pig industry. Recombinase polymerase amplification (RPA) is a rapid nucleic acid amplification technology used under constant temperature conditions. The study established a real-time reverse transcription (RT)-RPA assay for early diagnosis of SADS-CoV.  RESULTS: The detection limit of the real-time RT-RPA was 74 copies/µL of SADS-CoV genomic standard recombinant plasmid in 95% of cases. The assay was performed in less than 30 min and no cross-reactions were observed with eight other common viruses that affect swine, including classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), pseudo rabies virus (PRV), swine influenza virus (SIV), seneca valley virus (SVA), transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV). The coefficient of variation (C.V.) values of the two standards dilutions and three positive clinical sample ranged from 2.95% to 4.71%. A total of 72 clinical fecal samples from swine with diarrheal symptoms were analyzed with the developed RT-RPA and quantitative RT-PCR. There was 98.61% agreement between the RT-RPA and the quantitative real-time PCR results. CONCLUSIONS: These results indicated that the developed RT-RPA assay had good specificity, sensitivity, stability and repeatability. The study successfully established a broadly reactive RT-RPA assay for SADS-CoV detection.

The adenosine analog prodrug ATV006 is orally bioavailable and has preclinical efficacy against parental SARS-CoV-2 and variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus driving the ongoing coronavirus disease 2019 (COVID-19) pandemic, continues to rapidly evolve. Because of the limited efficacy of vaccination in prevention of SARS-CoV-2 transmission and continuous emergence of variants of concern (VOCs), orally bioavailable and broadly efficacious antiviral drugs are urgently needed. Previously, we showed that the parent nucleoside of remdesivir, GS-441524, has potent anti-SARS-CoV-2 activity. Here, we report that esterification of the 5'-hydroxyl moieties of GS-441524 markedly improved antiviral potency. This 5'-hydroxyl-isobutyryl prodrug, ATV006, demonstrated excellent oral bioavailability in rats and cynomolgus monkeys and exhibited potent antiviral efficacy against different SARS-CoV-2 VOCs in vitro and in three mouse models. Oral administration of ATV006 reduced viral loads and alleviated lung damage when administered prophylactically and therapeutically to K18-hACE2 mice challenged with the Delta variant of SARS-CoV-2. These data indicate that ATV006 represents a promising oral antiviral drug candidate for SARS-CoV-2.