RESUMEN
The guanosine analog AT-527 represents a promising candidate against Severe Acute Respiratory Syndrome coronavirus type 2 (SARS-CoV-2). AT-527 recently entered phase III clinical trials for the treatment of COVID-19. Once in cells, AT-527 is converted into its triphosphate form, AT-9010, that presumably targets the viral RNA-dependent RNA polymerase (RdRp, nsp12), for incorporation into viral RNA. Here we report a 2.98 Å cryo-EM structure of the SARS-CoV-2 nsp12-nsp7-nsp82-RNA complex, showing AT-9010 bound at three sites of nsp12. In the RdRp active-site, one AT-9010 is incorporated at the 3' end of the RNA product strand. Its modified ribose group (2'-fluoro, 2'-methyl) prevents correct alignment of the incoming NTP, in this case a second AT-9010, causing immediate termination of RNA synthesis. The third AT-9010 is bound to the N-terminal domain of nsp12 - known as the NiRAN. In contrast to native NTPs, AT-9010 is in a flipped orientation in the active-site, with its guanine base unexpectedly occupying a previously unnoticed cavity. AT-9010 outcompetes all native nucleotides for NiRAN binding, inhibiting its nucleotidyltransferase activity. The dual mechanism of action of AT-527 at both RdRp and NiRAN active sites represents a promising research avenue against COVID-19.
Asunto(s)
Antivirales/química , Antivirales/farmacología , Guanosina Monofosfato/análogos & derivados , Fosforamidas/química , Fosforamidas/farmacología , ARN Polimerasa Dependiente del ARN/antagonistas & inhibidores , SARS-CoV-2/enzimología , Proteínas Virales/antagonistas & inhibidores , Proteínas Virales/metabolismo , COVID-19/virología , Microscopía por Crioelectrón , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Guanosina Monofosfato/química , Guanosina Monofosfato/farmacología , Humanos , ARN Polimerasa Dependiente del ARN/química , ARN Polimerasa Dependiente del ARN/genética , ARN Polimerasa Dependiente del ARN/metabolismo , SARS-CoV-2/química , SARS-CoV-2/efectos de los fármacos , SARS-CoV-2/genética , Proteínas Virales/genéticaRESUMEN
Endoscopy is widely used as a clinical diagnosis and treatment method for certain hepatobiliary and pancreatic diseases. However, due to the distinctive epidemiological characteristics of severe acute respiratory syndrome coronavirus 2, the virus causing coronavirus disease-2019 (COVID-19), healthcare providers are exposed to the patient's respiratory and gastrointestinal fluids, rendering endoscopy a high risk for transmitting a nosocomial infection. This article introduces preventive measures for endoscopic treatment enacted in our medical center during COVID-19, including the adjustment of indications, the application of endoscope protective equipment, the design and application of endoscopic masks and splash-proof films, and novel recommendations for bedside endoscope pre-sterilization.