Evaluation of the Inhibition Potency of Nirmatrelvir against Main Protease Mutants of SARS-CoV-2 Variants.

SARS-CoV-2 continues to pose a threat to public health. Main protease (Mpro) is one of the most lucrative drug targets for developing specific antivirals against SARS-CoV-2 infection. By targeting Mpro, peptidomimetic nirmatrelvir is able to inhibit viral replication of SARS-CoV-2 and reduce the risk for progression to severe COVID-19. However, multiple mutations in the gene encoding Mpro of emerging SARS-CoV-2 variants raise a concern of drug resistance. In the present study, we expressed 16 previously reported SARS-CoV-2 Mpro mutants (G15S, T25I, T45I, S46F, S46P, D48N, M49I, L50F, L89F, K90R, P132H, N142S, V186F, R188K, T190I, and A191V). We evaluated the inhibition potency of nirmatrelvir against these Mpro mutants and solved the crystal structures of representative Mpro mutants of SARS-CoV-2 bound to nirmatrelvir. Enzymatic inhibition assays revealed that these Mpro variants remain susceptible to nirmatrelvir as the wildtype. Detailed analysis and structural comparison provided the inhibition mechanism of Mpro mutants by nirmatrelvir. These results informed the ongoing genomic surveillance of drug resistance of emerging SARS-CoV-2 variants to nirmatrelvir and facilitate the development of next-generation anticoronavirus drugs.

Structural basis of main proteases of HCoV-229E bound to inhibitor PF-07304814 and PF-07321332

PF-07321332 and PF-07304814, inhibitors against SARS-CoV-2 developed by Pfizer, exhibit broad-spectrum inhibitory activity against the main protease (Mpro) from various coronaviruses. Structures of PF-07321332 or PF-07304814 in complex with Mpros of various coronaviruses reveal their inhibitory mechanisms against different Mpros. However, the structural information on the lower pathogenic coronavirus Mpro with PF-07321332 or PF-07304814 is currently scarce, which hinders our comprehensive understanding of the inhibitory mechanisms of these two inhibitors. Meanwhile, given that some immunocompromised individuals are still affected by low pathogenic coronaviruses, we determined the structures of lower pathogenic coronavirus HCoV-229E Mpro with PF-07321332 and PF-07304814, respectively, and analyzed and defined in detail the structural basis for the inhibition of HCoV-229E Mpro by both inhibitors. Further, we compared the crystal structures of multiple coronavirus Mpro complexes with PF-07321332 or PF-07304814 to illustrate the differences in the interaction of Mpros, and found that the inhibition mechanism of lower pathogenic coronavirus Mpro was more similar to that of moderately pathogenic coronaviruses. Our structural studies provide new insights into drug development for low pathogenic coronavirus Mpro, and provide theoretical basis for further optimization of both inhibitors to contain potential future coronaviruses.

Structural basis of main proteases of HCoV-229E bound to inhibitor PF-07304814 and PF-07321332.

PF-07321332 and PF-07304814, inhibitors against SARS-CoV-2 developed by Pfizer, exhibit broad-spectrum inhibitory activity against the main protease (Mpro) from various coronaviruses. Structures of PF-07321332 or PF-07304814 in complex with Mpros of various coronaviruses reveal their inhibitory mechanisms against different Mpros. However, the structural information on the lower pathogenic coronavirus Mpro with PF-07321332 or PF-07304814 is currently scarce, which hinders our comprehensive understanding of the inhibitory mechanisms of these two inhibitors. Meanwhile, given that some immunocompromised individuals are still affected by low pathogenic coronaviruses, we determined the structures of lower pathogenic coronavirus HCoV-229E Mpro with PF-07321332 and PF-07304814, respectively, and analyzed and defined in detail the structural basis for the inhibition of HCoV-229E Mpro by both inhibitors. Further, we compared the crystal structures of multiple coronavirus Mpro complexes with PF-07321332 or PF-07304814 to illustrate the differences in the interaction of Mpros, and found that the inhibition mechanism of lower pathogenic coronavirus Mpro was more similar to that of moderately pathogenic coronaviruses. Our structural studies provide new insights into drug development for low pathogenic coronavirus Mpro, and provide theoretical basis for further optimization of both inhibitors to contain potential future coronaviruses.

Fatigue during Long-Haul Flights of Different Crew Compositions under Exemption from Layover and Flight Time during COVID-19.

Pilot fatigue and alertness are critical for civil aviation safety. Intercontinental pilots are more prone to fatigue and sleepiness due to jet lag, prolonged workdays, and disrupted rhythms. The Civil Aviation Administration of China excused enlarged flight crews from mandatory layovers and reimposed flight duration restrictions during COVID-19. This study investigates the sleep quality and attentional performance of pilots on intercontinental flights. The fifteen pilots who performed intercontinental flights in different crew compositions wore a body movement recorder, which has been proven to accurately estimate sleep duration and sleep efficiency. The crew's attentional performance and self-report were monitored at specified flight phases. In conclusion, the larger crews slept longer and more efficiently on board, particularly pilots in charge of takeoff and landing responsibilities. Crews on four-pilot layover flights were more alert before the takeoff of the inbound flights than exempt flights, but there was no significant difference towards the end of the mission. The new long-haul flight organization did not result in fatigue or decreased attention in the pilots. This study expands on the research by validating a novel intercontinental flight operation model under the COVID-19 scenario and highlighting critical spots for future fatigue management in various crew compositions.