Assessment of JMN3-003 stability in human plasma in comparison with unstable Procaine and stable Procainamide Table 1 . Active (EC 50 ) and toxic (CC 50 , determined on Vero-Slam cells) concentrations of JMN3-003 against a selection of clinically relevant para-and orthomyxovirus family members in comparison with active concentrations of AS-136A, a previously characterized, MeV-specific inhibitor of the viral RdRp complex [20, 36] . [23] corroborated these results, since JMN3-003 integrity was virtually unaffected after a 120-minute incubation period ( figure 3B ). Taken together, these findings suggest desirable metabolic stability for the JMN3-003 scaffold, recommending it for further mechanistic characterization. The data are corroborated by the good metabolic stability reported for the structurally similar compound RDEA-806 (figure S2), a non-nucleoside inhibitor of HIV reverse transcriptase and clinical precedent [24] , which shares the 2-thio-connector of JMN3-003 but lacks MeV inhibitory activity in our assays (data not shown).