Artemisone demonstrates synergistic antiviral activity in combination with approved and experimental drugs active against human cytomegalovirus

We have recently shown that the artemisinin derivative artemisone, which was screened against malaria in human clinical studies, is a potent inhibitor of human cytomegalovirus (HCMV). Here we evaluated the antiviral effect of artemisone when employed in 2-drug combinations with approved and experimental anti-HCMV agents. Using the Chou-Talalay method, we found that in-vitro combination of artemisone with cidofovir, brincidofovir, or with the HCMV UL97 inhibitor maribavir resulted in antiviral synergism and the combination of artemisone with ganciclovir or with the viral terminase inhibitors letermovir and BDCRB resulted in moderate synergism. Importantly, the combination of artemisone with maribavir demonstrated synergistic antiviral activity ex-vivo, in a clinically-relevant multicellular model of human placental tissues maintained in organ culture. Our findings provide the basis for the use of artemisone in synergistically acting drug combinations, to enhance viral control and reduce antiviral drug toxicities. •The new artemisinin derivative artemisone demonstrated in-vitro synergism with approved and experimental anti-HCMV drugs.•The synergism of artemisone with the HCMV inhibitor maribavir was confirmed in ex-vivo infected human placental tissues.•The findings provide the basis for the use of artemisone in synergistically acting drug combinations against HCMV.