Menoctone Resistance in Malaria Parasites Is Conferred by M133I Mutations in Cytochrome b That Are Transmissible through Mosquitoes.

ABSTRACT

Malaria-related mortality has slowly decreased over the past decade; however, eradication of malaria requires the development of new antimalarial chemotherapies that target liver stages of the parasite and combat the emergence of drug resistance. The diminishing arsenal of anti-liver-stage compounds sparked our interest in reviving the old and previously abandoned compound menoctone. In support of these studies, we developed a new convergent synthesis method that was facile, required fewer steps, produced better yields, and utilized less expensive reagents than the previously published method. Menoctone proved to be highly potent against liver stages of Plasmodium berghei (50 percent inhibitory concentration [IC50] = 0.41 nM) and erythrocytic stages of Plasmodium falciparum (113 nM). We selected for resistance to menoctone and found M133I mutations in cytochrome b of both P. falciparum and P. berghei The same mutation has been observed previously in atovaquone resistance, and we confirmed cross-resistance between menoctone and atovaquone in vitro (for P. falciparum) and in vivo (for P. berghei). Finally, we assessed the transmission potential of menoctone-resistant P. berghei and found that the M133I mutant parasites were readily transmitted from mouse to mosquitoes and back to mice. In each step, the M133I mutation in cytochrome b, inducing menoctone resistance, was confirmed. In summary, this study is the first to show the mechanism of resistance to menoctone and that menoctone and atovaquone resistance is transmissible through mosquitoes.