Resistance to Some But Not Other Dimeric Lindenane Sesquiterpenoid Esters Is Mediated by Mutations in a <i>Plasmodium falciparum</i> Esterase

Abstract

Unique lindenane sesquiterpenoid dimers from <i>Chloranthecae</i> spp. were recently identified with promising <i>in vitro</i> antiplasmodial activity and potentially novel mechanisms of action. To gain mechanistic insights to this new class of natural products, <i>in vitro</i> selection of <i>Plasmodium falciparum</i> resistance to the most active antiplasmodial compound, chlorajaponilide C, was explored. In all selected resistant clones, the half-maximal effective concentration (EC₅₀) of chlorajaponilide C increased >250-fold, and whole genome sequencing revealed mutations in the recently discovered <i>P. falciparum</i> prodrug activation and resistance esterase (PfPARE). Chlorajaponilide C was highly potent (mean EC₅₀ = 1.6 nM, <i>n</i> = 34) against fresh Ugandan <i>P. falciparum</i> isolates. The analysis of the structure-resistance relationships revealed that <i>in vitro</i> potency of a subset of lindenane sesquiterpenoid dimers was not mediated by PfPARE mutations. Thus, chlorajaponilide C, but not some related compounds, required parasite esterase activity for <i>in vitro</i> potency, and those compounds serve as the foundation for development of potent and selective antimalarials.