Defining the genetic basis of piperaquine resistance in P. falciparum to support malaria elimination

Expanded malaria interventions, reliant on effective artemisinin-based combination therapies (ACTs), have halved malaria mortality in the past decade. Yet malaria continues to kill over 500,000 children yearly. The situation could rapidly worsen if resistance of P. falciparum (Pf) to ACTs takes hold and spreads. This has begun with the emergence of resistance to artemisinin. Recently, the partner drug piperaquine (PPQ) has encountered resistance, leading to treatment failures in Cambodia, the epicenter of multidrug resistance. Resistance is also emerging in French Guiana. I propose to define the genetic basis of PPQ resistance. Using clinical isolates, I will implement genetic crosses between resistant and sensitive Pf parasites in chimeric FRG-NOD mice that are receptive to Pf infections. I will quantify PPQ susceptibility in the progeny using in vitro dose-response and survival assays. Linkage association studies with whole-genome sequenced progeny will localize candidate determinants, whose role will be ascertained using Cas9-based genome editing. In parallel, I will assess novel mutations in the pleiotropic drug transporter PfCRT that have recently been identified in a subset of PPQ-resistant Cambodian parasites. I hypothesize that resistance is multifactorial and involves altered hemoglobin digestion and availability of reactive heme as a PPQ ligand, along with altered drug transport. I will also define which partner drugs remain effective against PPQ-resistant parasites. Results of this high-risk, high-yield project will provide molecular markers to track PPQ resistance, offer insights into drug action, and inform strategies to combat multidrug-resistant malaria.