Exploring the Utility of Cell‐Penetrating Peptides as Vehicles for the Delivery of Distinct Antimalarial Drug Cargoes

Abstract

The devastating impact of malaria includes significant mortality and illness worldwide. Increasing resistance of the causative parasite, Plasmodium, to existing antimalarial drugs underscores a need for additional compounds with distinct modes of action in the therapeutic development pipeline. Here we showcase peptide‐drug conjugates (PDCs) as an attractive compound class, in which therapeutic or lead antimalarials are chemically conjugated to cell‐penetrating peptides. This approach aims to enhance selective uptake into Plasmodium‐infected red blood cells and impart additional cytotoxic actions on the intraerythrocytic parasite, thereby enabling targeted drug delivery and dual modes of action. We describe the development of PDCs featuring four compounds with antimalarial activity – primaquine, artesunate, tafenoquine and methotrexate – conjugated to three cell‐penetrating peptide scaffolds with varied antiplasmodial activity, including active and inactive analogs of platelet factor 4 derived internalization peptide (PDIP), and a cyclic polyarginine peptide. Development of this diverse set of PDCs featured distinct and adaptable conjugation strategies, to produce conjugates with in vitro antiplasmodial activities ranging from low nanomolar to low micromolar potencies according to the drug cargo and bioactivity of the partner peptide. Overall, this study establishes a strategic and methodological framework for the further development of dual mode of action peptide‐drug antimalarial therapeutics.

Cell-Penetrating Cyclic and Disulfide-Rich Peptides Are Privileged Molecular Scaffolds for Intracellular Targeting

“…We have developed PDCs that contain PDIP and the antimalarial drugs primaquine (PQ), tafenoquine and artesunate (ART). 71,72 We have also explored a range of linker options, including noncleavable hydrophobic linkers (alkane, DBCO), noncleavable linkers with PEG moieties, and cleavable linkers with disulfide or trioxolone spacers designed to liberate free drug cargo inside parasites within RBC. 71,72 We established that PDIP can be used as a vehicle for delivering antimalarial drugs, as the PDCs had potent in vitro activity against P. falciparum that was driven by the activity of the cargo molecule (e.g., nM IC 50 for ART-containing PDCs).…”

“…A cleavable linker was not required for conjugation to ART, which is a prodrug that is processed by esterases in the parasite cytosol to liberate the active drug dihydroartesunate. 72 Considering the selectivity of PDIP for membranes that contain negatively charged phospholipids, we were interested in determining whether it also acts against cancer cells. We treated a panel of cancer and noncancer cell lines and blood cells with first-generation PDIP analog cPF4PD, and observed selective low micromolar potency toward melanoma and leukemia cells.…”