Development of Antiplasmodial Peptide-Drug Conjugates Using a Human Protein-Derived Cell-Penetrating Peptide with Selectivity for Infected Cells

Malaria continues to impose a global health burden. Drug-resistant parasites have emerged to each introduced small-molecule therapy, highlighting the need for novel treatment approaches for the future eradication of malaria. Herein, targeted drug delivery with peptide-drug conjugates (PDCs) was investigated as an alternative antimalarial therapy, inspired by the success of emerging antibody-drug conjugates utilized in cancer treatment. A synthetic peptide derived from an innate human defense molecule was conjugated to the antimalarial drug primaquine (PQ) to produce PDCs with low micromolar potency toward Plasmodium falciparum in vitro. A suite of PDCs with different design features was developed to identify optimal conjugation site and investigate linker length, hydrophilicity, and cleavability. Conjugation within a flexible spacer region of the peptide, with a cleavable linker to liberate the PQ cargo, was important to retain activity of the peptide and drug.