Targeting Plasmodium falciparum IspD in the Methyl‑d‑erythritol Phosphate\nPathway: Urea-Based Compounds with Nanomolar Potency on Target and\nLow-Micromolar Whole-Cell Activity

The methyl-d-erythritol phosphate (MEP) pathway has emerged\nas an interesting target in the fight against antimicrobial resistance.\nThe pathway is essential in many human pathogens, including Plasmodium falciparum (<i>Pf</i>), but\nis absent in human cells. In the present study, we report on the discovery\nof a new chemical class targeting IspD, the third enzyme in the pathway.\nExploration of the structure–activity relationship yielded\ninhibitors with potency in the low-nanomolar range. Moreover, we investigated\nthe whole-cell activity, mode of inhibition, metabolic, and plasma\nstability of this compound class, and conducted <i>in vivo</i> pharmacokinetic profiling on selected compounds. Lastly, we disclosed\na new mass spectrometry (MS)-based enzymatic assay for direct IspD\nactivity determination, circumventing the need for auxiliary enzymes.\nIn summary, we have identified a readily synthesizable compound class,\ndemonstrating excellent activity and a promising profile, positioning\nit as a valuable tool compound for advancing research on IspD.