Discovery of Lipophilic Bisphosphonates That Target Bacterial Cell Wall and Quinone Biosynthesis

We report that alkyl-subsituted bisphosphonates have activity against Bacillus anthracis Sterne (0.40 µg/mL), Mycobacterium smegmatis (1.4 µg/mL), Bacillus subtilis (1.0 µg/mL) and Staphylococcus aureus (13 µg/mL). In many cases, there is no effect of serum binding, as well as low activity against a human embryonic kidney cell line. Targeting of isoprenoid biosynthesis is involved with74 having IC50 values of ~100 nM against heptaprenyl diphosphate synthase and 200 nM against a farnesyl diphosphate synthase. Bacillus subtilis growth inhibition was rescued by addition of farnesyl diphosphate, menaquinone-4 (MK-4) or undecaprenyl diphosphate (UP) and the combination of MK-4 plus UP resulted in a 25x increase in ED50, indicating targeting of both quinone and cell wall biosynthesis. Clostridioides difficile was inhibited by 74 and since this organism does not synthesize quinones, cell wall biosynthesis is the likely target. We also solved three X-ray structures of inhibitors bound to octaprenyl diphosphate an...