Design and Synthesis of High Affinity Inhibitors of Plasmodium falciparum and Plasmodium vivax N-Myristoyltransferases Directed by Ligand Efficiency Dependent Lipophilicity (LELP)

Mark D Rackham,Anthony A Holder,James A Brannigan,Stephan Meister,Kaveri Rangachari,Edward W Tate,Anthony J Wilkinson,Robin J Leatherbarrow

doi:10.1021/jm500066b

Abstract

N-Myristoyltransferase (NMT) is an essential eukaryotic enzyme and an attractive drug target in parasitic infections such as malaria. We have previously reported that 2-(3-(piperidin-4-yloxy)benzo[b]thiophen-2-yl)-5-((1,3,5-trimethyl-1H-pyrazol-4-yl)methyl)-1,3,4-oxadiazole (34c) is a high affinity inhibitor of both Plasmodium falciparum and P. vivax NMT and displays activity in vivo against a rodent malaria model. Here we describe the discovery of 34c through optimization of a previously described series. Development, guided by targeting a ligand efficiency dependent lipophilicity (LELP) score of less than 10, yielded a 100-fold increase in enzyme affinity and a 100-fold drop in lipophilicity with the addition of only two heavy atoms. 34c was found to be equipotent on chloroquine-sensitive and -resistant cell lines and on both blood and liver stage forms of the parasite. These data further validate NMT as an exciting drug target in malaria and support 34c as an attractive tool for further optimization.

Highlights

Malaria is an infectious disease caused by parasites of the genusPlasmodium and is a world health crisis of paramount urgency.Malaria was responsible for over 200 million cases and 1 million deaths in 2010 alone,[1] primarily affecting developing countries and children under the age of 5.2 five species of Plasmodium parasite are known to infect humans,[2,3] two species are responsible for the majority of morbidity and mortality: Plasmodium falciparum (Pf) and Plasmodium vivax (Pv)
Further development focused on removal of this high-risk functionality combined with a 100-fold improvement in enzyme affinity, reduced lipophilicity, and controlled molecular weight
Little is currently known of the potential for toxicity resulting from mammalian NMT inhibition, and previous data have shown that a potent Homo sapiens (Hs)NMT inhibitor is not toxic to mice at high doses.[22]

Summary

■ INTRODUCTION

Malaria was responsible for over 200 million cases and 1 million deaths in 2010 alone,[1] primarily affecting developing countries and children under the age of 5.2 five species of Plasmodium parasite are known to infect humans,[2,3] two species are responsible for the majority of morbidity and mortality: Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) These species are the focus of the work described in this paper. Using an integrated chemical biology approach, we identified the NMT substrate proteins in the blood stage of the parasite and demonstrated with small molecule tools that on-target inhibition of myristoylation disrupts the function of multiple specific downstream pathways, resulting in rapid cell death.[20] we describe the development of a previously described series of benzo[b]thiophene inhibitors into 34c, a potent and selective parasite NMT inhibitor instrumental to the validation of this drug target. We report further investigations into the utility of NMT inhibitors in drug-resistant cell lines and liver stage parasites

■ RESULTS AND DISCUSSION

■ CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES