Activity and Predicted Nephrotoxicity of Synthetic Antibiotics Based on Polymyxin B.

Alejandra Gallardo-Godoy,Alysha G Elliott,Matthew A Cooper,Wanida Phetsang,Mark A T Blaskovich,Ruby Pelingon,Johnny X Huang,Bernd Becker,Lawrence H Lash,Craig Muldoon,Soumya Ramu,Mark S Butler,Angela M Kavanagh

doi:10.1021/acs.jmedchem.5b01593

Alejandra Gallardo-Godoy, Alysha G Elliott + Show 11 more

Open Access

https://doi.org/10.1021/acs.jmedchem.5b01593

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Abstract

The polymyxin lipodecapeptides colistin and polymyxin B have become last resort therapies for infections caused by highly drug-resistant Gram-negative bacteria. Unfortunately, their utility is compromised by significant nephrotoxicity and polymyxin-resistant bacterial strains. We have conducted a systematic activity–toxicity investigation by varying eight of the nine polymyxin amino acid free side chains, preparing over 30 analogues using a novel solid-phase synthetic route. Compounds were tested against a panel of Gram-negative bacteria and counter-screened for in vitro cell toxicity. Promising compounds underwent additional testing against primary kidney cells isolated from human kidneys to better predict their nephrotoxic potential. Many of the new compounds possessed equal or better antimicrobial potency compared to polymyxin B, and some were less toxic than polymyxin B and colistin against mammalian HepG2 cells and human primary kidney cells. These initial structure–activity and structure–toxicity studies set the stage for further improvements to the polymyxin class of antibiotics.

Highlights

Bacterial sepsis kills millions of people every year
The synthetic routes toward the final compounds in this library are summarized in Schemes 1, 2, and S2 (Supporting Information)
The first solid-phase total synthesis of polymyxin B1 was developed in 1999 by Sharma[62] using Fmoc-Thr(tBu)-SASRIN resin, with the linear peptide cleaved from the resin and cyclized in solution

Summary

■ INTRODUCTION

Patients hospitalized for septicemia or sepsis are more than eight times as likely to die during their hospitalization compared to those hospitalized for other diagnoses,[1] with over 200,000 deaths in 2008.2 Over one-third of patients with sepsis treated in an intensive care unit die in the hospital.[3]. E. coli IFO12734, and P. aeruginosa IFO3080 from the Institute for Fermentation, Osaka, Japan.[46] b12 is compound 5 in O’Dowd et al.; MIC E. coli = 0.03, P. aeruginosa = 4, S. aureus = >16 μg/mL.[47] c13 is compound 5 in Leese et al.; MIC90 P. aeruginosa (100 strains) = 2, A. baumannii (81 strains) = 4, E. coli (80 strains) = 2, K. pneumoniae (81 strains) = 4 μg/mL.[54] d15 is compound 18 in Leese et al.; MIC E. coli = 2.5, P. aeruginosa ATCC 27853 = 2.5 μg/mL; MIC values were determined by serial 2-fold broth dilution method.[53] using primary kidney cells freshly isolated from human kidneys (see Table 4) This assay, measuring LDH and GGT release, has been reported to be a better in vitro model for predicting in vivo nephrotoxicity.[63−65] We assessed cytotoxicity against immortalized HEK293 cells. The results support our previous assessment of in vitro predictors of nephrotoxicity, in that there is little correlation between general cytotoxicity measurements and the human kidney results.[63,64]

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES