The Pathogen Box

Catalysing neglected disease drug discovery

Screening of the Pathogen Box for inhibitors with dual efficacy against Giardia lamblia and Cryptosporidium parvum

06 August 2018

Kelly M. Hennessey, Ilse C. Rogiers, Han-Wei Shih, Matthew A. Hulverson, Ryan Choi, Molly C. McCloskey, Grant R. Whitman, Lynn K. Barrett, Ethan A. Merritt, Alexander R. Paredez , Kayode K. Ojo

PLOS Neglected Tropical Diseases

DOI: 10.1371/journal.pntd.0006673

There is need for a more efficient cell-based assay amenable to high-throughput drug screening against Giardia lamblia. Here, we report the development of a screening method utilizing Glamblia engineered to express red-shifted firefly luciferase. Parasite growth and replication were quantified using D-luciferin as a substrate in a bioluminescent read-out platform. This assay was validated for reproducibility and reliability against the Medicines for Malaria Venture (MMV) Pathogen Box compounds. For Glamblia, forty-three compounds showed ≥ 75% inhibition of parasite growth in the initial screen (16 μM), with fifteen showing ≥ 95% inhibition.

The Pathogen Box was also screened against Nanoluciferase expressing (Nluc) Cparvum, yielding 85 compounds with ≥ 75% parasite growth inhibition at 10 μM, with six showing ≥ 95% inhibition. A representative set of seven compounds with activity against both parasites were further analyzed to determine the effective concentration that causes 50% growth inhibition (EC50) and cytotoxicity against mammalian HepG2 cells. Four of the seven compounds were previously known to be effective in treating either Giardia or Cryptosporidium. The remaining three shared no obvious chemical similarity with any previously characterized anti-parasite diarrheal drugs and offer new medicinal chemistry opportunities for therapeutic development. These results suggest that the bioluminescent assays are suitable for large-scale screening of chemical libraries against both Cparvum and Glamblia.

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