Repositioning Antitubercular 6-Nitro-2,3-dihydroimidazo[2,1-b][1,3]oxazoles for Neglected Tropical Diseases: Structure-Activity Studies on a Preclinical Candidate for Visceral Leishmaniasis

J Med Chem. 2016 Mar 24;59(6):2530-50. doi: 10.1021/acs.jmedchem.5b01699. Epub 2016 Mar 8.


6-Nitro-2,3-dihydroimidazo[2,1-b][1,3]oxazole derivatives were initially studied for tuberculosis within a backup program for the clinical trial agent pretomanid (PA-824). Phenotypic screening of representative examples against kinetoplastid diseases unexpectedly led to the identification of DNDI-VL-2098 as a potential first-in-class drug candidate for visceral leishmaniasis (VL). Additional work was then conducted to delineate its essential structural features, aiming to improve solubility and safety without compromising activity against VL. While the 4-nitroimidazole portion was specifically required, several modifications to the aryloxy side chain were well-tolerated e.g., exchange of the linking oxygen for nitrogen (or piperazine), biaryl extension, and replacement of phenyl rings by pyridine. Several less lipophilic analogues displayed improved aqueous solubility, particularly at low pH, although stability toward liver microsomes was highly variable. Upon evaluation in a mouse model of acute Leishmania donovani infection, one phenylpyridine derivative (37) stood out, providing efficacy surpassing that of the original preclinical lead.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antiprotozoal Agents / chemical synthesis*
  • Antiprotozoal Agents / pharmacokinetics
  • Antiprotozoal Agents / pharmacology*
  • Antitubercular Agents / chemical synthesis*
  • Antitubercular Agents / pharmacokinetics
  • Antitubercular Agents / pharmacology*
  • Cricetinae
  • Drug Repositioning
  • Female
  • High-Throughput Screening Assays
  • Hydrogen-Ion Concentration
  • Leishmania infantum / drug effects
  • Leishmaniasis, Visceral / drug therapy*
  • Mesocricetus
  • Mice
  • Mice, Inbred BALB C
  • Microsomes, Liver / metabolism
  • Models, Molecular
  • Solubility
  • Structure-Activity Relationship


  • Antiprotozoal Agents
  • Antitubercular Agents