Abstract
Abstract
Background
Leishmaniasis remains a neglected tropical disease with limited therapeutic options and a continued need for new and effective treatments. High-throughput phenotypic screening provides an approach for identifying chemically diverse compounds with antileishmanial activity that can serve as a starting point for drug development. This study further characterized compounds identified through a previous high-throughput phenotypic screen to prioritize promising antileishmanial chemical scaffolds and evaluate their potential for continued drug development.
Methods
Compounds belonging to two enriched scaffolds, 1,4-diaryl-pyrazolo-pyridinone (1,4-DAPP) and pyrazolo-[5,1-c][1,2,4]triazine (PTZ), along with structurally diverse singleton compounds, were evaluated for antileishmanial activity across
Leishmania
parasite life stages by determining half-maximal inhibitory concentrations (IC
50
). Host-cell cytotoxicity was evaluated against THP-1 macrophages by determining half-maximal cytotoxic concentrations (CC
50
). The IC
50
and CC
50
values were determined by nonlinear regression analysis. Selected lead compounds underwent preliminary
in vitro
absorption, distribution, metabolism, and excretion (ADME) profiling. Synthesized analogs of both scaffolds were evaluated to investigate structure-activity relationships and opportunities for chemical optimization.
Results
1,4-DAPP #9279817 and PTZ #9234527 were prioritized as lead compounds based on their combined antileishmanial activity and host-cell selectivity, exhibiting intracellular amastigote IC
50
values of 3.50 and 3.12 µM and selectivity indices (SI) of 14.29 and 16.03, respectively. Singleton compounds exhibited variable parasite stage-specific activity, with host-cell cytotoxicity limiting the selectivity of several candidates. Both lead scaffolds retained activity across multiple
Leishmania
species, although compound susceptibility varied among species. Preliminary ADME profiling revealed distinct properties of the two leads, highlighting strengths and limitations for further optimization. Structural modifications of both scaffolds generated analogs with improved intracellular antileishmanial activity and selectivity.
Conclusions
The 1,4-DAPP and PTZ scaffolds represent promising candidates for continued antileishmanial development. These findings support continued optimization of both scaffolds while emphasizing the importance of evaluating antileishmanial activity in disease-relevant parasite models.