Fluorovinylsulfones and -Sulfonates as Potent Covalent Reversible Inhibitors of the Trypanosomal Cysteine Protease Rhodesain: Structure-Activity Relationship, Inhibition Mechanism, Metabolism, and In Vivo Studies

J Med Chem. 2021 Aug 26;64(16):12322-12358. doi: 10.1021/acs.jmedchem.1c01002. Epub 2021 Aug 11.

Abstract

Rhodesain is a major cysteine protease of Trypanosoma brucei rhodesiense, a pathogen causing Human African Trypanosomiasis, and a validated drug target. Recently, we reported the development of α-halovinylsulfones as a new class of covalent reversible cysteine protease inhibitors. Here, α-fluorovinylsulfones/-sulfonates were optimized for rhodesain based on molecular modeling approaches. 2d, the most potent and selective inhibitor in the series, shows a single-digit nanomolar affinity and high selectivity toward mammalian cathepsins B and L. Enzymatic dilution assays and MS experiments indicate that 2d is a slow-tight binder (Ki = 3 nM). Furthermore, the nonfluorinated 2d-(H) shows favorable metabolism and biodistribution by accumulation in mice brain tissue after intraperitoneal and oral administration. The highest antitrypanosomal activity was observed for inhibitors with an N-terminal 2,3-dihydrobenzo[b][1,4]dioxine group and a 4-Me-Phe residue in P2 (2e/4e) with nanomolar EC50 values (0.14/0.80 μM). The different mechanisms of reversible and irreversible inhibitors were explained using QM/MM calculations and MD simulations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cysteine Endopeptidases / chemistry
  • Cysteine Endopeptidases / metabolism*
  • Cysteine Proteinase Inhibitors / chemical synthesis
  • Cysteine Proteinase Inhibitors / metabolism
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Cysteine Proteinase Inhibitors / toxicity
  • Enzyme Assays
  • Female
  • HeLa Cells
  • Humans
  • Kinetics
  • Male
  • Mice
  • Molecular Docking Simulation
  • Molecular Structure
  • Parasitic Sensitivity Tests
  • Protein Binding
  • Structure-Activity Relationship
  • Sulfones / chemical synthesis
  • Sulfones / metabolism
  • Sulfones / pharmacology*
  • Sulfones / toxicity
  • Sulfonic Acids / chemical synthesis
  • Sulfonic Acids / metabolism
  • Sulfonic Acids / pharmacology*
  • Sulfonic Acids / toxicity
  • Trypanocidal Agents / chemical synthesis
  • Trypanocidal Agents / metabolism
  • Trypanocidal Agents / pharmacology*
  • Trypanocidal Agents / toxicity
  • Trypanosoma brucei brucei / drug effects
  • Vinyl Compounds / chemical synthesis
  • Vinyl Compounds / metabolism
  • Vinyl Compounds / pharmacology*
  • Vinyl Compounds / toxicity

Substances

  • Cysteine Proteinase Inhibitors
  • Sulfones
  • Sulfonic Acids
  • Trypanocidal Agents
  • Vinyl Compounds
  • Cysteine Endopeptidases
  • rhodesain