Discovery of a highly potent novel rifampicin analog by preparing a hybrid of the precursors of the antibiotic drugs rifampicin and clofazimine

Sci Rep. 2021 Jan 13;11(1):1029. doi: 10.1038/s41598-020-80439-2.

Abstract

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (Mtb). The present work reports the design and synthesis of a hybrid of the precursors of rifampicin and clofazimine, which led to the discovery of a novel Rifaphenazine (RPZ) molecule with potent anti-TB activity. In addition, the efficacy of RPZ was evaluated in-vitro using the reference strain Mtb H37Rv. Herein, 2,3 diamino phenazine, a precursor of an anti-TB drug clofazimine, was tethered to the rifampicin core. This 2,3 diamino phenazine did not have an inherent anti-TB activity even at a concentration of up to 2 µg/mL, while rifampicin did not exhibit any activity against Mtb at a concentration of 0.1 µg/mL. However, the synthesized novel Rifaphenzine (RPZ) inhibited 78% of the Mtb colonies at a drug concentration of 0.1 µg/mL, while 93% of the bacterial colonies were killed at 0.5 µg/mL of the drug. Furthermore, the Minimum Inhibitory Concentration (MIC) value for RPZ was 1 µg/mL. Time-kill studies revealed that all bacterial colonies were killed within a period of 24 h. The synthesized novel molecule was characterized using high-resolution mass spectroscopy and NMR spectroscopy. Cytotoxicity studies (IC50) were performed on human monocytic cell line THP-1, and the determined IC50 value was 96 µg/mL, which is non-cytotoxic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antitubercular Agents / chemical synthesis*
  • Antitubercular Agents / chemistry
  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / chemistry
  • Clofazimine / analogs & derivatives*
  • Clofazimine / chemical synthesis
  • Clofazimine / chemistry
  • DNA-Directed RNA Polymerases / antagonists & inhibitors
  • DNA-Directed RNA Polymerases / chemistry
  • Drug Design
  • Drug Discovery
  • Humans
  • Magnetic Resonance Spectroscopy
  • Mass Spectrometry
  • Microbial Sensitivity Tests
  • Models, Molecular
  • Molecular Docking Simulation
  • Molecular Structure
  • Monocytes / drug effects
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / enzymology
  • Rifampin / analogs & derivatives*
  • Rifampin / chemical synthesis
  • Rifampin / chemistry
  • THP-1 Cells

Substances

  • Antitubercular Agents
  • Bacterial Proteins
  • Clofazimine
  • DNA-Directed RNA Polymerases
  • Rifampin