Identification of active main metabolites of anti-infective inhibitors of the macrophage infectivity potentiator protein by liquid chromatography using mass detection

Due to increasing antibiotic resistance, the development of anti-infectives with new mechanisms of action is crucial. Virulence factors such as the “macrophage infectivity potentiator” (Mip) protein, which catalyzes the folding of proline-containing proteins by means of their cis–trans isomerase (PPIase) activity, have come into focus as a potential new target. Since the inhibition of Mip by small molecules has been shown to lead to reduced virulence and survival in vitro, especially of Gram-negative bacteria such as Burkholderia pseudomallei (Bp), Neisseria meningitidis (Nm), and Neisseria gonorrhoeae (Ng), or Coxiella burnetii (Cb), among many others, a library of Mip inhibitors was developed. As drug metabolism has a significant impact on the overall therapeutic outcome, this report describes the biotransformation of the most potent Mip inhibitors. Therefore, the anti-infectives were treated using human liver microsomes in vitro. Liquid chromatography with tandem mass spectrometry (LC/MS-MS) methods were applied to identify the metabolites and quantify the metabolic degradation of the hit compounds. Active metabolites, N-oxides, were found, leading to new opportunities for further drug development.