Assessment of Protein Binding of 5‑Hydroxythalidomide Bioactivated in Humanized Mice with Human <i>P450 3A</i>-Chromosome or Hepatocytes by Two-Dimensional Electrophoresis/Accelerator Mass Spectrometry

Bioactivation of 5-hydroxy-[<i>carbonyl</i>-¹⁴C]­thalidomide, a known metabolite of thalidomide, by human artificial or native cytochrome P450 3A enzymes, and nonspecific binding in livers of mice was assessed using two-dimensional electrophoresis combined with accelerator mass spectrometry. The apparent major target proteins were liver microsomal cytochrome <i>c</i> oxidase subunit 6B1 and ATP synthase subunit α in mice containing humanized <i>P450 3A</i> genes or transplanted humanized liver. Liver cytosolic retinal dehydrogenase 1 and glutathione transferase A1 were targets in humanized mice with P450 3A and hepatocytes, respectively. 5-Hydroxythalidomide is bioactivated by human P450 3A enzymes and trapped with proteins nonspecifically in humanized mice