Detection and characterization of olmutinib reactive metabolites by LC-MS/MS: Elucidation of bioactivation pathways

Area of Science:

• Pharmacology and Toxicology
• Medicinal Chemistry
• Drug Metabolism

Background:

• Olmutinib (Olita™) is a third-generation EGFR tyrosine kinase inhibitor approved for EGFR T790M mutation-positive non-small cell lung cancer.
• Severe side effects associated with olmutinib treatment are suspected to be caused by reactive intermediates.
• No previous reports exist on the structural identification of these reactive olmutinib metabolites.

Purpose of the Study:

• To investigate the formation of reactive olmutinib metabolites in rat liver microsomes.
• To structurally identify potential reactive intermediates responsible for adverse effects.
• To postulate bioactivation pathways of olmutinib.

Main Methods:

• Incubation of olmutinib with rat liver microsomes.
• Use of capturing agents: methoxylamine (for aldehydes), glutathione (for iminoquinones), and potassium cyanide (for iminium ions).
• Identification of stable complexes using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Main Results:

• The major Phase I metabolic pathway was hydroxylation of the piperazine ring.
• Seven potential reactive intermediates were characterized: three iminium ions, three iminoquinones, and one aldehyde.
• Stable complexes formed with capturing agents confirmed the presence of these reactive species.

Conclusions:

• This study provides the first structural identification of reactive olmutinib metabolites.
• The identified intermediates, including iminium ions and iminoquinones, are potential culprits for severe side effects.
• Understanding these bioactivation pathways offers insights for developing safer olmutinib-based therapies.