Development of a Novel Immunoprecipitation Method for Extracting Monoclonal Antibodies From Brain Tissue and Its Application to Assessing In Vivo Brain Penetration in Mouse via Liquid Chromatography–Mass Spectrometry

A novel extraction method was developed to quantify monoclonal antibodies from brain tissue, crucial for pharmacokinetic assessments. We focused on optimizing detergent use for compatibility with liquid chromatography–mass spectrometry analysis. IGEPAL and sodium deoxycholate were selected for their ability to preserve antibody integrity during extraction, with conditions optimized to a 4% concentration. This was most effective for maintaining antibody structure and maximizing recovery. Pharmacokinetic analysis was conducted on the 8D3 monoclonal antibody, known for its brain penetration abilities. Administered at 20 mg/kg, its concentration in the brain was measured using the optimized extraction methods. The 4% SDC method showed superior extraction efficiency, significantly enhancing brain exposure levels with a higher maximum concentration and area under the curve compared to the 4% IGEPAL and detergent‐free methods. This highlights the importance of detergent selection in accurate pharmacokinetic measurements. We also addressed potential blood contamination. Specific perfusion conditions effectively removed 98% of blood contaminants, ensuring that pharmacokinetic measurements reflected true monoclonal antibody levels in brain tissue. Overall, this study establishes a robust method for monoclonal antibody extraction from brain tissue, enhancing the analysis of brain‐targeted therapies and providing a valuable framework for future studies aiming to measure drug concentrations in brain tissue.