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.