Quantitative Mass Spectrometry‐Based Biodistribution of Monoclonal Antibodies: An Alternative to Radio‐Biodistribution

Monoclonal antibodies (mAbs) are excellent tools for generating targeted therapies for cancer treatment, and an early assessment of their biodistribution properties is essential in the discovery process. Traditionally, radiolabeling methods are widely used, but they require structural alterations of the antibody, radiation exposure, and specialized infrastructure. In this work, we present the implementation of a non-radioactive Mass Spectrometry (MS)-based method to assess the ex vivo quantitative biodistribution of tumor-targeting mAbs directed against the tumor extracellular matrix. By combining protein A purification with a stable isotopically labeled standard, we obtained a versatile method that can be easily transferred to different analytes. The methodology was orthogonally validated by direct comparison against radiolabel-based biodistribution studies, demonstrating high reliability and accuracy.