Spatiotemporal Profiling of Intratumoral Free Payload Distribution via MALDI Imaging Mass Spectrometry: Implications for Drug-to-Antibody Ratio Optimization in Antibody-Drug Conjugates. - Cai T; Li Z; Yan Q; Huang G; Jia K; Chen X; Dun J; Zou J; Tan M; Wu Y; Wang F (The AAPS journal, 2026)