This ADC product is comprised of an anti-CD19 monoclonal antibody (clone hBU12) conjugated via a SPDB linker to a DM4. The DM4 is targeted to certain cancers by immunerecognition and delivered into cancer cells via receptor mediated endocytosis. Within the cell, DM4 binds to tubulins, interrupts microtubule dynamics, and subsequently, induces cell death. Disulfide Linkers, are extensively exploited as a chemically labile linkage. Since the release of disulfide-linked drugs requires a cytoplasmic thiol cofactor, such as glutathione (GSH). Disulfides maintain stable at physiological pH and only when ADCs are internalized inside cells, the cytosol provides reducing environment including intracellular enzyme protein disulfide isomerase, or similar enzymes, drugs can be released. "Derived from Maytansinoid,a group of cytotoxins structurally similar to rifamycin, geldanamycin, and ansatrienin. The eponymous natural cytotoxic agent maytansine is a 19-member lactam (ansa

macrolide) structure originally isolated from the Ethiopian shrub Maytenus ovatus. Maytansinoids can bind to tubulin at or near the vinblastine-binding site, which interfere the formation of microtubules and depolymerize already formed microtubules, inducing mitotic arrest in the intoxicated cells."