IMGN529 structure and in vitro activity. (A) Representation of the chemical structure of IMGN529, which was produced by conjugation of the DM1 maytansinoid via a thioether formed with the SMCC linker to the humanized CD37-binding K7153A antibody. Approximately 3 to 4 SMCC-DM1 moieties are linked per antibody. (B) Induction of apoptosis after 20-hour incubation with K7153A antibody, IMGN529, or nonbinding controls in Raji (left), DOHH2 (middle), and Ramos (right) cell lines. (C) ADCC activity as determined by LDH release after 4-hour incubation using purified human NK effector cells and Ramos target cells at a 3:1 ratio.