Pharmacodynamic studies of ADCT-402. (A) Representative scans of FFPE Ramos xenograft tumor sections, obtained from vehicle-treated control mice or mice treated with 0.3 and 1 mg/kg ADCT-402 or 1 mg/kg nontargeting ADC and stained with an anti-CD19 antibody (top), anti-PBD linker antibody (middle), or an anti-γ-H2AX antibody (bottom). (B) Histogram depicting % cells with γ-H2AX in tumor cell suspensions taken from Ramos xenograft tumors 24 hours after injection with vehicle or 0.3 or 1 mg/kg ADCT-402 or 1 mg/kg nontargeted ADC. Data represent the mean and SD from 3 individual mice per data point. **P ≤ .01, ***P ≤ .001. (C) Histogram depicting mean OTM in irradiated (I) or unirradiated (UI) tumor cell suspensions taken from Ramos xenograft tumors 24 hours after injection with vehicle or 0.3 mg/kg or 1 mg/kg ADCT-402 or 1 mg/kg nontargeted ADC. Data represent the mean and SD from 3 individual mice per data point. Statistical analysis was done with unpaired t test with Welch correction (not assuming equal SDs). P values are 2-tailed; *P ≤ .05, **P ≤ .01. SD, standard deviation.