TY - JOUR T1 - Antibody Drug Conjugates Differentiate Uptake and DNA Alkylation of Pyrrolobenzodiazepines in Tumors from Organs of Xenograft Mice JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 1958 LP - 1962 DO - 10.1124/dmd.116.073031 VL - 44 IS - 12 AU - Yong Ma AU - S. Cyrus Khojasteh AU - Cornelis E.C.A. Hop AU - Hans K. Erickson AU - Andrew Polson AU - Thomas H. Pillow AU - Shang-Fan Yu AU - Hong Wang AU - Peter S. Dragovich AU - Donglu Zhang Y1 - 2016/12/01 UR - http://dmd.aspetjournals.org/content/44/12/1958.abstract N2 - Pyrrolobenzodiazepine (PBD)-dimer is a DNA minor groove alkylator, and its CD22 THIOMAB antibody drug conjugate (ADC) demonstrated, through a disulfide linker, an efficacy in tumor reduction for more than 7 weeks with minimal body weight loss in xenograft mice after a single 0.5–1 mg/kg i.v. dose. The DNA alkylation was investigated here in tumors and healthy organs of mice to understand the sustained efficacy and tolerability. The experimental procedures included the collection of tumors and organ tissues of xenograft mice treated with the ADC followed by DNA isolation/hydrolysis/quantitation and payload recovery from reversible DNA alkylation. PBD-dimer formed a considerable amount of adducts with tissue DNA, representing approximately 98% (at 24 hours), and 99% (at 96 hours) of the total PBD-dimer in tumors, and 78–89% in liver and lung tissues, suggesting highly efficient covalent binding of the released PBD-dimer to tissue DNA. The amount of PBD-DNA adducts in tumor tissues was approximately 24-fold (at 24 hours) and 70-fold (at 96 hours) greater than the corresponding amount of adducts in liver and lung tissues. In addition, the DNA alkylation levels increased 3-fold to 4-fold from 24 to 96 hours in tumors [41/106 base pairs (bp) at 96 hours] but remained at the same level (1/106 bp) in livers and lungs. These results support the typical target-mediated cumulative uptake of ADC into tumors and payload release that offers an explanation for its sustained antitumor efficacy. In addition, the low level of DNA alkylation in normal tissues is consistent with the tolerability observed in mice. ER -