TY - JOUR T1 - <strong>Development of <sup>89</sup>Zr-labeling ADC Method for Translational Development of ADCs</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 244 LP - 244 VL - 59 IS - supplement 1 AU - Yumin Zhang AU - Todd Cole AU - Anthony Giamis AU - John Harlan AU - xinxin zhang AU - Dong Cheng AU - David Reuter AU - Martin Voorbach AU - Debra Ferguson AU - Anthony Haight AU - Laurent MARTARELLO AU - Robert Comley Y1 - 2018/05/01 UR - http://jnm.snmjournals.org/content/59/supplement_1/244.abstract N2 - 244Objectives: Optimal anti-cancer antibody drug conjugates (ADC) should show preferential targeting with high accumulation in tumors and low uptake in healthy tissues. Radiolabeling an ADC construct with zirconium-89 (89Zr), combined with positron emission tomography (PET) imaging enables non-invasive, whole-body, longitudinal tracking of ADC biodistribution. Using this approach one can directly evaluate in both preclinical models and patients whether an ADC retains its carrier monoclonal antibody’s (mAb) selective tumor targeting capability. However, although the 89Zr radiolabeling methodologies are well established for mAbs, the use of those approaches for the labelling of ADCs has proved to be problematic, the distinct physical-chemical properties of ADCs resulting in instability and a loss of the 89Zr label which accumulates in bone. Here we report the successful development of a novel 89Zr-radiolabeling method for ADCs which retains the in vivo stability, enabling PET imaging. Methods: Five ADC constructs consisting of human mAbs and MMAE toxin payload were conjugated with desferrioxamine (DFO) bifunctional chelator at 37oC for 1 h. Protein-A affinity purification was used to remove the unconjugated free DFO. After elution with pH 3.0 glycine, the DFO-ADCs were formulated into acetate radiolabeling buffer (pH 6.5) via routine PD-10 chromatography, and frozen at -80oC until use. The ratio of DFO groups per mAb was confirmed by mass spec. The thawed bioconjugated proteins were radiolabeled with neutralized 89Zr-zirconium oxalate and formulated for intravenous administration. Results With input mAb/DFO ratio of 1:3, the conjugated DFO groups per mAb ranged from 0.6 to 1.2, depending on the mAb/ADC combination. Specific activities ranged from 0.5 to 5 mCi/mg; labeling efficiency was no less than 98%. Stable preparations of 89Zr-ADCs were obtained. The ADCs showed similar biodistribution when compared to their parental carrier mAbs, and retained the same selective tumor accumulation as their carrier mAbs. No aberrant bone uptake of 89Zr was evident. Conclusions The procedure of 89Zr radiolabeling ADC constructs proved to be robust. Stable radiolabeling allows the use of immunoPET for in vivo comparison of multiple carrier antibodies, and the same antibody with different types of toxin payloads, and the same payload with different drug/antibody ratios (DAR), thereby helping select the most promising ADC candidates to move towards clinical development. In addition, clinical imaging studies with labeled ADC or carrier mAb may provide an efficient way to demonstrate tumor target in man in a small number of patients prior to phase 1 dose-escalation studies. ER -