89Zr-oxalate was produced as previously described55. Approximately 1 mCi (37 MBq) of 89Zr-oxalate was neutralized to pH 7.0–7.2 using 1 M NaOH. MEHD7945A-DFO (200 µg) was added to the 89Zr solution. The reaction was quenched after 1–1.5 h incubation at room temperature upon addition of 10 µL of 50 mM EDTA (pH~7) to eliminate any non-specifically bound 89Zr. Radiolabeling efficiency and purity were determined via radio-instant Thin Layer Chromatography (iTLC) using silica gel-impregnated iTLC strip (Agilent Technologies, Santa Clara, CA) and 50 mM EDTA as the solid and mobile phase respectively. Pure 89Zr-MEHD7945A was obtained by passing through a spin column centrifugation filter (GE Vivaspin 500, MWCO: 30 kDa) with saline as the diluent. A radiochemical purity of >99% was achieved based on iTLC analysis. 89Zr-MEHD7945A was assessed for immunoreactivity as previously described56. Demetallation of 89Zr was monitored in 0.9% saline and 1:1 human serum:saline over time at 37 °C via iTLC.