Three Methods for ¹⁸F Labeling of the HER2-Binding Affibody Molecule Z_HER2:2891 Including Preclinical Assessment

Positron Emission Tomography Imaging with 18F-Labeled ZHER2:2891 Affibody for Detection of HER2 Expression and Pharmacodynamic Response to HER2-Modulating Therapies

“…In this context previous Affibodies labeled with 68 Ga or 111 In showed approximately 10-fold higher renal localization than that seen in tumor (34,35,38), precluding imaging of tumors in the region around the kidney, as well as having an impact on dosimetry. Bioconjugation of the Affibody molecule with albumin, histidine containing tags or 18 F radiolabels have been proposed as alternative approaches to avoid tubular reabsorption and permitting rapid glomerular filtration (26,(39)(40)(41). Using a radiohalogen strategy with 18 F, we demonstrated rapid renal clearance of […”

“…By comparison with other molecular imaging probes, Affibodies benefit from a short blood circulation time and high target affinity resulting in high-contrast images within a relatively short time after injection, and slower internalization rates (26,34,35). This permits utilization of more widely available short-lived radioisotopes, such as 18 F and 68 Ga, minimizing the patient's dosimetry. In comparison with nanobodies, Affibodies excel through lower K D , higher k on , and slower k off rates (36).…”

“…However, within this early period, nonspecific uptake could contribute to tissue signal. We therefore assessed the specificity of 18 18 F]GE-226, for early imaging (1 hour) using both intrinsic cellular uptake and in vivo dynamic imaging to quantitatively discriminate between HER2-negative and HER2-positive tumors.…”

“…S1 and described elsewhere (18). Typical nondecay corrected end of synthesis yields were 30% and a radiochemical purity of 95%.…”

“…Because HER2-positive and HER2-negative xenografts described in Fig. 3 have greatly varying growth rates and require differential hormonal treatments, we used A431 (HER2-negative) and NCI-N87 (HER2-positive) xenografts as previously described (18). A mixture of 20 mg/kg Hoechst and 15 mg/kg fluorescein-conjugated GE-226 in PBS were injected intravenously and 2-hour postinjection, tumors were excised, formalin fixed, and paraffin embedded and adjacent tumor sections prepared for HercepTest staining or fluorescent microscopy.…”