TY - JOUR T1 - Phase I Trial of <sup>131</sup>I-GMIB-Anti-HER2-VHH1, a New Promising Candidate for HER2-Targeted Radionuclide Therapy in Breast Cancer Patients JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1097 LP - 1105 DO - 10.2967/jnumed.120.255679 VL - 62 IS - 8 AU - Matthias D’Huyvetter AU - Jens De Vos AU - Vicky Caveliers AU - Ilse Vaneycken AU - Johannes Heemskerk AU - Francois P. Duhoux AU - Christel Fontaine AU - Marian Vanhoeij AU - Albert D. Windhorst AU - Frank van der Aa AU - N. Harry Hendrikse AU - Jos L.E. Eersels AU - Hendrik Everaert AU - Pieterjan Gykiere AU - Nick Devoogdt AU - Geert Raes AU - Tony Lahoutte AU - Marleen Keyaerts Y1 - 2021/08/01 UR - http://jnm.snmjournals.org/content/62/8/1097.abstract N2 - 131I-GMIB-anti-human epidermal growth factor receptor type 2 (HER2)-VHH1 is a targeted radionuclide theranostic agent directed at HER2-expressing cancers. VHH1 is a single-domain antibody covalently linked to therapeutic 131I via the linker N-succinimidyl 4-guanidino-methyl-3-iodobenzoate (SGMIB). The phase I study was aimed at evaluating the safety, biodistribution, radiation dosimetry, and tumor-imaging potential of 131I-GMIB-anti-HER2-VHH1 in healthy volunteers and breast cancer patients. Methods: In a first cohort, 6 healthy volunteers were included. The biodistribution of 131I-GMIB-anti-HER2-VHH1 was assessed using whole-body (anterior and posterior) planar images obtained at 40 min and at 2, 4, 24, and 72 h after intravenously administered (38 ± 9 MBq) 131I-GMIB-anti-HER2-VHH1. Imaging data were analyzed using OLINDA/EXM software to determine the dosimetry. Blood and urine samples were obtained over 72 h. In the second cohort, 3 patients with metastatic HER2-positive breast cancer were included. Planar whole-body imaging was performed at 2 and 24 h after injection. Additional SPECT/CT images were obtained after the whole-body images at 2 and 24 h if there was relevant uptake in known cancer lesions. Results: No drug-related adverse events were observed throughout the study. The biologic half-life of 131I-GMIB-anti-HER2-VHH1 in healthy subjects was about 8 h. After intravenous administration, the compound was eliminated from the blood with a 2.5-h half-life. The drug was eliminated primarily via the kidneys. The drug was stable in circulation, and there was no increased accumulation in the thyroid or stomach. The absorbed dose to the kidneys was 1.54 ± 0.25 mGy/MBq, and to bone marrow it was 0.03 ± 0.01 mGy/MBq. SPECT/CT imaging in patients with advanced breast cancer showed focal uptake of 131I-GMIB-anti-HER2-VHH1 in metastatic lesions. Conclusion: Because of its favorable toxicity profile and its uptake in HER2-positive lesions, this radiopharmaceutical can offer new therapeutic options to patients who have progressed on trastuzumab, pertuzumab, or trastuzmab emtansine, given its difference in mode-of-action. A dose escalation is planned in a subsequent phase I/II study to assess the therapeutic window of this compound (NCT04467515). ER -