Molecular Imaging of HER2-Expressing Malignant Tumors in Breast Cancer Patients Using Synthetic 111In- or 68Ga-Labeled Affibody Molecules

The clinical utility of a human epidermal growth factor receptor 2 (HER2)-targeting Affibody molecule for detection and characterization of HER2-positive lesions was investigated in patients with recurrent metastatic breast cancer. Methods: Three patients received In-111- or Ga-68-labeled DOTA(0)-Z(HER2:342-pep2) (ABY-002). gamma-Camera, SPECT, or PET/CT images were compared with earlier F-18-FDG PET/CT results. Results: Administration of radiolabeled ABY-002 was well tolerated. Blood kinetics of radiolabeled ABY-002 showed a first half-life of 4-14 min, second half-life of 1-4 h, and third half-life of 12-18 h. Radiolabeled ABY-002 detected 9 of 11 F-18-FDG-positive metastases as early as 2-3 h after injection. Conclusion: Molecular imaging using In-111-or Ga-68-labeled ABY-002 has the potential to localize metastatic lesions in vivo, adds qualitative information not available today by conventional imaging techniques, and may allow the HER2 status to be determined for metastases not amenable to biopsy. To our knowledge, this is the first report on clinical imaging data obtained with a non-immunoglobulin-based scaffold protein.