Purpose: The purpose of this study was to evaluate the safety, dosimetry, and apparent receptor occupancy (RO) of [64Cu]DOTA-patritumab, a radiolabeled monoclonal antibody directed against HER3/ERBB3 in subjects with advanced solid tumors. Procedures: Dosimetry subjects (n = 5) received [64Cu]DOTA-patritumab and underwent positron emission tomography (PET)/X-ray computed tomography (CT) at 3, 24, and 48 h. Evaluable RO subjects (n = 3 out of 6) received [64Cu]DOTA-patritumab at day 1 and day 8 (after 9.0 mg/kg patritumab) followed by PET/CT at 24 h post-injection. Endpoints included safety, tumor uptake, and efficacy. Results: The tumor SUVmax (± SD) was 5.6 ± 4.5, 3.3 ± 1.7, and 3.0 ± 1.1 at 3, 24, and 48 h in dosimetry subjects. The effective dose and critical organ dose (liver) averaged 0.044 ± 0.008 mSv/MBq and 0.46 ± 0.086 mGy/MBq, respectively. In RO subjects, tumor-to-blood ratio decreased from 1.00 ± 0.32 at baseline to 0.57 ± 0.17 after stable patritumab, corresponding to a RO of 42.1 ± 3. Conclusions: [64Cu]DOTA-patritumab was safe. These limited results suggest that this PET-based method can be used to determine tumor-apparent RO.
- Human epidermal growth factor receptor 3
- Phase 1
- Receptor occupancy