First clinical data on ⁶⁸Ga-labeled somatostatin receptor antagonists: a phase I/II study comparing ⁶⁸Ga-OPS202 with ⁶⁸Ga-DOTATOC PET/CT.

Objectives To present the first clinical data on ⁶⁸Ga-OPS202, a radiolabeled somatostatin (sst) receptor antagonist, for PET/CT imaging of gastroenteropancreatic neuroendocrine tumors (GEP-NET) (ClinicalTrials.gov NCT02162446).

Methods Metastatic G1/G2 GEP-NET patients, with at least 1 tumor focus on previous ⁶⁸Ga-DOTATOC PET/CT, were screened for eligibility in an open-label, micro-dosing study. Safety, biodistribution, dosimetry of two single doses of ⁶⁸Ga-OPS202 (A: 15μg & B: 50μg) and preliminary efficacy in comparison with ⁶⁸Ga-DOTATOC PET/CT were investigated. ⁶⁸Ga-OPS202 doses were given within 3-4 weeks interval. All PET/CT were performed on the same scanner, >4 weeks after sst-analogs had been stopped and 1h after i.v. injection of the radiotracer.

Results Twelve patients were recruited (7 male, 5 female). No serious adverse event (AE) or AE needing medical intervention related to ⁶⁸Ga-OPS202 occurred. Patient 5 presented hypereosinophilia of undetermined origin after the first injection (mild, grade 2). Both ⁶⁸Ga-OPS202 doses (A & B) showed significantly lower uptake in the liver (mean SUVmax±σ) 3.4±0.8 (A)/3.0±0.8 (B), in the spleen 11.5±5.1 (A)/10.3±3.0 (B) and the intestine 3.6±1.5 (A)/3.0±0.9 (B) vs 6.7±2.2, 27.9±11.5 and 5.5±1.2 respectively for ⁶⁸Ga-DOTATOC (p<0.05). For the first 6 patients, 56 lesions were visible on all 3 scans. For those matched lesions ⁶⁸Ga-OPS202 PET/CT showed ~15% increase uptake (mean SUVmax±σ) 13.3±10.5 (A)/13.1±10.2 (B) vs 11.4±6.9 for ⁶⁸Ga-DOTATOC. Liver-metastases-to-liver-background uptake ratios consistently improved >2-fold (mean±σ) 4.4±3.5 (A)/4.9±3.9 (B) vs 2.1±1.5 for ⁶⁸Ga-DOTATOC resulting in a higher detection rate. Detection rate and reproducibility data of ⁶⁸Ga-OPS202 PET/CT will be shown.

Conclusions ⁶⁸Ga-OPS202 is well tolerated and shows increased image contrast compared to ⁶⁸Ga-DOTATOC PET/CT. The lower hepatic and intestinal uptake may increase the sensitivity and diagnostic confidence in staging GEP-NETs.