RT Journal Article SR Electronic T1 Imaging of the Glucagon Receptor in Subjects with Type 2 Diabetes JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 833 OP 838 DO 10.2967/jnumed.118.213306 VO 62 IS 6 A1 Olof Eriksson A1 Irina Velikyan A1 Torsten Haack A1 Martin Bossart A1 Iina Laitinen A1 Philip J. Larsen A1 Jan Erik Berglund A1 Gunnar Antoni A1 Lars Johansson A1 Stefan Pierrou A1 Joachim Tillner A1 Michael Wagner YR 2021 UL http://jnm.snmjournals.org/content/62/6/833.abstract AB Despite the importance of the glucagon receptor (GCGR) in disease and in pharmaceutical drug development, there is a lack of specific and sensitive biomarkers of its activation in humans. The PET radioligand 68Ga-DO3A-VS-Tuna-2 (68Ga-Tuna-2) was developed to yield a noninvasive imaging marker for GCGR target distribution and drug target engagement in humans. Methods: The biodistribution and dosimetry of 68Ga-Tuna-2 was assessed by PET/CT in 13 individuals with type 2 diabetes as part of a clinical study assessing the occupancy of the dual GCGR/glucagon like peptide-1 receptor agonist SAR425899. Binding of 68Ga-Tuna-2 in liver and reference tissues was evaluated and correlated to biometrics (e.g., weight or body mass index) or other biomarkers (e.g., plasma glucagon levels). Results: 68Ga-Tuna-2 binding was seen primarily in the liver, which is in line with the strong expression of GCGR on hepatocytes. The kidneys demonstrated high excretion-related retention, whereas all other tissue demonstrated rapid washout. The SUV55 min (SUV during the last 10-min time frame, 50–60 min after administration) uptake endpoint was sensitive to endogenous levels of glucagon. 68Ga-Tuna-2 exhibited a safe dosimetry profile and no adverse events after intravenous administration. Conclusion: 68Ga-Tuna-2 can be used for safe and accurate assessment of the GCGR in human. It may serve as an important tool in understanding the in vivo pharmacology of novel drugs engaging the GCGR.