International Journal of Pharmaceutics 632 (2023) 122527 Available online 23 December 2022 0378-5173/© 2022 Elsevier B.V. All rights reserved. 61 Cu-Labelled radiodiagnostics of melanoma with NAPamide-targeted radiopharmaceutical Ibolya K´ alm´ an-Szab´ o a, b, 1 , Szilvia Bunda c, 1 , Norbert Lihi d, * , Zs´ ofa Szaniszl´ o c , Dezs˝ o Szikra a , Judit Szab´ o P´ elin´ e a , Anik´ o Fekete a , Barbara Gyuricza a , D´ aniel Szücs a , G´ abor Papp c , Gy¨ orgy Trencs´ enyi a, b , Ferenc K. K´ alm´ an c, * a Division of Nuclear Medicine and Translational Imaging, Department of Medical Imaging, University of Debrecen, Egyetem t´ er 1., H-4032 Debrecen, Hungary b Gyula Petr´ anyi Doctoral School of Clinical Immunology and Allergology, Faculty of Medicine, University of Debrecen, Nagyerdei St. 98, H-4032 Debrecen, Hungary c Department of Physical Chemistry, University of Debrecen, Egyetem t´ er 1., H-4032 Debrecen, Hungary d ELKH-DE, Mechanisms of Complex Homogeneous and Heterogeneous Chemical Reactions Research Group, Department of Inorganic and Analytical Chemistry, University of Debrecen, Egyetem t´ er 1., H-4032 Debrecen, Hungary A R T I C L E INFO Keywords: Cu-61 Radiotherapy Melanoma Positron emission tomography (PET) NAPamide ABSTRACT Malignant melanoma is a major public health problem with an increasing incidence and mortality in the Caucasian population due to its signifcant metastatic potential. The early detection of this cancer type by im- aging techniques like positron emission tomography acts as an important contributor to the long-term survival. Based on literature data, the radio labelled alpha-MSH analog NAPamide molecule is an appropriate diagnostic tool for the detection of melanoma tumors. Inspired by these facts, a new radiotracer, the [ 61 Cu]Cu-KFTG- NAPamide has been synthesized to exploit the benefcial features of the positron emitter 61 Cu and the melanoma specifcity of the NAPamide molecule. In this work, we report a new member of the CB-15aneN 5 ligand family (KFTG) as the chelator for 61 Cu(II) complexation. On the basis of the thorough physico-chemical characteriza- tion, the rigid [Cu(KFTG)] + complex exhibits fast complex formation (t 1/2 = 155 s at pH 5.0 and 25 ◦ C) and high inertness (t 1/2 = 2.0 h in 5.0 M HCl at 50 ◦ C) as well as moderate superoxide dismutase activity (IC 50 = 2.3 μM). Furthermore, the [ 61 Cu]Cu-KFTG-NAPamide possesses outstanding features in the diagnostics of B16-F10 mel- anoma tumors by PET imaging: (T/M(SUVs) (in vivo): appr. 14, %ID/g: 7 ± 1 and T/M (ex vivo): 315 ± 24 at 180 min). 1. Introduction Among skin cancers melanoma malignum is the most aggressive malignancy with high mortality rate and associated with high metastatic potential.(Ahmed et al., 2020) The metastatic lesions in several organs (e.g. brain, liver, lung) largely reduce the chance of patient survival and the fve-year survival rate falls between 5 and 19 %.(Sandru et al., 2014) Due to its high metastatic potential, the early diagnosis of small and distant metastases is crucial, thus, high-resolution imaging techniques (e.g. Positron Emission Tomography (PET) or Magnetic Resonance Im- aging (MRI)) are frequently used to detect such metastases.(McIvor et al., 2014; Rodriguez Rivera et al., 2014). In the last decade, several melanoma-specifc radiolabeled molecules (e.g. antibodies,(Thompson et al., 2014) α-MSH receptor (alpha- Melanocyte-Stimulating hormone) ligands(Gao et al., 2016) and ben- zamide derivatives(Kim et al., 2012)) have been developed for PET imaging of melanoma. In the feld of nuclear medicine, the melanocortin-1 receptor (MC1-R) – as a G-protein-coupled cell mem- brane receptor – is one of the most promising targets due to its signif- cant overexpression on the surface of melanoma metastases.(Chung et al., 2012; Rosenkranz et al., 2013) Alpha melanocyte stimulating hormone (α-MSH) analogues, e.g. NAPamide peptide, specifcally bind to the MC1-R receptors. For in vivo preclinical PET imaging several 64 Cu- ,Cheng et al., 2007a 68 Ga-, 44 Sc-,(Nagy et al., 2017) 18 F-,(Ren et al., 2009; Cheng et al., 2007b) 111 In- and 99m Tc-labelled(Miao et al., 2007) NAPamide analogues are reported as potential melanoma-specifc radiopharmaceuticals. Beyond the widely used 64 Cu isotope, the diagnostic and therapeutic * Corresponding authors. E-mail addresses: lihi.norbert@science.unideb.hu (N. Lihi), kalman.ferenc@science.unideb.hu (F.K. K´ alm´ an). 1 These authors contributed equally. Contents lists available at ScienceDirect International Journal of Pharmaceutics journal homepage: www.elsevier.com/locate/ijpharm https://doi.org/10.1016/j.ijpharm.2022.122527 Received 26 October 2022; Received in revised form 15 December 2022; Accepted 17 December 2022