In vitro and in vivo characterization of [64Cu][Cu(elesclomol)] as a novel theranostic agent for hypoxic solid tumors

Tengzhi Liu; Maria Aanesland Dahle; Mathilde Hirsum Lystad; Laure Marignol; Morten Karlsen; Kathrine Røe Redalen

doi:10.1007/s00259-023-06310-4

In vitro and in vivo characterization of [⁶⁴Cu][Cu(elesclomol)] as a novel theranostic agent for hypoxic solid tumors

Eur J Nucl Med Mol Imaging. 2023 Oct;50(12):3576-3588. doi: 10.1007/s00259-023-06310-4. Epub 2023 Jun 29.

Authors

Tengzhi Liu^{1

2}, Maria Aanesland Dahle¹, Mathilde Hirsum Lystad¹, Laure Marignol³, Morten Karlsen², Kathrine Røe Redalen⁴

Affiliations

¹ Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
² Department of Radiology and Nuclear Medicine, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.
³ Applied Radiation Therapy Trinity, Discipline of Radiation Therapy, Trinity St. James's Cancer Institute, Trinity College, Dublin, Ireland.
⁴ Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway. kathrine.redalen@ntnu.no.

Abstract

Purpose: Hypoxic tumors are associated with therapy resistance and poor cancer prognosis, but methods to detect and counter tumor hypoxia remain insufficient. Our purpose was to investigate ⁶⁴Cu(II)-elesclomol ([⁶⁴Cu][Cu(ES)]) as a novel theranostic agent for hypoxic tumors, by implementing an improved production method and assessing its therapeutic and diagnostic potential compared to the established Cu-64 radiopharmaceuticals [⁶⁴Cu]CuCl₂ and [diacetyl-bis(N4-methylthiosemicarbazone) [⁶⁴Cu][Cu(ATSM)].

Methods: Cu-64 was produced using a biomedical cyclotron at 12 MeV with the reaction ⁶⁴Ni(p,n)⁶⁴Cu, followed by synthesis of [⁶⁴Cu]CuCl₂, [⁶⁴Cu][Cu(ATSM)], and [⁶⁴Cu][Cu(ES)]. In vitro therapeutic effects were assessed in both normoxic and hypoxic cells (22Rv1 and PC3 prostate cancer cells, and U-87MG glioblastoma cells) using the clonogenic assay and analyzing cellular uptake and internalization. In vivo therapeutic effects were assessed in 22Rv1 xenografts in BALB/cAnN-Foxn1nu/nu/Rj mice receiving a single or multiple doses of radiopharmaceutical, before their feasibility to detect tumor hypoxia was assessed by positron emission tomography (PET) in 22Rv1 and U-87MG xenografts.

Results: In vitro and in vivo studies demonstrated that [⁶⁴Cu][Cu(ES)] reduced cell survival and inhibited tumor growth more effectively than [⁶⁴Cu][Cu(ATSM)] and [⁶⁴Cu]CuCl₂. Hypoxia increased the cellular uptake and internalization of [⁶⁴Cu][Cu(ES)] and [⁶⁴Cu][Cu(ATSM)]. [⁶⁴Cu][Cu(ES)]-PET tumor hypoxia detection was feasible and also revealed an unexpected finding of uptake in the brain.

Conclusion: To the best of our knowledge, this is the first time that ES is radiolabeled with [⁶⁴Cu]CuCl₂ to [⁶⁴Cu][Cu(ES)]. We demonstrated superior therapeutic effects of [⁶⁴Cu][Cu(ES)] compared to [⁶⁴Cu][Cu(ATSM)] and [⁶⁴Cu]CuCl₂ and that [⁶⁴Cu][Cu(ES)]-PET is feasible. [⁶⁴Cu][Cu(ES)] is a promising theranostic agent for hypoxic solid tumors.

Keywords: 64Cu-elesclomol; Cancer; Hypoxia; Positron emission tomography; Theranostics.