First-in-Human Study of a⁶⁴Cu-Labeled Long-acting Integrin αvβ3 Targeting Molecule⁶⁴Cu-NOTA-EB-RGD in Healthy Volunteers and GBM Patients

Objectives: This study aimed to explore the safety, biodistribution and dosimetry of a long-acting integrin α_vβ₃-targeted PET tracer ⁶⁴Cu-NOTA-EB-RGD in humans, and to assess the pharmacokinetics and diagnostic feasibility of ⁶⁴Cu-NOTA-EB-RGD in glioblastoma multiforme (GBM) patients.

Methods: Following institutional review board approval and informed consent, three healthy volunteers (2 male and 1 female) underwent whole-body PET/CT at 0.5, 1.0, 8.0, 12.0 and 24.0 hours after a bolus injection of ⁶⁴Cu-NOTA-EB-RGD (148-296 MBq [4-8 mCi]). Safety data were collected before, 1 day and 1 week after the injection, including vital signs (blood pressure, pulse rate, respiratory frequency, and temperature), physical examination, electrocardiography, laboratory parameters (blood biochemistry, hematologic, kidney and liver function tests), and adverse events. Regions of interest were drawn manually over major organs, and time-activity curves were obtained. Dosimetry was calculated using the OLINDA/EXM software. ⁶⁴Cu-NOTA-EB-RGD was also administered to a patient with recurrent GBM. Seven sets of brain PET or PET/CT scans of the patient were acquired over two consecutive days. The time points of image acquisition were 30 min, 1 h, 8 h, 12 h, 20 h, 20.5 h and 24 h after injection of the radiopharmaceutical. Tumor-to-background ratios (TBR) were calculated using volume of interest (VOI) based SUV_max and SUV_mean for target tumor lesion and SUV_mean for normal brain tissue as the background. Within 1 week after tracer administration, the patient underwent surgical treatment and immunohistochemical staining of tumor samples against integrin α_vβ₃ was performed.

Results: The administration of ⁶⁴Cu-NOTA-EB-RGD was well tolerated, with no adverse symptoms or signs being noticed or reported either immediately or up to 1 week after the administration. ⁶⁴Cu-NOTA-EB-RGD uptake at 1 h p.i. was seen in the blood pool, kidneys, and bladder, with low accumulation in other normal organs. The organ with the highest radiation dose was the urinary bladder. The mean effective dose and effective dose equivalent of ⁶⁴Cu-NOTA-EB-RGD were 0.0315 mSv/MBq ± 0.0052 and 0.0454 mSv/MBq ± 0.0088, as compared to the previously reported ⁶⁸Ga-NOTA-PRGD2 of 0.0226 mSv/MBq and 0.0277 mSv/MBq, respectively, and an effective dose of 0.0315 mSv/MBq (0.1166 rem/mCi) represents exposure of 0.933 rem for a subject injected with 8 mCi, which was very similar to an ¹⁸F-FDG PET scan. The mean absorbed dose of kidneys and red marrow of ⁶⁴Cu-NOTA-EB-RGD were 0.0994 mSv/MBq ± 0.0425 and 0.0230 mSv/MBq ± 0.0027.Injection of ⁶⁴Cu-NOTA-EB-RGD to the patient with recurrent GBM showed high accumulation at the tumor which increased over time, reaching SUV_max of 6.25 at 12 h p.i., and decreased slightly by 24 h, but with continuously increased tumor-to-background (unaffected brain area) contrast over time. TBR ratio based on SUV_maxand SUV_mean reached a maximum of 73.4 and 40.2 at 24 h p.i., respectively. Post-operative pathology revealed WHO grade IV glioblastoma multiforme and immunohistochemical staining showed moderate expression of integrin α_vß₃.

Conclusions: This first-in-human study indicates the safety, favorable pharmacokinetic and dosimetry profile of a new type of PET tracer using a relatively long half-life PET isotope ⁶⁴Cu-labeled long-acting integrin α_vβ₃-targeted molecule EB-RGD. By introducing an EB-derived albumin-binding moiety to enhance tumor uptake, ⁶⁴Cu-NOTA-EB-RGD provides a superior pharmacokinetics and high contrast for diagnostic imaging purposes in GBM patient. The results shown here for ⁶⁴Cu-labeled EB-RGD are promising and very attractive for theranostic applications like ⁶⁷Cu, ¹⁷⁷Lu, ⁹⁰Y or ²²⁵Ac as therapeutic counterparts. Further investigations with matched pairs of copper and other therapeutic agents are warranted.

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