Radiopharmaceutical kit to prepare Copper-64 labelled porphyrin-lipid nanoparticles for radiotracer imaging studies in cancer patients.

Abstract

PORPHYSOMES (PS) are multifunctional porphyrin-lipid nanoparticles for fluorescence-guided photochemical tumour ablation and immune stimulation. PS can be radiolabelled with Copper-64 (⁶⁴Cu-PS) to permit tracing of their whole-body distribution and uptake in tumours with nuclear imaging. Herein we characterised the physicochemical and radiochemical properties of PS and ⁶⁴Cu-PS and evaluated their pharmacology and toxicology in rats and dogs. ⁶⁴Cu-PS labelling procedure was optimised and developed into a "one pot" kit format. The plasma pharmacokinetics (PK), tissue distribution, and single and repeat-dose toxicity of dose escalating PS was evaluated after intravenous injection in healthy Fisher 344 rats and Beagle dogs. Radiation dosimetry from single ⁶⁴Cu-PS dose was estimated in humans. Kit prepared ⁶⁴Cu-PS had high labelling yields and mean specific activities of 18.5 MBq/mg (11.4 GBq/mg max). The plasma PK of PS was linear between doses 0.5-15 mg/kg in both rats and dogs. Tissue distribution was primarily to the liver. The estimated effective dose from ⁶⁴Cu-PS in humans was 38-47 µSv/MBq. Single doses of 32.6 mg/kg PS did not have detectable toxicities in rats. In dogs, mild transient infusion reactions were observed following single and repeat-doses of PS starting at ≥ 10 mg/kg PS. Doses up to 15 mg/kg PS were tolerated in dogs. The pharmacology and safety profiles of PS and ⁶⁴Cu-PS in rats and dogs did not raise concerns regarding their use in humans. Radiolabelled ⁶⁴Cu-PS will permit accurate imaging-based assessments of nanoparticle PK and tumour uptake in imaging studies in cancer patients.