Evaluating Radioactive Analogs of Doxorubicin to Quantify ChemoFilter Binding and Whole-Body Positron Emission Tomography/Magnetic Resonance Imaging for Drug Biodistribution

Purpose: To evaluate radiolabeled doxorubicin (Dox) analogs as tracers of baseline Dox biodistribution in vivo during hepatic intra-arterial chemotherapy and to assess the efficacy of ChemoFilter devices to bind Dox in vitro.

Materials and methods: In an in vitro static experiment, [fluorine-18]N-succinimidyl 4-fluorobenzoate ([¹⁸F]SFB) and [fluorine-18]fluorobenzoyl-doxorubicin ([¹⁸F]FB-Dox) were added to a beaker containing a filter material (Dowex cation exchange resin, single-stranded DNA (ssDNA) resin, or sulfonated polymer coated mesh). In an in vitro flow model, [¹⁸F]FB-Dox was added into a Dox solution in phosphate-buffered saline, and the solution flowed via a syringe column containing the filter materials. In an in vitro flow experiment, using micro-positron emission tomography (PET), images were taken as [¹⁸F]SFB and [¹⁸F]FB-Dox moved through a phantom. For in vivo biodistribution testing, a catheter was placed into the common hepatic artery of a swine, and [¹⁸F]FB-Dox was infused over 30 seconds. A 10-minute dynamic image and three 20-minute static images were acquired using 3T PET/MR imaging.

Results: In the in vitro static experiment, [¹⁸F]FB-Dox demonstrated 76.7%, 88.0%, and 52.4% binding to the Dowex resin, ssDNA resin, and coated mesh, respectively. In the in vitro flow model, the first-pass binding of [¹⁸F]FB-Dox to the Dowex resin, ssDNA resin, and coated mesh was 76.7%, 74.2%, and 76.2%, respectively, and the total bound fraction was 80.9%, 84.6%, and 79.9%, respectively. In the in vitro flow experiment using micro-PET, the phantom demonstrated a greater amount of [¹⁸F]FB-Dox bound to both filter cartridges than of the control [¹⁸F]SFB. In in vivo biodistribution testing, the first 10 minutes depicted [¹⁸F]FB-Dox moving through the right upper quadrant of the abdomen. A region-of-interest analysis showed that the relative amount increased by 2.97 times in the gallbladder and 1.08 times in the kidney. The amount decreased by 0.74 times in the brain and 0.57 times in the heart.

Conclusions: [¹⁸F]FB-Dox can be used to assess Dox binding to ChemoFilters as well as in vivo biodistribution. This sets the stage for the evaluation of ChemoFilter effectiveness in reducing systemic toxicity from intra-arterial chemotherapy.