Highlights on the imaging (nuclear/fluorescence) and phototherapeutic potential of a tri-functional chlorophyll-a analog with no significant toxicity in mice and rats

Herein we report the positron emission tomography (PET) imaging potential of a ¹²⁴I-labeled radiopharmaceutical (PET-ONCO). In tumored mice, it shows high uptake in a variety of tumors: brain (GL261, U87), Colon (Colon26), lung (Lewis lung), breast (4 T1), bladder (UMUC3), pancreas (PANC-1) implanted in mice. This agent also shows promise for imaging associated metastatic disease (breast to lung, to bone). Interestingly, the iodinated compound derived from chlorophyll-a, in combination with the corresponding ¹²⁴I-analog, can serve as a dual imaging agent (PET/fluorescence, complimentary to each other), with an option of photodynamic therapy (PDT). In contrast to Fluorine-18 (half-life 110 min), the Iodine-124 radionuclide has a physical half-life of roughly 4 days. Thus, unlike ¹⁸F-FDG, PET-ONCO can be transported longer distances. While the time for optimal tumor-uptake was observed at 24 h, improved tumor contrasts of both primary and metastasis were obtained at 48 and 72 h post- injection (i. v.) of PET-ONCO. In both mice and rats at a single dose study, PET-ONCO did not show any organ toxicity.

Keywords: FI: Fluorescence imaging,; PDT: Photodynamic therapy; PET: Positron emission tomography; ROI: Region of interest.