Preclinical evaluation of anthraquinone based macrocyclic ⁶⁸Ga-DO3A-Act-AQ: a potential probe for theranostic application

Positron emission tomography (PET) with positron emitter ⁶⁸Ga-based imaging probe is an upcoming field in molecular imaging as the radionuclide ⁶⁸Ga is instantaneously available via the ⁶⁸Ge/⁶⁸Ga radionuclide generator, have half-life of 67.7 min and a positron abundance of 89% making it suitable for PET imaging. Anthraquinone based compounds are known for their prominent position in cancer chemotherapy. They act at the duplex DNA level through stabilization of ternary complex with DNA topoisomerase ΙΙ. Their mode of action relates to their ability of damaging the nucleic acid thereby inducing cell death. It has been known that telomerase activity is high in tumor cells than other somatic cells, thus tumor cells have an almost infinite capacity to divide and hence can be immortalized. Many amino anthraquinone derivatives are reported of having telomerase inhibiting activity. Herein, the objective is to develop a new bi-functional chelating agent based on DO3A for labeling ⁶⁸Ga and conjugate it with anthraquinone derivative to synthesize DO3A based anthraquinone derivative for imaging with application in PET and therapeutic purpose. (4,7-Biscarboxymethyl- 10-( (9,10-dioxo-9,10-dihydro-anthracen-1-ylcarbamoyl)- methyl)-1,4,7,10tetraaza-cyclododec-1-yl)-acetic acid was synthesized and characterized by NMR and mass spectroscopy. Initial radiolabeling studies showed high radiolabeling efficiency with ⁶⁸Ga >95%. Its biological potential as probe was checked by cytotoxicity on healthy and cancer cell lines (HEK and BMG-1). DNA binding and anticancer property of DO3A-Act-AQ was verified through fluorescence, CD spectroscopy and flow cytometry. The clearance of radio complex from the blood checked through blood kinetics experiment was within 40 min. Tumor uptake and biodistribution experiments using athymic nude mice xenografted with BMG-1 cell were performed. DO3AAct- AQ is successfully synthesized, characterized and radiolabeled with ⁶⁸Ga. Initial studies suggests strong binding CT-DNA, anticancer property and rapid clearance from the blood. Further investigations like biodistribution characteristics and PET imaging confirmed high affinity towards tumor site in BMG-1 cells xenografted athymic mice which further support its future as theranostic agent