Theranostic Polyaminocarboxylate-Cyanine-Transferrin Conjugate for Anticancer Therapy and Near-Infrared Optical Imaging.

Iron chelation therapy has been recognized as a promising antitumor therapeutic strategy. Herein we report a novel theranostic agent for targeted iron chelation therapy and near-infrared (NIR) optical imaging of cancers. The theranostic agent was prepared by incorporation of a polyaminocarboxylate-based cytotoxic chelating agent (N-NE3TA; 7-[2-[(carboxymethyl)amino]ethyl]-1,4,7-triazacyclononane-1,4-diacetic acid) and a NIR fluorescent cyanine dye (Cy5.5) onto a tumor-targeting transferrin (Tf). The N-NE3TA-Tf conjugate (without Cy5.5) was characterized and evaluated for antiproliferative activity in HeLa, HT29, and PC3 cancer cells, which have elevated expression levels of the transferrin receptor (TfR). The N-NE3TA-Tf conjugate displayed significant inhibitory activity against all three cancer cell lines. The NIR dye Cy5.5 was then incorporated into N-NE3TA-Tf, and the resulting cytotoxic and fluorescent transferrin conjugate N-NE3TA-Tf-Cy5.5 was shown by microscopy to enter TfR-overexpressing cancer cells. This theranostic conjugate has potential application for dual use in targeted iron chelation cancer therapy and NIR fluorescence imaging.

Synthesis and preclinical evaluation of bifunctional ligands for improved chelation chemistry of 90Y and 177Lu for targeted radioimmunotherapy.

We report a practical and high-yield synthesis of a bimodal bifunctional ligand 3p-C-NETA-NCS containing the isothiocyanate group for conjugation to a tumor targeting antibody. 3p-C-NETA-NCS was conjugated to a tumor-targeting antibody, trastuzumab, and the corresponding 3p-C-NETA-trastuzumab conjugate was evaluated and compared to trastuzumab conjugates of the known bifunctional ligands C-DOTA, C-DTPA, and 3p-C-DEPA for radiolabeling kinetics with (90)Y and (177)Lu. 3p-C-NETA-trastuzumab conjugate exhibited extremely rapid complexation kinetics with (90)Y and (177)Lu. (90)Y-3p-C-NETA-trastuzumab and (177)Lu-3p-C-NETA-trastuzumab conjugates were stable in human serum for 2 weeks. A pilot biodistribution study was conducted to evaluate in vivo stability and tumor targeting of (177)Lu-radiolabeled trastuzumab conjugate using nude mice bearing ZR-75-1 human breast cancer. (177)Lu-3p-C-NETA-trastuzumab conjugate displayed low radioactivity level at blood (1.6%), low organ uptake (<2.2%), and high tumor-to-blood ratio (6.4) at 120 h. 3p-C-NETA possesses favorable in vitro and in vivo profiles and is an excellent bifunctional chelator that can be used for targeted RIT applications using (90)Y and (177)Lu and has the potential to replace DOTA and DTPA analogues in current clinical use.

Synthesis and evaluation of a bifunctional chelate for development of Bi(III)-labeled radioimmunoconjugates.

A new bifunctional ligand C-DEPA was designed and synthesized as a component for antibody-targeted radiation therapy (radioimmunotherapy, RIT) of cancer. C-DEPA was conjugated to a tumor targeting antibody, trastuzumab, and the corresponding C-DEPA-trastuzumab conjugate was evaluated for radiolabeling kinetics with (205/6)Bi. C-DEPA-trastuzumab conjugate rapidly bound (205/6)Bi, and (205/6)Bi-C-DEPA-trastuzumab conjugate was stable in human serum for 72 h. The in vitro radiolabeling kinetics and serum stability data suggest that C-DEPA is a potential chelate for preclinical RIT applications using (212)Bi and (213)Bi.

Synthesis and evaluation of novel polyaminocarboxylate-based antitumor agents.

Iron depletion, using iron chelators targeting transferrin receptor (TfR) and ribonucleotide reductase (RR), is proven to be effective in the treatment of cancer. We synthesized and evaluated novel polyaminocarboxylate-based chelators NETA, NE3TA, and NE3TA-Bn and their bifunctional versions C-NETA, C-NE3TA, and N-NE3TA for use in iron depletion tumor therapy. The cytotoxic activities of the novel polyaminocarboxylates were evaluated in the HeLa and HT29 colon cancer cell lines and compared to the clinically available iron depletion agent DFO and the frequently explored polyaminocarboxylate DTPA. All new chelators except C-NETA displayed enhanced cytotoxicities in both HeLa and HT29 cancer cells compared to DFO and DTPA. Incorporation of the nitro functional unit for conjugation to a targeting moiety into the two potent non-functionalized chelators NE3TA and NE3TA-Bn (C-NE3TA and N-NE3TA) was well-tolerated and resulted in a minimal decrease in cytotoxicity. Cellular uptake of C-NE3TA, examined using a confocal microscope, indicates that the chelator is taken up into HT29 cancer cells.