Multifunctional 99mTc-5-azacitidine Gold Nanoparticles: Formulation, In Vitro Cytotoxicity, Radiosynthesis, and In Vivo Pharmacokinetic Study

BACKGROUND

5-azacitidine is a very potent chemotherapeutic agent that suffers from certain disadvantages.

OBJECTIVE

This study aims to prepare gold nanoparticles as a new nano-formula of 5-azacitidine that can improve its bioavailability and decrease its side effects.

METHODS

5-azacytidine-loaded GA-AuNPs were prepared and characterized by UV-Vis spectroscopy, infrared (IR), and electronic transmission microscope (TEM). This new platform was characterized in vitro by measuring its zeta potential, particle size, and drug loading efficacy, and the anti-proliferative effect on the MCF-7 cell line was evaluated. In vivo biodistribution studies of ^99mTc-5-aza solution and ^99mTc-5-aza-gold nano formula were conducted in tumor-bearing mice by different routes of administration (intravenous and intra-tumor).

RESULTS

5-Aza-GA-AuNPs formula was successfully prepared with an optimum particle size of ≈34.66 nm, the zeta potential of -14.4 mV, and high entrapment efficiency. ^99mTc-5-Aza-GA-AuNPs were successfully radiosynthesized with a labeling yield of 95.4%. Biodistribution studies showed high selective accumulation in tumor and low uptake in non-target organs in the case of the 5-Aza-GA-AuNPs formula than the ^99mTc-5-azacitidine solution.

CONCLUSION

^99mTc-5-Aza-GA-AuNPs improved the selectivity and uptake of 5-azacitidine in cancer. Moreover, ^99mTc-5-Aza-GA-AuNPs could be used as hopeful theranostic radiopharmaceutical preparation for cancer.

Preclinical Evaluation of a Tailor-Made DOTA-Conjugated PSMA Inhibitor with Optimized Linker Moiety for Imaging and Endoradiotherapy of Prostate Cancer

Despite many advances in the past years, the treatment of metastatic prostate cancer still remains challenging. In recent years, prostate-specific membrane antigen (PSMA) inhibitors were intensively studied to develop low-molecular-weight ligands for imaging prostate cancer lesions by PET or SPECT. However, the endoradiotherapeutic use of these compounds requires optimization with regard to the radionuclide-chelating agent and the linker moiety between chelator and pharmacophore, which influence the overall pharmacokinetic properties of the resulting radioligand. In an effort to realize both detection and optimal treatment of prostate cancer, a tailor-made novel naphthyl-containing DOTA-conjugated PSMA inhibitor has been developed.

METHODS

The peptidomimetic structure was synthesized by solid-phase peptide chemistry and characterized using reversed-phase high-performance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry. Subsequent (67/68)Ga and (177)Lu labeling resulted in radiochemical yields of greater than 97% or greater than 99%, respectively. Competitive binding and internalization experiments were performed using the PSMA-positive LNCaP cell line. The in vivo biodistribution and dynamic small-animal PET imaging studies were investigated in BALB/c nu/nu mice bearing LNCaP xenografts.

RESULTS

The chemically modified PSMA inhibitor PSMA-617 demonstrated high radiolytic stability for at least 72 h. A high inhibition potency (equilibrium dissociation constant [K(i)] = 2.34 ± 2.94 nM on LNCaP; K(i) = 0.37 ± 0.21 nM enzymatically determined) and highly efficient internalization into LNCaP cells were demonstrated. The small-animal PET measurements showed high tumor-to-background contrasts as early as 1 h after injection. Organ distribution revealed specific uptake in LNCaP tumors and in the kidneys 1 h after injection. With regard to therapeutic use, the compound exhibited a rapid clearance from the kidneys from 113.3 ± 24.4 at 1 h to 2.13 ± 1.36 percentage injected dose per gram at 24 h. The favorable pharmacokinetics of the molecule led to tumor-to-background ratios of 1,058 (tumor to blood) and 529 (tumor to muscle), respectively, 24 h after injection.

CONCLUSION

The tailor-made DOTA-conjugated PSMA inhibitor PSMA-617 presented here is sustainably refined and advanced with respect to its tumor-targeting and pharmacokinetic properties by systematic chemical modification of the linker region. Therefore, this radiotracer is suitable for a first-in-human theranostic application and may help to improve the clinical management of prostate cancer in the future.