Synthesis and Evaluation of Amino Acid-Based Radiotracer 99mTc-N4-AMT for Breast Cancer Imaging

Abstract EN

Purpose.

This study was to develop an efficient synthesis of 99mTc-O-[3-(1,4,8,11-tetraazabicyclohexadecane)-propyl]-α-methyl tyrosine (99mTc-N4-AMT) and evaluate its potential in cancer imaging.

Methods.

N4-AMT was synthesized by reacting N4-oxalate and 3-bromopropyl AMT (N-BOC, ethyl ester).

In vitro cellular uptake kinetics of 99mTc-N4-AMT was assessed in rat mammary tumor cells.

Tissue distribution of the radiotracer was determined in normal rats at 0.5–4 h, while planar imaging was performed in mammary tumor-bearing rats at 30–120 min.

Results.

The total synthesis yield of N4-AMT was 14%.

Cellular uptake of 99mTc-N4-AMT was significantly higher than that of 99mTc-N4.

Planar imaging revealed that 99mTc-N4-AMT rendered greater tumor/muscle ratios than 99mTc-N4.

Conclusions.

N4-AMT could be synthesized with a considerably high yield.

Our in vitro and in vivo data suggest that 99mTc-N4-AMT, a novel amino acid-based radiotracer, efficiently enters breast cancer cells, effectively distinguishes mammary tumors from normal tissues, and thus holds the promise for breast cancer imaging.