Towards to hENT1-nucleoside transporter selective imaging agents. Synthesis and in vitro evaluation of the radiolabeled SAENTA analogues

Three new potential hENT₁ inhibitors suitable for labeling with PET/SPECT radioisotopes were prepared from an advanced intermediate 4. They were tested for their capability to inhibit binding of SAENTA-fluorescein to HL60 leukemia cells in flow cytometry assay and SAENTA-I (5) was determined to be the most active compound. ¹³¹I-5 showed high hENT₁-specific binding (up to 54% ID) to 6 from 7 tested tumor cell lines and was chosen for further in vivo study.