Synthesis and Biological Evaluation of (<i>S</i>)‑Amino-2-methyl-4‑[⁷⁶Br]bromo-3‑(<i>E</i>)‑butenoic Acid (BrVAIB) for Brain Tumor Imaging

The novel compound, (S)-amino-2-methyl-4-[76Br]bromo-3-(E)-butenoic acid (BrVAIB, [76Br]5), was characterized against the known system A tracer, IVAIB ([123I]8). [76Br]5 was prepared in a 51% ± 19% radiochemical yield with high radiochemical purity (≥98%). The biological properties of [76Br]5 were compared with those of [123I]8. Results showed that [76Br]5 undergoes mixed amino acid transport by system A and system L transport, while [123I]8 had less uptake by system L. [76Br]5 demonstrated higher uptake than [123I]8 in DBT tumors 1 h after injection (3.7 ± 0.4% ID/g vs 1.5 ± 0.3% ID/g) and also showed higher uptake vs [123I]8 in normal brain. Small animal PET studies with [76Br]5 demonstrated good tumor visualization of intracranial DBTs up to 24 h with clearance from normal tissues. These results indicate that [76Br]5 is a promising PET tracer for brain tumor imaging and lead compound for a mixed system A and system L transport substrate.