Table 1.

Comparison of targeted arginine metabolism tracers.

Tracer	Organic Synthesis	Radiolabeling	Evaluation
(2S,4S)4-[18F]F PArg [32,33]	10 step, Configuration determination	2 step, yield < 6%	Targeting CAT transporters; PET imaging, MCF-7 (T/M = 6) and U87MG (T/M = 6) subcutaneous tumor, U87MG (T/B =1.5) and HS683 (T/B = 6.5) intracranial tumor, at 60 min p.i.
[18F]7	10 step, Configuration determination	2 step, yield = 8%	Targeting CAT, ASC, ASC2 transporters, PET imaging, MCF-7 Tumor (T/M = 4), intracranial tumor (T/B = 2) at 60 min p.i.
L2 [30]	3 step, Configuration determination	1 step, yield = 100%	Targeting y+ transporters, no PET Imaging
[18F]FPARG [31]	4 step, Configuration undetermined	5 step, yield = 15 ± 3%	No testing of transport mechanism, PET imaging, NCI-H460 Tumor (T/M = 2) at 60 min p.i.

CAT: Cationic amino acid transporter, p.i.: post injection, T/M: Tumor/Muscle, T/B: Tumor/Brain.