FOLH1 and neoplasm: Among the tested compounds, three DUPA radioconjugates [99mTc][TcO]2–4, with 7 to 16 atom spacers, were found to target PSMA with nanomolar affinity and high specificity, also displaying high and persistent tumor uptake in vivo (average 9.8 ± 2.4% ID/g at 4 h p.i.) and little or no-accumulation in other tissues except the kidneys.