GPC3 and neoplasm: Both probes retained nanomolar affinity (KD ≃ 10–30 nM) for recombinant GPC3 in vitro, but in mice bearing GPC3-positive A431 or HepG2 xenografts, 89Zr-ssHN3 cleared more rapidly from the blood and liver at 1 h post-injection, and ssHN3 achieved a ~7% IA/g tumor uptake versus ~5.7% IA/g for nHN3, yielding a tumor-to-liver ratio of 3.5 ± 0.5 (vs. 1.5 ± 0.5).