Development and Preclinical Evaluation ofGa-Labeled B7-H3-Specific Bicyclic Peptides as Immuno-PET Tracers for Oncology.

Source: PubMed, NCBI / U.S. National Library of Medicine

Journal of medicinal chemistryZhang Fengsheng, Li Jindian, Wang Dongliang, et al.Published 6/9/2026Last synced 6/10/2026Status: syncedPMID: 42263262DOI: 10.1021/acs.jmedchem.6c00961

B7-H3 (CD276) is an emerging target for cancer theranostics, highlighting the need for imaging probes capable of noninvasively quantifying B7-H3 expression in tumors. Here, we developed threeGa-labeled B7-H3-targeting bicyclic peptide tracers with different PEG linker lengths. All tracers showed high radiochemical purity (>96%), favorable in vitro stability, and rapid blood clearance. Among them, [Ga]Ga-B7H3-FZ1 exhibited the highest affinity (= 83.22 nM). Micro-PET/CT imaging demonstrated that tumor uptake of [Ga]Ga-B7H3-FZ1 correlated positively with B7-H3 expression across multiple tumor models. In H1299 tumors. B7-H3 overexpression increased uptake from 1.09 ± 0.18 to 3.50 ± 0.97%ID/g at 30 min postinjection, confirming target specificity. Biosafety studies indicated no obvious toxicity. These results support [Ga]Ga-B7H3-FZ1 as a promising PET tracer for noninvasive B7-H3 imaging.

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