Development and Preclinical Evaluation of (68)Ga-Labeled B7-H3-Specific Bicyclic Peptides as Immuno-PET Tracers for Oncology.
B7-H3-targeting bicyclic peptides just got a serious upgrade in imaging research. A group in Shanghai built three new 68Ga-labeled peptide tracers, aiming to nail down noninvasive, accurate detection of B7-H3 (CD276) in cancer models using PET/CT. This could be a big step for anyone working on targeted oncology research.
J Med Chem
by Zhang F, Li J, Wang D et al.
“Development and Preclinical Evaluation of (68)Ga-Labeled B7-H3-Specific Bicyclic Peptides as Immuno-PET Tracers for Oncology. Zhang F(1)(2)(3)(4)(5)(6), Li J(1)(7)(3)(4)(5)(6)(8)(9)(10), Wang D(1)(3)(4)(5)(6), Liu X(1)(3)(4)(5)(6), Pan X(1)(2)(3)(4)(5)(6), He S(1)(7)(3)(4)(5)(6), Zhang J(1)(7)(3)(4)(5)(6), Shen H(2)(6), Song S(1)(7)(3)(4)(5)(6). Author information: (1)Department of Nuclear Medicine, Fudan University Shanghai Cancer Center, Shanghai 200032, China. (2)Institute of Modern Physics, Fudan University, Shanghai 200433, China. (3)Center for Biomedical Imaging, Fudan University, Shanghai 200032, China. (4)Shanghai Engineering Research Center of Molecular Imaging Probes, Shanghai 200032, China. (5)Department of Nuclear Medicine, Shanghai Proton and Heavy Ion Center, Shanghai 200032, China. (6)Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai 200433, China. (7)Department of Oncology, Shanghai Medical College and Center for Biomedical Imaging, Fudan University, Shanghai 200032, China. (8)State Key Laboratory of Complex, Severe, and Rare Diseases, Beijing 102602, China. (9)State Key Laboratory of Oral Diseases, Sichuan 610041, China. (10)State Key Laboratory of Metabolic Dysregulation and Prevention and Treatment of Esophageal Cancer, Zhengzhou 450000, China. 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 three 68Ga-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, [68Ga]Ga-B7H3-FZ1 exhibited the highest affinity (KD = 83.22 nM). Micro-PET/CT imaging demonstrated that tumor uptake of [68Ga]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 [68Ga]Ga-B7H3-FZ1 as a promising PET tracer for noninvasive B7-H3 imaging.”
Why B7-H3? It's a checkpoint molecule popping up in a lot of tumors, making it a hot target for both therapy and diagnostics. But until now, researchers needed better tools to actually visualize how much B7-H3 is in a given tumor. That's where these new peptides come in.
Key takeaway: [68Ga]Ga-B7H3-FZ1, one of the three tracers, stood out. It showed the highest binding affinity (KD = 83 nM) and a strong correlation between tumor uptake and actual B7-H3 expression. The tracer worked across multiple tumor models, and in engineered H1299 tumors, higher B7-H3 meant higher uptake. No toxicity popped up in the biosafety studies.
Here’s what makes these peptides interesting for the research crowd:
All three tracers had high radiochemical purity (>96%) and held up in vitro
Fast blood clearance makes for cleaner imaging and less background
PEG linker length tuning lets researchers tweak pharmacokinetics for specific projects
Target specificity was confirmed in real tumor models, not just cell lines
No obvious toxicity at research doses
If your work touches B7-H3, immuno-PET, or peptide-based imaging, this is worth a look. Check out the peptide research index for related developments or use the research tools to plan out tracer reconstitution and handling.
The bottom line: B7-H3-specific bicyclic peptides are pushing noninvasive tumor imaging forward, opening up sharper, more tailored research in oncology.
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