Preclinical and first-in-human evaluation of 18F-labeled D-peptide antagonist for PD-L1 status imaging with PET

Purpose: PD-L1 PET imaging allows for the whole body measuring its expression across primary and metastatic tumors and visualizing its spatiotemporal dynamics before, during, and after treatment. In this study, we reported a novel ¹⁸F-labeled D-peptide antagonist, ¹⁸F-NOTA-NF12, for PET imaging of PD-L1 status in preclinical and first-in-human studies.

Methods: Manual and automatic radiosynthesis of ¹⁸F-NOTA-NF12 was performed. Cell uptake and binding assays were completed in MC38, H1975, and A549 cell lines. The capacity for imaging of PD-L1 status, biodistribution, and pharmacokinetics were investigated in preclinical models. The PD-L1 status was verified by western blotting, immunohistochemistry/fluorescence, and flow cytometry. The safety, radiation dosimetry, biodistribution, and PD-L1 imaging potential were evaluated in healthy volunteers and patients.

Results: The radiosynthesis of ¹⁸F-NOTA-NF12 was achieved via manual and automatic methods with radiochemical yields of 41.7 ± 10.2 % and 70.6 ± 4.2 %, respectively. In vitro binding assays demonstrated high specificity and affinity with an IC₅₀ of 78.35 nM and K_D of 85.08 nM. The MC38 and H1975 tumors were clearly visualized with the optimized tumor-to-muscle ratios of 5.36 ± 1.17 and 7.13 ± 1.78 at 60 min after injection. Gemcitabine- and selumetinib-induced modulation of PD-L1 dynamics was monitored by ¹⁸F-NOTA-NF12. The tumor uptake correlated well with their PD-L1 expression. ¹⁸F-NOTA-NF12 exhibited renal excretion and rapid clearance from blood and other non-specific organs, contributing to high contrast imaging in the clinical time frame. In NSCLC and esophageal Cancer patients, the specificity of ¹⁸F-NOTA-NF12 for PD-L1 imaging was confirmed. The ¹⁸F-NOTA-NF12 PET/CT and ¹⁸F-FDG PET/CT had equivalent findings in patients with high PD-L1 expression.

Conclusion: ¹⁸F-NOTA-NF12 was developed successfully as a PD-L1-specific tracer with promising results in preclinical and first-in-human trials, which support the further validation of ¹⁸F-NOTA-NF12 for PET imaging of PD-L1 status in clinical settings.