Preclinical and first-in-human evaluation of [68Ga]Ga-DOTA-PEG2-Asp2-PDL1P PET imaging to assess tumor PD-L1 expression

Purpose: PD-L1 PET imaging can provide a non-invasively and real-time assessment of PD-L1 expression status at tumor sites. This study aimed to evaluate the targeting efficacy and biodistribution of a novel peptide-based PD-L1 PET agent, [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P, in preclinical studies and human participants. Methods: [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P was synthesized and the probe stability was analyzed in vitro and in vivo. Cellular uptake of the probe was evaluated using tumor cell lines with different PD-L1 expression levels. Small animal PET imaging and semi-quantitative studies were conducted in PC3, H1975 and A549 tumor-bearing mice models, with tumor PD-L1 expression confirmed through immunofluorescence and immunohistochemistry. Furthermore, [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P PET imaging was performed in 1 healthy volunteer and 14 lung cancer patients to assess biodistribution and PD-L1 expression at tumor sites. Results: [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P exhibited a radiochemical purity of > 99% and had good stability both in vitro and in vivo. In vitro cellular uptake and in vivo small animal PET imaging revealed the probe binding to PD-L1 with high affinity and specificity, consistent with the results of immunofluorescence and immunohistochemistry. In the clinical study involving 15 participants, [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P was proven safe with demonstrating low uptake in normal organs and physiologically excreting via the urinary system. Lung cancer patients with high PD-L1 expression (TPS 70-90%) exhibited higher tumor uptake and tumor-to-background ratios than those with negative or low PD-L1 expression (TPS < 1-10%), with SUVmax of 1.89-2.27 vs. 0.87-1.01, tumor-to-lung ratios of 4.73-7.68 vs. 1.61-2.35, and tumor-to-muscle ratios of 6.73-12.61 vs. 4.35-5.61. Conclusion: [Ga-68]Ga-DOTA-PEG(2)-Asp(2)-PDL1P showed promising as a PET agent to assess tumor PD-L1 expression in preclinical and first-in-human studies, offering a non-invasive, real-time and accurate tool to address clinical challenges in predicting and assessing the efficacy of immunotherapy.