[68Ga]Ga-AUNP-12 PET imaging to assess the PD-L1 status in preclinical and first-in-human study

Abstract

Purpose: PD-L1 PET imaging, as a non-invasive procedure, can perform a real-time, dynamic and quantitative analysis of PD-L1 expression at tumor sites. In this study, we developed a novel peptide-based PET tracer, [⁶⁸ Ga]Ga-AUNP-12, for preclinical and first-of-its-kind imaging of PD-L1 expression in patients.

Methods: Radiosynthesis of [⁶⁸ Ga]Ga-AUNP-12 was conducted. Assays for cellular uptake and binding were conducted on the PANC02, CT26, and B16F10 cell lines. Preclinical models were used to investigate its biodistribution, imaging capacity, and pharmacokinetics. Furthermore, interferon-γ (IFN-γ) was used for development of an animal model with high PD-L1 expression for targeted PET imaging and efficacy evaluation of PD-L1 blocking therapy. In healthy volunteers and cancer patients, the PD-L1 imaging, radiation dosimetry, safety, and biodistribution were further evaluated.

Results: In vitro and in vivo animal studies showed that [⁶⁸ Ga]Ga-AUNP-12 PET imaging displayed a high specificity in evaluating PD-L1 expression. The radiochemical yield of [⁶⁸ Ga]Ga-AUNP-12 was 71.7 ± 8.2%. Additionally, its molar activity and radiochemical purity were satisfactory. The B16F10 tumor was visualized with the tumor uptake of 6.86 ± 0.71% ID/g and tumor-to-muscle ratio of 6.83 ± 0.36 at 60 min after [⁶⁸ Ga]Ga-AUNP-12 injection. Furthermore, [⁶⁸ Ga]Ga-AUNP-12 PET imaging could sensitively detect the PD-L1 dynamic changes in CT26 tumor xenograft models regulated by IFN-γ treatment, and correspondingly can effectively guide immunotherapy. Regarding radiation dosimetry, [⁶⁸ Ga]Ga-AUNP-12 is safe for human use. The first human study found that [⁶⁸ Ga]Ga-AUNP-12 can be rapidly cleared from blood and other nonspecific organs through the kidney excretion, leading to form a clear imaging contrast in the clinical framework. The specificity of [⁶⁸ Ga]Ga-AUNP-12 was validated and tumor uptake strongly correlated with the high PD-L1 expression in patients with lung adenocarcinoma and oesophageal squamous cell carcinoma (OSCC).

Conclusion: [⁶⁸ Ga]Ga-AUNP-12 was successfully developed as a PD-L1-specific PET imaging tracer in preclinical and first-in-human studies.

Keywords: Immune checkpoints; Immunotherapy; PD-1/PD-L1; PET/CT imaging.