Preclinical and exploratory human studies of novel 68Ga-labeled D-peptide antagonist for PET imaging of TIGIT expression in cancers

Abstract

Purpose While TIGIT has been propelled as a next-generation target in cancer immunotherapy, anti-TIGIT therapy seems to be promising for a fraction of patients in clinical trials. Therefore, patient stratification is critical for this therapy, which could benefit from a whole-body, non-invasive, and quantitative evaluation of TIGIT expression in cancers. In this study, a 68 Ga-labeled D-peptide antagonist, 68 Ga-GP12, was developed and validated for PET imaging of TIGIT expression in vitro, in vivo , and in an exploratory human study. Methods The D-enantiomer peptide antagonists were modified and radiolabeled with 68 Ga. In vitro binding assays were performed in human peripheral blood mononuclear cells (PBMCs) to assess their affinity and specificity. The imaging capacity, biodistribution, pharmacokinetics, and radiation dosimetry were investigated. Flow cytometry, autoradiography, and immunohistochemical staining were used to confirm the expression of TIGIT. The safety and potential of 68 Ga-GP12 for PET/CT imaging of TIGIT expression were evaluated in NSCLC patients. Results 68 Ga-labeled D-peptides were conveniently produced with high radiochemical yields, radiochemical purities and molar activities. In vitro binding assays demonstrated 68 Ga-GP12 has high affinity and specificity for TIGIT with a K D of 37.28 nM. In vivo and ex vivo studies demonstrated the capacity of 68 Ga-GP12 for PET imaging of TIGIT expression with high tumor uptake of 4.22 ± 0.68 %ID/g and the tumor-to-muscle ratio of 12.94 ± 2.64 at 60 min post-injection. In NSCLC patients, primary and metastatic lesions found in 68 Ga-GP12 PET images were comparable to that in 18 F-FDG PET images. Moreover, tracer uptake in primary and metastatic lesions and intra-tumoral distribution in the large tumor were inhomogenous, indicating the heterogeneity of TIGIT expression. Conclusion 68 Ga-GP12 is a promising radiotracer for PET imaging of TIGIT expression in cancers , indicating its potential as a potential companion diagnostic for anti-TIGIT therapies. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s00259-021-05672-x.

Molecular imaging to support cancer immunotherapy

“…30 A gallium-68 labeled peptide targeting TIGIT ([ 68 Ga]Ga-GP12) has been evaluated for PET imaging of TIGIT. 31 PET imaging in a tumor-bearing mouse model revealed optimal tumorto-muscle ratio 60 min after tracer injection. Pretreatment with excess GP12 reduced the PET signal, whereas pretreatment with an anti-TIGIT monoclonal antibody did not, indicating binding to another epitope.…”

Current state and upcoming opportunities for immunoPET biomarkers in lung cancer

“…Shaffer et al (2021) have developed 64 Cu-TIGITmAb and 89 Zr-TIGITmAb to visualize TIGIT expression in murine models [41]. Additionally, Wang et al ( 2022) have used 68 Ga-GP12 to visualize TIGIT expression and evaluate safety in mouse models and two NSCLC patients [42]. Both studies showed higher tracer uptake in tumor lesions as compared to healthy organs.…”

Positron Emission Tomography Probes for Imaging Cytotoxic Immune Cells

“…In recent years, the commercial availability of more suitable chelators, such as NOTA and (Tris(hydroxypyridinone) (THP), allow 68 Ga labelling to be performed under milder conditions (37–60 °C). Typically, 68 Ga labelling for immune response are almost exclusively paired with these two chelators [ 113 , 117 , 118 , 119 ].…”

“…Another inhibitory immune checkpoint molecule, TIGIT, is also an interesting target for PET imaging. Additionally, [ 68 Ga]Ga-NOTA-GP12, a peptide antagonist for TIGIT, was demonstrated to be safe and able to image TIGIT expression in murine models and two patients with advanced NSCLC [ 117 ]. Nevertheless, further clinical evaluation is necessary to determine its potential value in predicting and monitoring response to ICIs.…”