Noninvasive evaluation of PD-L1 expression using Copper 64 labeled peptide WL12 by micro-PET imaging in Chinese hamster ovary cell tumor model

As an indicative biomarker for immunotherapy, PD-L1 plays an important role in the clinical decision-making of the immune checkpoint blockade therapy. PET imaging through radiotracer can real-timely, quantitatively, and non-invasively assess the expression of PD-L1 in tumors. Here, we reported a copper-64 radiolabeled NOTA-WL12, ⁶⁴Cu-NOTA-WL12, and preliminarily evaluated its application in non-invasively detecting the PD-L1 expression.⁶⁴Cu-NOTA-WL12 was produced with high radiochemical yield (>90%), radiochemical purity (>98%), and specific activity (20 MBq/nmol). ⁶⁴Cu-NOTA-WL12 showed high in vitro stability and high binding affinity to the PD-L1 (K_D ≈ 3.012 nM). The micro-positron emission tomography/computerized tomography (micro-PET/CT) imaging indicated that ⁶⁴Cu-NOTA-WL12 was specifically accumulated in the tumor with PD-L1 expression. All results demonstrated that ⁶⁴Cu-NOTA-WL12 holds great potential for noninvasive evaluation of PD-L1 expression levels.