Development And Preliminary Clinical Translation Of PD-L1 Targeted Molecular Probe For Tumor

Objective:The immunotherapy targeting the immune checkpoint of PD-1/PD-L1 plays a role in the continuous response of tumor treatment and significantly prolongs the progression free survival of patients.Studies have shown that the expression level of PD-L1 in patients is related to whether the patients can benefit from the PD-1/PD-L1 targeted immunotherapy.Therefore,it is crucial to evaluate the expression level of PD-L1 in patients accurately for the formulation of treatment plan.At present,PD-L1 is mainly analyzed in by immunohistochemistry,and the results are used to achieve screening and prediction of therapeutic effect of immunotherapy.However,the heterogeneity and dynamic change of PDL1 expression and limited samples harvesting limit the value of immunohistochemistry in the evaluation of PD-L1 expression.PET/CT molecular imaging,using the radiotracer which targets PD-L1 as the imaging agent,is expected to achieve noninvasive,visual,real-time and quantitative detection of PD-L1 in patients.Methods:WL12 was synthesized by chemical synthesis and coupled with p-SCN-BnNOTA to obtain the precursor of radiotracer NOTA-WL12.NOTA-WL12 was radiolabeled with 68Ga and 64Cu,respectively,to obtain the radiotracer with high specific activity and radiochemical purity.Then,the physicochemical properties of radiotracer were analyzed and the quality was controlled according to the "Regulations on the administration of the preparation of positron radiation drugs in medical institutions".After obtaining the qualified radiotracer,cell uptake,biodistribution and PET/CT imaging of models were carried out to study the detection ability of the radiotracer for PD-L1 expression.A total of 9 patients with NSCLC with different degrees of PD-L1 expression were recruited in the study of clinical transformation.All subjects underwent 68Ga-NOTA-WL12 and 18F-FDG PET/CT imaging.The data of 68Ga-NOTA-WL12 and 18F-FDG PET/CT imaging were processed and analyzed by Siemens post-processing workstation to study the distribution of radiotracer in vivo and the uptake of radiotracer in tumor lesions.The dosimetry received by the subjects for 68Ga-NOTA-WL12 PET/CT imaging was obtained by Olinda/EXM software.Results:the purity of WL12 and NOTA-WL12 was over 95%with strong affinity for PDL1.68Ga-NOTA-WL12 and 64Cu-NOTA-WL12 radiotracers have high specific activity,high radiochemical purity and good stability in vitro and in vivo.In cell uptake study,the uptake values of 68Ga-NOTA-WL12 and 64Cu-NOTA-WL12 radiotracers in PD-L1 postive cell were significantly higher than those in PD-L1 negative cell(P<0.001).In the study of PET/CT imaging,the mean standard uptake of tumor in CHOhPD-L1 model mice was significantly higher than that in CHO model mice(P<0.001),and the mean standard uptake of tumor lesions in CHO-hPD-L1 model mice with PD-L1 expression could be reduced by co-injection experiment(P<0.01).There was no significant difference in the mean standard uptake of tumor lesions between the experimental group and blocking group of CHO model mice.These results indicate that both 68Ga-NOTA-WL12 and 64Cu-NOTA-WL12 radiotracers can effectively evaluate the expression level of PD-L1 in cells and model mice.In the clinical transformation study,there were no drug-related side effects in the process of 68Ga-NOTA-WL12 and 18F-FDG PET/CT imaging and within two weeks after the examination.The dosimetry of 68Ga-NOTA-WL12 PET/CT was 1.85e-02±4.07e03msv/MBq,which was significantly lower than that of 18F-FDG PET/CT.68Ga-NOTA-WL12 PET/CT imaging studies showed that the radiotracer could significantly concentrate in PD-L1 positive tumors.Conclusion:we have completed the preparation,quality control,basic biological evaluation of 68Ga-NOTA-WL12 and 64Cu-NOTA-WL12 radiotracers,and preliminary clinical transformation of 68Ga-N1TA-WL12 radiotracer.These radiotracers have good stability,high radiochemical purity and high specific activity,and can effectively evaluate the expression level of PD-L1 in a short time.The results show that the radiotracers are expected to realize the visualization,non-invasive,real-time and quantitative detection of PD-L1 in patients,and ultimately achieve the purpose of screening patients and predicting curative effect.