68Ga-NK224 PET/CT for Noninvasive Evaluation of PD-L1 Expression and Intertumor Heterogeneity: A Translational Exploratory Study
Liang Zhao, Yizhen Pang, Yi Ding, Jianhao Chen, Jianyang Fang, Lingyu Yu, Dan Ruan, Yaqing Dai, Hui Zhou, Hao Fu, Wei Guo, Long Sun, Hua Wu, Shan Zhong, Qin Lin, Haojun Chen
Abstract
PURPOSE: This study developed 68Ga-NK224, a novel peptide-based radiotracer targeting human PD-L1, to evaluate the feasibility of 68Ga-NK224 PET/CT for assessing PD-L1 expression and tumor heterogeneity in a prospective investigator-initiated trial. EXPERIMENTAL DESIGN: In preclinical studies, NK224 was labeled with 68Ga. Small-animal PET, biodistribution, and blocking studies were performed using tumor models with varying PD-L1 expression levels to assess the targeting ability and specificity of 68Ga-NK224 in vivo. Serial 68Ga-NK224 PET assessed target occupancy following PD-L1 antibody administration. In the clinical study, 37 patients with non-small cell lung cancer who underwent 68Ga-NK224 PET/CT were prospectively recruited, with PD-L1 expression assessed via IHC and analyzed for correlation with 68Ga-NK224 uptake. RESULTS: Preclinical studies demonstrated that 68Ga-NK224 exhibited high tumor uptake and rapid clearance, producing favorable tumor-to-background contrast. In human CD34+ humanized mice, immunotherapy guided by 68Ga-NK224 PET/CT (once weekly) yielded similar antitumor effects as conventional dosing (three times weekly). Clinically, 68Ga-NK224 PET/CT was well tolerated, with no adverse events reported. Among the 31 patients who underwent paired 68Ga-NK224 and 2[18F]fluoro-2-deoxy-D-glucose PET/CT, the tumor uptake of 68Ga-NK224 significantly correlated with PD-L1 expression, whereas no correlation was found with 2[18F]fluoro-2-deoxy-D-glucose PET/CT. Additionally, 68Ga-NK224 demonstrated high heterogeneity across intrapatient lesions, with a median maximum standardized uptake value (SUVmax) coefficient of variation of 27.5% (range, 5.7%-53.2%). CONCLUSIONS: 68Ga-NK224 provides a straightforward radiolabeling approach with high tumor-to-background contrast, enabling an accurate assessment of PD-L1 expression and visualization of heterogeneity across intrapatient lesions. Its ability to dynamically monitor PD-L1 occupancy in tumors offers a novel method for optimizing immunotherapy dosing regimens.