Development and First-in-Human evaluation of a Site-Specific [18F]-Labeled PD-L1 nanobody PET radiotracer for noninvasive imaging in NSCLC

• Published in: Bioorganic chemistry Vol. 156; p. 108222
• Main Authors: Ma, Xiaopan, Hu, Biao, Zhou, Xin, Wang, Lei, Chen, Hui, Xie, Fei, Zhu, Hua, Jia, Bing, Yang, Zhi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2025
• Subjects: Animals; B7-H1 Antigen - metabolism; Carcinoma, Non-Small-Cell Lung - diagnostic imaging; Carcinoma, Non-Small-Cell Lung - metabolism; Dose-Response Relationship, Drug; Female; Fluorine Radioisotopes - chemistry; Humans; Lung Neoplasms - diagnostic imaging; Mice; Mice, Nude; Molecular Structure; Nanobody; Neoplasms, Experimental - diagnostic imaging; NSCLC; PD-L1; PET/CT; Positron Emission Tomography Computed Tomography; Positron-Emission Tomography; Radiopharmaceuticals - chemistry; RESCA; Single-Domain Antibodies - chemistry; Tissue Distribution; PD-L1; Nanobody; RESCA; NSCLC; PET/CT
• ISSN: 0045-2068; 1090-2120
• DOI: 10.1016/j.bioorg.2025.108222

We have successfully developed a new PD-L1-targeted nanobody PET tracer using the site-specific labeling method with the complexing agent (Mal-RESCA) within 20 min under mild conditions. [18F]AlF-APN09 is a promising noninvasive PET radiotracer for visualizing PD-L1 expression in PD-L1-positive tumors (A549PD−L1 and H1975) in mice models with high signal-to-noise ratios. Tumor uptake of a single resectable non-small cell lung cancer (NSCLC) subject reached SUVmax 4.20 at 2 h after injection of [18F]AlF-APN09 with high contrast and rapid clearance. [Display omitted] •A new PD-L1-targeted nanobody-based radiotracer [18F]AlF-APN09 was developed within 20 min under mild conditions.•[18F]AlF-APN09 can be obtained with satisfactory radiochemical yields and high radiochemical purity.•[18F]AlF-APN09 clearly visualized PD-L1-positive tumors (A549PD−L1 and H1975) in mouse models with high signal-to-noise ratios.•First-in-human imaging was performed on a single resectable NSCLC subject with high contrast and rapid clearance. Immunohistochemistry (IHC) for PD-L1 detection is limited by its invasiveness and heterogeneity of tumors. To address these challenges, a new PD-L1-targeted nanobody-based immune-PET radiotracer [18F]AlF-APN09 was developed using the site-specific radiolabeling method with the complexing agent (Mal-RESCA) under mild conditions. [18F]AlF-APN09 was prepared at room temperature (pH 4.6–4.8) within 20 min with satisfactory radiochemical yields (45.8 ± 4.48 %, non-decay corrected), high radiochemical purity (>98 %) and moderate apparent molar activity (15–35 GBq/μmol), and remained stable in both PBS and 5 % HSA after 4 h (>90 %). Cell uptake studies indicated variable levels of surface PD-L1 expression in the following order: A549PD−L1 > H1975 > A549. In micro-PET/CT imaging, A549PD−L1 and H1975 tumors were distinctly visualized in a 6.0:1 and 3.2:1 ratios over PD-L1-negative A549 tumors in vivo. Ex vivo biodistribution studies showed tumor uptake values of 6.47 ± 1.06 %ID/g (A549PD−L1) and 2.27 ± 0.19 %ID/g (H1975), significantly higher than 0.90 ± 0.28 %ID/g in A549 tumors. The estimated effective radiation dose in humans was 8.65E-03 mSv/MBq, lower than that of conventional [18F]FDG. First-in-human imaging was conducted on a single resectable non-small cell lung cancer (NSCLC) subject without any adverse reactions. The radiotracer exhibited renal excretion with minimal hepatobiliary clearance. Tumor uptake reached SUVmax 4.20 at 2 h post-injection, demonstrating high contrast and rapid clearance. After PD-1 inhibitor immunotherapy and chemotherapy, the subject showed a therapeutic response and postoperative pathological specimens confirmed a major pathological response (MPR). These results suggest that we have successfully developed a new PD-L1-targeted nanobody PET tracer using the site-specific labeling method with the complexing agent (Mal-RESCA) within 20 min under mild conditions and [18F]AlF-APN09 is a promising noninvasive PET radiotracer for visualizing PD-L1 expression in tumors, offering rapid tumor targeting, excellent signal-to-noise ratios, and favorable clearance properties.