Pilot Study of Nectin-4–Targeted PET Imaging Agent⁶⁸Ga-FZ-NR-1 in Triple-Negative Breast Cancer from Bench to First-in-Human

Nectin cell adhesion molecule 4 (Nectin-4) is an emerging biomarker for cancer diagnosis and therapy. We developed a Nectin-4-targeted ⁶⁸Ga-DOTA-Sar10-Nectin-4 (⁶⁸Ga-FZ-NR-1) PET/CT radiotracer for detecting Nectin-4 expression in a tumor model and in triple-negative breast cancer (TNBC) patients. <b>Methods:</b> A series of Nectin-4-targeted radiotracers-⁶⁸Ga-FZ-NR-1, ⁶⁸Ga-DOTA-polyethylene glycol 5-Nectin-4 (⁶⁸Ga-FZ-NR-2), and ⁶⁸Ga-DOTA-polyethylene glycol 10-Nectin-4 (⁶⁸Ga-FZ-NR-3)-were synthesized, and their targeting ability and specificity were evaluated in vitro and in vivo. In vitro experiments were performed in the MDA-MB-468 (Nectin-4-positive) and MDA-MB-231 (Nectin-4-negative) cell lines. PET/CT imaging in tumor models was performed to assess the Nectin-4-targeting ability of the radiotracers. After preclinical experiments and screening, the ⁶⁸Ga-FZ-NR-1 radiotracer was selected for safety and efficacy evaluation in a first-in-human trial in TNBC patients. Positive lesions were biopsied and analyzed by immunohistochemistry to determine Nectin-4 expression levels. <b>Results:</b> The 3 ⁶⁸Ga-labeled radiotracers exhibited high radiochemical purity, stability, and strong affinity for Nectin-4. In vitro cell uptake studies showed that the radiotracers effectively targeted Nectin-4 in MDA-MB-468 cells, and ⁶⁸Ga-FZ-NR-1 showed the highest targeting efficacy. In the MDA-MB-468 tumor model, PET/CT imaging showed that ⁶⁸Ga-FZ-NR-1 was taken up at higher rates than ⁶⁸Ga-FZ-NR-2 and ⁶⁸Ga-FZ-NR-3, and it exhibited favorable pharmacokinetics and safety profiles. ⁶⁸Ga-FZ-NR-1 was thus selected for subsequent clinical trials. ⁶⁸Ga-FZ-NR-1 PET/CT effectively identified tumors in 9 patients with TNBC, which was confirmed by ¹⁸F-FDG PET/CT. Biopsy samples of the tumor lesions revealed that the positive lesions identified by ⁶⁸Ga-FZ-NR-1 PET/CT corresponded to areas of high Nectin-4 expression. <b>Conclusion:</b> A series of Nectin-4-targeted radiotracers (⁶⁸Ga-FZ-NR-1, ⁶⁸Ga-FZ-NR-2, and ⁶⁸Ga-FZ-NR-3) was developed and evaluated. Preclinical studies demonstrated that ⁶⁸Ga-FZ-NR-1 can identify tumors with high Nectin-4 expression. In a preliminary clinical study, ⁶⁸Ga-FZ-NR-1 was used to effectively identify and visualize Nectin-4-expressing tumor lesions in patients with TNBC, which was confirmed by immunohistochemistry. This radiotracer provides a noninvasive approach to the assessment of Nectin-4 and a potential basis for the development of Nectin-4-targeted treatments for TNBC.