De novo discovery and preclinical evaluation of a novel peptide radiotracer for PET imaging of TROP-2 in non-small cell lung cancer.

Trophoblast cell surface antigen 2 (TROP-2) is frequently overexpressed in non-small cell lung cancer (NSCLC), particularly in lung adenocarcinoma (LUAD), making it a promising target for the diagnosis and treatment of this malignancy. In this study, we performed the de novo design and preclinical evaluation of a novel TROP-2-targeted peptide-based positron emission tomography (PET) probe, designated NOTA-PEG4-RS15, which was derived from IGF-1, the natural ligand of TROP-2. The probe exhibited nanomolar affinity (Kd = 238.60 nM), along with high radiochemical yield, excellent stability, and favorable pharmacokinetic characteristics. In vitro studies revealed significant uptake of [Ga]Ga-NOTA-PEG4-RS15 in TROP-2-positive Calu-3 cells and patient-derived primary lung adenocarcinoma cells, accompanied by high binding specificity validated using TROP-2-negative A549 cells as a contrast. In vivo studies conducted in subcutaneous xenograft models (Calu-3 and A549) and patient-derived xenograft (PDX) models demonstrated marked tracer accumulation in TROP-2-high tumors, with quantitative data showing a tumor uptake of 4.63 ± 0.32 %ID/g and a tumor-to-muscle (T/M) ratio of 4.04 ± 0.85. In contrast, TROP-2-low models exhibited weak tracer uptake signals, yielding clear image contrast. In conclusion, [Ga]Ga-NOTA-PEG4-RS15 emerges as a promising TROP-2-targeted peptide-based PET probe, characterized by high specificity, robust imaging contrast, and notable translational potential. This probe may be a valuable tool for precision molecular imaging of TROP-2-positive NSCLC.