68Ga/177Lu-labeled nectin4-targeted covalent bicyclic peptide: a novel nectin-4-targeted radioligands for theranostic of urothelial carcinoma

Nectin-4 is markedly overexpressed in urothelial carcinoma (UC) and represents a promising theranostic target for both radiotherapy and positron emission tomography (PET) imaging. The Food and Drug Administration (FDA)-approved Nectin-4-targeted drug, enfortumab vedotin, has demonstrated substantial efficacy in the treatment of UC. Developing a non-invasive quantitative detection technology based on positron emission tomography/computed tomography (PET/CT) imaging is crucial for accurately measuring Nectin-4 expression levels, facilitating precise patient selection, treatment stratification, and efficacy monitoring in UC. In the present study, a series of ⁶⁸Ga/¹⁷⁷Lu-labelled covalent bicyclic peptide (⁶⁸Ga/¹⁷⁷Lu-FZ-NRs) targeted Nectin-4 were constructed for PET/CT imaging and targeted radiotherapy based on a SuFEx-bio-orthogonal strategy. In vitro experiments demonstrated that ⁶⁸Ga/¹⁷⁷Lu-FZ-NRs exhibited high radiochemical purity, stability, and strong Nectin-4 affinity. MicroPET/CT imaging confirmed that covalent ⁶⁸Ga-FZ-NRs exhibited strong tumor enrichment, low off-target binding, and excellent tumor/muscle ratios (> 4.90 at 60 min), thus validating Nectin-4 as an effective imaging target. In terms of clinical translation, all the ⁶⁸Ga-FZ-NRs localized in a highly precise manner to lesions in UC patients. PET/CT-positive areas matched ¹⁸F-Fluorodeoxyglucose (¹⁸F-FDG) positioning and regions of high Nectin-4 expression in biopsied tissues. In terms of radiotherapy, covalent ¹⁷⁷Lu-FZ-NRs exhibited a significantly higher tumor uptake (an average increase of ~ 4-fold at 24 h) and retention (~ 4-fold longer, up to 48 h) than non-covalent ¹⁷⁷Lu-FZ-NR-1, thus enhancing therapeutic effects. In treatment experiments, covalent ¹⁷⁷Lu-FZ-NRs strongly inhibited tumor growth without obvious toxicity. In summary, our novel Nectin-4-targeted covalent bicyclic peptide radioligands provide new molecular imaging tools for the non-invasive assessment of Nectin-4 and establish a foundation for UC-targeted radiotherapy.