EDB-FN targeted probes for the surgical navigation, radionuclide imaging, and therapy of thyroid cancer

Extradomain B of fibronectin (EDB-FN) is a promising diagnostic and therapeutic biomarker for thyroid cancer (TC). Here, we identified a high-affinity EDB-FN targeted peptide named EDBp (AVRTSAD) and developed three EDBp-based probes, Cy5-PEG4-EDBp(Cy5-EDBp), [¹⁸F]-NOTA-PEG4-EDBp([¹⁸F]-EDBp), and [¹⁷⁷Lu]-DOTA-PEG4-EDBp ([¹⁷⁷Lu]-EDBp), for the surgical navigation, radionuclide imaging, and therapy of TC.

Based on the previously identified EDB-FN targeted peptide ZD2, the optimized EDB-FN targeted peptide EDBp was identified by using the alanine scan strategy. Three EDBp-based probes, Cy5-EDBp, [¹⁸F]-EDBp, and [¹⁷⁷Lu]-EDBp, were developed for fluorescence imaging, positron emission tomography (PET) imaging, and radiotherapy in TC tumor-bearing mice, respectively. Additionally, [¹⁸F]-EDBp was evaluated in two TC patients.

The binding affinity of EDBp to the EDB fragment protein (Kd = 14.4 ± 1.4 nM, n = 3) was approximately 336-fold greater than that of the ZD2 (Kd = 4839.7 ± 361.7 nM, n = 3). Fluorescence imaging with Cy5-EDBp facilitated the complete removal of TC tumors. [¹⁸F]-EDBp PET imaging clearly delineated TC tumors, with high tumor uptake (16.43 ± 1.008%ID/g, n = 6, at 1-h postinjection). Radiotherapy with [¹⁷⁷Lu]-EDBp inhibited tumor growth and prolonged survival in TC tumor-bearing mice (survival time of different treatment groups: saline vs. EDBp vs. ABRAXANE vs. [¹⁷⁷Lu]-EDBp = 8.00 d vs. 8.00 d vs. 11.67 d vs. 22.33 d, ***p < 0.001). Importantly, the first-in-human evaluation of [¹⁸F]-EDBp demonstrated that it had specific targeting properties (SUVmax value of 3.6) and safety.

Cy5-EDBp, [¹⁸F]-EDBp, and [¹⁷⁷Lu]-EDBp are promising candidates for the surgical navigation, radionuclide imaging, and radionuclide therapy of TC, respectively.