Synthesis and Preclinical Evaluation of the Fibrin-Binding Cyclic Peptide ¹⁸F-iCREKA: Comparison with Its Contrasted Linear Peptide

Figure 1

Schematic diagram of the iCREKA. ① The iCREKA reached at the tumor through the bloodstream based on the targeting ability of CREKA for fibrin-fibronectin complexes. ② The iCREKA was bound to the fibrin-fibronectin complexes. ③ While the cleavage sites PLGLAG remained intact, the iCREKA could not enter into tumor cells. In the MMP-2/9 highly expressed tumor, the cleavage sites PLGLAG were cut into two fragments by MMP-2/9. ④ One of the postcleavage fragments was composed of CCP (CRRRQRRKKR) and the residual cleavage sites GAL. This fragment could be endocytosed by the tumor cells.