Development of a Stable Peptide-Based PET Tracer for Detecting CD133-Expressing Cancer Cells

CD133 has been recognized as a prominent biomarker for cancer stem cells (CSCs), which promote tumor relapse and metastasis. Here, we developed a clinically relevant, stable, and peptide-based positron emission tomography (PET) tracer, [⁶⁴Cu]­CM-2, for mapping CD133 protein in several kinds of cancers. Through the incorporation of a 6-aminohexanoic acid (Ahx) into the N terminus of a CM peptide, we constructed a stable peptide tracer [⁶⁴Cu]­CM-2, which exhibited specific binding to CD133-positive CSCs in multiple preclinical tumor models. Both PET imaging and ex vivo biodistribution verified the superb performance of [⁶⁴Cu]­CM-2. Furthermore, the matched physical and biological half-life of [⁶⁴Cu]­CM-2 makes it a state-of-the-art PET tracer for CD133. Therefore, [⁶⁴Cu]­CM-2 PET may not only enable the longitudinal tracking of CD133 dynamics in the cancer stem cell niche but also provide a powerful and noninvasive imaging tool to track down CSCs in refractory cancers.