Novel Receptor-Targeted Fluorescent Contrast Agents for In Vivo Tumor Imaging

Achilefu S, Dorshow RB, Bugaj JE, Rajagopalan R. Novel receptor-targeted fluorescent contrast agents for in vivo tumor imaging. Invest Radiol 2000;35:479–485. RATIONALE AND OBJECTIVES.To evaluate the efficacy of a novel tumor receptor-specific small-peptide–near-infrared dye conjugate for tumor detection by optical imaging. METHODS.A novel, near-infrared dye-peptide conjugate was synthesized and evaluated for tumor-targeting efficacy in a well-characterized rat tumor model (CA20948) known to express receptors for the chosen peptide. A simple continuous-wave optical imaging system, consisting of a near-infrared laser diode, a cooled CCD camera, and an interference filter, was used in this study. RESULTS.Tumor retention of two non–tumor-specific dyes, indocyanine green and its derivatized analogue, bis-propanoic acid cyanine dye (cypate), was negligible. In contrast, the receptor-specific peptide-cypate conjugate (cytate) was retained in the CA20948 tumor, with an excellent tumor-to-normal-tissue ratio in the six rats examined. CONCLUSIONS.Optical detection of tumors with a receptor-targeted fluorescent contrast agent has been demonstrated. This result represents a new direction in cancer diagnosis and patient management.