Synthesis and evaluation of ¹⁸F-labeled procainamide as a PET imaging agent for malignant melanoma

Malignant melanoma has an aggressive nature and a high metastatic propensity resulting in the highest mortality rate of any skin cancer. In this study, we synthesized ¹⁸F-labeled procainamide (PCA) for detection of melanoma using positron emission tomography (PET), and evaluated its biological characteristics. The non-decay-corrected radiochemical yield of ¹⁸F-PCA was 10-15% and its in vitro stability was over 98% for 2 h. At 1 h, cellular uptake of ¹⁸F-PCA was 3.8-fold higher in a group with the presence of l-tyrosine than in a non-l-tyrosine-treated group. Furthermore, ¹⁸F-PCA permitted visualization of B16F10 (mouse melanoma) xenografts on microPET after intravenous injection, and was retained in the tumor for 60 min, with a high tumor-to-liver uptake ratio. ¹⁸F-PCA showed specific melanoma uptake in primary lesions with a high melanin targeting ability in small animal models. ¹⁸F-PCA may have potential as a PET imaging agent for direct melanoma detection.