Estimating Human Organ Dose of [68Ga]Ga-αMSH Derivative: High Potential Agent for PET Imaging of Patients with Melanoma Cancer

This research was conducted with the aim of estimating the human absorbed dose of [68Ga]Ga-α-melanocyte-stimulating hormone ([68Ga]Ga-αMSH), a new agent for positron emission tomography (PET) imaging of melanoma cancer. 68Ga was eluted from an in-house developed 68Ge/68Ga generator in the form of [68Ga]GaCl3. αMSH was labeled with 68Ga under optimized conditions by adjusting various parameters that affect the peptide labeling process. The radiochemical purity (RCP) of the radiotracer was assessed using radio thin layer chromatography/high-performance liquid chromatography (RTLC/HPLC). The stability of the complex in human serum and PBS buffer was monitored for up to 2 h post-incubation. The biodistribution of the radiolabeled peptide was studied in tumor-bearing C57 mice. Medical Internal Radiation Dose (MIRD) and mass extrapolation methods were utilized to estimate the absorbed dose of human organs. [68Ga]Ga-αMSH was prepared with RCP>99% and a specific activity> 118 GBq/µmol. The radiolabeled peptide is stable in human serum and PBS buffer. Biodistribution studies in tumor-bearing mice revealed that majority of activity remained in the animal’s body was accumulated at the tumor site. Estimations of absorbed doses in human organs indicated that the kidneys received the highest dose (0.055 mGy/MBq) due to their high uptake and route of activity excretion. The equivalent dose for humans following injection of the [68Ga]Ga-αMSH complex was estimated to be 0.011 mGy/MBq. The results showed that [68Ga]Ga-αMSH has a high potential as a PET imaging agent in melanoma cancer patients. It is considered safe compared to other radiotracers used in clinical studies.