Effective synthesis of Pittsburg Compound B (¹¹C-PIB) for clinical application by on-column ¹¹C-methylation

Objectives The Pittsburg Compound B (¹¹C-PIB) is a radiotracer for imaging amyloid plaques in Alzheimer’s disease by PET. The aim of this study was to develop an efficient fully automated synthesis method to achieve a high radiochemical yield of ¹¹C-PIB with small amount of precursor based on the “on-column method".

Methods ¹¹C-Methyl triflate (¹¹C-MeOTf) passed through the column, which contained 1 mg of precursor, 6-OH-BTA-0 in Methylethylketone. After on-column ¹¹C-methylation using ¹¹C-MeOTf, ¹¹C-PIB was eluted with organic solvent. The solution was transferred into the reservoir and then injected onto the HPLC column. The peak corresponding to ¹¹C-PIB was transferred into a rotary evaporator flask. The solvent was removed in vacuo, and the residue was dissolved in saline, and then passed through a sterile filter to give the ¹¹C-PIB injection.

Results This method produced ¹¹C-PIB in less than 40 min after end of bombardment, with a 10% radiochemical yield, a 17-21 MBq/nmol specific activity and a high radiochemical purity (>99%).

Conclusions This synthesis method, achieving a high radiochemical yield with a small amount of precursor, is promising for the routine production of ¹¹C-PIB, and gives shortening of the preparations time as compared with conventional methods.