Simple automated radiosynthesis of 10-[11C]methoxy-20(S)-camptothecin and biodistribution in normal mice

10-[ 11 C]methoxy-20(S)-camptothecin was synthesized automatically. The radiochemical yield was 30%–50% (all calculated at EOB, n =20) with [ 11 C]methyl triflate as a methylating agent. The radiochemical purity was greater than 96%, and the specific activity was 8.72±2.18   GBq/μmoL at EOS . Biodistribution showed that 10-[ 11 C]methoxy-20(S)-camptothecin is characterized by quick clearance from the blood and by significant uptake in the liver (5.72±1.92% ID/g at 15   min), intestines (2.43±0.38% ID/g at 15   min), and kidney (1.57±0.85% ID/g at 15   min). Micro-PET imaging clearly showed high radioactivity accumulation in liver, intestines and bladder, indicating that the primary modes of excretion of the radiotracer are through the hepatobiliary system and, to a lesser extent, through the renal system.