First automatic radiosynthesis of 11C labeled Telmisartan using a multipurpose synthesizer for clinical research use

Telmisartan, a nonpeptide angiotensin II AT1 receptor antagonist, is an antihypertensive drug. Positron emission tomography (PET) imaging with [(11)C]Telmisartan is expected to provide information about the whole body pharmacokinetics of telmisartan as well as the transport function of hepatic OATP1B3. We developed a first automatic preparation system of [(11)C]Telmisartan to applicable clinical research using a new (11)C and (18)F multipurpose synthesizer.

Two milligrams of precursor (1) in 5 μl of 1 M KOH in 0.5 ml of dimethyl sulfoxide was reacted with [(11)C]CH(3)I for 5 min at 120°C. The resultant solution was hydrolyzed with 1 M NaOH at 100°C for 3 min. The neutralization was carried out with acetic acid, followed by purification with high-performance liquid chromatography. The desired radioactive fraction was collected and solvent was replaced by 10 ml saline containing 0.3 ml of EtOH and 0.5 ml of PEG400, and then passed through a sterile 0.22 μm filter (Millex-GV, Millipore) to a pyrogen-free vial as the final product.

The yield of [(11)C]Telmisartan for clinical research use was 16.8 ± 2.9% EOB as decay corrected (n = 8, mean ± SD) in 32-36 min. The radiochemical purity of [(11)C]Telmisartan was >97%, and specific activity was higher than 86.3 MBq/nmol.

We succeeded in the first synthesis of [(11)C]Telmisartan for clinical research use by appropriate quality tests.