Fully automated production of 11C-doxepin for PET imaging histamine H1 receptor.
OBJECTIVE
(11)C-Doxepin is an established positron emission tomography (PET) probe for imaging the histamine H1 receptor, which is associated with various neurological disorders and allergic diseases. A fully automated current Good Manufacturing Practices (cGMP)-compliant radiosynthesis is therefore desirable in order to facilitate clinical PET studies. We report here a fully automated production method for (11)C-doxepin using a multipurpose PET module for clinical use.


METHODS
(11)C-Doxepin was radiosynthesized by N-[(11)C]methylation of nordoxepin using [(11)C]methyl iodide in DMF solvent, and then purified by HPLC, and finally reformulated with solid phase extraction (SPE) using a cGMP-compliant automated multipurpose PET module developed in house. The final product was analyzed and subjected to quality control according to current US Pharmacopeia requirements.


RESULTS
The radiochemical yield (decay corrected) of (11)C-doxepin for clinical use was 47.0 ± 5.2% (n = 12) based on [(11)C]methyl iodide, moreover the radiochemical purity of (11)C-doxepin was more than 97.5% with 1,200 ± 500 Ci/mmol specific activity(end of production). The total production time of (11)C-doxepin was 37 min from end of bombardment (EOB) with the final product passing all tests under cGMP requirements for clinical use.


CONCLUSIONS
A simplified and reliable fully automated production of (11) C-doxepin for clinical use was developed, allowing the synthesis of the tracer with high yield using a cGMP-compliant module and procedure. The success of this approach could make the PET tracer (11) C-doxepin more accessible for clinical studies.
PET Center, Children's Hospital of Michigan/Detroit Medical Center, 3901 Beaubien Boulevard, Detroit, MI 48201, USA. hcai@dmc.org
Hancheng
H
Cai
Thomas J
TJ
Mangner
Otto
O
Muzik
Xin
X
Lu
Pulak K
PK
Chakraborty
Diane C
DC
Chugani
Harry T
HT
Chugani
D001331:Automation; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004316:Doxepin / Q000138:chemical synthesis* / Q000737:chemistry; D006801:Humans; D049268:Positron-Emission Tomography / Q000379:methods*; D011786:Quality Control; D011969:Receptors, Histamine H1 / Q000378:metabolism*
D002250:Carbon Radioisotopes; D011969:Receptors, Histamine H1; D004316:Doxepin