TY - JOUR T1 - Initial Evaluation of <sup>11</sup>C-DPA-713, a Novel TSPO PET Ligand, in Humans JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1276 LP - 1282 DO - 10.2967/jnumed.109.062265 VL - 50 IS - 8 AU - Christopher J. Endres AU - Martin G. Pomper AU - Michelle James AU - Ovsev Uzuner AU - Dima A. Hammoud AU - Crystal C. Watkins AU - Aaron Reynolds AU - John Hilton AU - Robert F. Dannals AU - Michael Kassiou Y1 - 2009/08/01 UR - http://jnm.snmjournals.org/content/50/8/1276.abstract N2 - Translocator protein (TSPO) is upregulated in activated microglia and thus can serve as a marker of neuroinflammation. Recently, a novel radioligand, 11C-N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide (11C-DPA-713), has been described that binds to TSPO with high affinity. Here, we report the first examination of 11C-DPA-713 in human subjects using PET. Methods: Five healthy controls were studied with PET for 90 min after a bolus injection of high-specific-activity 11C-DPA-713. For comparison, 2 additional healthy controls were studied with 11C-R-PK11195. Arterial blood sampling and metabolite analysis were performed to allow the accurate quantification of tracer kinetics. Tracer uptake was evaluated for several brain regions. Tissue time–activity curves were fitted using 1- and 2-tissue-compartment models, with goodness-of-fit tests showing a preference for the 2-tissue model. Results: In the healthy brain, the average plasma-to-tissue clearance and the total volume of distribution were an order of magnitude larger than measured for 11C-R-PK11195. Accordingly, dose-normalized time–activity curves showed that 11C-DPA-713 gives a larger brain signal. Conclusion: Studies in patient populations will help determine whether 11C-DPA-713 provides better sensitivity for evaluating increased TSPO expression. This initial study in humans shows that 11C-DPA-713 is a promising ligand for evaluating TSPO binding with PET. ER -