11C-ER176, a radioligand for 18-kDa translocator protein (TSPO), has adequate sensitivity to robustly image all three affinity genotypes in human brain

For positron emission tomography (PET) imaging of 18-kDa translocator protein (TSPO), a biomarker of neuroinflammation, most second-generation radioligands are sensitive to the single nucleotide polymorphism rs6971; however this is probably not the case for the prototypical agent (11)C-PK 11195, which has a relatively lower signal-to-noise ratio. We recently found that (11)C-ER176, a new analog of (11)C-(R)-PK 11195, showed little sensitivity to rs6971 when tested in vitro and had high specific binding in monkey brain. This study sought: 1) to determine whether the sensitivity of (11)C-ER176 in human subjects was similar to the low sensitivity measured in vitro, and 2) to measure the binding potential (BPND), the ratio of specific to nondisplaceable uptake, of (11)C-ER176 in human brain.