Preliminary results showed that the distribution patterns of R(1) and pAV-45 images are highly correlated with normalized FDG images, and the initial 5-min early time frame of 1-6 min is potentially useful in providing complementary FDG-like information to the amyloid plaque density by late-phase AV-45 images.

50% of patients with HRD respond to PARPi therapy (3). Moreover, patients without known HRD have also shown a clinical benefit from PARPis, as seen in recent trials assessing niraparib, olaparib, or rucaparib, as maintenance therapy in platinum-sensitive recurrent ovarian cancer (5-8). Given that not all patients will respond to PARPi therapy, improved clinical tools for predicting which patients will respond are urgently needed.Numerous clinical trials have led to FDA approval of 3 PARPis since 2014 and there is continued development of 2 additional drugs within this class (9-13). Despite growth in the BACKGROUND. Poly(ADP-ribose) polymerase (PARP) inhibitors are effective in a broad population of patients with ovarian cancer; however, resistance caused by low enzyme expression of the drug target PARP-1 remains to be clinically evaluated in this context. We hypothesize that PARP-1 expression is variable in ovarian cancer and can be quantified in primary and metastatic disease using a novel PET imaging agent. METHODS.We used a translational approach to describe the significance of PET imaging of PARP-1 in ovarian cancer. First, we produced PARP1-KO ovarian cancer cell lines using CRISPR/Cas9 gene editing to test the loss of PARP-1 as a resistance mechanism to all clinically used PARP inhibitors. Next, we performed preclinical microPET imaging studies using ovarian cancer patient-derived xenografts in mouse models. Finally, in a phase I PET imaging clinical trial we explored PET imaging as a regional marker of PARP-1 expression in primary and metastatic disease through correlative tissue histology. RESULTS.We found that deletion of PARP1 causes resistance to all PARP inhibitors in vitro, and microPET imaging provides proof of concept as an approach to quantify PARP-1 in vivo. Clinically, we observed a spectrum of standard uptake values (SUVs) ranging from 2-12 for PARP-1 in tumors. In addition, we found a positive correlation between PET SUVs and fluorescent immunohistochemistry for PARP-1 (r 2 = 0.60).CONCLUSION. This work confirms the translational potential of a PARP-1 PET imaging agent and supports future clinical trials to test PARP-1 expression as a method to stratify patients for PARP inhibitor therapy.TRIAL REGISTRATION. Clinicaltrials.gov NCT02637934. 22-24). Furthermore, PARP-1 has been development and application of PARPis, the primary drug target poly(ADP-ribose) polymerase 1 (PARP-1) has never been evaluated in vivo, even though loss of expression in vitro is a wellcharacterized resistance mechanism (3,(14)(15)(16)(17)(18)(19). It was first hypothesized that PARPis work primarily through a synthetic lethality pathway where loss of BRCA1 or BRCA2 combined with chemical inhibition of PARP-1 results in cell death (20, 21). However, it was later shown that deletion of PARP1 did not result in BRCA1-restored cells showed no increase in γH2AX compared with DMSO controls. Olaparib-treated OVCAR8 PARP1-KO G1 and G3 cells showed a 1.3 times increase (ANOVA, **P < 0.01 and ***P < 0.001, respectively) in γH2AX...

Reactive oxygen species (ROS) are believed to play a major role in the proinflammatory, M1-polarized form of neuroinflammation. However, it has been difficult to assess the role of ROS and their role in neuroinflammation in animal models of disease because of the absence of probes capable of measuring their presence with the functional imaging technique positron emission tomography (PET). This study describes the synthesis and in vivo evaluation of [18F]ROStrace, a radiotracer for imaging superoxide in vivo with PET, in an LPS model of neuroinflammation. [18F]ROStrace was found to rapidly cross the blood–brain barrier (BBB) and was trapped in the brain of LPS-treated animals but not the control group. [18F]ox-ROStrace, the oxidized form of [18F]ROStrace, did not cross the BBB. These data suggest that [18F]ROStrace is a suitable radiotracer for imaging superoxide levels in the central nervous system with PET.

The fibrillary aggregation of the protein alpha synuclein (Asyn) is a hallmark of Parkinson's disease, and the identification of small molecule binding sites on fibrils is essential to the development of diagnostic imaging probes. A series of molecular modeling, photoaffinity labeling, mass spectrometry, and radioligand binding studies were conducted on Asyn fibrils. The results of these studies revealed the presence of three different binding sites within fibrillar Asyn capable of binding small molecules with moderate to high affinity. A knowledge of the amino acid residues in these binding sites will be important in the design of high affinity probes capable of imaging fibrillary species of Asyn.