Liver Investigation: Testing Marker Utility in Steatohepatitis (LITMUS): Assessment & validation of imaging modality performance across the NAFLD spectrum in a prospectively recruited cohort study (the LITMUS imaging study): Study protocol.

Non-alcoholic fatty liver disease (NAFLD) is the liver manifestation of the metabolic syndrome with global prevalence reaching epidemic levels. Despite the high disease burden in the population only a small proportion of those with NAFLD will develop progressive liver disease, for which there is currently no approved pharmacotherapy. Identifying those who are at risk of progressive NAFLD currently requires a liver biopsy which is problematic. Firstly, liver biopsy is invasive and therefore not appropriate for use in a condition like NAFLD that affects a large proportion of the population. Secondly, biopsy is limited by sampling and observer dependent variability which can lead to misclassification of disease severity. Non-invasive biomarkers are therefore needed to replace liver biopsy in the assessment of NAFLD. Our study addresses this unmet need. The LITMUS Imaging Study is a prospectively recruited multi-centre cohort study evaluating magnetic resonance imaging and elastography, and ultrasound elastography against liver histology as the reference standard. Imaging biomarkers and biopsy are acquired within a 100-day window. The study employs standardised processes for imaging data collection and analysis as well as a real time central monitoring and quality control process for all the data submitted for analysis. It is anticipated that the high-quality data generated from this study will underpin changes in clinical practice for the benefit of people with NAFLD. Study Registration: clinicaltrials.gov: NCT05479721.

Synthesis, crystal structure, and in vitro biological evaluation of C-6 pyrimidine derivatives: new lead structures for monitoring gene expression in vivo.

Novel C-6 substituted pyrimidine derivatives are good substrates of herpes simplex virus type 1 thymidine kinase (HSV1-TK). Enzyme kinetic experiments showed that our lead compound, N-methyl DHBT (N-methyl-6-(1,3-dihydroxyisobutyl) thymine; N-Me DHBT), is phosphorylated at a similar rate compared to "gold standard" 9-[4-fluoro-3-(hydroxymethyl)butyl]guanine, FHBG, (K(m) = 10 ± 0.3 µM; k(cat) = 0.036 ± 0.015 sec(-1)). Additionally, it does not show cytotoxic properties on B16F1 cells up to a concentration of 10 mM. The x-ray analysis of the crystal structures of HSV1-TK with N-Me DHBT and of HSV1-TK with the fluorinated derivative N-Me FHBT confirmed the binding mode predicted by docking studies and their substrate characteristics. Moreover, the crystal structure of HSV1-TK with N-Me DHBT revealed an additional water-mediated H-bond interesting for the design of further analogues.

18F-labeled bombesin analog for specific and effective targeting of prostate tumors expressing gastrin-releasing peptide receptors.

UNLABELLED: Bombesin is a peptide exhibiting high affinity for the gastrin-releasing peptide receptor (GRPr), which is highly overexpressed on prostate cancer cells. In the present study, we developed an (18)F-labeled bombesin analog, (18)F-BAY 86-4367, which is currently being clinically tested for use in PET of prostate cancer. METHODS: In vitro pharmacologic studies were performed to characterize the nonradioactive ((19)F) standard of the bombesin analog for binding affinity and selectivity for GRPr. The stability of (18)F-BAY 86-4367 was determined in murine and human plasma. In vivo, the tumor-targeting potential and pharmacokinetic profile of the (18)F tracer were analyzed with biodistribution experiments and PET studies of prostate tumor-bearing mice. RESULTS: The nonradioactive ((19)F) standard of the bombesin analog showed subnanomolar and GRPr-selective binding affinity. The stability of the tracer in murine and human plasma was found to be high. In 2 prostate cancer xenograft models (PC-3 and LNCaP), (18)F-BAY 86-4367 showed more specific and effective GRPr-based targeting in vivo than the benchmark radiotracers (18)F-fluoroethylcholine and (18)F-FDG. In addition, rapid tumor targeting and fast renal excretion (∼70%) and hepatobiliary excretion (∼10%) were identified in both xenograft models. Furthermore, PET studies provided clear and specific visualization of PC-3 tumors in mice. CONCLUSION: Favorable preclinical data showing specific and effective tumor targeting by (18)F-BAY 86-4367 suggest that a clinical trial be undertaken to test its diagnostic utility in PET for prostate carcinoma patients.

In vitro and in vivo characterization of novel 18F-labeled bombesin analogues for targeting GRPR-positive tumors.

The gastrin-releasing peptide receptor (GRPR) is overexpressed on a number of human tumors and has been targeted with radiolabeled bombesin analogues for the diagnosis and therapy of these cancers. Seven bombesin analogues containing various linkers and peptide sequences were designed, synthesized, radiolabeled with (18)F, and characterized in vitro and in vivo as potential PET imaging agents. Binding studies displayed nanomolar binding affinities toward human GRPR for all synthesized bombesin analogues. Two high-affinity peptide candidates 6b (K(i) = 0.7 nM) and 7b (K(i) = 0.1 nM) were chosen for further in vivo evaluation. Both tracers revealed specific uptake in GRPR-expressing PC-3 tumors and the pancreas. Compared to [(18)F]6b, compound [(18)F]7b was characterized by superior tumor uptake, higher specificity of tracer uptake, and more favorable tumor-to-nontarget ratios. In vivo PET imaging allowed for the visualization of PC-3 tumor in nude mice suggesting that [(18)F]7b is a promising PET tracer candidate for the diagnosis of GRPR-positive tumors in humans.