Nemacol is a small molecule inhibitor of C. elegans vesicular acetylcholine transporter with anthelmintic potential.

Nematode parasites of humans and livestock pose a significant burden to human health, economic development, and food security. Anthelmintic drug resistance is widespread among parasites of livestock and many nematode parasites of humans lack effective treatments. Here, we present a nitrophenyl-piperazine scaffold that induces motor defects rapidly in the model nematode Caenorhabditis elegans. We call this scaffold Nemacol and show that it inhibits the vesicular acetylcholine transporter (VAChT), a target recognized by commercial animal and crop health groups as a viable anthelmintic target. We demonstrate that it is possible to create Nemacol analogs that maintain potent in vivo activity whilst lowering their affinity to the mammalian VAChT 10-fold. We also show that Nemacol enhances the ability of the anthelmintic Ivermectin to paralyze C. elegans and the ruminant nematode parasite Haemonchus contortus. Hence, Nemacol represents a promising new anthelmintic scaffold that acts through a validated anthelmintic target.

Non-Invasive Assessment of Locally Overexpressed Human Adenosine 2A Receptors in the Heart of Transgenic Mice.

A2A adenosine receptors (A2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [18F]FLUDA to non-invasively determine the A2A-AR availability for diagnosis of the A2AR status. Therefore, we compared mice with cardiomyocyte-specific overexpression of the human A2A-AR (A2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of the selective A2AR ligand FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (Bmax and KD) of [18F]FLUDA on mouse and human atrial tissue samples by autoradiographic studies, and (3) investigated the in vivo uptake of the radiotracer by dynamic PET imaging in A2A-AR TG and WT. After A2A-AR stimulation by the A2A-AR agonist CGS 21680 in isolated atrial preparations, antagonistic effects of FLUDA were found in A2A-AR-TG animals but not in WT. Radiolabelled [18F]FLUDA exhibited a KD of 5.9 ± 1.6 nM and a Bmax of 455 ± 78 fmol/mg protein in cardiac samples of A2A-AR TG, whereas in WT, as well as in human atrial preparations, only low specific binding was found. Dynamic PET studies revealed a significantly higher initial uptake of [18F]FLUDA into the myocardium of A2A-AR TG compared to WT. The hA2A-AR-specific binding of [18F]FLUDA in vivo was verified by pre-administration of the highly affine A2AAR-specific antagonist istradefylline. Conclusion: [18F]FLUDA is a promising PET probe for the non-invasive assessment of the A2A-AR as a marker for pathologies linked to an increased A2A-AR density in the heart, as shown in patients with heart failure.

Internal dose assessment of (-)-18F-flubatine, comparing animal model datasets of mice and piglets with first-in-human results.

UNLABELLED: (-)-(18)F-flubatine is a promising tracer for neuroimaging of nicotinic acetylcholine receptors (nAChRs), subtype α4ß2, using PET. Radiation doses after intravenous administration of the tracer in mice and piglets were assessed to determine the organ doses (ODs) and the effective dose (ED) to humans. The results were compared with subsequent clinical investigations in human volunteers. METHODS: Twenty-seven female CD1 mice (weight ± SD, 28.2 ± 2.1 g) received intravenous injection of 0.75 ± 0.33 MBq of (-)-(18)F-flubatine. Up to 240 min after injection, 3 animals per time point were sacrificed and the organs harvested, weighed, and counted in a γ counter to determine mass and activity, respectively. Furthermore, whole-body PET scans of 5 female piglets (age ± SD, 44 ± 3 d; weight ± SD, 13.7 ± 1.7 kg) and 3 humans (2 men and 1 woman; age ± SD, 59.6 ± 3.9 y; weight ± SD, 74.3 ± 3.1 kg) were obtained up to 236 min (piglets) and 355 min (humans) after injection of 186.6 ± 7.4 and 353.7 ± 10.2 MBq of (-)-(18)F-flubatine, respectively, using a PET/CT scanner. The CT was used for delineation of the organs. Exponential curves were fitted to the time-activity-data, and time and mass scales were adapted to the human anatomy. The ODs were calculated using OLINDA/EXM (version 1.0); EDs were calculated with the tissue-weighting factors of ICRP103. RESULTS: After the injection of (-)-(18)F-flubatine, there were no adverse or clinically detectable pharmacologic effects in any of the subjects. The highest activities after injection were found in the kidneys, urinary bladder, and liver. The urinary bladder receives the highest OD in all investigated species, followed by the kidneys and the liver for animals and humans, respectively. On the basis of mouse, piglet, and human kinetic data, the projected human ED of (-)-(18)F-flubatine was estimated to be 12.5 µSv/MBq in mice, 14.7 ± 0.7 µSv/MBq in piglets, and 23.4 ± 0.4 µSv/MBq in humans. CONCLUSION: As has been demonstrated for other PET radiotracers, preclinical (i.e., animal-derived) dosimetry underestimates the ED to humans, in the current case of (-)-(18)F-flubatine by 34%-44%.

Assessment of α7 nicotinic acetylcholine receptor availability in juvenile pig brain with [¹8F]NS10743.

PURPOSE: To conduct a quantitative PET assessment of the specific binding sites in the brain of juvenile pigs for [(18)F]NS10743, a novel diazabicyclononane derivative targeting α7 nicotinic acetylcholine receptors (α7 nAChRs). METHODS: Dynamic PET recordings were made in isoflurane-anaesthetized juvenile pigs during 120 min after administration of [(18)F]NS10743 under baseline conditions (n = 3) and after blocking of the α7 nAChR with NS6740 (3 mg·kg(-1) bolus + 1 mg·kg(-1)·h(-1) continuous infusion; n = 3). Arterial plasma samples were collected for determining the input function of the unmetabolized tracer. Kinetic analysis of regional brain time-radioactivity curves was performed, and parametric maps were calculated relative to arterial input. RESULTS: Plasma [(18)F]NS10743 passed readily into the brain, with peak uptake occurring in α7 nAChR-expressing brain regions such as the colliculi, thalamus, temporal lobe and hippocampus. The highest SUV(max) was approximately 2.3, whereas the lowest uptake was in the olfactory bulb (SUV(max) 1.53 ± 0.32). Administration of NS6740 significantly decreased [(18)F]NS10743 binding late in the emission recording throughout the brain, except in the olfactory bulb, which was therefore chosen as reference region for calculation of BP(ND). The baseline BP(ND) ranged from 0.39 ± 0.08 in the cerebellum to 0.76 ± 0.07 in the temporal lobe. Pretreatment and constant infusion with NS6740 significantly reduced the BP(ND) in regions with high [(18)F]NS10743 binding (temporal lobe -29%, p = 0.01; midbrain: -35%, p = 0.02), without significantly altering the BP(ND) in low binding regions (cerebellum: -16%, p = 0.2). CONCLUSION: This study confirms the potential of [(18)F]NS10743 as a target-specific radiotracer for the molecular imaging of central α7 nAChRs by PET.