ABSTRACT
OBJECTIVES: The authors sought to develop combined positron emission tomography (PET) dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) to quantify plaque inflammation, permeability, and burden to evaluate the efficacy of a leukotriene A4 hydrolase (LTA4H) inhibitor in a rabbit model of atherosclerosis. BACKGROUND: Multimodality PET/MRI allows combining the quantification of atherosclerotic plaque inflammation, neovascularization, permeability, and burden by combined 18F-fluorodeoxyglucose (18F-FDG) PET, DCE-MRI, and morphological MRI. The authors describe a novel, integrated PET-DCE/MRI protocol to noninvasively quantify these parameters in aortic plaques of a rabbit model of atherosclerosis. As proof-of-concept, the authors apply this protocol to assess the efficacy of the novel LTA4H inhibitor BI691751. METHODS: New Zealand White male rabbits (N = 49) were imaged with integrated PET-DCE/MRI after atherosclerosis induction and 1 and 3 months after randomization into 3 groups: 1) placebo; 2) high-dose BI691751; and 3) low-dose BI691751. All animals were euthanized at the end of the study. RESULTS: Among the several metrics that were quantified, only maximum standardized uptake value and target-to-background ratio by 18F-FDG PET showed a modest, but significant, reduction in plaque inflammation in rabbits treated with low-dose BI691751 (p = 0.03), whereas no difference was detected in the high-fat diet and in the high-dose BI691751 groups. No differences in vessel wall area by MRI and area under the curve by DCE-MRI were detected in any of the groups. No differences in neovessel and macrophage density were found at the end of study among groups. CONCLUSIONS: The authors present a comprehensive, integrated 18F-FDG PET and DCE-MRI imaging protocol to noninvasively quantify plaque inflammation, neovasculature, permeability, and burden in a rabbit model of atherosclerosis on a simultaneous PET/MRI scanner. A modest reduction was found in plaque inflammation by 18F-FDG PET in the group treated with a low dose of the LTA4H inhibitor BI691751.
Subject(s)
Anti-Inflammatory Agents/pharmacology , Aortic Diseases/drug therapy , Atherosclerosis/drug therapy , Capillary Permeability/drug effects , Enzyme Inhibitors/pharmacology , Epoxide Hydrolases/antagonists & inhibitors , Inflammation/drug therapy , Magnetic Resonance Imaging , Plaque, Atherosclerotic , Positron-Emission Tomography , Animals , Aortic Diseases/diagnostic imaging , Aortic Diseases/enzymology , Aortic Diseases/pathology , Atherosclerosis/diagnostic imaging , Atherosclerosis/enzymology , Atherosclerosis/pathology , Biomarkers/blood , Contrast Media/administration & dosage , Disease Models, Animal , Epoxide Hydrolases/metabolism , Fluorodeoxyglucose F18/administration & dosage , Gadolinium DTPA/administration & dosage , Inflammation/diagnostic imaging , Inflammation/enzymology , Inflammation/pathology , Male , Multimodal Imaging , Predictive Value of Tests , Rabbits , Radiopharmaceuticals/administration & dosageABSTRACT
Follicle-stimulating hormone (FSH), acting on its receptor (FSHR), plays a pivotal role in the stimulation of follicular development and maturation. Multiple injections of protein formulations are used during clinical protocols for ovulation induction and for in vitro fertilization that are followed by a selection of assisted reproductive technologies. In order to increase patient convenience and compliance several research groups have searched for orally bioavailable FSH mimetics for innovative fertility medicines. We report here the discovery of a series of substituted benzamides as positive allosteric modulators (PAM) targeting FSHR. Optimization of this series has led to enhanced activity in primary rat granulosa cells, as well as remarkable selectivity against the closely related luteinizing hormone receptor (LHR) and thyroid stimulating hormone receptor (TSHR). Two modulators, 9j and 9k, showed promising in vitro and pharmacokinetic profiles.
Subject(s)
Allosteric Regulation/drug effects , Benzamides/chemistry , Benzamides/pharmacology , Follicle Stimulating Hormone/metabolism , Animals , CHO Cells , Cells, Cultured , Cricetulus , Female , Follicle Stimulating Hormone/agonists , Granulosa Cells/drug effects , Granulosa Cells/metabolism , Humans , RatsABSTRACT
The strand-exchange engineered domain (SEED) platform was designed to generate asymmetric and bispecific antibody-like molecules, a capability that expands therapeutic applications of natural antibodies. This new protein engineered platform is based on exchanging structurally related sequences of immunoglobulin within the conserved CH3 domains. Alternating sequences from human IgA and IgG in the SEED CH3 domains generate two asymmetric but complementary domains, designated AG and GA. The SEED design allows efficient generation of AG/GA heterodimers, while disfavoring homodimerization of AG and GA SEED CH3 domains. Using a clinically validated antibody (C225), we tested whether Fab derivatives constructed on the SEED platform retain desirable therapeutic antibody features such as in vitro and in vivo stability, favorable pharmacokinetics, ligand binding and effector functions including antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. In addition, we tested SEED with combinations of binder domains (scFv, VHH, Fab). Mono- and bivalent Fab-SEED fusions retain full binding affinity, have excellent biochemical and biophysical stability, and retain desirable antibody-like characteristics conferred by Fc domains. Furthermore, SEED is compatible with different combinations of Fab, scFv and VHH domains. Our assessment shows that the new SEED platform expands therapeutic applications of natural antibodies by generating heterodimeric Fc-analog proteins.
