Evaluation of Mitochondrial Complex 1 Density with [F]BCPP-EF in a Murine Model and Individuals with Friedreich Ataxia.

Friedreich ataxia is caused by mutations in the frataxin gene, leading to neurodegeneration and premature death from cardiac dysfunction. Loss of frataxin impacts mitochondrial complex 1 (MC1) activity, suggesting MC1 may be a potential biomarker of frataxin levels and function. Biomarkers evaluated by noninvasive techniques are needed to monitor disease progression and treatment effects in people with Friedreich ataxia.

18F-FLT PET, a Noninvasive Pharmacodynamic Biomarker of Tumor Cell Proliferation, Detected Differential Response to Various Cyclin-Dependent Kinase (CDK) Inhibitors.

A dysregulated cell cycle is a hallmark of cancer and inhibition of cyclin-dependent kinases (CDK) is a proven therapeutic strategy in treating hormone receptor-positive/HER2- breast cancer and a variety of other cancers. 18F-3'-deoxy-3'-fluorothymidine (18F-FLT) is a validated PET biomarker to measure cell proliferation. In this study, we show the utility of 18F-FLT PET imaging as a pharmcodynamic biomarker in differentiating the efficacy of PF-07104091 (CDK2-selective inhibitor) in palbociclib (CDK4/6 inhibitor)-sensitive and -resistant tumor models.

Characterization of a Novel M4 PAM PET Radioligand [11C]PF06885190 in Nonhuman Primates (NHP).

Muscarinic acetylcholine receptors (mAChR), including M4, draw attention as therapeutic targets for several neurodegenerative diseases including Alzheimer's disease (AD). PET imaging of M4 positive allosteric modulator (PAM) allows qualification of the distribution as well as the expression of this receptor under physiological conditions and thereby helps to assess the receptor occupancy (RO) of a drug candidate. In this study, our aims were (a) to synthesize a novel M4 PAM PET radioligand [11C]PF06885190 (b) to evaluate the brain distribution of [C]PF06885190 in nonhuman primates (NHP) and (c) to analyze its radiometabolites in the blood plasma of NHP.

Investigating CNS distribution of PF-05212377, a P-glycoprotein substrate, by translation of 5-HT receptor occupancy from non-human primates to humans.

PF-05212377 (SAM760) is a potent and selective 5-HT antagonist, previously under development for the treatment of Alzheimer's disease. In vitro, PF-05212377 was determined to be a P-gp/non-BCRP human transporter substrate. Species differences were observed in the in vivo brain penetration of PF-05212377 with a ratio of the unbound concentration in brain/unbound concentration in plasma (C /C ) of 0.

Evaluation of [F]PF-06455943 as a Potential LRRK2 PET Imaging Agent in the Brain of Nonhuman Primates.

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the common causes of inherited Parkinson's disease (PD) and emerged as a causative PD gene. Particularly, LRRK2-Gly2019Ser mutation was reported to alter the early phase of neuronal differentiation, increasing cell death. Selective inhibitors of LRRK2 kinase activity were considered as a promising therapeutic target for PD treatment.

Imaging Leucine-Rich Repeat Kinase 2 In Vivo with F-Labeled Positron Emission Tomography Ligand.

Leucine-rich repeat kinase 2 (LRRK2) has been demonstrated to be closely involved in the pathogenesis of Parkinson's disease (PD), and pharmacological blockade of LRRK2 represents a new opportunity for therapeutical treatment of PD and other related neurodegenerative conditions. The development of an LRRK2-specific positron emission tomography (PET) ligand would enable a target occupancy study in vivo and greatly facilitate LRRK2 drug discovery and clinical translation as well as provide a molecular imaging tool for studying physiopathological changes in neurodegenerative diseases. In this work, we present the design and development of compound (PF-06455943) as a promising PET radioligand through a PET-specific structure-activity relationship optimization, followed by comprehensive pharmacology and ADME/neuroPK characterization.

Widespread cell stress and mitochondrial dysfunction occur in patients with early Alzheimer's disease.

Cell stress and impaired oxidative phosphorylation are central to mechanisms of synaptic loss and neurodegeneration in the cellular pathology of Alzheimer's disease (AD). In this study, we quantified the in vivo expression of the endoplasmic reticulum stress marker, sigma 1 receptor (S1R), using [C]SA4503 positron emission tomography (PET), the mitochondrial complex I (MC1) with [F]BCPP-EF, and the presynaptic vesicular protein SV2A with [C]UCB-J in 12 patients with early AD and in 16 cognitively normal controls. We integrated these molecular measures with assessments of regional brain volumes and cerebral blood flow (CBF) measured with magnetic resonance imaging arterial spin labeling.

Preclinical Evaluation of Zr-Df-IAB22M2C PET as an Imaging Biomarker for the Development of the GUCY2C-CD3 Bispecific PF-07062119 as a T Cell Engaging Therapy.

Purpose: A sensitive and specific imaging biomarker to monitor immune activation and quantify pharmacodynamic responses would be useful for development of immunomodulating anti-cancer agents. PF-07062119 is a T cell engaging bispecific antibody that binds to CD3 and guanylyl cyclase C, a protein that is over-expressed by colorectal cancers. Here, we used Zr-Df-IAB22M2C (Zr-Df-Crefmirlimab), a human CD8-specific minibody to monitor CD8+ T cell infiltration into tumors by positron emission tomography.

Consensus Recommendations on the Use of F-FDG PET/CT in Lung Disease.

PET with F-FDG has been increasingly applied, predominantly in the research setting, to study drug effects and pulmonary biology and to monitor disease progression and treatment outcomes in lung diseases that interfere with gas exchange through alterations of the pulmonary parenchyma, airways, or vasculature. To date, however, there are no widely accepted standard acquisition protocols or imaging data analysis methods for pulmonary F-FDG PET/CT in these diseases, resulting in disparate approaches. Hence, comparison of data across the literature is challenging.

PET imaging of beta-secretase 1 in the human brain: radiation dosimetry, quantification, and test-retest examination of [F]PF-06684511.

Purpose: Beta-secretase 1 (BACE1) enzyme is implicated in the pathophysiology of Alzheimer's disease. [F]PF-06684511 is a positron emission tomography (PET) radioligand for imaging BACE1. Despite favorable brain kinetic properties, the effective dose (ED) of [F]PF-06684511 estimated in non-human primates was relatively high.

Positron Emission Tomography Imaging of [ C]Rosuvastatin Hepatic Concentrations and Hepatobiliary Transport in Humans in the Absence and Presence of Cyclosporin A.

Using positron emission tomography imaging, we determined the hepatic concentrations and hepatobiliary transport of [ C]rosuvastatin (RSV; i.v. injection) in the absence (n = 6) and presence (n = 4 of 6) of cyclosporin A (CsA; i.

Quantitative Analysis of F-PF-06684511, a Novel PET Radioligand for Selective β-Secretase 1 Imaging, in Nonhuman Primate Brain.

β-secretase 1 (BACE1) is a key enzyme in the generation of β-amyloid, which is accumulated in the brain of Alzheimer disease patients. PF-06684511 was identified as a candidate PET ligand for imaging BACE1 in the brain and showed high specific binding in an initial assessment in a nonhuman primate (NHP) PET study using F-PF-06684511. In this effort, we aimed to quantitatively evaluate the regional brain distribution of F-PF-06684511 in NHPs under baseline and blocking conditions and to assess the target occupancy of BACE1 inhibitors.

Decreased VMAT2 in the pancreas of humans with type 2 diabetes mellitus measured in vivo by PET imaging.

Aims/hypothesis: The progressive loss of beta cell function is part of the natural history of type 2 diabetes. Autopsy studies suggest that this is, in part, due to loss of beta cell mass (BCM), but this has not been confirmed in vivo. Non-invasive methods to quantify BCM may contribute to a better understanding of type 2 diabetes pathophysiology and the development of therapeutic strategies.

Identification of a Novel Positron Emission Tomography (PET) Ligand for Imaging β-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE-1) in Brain.

Alzheimer's disease (AD) is characterized by accumulation of β-amyloid (Aβ) plaques and neurofibrillary tau tangles in the brain. β-Site amyloid precursor protein cleaving enzyme 1 (BACE1) plays a key role in the generation of Aβ fragments via extracellular cleavage of the amyloid precursor protein (APP). We became interested in developing a BACE1 PET ligand to facilitate clinical assessment of BACE1 inhibitors and explore its potential in the profiling and selection of patients for AD trials.

Pharmacology in translation: the preclinical and early clinical profile of the novel α2/3 functionally selective GABA receptor positive allosteric modulator PF-06372865.

Background And Purpose: Benzodiazepines, non-selective positive allosteric modulators (PAMs) of GABA receptors, have significant side effects that limit their clinical utility. As many of these side effects are mediated by the α1 subunit, there has been a concerted effort to develop α2/3 subtype-selective PAMs.

Experimental Approach: In vitro screening assays were used to identify molecules with functional selectivity for receptors containing α2/3 subunits over those containing α1 subunits.

The Discovery of a Novel Phosphodiesterase (PDE) 4B-Preferring Radioligand for Positron Emission Tomography (PET) Imaging.

As part of our effort in identifying phosphodiesterase (PDE) 4B-preferring inhibitors for the treatment of central nervous system (CNS) disorders, we sought to identify a positron emission tomography (PET) ligand to enable target occupancy measurement in vivo. Through a systematic and cost-effective PET discovery process, involving expression level (B) and biodistribution determination, a PET-specific structure-activity relationship (SAR) effort, and specific binding assessment using a LC-MS/MS "cold tracer" method, we have identified 8 (PF-06445974) as a promising PET lead. Compound 8 has exquisite potency at PDE4B, good selectivity over PDE4D, excellent brain permeability, and a high level of specific binding in the "cold tracer" study.

Discovery and Characterization of (R)-6-Neopentyl-2-(pyridin-2-ylmethoxy)-6,7-dihydropyrimido[2,1-c][1,4]oxazin-4(9H)-one (PF-06462894), an Alkyne-Lacking Metabotropic Glutamate Receptor 5 Negative Allosteric Modulator Profiled in both Rat and Nonhuman Primates.

We previously observed a cutaneous type IV immune response in nonhuman primates (NHP) with the mGlu negative allosteric modulator (NAM) 7. To determine if this adverse event was chemotype- or mechanism-based, we evaluated a distinct series of mGlu NAMs. Increasing the sp character of high-throughput screening hit 40 afforded a novel morpholinopyrimidone mGlu NAM series.

Quantitative projection of human brain penetration of the H antagonist PF-03654746 by integrating rat-derived brain partitioning and PET receptor occupancy.

1. Unbound brain drug concentration (C), a valid surrogate of interstitial fluid drug concentration (C), cannot be directly determined in humans, which limits accurately defining the human C:C of investigational molecules. 2.

Preclinical Evaluation of 18F-PF-05270430, a Novel PET Radioligand for the Phosphodiesterase 2A Enzyme.

Unlabelled: The enzyme phosphodiesterase 2A (PF-05270430) is a potential target for development of novel therapeutic agents for the treatment of cognitive impairments. The goal of the present study was to evaluate the PDE2A ligand (18)F-PF-05270430, 4-(3-fluoroazetidin-1-yl)-7-methyl-5-(1-methyl-5-(4-(trifluoromethyl)phenyl)-1H-pyrazol-4-yl)imidazo[1,5-f][1,2,4]triazine, in nonhuman primates.

Methods: (18)F-PF-05270430 was radiolabeled by 2 methods via nucleophilic substitution of its tosylate precursor.

The discovery and characterization of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor potentiator N-{(3S,4S)-4-[4-(5-cyano-2-thienyl)phenoxy]tetrahydrofuran-3-yl}propane-2-sulfonamide (PF-04958242).

A unique tetrahydrofuran ether class of highly potent α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor potentiators has been identified using rational and structure-based drug design. An acyclic lead compound, containing an ether-linked isopropylsulfonamide and biphenyl group, was pharmacologically augmented by converting it to a conformationally constrained tetrahydrofuran to improve key interactions with the human GluA2 ligand-binding domain. Subsequent replacement of the distal phenyl motif with 2-cyanothiophene to enhance its potency, selectivity, and metabolic stability afforded N-{(3S,4S)-4-[4-(5-cyano-2-thienyl)phenoxy]tetrahydrofuran-3-yl}propane-2-sulfonamide (PF-04958242, 3), whose preclinical characterization suggests an adequate therapeutic index, aided by low projected human oral pharmacokinetic variability, for clinical studies exploring its ability to attenuate cognitive deficits in patients with schizophrenia.

Discovery and preclinical characterization of 1-methyl-3-(4-methylpyridin-3-yl)-6-(pyridin-2-ylmethoxy)-1H-pyrazolo-[3,4-b]pyrazine (PF470): a highly potent, selective, and efficacious metabotropic glutamate receptor 5 (mGluR5) negative allosteric modulator.

A novel series of pyrazolopyrazines is herein disclosed as mGluR5 negative allosteric modulators (NAMs). Starting from a high-throughput screen (HTS) hit (1), a systematic structure-activity relationship (SAR) study was conducted with a specific focus on balancing pharmacological potency with physicochemical and pharmacokinetic (PK) properties. This effort led to the discovery of 1-methyl-3-(4-methylpyridin-3-yl)-6-(pyridin-2-ylmethoxy)-1H-pyrazolo[3,4-b]pyrazine (PF470, 14) as a highly potent, selective, and orally bioavailable mGluR5 NAM.

Design and selection parameters to accelerate the discovery of novel central nervous system positron emission tomography (PET) ligands and their application in the development of a novel phosphodiesterase 2A PET ligand.

To accelerate the discovery of novel small molecule central nervous system (CNS) positron emission tomography (PET) ligands, we aimed to define a property space that would facilitate ligand design and prioritization, thereby providing a higher probability of success for novel PET ligand development. Toward this end, we built a database consisting of 62 PET ligands that have successfully reached the clinic and 15 radioligands that failed in late-stage development as negative controls. A systematic analysis of these ligands identified a set of preferred parameters for physicochemical properties, brain permeability, and nonspecific binding (NSB).

The synthesis and in vivo evaluation of [18F]PF-9811: a novel PET ligand for imaging brain fatty acid amide hydrolase (FAAH).

Introduction: Fatty acid amide hydrolase (FAAH) is responsible for the enzymatic degradation of the fatty acid amide family of signaling lipids, including the endogenous cannabinoid (endocannabinoid) anandamide. The involvement of the endocannabinoid system in pain and other nervous system disorders has made FAAH an attractive target for drug development. Companion molecular imaging probes are needed, however, to assess FAAH inhibition in the nervous system in vivo.

MicroPET detection of regional brain activation induced by colonic distention in a rat model of visceral hypersensitivity.

Using microPET and (18)F-fluorodeoxyglucose ((18)F-FDG) as a tracer, we investigated regional brain activation in a rat model of visceral hypersensitivity induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). TNBS injection into the proximal colon through laparotomy resulted in a significant, sustained decrease in the pain threshold to mechanical distention of the distal colon, indicating a phenomenon referred to as visceral hypersensitivity. When TNBS-induced colonic hypersensitivity was fully developed, all the TNBS-treated rats presented characteristic pain behaviors in response to colonic distention at previously innocuous pressure (0-35 mmHg) that produced no abdominal pain in sham-operated control animals.

X-ray CT high-density artefact suppression in the presence of bones.

This paper presents a novel method of reducing x-ray CT high-density artefacts generated by metal objects when abundant bone structures are present in the region of interest. This method has an advantage over previously proposed methods since it heavily suppresses the metal artefacts without introducing extra bone artefacts. The method of suppression requires that bone pixels are isolated and segmented by thresholding.