Discovery of the Potent and Selective MC4R Antagonist PF-07258669 for the Potential Treatment of Appetite Loss.

The melanocortin-4 receptor (MC4R) is a centrally expressed, class A GPCR that plays a key role in the regulation of appetite and food intake. Deficiencies in MC4R signaling result in hyperphagia and increased body mass in humans. Antagonism of MC4R signaling has the potential to mitigate decreased appetite and body weight loss in the setting of anorexia or cachexia due to underlying disease.

Effect of a Ketohexokinase Inhibitor (PF-06835919) on In Vivo OATP1B Activity: Integrative Risk Assessment Using Endogenous Biomarker and a Probe Drug.

PF-06835919 is a first-in-class ketohexokinase inhibitor (KHKi), recently under development for the treatment of metabolic and fatty liver diseases, which inhibited organic anion transporting polypeptide (OATP)1B1 in vitro and presented drug-drug interaction (DDI) risk. This study aims to investigate the dose-dependent effect of KHKi on OATP1B in vivo activity. We performed an open-label study comparing pharmacokinetics of atorvastatin (OATP1B probe) dosed alone (20 mg single dose) and coadministered with two dose strengths of KHKi (50 and 280 mg once daily) in 12 healthy participants.

Target occupancy study and whole-body dosimetry with a MAGL PET ligand [C]PF-06809247 in non-human primates.

Background: Monoacylglycerol lipase (MAGL) is a key serine hydrolase which terminates endocannabinoid signaling and regulates arachidonic acid driven inflammatory responses within the central nervous system. To develop [C]PF-06809247 into a clinically usable MAGL positron emission tomography (PET) radioligand, we assessed the occupancy of MAGL by an inhibitor in the non-human primate (NHP) brain. Additionally, we measured the whole-body distribution of [C]PF-06809247 in NHP and estimated human effective radiation doses.

The Effects of a Novel Non-catechol Dopamine Partial Agonist on Working Memory in the Aged Rhesus Monkey.

Aged-related declines in cognition, especially working memory and executive function, begin in middle-age and these abilities are known to be mediated by the prefrontal cortex (PFC) and more specifically the dopamine (DA) system within the PFC. In both humans and monkeys, there is significant evidence that the PFC is the first cortical region to change with age and the PFC appears to be particularly vulnerable to age-related loss of dopamine (DA). Therefore, the DA system is a strong candidate for therapeutic intervention to slow or reverse age related declines in cognition.

D1 Agonist Improved Movement of Parkinsonian Nonhuman Primates with Limited Dyskinesia Side Effects.

Parkinson's disease is a progressive neurodegenerative disease characterized by striatal dopaminergic loss. L-DOPA treatment replaces lost dopamine and enables motor function; however, eventually, fluctuating efficacy and side effects associated with its use become challenging for many patients. Here, we demonstrate, in a clinically translatable nonhuman primate model of parkinsonian motor symptoms, that treatment with the partial D1 receptor agonist CVL-751, formerly known as PF-06649751, is just as effective as L-DOPA in enabling movement and reducing disability.

Quantitative Translational Analysis of Brain Kynurenic Acid Modulation via Irreversible Kynurenine Aminotransferase II Inhibition.

Kynurenic acid (KYNA) plays a significant role in maintaining normal brain function, and abnormalities in KYNA levels have been associated with various central nervous system disorders. Confirmation of its causality in human diseases requires safe and effective modulation of central KYNA levels in the clinic. The kynurenine aminotransferases (KAT) II enzyme represents an attractive target for pharmacologic modulation of central KYNA levels; however, KAT II and KYNA turnover kinetics, which could contribute to the duration of pharmacologic effect, have not been reported.

Discovery of Trifluoromethyl Glycol Carbamates as Potent and Selective Covalent Monoacylglycerol Lipase (MAGL) Inhibitors for Treatment of Neuroinflammation.

Monoacylglycerol lipase (MAGL) inhibition provides a potential treatment approach to neuroinflammation through modulation of both the endocannabinoid pathway and arachidonoyl signaling in the central nervous system (CNS). Herein we report the discovery of compound 15 (PF-06795071), a potent and selective covalent MAGL inhibitor, featuring a novel trifluoromethyl glycol leaving group that confers significant physicochemical property improvements as compared with earlier inhibitor series with more lipophilic leaving groups. The design strategy focused on identifying an optimized leaving group that delivers MAGL potency, serine hydrolase selectivity, and CNS exposure while simultaneously reducing log  D, improving solubility, and minimizing chemical lability.

Systematic N-methylation of oxytocin: Impact on pharmacology and intramolecular hydrogen bonding network.

Oxytocin (OT) is a peptide hormone agonist of the OT receptor (OTR) that plays an important role in social behaviors such as pair bonding, maternal bonding and trust. The pharmaceutical development of OT as an oral peptide therapeutic has been hindered historically by its unfavorable physicochemical properties, including molecular weight, polarity and number of hydrogen bond donors, which determines poor cell permeability. Here we describe the first systematic study of single and multiple N-methylations of OT and their effect on physicochemical properties as well as potency at the OT receptor.

Peripheral Administration of a Long-Acting Peptide Oxytocin Receptor Agonist Inhibits Fear-Induced Freezing.

Oxytocin (OT) modulates the expression of social and emotional behaviors and consequently has been proposed as a pharmacologic treatment of psychiatric diseases, including autism spectrum disorders and schizophrenia; however, endogenous OT has a short half-life in plasma and poor permeability across the blood-brain barrier. Recent efforts have focused on the development of novel drug delivery methods to enhance brain penetration, but few efforts have aimed at improving its half-life. To explore the behavioral efficacy of an OT analog with enhanced plasma stability, we developed PF-06655075 (PF1), a novel non-brain-penetrant OT receptor agonist with increased selectivity for the OT receptor and significantly increased pharmacokinetic stability.

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.

Structure-Based Design of Irreversible Human KAT II Inhibitors: Discovery of New Potency-Enhancing Interactions.

A series of aryl hydroxamates recently have been disclosed as irreversible inhibitors of kynurenine amino transferase II (KAT II), an enzyme that may play a role in schizophrenia and other psychiatric and neurological disorders. The utilization of structure-activity relationships (SAR) in conjunction with X-ray crystallography led to the discovery of hydroxamate 4, a disubstituted analogue that has a significant potency enhancement due to a novel interaction with KAT II. The use of k inact/K i to assess potency was critical for understanding the SAR in this series and for identifying compounds with improved pharmacodynamic profiles.

Application of structure-based drug design and parallel chemistry to identify selective, brain penetrant, in vivo active phosphodiesterase 9A inhibitors.

Phosphodiesterase 9A inhibitors have shown activity in preclinical models of cognition with potential application as novel therapies for treating Alzheimer's disease. Our clinical candidate, PF-04447943 (2), demonstrated acceptable CNS permeability in rats with modest asymmetry between central and peripheral compartments (free brain/free plasma = 0.32; CSF/free plasma = 0.

Design and discovery of 6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (PF-04447943), a selective brain penetrant PDE9A inhibitor for the treatment of cognitive disorders.

6-[(3S,4S)-4-Methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (PF-04447943) is a novel PDE9A inhibitor identified using parallel synthetic chemistry and structure-based drug design (SBDD) and has advanced into clinical trials. Selectivity for PDE9A over other PDE family members was achieved by targeting key residue differences between the PDE9A and PDE1C catalytic site. The physicochemical properties of the series were optimized to provide excellent in vitro and in vivo pharmacokinetics properties in multiple species including humans.

Discovery of Brain-Penetrant, Irreversible Kynurenine Aminotransferase II Inhibitors for Schizophrenia.

Kynurenine aminotransferase (KAT) II has been identified as a potential new target for the treatment of cognitive impairment associated with schizophrenia and other psychiatric disorders. Following a high-throughput screen, cyclic hydroxamic acid PF-04859989 was identified as a potent and selective inhibitor of human and rat KAT II. An X-ray crystal structure and (13)C NMR studies of PF-04859989 bound to KAT II have demonstrated that this compound forms a covalent adduct with the enzyme cofactor, pyridoxal phosphate (PLP), in the active site.

Phosphodiesterase 9A regulates central cGMP and modulates responses to cholinergic and monoaminergic perturbation in vivo.

Cyclic nucleotides are critical regulators of synaptic plasticity and participate in requisite signaling cascades implicated across multiple neurotransmitter systems. Phosphodiesterase 9A (PDE9A) is a high-affinity, cGMP-specific enzyme widely expressed in the rodent central nervous system. In the current study, we observed neuronal staining with antibodies raised against PDE9A protein in human cortex, cerebellum, and subiculum.

Use of structure-based design to discover a potent, selective, in vivo active phosphodiesterase 10A inhibitor lead series for the treatment of schizophrenia.

Utilizing structure-based virtual library design and scoring, a novel chimeric series of phosphodiesterase 10A (PDE10A) inhibitors was discovered by synergizing binding site interactions and ADME properties of two chemotypes. Virtual libraries were docked and scored for potential binding ability, followed by visual inspection to prioritize analogs for parallel and directed synthesis. The process yielded highly potent and selective compounds such as 16.

Identification of a brain penetrant PDE9A inhibitor utilizing prospective design and chemical enablement as a rapid lead optimization strategy.

By use of chemical enablement and prospective design, a novel series of selective, brain penetrant PDE9A inhibitors have been identified that are capable of producing in vivo elevations of brain cGMP.