Discovery of a High Affinity, Orally Bioavailable Macrocyclic FXIa Inhibitor with Antithrombotic Activity in Preclinical Species.

Oral factor XIa (FXIa) inhibitors may provide a promising new antithrombotic therapy with an improved benefit to bleeding risk profile over existing antithrombotic agents. Herein, we report application of a previously disclosed cyclic carbamate P1 linker which provided improved oral bioavailability in the imidazole-based 13-membered macrocycle to the 12-membered macrocycle. This resulted in identification of compound 4 with desired FXIa inhibitory potency and good oral bioavailability but high in vivo clearance. Further structure-activity relationship (SAR) studies of heterocyclic core modifications to replace the imidazole core as well as various linkers to the P1 group led to the discovery of compound 6f, a potent FXIa inhibitor with selectivity against most of the relevant serine proteases. Compound 6f also demonstrated excellent pharmacokinetics (PK) profile (high oral bioavailability and low clearance) in multiple preclinical species. Compound 6f achieved robust antithrombotic efficacy in a rabbit efficacy model at doses which preserved hemostasis.

Orally bioavailable amine-linked macrocyclic inhibitors of factor XIa.

The discovery of orally bioavailable FXIa inhibitors has been a challenge. Herein, we describe our efforts to address this challenge by optimization of our imidazole-based macrocyclic series. Our optimization strategy focused on modifications to the P2 prime, macrocyclic amide linker, and the imidazole scaffold. Replacing the amide of the macrocyclic linker with amide isosteres led to the discovery of substituted amine linkers which not only maintained FXIa binding affinity but also improved oral exposure in rats. Combining the optimized macrocyclic amine linker with a pyridine scaffold afforded compounds 23 and 24 that were orally bioavailable, single-digit nanomolar FXIa inhibitors with excellent selectivity against relevant blood coagulation enzymes.

Evaluating the Impact of an Innovative Public Speaking Competition to Promote Psychiatry as a Career Option for Ghanaian Medical Students.

OBJECTIVE: The psychiatrist workforce has been identified as an area in need of development, especially in low- to middle-income countries. The purpose of this project is to assess the perceptions of Ghanaian medical students of a novel mental health inter-medical school speaking competition on career interest in psychiatry and mental health education and advocacy. METHODS: The study employed quantitative and qualitative methods in a cross-sectional design. A paper-based survey was administered to medical students from four schools in Ghana, and focus groups were conducted. RESULTS: A 52% response rate (545/1041 fifth- and sixth-year medical students from the four public medical schools in Ghana) was achieved. The competition was successful in stimulating interest in psychiatry as a subject (25%) and as a career (14%) and was viewed as serving an important public health and mental health advocacy function (65% and 66% respectively). The competition stimulated interest in students who were undecided or had previously ruled out psychiatry specialization, in both those who had and had not already completed a psychiatry clerkship (23% and 13% before and after completing a clinical rotation in psychiatry, respectively). Overall, 29% of respondents who participated in at least one competition-related activity reported that the competition stimulated their interest in psychiatry, compared to 4% who did not participate in any competition-related activity (Ó¼2 = 80, p = 0.0). Analysis of focus group content echoed these themes and highlighted opportunities for improvement. CONCLUSION: The innovative public speaking competition was successful in stimulating interest in psychiatry and furthering mental health education and advocacy. Implications are discussed.

Novel phenylalanine derived diamides as Factor XIa inhibitors.

The synthesis, structural activity relationships (SAR), and selectivity profile of a potent series of phenylalanine diamide FXIa inhibitors will be discussed. Exploration of P1 prime and P2 prime groups led to the discovery of compounds with high FXIa affinity, good potency in our clotting assay (aPPT), and high selectivity against a panel of relevant serine proteases as exemplified by compound 21. Compound 21 demonstrated good in vivo efficacy (EC50=2.8µM) in the rabbit electrically induced carotid arterial thrombosis model (ECAT).

Discovery of a Potent Parenterally Administered Factor XIa Inhibitor with Hydroxyquinolin-2(1H)-one as the P2' Moiety.

Structure-activity relationship optimization of phenylalanine P1' and P2' regions with a phenylimidazole core resulted in a series of potent FXIa inhibitors. Introducing 4-hydroxyquinolin-2-one as the P2' group enhanced FXIa affinity and metabolic stability. Incorporation of an N-methyl piperazine amide group to replace the phenylalanine improved both FXIa potency and aqueous solubility. Combination of the optimization led to the discovery of FXIa inhibitor 13 with a FXIa K i of 0.04 nM and an aPTT EC2x of 1.0 µM. Dose-dependent efficacy (EC50 of 0.53 µM) was achieved in the rabbit ECAT model with minimal bleeding time prolongation.

Inhibitors of leucine-rich repeat kinase 2 (LRRK2): progress and promise for the treatment of Parkinson's disease.

Mutations in the gene for leucine-rich repeat kinase 2 (LRRK2) have been linked to several familial and sporadic late-onset cases of Parkinson's disease. The cumulative data for the effects of mutant forms of this enzyme on neuronal degradation and the pathophysiology of Parkinson's disease create a compelling case for drug discovery based on inhibition of the mutant forms of LRRK2. This review focuses on structure-activity relationships for inhibitors of LRRK2 and the data supporting a potential role of these agents in treating Parkinson's disease.

Synthesis and structure-activity relationships of pyrido[3,2-b]pyrazin-3(4H)-ones and pteridin-7(8H)-ones as corticotropin-releasing factor-1 receptor antagonists.

Pyrido[3,2-b]pyrazin-3(4H)-ones and pteridin-7(8H)-ones were evaluated as corticotropin-releasing factor-1 receptor antagonists. The synthesis, SAR studies and pharmacokinetic evaluation of these analogs are described herein.

Synthesis and structure-activity relationships of 8-(pyrid-3-yl)pyrazolo[1,5-a]-1,3,5-triazines: potent, orally bioavailable corticotropin releasing factor receptor-1 (CRF1) antagonists.

This report describes the syntheses and structure-activity relationships of 8-(substituted pyridyl)pyrazolo[1,5-a]-1,3,5-triazine corticotropin releasing factor receptor-1 (CRF(1)) receptor antagonists. These CRF(1) receptor antagonists may be potential anxiolytic or antidepressant drugs. This research resulted in the discovery of compound 13-15, which is a potent, selective CRF(1) antagonist (hCRF(1) IC(50) = 6.1 +/- 0.6 nM) with weak affinity for the CRF-binding protein and biogenic amine receptors. This compound also has a good pharmacokinetic profile in dogs. Analogue 13-15 is orally effective in two rat models of anxiety: the defensive withdrawal (situational anxiety) model and the elevated plus maze test. Analogue 13-15 has been advanced to clinical trials.

8-(4-Methoxyphenyl)pyrazolo[1,5-a]-1,3,5-triazines: selective and centrally active corticotropin-releasing factor receptor-1 (CRF1) antagonists.

This report describes the syntheses and structure-activity relationships of 8-(4-methoxyphenyl)pyrazolo[1,5-a]-1,3,5-triazine corticotropin releasing factor receptor-1 (CRF(1)) receptor antagonists. CRF(1) receptor antagonists may be potential anxiolytic or antidepressant drugs. This research culminated in the discovery of analogue 12-3, which is a potent, selective CRF(1) antagonist (hCRF(1) IC(50) = 4.7 +/- 2.0 nM) with weak affinity for the CRF-binding protein and biogenic amine receptors. This compound also has a good pharmacokinetic profile in dogs. Analogue 12-3 is orally effective in two rat models of anxiety: the defensive withdrawal (situational anxiety) model and the elevated plus maze test. Analogue 12-3 has been advanced to clinical trials.

Dihydropyridopyrazinones and dihydropteridinones as corticotropin-releasing factor-1 receptor antagonists: structure-activity relationships and computational modeling.

The CRF antagonist pharmacophore is a heterocyclic ring bearing a critical hydrogen-bond acceptor nitrogen and an orthogonal aromatic ring. CRFR1 antagonists have shown a 40-fold and 200-fold loss in potency against the CRFR1 H199V and M276I mutant receptors, suggesting key interactions with these residues. We have derived a two component computational model that correlates CRFR1 binding affinity within the reported series to antagoinst/H199 complexation energy and M276 hydrophobic contacts.

Corticotropin-releasing factor receptor antagonists.

Corticotropin-releasing factor (CRF) coordinates the neural, endocrine and immune responses of the body to stress. Therefore, CRF receptors are important targets for the design of drugs for depression, anxiety and stress-related disorders. Several laboratories have published extensive preclinical and limited clinical research into the role of CRF in human disease. This review covers developments in the patent literature during 2002 - 2006 and outlines the prospects for CRF-based therapy for mental illness.

Synthesis and evaluation of 2-anilino-3-phenylsulfonyl-6-methylpyridines as corticotropin-releasing factor1 receptor ligands.

A novel series of 2-anilino-3-phenylsulfonyl-6-methylpyridines was synthesized and evaluated as corticotropin-releasing factor receptor ligands. Structure-activity relationship studies focused primarily on optimization of the 3-phenylsulfonyl group. Compounds within this series were identified which showed potent binding affinity for the CRF1 receptor. Selected compounds were examined in a rat pharmacokinetic study and were found to have oral bioavailabilities ranging from 16 to 35%.

Quantitative trait loci with age-specific effects on fecundity in Drosophila melanogaster.

Life-history theory and evolutionary theories of aging assume the existence of alleles with age-specific effects on fitness. While various studies have documented age-related changes in the genetic contribution to variation in fitness components, we know very little about the underlying genetic architecture of such changes. We used a set of recombinant inbred lines to map and characterize the effects of quantitative trait loci (QTL) affecting fecundity of Drosophila melanogaster females at 1 and 4 weeks of age. We identified one QTL on the second chromosome and one or two QTL affecting fecundity on the third chromosome, but these QTL affected fecundity only at 1 week of age. There was more genetic variation for fecundity at 4 weeks of age than at 1 week of age and there was no genetic correlation between early and late-age fecundity. These results suggest that different loci contribute to the variation in fecundity as the organism ages. Our data provide support for the mutation accumulation theory of aging as applied to reproductive senescence. Comparing the results from this study with our previous work on life-span QTL, we also find evidence that antagonistic pleiotropy may contribute to the genetic basis of senescence in these lines as well.

The pharmacology of DMP696 and DMP904, non-peptidergic CRF1 receptor antagonists.

CRF(1) antagonists DMP696 and DMP904 were designed as drug development candidates for the treatment of anxiety and depression. Both compounds display nanomolar affinity for human CRF(1) receptors, and exhibit >1000-fold selectivity for CRF(1) over CRF(2) receptors and over a broad panel of other proteins. DMP696 and DMP904 block CRF-stimulated adenylyl cyclase activity in cortical homogenates and cell-lines expressing CRF(1) receptors. Both compounds inhibit CRF-stimulated ACTH release from rat pituitary corticotropes. Binding and functional studies indicate that DMP696 and DMP904 behave as noncompetitive full antagonists. DMP696 and DMP904 exhibit anxiolytic-like efficacy in several rat anxiety models. In the defensive withdrawal test, both compounds reduce exit latency with lowest effective doses of 3 and 1 mg/kg, respectively. The anxiolytic-like effect is maintained over 14 days of repeated dosing. In the context of a novel environment used in this test, DMP696 and DMP904 reverse mild stress-induced increases in plasma CORT secretion but at doses 3-4-fold greater than those required for anxiolyticlike efficacy. DMP696 and DMP904 are ineffective in three depression models including the learned helplessness paradigm at doses up to 30 mg/kg. At lowest anxiolytic-like doses, DMP696 and DMP904 occupy >50% CRF(1) receptors in the brain. The in vivo IC(50) values (plasma concentrations required for occupying 50% CRF(1) receptors) estimated based upon free, but not total, plasma concentrations are an excellent correlation with the in vitro IC(50) values. Neither compound produces sedation, ataxia, chlordiazepoxide-like subjective effects or adverse effects on cognition at doses 10-fold higher than anxiolytic-like doses. Neither compound produces physiologically significant changes in cardiovascular, respiratory, gastrointestinal or renal functions at anxiolytic-like doses. DMP696 and DMP904 have favorable pharmacokinetic profiles with good oral bioavailabilities. The overall pharmacological properties suggest that both compounds may be effective anxiolytics with low behavioral side effect liabilities.

Effects of CRF1 receptor antagonists and benzodiazepines in the Morris water maze and delayed non-matching to position tests.

RATIONALE: Benzodiazepines continue to be widely used for the treatment of anxiety, but it is well known that benzodiazepines have undesirable side effects, including sedation, ataxia, cognitive deficits and the risk of addiction and abuse. CRF(1) receptor antagonists are being developed as potential novel anxiolytics, but while CRF(1) receptor antagonists seem to have a better side-effect profile than benzodiazepines with respect to sedation and ataxia, the effects of CRF(1) receptor antagonists on cognitive function have not been well characterized. It is somewhat surprising that the potential cognitive effects of CRF(1) receptor antagonists have not been more fully characterized since there is some evidence to suggest that these compounds may impair cognitive function. OBJECTIVE: The Morris water maze and the delayed non-matching to position test are sensitive tests of a range of cognitive functions, including spatial learning, attention and short-term memory, so the objective of the present experiments was to assess the effects of benzodiazepines and CRF(1) receptor antagonists in these tests. RESULTS: The benzodiazepines chlordiazepoxide and alprazolam disrupted performance in the Morris water maze and delayed non-matching to position at doses close to their therapeutic, anxiolytic doses. In contrast, the CRF(1) receptor antagonists DMP-904 and DMP-696 produced little or no impairment in the Morris water maze or delayed non-matching to position test even at doses 10-fold higher than were necessary to produce anxiolytic effects. CONCLUSIONS: The results of the present experiments suggest that, with respect to their effects on cognitive functions, CRF(1) receptor antagonists seem to have a wider therapeutic index than benzodiazepines.

Synthesis, structure-activity relationships, and in vivo properties of 3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-ones as corticotropin-releasing factor-1 receptor antagonists.

Corticotropin releasing factor (CRF) is the primary regulator of the hypothalamus-pituitary-adrenal (HPA) axis, coordinating the endocrine, behavioral, and autonomic responses to stress. It has been postulated that small molecules that can antagonize the binding of CRF1 to its receptor may serve as a treatment for anxiety-related and/or affective disorders. Members within a series of 3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-ones, exemplified by compound 2 (IC50 = 0.70 nM), were found to be very potent antagonists of CRF1. Compound 8w showed high CRF1 receptor binding affinity and was examined further in vivo. The compound was efficacious in a defensive withdrawal model of anxiety in rats and had a long half-life and reasonable oral bioavailability in dog pharmacokinetic studies.

Corticotropin-releasing factor antagonists: recent advances and exciting prospects for the treatment of human diseases.

Corticotropin-releasing factor (CRF) co-ordinates the neural, endocrine and immune responses of the body to stress. Several studies have implicated CRF in the etiology of anxiety, depression, substance abuse, stress-related gastrointestinal disorders and preterm labor, and intensive research into the design of safe and effective CRF antagonists is currently being pursued in several laboratories. Recently, improvements have been made not only in brain penetrance and in vivo activity in preclinical models for anxiety, depression and irritable bowel syndrome, but also in structural diversity for these compounds. Clinical data for R-121919 (NBI-30775; Neurocrine Biosciences Inc) raises the expectation that safe and potent CRF antagonists might be useful as drugs for the treatment of human diseases.

Design, synthesis, and biological evaluation of 1,2,3,7-tetrahydro-6h-purin-6-one and 3,7-dihydro-1h-purine-2,6-dione derivatives as corticotropin-releasing factor(1) receptor antagonists.

A growing body of evidence suggests that CRF(1) receptor antagonism offers considerable therapeutic potential in the treatment of diseases resulting from elevated levels of CRF, such as anxiety and depression. A series of novel 1,2,3,7-tetrahydro-6H-purin-6-one and 3,7-dihydro-1H-purine-2,6-dione derivatives was synthesized and evaluated as corticotropin releasing factor-1 (CRF(1)) receptor antagonists. Compounds within this series, represented by compound 12d (IC(50) = 5.4 nM), were found to be highly potent CRF(1) receptor antagonists. In addition, compounds 12d and 12j were determined to be selective CRF(1) antagonists. The synthesis, structure-activity relationships and pharmacokinetic properties of compounds within this series is presented.

Anxiolytic-like effects of the corticotropin-releasing factor1 (CRF1) antagonist DMP904 [4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazolo-[1,5-a]-pyrimidine] administered acutely or chronically at doses occupying central CRF1 receptors in rats.

Corticotropin-releasing factor(1) (CRF(1)) antagonists may be effective in the treatment of anxiety disorders with fewer side effects compared with classic benzodiazepines. The behavioral effects of DMP904 [4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazolo-[1,5-a]-pyrimidine] and its effects on the hypothalamic-pituitary-adrenal (HPA) axis were related to its levels in plasma and estimated occupancy of central CRF(1) receptors. DMP904 (10-30 mg/kg, p.o.) and alprazolam (10 mg/kg, p.o.) increased time spent in open arms of an elevated-plus maze. In addition, acutely or chronically (14 days) administered DMP904 (1.0-30 mg/kg, p.o.) and acute alprazolam (1.0-3.0 mg/kg, p.o.) significantly reduced exit latency in the defensive withdrawal model of anxiety in rats, suggesting that tolerance may not develop to the anxiolytic-like effects of DMP904 in this model of anxiety. Acutely, DMP904 reversed the stress-induced increase in plasma corticosterone levels in defensive withdrawal at doses of 3.0 mg/kg and higher. These doses also resulted in levels of DMP904 in plasma similar to (for anxiolytic-like effects) or 4-fold higher (for effects on the HPA axis) than the in vitro IC(50) value for binding affinity at CRF(1) receptors and greater than 50% occupancy of CRF(1) receptors. Unlike alprazolam, DMP904 did not produce sedation, ataxia, or chlordiazepoxide-like subjective effects (as measured by locomotor activity, rotorod performance, and chlordiazepoxide discrimination assays, respectively) at doses at least 3-fold higher than anxiolytic-like doses. In conclusion, anxiolytic-like effects and effects on the stress-activated HPA axis of DMP904 in the defensive withdrawal model of anxiety required 50% or greater occupancy of central CRF(1) receptors. This level of CRF(1) receptor occupancy resulted in fewer motoric side effects compared with classic benzodiazepines.