Elsevier

Neuropharmacology

Volume 77, February 2014, Pages 131-144
Neuropharmacology

LY2456302 is a novel, potent, orally-bioavailable small molecule kappa-selective antagonist with activity in animal models predictive of efficacy in mood and addictive disorders

https://doi.org/10.1016/j.neuropharm.2013.09.021Get rights and content

Highlights

  • Noncanonical pharmacokinetic properties have hampered kappa antagonist development.

  • Chemistry improvements identified novel compounds with kappa antagonist activity.

  • LY2456302 exhibits canonical pharmacokinetic properties and kappa selectivity in vivo.

  • LY2456302 has antidepressant-like properties and reduces ethanol self-administration.

  • LY2456302 is a novel research tool with favorable properties for clinical development.

Abstract

Kappa opioid receptors and their endogenous neuropeptide ligand, dynorphin A, are densely localized in limbic and cortical areas comprising the brain reward system, and appear to play a key role in modulating stress and mood. Growing literature indicates that kappa receptor antagonists may be beneficial in the treatment of mood and addictive disorders. However, existing literature on kappa receptor antagonists has used extensively JDTic and nor-BNI which exhibit long-lasting pharmacokinetic properties that complicate experimental design and interpretation of results. Herein, we report for the first time the in vitro and in vivo pharmacological profile of a novel, potent kappa opioid receptor antagonist with excellent selectivity over other receptors and markedly improved drug-like properties over existing research tools. LY2456302 exhibits canonical pharmacokinetic properties that are favorable for clinical development, with rapid absorption (tmax: 1–2 h) and good oral bioavailability (F = 25%). Oral LY2456302 administration selectively and potently occupied central kappa opioid receptors in vivo (ED50 = 0.33 mg/kg), without evidence of mu or delta receptor occupancy at doses up to 30 mg/kg. LY2456302 potently blocked kappa-agonist-mediated analgesia and disruption of prepulse inhibition, without affecting mu-agonist-mediated effects at doses >30-fold higher. Importantly, LY2456302 did not block kappa-agonist-induced analgesia one week after administration, indicating lack of long-lasting pharmacodynamic effects. In contrast to the nonselective opioid antagonist naltrexone, LY2456302 produced antidepressant-like effects in the mouse forced swim test and enhanced the effects of imipramine and citalopram. LY2456302 reduced ethanol self-administration in alcohol-preferring (P) rats and, unlike naltrexone, did not exhibit significant tolerance upon 4 days of repeated dosing. LY2456302 is a centrally-penetrant, potent, kappa-selective antagonist with pharmacokinetic properties favorable for clinical development and activity in animal models predictive of efficacy in mood and addictive disorders.

Introduction

Major depression, characterized by negative mood, reduced motivation, and sometimes anhedonia and decreased energy, affects nearly 5% of people worldwide each year. Current antidepressants work well for some patients, but ∼60% suffer from unresolved residual symptoms or inadequate treatment response (Thase et al., 2001). As a result, some patients may abuse or misuse alcohol or other drugs in an attempt to reduce their depressive symptoms, often termed “self-medication” (Bolton et al., 2009). A recent study estimated that 16% of depressed patients also have a diagnosable addiction disorder (Sher et al., 2008). Such comorbidity puts patients at greater risk. Comorbid substance use in depressed patients is associated with greater symptom severity, inadequate treatment response, poorer prognosis (including increased risk of suicide), and persistence of depressive symptoms (Thase et al., 2001, Blanco et al., 2012). Therefore, a tremendous need exists for pharmacotherapies effective in treating both depressive symptoms and alcohol dependence.

Kappa opioid receptors and their endogenous neuropeptide ligand, dynorphin A, are densely localized in limbic and cortical areas comprising the brain reward and stress systems, and play a key role in modulating neurotransmission in these areas (Mansour et al., 1987, Mansour et al., 1994, Margolis et al., 2006). In preclinical models, stress produces a prodepressive phenotype that is believed to be associated with the activation of kappa opioid receptors and subsequent downstream signaling events (Pliakas et al., 2001, Newton et al., 2002, McLaughlin et al., 2003, Shirayama et al., 2004, Land et al., 2008). Consistent with this hypothesis, kappa receptor agonists produce anxiogenic- and prodepressive-like effects in animals and humans (Pfeiffer et al., 1986, Todtenkopf et al., 2004; but see also Harden et al., 2012), whereas kappa receptor antagonists reliably exhibit antidepressant-like effects in animal models predictive of efficacy in the domains of mood and affect (Mague et al., 2003, Land et al., 2009, Carr et al., 2010). Unfortunately, there have been no reports of selective kappa receptor antagonists administered in clinical populations.

Kappa-selective antagonists also reduce ethanol intake and reinstatement in a number of preclinical paradigms (Deehan et al., 2012, Walker and Koob, 2008). While nonselective opioid antagonists such as naltrexone, an FDA-approved medication for alcohol dependence, are efficacious in animal models of alcoholism, they do not produce reliable antidepressant- or anxiolytic-like effects in animals or humans, likely due to functional opposition between mu and kappa receptors (Margolis et al., 2003, Spanagel et al., 1992). Similarly, antidepressants are weakly and inconsistently effective at reducing alcohol consumption in depressed patients with comorbid addictive disorders (Kranzler et al., 2006, Pettinati et al., 2010). Because kappa antagonists demonstrate efficacy in animal models predictive of efficacy in mood and addictive disorders, they have the potential to treat depressed patients with comorbid alcohol dependence.

Molecules targeting specific biological mechanisms are powerful tools for elucidating biological function. Most current knowledge of the kappa opioid system comes from studies on the prototypical antagonists, norbinaltorphimine (nor-BNI) and (3R)-7-Hydroxy-N-{(1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl}-1,2,3,4-tetrahydro-3-isoquinoline-carboxamide (JDTic), which have unusual pharmacokinetic properties, including delayed onset of centrally-mediated effects (24–48 h) and very long duration of pharmacodynamic effects (28+ days; Munro et al., 2012, Patkar et al., 2013), that complicate research design and interpretation of the results. Long-duration activity of an antagonist can result in biological consequences that are different from that of short-term receptor blockade; differential biochemical modifications occur at the receptor level and at down-stream targets as a result of prolonged gating of agonist from the receptor. In order to expand and crystallize our current understanding of the biological basis of kappa opioid receptor function, the purpose of the present experiments was two-fold: first, to pharmacologically characterize (S)-3-fluoro4-(4-((2-(3,5-dimethylphenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (LY2456302) as an improved research tool for studying the kappa opioid receptor system; and second, to examine its antidepressant-like effects and its ability to decrease ethanol consumption.

Section snippets

Drugs and reagents

(S)-3-fluoro-4-(4-((2-(3,5-dimethylphenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (LY2456302; Diaz Buezo et al., 2009, Mitch et al., 2011), LY2048978, JDTic, and GR103545 were synthesized at Lilly Research Laboratories. Naltrexone HCl, DAMGO acetate, DPDPE hydrate, naltriben methanesulfonate hydrate, U-69593, morphine sulfate, imipramine HCl, chlordiazepoxide HCl, phencyclidine HCl, and formalin solution (10%, diluted to 5%) were purchased from Sigma Aldrich (St. Louis, MO). LY2456302,

In vitro receptor binding and functional activity

LY2456302 (Fig. 1) was tested in filtration radioligand binding and GTP-γ-35S functional assays using membranes prepared from HEK or CHO cells expressing cloned human mu-, kappa-, and delta-opioid receptor subtypes (Mitch et al., 2011). LY2456302 bound with high affinity to the human kappa opioid receptor with a 30-fold higher affinity over the human mu opioid receptor and 190-fold higher affinity over the human delta opioid receptor (Table 1; Mitch et al., 2011). By comparison, naltrexone had

Discussion

LY2456302 is a structurally-unique, high-affinity, selective antagonist at the kappa opioid receptor (Diaz Buezo et al., 2009, Mitch et al., 2011), with approximately 30- and 200-fold selectivity over mu and delta opioid receptors, respectively, as assessed in in vitro binding and functional assays. LY2456302 had no appreciable affinity at several non-opioid cell surface receptor targets, including monoaminergic, muscarinic, cholinergic, and adrenergic receptors, as well as the central

Funding/conflict of interest

Financial support for the research provided by Eli Lilly and Company. All authors were employees of, and stockholders in, Eli Lilly and Company at the time the experiments were conducted.

Authorship contributions

Participated in research design: Rorick-Kehn, Statnick, Witkin, Kahl, Cramer, Mitch, D McKinzie, Forster.

Conducted experiments: Rorick-Kehn, Crile, Shaw, Sahr, J McKinzie, Eberle, Adams, Li, Kahl, D McKinzie, Forster.

Contributed new reagents or analytic tools: Quimby, Diaz, Jimenez, Pedregal, Mitch, Anderson, D McKinzie.

Performed data analysis: Rorick-Kehn, Crile, Shaw, Sahr, J McKinzie, Eberle, Adams, Li, Kahl, Anderson, Cramer, D McKinzie, Witkin, Forster.

Wrote or contributed to the writing

References (60)

  • R.D. Porsolt et al.

    Immobility induced by forced swimming in rats: effects of agents which modify central catecholamine and serotonin activity

    Eur. J. Pharmacol.

    (1979)
  • H.E. Shannon et al.

    Effects of the I(1) imidazoline/alpha(2)-adrenergic receptor agonist moxonidine in comparison with clonidine in the formalin test in rats

    Pain

    (2000)
  • M.B. Waller et al.

    Induction of dependence on ethanol by free-choice drinking in alcohol-preferring rats

    Pharmacol. Biochem. Behav.

    (1982)
  • T.E. West et al.

    Effects of naltrexone on nucleus accumbens, lateral hypothalamic and ventral tegmental self-stimulation rate-frequency functions

    Brain Res.

    (1988)
  • P.M. Beardsley et al.

    Differential effects of the novel kappa opioid receptor antagonist, JDTic, on reinstatement of cocaine-seeking induced by footshock stressors vs cocaine primes and its antidepressant-like effects in rats

    Psychopharmacology (Berl.)

    (2005)
  • C. Blanco et al.

    Differences among major depressive disorder with and without co-occurring substance use disorders and substance-induced depressive disorder: results from the National Epidemiologic Survey on Alcohol and Related Conditions

    J. Clin. Psychiatry

    (2012)
  • D.L. Braff et al.

    Human studies of prepulse inhibition of startle: normal subjects, patient groups, and pharmacological studies

    Psychopharmacology (Berl.)

    (2001)
  • G.V. Carr et al.

    Antidepressant-like effects of kappa-opioid receptor antagonists in Wistar Kyoto rats

    Neuropsychopharmacology

    (2010)
  • E.H. Chartoff et al.

    Desipramine reduces stress-activated dynorphin expression and CREB phosphorylation in NAc tissue

    Mol. Pharmacol.

    (2009)
  • V.I. Chefer et al.

    Endogenous kappa-opioid receptor systems regulate mesoaccumbal dopamine dynamics and vulnerability to cocaine

    J. Neurosci.

    (2005)
  • T.J. Cicero

    Animal models of alcoholism?

  • G. Di Chiara et al.

    Drugs abused by humans preferentially increase synaptic dopamine concentrations in the mesolimbic system of freely moving rats

    Proc. Natl. Acad. Sci. U. S. A.

    (1988)
  • Diaz Buezo, N., Pedregal-Tercero, C., McKinzie, D., Mitch, C., 2009. Kappa selective opioid receptor antagonist. US...
  • H.J. Edenberg et al.

    A regulatory variation in OPRK1, the gene encoding the kappa-opioid receptor, is associated with alcohol dependence

    Hum. Mol. Genet.

    (2008)
  • M. Fava et al.

    A pilot study of ALKS 5461 (Buprenorphine combined with ALKS 33) in treatment resistant depression

  • J.B. Fitzgerald et al.

    Systems biology and combination therapy in the quest for clinical efficacy

    Nat. Chem. Biol.

    (2006)
  • W.R. Greco et al.

    The search for synergy: a critical review from a response surface perspective

    Pharmacol. Rev.

    (1995)
  • M.T. Harden et al.

    Antidepressive effects of the kappa-opioid receptor agonist salvinorin A in a rat model of anhedonia

    Behav. Pharmacol.

    (2012)
  • C. Harrison

    Opioid receptor blocker shows promise in phase II depression trial

    Nat. Rev. Drug Discov.

    (2013)
  • A.B. Kampov-Polevoy et al.

    P rats develop physical dependence on alcohol via voluntary drinking: changes in seizure thresholds, anxiety, and patterns of alcohol drinking

    Alcoholism – Clin. Exp. Res.

    (2000)
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