Triple reuptake inhibitors as antidepressants

Design and synthesis of 4-benzylpiperidine carboxamides as dual serotonin and norepinephrine reuptake inhibitors

A series of 4-benzylpiperidine carboxamides were designed and synthesized, and tested for their dual (serotonin and norepinephrine) reuptake inhibition. The synthesis of 4-benzylpiperidine carboxamides involved two main steps: amidation and substitution. Derivatives with 3 carbon linker displayed better activity than with 2 carbon linker. 4-Biphenyl- and 2-naphthyl-substituted derivatives 7e and 7j showed greater dual reuptake inhibition than standard drug venlafaxine HCl.

Learning from the past and looking to the future: Emerging perspectives for improving the treatment of psychiatric disorders

Modern neuropsychopharmacology commenced in the 1950s with the serendipitous discovery of first-generation antipsychotics and antidepressants which were therapeutically effective yet had marked adverse effects. Today, a broader palette of safer and better-tolerated agents is available for helping people that suffer from schizophrenia, depression and other psychiatric disorders, while complementary approaches like psychotherapy also have important roles to play in their treatment, both alone and in association with medication. Nonetheless, despite considerable efforts, current management is still only partially effective, and highly-prevalent psychiatric disorders of the brain continue to represent a huge personal and socio-economic burden. The lack of success in discovering more effective pharmacotherapy has contributed, together with many other factors, to a relative disengagement by pharmaceutical firms from neuropsychiatry. Nonetheless, interest remains high, and partnerships are proliferating with academic centres which are increasingly integrating drug discovery and translational research into their traditional activities. This is, then, a time of transition and an opportune moment to thoroughly survey the field. Accordingly, the present paper, first, chronicles the discovery and development of psychotropic agents, focusing in particular on their mechanisms of action and therapeutic utility, and how problems faced were eventually overcome. Second, it discusses the lessons learned from past successes and failures, and how they are being applied to promote future progress. Third, it comprehensively surveys emerging strategies that are (1), improving our understanding of the diagnosis and classification of psychiatric disorders; (2), deepening knowledge of their underlying risk factors and pathophysiological substrates; (3), refining cellular and animal models for discovery and validation of novel therapeutic agents; (4), improving the design and outcome of clinical trials; (5), moving towards reliable biomarkers of patient subpopulations and medication efficacy and (6), promoting collaborative approaches to innovation by uniting key partners from the regulators, industry and academia to patients. Notwithstanding the challenges ahead, the many changes and ideas articulated herein provide new hope and something of a framework for progress towards the improved prevention and relief of psychiatric and other CNS disorders, an urgent mission for our Century.

On 'polypharmacy' and multi-target agents, complementary strategies for improving the treatment of depression: a comparative appraisal

Major depression is a heterogeneous disorder, both in terms of symptoms, ranging from anhedonia to cognitive impairment, and in terms of pathogenesis, with many interacting genetic, epigenetic, developmental and environmental causes. Accordingly, it seems unlikely that depressive states could be fully controlled by a drug possessing one discrete mechanism of action and, in the wake of disappointing results with several classes of highly selective agent, multi-modal treatment concepts are attracting attention. As concerns pharmacotherapy, there are essentially two core strategies. First, multi-target antidepressants that act via two or more complementary mechanisms and, second, polypharmacy, which refers to co-administration of two distinct drugs, usually in separate pills. Both multi-target agents and polypharmacy ideally couple a therapeutically unexploited action to a clinically established mechanism in order to enhance efficacy, moderate side-effects, accelerate onset of action and treat a broader range of symptoms. The melatonin MT1/MT2 agonist and 5-HT(2C) antagonist, agomelatine, which is effective in the short- and long-term treatment of depression, exemplifies the former approach, while evidence-based polypharmacy is illustrated by the adjunctive use of second-generation antipsychotics with serotonin reuptake inhibitors for treatment of resistant depression. Histone acetylation and methylation, ghrelin signalling, inflammatory modulators, metabotropic glutamate-7 receptors and trace amine-associated-1 receptors comprise attractive substrates for new multi-target and polypharmaceutical strategies. The present article outlines the rationale underpinning multi-modal approaches for treating depression, and critically compares and contrasts the pros and cons of established and potentially novel multi-target vs. polypharmaceutical treatments. On balance, the former appear the most promising for the elaboration, development and clinical implementation of innovative concepts for the more effective management of depression.

Dual- and triple-acting agents for treating core and co-morbid symptoms of major depression: novel concepts, new drugs

The past decade of efforts to find improved treatment for major depression has been dominated by genome-driven programs of rational drug discovery directed toward highly selective ligands for nonmonoaminergic agents. Selective drugs may prove beneficial for specific symptoms, for certain patient subpopulations, or both. However, network analyses of the brain and its dysfunction suggest that agents with multiple and complementary modes of action are more likely to show broad-based efficacy against core and comorbid symptoms of depression. Strategies for improved multitarget exploitation of monoaminergic mechanisms include triple inhibitors of dopamine, serotonin (5-HT) and noradrenaline reuptake, and drugs interfering with feedback actions of monoamines at inhibitory 5-HT(1A), 5-HT(1B) and possibly 5-HT(5A) and 5-HT(7) receptors. Specific subsets of postsynaptic 5-HT receptors mediating antidepressant actions are under study (e.g., 5-HT(4) and 5-HT(6)). Association of a clinically characterized antidepressant mechanism with a nonmonoaminergic component of activity is an attractive strategy. For example, agomelatine (a melatonin agonist/5-HT(2C) antagonist) has clinically proven activity in major depression. Dual neurokinin(1) antagonists/5-HT reuptake inhibitors (SRIs) and melanocortin(4) antagonists/SRIs should display advantages over their selective counterparts, and histamine H(3) antagonists/SRIs, GABA(B) antagonists/SRIs, glutamatergic/SRIs, and cholinergic agents/SRIs may counter the compromised cognitive function of depression. Finally, drugs that suppress 5-HT reuptake and blunt hypothalamo-pituitary-adrenocorticotrophic axis overdrive, or that act at intracellular proteins such as GSK-3beta, may abrogate the negative effects of chronic stress on mood and neuronal integrity. This review discusses the discovery and development of dual- and triple-acting antidepressants, focusing on novel concepts and new drugs disclosed over the last 2 to 3 years.

Effect of DOV 102,677 on the volitional consumption of ethanol by Myers' high ethanol-preferring rat

BACKGROUND

Inhibitors of monoamine neurotransmitter transporters are well established as antidepressants. However, the evidence that single (serotonin) or dual (serotonin-norepinephrine) neurotransmitter uptake inhibitors can treat ethanol abuse, either as a comorbidity with depression or as a separate entity, is inconsistent. Drugs that have, in addition, the ability to inhibit dopamine uptake may have an advantage in the treatment of alcohol abuse. Therefore, the inhibitor of norepinephrine, serotonin and dopamine uptake, DOV 102,677, was tested for its effects on the volitional consumption of ethanol by an ethanol-preferring rat strain.

METHODS

Myers' high ethanol-preferring rats were screened by a 10-day, 3 to 30% step-up test and then given free access to the preferred concentration of ethanol in a 3-bottle choice task. Consumption of ethanol (g/kg), water, food, and body weight were measured daily during a 3-day predrug treatment period, a 3-day treatment period, and a 3-day posttreatment period. Additional Sprague-Dawley rats were observed for 24 hours for the behavioral effects of 2.0 mg/kg s.c. reserpine after a 30-minute pretreatment with different doses of DOV 102,677.

RESULTS

The triple monoamine uptake inhibitor DOV 102,677 dose-dependently decreased the volitional consumption of ethanol by as much as 71.2% (20 mg/kg i.p., b.i.d.) over 3 days of administration. This effect carried over into the posttreatment period. Similarly, the proportion of ethanol to total fluids consumed declined by 66.2% (20 mg/kg s.c., b.i.d.), while food consumption and body weight were unaltered. In contrast, amperozide (2 mg/kg i.p., b.i.d.) suppressed the amount of ethanol consumed by 56%, while naltrexone (5 mg/kg i.p., b.i.d.) was without effect. DOV 102,677 (40 mg/kg s.c.) inhibited reserpine-induced akinesia and ptosis, but not hypothermia in Sprague-Dawley rats, consistent with its transient inhibition of serotonin transport, and more long-lived inhibition of norepinephrine and dopamine uptake.

CONCLUSIONS

DOV 102,677 significantly decreased the volitional consumption of ethanol with minimal alterations in the intake of food or on body weight in an ethanol-preferring rat strain, suggesting that triple reuptake inhibitors may find utility in treating alcohol abuse.

Triple uptake inhibitors: therapeutic potential in depression and beyond

Drugs that interfere with the uptake and/or metabolism of biogenic amines have been used to treat depression for > 4 decades. Early medications such as tricyclic antidepressants and monoamine oxidase inhibitors are effective but possess many side effects that limit their usefulness. Selective serotonin reuptake inhibitors (SSRIs) or selective noradrenaline reuptake inhibitors (SNRIs) are the results of rational design to find drugs that are as effective as the tricyclic antidepressants, but with more selectivity towards a single monoamine transporter. The SSRI class of drugs, which includes fluoxetine, paroxetine and sertraline, were previously viewed as the agents of choice for treating major depression. Recently, inhibitors of both serotonin and noradrenaline uptake ('dual uptake inhibitors'; SSRI/SNRI such as venlafaxine, duloxetine and milnacipran) have gained acceptance in the market. However, neither the SSRIs nor the SSRI/SNRI are fully satisfactory due to a delayed onset of action, low rate of response and side effect that can affect compliance. An important recent development has been the emergence of the triple uptake inhibitors (SSRI/SNRI/selective dopamine reuptake inhibitor), which inhibit the uptake of all three neurotransmitters that are most closely linked to depression: serotonin, noradrenaline and dopamine. Preclinical studies and clinical trials indicate that a drug inhibiting the uptake of all three of these neurotransmitters could produce a more rapid onset of action and possess greater efficacy than traditional antidepressants. This review discusses the evolution of biogenic amine-based therapies, the emerging strategies involved in the design and synthesis of novel triple uptake inhibitors as antidepressants and the therapeutic potential of triple uptake inhibitors.