Resolving the onset of antidepressants' clinical actions: critical for clinical practice and new drug development

Hamilton depression rating subscales to predict antidepressant treatment outcome in the early course of treatment

BACKGROUND

Hamilton depression rating scale (HAMD) subscales provide an economic alternative for the full scale; however, their ability to detect onset of improvement in the early course of treatment (EI) has not yet been researched. The present study investigated in patients with major depression (MD) whether the subscales are a comparable option to predict treatment remission in the early course of treatment.

METHODS

Based on data from 210 MD patients of a 6-week randomised, placebo-controlled trial comparing mirtazapine (MIR) and paroxetine (PAR), the discriminative and predictive validity of EI for (stable) remission at treatment end was evaluated for seven subscales and the HAMD17 in the total and in treatment subgroups (MIR vs. PAR). Receiver operating characteristics (ROC) curves (at week 2) and the Clinical Global Impression scales (CGI) (at study endpoint) were used to validate the 20% EI criterion for the subscales.

RESULTS

Only the Evans6 and Toronto7 subscale had almost the same predictive value as the HAMD17 (e.g., sensitivities stable remission Evans6/Toronto7: 96/95% vs. 96% HAMD17). The optimal cut-off for EI to predict remission was just below 20% for most subscales and slightly over 20% for stable remission.

LIMITATIONS

Study sample representativeness, non-independence of subscales, missing external validation criterion, lack of control group.

CONCLUSIONS

The Evans6 and Toronto7 subscales are valuable alternatives in situations, where economic aspects play a larger role. A sum score reduction of ≥20% as definition for EI seems also appropriate for the HAMD subscales, in the total as well as in the antidepressant subgroups.

Allopregnanolone regulates neurogenesis and depressive/anxiety-like behaviour in a social isolation rodent model of chronic stress

Chronic stress has been implicated as a causal factor in depression and anxiety, and is associated with neuroendocrine dysfunction and impaired hippocampal neurogenesis. The neurosteroid allopregnanolone (3α,5α-THP; ALLO) has been shown to be reduced in depressed patients. ALLO is "stress responsive" and plays a major role in regulating hypothalamic-pituitary-adrenal (HPA) axis function. We propose that reduced ALLO levels following chronic stress leads to HPA hyperactivity due to diminished ALLO regulation. This will result in increased glucocorticoid levels and reduced BDNF expression, leading to impaired hippocampal neurogenesis and the precipitation of depression/anxiety. To investigate this, chronic stress was induced using the social isolation model and depressive/anxiety-like behaviour assessed using the novelty-suppressed feeding test and forced-swim test. The social isolation model was associated with a significant reduction in endogenous ALLO levels and a depressive/anxiety-like behavioural profile. When exogenous ALLO was administered from the onset of isolation it prevented the development of depressive/anxiety-like behaviours and impairment of hippocampal neurogenesis. When treatment was initiated following six weeks of social isolation, behavioural profile was restored and deficits in BDNF and neurogenesis were not observed. Supporting our hypothesis we observed that socially isolated animals exhibited reduced HPA responsiveness, which was either prevented or normalised with ALLO treatment. Combined, these results indicate that administration of exogenous ALLO either during or following a period of chronic stress can prevent or normalise HPA dysfunction and impairment of hippocampal neurogenesis respectively, precluding the establishment of depressive/anxiety-like behaviours. ALLO may therefore provide a novel therapeutic target for the treatment of depression/anxiety.

The importance of early symptom relief in antidepressant treatment: focus on agomelatine

Antidepressants were traditionally considered to have delayed onset of action, and clinical opinion often stated that patients may not experience noticeable improvement for 4-6 weeks. Recent studies have shown, however, that antidepressants have more rapid onset of effect, within 1-2 weeks, and that this early response may be associated with later sustained response. Moreover, there is emerging evidence that some medications may have faster onset of therapeutic effect than others. The new antidepressant agomelatine, with its novel pharmacological profile as an agonist at melatonergic (MT(1) and MT(2)) receptors and antagonist at 5-HT(2C) receptors, has in several studies produced earlier symptom improvement than comparator selective serotonin reuptake inhibitors and serotonin-noradrenaline reuptake inhibitors. In particular, beneficial effects on sleep and daytime functioning are noticeable as early as the first week of treatment. These therapeutic benefits may, in part, be related to its regulatory effects on circadian and sleep- wake cycles. Agomelatine therefore combines early symptom relief with a favorable side-effect profile and short-term and long-term antidepressant efficacy. These properties suggest that agomelatine can be considered a first-line treatment for patients with major depression.

Oppositional effects of serotonin receptors 5-HT1a, 2, and 2c in the regulation of adult hippocampal neurogenesis

Serotonin (5-HT) appears to play a major role in controlling adult hippocampal neurogenesis and thereby it is relevant for theories linking failing adult neurogenesis to the pathogenesis of major depression and the mechanisms of action of antidepressants. Serotonergic drugs lacked acute effects on adult neurogenesis in many studies, which suggested a surprisingly long latency phase. Here we report that the selective serotonin reuptake inhibitor fluoxetine, which has no acute effect on precursor cell proliferation, causes the well-described increase in net neurogenesis upon prolonged treatment partly by promoting the survival and maturation of new postmitotic neurons. We hypothesized that this result is the cumulative effect of several 5-HT-dependent events in the course of adult neurogenesis. Thus, we used specific agonists and antagonists to 5-HT1a, 2, and 2c receptor subtypes to analyze their impact on different developmental stages. We found that 5-HT exerts acute and opposing effects on proliferation and survival or differentiation of precursor cells by activating the diverse receptor subtypes on different stages within the neuronal lineage in vivo. This was confirmed in vitro by demonstrating that 5-HT1a receptors are involved in self-renewal of precursor cells, whereas 5-HT2 receptors effect both proliferation and promote neuronal differentiation. We propose that under acute conditions 5-HT2 effects counteract the positive proliferative effect of 5-HT1a receptor activation. However, prolonged 5-HT2c receptor activation fosters an increase in late-stage progenitor cells and early postmitotic neurons, leading to a net increase in adult neurogenesis. Our data indicate that serotonin does not show effect latency in the adult dentate gyrus. Rather, the delayed response to serotonergic drugs with respect to endpoints downstream of the immediate receptor activity is largely due to the initially antagonistic and un-balanced action of different 5-HT receptors.

Efficacy and safety of agomelatine in the treatment of major depressive disorder: a multicenter, randomized, double-blind, placebo-controlled trial

In this 8-week double-blind multicenter trial, we evaluated the efficacy and safety of 2 fixed doses of agomelatine in patients with moderate to severe major depressive disorder. Primary efficacy variable was the change in 17-item Hamilton Depression Rating Scale (HAM-D17) total score from baseline to week 8/end of treatment. Secondary efficacy assessment compared the improvements in clinical response and remission (HAM-D17), Clinical Global Impression--Improvement Score, Clinical Global Impression--Severity Score, Hospital Anxiety and Depression (HAD), sleep (Leeds Sleep Evaluation Questionnaire), disability (Sheehan Disability Scale), and overall Quality of Life in Depression Scale between the agomelatine and placebo groups. Eligible patients (n = 511; baseline mean HAM-D17 score = 27.0) were randomized (1:1:1) to once-daily agomelatine, 25 mg; agomelatine, 50 mg; or placebo. Agomelatine 50 mg provided a statistically significant improvement in HAM-D17 score from first baseline visit through week 8 compared with placebo (week 8 treatment difference, 2.5; P = 0.004), whereas agomelatine 25 mg did not show (P = 0.505) a significant improvement. Treatment differences for all secondary efficacy variables were also statistically significant for agomelatine 50 mg versus placebo: Clinical Global Impression--Improvement (P = 0.012); Clinical Global Impression--Severity difference (P = 0.003); improvement in HAD total score, 2.2 (P = 0.014); patients' ability to get sleep (P < 0.001); quality of sleep (P = 0.002). Both doses of agomelatine were well tolerated relative to placebo. However, clinically notable transient aminotransferase elevations were observed in 4.5% of the patients in the agomelatine 50 mg group. The results showed significant antidepressant efficacy of agomelatine 50 mg/d, including a positive effect on sleep compared with placebo in outpatients with moderate to severe major depressive disorder.

Rethinking depression and the actions of antidepressants: uncovering the links between the neural and behavioral elements

Despite major strides in the understanding of mechanisms of antidepressant drug action, few, if any, widely applicable drug treatments with new mechanisms have been developed since the selective serotonin reuptake inhibitors in the late 1970's. One factor that may contribute to this lack of advance is reliance on a set of flawed assumptions that have guided most new drug development over the past quarter century. These assumptions have been particularly deleterious to the development of treatments with mechanisms distinctly different from currently approved treatments. One such assumption is that antidepressant actions on clinical aspects are delayed for several weeks. We review the results of studies on time to improvement and describe two collaborative, multidisciplinary studies during this period which employed a behavioral component model for assessment of change, as an alternative to the conventional "diagnostic-specific" research model. These studies incorporated a novel neurobehavioral framework for describing depressive episodes. The studies indicated that (1) depressive states are comprised of relatively independent and somewhat opposed behavioral and emotional components of anxiety-agitation and depression-retardation, coexisting with a third dimension, hostility, all of which might indicate some degree of mixed state phenomenology, (2) drugs selectively targeted at serotonergic and noradrenergic systems have differing profiles of impact on the behavioral dimensions of depressive states and (3) the sequence of behavioral improvements initiated by pharmacodynamically different drugs also differ. In the aggregate these consistent observations provide the basis for a new paradigm on the nature of major depression. The proposition links drug-induced neural and behavioral changes of antidepressants with prediction of clinical outcome based on early response. We submit that the proposed approach may bring about a new paradigm for improving behavioral technology and design of studies capable of identifying drugs with novel properties and rapid onset of improvement, while avoiding some problematic constructs in past biological research on depression.

Differential effects of chronic antidepressant treatment on shuttle box escape deficits induced by uncontrollable stress

RATIONALE

The transient behavioral deficit produced in rodents by typical learned helplessness (LH) procedures limits the utility of LH in identifying the therapeutic mechanisms associated with chronic antidepressant administration. In addition, LH procedures do not differentiate between different antidepressant classes as observed in the forced swim test.

OBJECTIVES

To produce both a long lasting and antidepressant reversible behavioral deficit in a modified LH procedure that administers inescapable shock (IS) in the same operant chamber used for shuttle box escape testing.

RESULTS

A single IS session produced a robust increase in the number of escape failures (FR-2 escape contingency) that endured for at least 21 days. This escape deficit was reversed by desipramine (24 mg/kg/day, 6 days) at the first shuttle box session. Fluoxetine (5 mg/kg/day, 6 and 21 days) improved escape performance only after repeated test sessions. In contrast, fluoxetine (5 mg/kg/day, 21 days) completely reversed the first shuttle box test escape deficit induced by exposure to a chronic unpredictable stress procedure devoid of shocks or exposure to operant chambers. These differential drug effects may be due to the presence or absence of contextual cues during escape testing. Repeated re-exposure to the IS context enhanced the FR-2 escape deficit.

CONCLUSIONS

These data suggest that performing escape testing and IS in the same environment improves the preclinical modeling of the time-dependency and behavioral pattern of antidepressant response observed clinically. Additionally, contextual information associated with the IS environment modulates escape performance and may interact differentially with discrete antidepressant classes.

Time to response for duloxetine 60 mg once daily versus placebo in elderly patients with major depressive disorder

BACKGROUND

Rapid response to antidepressant therapy is desirable and may be particularly critical in elderly patients with major depressive disorder (MDD).

METHODS

Findings are based on post-hoc analyses from a double-blind trial of elderly patients with MDD > or = 65 years, randomly assigned 2:1 to duloxetine 60 mg QD (N = 207) or placebo (N = 104) for 8 weeks. Depression and pain measures included the Geriatric Depression Scale (GDS), 17-item Hamilton Depression Scale (HAMD17), CGI-Severity, and Visual Analog Scale (VAS) for overall pain. The time to response and remission for duloxetine compared with placebo was evaluated using Cox proportional hazards (PH) modeling, Kaplan-Meier estimation, and categorical repeated measures analysis.

RESULTS

Significant improvements of estimated HAMD17 response and remission rates for duloxetine started at week 2 (P = 0.022 and P = 0.033, respectively). Time to HAMD17 response and remission were significantly shorter for duloxetine versus placebo (P 0.10 for all PH treatment-by-age interactions). The placebo-referenced duloxetine HR for time to 50% reduction in overall pain was 1.75 (P = 0.024) for patients with moderate to severe pain.

CONCLUSION

Duloxetine demonstrated a faster time to antidepressant response and improvement in self-reported pain as compared with placebo. CLINICAL TRIAL REGISTRY NUMBER FOR THIS STUDY: NCT00062673, at www.clinicaltrials.gov.