Antidepressant drugs for narcolepsy

Long-term use of pitolisant to treat patients with narcolepsy: Harmony III Study

Study Objectives

To asses the long-term safety and efficacy of pitolisant, an histamine H3-receptor antagonist, on narcolepsy.

Methods

This open-label, single-arm, pragmatic study, recruited adult patients with narcolepsy and Epworth Sleepiness Scale (ESS) score ≥12. After a titration period, patients were treated for up to 1 year with oral pitolisant once-a-day at up to 40 mg. Concomitant stimulants and anti-cataplectic agents were allowed. The primary endpoint was safety; secondary endpoints included ESS, cataplexy, and other diary parameters.

Results

Patients (n = 102, 75 with cataplexy) received pitolisant, for the first time in 73 of them. Sixty-eight patients (51 with cataplexy) completed the 12-month treatment. Common treatment-emergent adverse events were headache (11.8% of patients), insomnia (8.8%), weight gain (7.8%), anxiety (6.9%), depressive symptoms (4.9%), and nausea (4.9%). Seven patients had a serious adverse effect, unrelated to pitolisant except for a possibly related miscarriage. One-third of patients stopped pitolisant, mostly (19.6%) for insufficient benefit. ESS score decreased by 4.6 ± 0.6. Two-thirds of patients completing the treatment were responders (ESS ≤ 10 or ESS decrease ≥ 3), and one third had normalized ESS (≤10). Complete and partial cataplexy, hallucinations, sleep paralysis, and sleep attacks were reduced by 76%, 65%, 54%, 63%, and 27%, respectively. Pitolisant as monotherapy (43% of patients) was better tolerated and more efficacious on ESS than on add-on, but efficacy was maintained in this last case.

Conclusions

Long-term safety and efficacy of pitolisant on daytime sleepiness, cataplexy, hallucinations, and sleep paralysis is confirmed.

Multiple treatment comparison in narcolepsy: a network meta-analysis

Study Objectives

Randomized controlled trials (RCTs) that compared the safety and efficacy of medical treatments for narcolepsy were analyzed using network meta-analysis.

Methods

The RCTs in narcolepsy were searched. Network meta-analysis compared efficacy and safety of multiple treatments, multi-arm studies, and multi-criteria treatment decisions, based on a random model that assumed heterogeneity between studies, with corrections for multi-arm studies.

Results

Fourteen RCTs, three drug treatments, and six doses were identified: sodium oxybate (6 and 9 g/d), modafinil (between 200 and 400 mg/d), and pitolisant (up to 20 and up to 40 mg/d). Significant heterogeneity (>50%) between studies was found in 12/14 studies for almost all endpoints, but between-design consistency was present. For ESS and MWT, sodium oxybate 9 g/d, modafinil, and pitolisant up to 40 mg/d had similar efficacy. Pitolisant 40 mg/d and sodium oxybate 9 g/d in two nightly doses had similar efficacy in reducing cataplexy. A good safety profile characterized by a TEAE incidence risk ratio (IRR) <1.5 was found for all the compared treatments, except for sodium oxybate 9 g/d. Although no significant difference was found, Pitolisant 40 mg was shown with the best P scores for the benefit/risk (BR) ratio.

Conclusions

Modafinil (200–400 mg/d), sodium oxybate 9 g/d, and pitolisant up to 40 mg/d had similar efficacy in reducing excessive day time sleepiness. Only sodium oxybate 9 g/d and pitolisant up to 40 mg/d were shown with a comparable beneficial effect on cataplexy. Overall, Pitolisant was found with the best P score on the BR ratio

Clinical Trial Registration

PROSPERO 2017 CRD42017054686. Efficacy, safety, and benefit-risk comparison of alternative treatments in narcolepsy: a network multiple comparisons of treatment meta-analysis. http://www.crd.york.ac.uk/PROSPERO/display_record.php?ID=CRD42017054686.

Safety and efficacy of pitolisant on cataplexy in patients with narcolepsy: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Histaminergic neurons are crucial to maintain wakefulness, but their role in cataplexy is unknown. We assessed the safety and efficacy of pitolisant, a histamine H3 receptor inverse agonist, for treatment of cataplexy in patients with narcolepsy.

METHODS

For this randomised, double-blind, placebo-controlled trial we recruited patients with narcolepsy from 16 sleep centres in nine countries (Bulgaria, Czech Republic, Hungary, Macedonia, Poland, Russia, Serbia, Turkey, and Ukraine). Patients were eligible if they were aged 18 years or older, diagnosed with narcolepsy with cataplexy according to version two of the International Classification of Sleep Disorders criteria, experienced at least three cataplexies per week, and had excessive daytime sleepiness (defined as an Epworth Sleepiness Scale score ≥12). We used a computer-generated sequence via an interactive web response system to randomly assign patients to receive either pitolisant or placebo once per day (1:1 ratio). Randomisation was done in blocks of four. Participants and investigators were masked to treatment allocation. Treatment lasted for 7 weeks: 3 weeks of flexible dosing decided by investigators according to efficacy and tolerance (5 mg, 10 mg, or 20 mg oral pitolisant), followed by 4 weeks of stable dosing (5 mg, 10 mg, 20 mg, or 40 mg). The primary endpoint was the change in the average number of cataplexy attacks per week as recorded in patient diaries (weekly cataplexy rate [WCR]) between the 2 weeks of baseline and the 4 weeks of stable dosing period. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01800045.

FINDINGS

The trial was done between April 19, 2013, and Jan 28, 2015. We screened 117 patients, 106 of whom were randomly assigned to treatment (54 to pitolisant and 52 to placebo) and, after dropout, 54 patients from the pitolisant group and 51 from the placebo group were included in the intention-to-treat analysis. The WCR during the stable dosing period compared with baseline was decreased by 75% (WCR_final=2·27; WCR_baseline=9·15; WCR_{final/baseline}=0·25) in patients who received pitolisant and 38% (WCR_final=4·52; WCR_baseline=7·31; WCR_{final/baseline}=0·62) in patients who received placebo (rate ratio 0·512; 95% CI 0·43-0·60, p<0·0001). Treatment-related adverse events were significantly more common in the pitolisant group than in the placebo group (15 [28%] of 54 vs 6 [12%] of 51; p=0·048). There were no serious adverse events, but one case of severe nausea in the pitolisant group. The most frequent adverse events in the pitolisant group (headache, irritability, anxiety, and nausea) were mild or moderate except one case of severe nausea. No withdrawal syndrome was detected following pitolisant treatment; one case was detected in the placebo group.

INTERPRETATION

Pitolisant was well tolerated and efficacious in reducing cataplexy. If confirmed in long-term studies, pitolisant might constitute a useful first-line therapy for cataplexy in patients with narcolepsy, for whom there are currently few therapeutic options.

FUNDING

Bioprojet, France.

Central Disorders of Hypersomnolence: Focus on the Narcolepsies and Idiopathic Hypersomnia

The central disorders of hypersomnolence are characterized by severe daytime sleepiness, which is present despite normal quality and timing of nocturnal sleep. Recent reclassification distinguishes three main subtypes: narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia (IH), which are the focus of this review. Narcolepsy type 1 results from loss of hypothalamic hypocretin neurons, while the pathophysiology underlying narcolepsy type 2 and IH remains to be fully elucidated. Treatment of all three disorders focuses on the management of sleepiness, with additional treatment of cataplexy in those patients with narcolepsy type 1. Sleepiness can be treated with modafinil/armodafinil or sympathomimetic CNS stimulants, which have been shown to be beneficial in randomized controlled trials of narcolepsy and, quite recently, IH. In those patients with narcolepsy type 1, sodium oxybate is effective for the treatment of both sleepiness and cataplexy. Despite these treatments, there remains a subset of hypersomnolent patients with persistent sleepiness, in whom alternate therapies are needed. Emerging treatments for sleepiness include histamine H3 antagonists (eg, pitolisant) and possibly negative allosteric modulators of the gamma-aminobutyric acid-A receptor (eg, clarithromycin and flumazenil).

Is suvorexant a better choice than alternative hypnotics?

Suvorexant is a novel dual orexin receptor antagonist (DORA) newly introduced in the U.S. as a hypnotic, but no claim of superiority over other hypnotics has been offered.  The manufacturer argued that the 5 and 10 mg starting doses recommended by the FDA might be ineffective.  The manufacturer's main Phase III trials had not even included the 10 mg dosage, and the 5 mg dosage had not been tested at all in registered clinical trials at the time of approval.  Popular alternative hypnotics may be similarly ineffective, since the FDA has also reduced the recommended doses for zolpidem and eszopiclone.  The "not to exceed" suvorexant dosage of 20 mg does slightly increase sleep.  Because of slow absorption, suvorexant has little effect on latency to sleep onset but some small effect in suppressing wakening after sleep onset and in improving sleep efficiency. The FDA would not approve the manufacturer's preferred 40 mg suvorexant dosage, because of concern with daytime somnolence, driving impairment, and possible narcolepsy-like symptoms.  In its immediate benefits-to-risks ratio, suvorexant is unlikely to prove superior to currently available hypnotics—possibly worse—so there is little reason to prefer over the alternatives this likely more expensive hypnotic less-tested in practice.  Associations are being increasingly documented relating hypnotic usage with incident cancer, with dementia risks, and with premature death.  There is some basis to speculate that suvorexant might be safer than alternative hypnotics in terms of cancer, dementia, infections, and mortality.  These safety considerations will remain unproven speculations unless adequate long-term trials can be done that demonstrate suvorexant advantages.

Treatment paradigms for cataplexy in narcolepsy: past, present, and future

Cataplexy is defined as episodes of sudden loss of voluntary muscle tone triggered by emotions generally lasting <2 minutes. Cataplexy is most commonly associated with and considered pathognomonic for narcolepsy, a sleep disorder affecting ~0.05% of the general population. Knowledge of the pathophysiology of cataplexy has advanced through study of canine, murine, and human models. It is now generally considered that loss of signaling by hypothalamic hypocretin/orexin-producing neurons plays a key role in the development of cataplexy. Although the cause of hypocretin/orexin neuron loss in narcolepsy with cataplexy is unknown, an autoimmune etiology is widely hypothesized. Despite these advances, a literature review shows that treatment of cataplexy remains limited. Multiple classes of antidepressants have been commonly used off-label for cataplexy in narcolepsy and are suggested for this use in expert consensus guidelines based on traditional practice, case reports, and small trials. However, systematic research evidence supporting antidepressants for cataplexy is lacking. The single pharmacotherapy indicated for cataplexy and the guideline-recommended first-line treatment in Europe and the US is sodium oxybate, the sodium salt of gamma-hydroxybutyrate. Clinical trial evidence of its efficacy and safety in cataplexy is robust, and it is hypothesized that its therapeutic effects may occur through gamma-aminobutyric acid receptor type B-mediated effects at noradrenergic, dopaminergic, and thalamocortical neurons. Additional possible mechanisms for cataplexy therapy suggested by preliminary research include antagonism of the histamine H3 autoreceptor with pitolisant and intravenous immunoglobulin therapy for amelioration of the presumed autoimmune-mediated hypocretin/orexin cell loss. Further research and development of therapeutic approaches to cataplexy are needed.