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A New Drug for the Treatment of Insomnia: Lemborexant (Dayvigo)

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The Burden of Insomnia

Insomnia is a highly prevalent and debilitating disorder associated with significant functional impairment. A Singapore study conducted by Yeo et al in 1996 places sleep disorder estimates among Singaporeans at 15.3%, a number matched globally across industrialised countries with prevalence rates ranging between 10-50%.

The diagnosis of insomnia is broadly defined by sleep disturbances for at least three nights per week, with consequent daytime impairment arising from sleep difficulty. Chronic insomnia in particular has been shown to be associated with substantial societal costs that result from reduced work productivity, daytime dysfunction and poor health-related quality of life (HR QoL).

Insomnia is both a symptom and a disorder in itself, and warrants a detailed evaluation to ensure the right treatment strategy. Pharmacotherapy can be considered if first-line cognitive behaviour therapy remains ineffectual and must be individualised based on factors such as age, comorbidity, symptom pattern, adverse events, cost and patient preference. 

A New Chemical Entity: Dual Orexin Receptor Antagonist

Medications with regulatory approval for insomnia treatment span multiple classes, tapping on a broad range of neurotransmitter and hormonal targets that regulate the sleep-wake cycle. Notwithstanding, the pharmacotherapy landscape for chronic insomnia remains relatively devoid of safe and effective long-term drug therapies. 

The newest local entrant, oral lemborexant (Dayvigo), received approval by the Health Sciences Authority (HSA) of Singapore, in September 2021 for the treatment of adult patients with insomnia characterised by difficulties with sleep onset and/or sleep maintenance.

Lemborexant is a dual orexin receptor antagonist that inhibits orexin signalling by selectively binding to orexin receptor 1 (hypothesised to suppress rapid eye movement (REM) sleep) and orexin receptor 2 (thought to suppress non-REM and REM sleep). Orexin, which is produced in the hypothalamus, is a neuropeptide that plays a pivotal role in maintaining wakefulness. Unlike most hypnotics, which have widespread central nervous system (CNS) depressant effects, lemborexant has a more targeted action in promoting sleep by suppressing the wake drive. 

Evidence of use

HSA’s approval was based on findings from the SUNRISE clinical development program that comprised two key Phase III studies. Notably, the studies evaluated outcomes using different monitoring and measurement modality settings. Significant subjective and objective improvements in the primary outcome of sleep onset latency was observed in both trials throughout the respective study periods.

  • SUNRISE 1 utilised gold-standard polysomnograms to quantify sleep time in the laboratory setting over a 1-month period. Lemborexant was able to demonstrate significant improvements in sleep onset and sleep maintenance compared to placebo and zolpidem tartrate extended release (ER).
  • SUNRISE 2 assessed subjective efficacy outcomes via patient-reported sleep diaries, subsequently providing long-term evidence for lemborexant’s sustained subjective efficacy over a 12-month period in the home environment.
  • Treatment related adverse events were generally mild across both studies with somnolence being the most prominent adverse effect. Encouragingly, the drug was associated with reduced postural instability compared to Zolpidem suggesting comparatively minor CNS impairment. 

Clinical Applications

There is encouraging support for lemborexant’s utility as a potential long-term treatment option for insomnia disorder, conferring improvements in sleep onset and sleep maintenance. The drug also appears to be well tolerated and circumvents adverse effects associated with traditional hypnotics like benzodiazepines. 

Its benefit however, must be contextualised to the patient populations included in the SUNRISE development program. Notably, the SUNRISE trials recruited generally older adults of predominantly White ethnicity.

In addition, while the Phase III trials allowed for psychiatric diagnoses, they excluded people with higher scores on anxiety and depression scales. Individuals with evidence of clinically significant disease such as renal impairment, cardiac disease or respiratory disorders etc., that were deemed by the investigator to be unsafe for drug use were also excluded from the trials.

With knowledge that the prevalence of insomnia is considerably higher in patients with chronic medical disorders and co-morbid psychiatric disorders (approximately 40% of all insomnia cases), caution must be exercised with extrapolating lemborexant’s utility as a sleep aid for people with co-morbid psychiatric or severe chronic disorders.

 A summary of the SUNRISE clinical trial program is detailed below. 

Study (Population) Inclusion/ Exclusion Criteria  Study Design Outcomes
SUNRISE 1

R Rosenberg et al. Dec 2019

Randomised, double-blind, parallel-group, placebo-controlled

Conducted at 67 sites in North America and Europe between 2016 – 2018

N=1,006 participants

869 (86.4%) female with a median age of 63y, predominantly white (72.3%) with only 0.2% Chinese and 1.0% of other Asian descent representation.

Baseline demographics across all 4 treatment arms were balanced and insomnia severity was considered moderate based on the baseline Insomnia Severity Index (ISI) score (mean 19.1 S.D. 3.5)

Inclusion 

Women >55yo and Men >65yo with insomnia as defined by DSM-5 and an ISI score of 13 or greater.

Exclusion

Current diagnosis of sleep-related breathing disorder e.g. OSA, restless leg syndrome, narcolepsy. Patients with high depression (Beck Depression Inventory – II >19) or anxiety (Beck Anxiety Index >15) scores at screening were also excluded.

Please refer to the study protocol for the full list.

Patients were randomised in a 5:5:5:4 ratio to receive placebo (n=208), zolpidem tartrate ER 6.25mg (n=263) or lemborexant 5mg (n=266) / 10mg (n=269) for 1 month at bedtime

Paired polysomnograms were collected at baseline, the first 2 nights and the last 2 nights of treatment

To Note:

At the end of 1 month ISI scores significantly improved in all active arms compared to placebo. Comparisons with Zolpidem therapy were also not significantly different for either dose of lemborexant. There was no evidence of rebound insomnia in the 2 weeks after the study period with either lemborexant or zolpidem therapy. 

Efficacy

Primary endpoint – change from baseline in log-transformed latency to persistent sleep (LPS): Both doses of lemborexant demonstrated statistically significant changes from baseline compared with placebo. Treatment ratio at 1 month:

  • Lemborexant 5mg, 0.77; 95% CI 0.67-0.89; P < 0.001
  • Lemborexant 10mg, 0.72; 95% CI 0.63-0.83; P < 0.001

Secondary endpoints

  • Both doses of lemborexant demonstrated statistically significant treatment difference from baseline compared with placebo and Zolpidem. The increase in sleep efficiency in both lemborexant groups translated into > 60 mins more sleep/ night than before treatment.
  • Change from baseline in wake-after-sleep onset (WASO): Both doses of lemborexant demonstrated statistically significant treatment difference from baseline compared with placebo and zolpidem. Both doses of lemborexant reduced WASO by more than 45 mins relative to baseline. 
  • WASO decreases were sustained throughout the night whereas participants in the Zolpidem group experienced placebo-like effects in the final quarter of the night.

Safety

AEs were mostly mild or moderate in severity. 

6 participants (4 in zolpidem group and 2 in the lemborexant 5mg group) reported serious AEs and none were treatment-related. Sleep paralysis was reported by 1 participant receiving lemborexant 5mg and 3 participants receiving lemborexant 10mg. 

SUNRISE 2

J Yardley et al. Jun 2020

Randomised, double-blind, parallel group with a 6-month placebo-controlled period followed by a 6-month active-treatment only period.

Conducted at 119 sites globally, including America, Europe, Asia and Oceania between Nov 2016 – Jan 2019.

N=949, mean age 54.5yo (72.4% were aged less than 65), 68.2% female, predominantly white (71.5%) and 17% Japanese. Mean ISI score was 19.2 (S.D. 3.2)

Inclusion

Adults >/= 18y of age with insomnia disorder meeting the DSM-5 criteria and an ISI score of at least 15. 

Exclusion

Co-morbid sleep disorders e.g. sleep apnea, restless legs syndrome or narcolepsy. Individuals with a diagnosis of major medical or psychiatric disorder that was not adequately treated (investigator opinion), BDI-II > 19, BAI > 15, excessive caffeine consumption and drug or alcohol dependency

Please refer to the study protocol for the full list.

Patients were randomised in a 1:1:1 manner to receive placebo (n=318), 5mg lemborexant (n=316) or 10mg lemborexant (n=315). For the first 6-months. In the second 6-months, participants in the placebo group were randomised 1:1 to 5mg lemborexant or 10mg lemborexant. Participants on active drug in the first 6-months continued on their originally assigned doses.

Within 1h of waking, participants were instructed to complete the electronic sleep diary. Sleep onset and maintenance endpoints were analysed using data from these sleep diaries. 

Efficacy 

Primary endpoint – Subjective sleep onset latency (sSOL) i.e. estimated time (mins) from attempt to sleep until sleep onset: Both doses of lemborexant (5mg, -21.8min; 10mg, -28.2min vs placebo, 11.4min) demonstrated statistically significant decreases from baseline compared with placebo (p<0.0001 for both comparisons). Significant reductions were observed from the 1st week through to the 6 and 12 month mark. 

Secondary endpoints

  • Subjective sleep efficiency (sSE) expressed as the proportion of subjective total sleep time per subjective time in bed: Significantly greater with both doses of lemborexant compared to placebo at month 6 and month 12.
  • Subjective WASO i.e. estimated sum of time (mins) of wake during the night after initial sleep onset until day: Significant reductions with both doses of lemborexant at month 6 and month 12.

Safety 

24.8% and 29% of participants receiving lemborexant 5mg and 10mg respectively experienced at least 1 treatment emergent adverse event (TEAE) with 4.1% and 8.3% discontinuing the drug as a result. The most common TEAE leading to discontinuation was somnolence. 

The most common TEAE was headache and influenza (>5%). 

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