An orexin agonist restores wakefulness in narcolepsy type 1

Design

two phase 3, randomised, placebo-controlled trials over 12 weeks

Population

273 participants aged 16–70 with narcolepsy type 1 (168 in First Light, 105 in Radiant Light)

Primary outcome

change from baseline to week 12 in mean sleep latency on the Maintenance of Wakefulness Test

Effect

+14.3 to +19.8 minutes with oveporexton vs −0.4 to −0.8 with placebo (adjusted P<0.001); weekly cataplexy down 79.0–88.8% vs 27.7–39.1%

Narcolepsy type 1 is caused by loss of orexin-producing neurons, and until now treatment has been symptomatic — stimulants for sleepiness, separate agents for cataplexy. Oveporexton is an oral orexin receptor 2 agonist, and two phase 3 placebo-controlled trials tested it over 12 weeks in participants aged 16 to 70. First Light randomised 168 people to 1 mg, 2 mg or placebo twice daily; Radiant Light randomised 105 to 2 mg or placebo.

Mean sleep latency on the Maintenance of Wakefulness Test, which runs from 0 to 40 minutes with 20 or more considered normal, improved from baseline by 14.3 to 19.8 minutes across the oveporexton arms against −0.4 to −0.8 minutes on placebo (adjusted P < 0.001 for every comparison). Epworth Sleepiness Scale scores fell by 9.7 to 11.8 points against 1.5 to 1.7 with placebo. Weekly cataplexy rate fell by a median 79.0 to 88.8% against 27.7 to 39.1%.

The tolerability figures deserve equal billing. Adverse events occurred in 86 to 89% of treated participants against 43 to 54% on placebo, and the commonest — increased urinary frequency and transient insomnia — affected a majority of those taking the drug. Effects of this size on a disabling condition are unusual; so is a side-effect rate that high. Both belong in the counselling.

• Recognise narcolepsy type 1 as a condition where the underlying deficit is now druggable
• Expect urinary frequency and early insomnia to be the common complaints, not rare ones
• Do not extrapolate to narcolepsy type 2 or idiopathic hypersomnia — these trials enrolled type 1
• Twelve weeks is short for a lifelong condition; durability and long-term safety are not yet known

Why it matters

For the first time the missing signal in narcolepsy type 1 can be replaced rather than worked around.

Don't overread it

These are 12-week trials; nothing here establishes durability or long-term safety.

The statistics, in plain English

A 14 to 20 minute gain on a 40-minute test, from a placebo change of under a minute, is a very large effect by any standard — these are not marginal statistical differences. Epworth changes of around 10 points move a patient from severely sleepy to near-normal. The 12-week duration is the main limit: it establishes that the drug works, not that it keeps working or stays safe.

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