Investigational treatments
Researchers are trying to develop new medicines with greater potency, and several medications are under investigation. Early studies have shown that reboxetine, an antidepressant medication that affects dopamine and norepinephrine activity, is an effective treatment for EDS and cataplexy. Ongoing phase 3 studies are examining reboxetine for EDS. Another drug known as FT-218 is a once-nightly formulation of sodium oxybate, unlike the twice-nightly formulations of the drug that currently are available. In a phase 3 trial, the drug was associated with significant improvements in wakefulness and reductions in attacks of cataplexy. Avadel, which is developing the drug, submitted it to the U.S. Food and Drug Administration for approval in 2021, but the agency has not yet made a decision about it.
Researchers and patients alike have high hopes for medications that activate the orexin receptors. Orexin stimulates the wake-promoting neurons in the brain. Narcolepsy, and particularly narcolepsy type 1, is characterized by a loss of hypocretin cells in the central nervous system. The loss of these cells promotes sleepiness and disturbed REM sleep. To counteract this loss of cells, several companies are investigating new orexin agonists.
One such medication is TAK-994, which was developed by Takeda. The drug showed great promise for treating EDS and cataplexy, said Dr. Thorpy. But when phase 3 studies suggested that TAK-994 was associated with hepatotoxicity, the company terminated the studies. Nevertheless, other orexin agonists, including Takeda’s TAK-861, are under investigation.
“If we can restore orexin signaling, it could be like giving insulin to type 1 diabetics,” said Dr. Scammell. This class of medications could provide substantial improvements in sleepiness and other symptoms, he added. “I think when orexin agonists become available, it’s going to be quite transformative.” But these drugs are still in early development and will not be available in clinical practice for several years.
Common psychological comorbidities
Certain comorbidities are prevalent among patients with narcolepsy, and psychiatric disorders tend to be the most common. These comorbidities may complicate the management of narcolepsy. Nevertheless, they often are significant enough to require management in their own right, said Dr. Thorpy.
Depression is likely twice as common among patients with narcolepsy than among the general population, said Dr. Scammell. “Whether this is an actual neurobiologic feature of the disease, or whether it is just a reaction to having a challenging disorder isn’t entirely clear,” he added. “But it doesn’t get the attention or treatment that it deserves.”
Partnering with a psychologist or psychiatrist is important because many treatments can exacerbate mood disorders, said Dr. Maski. In general, stimulants, for example, can worsen depression and anxiety and are associated with increased suicide risk. “We oftentimes are using high-dose stimulants in patients, so mood has to be really carefully monitored and managed,” Dr. Maski added.
Cases of depression and suicidal ideation were reported in clinical trials of sodium oxybate. Although these serious adverse events were rare, patients must be monitored very closely even on treatments specifically approved for narcolepsy, said Dr. Maski. Mood disturbances are reported less frequently with modafinil and pitolisant than with stimulants, she noted.
Many times, patients need to take an antidepressant medication, but these drugs could affect the medicines administered for narcolepsy, said Dr. Thorpy. Pitolisant, in particular, may be adversely affected by current antidepressant medications. The only remedies are to change from pitolisant to another narcolepsy medication or to use an antidepressant that does not have histamine 1 receptor antagonism or affect the QTc interval.
Anxiety also is prevalent among patients with narcolepsy, and it can be worsened by traditional stimulants. These drugs also can increase the likelihood of irritability or obsessive-compulsive tendencies. “Traditional stimulants would be best avoided in these patients who have significant anxiety,” said Dr. Thorpy.