Presenting at the World Sleep Congress 2025, the Dublin-based company’s Phase II study bested Takeda drug in both efficacy and safety.
Alkermes’ mid-stage narcolepsy type 1 drug alixorexton improved wakefulness, cognition and fatigue over six weeks, setting up a potential showdown with Takeda in the sleep disturbance space.
Presenting at the World Sleep Congress 2025, the company announced that patients in the Phase II Vibrance-1 trial got statistically significant and “clinically meaningful” improvements in the three key narcolepsy endpoints over a six-week treatment period.
Patients going into the study had mean sleep latency (MSL)—the time from being completely awake to being asleep—of three minutes. On doses of 4 mg, 6 mg and 8 mg of the drug, patients’ MSL went to 24 minutes, 26 minutes and 28 minutes, respectively. Patients on placebo saw no improvement. Patients also reported that cognitive impairment issues fell away completely, with patients on all doses and at all time points reporting “none or minimal” impairment.
Analysts at Stifel viewed the data with cautious optimism. While they didn’t see the improvements in MSL as “the end all be all” of efficacy for the condition, they added that it did best Takeda’s reported Phase III data for TAK-861 by five minutes, or 25%, the analysts wrote in a note to investors Monday morning.
“The cognition data are especially interesting where at baseline, most patients are reporting mild-to-moderate cognitive impairment that ends up being largely resolved,” the analysts added.
Alkermes also beat Takeda in terms of tolerability. Patients “vote with their feet,” as Stifel analysts put it, with only one patient discontinuation in the Vibrance-1 trial. Takeda, in its TAK-861 data, reported one discontinuation in the placebo group, three in a 60-person low dose group and none in a 66-person higher dose group. Alixorexton’s side effects, most notably rates of insomnia at 33% for the high doses and 32% for the mid-dose, were lower than in TAK-861, which had a 57% insomnia rate.
Seven of 24 high-dose patients experienced blurred vision as well, though noting the single discontinuation the Stifel analysts said that adverse effect “seems generally benign.”
Takeda did not share data on improvements in cognition, stating that the company would share more data in oral and poster presentations as the World Sleep Congress progressed.
Alkermes’ stock is down about 8.75% in Monday morning trading.
According to Alkermes’ announcement, the company plans to move the drug into Phase III trials by the first quarter 2026. Alkermes is also currently enrolling patients for two Phase II trials, called Vibrance-2 and Vibrance-3, to test alixorexton in narcolepsy type 2 and idiopathic hypersomnia, respectively.
Both alixorexton and TAK-861 are selective orexin 2 receptor agonists, which modulate receptors of orexin, a neuropeptide that directly controls wakefulness in the body through activation of multiple neurological pathways.
Correction: (Sept. 9): This story has been updated to clarify that Takeda did provide data on discontinuation rates in its TAK-861 data. BioSpace regrets the error.
