Alkermes Launches Phase 3 Brilliance Program for Alixorexton in Narcolepsy

In recent news, Alkermes has initiated the phase 3 Brilliance clinical program evaluating alixorexton, an investigational oral orexin 2 receptor (OX2R) agonist, for the treatment of narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2).¹ The program includes three randomized, double-blind, placebo-controlled trials—Brilliance NT1 (Studies 302 [NCT07455383] and 304) and Brilliance NT2 (Study 303; NCT07502443)—each designed to assess efficacy, safety, and dosing strategies over a 12-week treatment period.

Phase 3 Program Design and Endpoints

The Brilliance studies will evaluate both once-daily and split-dose regimens of alixorexton across global populations. In NT1, each study is expected to enroll approximately 150 patients, while the NT2 trial will include approximately 180 participants.

“The initiation of the phase 3 Brilliance Studies program marks an exciting and important milestone for alixorexton. Building on the positive findings observed in our large phase 2 program across both narcolepsy type 1 and type 2, we are entering this pivotal stage with confidence,” Craig Hopkinson, MD, MBChB, Chief Medical Officer and Executive Vice President of Research & Development at Alkermes, said in a statement.¹ “We look forward to evaluating alixorexton in both once-daily and split-dose regimens as we seek to optimize efficacy, safety and dosing flexibility in the development of a potential new treatment option for patients and providers.”

Across all studies, the primary endpoint is change from baseline to week 12 in mean sleep latency on the Maintenance of Wakefulness Test (MWT), a standard objective measure of wakefulness. Secondary endpoints include changes in Epworth Sleepiness Scale (ESS) scores, patient-reported outcomes assessing fatigue and cognition, and overall disease severity.^2,3

For NT1 specifically, additional endpoints include weekly cataplexy rate, reflecting a key clinical feature of the disorder. Safety will be assessed through treatment-emergent adverse events over approximately 14 weeks.²

Building on Prior Phase 1 and Phase 2 Data

The initiation of the Brilliance program follows earlier clinical findings that supported advancement into phase 3, including data that led to the FDA granting Breakthrough Therapy designation for alixorexton in NT1.

In the phase 2 VIBRANCE-1 study, a randomized, double-blind, placebo-controlled trial of 92 patients with NT1, alixorexton demonstrated statistically significant, dose-dependent improvements in wakefulness as measured by the MWT after 6 weeks of treatment across all tested doses (4 mg, 6 mg, and 8 mg). These improvements were accompanied by significant reductions in excessive daytime sleepiness, with Epworth Sleepiness Scale scores improving at all doses (P <.0001).⁴

Additional findings showed improvements in weekly cataplexy rates, with the 6-mg dose reaching statistical significance (P = .005), as well as clinically meaningful gains in patient-reported outcomes, including the Narcolepsy Severity Scale and British Columbia Cognitive Complaints Inventory (P <.001 and P <.0001, respectively). Improvements in fatigue were also observed across all dose groups (P <.01).

Earlier phase 1 data further supported the drug’s wake-promoting effects, demonstrating dose-dependent increases in mean sleep latency of 18, 30, and 37 minutes in 1-, 3-, and 8-mg dose groups, respectively, compared with a reduction in the placebo group. These findings established proof of concept for orexin receptor activation as a mechanism to improve wakefulness.⁵

Across studies, alixorexton was generally well tolerated, with no serious treatment-emergent adverse events reported and no clinically meaningful changes in laboratory or cardiovascular parameters.

Mechanism and Clinical Rationale

Alixorexton is a selective OX2R agonist designed to target the orexin system, a key regulator of wakefulness produced in the lateral hypothalamus.¹

Loss of orexin signaling is a defining feature of NT1 and contributes to excessive daytime sleepiness and cataplexy, while broader dysregulation of wake-promoting pathways is implicated in NT2. By directly activating OX2R pathways, alixorexton aims to restore physiologic wakefulness signaling rather than relying on traditional stimulant-based approaches.

This mechanism has emerged as a promising strategy in sleep medicine, particularly as clinicians seek therapies that address underlying pathophysiology across hypersomnolence disorders.

Long-Term Development and Clinical Outlook

Participants who complete the Brilliance studies will be eligible to enroll in a long-term, open-label extension study to further evaluate durability and safety. The phase 3 program represents a key step in determining whether the improvements observed in earlier studies translate into consistent, clinically meaningful outcomes across broader populations and longer durations.

REFERENCES
1. Alkermes Announces Initiation of Phase 3 Brilliance Studies Evaluating Alixorexton for the Treatment of Narcolepsy Type 1 and Type 2. News release. Alkermes. April 1, 2026. Accessed April 6, 2026.
2. A Study to Evaluate the Efficacy and Safety of ALKS 2680 in Adults With Narcolepsy Type 1 (Brilliance NT1). Clinicaltrials.gov. https://clinicaltrials.gov/study/NCT07455383. Accessed April 6, 2026.
3. A Study to Evaluate the Efficacy and Safety of ALKS 2680 in Adults With Narcolepsy Type 2 (Brilliance NT2). Clinicaltrials.gov. https://clinicaltrials.gov/study/NCT07502443
4. Alkermes Announces Positive Topline Results From Vibrance-1 Phase 2 Study of Once-Daily Alixorexton in Patients With Narcolepsy Type 1. News release. Alkermes. July 21, 2025. Accessed April 6, 2026. https://www.prnewswire.com/news-releases/alkermes-announces-positive-topline-results-from-vibrance-1-phase-2-study-of-once-daily-alixorexton-in-patients-with-narcolepsy-type-1-302509211.html
5. Alkermes Presents First Clinical Data for Orexin 2 Receptor Agonist ALKS 2680 at World Sleep Congress. News release. Alkermes. October 23, 2023. Accessed April 6, 2026. https://www.prnewswire.com/news-releases/alkermes-presents-first-clinical-data-for-orexin-2-receptor-agonist-alks-2680-at-world-sleep-congress-301963945.html