Study objectives

To evaluate long-term safety and maintenance of efficacy of solriamfetol treatment for excessive daytime sleepiness in narcolepsy and obstructive sleep apnea (OSA).

Methods

Participants with narcolepsy or OSA who completed a prior solriamfetol study were eligible. A 2-week titration period was followed by a maintenance phase (up to 50 weeks). Efficacy was assessed by Epworth Sleepiness Scale (ESS) and Patient and Clinical Global Impression of Change (PGI-C and CGI-C, respectively). After approximately 6 months of treatment, a subgroup entered a 2-week placebo-controlled randomized withdrawal (RW) phase. Change in ESS from beginning to end of the RW phase was the primary endpoint; PGI-C and CGI-C were secondary endpoints. Safety was assessed throughout the study.

Results

In the maintenance phase, solriamfetol-treated participants demonstrated clinically meaningful improvements on ESS, PGI-C, and CGI-C. In the RW phase, least squares mean change on ESS was 1.6 in participants continuing solriamfetol versus 5.3 in participants switched to placebo (p < .0001). For both secondary endpoints, higher percentages of participants receiving placebo were reported as worse at the end of the RW phase versus solriamfetol (p < .0001). Common treatment-emergent adverse events (TEAEs) with solriamfetol were headache, nausea, nasopharyngitis, insomnia, dry mouth, anxiety, decreased appetite, and upper respiratory tract infection; 27 (4.2%) participants experienced at least one serious TEAE, and 61 (9.5%) withdrew because of TEAEs.

Conclusions

This study demonstrated long-term maintenance of efficacy of solriamfetol under open-label and double-blind, placebo-controlled conditions. Safety profile of solriamfetol was consistent with previous 12-week studies; no new safety concerns were identified.

Trial registration

NCT02348632.