Placebo-Controlled, Double-Blind, Study to Determine the Safety and Efficacy of SDX in Patients With IH

SDX is a prodrug of dexmethylphenidate (d-MPH). SDX behaves as a prototypical prodrug that is devoid of pharmacological effects until metabolized to active d-MPH. Central nervous system (CNS) stimulants, including d-MPH products, are being used off-label by patients with IH. The potential advantage of SDX-derived d-MPH is its unique PK profile with rising d-MPH plasma concentrations at approximately 3 hours postdose followed by a broad peak from approximately 8 to 12 hours postdose (without sharp exposure spikes), and a gradual decline after the peak.

The optimal dose of SDX will be determined for each participant by titration based on individual tolerability and response during the 5-week SDX-only Open-Label Titration period (OLTP), after which 2/3 of the participants will continue to receive SDX and 1/3 of the participants will receive placebo (withdrawal design) in the 2-week Double-Blind Withdrawal Period (DBWP).

The study will evaluate safety (primary endpoint), efficacy and PK in patients with IH after daily oral administration of SDX either once per day in the evening (qd pm) or twice per day (morning and evening: bid). The study is expected to inform about the optimal SDX dose range and the best dose regimen (nighttime dosing or twice-per-day) for further studies in patients with IH and narcolepsy. The evening dosing regimen (just before bedtime) is of interest since there is little or no exposure to d-MPH for the first several hours post-dose and the mean peak d-MPH concentration occurs at 10-12 hours post-dose (ie, in the morning after a nighttime dose).