This Phase II clinical trial is a monocenter, double-blind, randomized, placebo-controlled study aimed at evaluate the efficacy and safety of solriamfetol from 75 to 300 mg per day in IH patients.

Patients will be randomized (1:1) to receive either solriamfetol or placebo, with titration, every morning upon awakening during all treatment periods (Day 0 to Week 7).

Main inclusion criteria:

• Age between 18 and 60 years-old
• BMI between 18 and 30 kg/m2
• Diagnostic of idiopathic hypersomnia (ICSD-3 criteria) made in the last 5 years, based on Polysomnography (PSG) and Multiple Sleep Latency Test (MSLT) results, showing either: a mean sleep latency (MSL) of ≤8 minutes and < 2 SOREMPs and/or a 24-h long term polysomnography recording showing total sleep time >11h/24 hours.
• Apnea-hypopnea index (AHI) <15/hour, Apnea index <10/hour, micro-arousals index <15/hour, Periodic limb movement (PLM) index associated with micro-arousals <15/hour on the PSG and MSLT performed within the past 5 years.
• Absence of sleep deprivation, assessed by actigraphy or sleep logs for the 7 days preceding study inclusion
• ESS score ≥11 points
• Written informed consent
• National health insurance coverage
• Understand, read and speaks French well
• The participant agrees to follow the contraceptive requirements detailed in the protocol.

Main non-inclusion criteria

• Non-stabilized hypertension

• To be at imminent risk of suicide or injury to self, others, or property, or the participant has attempted suicide within the past year before screening, or has positive answers on items number 4 or 5 on the Colombia-Suicide Severity Rating Scale (based on the 6 months before randomization).

• Other psychiatric conditions in the past 6 months

• Presence of other central nervous system diseases: neurodegenerative diseases, seizure disorders, or history of head trauma associated with loss of consciousness

• Prior history of psychotic episodes

• Psychostimulant treatment with modafinil, methylphenidate, mazindol, pitolisant, ongoing or within 15 days prior to visit 1

• Treatment for obstructive sleep apnea-hypopnea syndrome ongoing or within 15 days prior to visit 1

• Treatment with psychotropic drugs: neuroleptics (i.e. clozapine, olanzapine, aripiprazole, …), sedative hypnotics (benzodiazepines, zolpidem, zopiclone), central nervous system depressants (barbiturates, …), antidepressants (SSRI (e.g. fluoxetine, sertraline, paroxetine…), serotonin and norepinephrine reuptake inhibitors (SRNI : e.g. venlafaxine, duloxetine), Monoamine oxidase inhibitors), anxiolytic drugs, anticonvulsive therapy (i.e. topiramate, inhibitors of GHB dehydrogenase (i.e. valproate, ethosuximide, phenytoin), or drugs for pain (level 2 (e.g. codeine, tramadol), and level 3 (morphine and derivatives)), ongoing or within 30 days prior to visit 1.

• Treatment with dopamine antagonist antiemetics except domperidone, Catechol-O-methyltransferase (COMT) inhibitors, or sedative antihistamines ongoing or within 30 days prior to visit 1

  => Of note, for all the above treatments: if patient has received such therapy, a washout-period of at least 15 days, or equivalent to 5 half-lives of the drug, prior to the inclusion in the study is required before starting treatment in this study. Of note, for antidepressants, a washout of at least 30 days should be required.

• Previously treated with solriamfetol

• History of chronic alcohol or drug abuse within the prior 12 months

• Malignant neoplastic disease requiring therapy within 12 months prior to Visit 1 or clinically relevant

• Heart failure, unstable hypertension or other cardiovascular disease compromising the patient's wellbeing or ability to participate in this study

• Renal or hepatic impairment

• No regular sleep at night: shift work or other continuous non-disease-related life conditions

• Has received any other investigational drug within 30 days or 5 half-lives (whichever is longer) prior to screening or plans to use an investigational drug (other than the study intervention) during the study