A Study of Suvorexant in Patients With Multiple Sclerosis Fatigue and Insomnia

Inclusion Criteria: * Diagnosis of multiple sclerosis made at least 3 months prior based on McDonald criteria; * Age 18-75 inclusive; * Expanded Disability Status Scale (EDSS) 0- 7.5; * Clinical stability defined as no multiple sclerosis exacerbation or change in disease modifying therapy for 60 days prior to screening; * Screening Fatigue Severity Scale score of ≥4.0; * Has Insomnia Disorder defined by diagnostic criteria published in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5); namely, subject report of all of the following: * One of the following: difficulty initiating sleep; difficulty maintaining sleep; or early morning waking; * Sleep disturbance causes clinically significant distress or impairment in social, occupational, educational, academic, behavioral, or other important areas of functioning; * Sleep difficulty has occurred on 3 or more nights per week; * Sleep difficulty has been present for at least the past 3 months; * Sleep difficulty occurs despite adequate opportunity for sleep; * Insomnia is not explained by another sleep disorder; * Insomnia is not attributable to physiological effects of a consumed substance; * May use other medications that could influence sleep, other than those specifically prohibited, as long as the dose is stable for 4 weeks preceding screening, with no dose changes during the study; * Signed and dated Institutional Review Board-approved informed consent form before any protocol-specific screening procedures have been performed. Exclusion Criteria: * Use of potential multiple sclerosis-associated fatigue drugs within 3 days of screening until study completion, including modafinil, armodafinil, amantadine, methylphenidate, products with amphetamine or dextroamphetamine; * Use of any of any prohibited medication (including Digoxin, benzodiazepines, barbiturates, opiates, Zolpidem, Zaleplon, Eszopiclone, moderate or strong CYP3A inhibitors, or strong inducers of CYP3A) from 3 days prior to screening to termination visit; * Female who is breast-feeding, pregnant, or has the potential to become pregnant during the course of the study (fertile and unwilling/unable to use effective contraceptive measures); * History of narcolepsy; * Has a diagnosis of severe chronic obstructive pulmonary disease (COPD), defined by forced expiratory volume 1 (FEV1) \< 50% of predicted on most recent available pulmonary function test (PFT). Pulmonary function test is not required if the subject has never been diagnosed with chronic obstructive pulmonary disease; * Has a history of severe obstructive sleep apnea (OSA), with severe obstructive sleep apnea defined as having an apnea-hypopnea index (AHI) \> 30 on prior polysomnograph (PSG). Polysomnograph is not required if there is no history of obstructive sleep apnea; * Is concurrently using other central nervous system (CNS) depressants, including alcohol, except that one alcoholic drink per day will be allowed for those with normal hepatic function provided the drink is consumed at least 2 hours prior to or 8 hours after taking the study drug. Medical marijuana is allowed if consumed at the patient's usual dose at least 2 hours prior to or 8 hours after taking the study drug. Recreational marijuana is not allowed from screening until end of study; * Has evidence at screening of severe hepatic impairment as defined by a Child-Pugh score \> 10; * Cognitive impairment that in the opinion of the investigator would prevent completion of study procedures or the ability to provide informed consent; * Suicidality or severe depression as measured by screening Beck Depression Inventory II (BDI) score \> 28 or score of \>1 on Beck Depression Inventory II Question 9 (suicidality screen) at any time during the study; * Any other serious and/or unstable medical condition.