A Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Food Effect of RO6953958 in Healthy Participants

Inclusion Criteria:

• Body mass index (BMI) within 18 to 31 kg/m2

• During treatment and for at least 14 days after the last dose to remain abstinent

• Refrain from donating sperm for at least 14 days after last dose

• Part 2 (MAD) only - Participants must be prepared to collect a sleep log and wear anactigraphy device the week before participation in the study. Participants must alsohave scored 5 or less on the Pittsburgh Sleep Quality Index (PSQI), less than 13 onthe Epworth sleepiness scale (ESS), and not be considered an extreme morning orevening type according to the morningness-eveningness questionnaire (MEQ) atscreening to be eligible.

Exclusion Criteria:

• History or evidence of any medical condition potentially altering the absorption,metabolism, or elimination of drugs

• History of any clinically significant gastrointestinal, renal, hepatic,bronchopulmonary, neurological, psychiatric, cardiovascular, endocrinological,hematological, or allergic disease, sleep disorders (Part 2 [MAD] only), unexplainedsyncope (within 12 months prior to screening), metabolic disorder, cancer, orcirrhosis

• Use of any psychoactive medication, or medications known to have effects on centralnervous system (CNS), or blood flow

• History of convulsions

• History of clinically significant hypersensitivity (e.g., drugs, excipients) orallergic reactions

• Abnormal blood pressure (BP) and pulse rate

• Presence of orthostatic hypotension

• History or presence of clinically significant ECG abnormalities or cardiovasculardisease

• Current or chronic history of liver disease or known hepatic or biliaryabnormalities

• Known active or any major episode of infection within 4 weeks prior to the start ofdrug administration

• Participants who test positive for acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

• Have used or intend to use over-the-counter (OTC) or prescription medicationincluding herbal medications within 30 days prior to dosing

• Positive test for drugs, abuse of alcohol, human immunodeficiency virus (HIV),hepatitis B or hepatitis C virus (HCV), presence of hepatitis B surface antigen (HBsAg), or positive hepatitis C antibody test

• Inability or unwillingness to fully consume standardized breakfast at Day 1

• Part 2 (MAD) only - Participants who have issues sleeping or participants who havetravelled across 2 or more time zones in the past month.

• Part 2 (MAD) only - Participants who cannot produce sufficient saliva for studyassessments

• Participants who have donated more than 500 mL of blood or blood products or hadsignificant blood loss within 3 months prior to screening

• Have a history of clinically significant back pain, back pathology, and/or backinjury that may predispose to complications from, or technical difficulty with,lumbar puncture

• Complications that would lead to difficulty in obtaining a lumbar puncture

• Part 3 (DDI) only - History of hypersensitivity to benzodiazepines (includingmidazolam) or its formulation ingredients