Study to Investigate the Safety, Tolerability, and Pharmacokinetics of JNJ-55375515 in Healthy Participants

A Double-Blind, Placebo-Controlled, Randomized, Single and Multiple Ascending Dose Study to Investigate the Safety, Tolerability, and Pharmacokinetics of JNJ-55375515 in Healthy Subjects

The purpose of this study is to assess the safety, tolerability, and pharmacokinetics of JNJ-55375515 in healthy participants after administration of single and multiple oral doses.

This is a randomized (study medication assigned to participants by chance), double-blind (neither the investigator nor the participants know what treatment the participant is receiving), placebo-controlled (an inactive comparator treatment that has no study drug in it), single center study in healthy male participants and female participants of non-childbearing potential (surgically sterile or post menopausal), aged 18 to 58 years inclusive. This study will consist of two parts; a Single Ascending Dose (SAD) part and a Multiple Ascending Dose (MAD) part. The SAD will consist of 6 escalating dose cohorts. Participants in each cohort will be randomized to receive a single oral administration of JNJ-55375515 or placebo after an overnight fast. The planned doses of JNJ-55375515 range from 0.75 to 100 milligrams (mg). Participants in an additional cohort will be dosed in the fed state to determine the effects of food on the safety, tolerability and pharmacokinetics of JNJ-55375515. An additional optional cohort may be evaluated to further explore the safety, tolerability, pharmacokinetics, and pharmacodynamics of JNJ-55375515, with the maximal dose not exceeding 200 mg. The study duration for participants in the SAD part of the study will be approximately 2 to 5.5 weeks, including eligibility Screening. The MAD will consist of 3 cohorts of 9 participants. Participants will receive once daily oral doses of JNJ-55375515 or placebo for 10 consecutive days. The study duration for participants in the MAD part of this study will be approximately 3 to 7 weeks including the eligibility Screening. The Safety of Participants will be monitored throughout the study.

Inclusion Criteria:

• Participant must be healthy on the basis of physical and neurological examination, medical history, vital signs, and electrocardiogram (ECG), and have a body mass index of 18-30 kilogram / square meter (kg/m^2) and a body mass of not less than 50 kg.
• Participant must be healthy on the basis of clinical laboratory tests performed at Screening and Day -1.
• Female participants must not be of childbearing potential by either being post-menopausal or permanently sterilized.
• Female participants must not be pregnant.
• Participant must be willing and able to adhere to the prohibitions and restrictions specified in this protocol, including contraception.
• Each participant must sign an informed consent form (ICF) indicating that he or she understands the purpose of, and procedures required for, the study and are willing to participate in the study.

Exclusion Criteria:

• Participant has current, or history of, clinically significant medical or psychiatric illness.
• Participant has any condition for which participation would not be in the best interest of the participant or that could prevent, limit, or confound any protocol specified assessments or the interpretation of the study results.
• Participant has a personal history of, or a first degree relative with a history of, acute angle-closure glaucoma, or participant has significant hyperopia (far-sightedness).
• Participant has a QT corrected according to Fridericia's formula (QTcF) interval greater than (>) 450 msec (male) or >470 msec (female), or has a history of additional risk factors for torsades de pointes.
• Participant has history of vasovagal episodes.
• Participant has history of drug, alcohol, nicotine, or caffeine abuse.
• Participant who is breastfeeding.
• Participant has had major surgery within 12 weeks of Screening, has donated more than 450 milliliters (mL) of blood, or has acute loss of equivalent amount of blood within 90 days of study drug administration.
• Participant has positive fecal occult blood test results at Screening.
• Participant has history of clinically significant drug and/or food allergies.
• Participant has received another investigational drug within 1 month or a period of less than 10 times the drug's half-life, whichever is longer, before the planned first dose of study drug
• Participant is an employee, or family member of an employee, of the study site.