The purpose of the study is to evaluate the safety and tolerability of multiple dose administration of JNJ-39393406 in young healthy participants, and subsequently in healthy elderly participants.

This is a double-blind (neither physician nor participant knows the treatment that the participant receives), placebo-controlled (study in which an inactive substance is given to one group of participants, while the study medication is given to another group), randomized (the study medication is assigned by chance), and multiple ascending dose (participants will receive multiple doses of study medication and the dose level is subsequently escalated in further groups) study. This study will consist of screening phase (between 21 and 2 days prior to dose administration), a double-blind treatment phase (Part A - 7 days and Part B - 13 days), and a follow-up phase (within 7 to 14 days after last dose administration). In Part A of the multiple ascending dose study approximately 40 young healthy male participants will be randomly allocated to 5 cohorts (group of individuals with similar characteristics) to receive single daily doses of either JNJ-39393406 or placebo for 7 consecutive days. After each dose level, safety, tolerability, and pharmacokinetic (PK) profile (explores what the body does to a medication) of the dose level will be evaluated and the next dose level will be escalated considering the safety and tolerability data. In Part B of the study approximately 48 elderly healthy male and female participants will be randomly allocated to A, B, and C cohorts to receive single daily doses of either JNJ-39393406 or placebo for 13 consecutive days. Dose levels in Part B will be selected based on the PK data from Part A. In both Part A and Part B of the study the dose levels will be increased only after acceptable safety and tolerability data will be obtained. Safety evaluations will include assessments of adverse events, clinical laboratory tests, 24-hour creatinine clearance, Holter monitoring, telemetry, electrocardiogram, vital signs, physical examination, and neurological examination. The study duration for each participant will be approximately 8 weeks.

Inclusion Criteria:

• Willing to adhere to the prohibitions and restrictions specified in the protocol
• Part A: Body mass index (BMI) between 18 and 30 kg/m2, inclusive (BMI = weight/height2)
• Part B: Female participants must be postmenopausal (for at least 12 months)
• BMI between 18 and 33 kg/m2, inclusive

Exclusion Criteria:

• Clinically significant abnormal values for clinical chemistry, hematology or urinalysis at screening or admission. It is expected that laboratory values will generally be within the normal range for the laboratory, though minor deviations, which are not considered to be of clinical significance to the investigator, are acceptable
• Clinically significant abnormal physical examination, vital signs or 12 lead electrocardiogram (ECG) at screening. Minor deviations in ECG, which are not considered to be of clinical significance to the investigator, are acceptable
• Clinically significant abnormal 24 hour Holter monitoring at screening in the opinion of the investigator
• Significant history of or current psychiatric or neurological illness
• Serology positive for hepatitis B surface antigen, hepatitis C antibodies or human immunodeficiency virus antibodies at screening