A Molecular and Functional Brain Imaging Study in Individuals With Down Syndrome and Healthy Controls Following Single Dose RG1662

• Brain GABAA receptor alpha5 subunit localization/density assessed by positron emission tomography (PET) [ Time Frame: approximately 1 day ] [ Designated as safety issue: No ]
• Brain GABAA receptor alpha5 subunit occupancy following single dose of RG1662 [ Time Frame: approximately 1 day ] [ Designated as safety issue: No ]
• Correlation of RG1662 plasma concentrations and GABAAalpha5 receptor occupancy [ Time Frame: approximately 12 months ] [ Designated as safety issue: No ]

• Safety: Incidence of adverse events [ Time Frame: approximately 12 months ] [ Designated as safety issue: No ]
• Resting state functional brain connectivity following a single dose of either RG1662 or placebo, assessed by functional magnetic resonance imaging (fMRI) [ Time Frame: approximately 1 day ] [ Designated as safety issue: No ]
• Functional brain connectivity of individuals with Down syndrome versus healthy controls receiving placebo [ Time Frame: approximately 12 months ] [ Designated as safety issue: No ]

This single-center, double-blind, placebo-controlled, parallel-group study with crossover component will evaluate the GABAAalpha5 receptor expression, occupancy and functional connectivity in the brains of individuals with Down syndrome and healthy controls following single dose RG1662. On two separate visits, no less than 96 hours and no more than 6 weeks apart, subjects will receive a single oral dose of either RG1662 or placebo followed by positron emission tomography (PET) and magnetic resonance imaging (MRI) scans.

• Drug: RG1662
  Single oral dose
• Drug: placebo
  Single oral dose

• Experimental: RG1662
  Intervention: Drug: RG1662
• Placebo Comparator: Placebo
  Intervention: Drug: placebo

Inclusion Criteria:

Healthy controls and individuals with Down syndrome:

• Male and female adults, 18 to 30 years of age
• Body mass index (BMI) 18 - 40 kg/m2 inclusive
• Females of child-bearing potential and males with female partners of child-bearing potential must agree to use two medically approved methods of contraception, one of which must be a barrier method, for the duration of the study and for 4 months after the last study drug administration
• Clinical laboratory values within normal limits or abnormalities considered not significant by the investigator and sponsor; subjects with thyroid disease may be included in the study provided they are euthyroid and stable on treatment for at least one month prior to screening

Individuals with Down syndrome must also meet the following:

• Diagnosis of Down syndrome confirmed by karyotype; subjects may have free trisomy 21 or Robertsonian translocations; mosaic Down syndrome will be excluded
• Subjects must have a parent or other reliable caregiver who agrees to accompany the subject to all clinic visits, provide information about the subject as required by protocol, and be willing to give informed consent

Exclusion Criteria:

• Regular smoker (>5 cigarettes or equivalent: 3 cigars, 6 cigarillos, 3 pipes per day)
• Concomitant disease or condition or any clinically significant finding at screening that could interfere with, or for which the treatment might interfere with the conduct of the study, or that would, in the opinion of the investigator, pose an unacceptable risk to the subject in this study
• Severe head trauma or CNS infections (e.g. meningitis)
• History of epilepsy or seizures other than benign febrile convulsions of childhood
• Any confirmed significant allergic reactions against any drug, anaphylaxis or severe environmental allergies as judged by the investigator
• Positive for hepatitis B, hepatitis C or HIV infection
• Positive urine test at screening or at follow-up for drugs of abuse, or positive alcohol breath test at screening and prior to dosing
• Previous inclusion in research and/or medical protocol involving nuclear medicine, PET or radiological investigations with significant radiation burden (as defined by protocol)
• Pregnant or lactating women