A Study of RG1662 in Individuals With Down Syndrome

Inclusion Criteria:

- Adult individuals, 18 to 30 years of age, with diagnosis of Down Syndrome (confirmed
by karyotype)

- Males and non-pregnant non-lactating females

- Parent or legal guardian/representative and caregiver willing to give written
informed consent

- Subject willing and assenting or consenting to participate

Exclusion Criteria:

- Major depressive disorder not adequately controlled by a selective serotonin reuptake
inhibitor or a serotonin norepinephrine reuptake inhibitor

- Subjects meeting clinical diagnostic criteria for autistic spectrum disorder,
attention deficit or hyperactivity disorder unlikely to cooperate and take part
successfully in the study assessments

- Subjects with other primary psychiatric diagnosis

- Subjects with evidence or meeting clinical diagnosis of dementia

- Subjects with personal history of cardiac abnormalities; patients that have
previously undergone congenital heart surgery can be enrolled provided they have no
residual complication requiring intervention (e.g. pace maker)

- Subjects with clinically significant obstructive pulmonary disease or asthma that is
not adequately treated (oral steroids are not allowed)

- Subjects with thyroid dysfunction that is not adequately controlled and stabilized on
treatment for at least 8 weeks

- Subjects with sustained elevated supine blood pressure (SBP/DBP) at rest exceeding
140/90 mmHg or notable resting tachycardia (mean HR > 60 bpm) or blood pressure below
90/40 mmHg

- Subjects who have taken any other investigational medications within 3 months

- Body mass index (BMI) > 40 kg/m2