The study treatment failed to demonstrate efficacy in target population in two other clinical studies (CAFQ056B2214 and CAFQ056A2212).

The purpose of this study is to generate long-term safety, tolerability and efficacy data for AFQ056 in eligible adolescent patients with FXS who have participated in the CAFQ056B2214 study, the PK study CAFQ056B2131, or another study of AFQ056 which included FXS patients below 18 years of age provided the patient is at least 12 years of age at the time of entry into the current study.

Inclusion Criteria:

• Group 1 patients:
• Must have completed study CAFQ056B2214 or another study of AFQ056 which included FXS patients below 18 years of age within one week of enrollment into the open-label study.
• Has a caregiver or caregivers who spend, on average, at least 6 hours per day with the patient , who is willing to and capable of supervising treatment, providing input into efficacy and safety assessments, and accompanying the patient to study visits.
• Group 2 patients:
• Must meet one of the following conditions:
• Completed Study CAFQ056B2131
• Completed Study CAFQ056B2214 or another study of AFQ056 which included FXS patients below 18 years of age but enrollment into the current study was delayed for more than a week.
• Discontinued prematurely from Study CAFQ056B2214 or another study of AFQ056 which included FXS patients below 18 years of age due to intolerability of the dosage in the patient's assigned treatment group.
• Has a caregiver or caregivers who spend, on average, at least 6 hours per day with the patient , who is willing to and capable of supervising treatment, providing input into efficacy and safety assessments, and accompanying the patient to study visits.

Exclusion Criteria:

• Discontinuation from Study CAFQ056B2214 or CAFQ056B2131 or another study of AFQ056 which included FXS patients below 18 years of age due to safety reasons
• Female patients who are sexually active at any time during the study
• Any advanced, severe or unstable disease
• History and/or presence of schizophrenia, bipolar disease, psychosis, confusional states and/or repeated hallucinations as per DSM-IV criteria
• History of suicidal behavior or considered a high suicidal risk
• History of severe self-injurious behavior
• History of uncontrolled seizure disorder or resistant to therapy within the past 2 years (Patients who are clinically stable under anti-convulsant therapy for the past 2 years are not excluded)
• History of clinically significant allergies requiring hospitalization or non-inhaled corticosteroid therapy (asthma, anaphylaxis, etc.)
• History of malignancy of any organ system (other than localized basal cell carcinoma of the skin), treated or untreated, within the past 5 years, regardless of whether or not there is evidence of local recurrence or metastases
• Patients who are using (or used within 6 weeks before baseline) digoxin or warfarin
• Using (or used within 6 weeks before baseline) concomitant medications that are potent inhibitors or inducers of CYP3A4
• Using glutamatergic agents (riluzole, memantine, etc.) or lithium within 6 weeks of baseline

Other protocol-defined inclusion/exclusion criteria may apply.

The terms and conditions of Novartis' agreements with its investigators may vary. However, Novartis does not prohibit any investigator from publishing. Any publications from a single- site are postponed until the publication of the pooled data (i.e, data from all sites) in the clinical trial.