Terminated because primary efficacy parameter failed to demonstrate statistically significant difference between memantine and placebo in controlled trials

The objective of this study is to evaluate the long-term safety and tolerability of memantine in the treatment of pediatric patients with autism, Asperger's Disorder or Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS).

This clinical study was a 48-week, multicenter, multinational, open-label extension study in pediatric outpatients with autism, Asperger's Disorder, or PDD-NOS conducted at 106 study centers. Patients were eligible for this long-term extension study if they had:

• completed the open-label Study MEM MD 67,or
• completed the open-label Study MEM-MD-91, or
• completed the double-blind Study MEM-MD-68, or
• discontinued study MEM-MD-68 by meeting requirements for loss of therapeutic response

The weight-based dose limits in this study were as follows:

Group A: ≥ 60 kg; maximum 15 mg/day Group B: 40-59 kg; maximum 9 mg/day Group C: 20-39 kg; maximum 6 mg/day Group D: < 20 kg; maximum 3 mg/day

The decision to close the study early was based on data from 2 double-blind placebo-controlled studies (MEM-MD-57A and MEM-MD-68) that failed to demonstrate a statistically significant difference between memantine and placebo in the primary efficacy parameter based on Social Responsiveness Scale (SRS) total raw score.

Inclusion Criteria:

• Patients who completed Study MEM-MD-67, MEM-MD-68, MEM-MD-91, or discontinued Study MEM-MD-68 due to meeting the criterion for loss of therapeutic response.
• Having normal results from a physical examination and laboratory tests at Visit 1 of this study (last visit of the preceding study). Any abnormal findings must be deemed not clinically significant by the Investigator and documented as such.
• Have a family that is sufficiently organized and stable to guarantee adequate safety monitoring and continuous attendance to clinic visits for the duration of the study

Exclusion Criteria:

• Patients who discontinued a preceding memantine study due to an adverse event possibly related to study drug
• Patients with a concurrent medical condition that might interfere with the conduct of the study, confound interpretation of the study results, or endanger the patient's well being
• Significant risk of suicidality based on the Investigator's judgment, Aberrant Behavior Checklist-irritability subscale (ABC-I), or if appropriate, as indicated by a response of "yes" to questions 4 or 5 in the suicidal ideation section of the Children's Columbia-Suicide Severity Rating Scale (C-SSRS) or any suicidal behavior