Have normal results from the physical examination, laboratory tests, ECG, and vital signs at Visit 1 of this study (last visit of Study MEM-MD-91).Every effort should be made to maintain the same caregiver as used in the lead-in study throughout this study Have a knowledgeable caregiver who is capable of providing reliable information about the patient's condition, attending all clinic visits with the patient, and overseeing the administration of study drug.A separate written informed consent for the caregiver must also be obtained before the conduct of any study specific procedures The parent/guardian/LAR must provide written informed consent before the patient's participation in the study. Provide written informed assent, when developmentally appropriate, to participate in the study before conduct of any study-specific procedures.Met responder criterion at two consecutive visits separated by at least two weeks in lead-in study MEM-MD-91.Completed at least 12 weeks of exposure to study drug in lead-in study MEM-MD-91 (NCT01592786).The weight-based dose limits in this study were as follows: h/mL which represents a 10-fold lower exposure than observed at the NOAEL(No observed adverse effect level) of 15 mg/kg/day in juvenile rats.Weight based dose limits were selected in this study to ensure that exposure in terms of area under the curve (AUC) was less than the predefined limit of 2100 ng The responder criterion was defined as having at least a 10 point improvement (reduction in score) in the Social Responsiveness Scale (SRS) total raw score relative to the Visit 1 total raw score in Study MEM-MD-91. Patients who completed at least 12 weeks of study drug exposure and met protocol specified responder criterion in lead in Study MEM-MD-91 (NCT01592786) at two consecutive visits separated by at least two weeks were eligible to transition to this study. This clinical study was a 12-week, multicenter, double-blind, placebo-controlled, randomized withdrawal study in pediatric outpatients with autism, Asperger's Disorder, or Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS). Why Should I Register and Submit Results?.