 The purpose of this study is to determine the effectiveness of folinic acid in the treatment of language problems in children with autism spectrum disorder. Folinic acid, also known as leucovorin, is approved by the U.S. Food and Drug Administration FDA to decrease side effects during cancer chemotherapy. Folinic acid may be helpful in treating language problems in children with autism spectrum disorder, but this is not known. Therefore, folinic acid is an investigational new drug for this study.Investigators will enroll up to 60 participants in this study at the Marcus Autism Center over 5 years and a total of 160 participants across all three centers. Participation will last between 12 - 24 weeks 