- An untreated follow-up period for 26 weeks. Following informed consent, patients will be screened on the basis of diagnosis of autism, vital signs, clinical laboratories medical history and a physical examination. Eligible patients will be randomized to double-blind treatment with TSO 2500 every other week, TSO 7500 every other week, or placebo every other week, in a ratio of 1:1:1. During the double-blind study phase, study drug will be provided in the clinic in a liquid form and will be administered every other week, starting with the Baseline visit, through Week 14. Week 14 is the last double-blind treatment administration of the study, while Week 16 is the primary time point for assessment of efficacy. Patients will return to the clinic every other week during the double blind treatment period.