Randomized crossover feasibility trial of helminthic <i>Trichuris suis</i> ova versus placebo for repetitive behaviors in adult autism spectrum disorder

<b>Objectives:</b> Inflammatory mechanisms are implicated in the aetiology of autism spectrum disorder (ASD), and use of the immunomodulator <i>Trichuris suis</i> Ova (TSO) is a novel treatment approach. This pilot study determined the effect sizes for TSO versus placebo on repetitive behaviours, irritability and global functioning in adults with ASD. <b>Methods:</b> A 28-week double-blind, randomised two-period crossover study of TSO versus placebo in ten ASD adults, aged 17–35, was completed, with a 4-week washout between each 12-week period at Montefiore Medical Center, Albert Einstein College of Medicine. Subjects with ASD, history of seasonal, medication or food allergies, Y-BOCS ≥6 and IQ ≥70 received 2,500 TSO ova or matching placebo every 2 weeks of each 12-week period. <b>Results:</b> Large effect sizes for improvement in repetitive behaviours (<i>d</i> = 1.0), restricted interests (<i>d</i> = 0.82), rigidity (<i>d</i> = 0.79) and irritability (<i>d</i> = 0.78) were observed after 12 weeks of treatment. No changes were observed in the social-communication domain. Differences between treatment groups did not reach statistical significance. TSO had only minimal, non-serious side effects. <b>Conclusions:</b> This proof-of-concept study demonstrates the feasibility of TSO for the treatment of ASD, including a favourable safety profile, and moderate to large effect sizes for reducing repetitive behaviours and irritability. <b>Clinicaltrials.gov:</b> NCT01040221