This presentation will cover the results of a major Phase 2 clinical trial of Microbiota Transplant Therapy (MTT) for adults on the autism spectrum. This was a randomized, double-blind, placebo-controlled study for Part 1, and then in Part 2 the placebo group received a similar treatment, and the original treatment group received an extra 8 weeks of microbiota transplant. We found that MTT was generally safe and well-tolerated, and microbiota capsules were better tolerated than placebo capsules. For the primary outcome (autism symptoms), the treatment group improved more than the placebo group (medium effect). For the secondary outcome of daily stool record, the treatment group improved more than the placebo group (medium effect). The microbiome of the treatment group became more similar to the donor, with increases in certain beneficial bacteria. Overall, we believe these positive results demonstrate that MTT is generally safe and effective for treating autism and GI symptoms in adults with autism, and provide important insight into how to improve dosing to potentially improve clinical benefit.