Not true; their clinical trials[1] finds Improvements in GI symptoms, ASD symptoms, and the microbiome all persisted for at least 8 weeks after treatment ended, suggesting a long-term impact[2]

More recently, a study finds The modulation of the gut microbiota using MTT in ASD has shown beneficial and long-term effects on GI symptoms and core symptoms of autism[3]

[1] https://gutbrainaxistherapeutics.com/pipeline/#clinical-tria...

[2] https://link.springer.com/article/10.1186/s40168-016-0225-7

[3] https://www.tandfonline.com/doi/abs/10.1080/19490976.2025.24...