Microbiota Transfer Therapy (MTT) Trial – An Update for Parents

By Gita Gupta

Imagine moving from a diagnosis of “severe” autism to no longer meeting the criteria for autism spectrum disorder (ASD).  The recently completed Microbiota Transplant Therapy (MTT) Phase 1 study indicates such results are possible and sustainable.

At the beginning of the study, the majority – 83% of participants – were classified as “severe” on an autism diagnosis scale. At a 2 year follow up, only 17% were still “severe”, and 44% no longer met the criteria for an autism diagnosis. Most participants had significant improvements in core autism symptoms and gastrointestinal problems.

MTT holds great promise as a potential treatment for ASD. In an interview with primary researcher Dr. James Adams from Arizona State University, this blog takes an in-depth look at Microbiota Transfer Therapy (MTT.)

Background Info

First of all, what is Microbiota Transfer Therapy (MTT)?

While we usually associate microbes with disease, there are actually trillions of bacteria, viruses, fungi, and other microbes that live in the body. This is called the human microbiota and the part that lives in your gut is called the gut microbiota.

Microbiota transfer therapy (MTT) refers to the technique of transferring the gut microbiota from a very carefully screened, healthy donor to a recipient who has gastrointestinal issues.

Why did you decide to trial MTT in autism?

There is no FDA-approved medication for the core symptoms of autism spectrum disorders (ASD.) Many studies have shown that children and adults with autism also have a high rate of gastrointestinal (GI) symptoms. We came up with the idea of doing a small open-label clinical trial to evaluate the impact of MTT on GI and ASD symptoms of 18 ASD-diagnosed children (1).  An open-label study is a type of study in which both the health providers and the trial participants are aware of the drug or treatment being given.

We came up with this idea based on a few things –

  • A similar approach has been used for C.Diff infections and has helped resolve gastrointestinal symptoms
  • There are many reports of abnormal gut microbe composition in children with ASD
  • Mouse models show that there is a connection between autism symptoms and the composition of the gut microbiome and autism symptoms
  • A previous study showed that modifying the gut microbiome with a special antibiotic resulted in short-term improvement in GI and autism behaviors (2).

Can you describe the MTT trial in ASD children?

Eighteen children with ASD, aged 7-16 participated in the trial. This process first involved a 2-week antibiotic treatment and a bowel cleanse. Then the children were treated with a stomach acid suppressant, followed by a microbiota transfer which was done daily for 7-8 weeks.

Is MTT invasive?

The vancomycin and bowel cleanse were liquid medications.  The initial high dose of microbiota was given either orally (mixed in milk or juice) or rectally.  All the maintenance doses were given orally.

Results of the MTT Trial

Was the MTT trial in ASD children successful?

The results of the first trial are promising. The results suggest that MTT is helpful for children with ASD ages 7–16 years. Here are more details.

  • There was approximately 80% reduction in gastrointestinal symptoms based on a standardized metric called the Gastrointestinal Symptom Rating Scale (GSRS.) There were significant improvements in symptoms of constipation, diarrhea, indigestion, and abdominal pain.
  • ASD-related behavior, as measured by standardized tests, showed improvement in all areas. The scores on CARS, which rates core ASD symptoms, decreased by 22% from beginning to end of the treatment. Children with ASD saw improvement in scores on assessments of social skill deficits, irritability, hyperactivity, lethargy, stereotypy, and abnormal speech. A test that evaluates adaptive behaviors like communication, daily living skills, and socialization, found that the average developmental age increased by 1.4 years.
  • Analysis showed that the changes were directly correlated to improvement in GI symptoms

Sounds great, but did the improvements stick?

We did a two-year follow up study which was published recently (3). The improvements we saw in GI symptoms were mostly maintained 2 years after treatment stopped.  Also, autism symptoms continued to improve, with a 47% decrease compared to baseline. At the beginning of the study, the majority (83%) of the participants were classified as “severe” on standardized rating scales assessing autism symptoms. By the 2-year follow up, only 17% were still classified as “severe.” 44% of the 18 children included in the trial no longer met the criteria for an ASD diagnosis.

Does this mean MTT is a proven treatment for ASD symptoms and co-occurring GI issues?

The initial results are promising. It’s too early to say this treatment is proven. That is why we need larger trials that are randomized, double-blind and placebo controlled.

What is the profile of non-responders? How many non-responders were there out of the 18?

Children were classified as non-responders if they had less than 50% reduction in gastrointestinal symptoms, measured on the standardized scale called GSRS.

90% of the children enrolled in the study had 70-100% improvement in GI symptoms. However, one child with severe constipation had no significant improvements. Another child only had a 30% reduction in severity of gastrointestinal symptoms. It is possible that a longer and/or higher dose could have helped them more.

What side effects were seen in this study?

At the start of the vancomycin (antibiotic) 12 of 18 participants had temporary worsening of irritability or hyperactivity, usually lasting only a few days.  One participant had a temporary rash from the vancomycin with natural orange flavoring, but it disappeared when switched to pure vancomycin.

The microbiota was generally well-tolerated, except that one participant had some nausea/vomiting with the initial high oral dose and was instead switched to a rectal dose which was well-tolerated.

Long term, after treatment ended, one participant had a temporary worsening of behavior for about 6 months, and then improved.

Discussion of “Do It Yourself” Approaches

MTT is “just” stool from another person, right? Why do we need FDA approval – why not try this at home?

We used a highly purified form of gut bacteria extracted from stool from healthy individuals.  Donors went through rigorous screening. The screening involved extensive questionnaires (similar to blood donors) to check for risk of infectious disease, as well as a careful check of GI history and requiring a normal body weight. The donated material was then extensive tested for pathogens and extensively processed, following FDA good manufacturing processes (GMP), resulting in a material that is more than 99% microbes. The final product was in liquid form which can be frozen. It was stored in −80 °C freezers and then delivered to families on dry ice every week during the study. Families were instructed to keep the material in a container with dry ice and thaw it shortly before use.

We believe our approach to MTT is safe because donors are screened using an approach that is based on years of experience and success with similar treatments for patients with severe gastrointestinal infections. The material is also prepared using a special process. We believe that much more needs to be understood about the gut microbiome before it can become a “do it yourself” therapy.

OK, so you are not in favor of “do it yourself” (DIY) approaches. But can my doctor do it?

The US Food and Drug Administration (FDA) has classified human stool as a biological agent, which has to be regulated to make sure of patient safety. This is similar to how blood is considered a biological agent that is regulated. Currently, FMT is only allowed by the FDA for patients with recurrent infections from a bacterium called Clostridium Difficile, or in research studies like ours which are reviewed by the FDA.

Enrolling In The Studies

Are you doing more studies?

Yes, we currently have a randomized, double-blind, placebo controlled adult study (age 18-60) designed for 84 participants that is actively enrolling. We are also planning a child study, ages 5-17 years.

How to enroll in the adult study?

Go to https://autism.asu.edu/ and fill out the application. One of the study coordinators will review and see if you meet exclusion and inclusion criteria. We will then verify the diagnosis of autism. The next step after that is screening blood tests for safety, followed by a thorough review of medical history by the study physician to look for risk factors like seizures.

What is the status of the child study? How will participants be recruited?

The child study can’t recruit until it receives FDA approval, gets funding and gets started. Currently, we’ve submitted an application for the child study to the FDA and are waiting for approval and trying to raise funding. In the meantime, you can sign up on the contact list. The contact list has over 400 children signed up already. Once approved by the FDA and the Institutional Review Board (IRB), we will advertise to everyone on the contact list, and participants will be assessed for inclusion and exclusion criteria.

Can we pay to ensure a place in the study?

We are not allowed to “sell” slots. The FDA does not allow it. When we receive approval for the child study, we will advertise the study and we will randomly select participants from those who apply within the initial deadline and meet the study criteria.

Would you enroll children with ASD who cannot speak or have minimal speech?

Our initial study required children to be able to communicate assent. In our next study we plan to only require assent if the children have an intellectual development level that is at least equivalent to a typically developing 7-year-old child.

What it will take to get FDA approval

We need to move this therapy through the FDA approval process. As mentioned before, the research team lead by Dr. James Adams is currently conducting a randomized, double-blind placebo-controlled Phase II trial which is enrolling 84 adults, ages 18-60.  We have also submitted an application for FDA approval of a double-blind placebo-controlled Phase II trial enrolling 50 children, ages 5-17.

Dr Adams is presenting on this topic at TACA’s upcoming National TACA Autism Conference. For more info:  https://tacanow.org/conference/west-coast/ 

For more information please contact Arizona State University:  https://autism.asu.edu/


  1. https://doi.org/10.1186/s40168-016-0225-7
  2. https://journals.sagepub.com/doi/10.1177/088307380001500701
  3. https://www.nature.com/articles/s41598-019-42183-0

9 thoughts on “Microbiota Transfer Therapy (MTT) Trial – An Update for Parents

Add yours

  1. My son is 3 non verbal… it’s sad the the age requirements are 5 and the developmental age is 7? I can’t even make sense of that. so much for early intervention 🙄

    1. Studies are expensive. If they had more funding, perhaps they could open it up to more patients?

      It may be worthwhile to contact ASU and see if you can sign up to participate in future studies.

  2. I visited the ASU website and I cannot find how to enroll in the contact list for the child study. The only one that was active was the recruitment for the adult study. Has anyone been able to find it?

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