Microbiota Transfer Therapy for Children and Adults With Both Pitt Hopkins Syndrome and Gastrointestinal Disorders

Inclusion Criteria:

1. Children ages 5 to <18 years and adults ages 18 to < 55 years with Pitt HopkinsSyndrome (verified by genetic testing)
2. GI disorder as defined below that has lasted for at least 2 years.
3. No changes in medications, supplements, diet, or therapies in the 2 months prior tostart of treatment, and no intention to change treatments during Part 1 (allparticipants) and Part 2 (group B) of the clinical trial. The only exception is GImedications, which may be reduced if symptoms reduce, and any changes during the studywill be documented.
4. Review of last year of medical records by the study physician.
5. At least two previous trials of "standard of care" GI treatments that did notalleviate GI symptoms (constipation, diarrhea, bloating, gas, reflux, and/or abdominalpain). Standard of care treatments include laxatives, stool softeners, enemas,suppositories, or similar medications.

Exclusion Criteria:

1. Antibiotics in 2 months prior to start of treatment (topical antibiotics are allowed)
2. Probiotics in 2 months prior to start of treatment, or fecal transplant in last 12months. Foods naturally containing probiotics such as yogurt are allowed.
3. Tube feeding may be an exclusion criterion if the participant requires an unusual dietsuch as a liquid diet with low fiber.
4. Current severe gastrointestinal problems that require immediate hospital treatment (life-threatening)
5. Ulcerative Colitis, Crohn's Disease, diagnosed Celiac Disease, EosinophilicGastroenteritis, or similar conditions
6. Unstable, poor health (based on study physician's opinion), or active malignancy orinfection.
7. Recent or scheduled abdominal surgeries
8. Current participation in other clinical trials
9. Females who are pregnant or who are at risk of pregnancy and sexually active with amale partner without effective birth control. We will conduct a pregnancy test on allfemale participants 12 years and older as part of the screening and at each clinicalvisit. Males who are sexually active with a female partner without highly effective birthcontrol (IUD or birth control hormones).
10. Allergy or intolerance to the study medications: vancomycin, magnesium citrate, milkpowder with chocolate flavoring (which are included in MTP-101P), or the antacid.
11. Clinically significant abnormalities at baseline on the blood safety tests, andconfirmed on a second test. The tests include Comprehensive Metabolic Panel, andComplete Blood Count with Differential. Note that some abnormalities may occur due toPTHS, so only those likely to significantly increase risk in this study would begrounds for exclusion, at the discretion of the study physician. See detaileddiscussion at the end of this section on Interpreting Laboratory Results. re.Eligibility for Admission to Study.
12. Evidence of significant impairment of immune system, or taking medications that cancompromise the immune system, and thus increase risk if exposed to multiple-drugresistant bacteria.
13. Substantially decreased kidney function, as evidenced by estimated glomerularfiltration rate of <60 mL/min/1.73 m2. This is not normally reported for children onstandard laboratory metabolic panels, so in those cases we will use the NationalKidney Foundations Pediatric Glomerular filtration rate (GFR) Calculator to calculatethe pediatric GFR based on age/height, the Blood urea nitrogen (BUN) and serumcreatinine from our standard Comprehensive Metabolic Panel (CMP). [https://www.kidney.org/professionals/kdoqi/gfr_calculatorped] This calculator usesthe Creatinine-based "Bedside Schwartz" equation (2009) that seems to be the mostcommonly used calculation for this purpose.
14. Participants who are breastfeeding.