Fecal transplant to restore gut microbiome before CAR T therapy for relapsed or refractory B‑cell lymphoma

Inclusion Criteria:

* Documented informed consent of the participant and/or legally authorized representative.

  * Assent, when appropriate, will be obtained per institutional guidelines
* Agreement to allow the use of archival tissue from diagnostic tumor biopsies

  * If unavailable, exceptions may be granted with study principal investigator (PI) approval
* Age: ≥ 18 years
* Karnofsky performance status (KPS) ≥ 60
* Confirmed diagnosis of relapsed/refractory CD19 B-cell lymphomas of diffuse large B cell lymphoma (DLBCL), transformed follicular lymphoma (tFL), or double-hit lymphoma (DHL) and scheduled to receive commercial CAR T treatment of YESCARTA ® for their diagnosis
* Fully recovered from the acute toxic effects (except alopecia) to ≤ grade 1 to prior anti-cancer therapy
* Exposure to high-risk antibiotics within 90 days of consent. High-risk broad-spectrum antibiotics include carbapenems (meropenem, imipenem, doripenem), anti-pseudomonal antibiotics (cefepime, piperacillin-tazobactam, ceftazidime) or anaerobic antibiotics including metronidazole, clindamycin, amoxicillin-sulbactam, and vancomycin
* Clinical laboratory and organ function criteria per standard of care to CAR T patients at City of hope: (To be performed within 30 days prior to leukapheresis)
* Seronegative for HIV antigen (Ag)/antibody (Ab) combo, hepatitis C virus (HCV), active hepatitis B virus (HBV) (surface antigen negative)

  * HIV-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months are eligible for this trial.
* Meets other institutional and federal requirements for infectious disease titer requirements

  * Note: Infectious disease testing to be performed within 28 days prior to day 1 of protocol therapy
* Women of childbearing potential (WOCBP): negative urine or serum pregnancy test

  * If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required
* Agreement by females and males of childbearing potential\* to use an effective method of birth control or abstain from heterosexual activity for the course of the study through at least 12 months after the last dose of protocol therapy.

  * Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for \> 1 year (women only)

Exclusion Criteria:

* Major surgery in 4 months preceding enrollment
* No live vaccine in 30 days prior to enrollment
* Inability to swallow capsules or history of disorder with Inability to swallow FMT capsules
* History of inflammatory bowel disorder, irritable bowel disorder
* Severe food allergies
* History of chronic aspiration
* History of behavioral disorders including substance abuse disorders which per discretion of primary investigator will interfere with safe conduct and compliance to study treatment
* History neurocognitive disorder which per discretion of primary investigator will interfere with safe conduct and compliance to study treatment
* Diagnosis of primary immunodeficiency
* Active second malignancy requiring treatment except non-melanoma skin cancer or carcinoma in situ-cervix, bladder or to non-metastatic prostate cancer which does not require treatment
* Uncontrolled bacterial, fungal, or viral infection confirmed using clinical, laboratory and radiological findings requiring administration of intravenously (IV) antimicrobials
* Any clinical, laboratory or radiologic findings per discretion of primary investigator will interfere with safe conduct of study treatment and compliance with study procedures
* Any other condition that would, in the Investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
* Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)