A Study of LBP-MARCO and Ruxolitinib in People With Graft-Versus-Host Disease (GVHD)

Inclusion Criteria:

* Age ≥ 18
* Ability to swallow capsules
* Have undergone allo-HCT from any donor source
* Upper GI aGVHD stage 1 and/or lower GI aGVHD stage 1-4. aGVHD affecting other organs (e.g. skin, liver) are allowed

  * Steroid-refractory, steroid-dependent or intolerant, defined as:
  * Progressive (i.e., increase in stage of the lower GI tract) after 3 days of treatment with corticosteroids (≥1 mg/kg/day prednisone or IV equivalent), or
  * Failure to improve (i.e., decrease in stage in the GI tract) after 5 days of corticosteroid treatment (≥1 mg/kg/day prednisone or IV equivalent), or
  * Incomplete response after \>28 days of corticosteroids, or
  * Corticosteroid dependent (inability to taper prednisone \<1 mg/kg/day or recurrence of aGVHD activity or flare during steroid taper), or
  * Corticosteroid intolerance (unacceptable toxicity due to the use of corticosteroids).
* Absolute neutrophil count (ANC) ≥0.5 x10\^9/L and platelets \>20,000/mm3. Use of growth factor supplementation and platelet transfusional support is allowed
* Ability to start ruxolitinib therapy for aGVHD

Exclusion Criteria:

Has received more than one systemic treatment for aGVHD other than corticosteroids +/- CNI or sirolimus prophylaxis or treatment

* Active GI bleeding requiring intervention or transfusional support
* Toxic megacolon
* Active uncontrolled infection requiring systemic antibiotic treatment including persistent bacteremia (controlled infection receiving definitive therapy for 48 hours prior to enrollment are eligible).
* Treatment with broad spectrum antibiotic with anaerobic coverage for 48 hours prior to enrollment
* Elevated total bilirubin not caused by GVHD or Gilbert's disease of \>5 x upper limit of normal (ULN)
* Use of investigational agent within 14 days pre-treatment
* Evidence of current uncontrolled cardiovascular conditions, including uncontrolled hypertension, uncontrolled cardiac arrhythmias, symptomatic congestive heart failure, unstable angina, or myocardial infarction within the past 6 months
* Uncontrolled psychiatric illness
* Patients with an active secondary malignancy or prior malignancy requiring systemic therapy within the past 3 years. Exceptions include adequately treated localized non-melanoma skin cancer (basal cell carcinoma and squamous cell carcinoma), as well as localized prostate cancer considered low risk and stable under treatment or surveillance
* Female patient who is pregnant or breastfeeding
* Known allergy or sensitivity to ruxolitinib and/or MARCO live biotherapeutic