Prebiotic Galacto-oligosaccharide and Acute GVHD

Humans carry on the order of 100 trillion microbial cells (the microbiota),which play a major role in normal health as well as disease pathogenesis. In the gut, the microbiota interact with the intestinal epithelium and immune system to regulate inflammation and metabolism. The impact of the microbiota on GVHD and other clinical outcomes may be mediated by bacterial metabolites such as short chain fatty acid (SCFAs). In particular, the SCFA butyrate has been shown to be a preferred fuel source of human colonic epithelial cells and essential for normal differentiation of regulatory immune cells in the intestine, which in turn may decrease GVHD. This is supported by murine studies, in which manipulating the gut microbiota to increase microbial SCFA production or by direct administration (oral gavage) of butyrate has been shown to improve HCT outcomes, including protection from GVHD Manipulating the gut microbiota in HCT to decrease the risk of GVHD could potentially be done using several methods, namely prebiotics (dietary carbohydrates or fibers), probiotics (live bacteria), and fecal transplantation. In contrast to live bacteria, prebiotics are dietary carbohydrates classified as nutritional supplements that can sustain gut bacteria, regulate gastrointestinal transit time, and foster cooperative metabolic networks between enteric microbes. Because prebiotics encourage the growth of existing bacteria rather than introducing new organisms, they may be safer. Moreover, bacterial fermentation of prebiotics may yield SCFA. The purpose of this study is to determine whether the carbohydrate prebiotic (dietary supplement) known as galacto-oligosaccharide (GOS) can modulate the microbiome (the bacteria in the gut) and help prevent graft-versus host disease (GVHD) after allogeneic stem cell transplant. The study has two two parts. In phase 1, three dose levels 0.75g/day (25% maximum dose, D1), 1.5g/day (50% maximum dose D2), and 2.9g/day (maximum dose, D3) will be evaluated to find out the provisional maximum tolerated dose (pMTD) of GOS to be used in phase 2. In phase 2, using pMTD of GOS, participants will be randomized to receive GOS or a placebo (maltodextrin, a common food additive that is not known to affect the microbiome) so that the effect of GOS can be determined. Note that if the pMTD is D3, there will be a D1 and D2 lead-in period similar to the Phase 1 study however if the pMTD is D2, there will only be a lead-in with D1 and if pMTD is D1, there will only be one dose with no lead-in. The study will generate important data on gut microbiota responses to help tailor or personalize future prebiotic therapies to patients and their microbiota.