BACKGROUND: Novel therapies are needed to treat HE, and microbiome modulation is a promising target. VE303 is a defined consortium of 8 purified, clonal bacterial strains, known to produce metabolites that may be beneficial in HE. We evaluated the safety and efficacy of VE303 to treat HE. METHODS: We performed a single-center, randomized, placebo-controlled trial of VE303 in adult patients with a history of overt HE (NCT04899115). Eligible patients were taking lactulose and rifaximin, had no recent systemic antibiotics, and had MELD ≤20. All patients received 5 days of oral vancomycin followed by randomization to 14 days of VE303 or placebo (2:1). The primary endpoints were incidence of serious adverse events and change in psychometric HE score (PHES) from baseline to 4 weeks after treatment. Stool samples underwent metagenomic sequencing and metabolite quantification. RESULTS: Eighteen patients completed the trial, 56% men, with a mean age of 59 years and a mean MELD of 11. Patients who received VE303 had a mean change in PHES of +1.5 versus -1.0 in those who received a placebo (p=0.20). Two of the 12 patients who received VE303 had at least 1 serious adverse event (all overt HE hospitalizations), compared with 0/6 patients who received a placebo. In the patients who received VE303, 2 of 8 strains engrafted in >
50% of patients. Both VE303 strain engraftment and increased stool butyrate production had a trend toward improved PHES. CONCLUSIONS: VE303 was well tolerated in patients with cirrhosis and a history of overt HE, leading to the engraftment of certain VE303 strains and a higher percentage of patients with improved PHES.