A live biotherapeutic product for adult allogeneic hematopoietic cell transplantation recipients: a partially randomized, placebo-controlled phase 1b trial.

Gastrointestinal (GI) microbiome disruption and impaired GI barrier integrity increase the risk of bloodstream infection (BSI) following allogeneic hematopoietic cell transplant. Here we report results from a two-cohort (open-label, n = 15; randomized, placebo-controlled, n = 45) phase 1b study of SER-155, an investigational, cultivated, multi-strain, oral live biotherapeutic designed to address GI microbiome disruption GI epithelial barrier integrity in allogeneic he
Gastrointestinal (GI) microbiome disruption and impaired GI barrier integrity increase the risk of bloodstream infection (BSI) following allogeneic hematopoietic cell transplant. Here we report results from a two-cohort (open-label, n = 15; randomized, placebo-controlled, n = 45) phase 1b study of SER-155, an investigational, cultivated, multi-strain, oral live biotherapeutic designed to address GI microbiome disruption GI epithelial barrier integrity in allogeneic hematopoietic cell transplant recipients. In cohort 2, 34 of 45 participants received either SER-155 treatment (n = 20, SER-155 following microbiome conditioning with oral vancomycin), or placebo (n = 14), and subsequently received transplant. For the primary safety endpoint, SER-155 was well tolerated, with a safety profile comparable to placebo, no treatment-related serious adverse events and no infections with SER-155 species; the most common adverse events were diarrhea and nausea. Four participants in cohort 1 and four participants in cohort 2 (two participants in the SER-155 arm and two in the placebo arm) died during the study; none was attributable to SER-155. For the primary pharmacokinetic endpoint, engraftment was detected for 16 of 16 SER-155 strains, with a median of 11.5 strains detected after the first treatment course. The key secondary efficacy endpoint revealed a significantly lower incidence of BSI with SER-155 versus placebo (10.0% versus 43%; OR 0.15; 95% CI 0.01-1.13; P = 0.0423; 77% relative risk reduction). Other secondary efficacy endpoints (GI infection, acute graft-versus-host disease ≥grade 2, febrile neutropenia and a composite endpoint of BSI, GI infection or acute graft-versus-host disease) were not statistically significant. The secondary pharmacodynamic endpoint of GI domination by Enterococcus and Enterobacteriaceae spp. was not achieved. ClinicalTrials.gov identifier: NCT04995653 .




