An eight-week study evaluating a microbiome designed to reduce the relative risk of Clostridium difficile recurrence at up to 8 weeks was not achieved, according to a statement from the manufacturer, Seres Therapeutics, Inc. 

The phase 2 study enrolled 89 people with multiply recurrent Clostridium difficile infection (CDI), defined as 3 or more recent recurrences, in a randomized, double-blind, placebo-controlled 24-week study conducted to evaluate the safety and efficacy of SER-109. 

The researchers randomly assigned subjects at a 2:1 ratio with 59 subjects receiving SER-109 and 30 subjects receiving placebo. SER-109 was administered orally as a single dose, of 1 X 108 bacterial spores, following the completion of antibiotic treatment for CDI. The study was conducted at 36 centers across the United States. 

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CDI recurrence occurred in 26 of 59 people who received SER-109, compared to 16 of 30 who received placebo, according to the statement. The relative risk of CDI recurrence for the placebo population compared to the SER-109 population was not statistically significant. 


Seres Therapeutics Announces Interim Results from SER-109 Phase 2 ECOSPOR Study in Multiply RecurrentClostridium Difficile Infection. Press release. 2016.