Seres Therapeutics announced that the Food and Drug Administration (FDA) has granted Orphan Drug designation to SER-109, an oral agent currently in a Phase 2 clinical trial for the prevention of recurrent Clostridium difficile infection (CDI) in adults. SER-109 is being investigated as a new therapeutic modality to treat recurrent CDI by correcting a dysbiosis of the human microbiome, which is an underlying cause of the condition.

Results from a Phase 1b/2 study of SER-109 in recurrent CDI patients showed that 87% of patients achieved efficacy endpoint per protocol, and 97% of patients achieved a clinical cure, which was defined as the absence of CDI requiring antibiotic treatment during the eight-week period after SER-109 dosing.

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Seres is currently conducting a multicenter, randomized, placebo-controlled Phase 2 clinical study to assess the efficacy and safety of SER-109 in preventing recurrent CDI. The primary outcome measure is the absence of CDI through eight weeks following administration of SER-109 compared to placebo. Results from this study are expected to be available in the middle of 2016.

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