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Seres' microbiome therapy misses Phase II endpoint

July 29, 2016 7:00 AM UTC

Seres Therapeutics Inc. (NASDAQ:MCRB) sank $24.83 (69%) to $10.94 on Friday, shedding nearly $1 billion in market cap, after it said microbiome-based therapy SER-109 missed the primary endpoint in the 89-patient Phase II ECOSPOR study to prevent recurrent Clostridium difficile infection (CDI). SER-109 did not significantly reduce the relative risk of CDI recurrence at up to eight weeks vs. placebo, with CDI recurrence in 44% of patients receiving SER-109 vs. 53% for placebo.

In patients aged 65 and older, CDI recurrence occurred in 45% of patients receiving SER-109 vs. 80% for placebo. In patients younger than 65, the rates were 43% for SER-109 and 27% for placebo. Both subgroup analyses were prespecified. ...