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Clostridium difficile Infection (CDI)

CDI is one of the top three most urgent antibiotic-resistant bacterial threats in the United States, according to the Centers for Disease Control. It is the leading cause of hospital-acquired infection in the United States and is responsible for the deaths of approximately 29,000 Americans each year.

The current standard of care for CDI is to treat with antibiotics. While antibiotic treatment may resolve the acute infection, it can worsen dysbiosis in individuals, potentially making patients more susceptible to a recurrence of CDI. Recurrent CDI patients receive multiple rounds of antibiotics that can worsen dysbiosis and thus make it more likely that they will relapse.

Seres Therapeutics’ development candidate SER-262 is an investigational oral microbiome therapeutic for patients with primary Clostridium difficile infection. An Ecobiotic® rationally-designed, fermented microbiome therapeutic derived by a manufacturing process that does not require human donor material, SER-262 is the first synthetically-derived and designed microbiome therapeutic ever to reach clinical-stage development. In addition, Seres’ program SER-109 continues to be evaluated in a Phase 2 study in multiply recurrent CDI.

Seres Therapeutics’ lead development candidate, SER-109, is an investigational oral microbiome therapeutic for the prevention of recurrent Clostridium difficile infection (CDI) in adults with multiply recurrent CDI. The FDA has granted SER-109 both Breakthrough Therapy and Orphan Drug designations.

SER-109 is a patient-friendly, single-dose capsule that may repair the underlying cause of recurrent CDI—dysbiosis, which is a disrupted state of the microbiome. SER-109 was developed using computational design insights suggesting that a complex spore ecology includes keystone organisms that could address the underlying dysbiosis and return the microbiome to a healthy state. SER-109 is an ecology of bacterial spores enriched and purified from healthy, screened human donors.

Seres plans to initiate a new SER-109 Phase 2 clinical study (ECOSPOR III) in patients with multiply recurrent Clostridium difficile infection. The ECOSPOR III study design was finalized following a positive Type B meeting with the FDA. The FDA has agreed that this new trial may qualify as a pivotal study with achievement of a persuasive clinical effect and addressing FDA requirements, including clinical and statistical factors, an adequately sized safety database, and certain CMC parameters.

The SER-262 Phase 1b study, a 24-week randomized, placebo-controlled, dose escalation study is expected to enroll approximately 60 patients who have experienced a first episode of CDI. The primary endpoint of the study will compare the CDI recurrence rate between the SER-262 and placebo groups at up to 8 weeks after dosing.

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