FDA Approves First Orally Administered Fecal Microbiota Product for Recurrent C. Diff


Through 8 weeks after treatment, C. difficile recurrence in SER-109-treated participants was lower compared to placebo-treated participants.

The FDA has approved SER-109 (Vowst, Seres Therapeutics), the first fecal microbiota product that is taken orally for the prevention of the recurrence of Clostridioides difficile (C. diff) infection (CDI) in individuals 18 years of age and older, following antibacterial treatment.

CDI is one of the most common health care-associated infections in the United States and is associated with between 15,000 and 30,000 deaths each year. Certain situations, such as taking antibiotics to treat an infection, can impact the gut microbiome and change the balance of microorganisms in the gut, allowing C. diff to multiply and release toxins causing diarrhea, abdominal pain, and fever.

In some cases, it can cause organ failure and death. Other risk factors that can increase the risk of CDI as well, including being over 65 years of age, hospitalization, living in a nursing home, a weakened immune system, or a previous history of CDI.

After recovering from the infection, individuals can experience recurrent CDI. The risk of additional recurrences increases with each infection and treatment options for recurrent CDI are limited. However, administering fecal microbiota is believed to facilitate restoration of the gut flora to prevent further episodes.

SER-109 offers a new option for fecal microbiota administration. The dosing regimen is 4 capsules taken once daily, orally, for 3 consecutive days. It contains live bacteria and is manufactured from human fecal matter that has been donated by qualified individuals.

Although the donors and donated stool are tested for a panel of transmissible pathogens, treatment with SER-109 does carry a risk of transmitting infectious agents. It is also possible for it to contain food allergens, although the potential to cause adverse reactions due to food allergens is unknown.

The efficacy of SER-109 was evaluated in a randomized, placebo-controlled clinical study in which 89 participants received SER-109 and 93 received placebo. Through 8 weeks posttreatment, C. diff recurrence in SER-109-treated participants was lower compared to placebo-treated participants (12.4% versus 39.8%).

The safety of SER-109 was evaluated in a randomized, double-blind, placebo-controlled, clinical study and an open-label clinical study conducted in the United States and Canada. Participants had recurrent CDI, were between 48 and 96 hours post-antibacterial treatment, and had controlled symptoms.

In total, 346 individuals 18 years of age and older with recurrent CDI received all scheduled doses of SER-109. In an analysis among 90 recipients, when compared to 92 placebo recipients, the most commonly reported adverse effects, which occurred at a greater frequency than reported by placebo recipients, were abdominal bloating, fatigue, constipation, chills, and diarrhea.

“Today’s approval provides patients and health care providers a new way to help prevent recurrent C. difficile infection,” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, in a press release. “The availability of a fecal microbiota product that can be taken orally is a significant step forward in advancing patient care and accessibility for individuals who have experienced this disease that can be potentially life-threatening.”


FDA Approves First Orally Administered Fecal Microbiota Product for the Prevention of Recurrence of Clostridioides difficile Infection. News release. FDA. April 26, 2023. Accessed April 27, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-first-orally-administered-fecal-microbiota-product-prevention-recurrence-clostridioides

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