The Food and Drug Administration on Wednesday approved a new kind of drug designed to restock the gut with helpful bacteria after recurring bouts of a debilitating intestinal infection.
Developed by Massachusetts biotechnology company Seres Therapeutics, the drug is the second microbiota therapy that’s been cleared for use in the U.S., but is the first taken orally. It is meant to prevent recurrent infections of a bacterium called Clostridioides difficile, or C. diff., in adults 18 years or older.
C. diff. infections cause diarrhea and, in some cases, life-threatening colon inflammation. They are more common in adults aged 65 years and older, and often occur after a hospital stay. While antibiotics can tamp down infections, the drugs can also kill helpful bacteria, letting C. diff. spores take root again after treatment is stopped.
Seres’ pill is made from human fecal matter that’s donated by screened individuals and purified. It contains Firmicutes spores, which are associated with a healthy microbiome capable of resisting C. diff. colonization.
“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,” said Peter Marks, head of the FDA’s Center for Biologics Evaluation and Research, in a statement.
The drug’s approval comes after more than a decade of work by Seres to bring a microbiota-based treatment to market. The biotech, which trades under the ticker “MCRB,” was founded by Flagship Pioneering and went public in 2015.
But Seres hit a major setback one year later when its treatment failed a Phase 2 trial in 2016, sinking shares in the company. After adjusting and advancing the drug into Phase 3 testing, Seres reported data in 2020 that showed treatment reduced the risk of C. diff. infections recurring.
In that study, 12% of participants given Vowst experienced infection recurrence, compared to 40% who received placebo. The most common side effects were abdominal bloating, fatigue, constipation, chills and diarrhea, the FDA said.
While Seres will be second to market with a microbiota-based treatment for C. diff., it believes it can compete because of the convenience of Vowst’s oral administration. In December, the FDA approved Ferring Pharmaceuticals’ Reybota, which is prepared from stool donations and given rectally.
Although both Seres and Ferring screen donated stool before making their drugs, there is still some risk their treatments could transmit infectious pathogens. Still, when experts reviewed Ferring’s drug last September, they viewed the risk as less than with unregulated fecal transplants, which have been allowed by the FDA under its “enforcement discretion.”
The FDA also warned Vowst could contain food allergens, although it said the potential for treatment to cause adverse reactions as a result is unknown.
Seres will charge $17,500 per course of therapy with Vowst, said Terri Young, Seres’ chief commercial and strategy officer, on a call with investors Thursday. The company estimates commercial insurers will cover more than half of people taking the drug, but cautioned it might take time before they agree to broadly cover it without requiring extra paperwork.
Medicaid and Medicare coverage will take longer to put in place, she said.
Other companies are working to follow Seres and Ferring in the microbiome field, with mixed results.
Vedanta Biosciences has raised more than $100 million from investors including the Bill & Melinda Gates Foundation to advance a bacteria-containing capsule it’s developing.
Data from a Phase 2 study published in 2021 showed less than 14% of trial participants on the highest dose of Vedanta’s drug had a recurrent C. diff infection after eight weeks, compared with about 46% of those on placebo.
But one-time rival Finch Therapeutics earlier this year halted its microbiome work after running low on funding, nearly a decade after it was formed and three years after reporting mid-stage data. Evelo Biosciences, another Flagship-backed developer of microbe-based therapies, said Wednesday it is refocusing its research and cutting staff.
With the FDA approval, Seres is due $125 million from food and beverage company Nestlé under a 2021 deal it signed with Seres to help develop and market the drug. Nestlé could pay Seres as much as $225 million more if certain sales goals are met.
Editor’s note: This story has been updated with additional information on Vowst's pricing and launch.