Seres Shares Trial Data for Vowst, the FDA-Approved Microbiome Therapeutic

On April 26, Seres Therapeutics’ Vowst (fecal microbiota spores, live-brpk) became the first and only US Food and Drug Administration (FDA)-approved orally administered microbiota-based therapeutic.

Vowst, formerly called SER-109, was approved to prevent recurrent Clostridioides difficile infection (rCDI) in adults. The microbiome therapeutic competed metabolically with C difficile, restoring colonization resistance in the gut.

At this week’s 2023 Digestive Disease Week (DDW 2023) Annual Meeting, Seres shared phase 3 data from their open-label ECOSPOR IV clinical trial, which evaluated Vowst for the prevention of rCDI following antibacterial treatment.

The randomized, placebo-controlled study examined the safety and effectiveness of Vowst in 263 adults with rCDI, including in first recurrence patients. The investigators determined whether Vowst was more effective than placebo in reducing rCDI after 8 weeks.

In an oral presentation entitled “Durability of the Clinical Response to SER-109, an Investigational Oral Microbiome Therapeutic, in a Phase 3 Open-Label Trial (ECOSPOR IV) in Patients with Recurrent Clostridioides Difficile Infection,” Seres shared data demonstrating that 91.3% of the study patients who received Vowst achieved a significant clinical response at week 8. Through week 24, 94.6% of these participants maintained the response.

“In the ECOSPOR IV phase 3 open-label single-arm study, high clinical response rates were achieved at week 8 and continued into week 24 following Vowst treatment, regardless of the number of prior CDI infections,” said Lisa von Moltke, MD, the Chief Medical Officer of Seres.

In addition to participants with a first recurrence, the study population included patients with multiple comorbidities. Seres noted most adverse events were mild to moderate in severity and dissipated quickly. Reported in ≥ 5% of participants, the most common adverse reactions were abdominal distension (31.1%), fatigue (22.2%), constipation (14.4%), chills (11.1%), and diarrhea (10.0%).

A subgroup analysis revealed rates of rCDI were 8.7% among all participants, 6.5% for patients with a first recurrence, 9.7% for patients with 2 or more recurrences, 4% for patients younger than 65 years of age, 13.1% for patients 65 years and older, 8.9% in patients who received vancomycin, 8.3% in patients who received fidaxomicin, 10.8% in males, 7.8% in females, 4.3% in patients with a qualifying episode defined only by PCR, and 10.4% in patients with a qualifying episode by toxin with or without PCR.

Vowst contains a consortium of highly purified Firmicutes spores, which works to repair a gut microbiome damaged by Clostridioides difficile. You can read Contagion’s past coverage of the microbiota-based oral therapeutic here.