Microbiome Therapy Advances for Reoccurring C. Diff

Diff, also known as Clostridioides difficile or C. difficile, is a type of bacterium that causes severe diarrhea and inflammation of the colon (colitis). This bacterium affects almost half a million Americans annually, and 1 in 6 will have a recurrence of C. Diff in the following 2-8 weeks. Major risk factors include age (65+), recently being hospitalized or in a nursing home, a compromised immune system, prolonged antibiotic use, and previously having contracted C. Diff. Many IBD patients will be diagnosed with C. Diff with 6% of hospitalized IBD patients contracting it. At the DDW, Digestive Disease Week, two new microbiome therapies for C. Diff were presented with the initial trial’s findings. 

The first microbiome therapy is called RBX2660, and contains live bacteria administered by enema. The second is SER-109, and is an oral mix of Firmicutes bacterial spores. These therapies differ from current treatments, and aim to help the recurrence of C. Diff. Today, C. Diff is treated with antibiotics, probiotics, and fecal microbiota transplant (FMT). FMT is not yet FDA approved, but has seen a spike in popularity as it has an 85% success rate for treating C. Diff. FMT consists of receiving healthy stool from a donor and is administered to the colon directly. While this approach has had good success, it takes some time to do all the screening necessary for both donor and patient. These new microbiome therapies would require less prep time, and could be more readily available pending FDA approval. 

RBX2660 has just undergone phase 3 trials, and followed patients for 6 months after to account for C. Diff recurrence. Treatment success rates reached just above 70%, compared to the placebo group of 58%. The raw data however, shows that men responded better than women with men showing higher efficacy advantage at 18.7 points over placebo, whereas women were 4.4 points over placebo. Although women’s numbers were lower, RBX2660 showed better efficacy overall. And those in this study who had C. Diff three times or more also showed better response in RBX2660 than previous treatments. Making it a promising up and coming treatment for C. Diff and reoccurring C. Diff.  

Another study done with RBX2660, which allowed patients with IBS and IBD to participate also showed promise with 75% of the 125 people remaining C. Diff recurrence free at 8 weeks, and 74% of participants stayed recurrent free through 6 months. In both these studies some adverse effects were noted, but none were severe or required extra treatment. Two patients were permanently pulled from the study, but it was determined that these symptoms were not a result of RBX2660. This second study is still in effect as they have a goal to enroll enough people to reach 500 to truly determine effect and efficacy.  

The second therapy presented was SER-109. This therapy is oral and consists of specific bacterial spores. 182 patients were randomized 1:1 medication and placebo. SER-109’s results showed greater success in younger, much older, and female patients versus RBX2660. It also did a slightly better job in treating those who had experienced three or more bouts with C. Diff. After the initial 8 weeks only 13% of those on SER-109 showed recurrence, whereas 40% of the placebo group had a recurrence of C. Diff. The advantage of SER-109 maintained its superiority at 24 weeks, showing 21% of C. Diff recurrence versus 47% in the placebo group. 

While neither company has announced official plans to receive market approval, these initial findings are more than promising for those struggling with C. Diff, and the recurrence thereof. These findings are especially encouraging for the 65+ and immunocompromised as they are at the most risk of contracting and having relapsing C. Diff. Both RBX2660 and SER-109 will undergo more testing in the near future to continue to prove their efficacy and potency. The gut’s microbiome is complex and not yet fully understood, but with therapies targeted to help the microbiome recover we are taking a huge step in the right direction regarding gut health and C. Diff.     

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