About the Study

An open-label clinical study evaluating an investigational medication for recurrent C. diff infection is now enrolling. If you have C. diff that has recurred after antibiotic treatment, you may qualify to participate.

This investigational medication, called SER-109, has shown promise at breaking the cycle of recurrence in C. diff. All patients in the study will receive treatment with SER-109.


About SER-109

SER-109 is an oral capsule containing bacteria that normally exist in a healthy human gut. The bacteria in SER-109 have been chosen specifically for their ability to restore a damaged gut microbiome, breaking the cycle of C. diff recurrence.

In a Phase 3 clinical trial, SER-109 significantly reduced the recurrence of C. diff infection.

Patients taking SER-109 remained free of C. diff infection 87.6% of the time at 8 weeks while patients taking placebo (dummy) medication only remained free of C. diff infection 60.2% of the time.


C. diff recurrence after antibiotic treatment

The most common treatment today for C. diff infection is antibiotics. However, antibiotic treatment alone is ineffective. This is because C. diff exists in two forms within the gut: as both active bacteria and inactive spores.

Antibiotics don’t kill C. diff spores, allowing them to germinate and grow after antibiotics are completed. Repeated antibiotic exposure also depletes beneficial bacteria in the microbiome of the gut that inhibit C. diff. This can lead to a vicious cycle of recurrence.

Effective C. diff treatment requires a two-pronged approach: Killing C. diff bacteria and inhibiting spore germination.


How SER-109 is different than antibiotics

Rather than killing C. diff bacteria, like antibiotics do, SER-109 is designed to replenish the gut bacteria which research indicates are protective against C. diff in the healthy human gut. The bacterial spores included in SER-109 germinate in the gut and compete for the same nutrients that C. diff spores need to germinate. They also make chemicals that inhibit C. diff spores from germinating. Therefore, when delivered after antibiotic treatment, SER-109 may reduce C. diff recurrence. SER-109 bacterial spores come from the stool of healthy donors and are aimed at returning the gut bacteria to its healthy state.


How the microbiome contributes to C. diff infection

Research shows that C. diff infection requires two ingredients: Exposure to C. diff bacteria, and a disrupted microbiome in which C. diff can take root.

One common source of microbiome disruption is broad-spectrum antibiotics. By killing off both good and bad bacteria, broad-spectrum antibiotics can create conditions favorable to C. diff infection. Antibiotic treatment will kill the active, toxin-producing C. diff bacteria (leading to symptom resolution), but the C. diff spores may remain. These spores can then germinate into the form that produces the toxin, causing the return of symptoms or recurrence, if healthy bacteria do not return in time to reverse the disrupted microbiome. More than 25% of people with C. diff infection treated solely with antibiotics will have their infection recur at least once.

Frequently Asked Questions About This Study

What can I expect if I enroll in the study?

If you enroll in the study, you are guaranteed to receive the active study drug, SER-109. You will have a minimum of 2 clinic visits and up to 12 telephone visits over 24 weeks. At one of your clinic visits you will be given 4 capsules of SER-109 which are taken orally (by mouth). Over the subsequent 2 days you will take an additional 4 capsules of SER-109 each day. All treatment and visits will be provided at no cost to you. You may also be entitled to reimbursement for your time and travel costs.

Is there any cost to participate?

There will be no cost to you or your insurance provider for the investigational medication (SER-109) or for any of the procedures connected with your participation in the study. All study-related treatment and visits will be provided at no cost to you.

Where is this study offered?

Click here to view a map of study sites, or email us via the contact form if you’d like help locating a site near you.

Do I qualify?

You may qualify to participate if you meet the following criteria:

  • Are 18 years or older,
  • Have had a C. diff infection in the past,
  • Are now experiencing 3 or more unformed bowel movements per day over two consecutive days (potential current C. diff infection), and
  • Have been told by your physician you may have to take antibiotics.

If you think you may qualify, contact us to learn more.

How is SER-109 different from fecal microbiota transplantation (FMT)?

SER-109 is different from FMT in three important ways:

  1. Purity
    FMT uses minimally processed stool, which can contain viruses, bacteria, parasites and fungi that can cause illness in the recipient. The U.S. Food and Drug Administration has issued several safety alerts about cases where pathogen transmission by FMT has occurred. By contrast, SER-109 undergoes specific purification steps to remove unwanted viruses, bacteria, parasites and fungi. This reduces the risk of pathogen transmission to a level that cannot be achieved through donor screening alone.
  2. Manufacturing
    FMT preparations vary based on the clinic or provider performing the FMT. Seres’ microbiome therapeutics, on the other hand, are manufactured in a state-of-the-art bioprocessing facility, with rigorous testing to ensure product purity.
  3. FDA Oversight
    The use of FMT for the treatment of recurrent C. diff infection is not subject to the rigorous safety monitoring and oversight that are standard requirements for investigational drugs.

Seres’ microbiome therapeutics, in contrast, are being evaluated in controlled clinical studies with FDA oversight. Each study is conducted under an Investigational New Drug application (IND) with rigorous safety monitoring and reporting procedures.

Why should I enroll in a clinical study?

Clinical studies are extremely important to the advancement of science and medicine. Clinical studies look at investigational treatments, medical procedures, and devices to determine if they work and are safe to use. These trials also look for better ways to manage diseases and improve the quality of life for those with chronic illness.

Deciding to participate in a clinical trial is a personal decision and the reasons for participating are different for each person. For anyone considering participation in a clinical trial, it’s important to look carefully at all of the factors, such as safety, potential side effects and other pros and cons of the trial.

There are many benefits to participating in a clinical trial. You are able to take an active role in your health care, gain access to new investigative treatments, advance medical knowledge, and help advance the knowledge and treatment options for other patients with C. diff.

I have other questions — how can I learn more?

We’d love to hear from you! Contact us via the form here and a member of our team will respond to your message as soon as possible.