Rebiotix Inc. said RBX-2660, its standardized, non-antibiotic, microbiome-based therapy designed to reduce Clostridioides difficile (C. diff) infection recurrences, notched positive preliminary results on the primary efficacy endpoint of its ongoing pivotal phase III trial.

The primary endpoint was the absence of C. diff diarrhea without the need for treatment as assessed by a subject interview and a physical exam in the first, fourth and eighth week following the treatment’s administration by enema.

The company did not release any specific data or statistics from the preliminary study results.

The microbiome is a community of naturally occurring germs in and on the body, including the skin, gut, mouth, respiratory or urinary tracts. C. diff is a bacterium that causes diarrhea and colitis, inflammation of the colon. The CDC estimates C. diff causes nearly half a million illnesses in the U.S. each year and that about one in every six patients will get it again two to eight weeks later. Also, within a month of being diagnosed, one in every 11 patients over the age of 65 dies of a health care-associated C. diff infection. The risk factors include age (being 65 or older), recent hospitalizations, a weakened immune system and a previous C. diff infection or known exposure to germs.

Antibiotics are the current standard of care, but the condition has become more frequent, severe and harder to treat.

Roseville, Minn.-based Rebiotix, part of Ferring Pharmaceuticals Inc., of Saint-Prex, Switzerland, launched the prospective, randomized, multicenter, double-blinded, placebo-controlled phase III study of a microbiota suspension of intestinal microbes in July 2017. The trial also includes a safety assessment for patients several months after receiving the drug, providing additional insight into the use of microbes as a therapy.

The complete data package is expected sometime in the second half of 2020. The therapy has fast track, orphan and breakthrough therapy designations from the FDA.

The trial’s enrollment began in early February and it is estimated to end in October.

Rebiotix is one of three biotechs steering the Microbiome Therapeutics Innovation Group, an independent 501(c)(6) coalition of companies leading the research and development of FDA-approved microbiome therapeutics and microbiome-based products to address unmet medical needs, improve clinical outcomes and reduce health care costs. The other two steering companies in the group are Seres Therapeutics Inc., of Cambridge, Mass., and Vedanta Biosciences Inc., also of Cambridge. Other companies involved in the group include Siolta Therapeutics, Takeda Pharmaceutical Co. and Seed Health, a venture-backed microbial sciences company.

In late March, Seres completed enrollment in its phase III trial of SER-109, an oral microbiome therapeutic that received orphan drug and breakthrough therapy designations by the FDA. SER-109 is being studied for use in preventing recurrent C. diff infection. The multicenter, randomized, placebo-controlled study, which has enrolled 181 patients, was designed to enroll 188 patients. Seres decided to halt enrollment as a result of the COVID-19 pandemic. The study’s primary endpoint is the reduction of C. diff infection recurrence at up to eight weeks following SER-109 administration. Seres said it expects to report study results in mid-2020, as it had planned.

Right behind Seres is Finch Therapeutics Group, which completed enrollment of its multicenter, placebo-controlled phase II trial of CP-101, an oral, microbiome therapeutic that was granted fast track and breakthrough therapy designations by the FDA. It is being investigated for the prevention of recurrent C. diff infections. A total of 206 participants were randomized at 51 sites across the U.S. and Canada. Finch expects to report top-line preliminary efficacy and safety results at the end of the second quarter of 2020.

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