Rebiotix, a Ferring Company, and its parent Ferring Pharmaceuticals Group said today their microbiome-based treatment candidate RBX2660 showed positive preliminary Phase III results in patients with Clostridioides difficile (C. diff) infections.

As a result, the companies said, RBX2260 is the world’s first standardized, non-antibiotic, microbiome-based therapeutic to achieve safety and efficacy in a pivotal study. The companies did not disclose specifics in their announcement, and no results were posted on The trial’s primary completion date is June, and a full data package is not expected to be completed until the second half of this year.

RBX2260 met its primary outcome measure in the Phase III PUNCH CD3 trial (NCT03244644) of favorable efficacy compared to placebo measured at 8 weeks after treatment. The 267-patient study defined efficacy as the absence of C. difficile diarrhea without the need for retreatment as assessed by subject interview and physical exam 1, 4, and 8 weeks after administration of the study treatment.

“As a first-in-class, potentially paradigm-changing technology, we look forward to discussing our final data with the FDA in the latter part of this year,” Lee Jones, CEO and founder of Rebiotix. “The positive preliminary data on the primary efficacy endpoint are a major stepping stone for the RBX2660 development program, bringing us closer to an approved microbiome therapy available for healthcare providers to help patients.”

PUNCH CD3 is a randomized, multicenter, double-blinded, placebo-controlled study. In addition to measuring efficacy, the study also incorporates a safety assessment intended to follow patients for several months after receiving the investigational drug. The safety data will provide insight into the potential of using microbes as a therapeutic intervention.

RBX2660 is the first treatment developed through Rebiotix’s Microbiota Restoration Therapy (MRT™) drug platform, which uses live microbiota as a therapy to replace or replenish disrupted microbial communities. A second formulation against C. diff. infection based on the platform is also in development, RBX7455, which according to Rebiotix is the first-of-its-kind non-frozen, room-temperature stable, oral microbiota-based product.

“Major step forward”

“These positive preliminary findings represent a major step forward towards bringing an innovative, non-antibiotic option to patients that may help restore their gut microbiome,” Per Falk, Ferring’s President and Chief Science Officer, said in a statement. “With health systems under increasing pressure due to viruses like COVID-19 and the rising threat of antimicrobial resistance, the need for new therapies is greater than ever. We believe the power of the microbiome has great potential and we look forward to bringing RBX2660 to patients soon.”

Among other developers of microbiome-based treatments, Seres Therapeutics on March 30 said it completed enrollment in its Phase III ECOSPOR III trial (NCT03183128), a multicenter, randomized, double-blind, placebo-controlled, parallel-group study designed to assess the safety, tolerability, and efficacy of SER-109 versus placebo in adults with recurrent C. diff. infection.

The trial was designed for 188 patients, but Seres halted enrollment at 181, citing the COVID-19 pandemic. Top-line results are expected in “mid-2020” as planned, the company added.

Another microbiome-based drug developer, Finch Therapeutics, is also studying its lead candidate CP101 in recurrent C. diff. CP101 is an oral Full-Spectrum Microbiota (FSM) product—an oral capsule containing lyophilized microbiota from healthy human donors—that is designed to prevent recurrent C. diff. infection by restoring the balance of the gut microbiome. Topline data for CP101 is set to be read out later this year from a Phase II potentially single pivotal trial, PRISM3 (NCT03110133)

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