Why did Seres Therapeutics (NASDAQ:MCRB) initiate the clinical evaluation for SER-155?

Seres Therapeutics (NASDAQ:MCRB) collaborated on the study to determine if a live biotherapeutic could treat severe gastrointestinal complications caused by popular cancer treatments. The clinical program seeks to establish an alternative option for patients suffering from immune checkpoint inhibitor-related enterocolitis.

What specific clinical response metrics did the trial achieve by day 15?

The early clinical dataset revealed that 80% of the treated patients achieved a formal immunosuppressive-free clinical response within the first two weeks. Furthermore, 33% of the participants within the 15-patient cohort reached a state of complete clinical remission.

How did the microbiome candidate impact biological biomarkers and gut health?

The biological compound successfully modified the intestinal flora of patients by achieving durable bacterial strain engraftment across the gastrointestinal tract. These structural microbiome alterations correlated with positive local biological marker changes that support moving the asset into advanced development.

What safety and tolerability outcomes were recorded during the investigator-sponsored trial?

The investigational oral consortium demonstrated a favorable overall safety profile and was generally well tolerated by the immunocompromised patient population. Researchers recorded zero unexpected severe toxicities or treatment-related infections stemming from the live bacterial strains.

Which medical research center spearheaded the design and execution of this clinical study?

The open-label, early-stage evaluation was conducted as an investigator-sponsored clinical trial directly at the Memorial Sloan Kettering Cancer Center. The specialized oncology institution coordinated the clinical patient tracking, stool sample sequencing, and baseline metabolic analyses.

Image for illustrative purposes only. Not a real photo.

Seres Therapeutics reports positive early enterocolitis data

Written by Mahathir BayenaPublished Jul 8, 2026, 12:48 PM

Seres Therapeutics announced positive preliminary clinical data evaluating its microbiome candidate SER-155.
The investigator-sponsored trial recorded an 80% immunosuppressive-free clinical response rate at day 15.
The early-stage data demonstrated successful bacterial microbiome engraftment alongside favorable tolerability profiles.

Seres Therapeutics (NASDAQ:MCRB) reported positive early clinical data from a 15-patient investigator-sponsored study evaluating its microbiome candidate SER-155 in patients with immune checkpoint inhibitor-related enterocolitis.

The early-stage trial achieved an 80% immunosuppressive-free clinical response rate at day 15, with 33% of the treated cohort reaching complete clinical remission.

"The early clinical data from this study support the potential of SER-155 to modulate the gut microbiome and reduce severe complications associated with cancer immunotherapies," the company stated in its clinical directory.

The bacterial consortium candidate demonstrated a highly favorable tolerability baseline while triggering crucial microbiome engraftment changes and targeted biological biomarker reductions across the participant population.

Following the announcement, Seres Therapeutics's share price was up at $8.45.

The clinical-stage biotechnology developer engineered the live biotherapeutic candidate to safely prevent bacterial translocation and manage aggressive gastrointestinal immune diseases.

The collaborative human trial framework was designed and executed independently by specialized oncology researchers at the Memorial Sloan Kettering Cancer Center.

Seres Therapeutics reports positive early enterocolitis data

Frequently asked questions

Assets related to this article