Seres Therapeutics has secured an orphan drug designation (ODD) from the U.S. Food and Drug Administration (FDA) for SER-287, its therapy to treat ulcerative colitis in children.

ODD offers companies incentives to develop therapies designed to treat diseases affecting fewer than 200,000 Americans.

SER-287 is a new kind of drug made up of bacterial spores, or dormant bacteria that act as seeds, only multiplying when conditions are right. The spores in SER-287 produce bacteria that help the intestines, where they multiply and replace bacteria that contribute to UC.

SER-287 won its ODD status on the basis of a recent placebo-controlled Phase 1b trial (NCT02618187) in children with mild to moderate UC who did not respond to current therapies. The test group received SER-287 orally on a once-weekly basis for eight weeks.

Seres, based in Cambridge, Massachusetts, reported that the drug was safe and well-tolerated in these patients. Seres also said treatment with SER-287 resulted in an improvement in remission rates and endoscopic scores.

The composition of different kinds of bacteria in the body, or in a specific area of the body, is known as its microbiome. The Phase 1b study, still recruiting patients, will also analyze changes in the kinds of bacteria that comprise patients’ microbiomes, with results expected in early 2018.

“We are pleased to receive FDA Orphan Drug Designation for SER-287 and we look forward to advancing the program into further development for ulcerative colitis,” Dr. Roger J. Pomerantz, president, CEO and chairman of Seres, said in a press release. “Safety is of particular importance to the pediatric population, and given the positive safety profile observed in our clinical trial to date, we believe our microbiome approach may be well suited to address this group.”

UC causes in inflammation of the colon and rectum and can have debilitating symptoms, including abdominal pain and diarrhea. In severe cases, the colon may have to be surgically removed.