What happened

Shares of Seres Therapeutics (NASDAQ:MCRB) soared on Monday after the biotech company announced promising results from a phase 3 study of its experimental therapy for colon infections. As of 3:35 p.m. EDT, Seres' stock was up 350% after rising as much as 611% earlier in the day. 

So what 

Seres said the administration of its oral microbiome therapeutic, labeled SER-109, resulted in a 30.2% decline in the number of patients who experienced a recurrence of C. difficile infection (CDI) within an eight-week period, compared to a placebo. The drug was also well tolerated, with no serious adverse events reported during the study.

A person is pointing to an upwardly sloping line.

Seres Therapeutics' stock rocketed higher on Monday. Image source: Getty Images.

Seres also said the results of the study support its request for a breakthrough therapy designation from the U.S. Food and Drug Administration. "We are extremely pleased with these highly clinically meaningful SER-109 phase 3 study results, greatly exceeding the statistical threshold provided by the FDA," CEO Eric Shaff said in a press release. "Based on our prior discussions with the FDA, we believe this trial should provide the efficacy basis for submitting an application for product approval."

Now what 

The market opportunity for Seres' experimental treatment could be sizable. Roughly 170,000 people in the U.S. alone suffer from recurrent CDI each year, according to Seres' chief medical officer Lisa von Moltke.

Better still, the drug could have an enormous impact on the lives of the people who struggle with the illness. "Recurrent C. difficile infection is a serious disease that devastates patients' quality of life, and in many severe cases may result in a patient's death," University of Leeds Professor of Medical Microbiology Mark Wilcox said in Seres' release. "Today's treatment options have important shortcomings related to efficacy, safety, and route of administration, and novel approaches that target the root causes of the disease are urgently needed."