Seres Therapeutics stock rockets nearly fourfold after positive Phase 3 data on treatment for colon infections

Shares of Seres Therapeutics Inc. rocketed nearly fourfold (up 270%) on heavy volume in premarket trading Monday, after the microbiome therapeutics company reported upbeat results of a Phase 3 trial of its SER-109 for recurrent C. difficile infections (CDI), or an infection of the colon. Trading volume ballooned to 7.1 million shares, compared with the full-day average of about 876,000 shares. Seres said the study showed that SER-109 resulted in a "highly statistically significant absolute decrease" in the proportion of patients who experienced a recurrence in CDI within 8 weeks of administration versus placebo. ""We are extremely pleased with these highly clinically meaningful SER-109 Phase 3 study results, greatly exceeding the statistical threshold provided by the [Food and Drug Administration]," said Chief Executive Eric Shaff. "Based on our prior discussions with the FDA, we believe this trial should provide the efficacy basis for submitting an application for product approval." The stock has rallied 34.5% year to date through Friday, while the iShares Nasdaq Biotechnology ETF has advanced 13.0% and the S&P 500 has gained 3.7%.

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