Venture capitalists launched two new biotech companies that will tackle disorders that affect the gut.

Flagship Ventures, and other investors, launched Seres Health with $10.5 million in funding. The new company was incubated in Flagship’s Venture Labs for two years, studying the ecology of the human microbiome—the trillions of bacteria and microorganisms that populate the human body, especially the gastrointestinal tract. Seres’ will focus on therapeutics that can shift the microbiome to a state of health.

“The true underlying biology of the microbiome gives us a solid foundation from which we can develop safe and effective drugs using our proprietary Microbiome Therapeutics platform,” says David Berry, CEO and co-founder of Seres, and partner at Flagship Ventures.

Seres is developing candidates to treat infectious, metabolic, and inflammatory diseases. Its lead experimental candidate is currently being tested in the clinic to treat C. difficile infection, a major cause of antibiotic associated diarrhea that leads to more than 14,000 deaths a year in the United States.

Seres joins a growing list of companies that are exploring microbiome modulation therapies, including Second Genome, AvidBiotics, and Vedanta, among others.

Sitari Pharmaceuticals is the first company launched by the recently established Avalon Ventures and GlaxoSmithKline collaboration to fund and launch up to 10 life sciences companies in San Diego. Under their agreement, signed in April 2013, Avalon said it would commit about $30 million to the joint venture, while GSK said it would commit about $465 million. GSK has the option to buy the companies launched by their joint venture after they have done the initial discovery and preclinical work.

Funded with $10 million in series A financing plus research and development support, Sitari will develop new treatments for celiac disease. Sitari’s technology is based on intellectual property in-licensed from the laboratory of Stanford professor Chaitan Khosla, who is the scientific founder of Sitari. The company is targeting inhibitors of the transglutaminase 2 pathway to develop novel treatments for multiple disease indications, starting with celiac disease, an autoimmune digestive disease caused by intolerance to gluten.