Mark Smith, a microbiologist at M.I.T., was halfway through his pitch with a group of pharmaceutical executives when one of them interrupted to ask if the meeting was a prank. “I can’t believe you wasted my time with this crazy idea,” the man said, Dr. Smith later recalled. That was 2012. Later that year he helped found OpenBiome, the nonprofit stool bank that now supplies most of the fecal matter for transplants in the United States. Three years ago, he started his own drug company, Finch Therapeutics, which has raised $77 million. Over the past decade, tens of thousands of Americans with C. diff have been cured through fecal transplants, often with a single dose that can bring patients back from the brink of death. The treatment has more than an 80 percent success rate, according to several studies, and many patients feel better within hours of receiving the procedure, which is usually administered through colonoscopy or capsules containing desiccated fecal matter. The F.D.A. has not formally approved the therapy but it has suspended enforcement of its rules for patients who have failed on antibiotics while it figures out the best way to regulate a regimen that, until recently, was sometimes performed at home by desperate patients using an enema, saline and a relative’s stool. Ms. Duff, the head of the C. diff patients group, credits her own recovery from the disease to a homemade concoction her husband created with his own stool in the kitchen blender. - www.nytimes.com