It is just over a year since the publication of the first randomized controlled trial1 investigating the medical use of human faeces. The 43 trial participants had recurrent Clostridium difficile infections, which cause dangerous, painful and persistent diarrhoea. Those in the control groups received antibiotics alone. Those in the test group received antibiotics along with a fluid derived from filtered faeces, which was delivered into the upper small intestine through nasal tubes. This small trial was stopped ahead of schedule because the faecal slurry was more than twice as effective in resolving symptoms as antibiotics alone1. Non-randomized studies, with outcomes collected from hundreds of people suffering from recurrent C. difficile infections and treated with similar procedures, have had typical success rates of around 90% (ref. 2). First described3 in the scientific literature in 1958, faecal microbiota transplantation (FMT), delivers processed stool from a healthy individual to the gut of a sick person through enema, colonoscopy or other means. The goal is to displace pathogenic microbes from the intestine by re-establishing a healthy microbial community. Interest has surged in the past five years (see 'Stool treatment'). At the same time, new regulatory barriers have made FMT more difficult to study or practice.
In May 2013, the US Food and Drug Administration (FDA) issued a public announcement that it had been regulating human faeces as a drug. This classification requires physicians to submit a time-consuming Investigational New Drug (IND) application before performing FMT. The FDA reasoned that this requirement would make FMT safer by providing oversight, standardizing therapy and, eventually, encouraging development of commercial drug products. At a public meeting hosted that month by the FDA and the US National Institutes of Health (NIH), patients, physicians and representatives of the Centers for Disease Control and Prevention and several professional medical societies voiced concern about restricting access to care for these increasingly prevalent infections. Six weeks later, the FDA revised its position. The agency decided, for the time being, not to enforce the IND requirement for recurrent C. difficile infections. This compassionate exception is now enabling many people to receive much-needed care. But the long-term status of FMT for C. difficile infection is unresolved, and regulatory policy is complicating research into the exploration of FMT for other conditions, such as inflammatory bowel diseases or obesity.