The US Food and Drug Administration (FDA) has granted orphan drug designation to microbiome therapeutics platform company Seres Therapeutics Inc's SER-109, an oral therapeutic currently in a phase 2 clinical trial for the prevention of recurrent Clostridium difficile infection (CDI) in adults.

SER-109, the lead Ecobiotic microbiome therapeutic, is being investigated as a new therapeutic modality to treat recurrent CDI by correcting a dysbiosis of the human microbiome, which is an underlying cause of the condition. SER-109 was developed utilising the Seres microbiome therapeutics platform that provides deep insight into the ecologies of disease and then identifies microbial compositions that can catalyse a shift to a healthier state.

CDI is one of the US Centers for Disease Control’s top three most urgent antibiotic-resistant bacterial threats. It is the leading cause of hospital-acquired infection in the US, and is responsible for the deaths of approximately 29,000 Americans each year. Recurrent CDI affects between 85,000 and 110,000 people in the US annually.

"Receiving orphan drug designation from the FDA for SER-109 is another step on our path to bringing this important new medicine to patients in dire need of an effective, durable treatment. Moreover, it signifies a landmark event, as it marks the first microbiome drug to achieve this regulatory milestone, and is also rarely given for infectious disease indications," said Roger Pomerantz, M.D., chairman, president and chief executive officer of Seres.

"SER-109 is intended to re-introduce essential bacteria that restore the body's natural resistance to CDI by re-establishing the ecology of the colonic microbiome. Because we're focused on treating the underlying cause of the disease, we believe we have the potential to break the cycle of recurrent CDI and have a significant impact for patients. We're extremely pleased that we continue to make both clinical and regulatory progress, well positioning us to advance this radically new approach to address such a difficult and devastating infectious disease."

Antibiotics are currently the only FDA-approved treatment option for recurrent CDI. Exposure to antibiotics is the greatest risk factor for acquiring CDI and their use to treat CDI may induce or prolong an imbalance of the microbiome, which is comprised of trillions of bacteria and other organisms that inhabit or live on our bodies. When in balance, these organisms play critical, beneficial roles in a wide range of biological processes, including resistance to infection by pathogens such as the Clostridium difficile bacterium, education and regulation of the immune system, and regulation of energy metabolism. In a dysbiotic state, the microbiome cannot carry out some of these roles, which leads to the onset and progression of various diseases and conditions. In a single dose of four capsules, SER-109 re-introduces an ecology of purified bacterial spores which restore the microbome to a healthy state, able to once again carry out key biological functions, including resistance to Clostridium difficile.

Results from a phase 1b/2 study of SER-109 in recurrent CDI patients showed that 87 per cent of patients achieved efficacy endpoint per protocol, and 97 per cent of patients achieved a clinical cure, which was defined as the absence of CDI requiring antibiotic treatment during the eight-week period after SER-109 dosing.

Seres is currently conducting a multicenter, randomized, placebo-controlled phase 2 clinical study to assess the efficacy and safety of SER-109 in preventing recurrent CDI. The primary outcome measure is the absence of CDI through eight weeks following administration of SER-109 compared to placebo. The company expects the results from this study to be available in the middle of 2016.

The FDA Orphan Drug Designation programme provides a special status to drugs and biologics intended to treat, diagnose or prevent rare diseases and conditions that affect fewer than 200,000 people in the US, or that affect more than 200,000 people but are not expected to recover the costs of developing and marketing the product in the U.S. The designation provides Seres with certain benefits, including a seven-year marketing exclusivity period for this indication upon approval of SER-109, tax credits for clinical research expenses incurred in the US, and an exemption from FDA application user fees.

In addition to Orphan Designation, in June 2015, SER-109 was granted Breakthrough Therapy designation by the FDA, which is intended to expedite the development and review of therapeutics for serious conditions that may demonstrate a substantial improvement over existing therapies, based on preliminary clinical evidence.