Bacteriophages have long been used to treat infections. These naturally occurring virus are capable of killing bacteria, but each strain of phage is highly specific. Because of their unique mechanism of action, they provide a potential to address the growing threat posed by multidrug-resistant bacteria, but to treat someone, the right phage must be matched to each patient’s infection. Adaptive Phage Therapeutics believes it’s found a way to create phage therapies suited to treat patients with drug-resistant infections by building a bank of targeted and genomically-screened bacteriophage and testing individual patient’s bacterial colony against that to determine the appropriate phage to treat them. We spoke to Greg Merril, co-founder and CEO of Adaptive Phage Therapeutics, about the origins of the company, how its technology works, and the regulatory hurdles for producing customized therapies to treat individual patients.