Live biotherapeutic products are an emerging class of biological medicines that rely on viable microorganisms to treat or prevent disease. Unlike probiotics marketed as foods or dietary supplements, live biotherapeutic products are regulated as drugs and are therefore subject to rigorous requirements for quality, safety, and clinical efficacy. Recent approvals of microbiota-based treatments for recurrent Clostridioides difficile (C difficile) infection, a bacterial illness that causes severe diarrhea, highlight their therapeutic potential and the regulatory challenges posed by using living organisms. This article examines regulatory expectations for live biotherapeutic products in the US and EU, with an emphasis on safety evaluation, clinical development strategies, and manufacturing controls.