A new guidance document from the UK’s medicines regulator, the MHRA, has laid out a clear path for companies to develop and approve a new type of medicine based on the body’s natural bacteria—called microbiome-based medicines. These medicines, which are not yet available in the UK, could help fight antibiotic-resistant infections like superbugs. The MHRA’s paper explains how companies can meet the same high safety and quality standards required for all UK medicines while developing these products. Key points for developers include: describing their product fully, ensuring consistent manufacturing, controlling differences between batches, assessing safety (including risks of spreading antibiotic resistance), and providing strong clinical evidence. Depending on their design, these treatments may be regulated as either biological medicines or advanced therapy medicines, similar to gene or cell therapies. The paper also updates rules for faecal microbiota transplants (FMT), a treatment already used in the UK for serious gut infections caused by *Clostridioides difficile*. Julian Beach, Executive Director of Healthcare Quality and Access at the MHRA, said: “Microbiome-based medicines are one of the most exciting and rapidly advancing areas in healthcare today. Our new guidance gives companies the confidence to develop these treatments while keeping patients safe under the same strict standards as all approved UK medicines. The UK’s licensing system is flexible and evidence-based, ready to support this field. The best way for companies to navigate these rules is to contact us early in the process, so we can help clarify requirements, agree on practical development plans, and reduce risks before major clinical trials.” The MHRA’s guidance comes as the European Union introduces new rules for treatments involving human-derived substances, including gut bacteria therapies, to ensure safety and consistency across Europe.