Policy paper

UK Position Paper on Microbiome-Based Medicinal Products (MBMPs)

Published 18 August 2026

Executive summary

Microbiome-based medicinal products (MBMPs) represent an emerging class of therapeutics with the potential to address areas of significant unmet clinical need. The purpose of this position paper is to encourage the development and licensing of these products in the UK.

The Human Medicines Regulations 2012 (SI 2012/1916) regulate medicinal products (for human use).  The Regulations include a definition of a medicinal product, and if a product is captured within that definition, strict regulatory requirements apply to the product and its manufacture, distribution, supply and advertisement.

The UK Medicines and Healthcare products Regulatory Agency (MHRA) considers MBMPs to be within scope of the existing UK medicines regulatory framework. At present, there are no microbiome-based medicinal products with marketing authorisation approvals in the UK. Nevertheless, microbiome interventions are already used in clinical practice and research through alternative regulatory routes, most notably faecal microbiota transplantation (FMT), which is available under clinical trial authorisations and as an unlicensed medicine manufactured under MHRA oversight via “specials” manufacturing arrangements.

Scope and definitions

A medicinal product is defined in section 2 of the Human Medicines Regulations 2012 as either any substance or combination of substances presented as having properties of preventing or treating disease in human beings; or any substance or combination of substances that may be used by or administered to human beings with a view to either restoring, correcting or modifying a physiological function by exerting a pharmacological, immunological or metabolic action, or making a medical diagnosis.

A MBMP is a medicinal product intended for the prevention, treatment, or diagnosis of disease in humans, whose principal therapeutic effect is mediated through the modulation, restoration, replacement, or functional activity of the human microbiome, and which contains as active substance(s) live microorganisms, a defined consortium of microorganisms, a complex microbial ecosystem, or non-viable microorganisms or their derived components. These products have typically been administered by oral, rectal or vaginal routes, but other routes may also be considered. Products regulated as foods, food supplements, cosmetics, or non-therapeutic probiotics fall outside the scope of this paper.

Live biotherapeutic products are referenced within the British Pharmacopoeia and are defined broadly as medicinal products containing live micro-organisms (bacteria or yeasts) for human use; these are administered orally, rectally or vaginally. Some of these products may therefore be considered MBMPs. MHRA encourages applicants to submit marketing authorisation applications for MBMPs.  These may be regulated as biological medicinal products under the Human Medicines Regulations 2012 as MBMPs are derived from a biological (living) source, and in some cases as advanced therapy medicinal products (ATMPs) where the legal criteria are met.

Current UK regulatory landscape

Absence of authorised MBMPs

As of July 2026, no MBMP has been granted a UK marketing authorisation. This contrasts with the US, where two donor-derived microbiota products have been licensed. In principle, MBMPs may achieve marketing authorisation in the UK using the existing UK medicines regulatory framework, if developers can demonstrate appropriate standards of quality, safety and efficacy (Apply for a licence to market a medicine in the UK).

Availability of FMT in the UK

Despite the absence of authorised MBMPs, FMT is available in the UK for specific indications, most notably recurrent Clostridioides difficile infection. FMT may be supplied:

• within clinical trials where investigational medicinal product (IMP) has been manufactured under a manufacturing authorisation for IMPs;
• as an unlicensed medicine operating under MHRA manufacturer’s specials licences;
• extemporaneously prepared in a pharmacy under section 10 of the 1968 Medicines Act.

The use of unlicensed medicines has enabled patient access and is designed to meet the needs of individual patients where no authorised medicines are available. However, the quality, safety and efficacy of unlicensed medicines have not been assessed by the MHRA and are under the direct responsibility of the prescribing doctor. 

Potential scientific and regulatory challenges

Product development, manufacture and controls

A central challenge for MBMP development is inherent variability which complicates characterisation. Thorough characterisation of the MBMP is essential as these may vary from fixed product compositions to tailored microbial consortia. The composition may vary during the product lifecycle and characterisation will need to be updated. The characterisation studies are intended to identify Critical Quality Attributes (CQA): i.e. molecular and biological characteristics found to be necessary in ensuring the consistency and the safety and efficacy of the product. Many microbiome products exhibit intrinsic biological variability, whether due to multi-strain composition, donor dependence, or dynamic behaviour during manufacture and storage. Developers must establish robust strategies for strain identification, potency assessment, control of batch-to-batch variability, and stability over the established shelf life. Current analytical tools, while advancing rapidly, may not be standardised or fully validated but they should be demonstrated to be suitable for their intended use. Developers must provide robust scientific justifications to address Chemistry, Manufacturing and Controls (CMC) expectations.

Developers should consider requirements as described in ICH quality guidelines including for the development and manufacture of drug substances as described in ICH Q11 (Q11 Guideline.pdf).  As a minimum this includes identifying potential CQAs associated with the drug substance so that those characteristics having an impact on drug product quality can be studied and controlled, defining an appropriate manufacturing process, and defining a control strategy to ensure process performance and drug substance quality.

Safety and antimicrobial resistance (AMR)

Safety assessment of MBMPs requires particular attention to:

• potential contamination with pathological microorganisms or toxins;
• risk of infection in vulnerable populations; and
• horizontal gene transfer, especially the potential transfer of antimicrobial resistance (AMR) genes.

MHRA accepts the need for risk-based, product-specific safety strategies rather than reliance on conventional toxicology studies, which may be poorly predictive for microbiome-modulating products.

Limitations of non-clinical models

Studies in animals may have limited relevance for predicting human effects due to species-specific microbiome differences. MHRA supports scientifically justified alternative approaches, including New Approach Methodologies (NAMs) and weight-of-evidence strategies, provided that uncertainties are transparently addressed (MHRA approach to medicines using non-animal methods).

Nevertheless, there still needs to be evidence presented that supports the claim that use of a specific product, as intended, is likely to bring medical benefit to an identifiable group of patients and that its use, as intended, is reasonably expected to be safe.

Drug-microbiota interactions

Evidence suggests the microbiome may be an important contributor to individual variability in drug responses and to adverse drug reactions.  For example, gut microbiota may modulate cancer treatment responses to immune checkpoint inhibitors and chemotherapies. Similarly, differences in gut bacteria may alter responses to many commonly administered medications for cardiovascular disease, diabetes, Parkinson’s disease, and other common diseases. Applicants should consider concomitant medication use during clinical development and the impact of MBMPs on pre-existing and new medical conditions.

Interaction with the EU SoHO Regulation and the Windsor Framework

The EU Regulation on Substances of Human Origin (SoHO), which explicitly includes intestinal microbiota, introduces a distinct regulatory framework for certain microbiome-derived interventions within the EU from 2027 (Regulation (EU) 2024/1938). UK Government consultation regarding SoHO regulation is currently in progress and future guidance is anticipated. Under current legislation and the Windsor Framework, the SoHO regulation will apply in Northern Ireland, but not in Great Britain. Once the review has concluded, a decision will be made about potential changes to legislation.

Application of existing legislative and regulatory frameworks

At present, no overarching UK-specific guidance for MBMPs exists. Developers must therefore consider:

• established UK legislation and regulatory guidance for biological medicinal products (and ATMPs if relevant);
• relevant ICH quality, safety and efficacy principles;
• Guide to the quality and safety of tissues and cells for human application -European Directorate for the Quality of Medicines and Healthcare guidance on intestinal microbiota (Chapter 32); and
• product-specific scientific advice from the MHRA.

International guidance for biological medicinal products may be helpful for planning development of MBMPs but MHRA advises developers to seek formal scientific advice on the acceptability of their development plan for future UK marketing authorisation approval. The MHRA considers that there is sufficient flexibility in existing frameworks for proportionate, science-led approaches rather than prescriptive regulation to the development and future approval of MBMPs.

Importance of early engagement with MHRA

Given the scientific novelty, regulatory complexity, and potential international divergence in expectations, early engagement with the MHRA is recommended. Innovation surgeries (MHRA Innovation Office) and scientific advice meetings (Medicines: get scientific advice from the MHRA ) allow developers to:

• clarify applicable regulatory frameworks (e.g. biological vs ATMP);
• agree proportionate non-clinical and clinical development strategies;
• align on CMC expectations, including acceptable levels of variability; and
• de-risk development plans ahead of pivotal investment decisions.

Experience to date indicates that such engagement provides clarity and assurance, enabling accelerated development of novel therapies within the UK.

Overall position

The UK takes a science-led, enabling approach to MBMPs. The MHRA wishes to encourage the development and use of products which have been licensed with appropriate evidence.  The supply of unlicensed products in the UK remains important for patient treatment until we have licensed treatments available.

The MHRA considers MBMPs acceptable in principle and capable of meeting UK regulatory standards for marketing authorisation. Progress toward licensure will depend on resolving challenges which may include product characterisation, CMC standardisation, safety (including antimicrobial resistance), and clinical evidence generation. Early engagement with MHRA remains the regulatory cornerstone for successful MBMP development in the UK.