With regards to licensed phage therapeutic products, MHRA non-binding advisory guidance for licensed products is in development and is scheduled to undergo public consultation in 2024. Due to the specific nature of bacteriophage products, any guidance on safety tests for phage-based VMPs should ensure studies are carried out with representative mono- or multi-phage preparations. Accordingly, it will also need to consider how extrapolation between comparable strains of bacteriophages may be possible. This may be based on representative in vitro or in vivo test parameters or scientific justifications. The VMD is already considering these specific requirements as part of its wider consideration of guidance for phage-based VMPs. Specific scenarios set out in paragraph 100 of the report, followed by responses The individual phage strains specific to the bacteria they seek to inhibit could be limitless and impossible to test in advance. Where new phage strains are needed, manufacture should occur in compliance with GMP standards, including unlicensed medicines. Unique formulations of phages in conjunction with other drugs, to target infection in individual patients with specific microbiota might not be anticipated in traditional clinical trials. Formulations of medicinal products must be assessed for safety. It is recommended that there is engagement with the MHRA Clinical Investigations and Trials team to ensure that the appropriate safety evidence is available for assessment. In the future, pre-tested generic phages that have met regulatory standards may not be able to inhibit bacterial growth necessitating adaptation which maybe beyond inflexible regulations. The GMP and Clinical Trials Regulations exist to ensure the safety of the patient. The regulations include frameworks and processes to ensure that when a medicinal product is changed there is assessment of the implications of the change for the efficacy and safety of the product. The planned guidance will provide information on the requirements for those seeking to adapt an existing medicinal product. The specificity required to target a particular infection in a single human could require gene editing of phages, with current regulations implying that each new formulation would require full clinical trials each time, which would not be timely cost effective efficient or possible in terms of generating clinical data if each use ins unique. Urgent, patient-specific compassionate use largely excludes gene editing due to time pressures (if there is no time pressure it can be made to GMP), while formulation is a pharmacy issue, and clinical trials are not relevant in this case. The use of double-blind clinical trials and control groups would be problematic if they related to a unique combination of phages produced for a single patient. Unique combinations for patients would fall under named-patient use, for which GMP requirements remain appropriate. The prescribing physician is responsible for the decision on the benefit risk balance of these medicines in an individual patient and they are not subject to the requirement for clinical trials or assessment by MHRA.