The regulatory definition for advanced therapy medicinal products (ATMPs) has struggled to stay in step with modern science and current practice. In response to this, the Medicines and Healthcare products Regulatory Agency (MHRA) opened a consultation on 11 May 2026 to update the legal definition for gene therapy medicinal products (GTMPs).
This matters because a product will only be regulated as an ATMP if it falls within one of the relevant legal categories, including GTMPs, somatic cell therapy medicinal product (sCTMP), or tissue engineered product (TEP). GTMPs are a particularly important category, but the existing definition requires them to be biological in origin. That limitation no longer reflects the way many modern therapies are being developed, with products often now using gene editing and synthetic nucleic acid technologies.
The existing definition
The regulatory definition of a GTMP is found in the Human Medicines Regulations 2012 (reg 2A(2) and (3)), as follows:
"A 'gene therapy medicinal product' is a biological medicinal product which has the following characteristics:
- it contains an active substance which contains or consists of a recombinant nucleic acid used in or administered to human beings with a view to regulating, repairing, replacing adding or deleting a genetic sequence; and
- its therapeutic, prophylactic or diagnostic effect relates directly to the recombinant nucleic acid sequence it contains, or to the product of genetic expression of this sequence."
The current definition does not reflect modern developments in this fast moving area. Neither synthetic nucleic acid starting materials nor emerging forms of genome editing technologies are captured. This has real world implications for developers as it means regulation acts as an impediment to them taking a risk based approach to their programme of development.
The proposed change
As is apparent from the suggested definition included below, the MHRA is seeking to broaden the definition to capture medicinal products developed from non-biological starting materials. This would mean that all products which result in sequence genome edits and medicinal products created with synthetic nucleic acids would be classified as GTMPs, alongside the biological products caught by the existing definition. This proposed definition captures a product's 'impact' on the cell, rather than providing a prescriptive definition of how the products were made and from what materials.
It is proposed that a GTMP is a medicinal product that has any of the following characteristics, namely the product contains or consists of:
- a substance or a combination of substances that edit a target genome in a sequence specific manner; or
- cells which have been modified in that their genome has been edited in a sequence specific manner.
- a recombinant nucleic acid or synthetic nucleic acid, which is intended to regulate, replace or add any nucleic acid sequence; and mediates its effect by being transcribed or translated; or
- cells subjected to a recombinant nucleic acid or synthetic nucleic acid, which is intended to regulate, replace or add any nucleic acid sequence; and mediates its effect by being transcribed or translated;
A vaccine against infectious diseases is still not to be treated as a gene therapy medicinal product.
Anything else to be aware of?
Developers should be aware that this is not a backwards looking consultation. There are no changes to those products that are already licensed, nor are any of the wider standards around product approvals and the underlying regulatory principles for GTMPs shifting any time soon.
The consultation will be open until 22 June 2026 for the submission of responses, before it moves onto the next stage in the process and the MHRA consider the responses. The MHRA are particularly interested in the views of experts, given the technical nature of this area.
