FDA Draft Guidance on Potency Assays for Cellular and Gene Therapy Products

On 28 December 2023, the FDA published a draft guidance document "Potency Assurance for Cellular and Gene Therapy Products". This can now be commented on until 27 March 2024.
In the recent past, it has been shown several times that ensuring the efficacy of cell and gene therapeutics over the entire product cycle, i.e. from development through clinical phases to final production, can certainly be a challenge, e.g. in the context of upscaling. Bio assays/potency assays in particular are often highly complex. This may explain why the authorities are also trying to create helpful guidelines for this area.


This draft guidance contains recommendations for the development of a science- and risk-based strategy to ensure the effectiveness of a human cell therapy or gene therapy product (CGT). The term strategy in this case refers to an approach to ensure efficacy that reduces risk at multiple levels through manufacturing process design, manufacturing process control, material control, in-process testing and efficacy batch release testing. It aims to ensure that each batch of a released product has the specific ability or capacity to achieve the intended therapeutic effect. This draft is intended to replace the previous "Guidance for Industry: Potency Tests for Cellular and Gene Therapy Products" from January 2011 once it has been commented on and finalised.

The final guidance is intended to describe a QRM (quality risk management) based approach to ensure the efficacy of cell/gene therapy and to reflect the FDA's recommendations for potency testing for CGT products. As potency assays are an important component of efficacy testing, these recommendations are of key importance, but the guidance is also intended to provide complementary approaches to ensure efficacy.


The scope of this guidance is limited to ensuring the effectiveness of CGT products regulated as biological products under Section 351 of the Public Health Service Act (PHS Act) (42 U.S.C. 262). This guidance provides recommendations for ensuring the effectiveness of CGT products at all stages of their product life cycle. For investigational products, it explains how to implement a step-by-step strategy to ensure efficacy during product development. It also provides specific considerations for ensuring the efficacy of products undergoing rapid clinical development.

Contents of the guideline

I. Introduction
II. Background
III Regulatory framework
IV. Development of a strategy to ensure effectiveness
V. Potency a and acceptance criteria

For authorised products, the requirements for ensuring potency, including the tests required for batch release, are described. Developing tests to measure the potency of CGT products can be challenging. This guidance emphasises that efficacy testing and the corresponding acceptance criteria should be designed to make a meaningful contribution to ensuring efficacy by reducing risks to product efficacy. Illustrative examples of approaches to developing efficacy testing based on quality risk management are presented.

Due to the diversity of CGT products and the product-specific nature of efficacy testing, the recommendations in this guidance regarding the selection and design of efficacy testing are necessarily general. FDA reserves the right to issue additional guidance documents that provide additional efficacy testing advice for specific classes of CGT products.

More detailed information can be found directly in the draft guidance "Potency Assurance for Cellular and Gene Therapy Products".

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