Guidance on Sequencing Standards for Genome Editing Therapies
FDA has released a draft guidance outlining how drug developers should evaluate the safety of human gene therapies that use genome editing, with a particular focus on next-generation sequencing (NGS) methods to detect unintended genetic changes.
The document, titled “Safety Assessment of Genome Editing in Human Gene Therapy Products Using Next-Generation Sequencing,” provides recommendations for designing nonclinical studies that support INDs and BLAs. It builds on the agency’s 1/2024 guidance on genome editing therapies and reflects growing regulatory attention to risks such as off-target genetic alterations, FDA says.
FDA notes that genome editing technologies — including systems like CRISPR-Cas system, zinc finger nucleases, and TALENs — rapidly expanded in recent years, enabling precise modification of DNA, RNA, and even epigenetic markers. However, it emphasizes that unintended edits at off-target sites and chromosomal disruptions remain key safety concerns.
The draft guidance highlights the need for robust assessment of these risks, noting that unintended edits could impair normal cell function or introduce harmful mutations. Sponsors are encouraged to use both computational tools and sequencing-based approaches to identify and quantify such events.
A central component of the guidance is the use of NGS technologies to evaluate both intended (on-target) and unintended (off-target) edits. FDA recommends that developers tailor sequencing strategies based on the type and scale of genetic changes:
- Short-read sequencing may be sufficient for detecting small edits, such as single base pair changes or short insertions and deletions.
- Long-read sequencing is advised for identifying larger structural changes, including sizable insertions, deletions, or chromosomal rearrangements.
The agency also stresses the importance of sequencing depth and sensitivity, particularly for detecting low-frequency off-target events that may occur less often than intended edits. Sponsors should justify their methodologies with internal data or published evidence and take steps to minimize technical biases, such as those introduced during PCR amplification.
Beyond laboratory methods, the guidance places significant emphasis on transparency and reproducibility in data analysis. Sponsors are expected to provide detailed documentation of:
- Sample preparation and sequencing workflows
- Bioinformatics pipelines and software tools
- Reference genomes and databases used
- Quality control criteria and acceptance thresholds
- Tabulated results, including metadata, in standardized formats
This level of detail is intended to ensure that regulators can adequately assess the reliability of sequencing data and the robustness of safety conclusions.