FDA's new genome editing guidance: Why patient identification matters earlier in development

The FDA's draft guidance on individualized human genome editing products, issued on 27 October 2026, proposes a pathway that could allow a single biologics license application (BLA) to cover multiple patient-specific versions of a genome editing product.Central to the proposal is the Individualized Feature Space (IFS): the defined boundaries within which product features, such as the guide RNA spacer, may vary. Under the draft, additional product variants within an approved IFS could, in many cases, be introduced using new in vitro safety and activity data alongside existing clinical evidence, without requiring additional clinical studies for every variant.

For sponsors, this has implications beyond regulatory strategy. As the pathway for adding variants becomes more scalable, identifying and genetically confirming eligible patients may become increasingly important in determining how broadly individualized therapies can reach their intended populations.

On the same day, a joint HHS, FDA and CMS announcement stated that CMS plans to expand its Cell and Gene Therapy (CGT) Access Model beyond sickle cell disease. Although the reimbursement details remain to be established, both announcements point toward an environment increasingly focused on making individualized therapies more viable.

In our view, the FDA draft could reduce the regulatory burden of treating additional mutations within a licensed program, provided the variants fall within the approved IFS and sufficient supporting evidence is available. That makes the ability to identify, characterize, and maintain relationships with eligible patients an increasingly important consideration for development planning.

How the individualized pathway took shape

The draft builds on several FDA initiatives addressing the challenges of developing therapies for very small patient populations. The Federal Register notice connects it to the January 2024 genome editing guidance, the February 2026 Plausible Mechanism Framework draft, which addressed evidentiary standards for individualized therapies, and a June 2026 prior knowledge draft.

In November 2025, Makary and Prasad described the emerging pathway in the New England Journal of Medicine, citing Baby KJ, who received a bespoke CRISPR therapy for CPS1 deficiency. The case demonstrated the potential of individualized editing while highlighting the difficulty of developing separate evidence packages for extremely small patient populations.

According to the HHS announcement, the new guidance puts elements of FDA's Rare Disease Framework into practice. When that framework was announced, we explored how it could place patient identification at the center of rare disease development.

The IFS draft makes that connection more concrete by proposing a regulatory framework in which the genetic variants covered by a therapy are explicitly defined within its licensed scope.

As BioInnovation Beacon reported, the guidance arrived during the NORD Breakthrough Summit. Reimbursement is progressing separately through the CMS CGT Access Model, which began state participation in January 2025 and initially focused on sickle cell therapies. The HHS announcement states that a request for manufacturer applications will follow in the coming months.

Why variant-level eligibility changes patient identification

Several provisions in the draft guidance define the proposed pathway at the level of individual genetic variants or variant classes:

• Product labeling identifies the disease and covered gene variants or variant classes, including which were evaluated clinically.
• Sponsors must justify how clinically evaluated variants adequately span the proposed IFS.
• Extrapolation to additional variants depends partly on natural history knowledge, including genotype-phenotype associations.
• Variants causing a clinically distinct disease represent a new indication requiring supporting clinical evidence.
• The pathway is limited to monogenic diseases caused by known pathogenic variants that share a single intended editing outcome.

These requirements make patient identification relevant well before recruitment begins.

Demonstrating that clinically studied variants adequately represent an IFS may require sponsors to consider variant diversity alongside total enrollment targets. Extrapolation to additional variants depends partly on evidence connecting genetic findings with clinical characteristics, making access to well-characterized patient populations particularly valuable.

The distinction between genetic variants and clinical indications also matters. A variant in the same gene may cause a clinically different disease, meaning genetic confirmation alone may not establish whether a patient falls within the licensed indication.

Similarly, patients carrying variants of uncertain significance (VUS) may fall outside the proposed pathway unless sufficient evidence supports their classification as pathogenic. Accurate variant interpretation therefore becomes an important part of eligibility assessment.

For sponsors, these requirements create a direct connection between patient identification and development strategy. Understanding variant distribution, genotype-phenotype relationships and practical routes to genetic confirmation can inform feasibility assessments, clinical evaluation and the evidence needed to support the proposed IFS.

This need may extend beyond initial approval. As additional product variants are considered under a license supplement or approved postapproval change management protocol, sponsors may need to identify and reassess patients whose genetic and clinical characteristics meet the evolving eligibility criteria.

Patient identification is therefore not simply an enrollment activity. For individualized editing programs, it may become a continuing component of development and postapproval planning.

What this means for patient-finding programs

The proposed framework highlights the importance of connecting genetic testing, prescreening, patient characterization and long-term engagement.

Genetic testing needs to reflect the intended variant coverage. Sano's integrated genetic testing approach supports at-home sample collection or kits-at-site models, alongside precise genetic confirmation, genetic counseling and personalized reporting.

Test selection matters when an IFS covers multiple variants within a gene. The FDA draft, for example, describes an illustrative IFS containing four specified variants alongside other C>T or G>A variants in the same gene. A test targeting only one known mutation would not necessarily identify the full potentially relevant population. Sponsors may therefore need testing strategies designed around the expected breadth and types of variants.

Prescreening can provide earlier visibility into variant-level feasibility. In a gene therapy trial for a rare cause of congenital hearing loss, 510 individuals completed Sano's pre-screener. Of these, 85% met initial eligibility criteria and 20% were referred to genetic testing or the study. Caregivers could upload existing genetic reports to support diagnosis confirmation, and eligible participants were segmented into two cohorts.

In an IFS-based program, a similar approach could help sponsors understand which variants are represented among identified patients and where additional patient-finding efforts may be needed. This provides a more useful view of feasibility than total patient numbers alone.

Long-term engagement matters when eligibility evolves. Patients who are not eligible for a current treatment opportunity may become relevant as additional variants are incorporated or future studies become available.

Sano's Virtual Waiting Room is designed to maintain relationships with participants over time. In the program described in Sano's testing overview, 60% of participants remained engaged long term, with study emails achieving a 65% open rate compared with a cited industry benchmark of 21%.

For individualized editing programs, maintaining appropriately consented and recontactable patient populations could reduce the need to rebuild identification efforts whenever eligibility expands. Patients would still require updated assessment and confirmation before being considered for new treatment opportunities.

These activities may also contribute to the broader evidence strategy. Genotype and phenotype information gathered through appropriately designed patient identification programs can help sponsors understand variant distribution, clinical characteristics and gaps in natural history evidence. Such data would need to meet relevant quality and governance requirements before being used as regulatory evidence.

The draft guidance encourages sponsors to define the IFS prospectively during development. Decisions about which patients and variants can be identified and characterized early may therefore influence both clinical evaluation and the scope of the eventual licensed product.

Open questions for sponsors

Comments on the draft close on 27 November 2026 under Docket FDA-2026-D-11783, according to the Federal Register notice.

Clinical trial design is outside the scope of the current draft guidance, with FDA indicating that it intends to address the topic separately. How the agency approaches the number and selection of variants needed to support an IFS could have important implications for early recruitment and evidence planning.

Several questions remain:

• How will FDA weigh natural history evidence for variants found in very small numbers of patients?
• Under what circumstances could a VUS subsequently classified as pathogenic be incorporated within an existing IFS?
• How should sponsors manage patient identification and recontact as variant eligibility changes after approval?
• How will the forthcoming CMS CGT Access Model expansion address therapies whose eligible populations grow over time?

Our earlier analysis of BEAM-301 explored patient finding for a mutation-specific therapy. The IFS proposal extends this challenge across a potentially broader range of variants and into the postapproval period.

For sponsors, that makes variant-level feasibility, genetic confirmation and long-term engagement important considerations from the outset. The variants represented in clinical evaluation, the evidence available to support extrapolation and the patient populations that can be characterized may all influence how broadly an individualized therapy can ultimately be used.

Sano brings patient finding, genetic testing and long-term engagement together to help precision medicine teams identify and characterize relevant patient populations across development programs.

To discuss patient identification and genetic testing strategies for an individualized genome editing program, get in touch with Sano.