FDA Issues Draft Guidance on Potency Assessment for Active Immunotherapy Products
核心洞察
The FDA's CBER issued draft guidance in August 2026 outlining potency assessment recommendations for active immunotherapy products (ACTIMPs), including personalized cancer vaccines and autoimmune disease (搜索) treatments.
The guidance supplements CBER's December 2023 potency assurance framework for cellular and gene therapy products while covering peptide- and protein-based ACTIMPs outside those categories.
FDA proposes a phase-appropriate approach allowing physicochemical lot-release testing in place of patient-specific functional bioassays when scientifically justified, potentially easing manufacturing scalability for personalized neoantigen vaccines.
The US Food and Drug Administration's (FDA) Center for Biologics Evaluation and Research (CBER) has issued draft guidance setting out its recommendations for assessing the potency of active immunotherapy products (ACTIMPs), a category that includes personalized neoantigen cancer vaccines, vectored immunotherapies, and cell-based antigen-presenting platforms. The guidance, issued in August 2026, describes the agency's current thinking regarding the design, validation, and evaluation of potency tests for these products.
The document supplements CBER's broader guidance for industry on "Potency Assurance for Cellular and Gene Therapy Products," released in December 2023, while also addressing ACTIMPs—such as peptide- and protein-based products—that do not fall within the cell or gene therapy categories.
Scope and Definition of ACTIMPs
FDA defines ACTIMPs as biological products regulated under Section 351 of the Public Health Service Act that treat pre-existing disease by inducing, stimulating, or modulating antigen-specific immune responses. According to the agency, active immunotherapies are designed to treat existing diseases or conditions by inducing, stimulating, or modulating immune effector cells through the introduction of an antigen associated with the specific disease or condition into the immune system.
Preventive vaccines for infectious diseases, bacteriophage products for infectious diseases, live biotherapeutic products, fecal microbiota for transplantation (FMT) products, and allergenic products are outside the scope of the guidance.
The guidance notes that "recent advances in genomics and new knowledge regarding mutation load in tumor cells have led to rapid improvements in ACTIMPs intended to treat cancer through induction of anti-cancer immune responses. ACTIMPs also include products intended to treat autoimmune disease (搜索) by inducing immune tolerance against specific antigens associated with that autoimmune disease."
Potency Assessment Framework
FDA emphasizes that assessing an ACTIMP's potency is challenging due to its reliance on host immune responses. To evaluate potency, sponsors should understand the active ingredients and mechanism of action (MOA) of the ACTIMP to identify critical quality attributes (CQAs) related to potency. Sponsors should also ensure that potency assays are quantitative and able to reliably discriminate between a product that is actively achieving its intended therapeutic effect and a product that has insufficient activity.
Recommendations are organized across five product categories: non-personalized peptide/protein products, non-personalized vectored products, personalized peptide/protein products, personalized vectored products, and cell-based ACTIMPs. The guidance addresses selection of bioassays and physicochemical assays, CQA identification, reagent qualification, adjuvant control strategies, lot release, stability testing, and manufacturing comparability.
The agency states that the most effective way to assess ACTIMP potency is through a quantitative bioassay, which evaluates the product's impact on the immune system using living cells, tissues, or animals. "Bioassays can help mitigate risks to a product's potency that may not be fully addressed through physicochemical assays alone," the guidance states. If the potency of an ACTIMP can be adequately assured without a bioassay, sponsors can use physicochemical assays during release testing.
Personalized Products and Scalability
Personalized products receive particular attention because each patient's antigen composition may differ, making conventional product-specific biological potency testing difficult to implement at scale. For products using bioinformatics pipelines to identify patient-specific epitopes, FDA describes a phase-appropriate approach in which early clinical development may rely on sequence confirmation supported by scientific justification of the antigen-selection process.
As development advances and the bioinformatics and manufacturing processes become appropriately qualified, FDA indicates that potency may in some circumstances be assured using physicochemical testing of relevant CQAs rather than a functional bioassay for every individualized lot. The agency states that physicochemical assays alone may be appropriate when sponsors can demonstrate that they adequately assure product potency.
This framework addresses a potentially important manufacturing constraint for personalized cancer vaccines. Because each patient's product may encode a different set of tumor neoantigens, requiring a bespoke functional potency assay for every manufactured batch could make large-scale commercial production difficult and slow. FDA's proposed approach provides a potential regulatory route around that problem: developers can establish and qualify the systems used to select and manufacture individualized antigens, define the CQAs linked to biological activity, and potentially transition toward scalable physicochemical lot-release testing when scientifically justified.
Regulatory and Clinical Context
FDA cautions that inadequate potency information can create regulatory risk, including the possibility of a clinical hold where the available information is insufficient to assess whether administration presents an unreasonable and significant risk to study participants. Sponsors should discuss their potency assurance strategy and potency assay development plans with the CBER review team assigned to their Investigational New Drug (IND) application.
The guidance also advises sponsors against adding an adjuvant to licensed products unless there is "satisfactory evidence" that it does not impact the product's safety or potency. If an adjuvant is utilized, CBER recommends that sponsors consult with their CBER review team for guidance on the appropriate control strategy for the adjuvant.
The guidance arrives as personalized cancer vaccines move closer to potential commercialization. In August 2026, Merck (搜索) and Moderna reported positive Phase III results for intismeran autogene, an individualized mRNA therapy encoding patient-specific tumor neoantigens, in combination with Keytruda (pembrolizumab) for resected high-risk melanoma (搜索). The 1,137-patient INTerpath-001 study met its primary recurrence-free survival endpoint and key secondary distant metastasis-free survival endpoint, providing late-stage validation of a therapeutic approach that depends on selecting and manufacturing a different antigen payload for each patient.
That progress raises the importance of scalable potency testing. Requiring a bespoke functional potency assay for every individualized vaccine batch could create a significant manufacturing bottleneck as patient volumes increase. FDA's proposed framework provides a potential route toward qualifying the underlying antigen-selection and manufacturing processes and, where scientifically justified, relying on physicochemical testing of potency-related CQAs for lot release rather than patient-specific functional bioassays.
Open Questions and Next Steps
Several issues remain to be resolved through the consultation process. FDA acknowledges that detailed criteria for qualification of bioinformatics pipelines are outside the guidance's scope, leaving open how sponsors will demonstrate that patient-specific antigen-selection systems are sufficiently controlled and reproducible. Industry feedback is also likely to focus on the evidence required before FDA accepts physicochemical assays without a functional bioassay, a determination that could materially affect the manufacturing scalability and turnaround times of individualized immunotherapies.
The document cross-references CBER's December 2023 draft guidance on Potency Assurance for Cellular and Gene Therapy Products, and finalization of that guidance could further clarify expectations for vectored and cell-based ACTIMPs. The current document represents FDA's draft recommendations and is nonbinding; comments submitted during the consultation process could result in changes before the agency issues final guidance.
The deadline for submitting comments is 18 November. Comments should be sent to www.regulations.gov and reference Docket No. FDA-2026-D-8561.