A comparability assessment is the structured, risk-based process used to determine whether a biotechnological/biological product made before and after a manufacturing change remains comparable—i.e., has highly similar quality attributes with no adverse impact on quality, safety, or efficacy. Analytical testing is the foundation; when uncertainty remains, nonclinical and/or clinical bridging may be needed. Principles are defined in ICH Q5E and implemented within a firm’s Quality Risk Management (ICH Q9) and Pharmaceutical Quality System (ICH Q10).
What triggers a comparability assessment?
Comparability is undertaken when a change could affect product quality, not automatically for “any” change. The scope is determined by risk assessment under Q9 and managed via the change-management system described in Q10. Typical triggers include (examples): manufacturing site/scale changes; process parameter or unit-operation modifications; changes to cell banks; raw materials; and container-closure systems. Regulators expect the extent of data to match the potential impact of the change.
The tiered approach (per ICH Q5E)
- Analytical testing (the foundation)
Use a sufficiently sensitive panel of appropriately validated (or phase-appropriate) methods to compare pre-change and post-change materials side-by-side. Multiple orthogonal methods may be used for the same attribute. If analytical data show the products are highly similar and science indicates no adverse impact, nonclinical/clinical studies are not warranted. - Nonclinical studies (as needed)
If analytical results reveal differences whose clinical impact is uncertain, targeted nonclinical studies (e.g., PK/PD or tox, as appropriate to modality) may be used to resolve residual uncertainty. - Clinical studies (as a last resort)
When meaningful uncertainty persists after analytical/nonclinical assessment, a clinical bridging study may be required to confirm that safety/efficacy are unchanged.
FDA’s 2023 draft guidance on manufacturing changes and comparability for CGT products applies the same principles but notes that, due to modality complexity, the level of evidence may be higher, and additional nonclinical/clinical bridging can be needed if analytical comparisons cannot fully resolve uncertainty. Early FDA interaction is encouraged.
The Comparability Protocol (FDA)
For post-approval changes, sponsors can submit a Comparability Protocol (CP)—a prospective, detailed plan that defines the change, the studies (analytical/nonclinical/clinical, as needed), predefined acceptance criteria, and the proposed reporting category. An approved CP can streamline implementation and regulatory reporting of future changes within its scope.
Practical design notes (from Q5E)
- Evaluate at the stage(s) most likely to reveal differences (e.g., DS and DP, if appropriate).
- Include stability data (real-time/accelerated or stress) as needed to understand degradation pathways post-change.
- Recognize that release specifications alone may be insufficient; deeper characterization can be required.
Regulatory Guidance
- ICH Q5E: Comparability of Biotechnological/Biological Products Subject to Changes in Their Manufacturing Process. (Core principles; “highly similar,” tiered approach; not necessarily identical.) ICH DatabaseEuropean Medicines Agency (EMA)U.S. Food and Drug Administration
- ICH Q9: Quality Risk Management. (Risk assessment to scope the exercise.) ICH DatabaseEuropean Medicines Agency (EMA)
- ICH Q10: Pharmaceutical Quality System. (Change management framework.) ICH DatabaseEuropean Medicines Agency (EMA)
- FDA – Comparability Protocols (final guidance and notice). (Prospective plan for post-approval CMC changes.) U.S. Food and Drug AdministrationFederal Register
- FDA – CGT manufacturing changes & comparability (Draft, 2023). (CGT-specific expectations; when additional bridging may be needed.)