Biosimilars: Regulatory Concepts, Development and Pharmacovigilance

Purpose and Scope

A biosimilar is a biological medicinal product developed to be highly similar to an already authorised biological medicinal product, known as the reference medicinal product. The EU biosimilar framework was developed because biological medicines cannot generally be reproduced by the same straightforward chemical synthesis and bioequivalence approach used for conventional generic medicines. Instead, biosimilarity is established through a structured comparability exercise that progressively evaluates the relevant characteristics of the proposed product against the reference product.

This distinction has direct implications for pharmacovigilance. A biosimilar is a biological medicinal product and therefore remains subject to the general EU pharmacovigilance framework. At the same time, its scientific and regulatory history creates a particular evidence context: the reference product provides an established body of biological, clinical and safety knowledge, while the biosimilar must retain its own product identity and remain distinguishable in clinical use. EMA states that the safety of biosimilars is monitored through pharmacovigilance activities after authorisation in the same general way as other medicines, while the biological-product GVP guidance places particular emphasis on product and batch traceability. [1,2]

The purpose of this article is to establish the conceptual foundation for the QPPV.com biosimilar series. It explains what biosimilarity means, why the biosimilar approach differs from the generic-medicine pathway, how the reference medicinal product is used during development, how the comparability exercise is structured, and what conclusions can and cannot be drawn from biosimilarity. It then connects those concepts with pharmacovigilance, where product identification, immunogenicity, comparative evidence and lifecycle surveillance become important.

The article deliberately remains at the biosimilar-framework level. Detailed treatment of generic-versus-biosimilar pharmacovigilance, reference-product safety evidence, traceability, switching, immunogenicity and biosimilar signal management will follow in dedicated articles rather than being compressed into this foundation.

What Is a Biosimilar?

Under the EU regulatory framework, a biosimilar is a biological medicinal product that is highly similar to another biological medicine already authorised in the European Union, referred to as the reference medicine. EMA explains that the comparison concerns relevant aspects including structure and biological activity and extends to the clinical domains of efficacy, safety and immunogenicity. [1]

The word "similar" is therefore a regulatory and scientific term with a specific meaning. It does not mean that the applicant has demonstrated that the proposed product is an identical molecular copy of the reference medicine. Nor does it mean that the products are unrelated biological medicines that merely produce the same clinical effect. The biosimilar approach establishes a defined degree of similarity using analytical, functional, non-clinical and, where appropriate, clinical evidence.

This is possible because biological medicines can be characterised at multiple levels. Modern analytical methods can compare primary structure, higher-order structure, post-translational modifications, purity, charge variants, aggregation, biological activity and other relevant quality attributes. The precise evidence package depends on the product and the scientific questions that remain after analytical comparison.

Biosimilarity is consequently a conclusion reached from the totality of a structured comparability exercise. It is not a conclusion derived from one test, one clinical trial or one measure of molecular similarity.

Why Biosimilars Are Biological Medicines

The first conceptual step is to place biosimilars within the wider biological-product taxonomy. A biosimilar is not a category separate from biological medicinal products. It is a biological medicinal product whose development and regulatory status are defined by its demonstrated similarity to a reference biological medicine.

This distinction matters because the characteristics that make biological medicines scientifically different from chemically synthesised medicines remain relevant after biosimilar authorisation. The biosimilar is produced through its own manufacturing process, has its own product identity and may have product-specific characteristics that need to be understood during pharmacovigilance. The reference product is an essential comparator in development, but it does not replace the biosimilar as the unit of post-authorisation safety surveillance.

The relationship can therefore be represented as:

biological medicinal product → reference biological medicine → biosimilar development → comparability exercise → biosimilar authorisation → product-specific pharmacovigilance

The last step is particularly important. Once the biosimilar is marketed, the pharmacovigilance system must be able to determine whether a safety report concerns the biosimilar, the reference product or another related biological medicine. Scientific relationships between the products can then be considered during signal evaluation without losing the identity of the product actually administered.

The Reference Medicinal Product

The reference medicinal product is the biological medicine against which biosimilarity is established. Its role is therefore fundamental to the scientific design of the biosimilar development programme.

The reference product provides the benchmark against which relevant quality attributes and, where required, non-clinical and clinical characteristics are compared. The choice and use of the reference product are governed by the applicable EU biosimilar framework and product-specific scientific guidance. The applicant does not simply select any biological medicine with the same active substance and assume that it is an acceptable comparator.

The reference product also provides an important body of prior knowledge. By the time a biosimilar is developed, the reference medicine may have accumulated substantial information concerning pharmacology, clinical use, efficacy, safety, immunogenicity and post-authorisation experience. This existing knowledge is scientifically relevant to the interpretation of the biosimilar evidence, but it does not eliminate the need to evaluate the biosimilar itself.

This distinction becomes particularly important in pharmacovigilance. A known safety characteristic of the reference product may provide useful context for evaluating a corresponding observation with the biosimilar. However, the report must remain associated with the actual medicinal product administered, and any conclusion that the observation represents a shared risk or a product-specific concern should be based on the evidence.

The Biosimilarity Exercise

The biosimilar development approach is based on a stepwise comparison. The aim is to identify and resolve relevant differences between the proposed biosimilar and the reference product, using the most sensitive and informative methods available for the scientific question.

Analytical and functional characterisation normally provides the foundation because it can directly examine the molecular and biological properties of the products. If residual uncertainty remains, the development programme may use additional non-clinical or clinical studies to address specific questions. The evidence is therefore not simply accumulated by adding increasingly large studies; each stage is intended to answer the uncertainty left by the preceding assessment.

A simplified conceptual sequence is:

Reference-product selection
        ↓
Analytical and structural comparison
        ↓
Functional / biological comparison
        ↓
Assessment of relevant differences
        ↓
Targeted non-clinical evidence where justified
        ↓
Targeted clinical evidence where justified
        ↓
Integrated assessment of biosimilarity
        ↓
Regulatory conclusion

The exact programme is product-specific. EU guidance has evolved as analytical science and clinical experience with biosimilars have developed, and EMA is currently consulting on a proposed revision of its overarching biosimilar guideline from 22 July to 31 October 2026. The currently effective overarching guideline remains Rev. 1, adopted in 2014 and legally effective from 30 April 2015, until a replacement guideline is adopted and becomes applicable. [3]

Analytical Similarity as the Foundation

Analytical comparison is central because biological molecules can be characterised directly across many relevant dimensions. Depending on the product, these may include identity, primary structure, higher-order structure, glycosylation, purity, aggregates, charge variants and biological activity.

The purpose is not to demonstrate that every analytical measurement is numerically identical. Biological products can display natural and process-related heterogeneity, and the relevant question is whether observed differences fall within a range compatible with the intended conclusion of similarity. The scientific significance of a difference depends on the attribute, its relationship to biological function, the magnitude and consistency of the difference, and the evidence available from other parts of the comparability exercise.

This analytical foundation distinguishes the biosimilar approach from the development of an entirely new biological medicine. The applicant begins with an existing reference medicine whose relevant characteristics can be extensively investigated and uses comparative evidence to establish that the proposed product is highly similar.

Biological and Functional Comparison

Structural similarity is necessary but is not sufficient if a structural attribute affects biological function. Functional assays can therefore be used to compare relevant biological activities, receptor interactions, binding characteristics, enzymatic activity or other product-specific functions.

The assays selected should be sensitive to differences that could have clinical significance. A highly similar analytical profile is most informative when it is accompanied by evidence that the products behave similarly in the biological systems relevant to their mechanism of action.

This also illustrates why the biosimilar concept cannot be reduced to molecular size or amino-acid sequence. A biological product can have the same intended protein sequence while differing in attributes such as glycosylation, aggregation or other structural features that may influence biological activity or immunogenicity. Conversely, a detected analytical difference is not automatically clinically meaningful. The assessment must connect the characteristic with function and, where necessary, clinical evidence.

From Similarity to Clinical Relevance

The purpose of the biosimilarity exercise is ultimately to support the conclusion that clinically meaningful differences have not been identified within the scope of the evidence and applicable regulatory framework. Clinical studies therefore have a different role from the role they would play in developing a new active substance from first principles.

The scientific logic is not that a biosimilar must independently reproduce the entire historical development programme of the reference medicine. Rather, the development programme uses comparative evidence to establish similarity and to address remaining uncertainty. Existing knowledge of the reference product can therefore reduce the need to repeat studies that would not provide additional useful information, while product-specific evidence remains necessary where uncertainty persists.

This is one reason why biosimilar development is often described as an evidence-generating exercise that is comparative rather than purely standalone. The comparison with the reference product is maintained throughout development, but the resulting authorised medicine remains a distinct product that requires its own post-authorisation surveillance.

The Role of Non-Clinical and Clinical Evidence

The amount and type of non-clinical and clinical evidence required for a biosimilar are determined by the scientific questions remaining after analytical and functional comparison. The objective is not to recreate the entire evidence package of the reference product, but to address residual uncertainty that cannot be resolved adequately through earlier comparative stages.

Clinical pharmacology can be particularly informative where sensitive measures of exposure and biological response can detect meaningful differences between products. Comparative clinical efficacy and safety studies may be appropriate when they provide information that cannot otherwise be obtained. The exact design depends on the molecule, mechanism, indication and state of the scientific and regulatory framework.

This stepwise logic is important for pharmacovigilance because it explains why the pre-authorisation evidence base for a biosimilar should not be interpreted as though it were a conventional new active substance programme. The reference product contributes substantial prior knowledge, while the biosimilar development programme focuses on demonstrating similarity and resolving uncertainty.

Immunogenicity in Biosimilar Development

Immunogenicity is a specific component of biological-product development because an immune response can potentially alter exposure, biological activity, clinical response or tolerability. The relevant risk depends on the molecule, its structural characteristics, treatment duration, route of administration, patient population and other factors.

For biosimilars, immunogenicity is assessed comparatively with the reference product using appropriate analytical, clinical and immunological evidence. A difference in the measured frequency of antibodies is not automatically a clinically meaningful difference, just as a similar measured frequency does not by itself establish identical clinical consequences. The interpretation depends on the characteristics of the immune response and its relationship to pharmacokinetic, pharmacodynamic, efficacy and safety outcomes.

This distinction becomes important after authorisation. Pharmacovigilance should not treat the detection of anti-drug antibodies as an adverse event by definition. It should determine whether an immune response is clinically relevant to the product-specific safety question and whether the evidence suggests an effect on treatment or patient outcome.

Extrapolation of Indications

A biosimilar may be authorised for more than one indication held by the reference product when the scientific and regulatory criteria for extrapolation are satisfied. Extrapolation does not mean that evidence for one indication is simply assumed to be identical in another. It reflects an assessment that the totality of the evidence, including mechanism of action and relevant clinical considerations, supports use across the proposed indications.

The distinction is important for pharmacovigilance because the safety profile may be observed in different populations, with different disease characteristics, treatment durations and concomitant therapies. Surveillance should therefore preserve the indication and relevant clinical context rather than assuming that all experience with a biosimilar belongs to one homogeneous population.

A safety observation in an extrapolated indication may also raise a scientific question about whether the underlying mechanism is shared across indications. That question should be assessed from the evidence rather than inferred from the existence of the extrapolated authorisation alone.

What Biosimilarity Establishes

Biosimilarity establishes a regulatory conclusion based on the evidence generated in the comparability exercise. In practical terms, it supports the conclusion that the proposed product is highly similar to the reference medicinal product and that there are no clinically meaningful differences in the relevant aspects within the scope of the assessment.

The conclusion provides a scientifically justified basis for the regulatory use of the reference product's existing knowledge, including where the applicable framework permits extrapolation to indications. It also means that the biosimilar enters clinical use within an established biological and pharmacological context rather than as an entirely unknown biological substance.

For pharmacovigilance, this existing knowledge is valuable. It can inform expectedness, biological plausibility, signal evaluation and benefit-risk assessment. It can also help determine whether a reported event represents a new observation, a known risk, a potentially shared biological effect or a question that requires product-specific investigation.

What Biosimilarity Does Not Establish

Biosimilarity does not mean that the biosimilar and reference product are the same medicinal product. They remain distinct authorised products with their own product identities and manufacturing histories.

It also does not mean that every future safety observation for the reference product must automatically be attributed to the biosimilar, or that a safety report concerning the biosimilar should be reassigned to the reference product. The pharmacovigilance system must preserve the identity of the actual administered product.

Nor does biosimilarity eliminate the possibility of product-specific safety information emerging after authorisation. Post-authorisation surveillance exists precisely because clinical use expands beyond the conditions and populations studied before authorisation and because uncommon events may become detectable only with wider exposure.

The appropriate principle is therefore:

biosimilarity informs interpretation; it does not replace product-specific pharmacovigilance.

Biosimilar Pharmacovigilance Within the EU GVP Framework

Once authorised, a biosimilar is subject to the general EU pharmacovigilance system. EMA's current biosimilar overview explicitly states that the safety of biosimilars is monitored through pharmacovigilance activities after marketing in the same general way as other medicines. The biological-medicinal-product GVP guidance adds product-specific considerations, particularly around traceability, immunogenicity and the distinction between related biological products. [1,2]

This means that there is no separate pharmacovigilance system called "biosimilar pharmacovigilance" in place of GVP. Instead, biosimilar pharmacovigilance is the application of the general system to a product whose scientific context includes a reference biological medicine and a prior comparability assessment.

The practical consequences are concentrated in the evidence rather than in a different set of fundamental PV processes. Case management, signal management, aggregate reporting, risk management and safety communication continue to operate within the established GVP framework. The biosimilar context affects what information needs to be preserved and how evidence should be interpreted.

Product Identity After Authorisation

The distinction between a biosimilar and its reference product makes product identification particularly important. A case should identify the medicinal product that the patient actually received whenever that information is available. If the product cannot be identified with confidence, the uncertainty should remain visible and should be addressed through proportionate follow-up when the information is material to the safety question.

This principle applies even when products share the same active substance or have highly similar biological characteristics. A safety database that collapses all products into a single active-substance category may be useful for some analyses, but it should not destroy the product-level information needed for case assessment and signal detection.

EMA's biological-product GVP guidance specifically highlights the need for different biological products with the same international non-proprietary name to remain readily distinguishable so that product-specific safety concerns and immunogenicity can be detected and evaluated. [2]

Product and Batch Traceability

Traceability extends beyond the product name. Where relevant information is available, the pharmacovigilance system should be capable of linking a report to the product, batch or lot and exposure circumstances. Batch information may become particularly important if a potential quality or manufacturing-related concern emerges.

The absence of batch information does not automatically make an individual case unusable. Its importance depends on the question being investigated. The operational objective is to preserve available traceability information and ensure that it remains accessible if a later signal requires a more focused investigation.

Traceability is therefore an evidence-preservation function. It should not be interpreted as evidence that biological products are unsafe or that every batch must be investigated for every adverse event.

The Reference Product as a Source of Safety Knowledge

The reference medicinal product can provide extensive pre-authorisation and post-authorisation safety information. That information may include known adverse reactions, identified and potential risks, immunogenicity experience, long-term exposure and evidence from a broad range of clinical settings.

For the biosimilar, the reference-product safety profile provides an important scientific baseline. A reported event may already be well established for the reference product and biologically plausible for the biosimilar. In that circumstance, the reference experience can help interpret the report, but the case remains a report concerning the biosimilar if that was the product administered.

The distinction between using evidence and reassigning a case is therefore fundamental. Comparative evidence may be integrated across related products when scientifically justified, while the underlying exposure data remain product-specific.

Biosimilar-Specific Evidence After Authorisation

Post-authorisation evidence can provide information that was not available during development. Larger patient populations, longer exposure, broader clinical use, different treatment patterns and routine healthcare practice can reveal safety information that was difficult to characterise in comparative studies.

For a biosimilar, this evidence should be considered together with the pre-authorisation comparability package and the reference-product knowledge base. A new report can therefore be interpreted in three related contexts: what is known about the biosimilar itself, what is known about the reference product, and what is known about the wider biological or pharmacological class.

These contexts should be connected without being collapsed into one. The evidence hierarchy is not a reason to assume that every observation belongs to the reference-product profile, nor is it a reason to ignore established information simply because the report concerns a different product.

A Three-Level Evidence Model

The pharmacovigilance interpretation of a biosimilar can be represented as three connected levels:

The levels should be considered in sequence and according to the safety question. Evidence from a reference product may strengthen biological plausibility without establishing causality for the biosimilar. Conversely, a biosimilar-specific pattern may justify evaluation of the reference product or other related products when a shared mechanism is plausible.

The central control is preservation of the distinction between where the observation occurred and where supporting evidence comes from.

Regulatory Status and Evolving Guidance

The EU biosimilar framework is mature but not static. EMA's current scientific-guideline page identifies the overarching guideline on similar biological medicinal products, Rev. 1, as the current effective version. In July 2026, EMA opened a consultation on a draft replacement guideline, with consultation scheduled from 22 July to 31 October 2026. [3]

The existence of a draft revision does not make the draft the applicable legal or scientific requirement. Until a revised guideline is adopted and becomes applicable, the current effective framework remains the relevant basis for regulatory decisions, supplemented by applicable product-specific guidelines and procedural advice.

This distinction is particularly important for QPPV.com because biosimilar science is developing alongside regulatory guidance. Articles should therefore distinguish the current effective framework from proposals, consultation documents and emerging scientific interpretation.

Signal Detection in Biosimilar Pharmacovigilance

The general principles of signal detection apply to biosimilars, but product identification and the reference-product context can materially affect interpretation. A potential signal may arise from individual case reports, case series, quantitative analyses, clinical studies, literature, registries, post-authorisation studies, quality information or other relevant sources.

The first analytical question remains whether the observed pattern is credible as a potential safety concern. Once that question is established, the biosimilar context adds further questions. Is the observation already recognised for the reference product? Is it consistent with the known pharmacology of the biosimilar? Does it appear specific to the biosimilar, or could it plausibly represent a broader effect? Is there a product-quality or manufacturing context? Is the apparent pattern influenced by switching, stimulated reporting or changes in exposure?

These questions should not be answered by simply pooling all available reports. Pooling can increase statistical power but may also remove the product-level information needed to identify a product-specific signal. A sound analysis therefore preserves product identity while using comparative evidence at the level appropriate to the scientific question.

Signal Validation and Product Attribution

Signal validation requires a credible association between a medicinal product and a potential safety concern that warrants further analysis. For a biosimilar, attribution should begin with the actual product exposure.

If several products share an active substance, an apparent signal may be distorted if cases are coded inconsistently or if cases for different products are aggregated before product identity has been established. Conversely, a narrow analysis confined to the biosimilar may overlook evidence from the reference product that is relevant to biological plausibility or prior knowledge.

The appropriate solution is not to choose one dataset and exclude the other. It is to retain product-specific data while explicitly defining which comparative evidence is being used and why. This allows the assessor to distinguish an observation, its supporting evidence and the conclusion reached from the totality of that evidence.

Known Reference-Product Risks

A biosimilar may be associated with adverse reactions that are already well characterised for the reference product. The presence of such an event after biosimilar exposure is therefore not automatically evidence of a new biosimilar-specific signal.

The reference-product safety profile can provide useful context for expectedness, biological plausibility and risk interpretation. However, the fact that an event is known for the reference product does not remove the need to assess the biosimilar case. The assessor should determine whether the clinical circumstances are compatible with the established risk and whether any features suggest a product-specific difference.

This distinction is especially important when a known event has multiple potential mechanisms. A similar clinical phenotype may arise from the shared pharmacology of the products, from administration circumstances or from another factor. The reference-product experience informs the assessment but does not dictate its conclusion.

New or Potentially Product-Specific Safety Information

A safety observation that is not established for the reference product may require particular attention, but novelty alone does not establish causality. The observation may represent a previously unrecognised risk of the shared biological mechanism, a product-specific characteristic, a reporting artefact, confounding or a chance occurrence.

The assessment should therefore consider the strength and consistency of the evidence, temporal relationships, alternative explanations, biological plausibility, exposure patterns and evidence from other data sources. Where appropriate, the reference product and related products can be evaluated to determine whether similar observations have occurred.

A biosimilar-specific signal can be scientifically meaningful even when the reference product has no corresponding signal. Conversely, the absence of reports for the reference product may reflect differences in exposure, reporting or surveillance rather than a true biological difference.

Comparative Safety Evidence

Comparative safety evidence can arise from randomised studies, observational studies, registries, post-authorisation safety studies, literature and other sources. The value of each source depends on the question and study design.

Comparative evidence is particularly useful when the scientific question concerns whether a safety characteristic differs between the biosimilar and reference product. However, a lack of observed difference in a study does not necessarily prove equivalence for every rare or delayed event. The sensitivity of the evidence to the event being investigated must be considered.

For rare events, spontaneous reports and case series may provide the initial evidence, while epidemiological studies may be required to estimate incidence or compare risks. For immunogenicity, antibody characteristics may need to be interpreted alongside clinical outcomes. For manufacturing concerns, batch and quality information may be essential.

The evidence should therefore be matched to the question rather than ranked by source type alone.

Immunogenicity and Pharmacovigilance Interpretation

Immunogenicity deserves particular attention because biological products can induce antibodies or other immune responses that may have different clinical consequences. In biosimilar assessment, the comparison with the reference product helps establish whether the immune response is sufficiently similar within the evidence available for authorisation.

Post-authorisation pharmacovigilance must nevertheless remain alert to clinically relevant immune-mediated events. A detected antibody response may be clinically silent, may correlate with altered exposure, may reduce biological activity or may contribute to hypersensitivity. The meaning depends on the product and the clinical evidence.

The appropriate pharmacovigilance question is therefore not simply whether antibodies are present. It is whether the immune response is associated with a clinically meaningful outcome and whether the evidence supports a product-specific or broader interpretation.

Switching and the Interpretation of Safety Reports

Patients may receive different biological products over time. The interpretation of a subsequent safety event can depend on the complete exposure sequence, particularly when the event is delayed or potentially immune-mediated.

A report after switching should therefore retain information on the previous product, the date of switching and the timing of the event. The occurrence of an event after a switch does not establish that the new product caused it. It does, however, make exposure chronology more important.

Switching can also influence reporting behaviour. Patients and healthcare professionals may be more likely to report events following a change in treatment, which can create apparent temporal associations that require careful evaluation. The assessment should therefore consider both biological and reporting explanations.

Manufacturing Changes and Biosimilar Safety Surveillance

A biosimilar has its own manufacturing process, and manufacturing changes may occur after authorisation. Such changes are subject to the applicable quality and regulatory framework, including comparability assessment where required.

Pharmacovigilance provides a complementary source of post-change clinical evidence. If a safety pattern emerges after a significant manufacturing change, the timing and affected batches may become relevant to the investigation. However, post-change occurrence alone does not establish a causal relationship.

The appropriate investigation connects the pharmacovigilance evidence with quality and manufacturing information while preserving the distinction between a quality assessment and a clinical safety conclusion.

Risk Management for Biosimilars

The risk management system for a biosimilar reflects the risks and missing information relevant to the individual product. Existing knowledge of the reference product can be important in defining the safety specification, while biosimilar-specific evidence may modify the understanding of particular risks.

EMA's biological-product GVP guidance states that, as a general principle, post-authorisation RMP updates for a reference product should similarly apply to relevant biosimilars and related products, and vice versa, unless there is justification that the clinical concern is product-specific or otherwise not applicable. [2]

This principle does not mean that every RMP change must automatically be identical across products. It means that safety information affecting related products should be considered systematically, with product-specific differences assessed and documented where relevant.

Risk-minimisation measures should follow the actual safety problem. The fact that a medicine is a biosimilar does not itself mandate a particular additional risk-minimisation measure.

Aggregate Safety Evaluation

Aggregate evaluation provides the context in which individual biosimilar cases are interpreted over time. Relevant evidence may include spontaneous reports, clinical studies, post-authorisation studies, literature, epidemiological data, immunogenicity information, reference-product experience and quality or manufacturing information.

The assessment should preserve enough product-level granularity to determine whether an observed pattern belongs to the biosimilar, the reference product or a broader biological mechanism. At the same time, the evaluator should use the reference-product evidence when it provides relevant background knowledge.

This balance is important because the same adverse event can occupy different analytical positions. It may be a known class effect, a known reference-product risk also seen with the biosimilar, a possible product-specific signal, or an unrelated background event. The conclusion depends on the evidence rather than the category assigned at the outset.

Safety Communication

When a safety issue involving a biosimilar requires communication, the communication should identify the relevant product and explain the evidence accurately. Where the concern also affects a reference product or other related biological medicines, the communication strategy may need to reflect that relationship.

EMA's post-authorisation guidance for similar biological medicinal products describes situations in which safety variations and communications may involve both the reference medicinal product and biosimilars and notes the value of coordinated communication where products share the same active substance. [4]

The communication should nevertheless avoid implying that all products have identical safety profiles unless the evidence supports that conclusion. The distinction between shared evidence and product-specific attribution should remain clear.

Practical Evidence and Record Requirements

A mature biosimilar pharmacovigilance system should be capable of reconstructing the evidence underlying an important safety conclusion. Depending on the question, this may include:

The exact evidence required depends on the safety question. The objective is not maximal data collection but sufficient traceability and scientific reconstruction.

Roles and Interfaces

Biosimilar pharmacovigilance requires controlled interfaces between pharmacovigilance, medical, regulatory, quality, manufacturing, clinical and supply functions. The precise organisational structure is not universal, but the information flows should support the safety questions that arise from the product's characteristics and regulatory history.

Quality and manufacturing functions may hold information about batches, process changes and investigations. Regulatory functions may hold information about variations, commitments and interactions with authorities. Medical and clinical functions provide mechanistic and clinical context. Pharmacovigilance integrates relevant information into safety assessment and governance.

The reference-product relationship adds another dimension: teams must be able to access relevant reference-product safety information without allowing that information to obscure the identity of the biosimilar exposure.

Potential Failure Modes

Several potential failure modes are particularly relevant to biosimilar pharmacovigilance.

Product collapse: reference and biosimilar reports are aggregated under a common active-substance identifier and product identity is lost.

Reference-product substitution in assessment: a biosimilar case is treated as though it were a reference-product case because the event is already known for the reference medicine.

Failure to use reference knowledge: established reference-product evidence is ignored, making the assessment less informative than it could be.

Unjustified class attribution: an observation with one biosimilar is assumed to apply to every product containing the same active substance without adequate evidence.

Immunogenicity over-interpretation: detection of anti-drug antibodies is treated as proof of clinical harm without evidence linking the immune response to the outcome.

Loss of switching history: previous biological exposures are not captured, weakening assessment of delayed or immune-mediated events.

These are illustrative potential failure modes, not documented inspection findings.

Inspection Perspective

Inspection of biosimilar pharmacovigilance should focus on whether the organisation can demonstrate that the product-specific and comparative dimensions of the evidence are both controlled.

An inspector could examine whether the actual administered product can be identified, whether switching history is retained, whether reference-product information is used appropriately, whether biosimilar-specific evidence is evaluated independently where necessary, and whether quality or manufacturing information is connected to safety assessment when relevant.

The strongest evidence is reconstructability. A reviewer should be able to trace a significant conclusion from the incoming observation through product identification, evidence review, assessment, decision, action and follow-up.

These are illustrative inspection questions rather than claims about specific inspection findings.

Practical Implementation Framework

An operational framework can be organised around five controls:

1. Identify the product. Preserve the identity of the biosimilar actually administered.
2. Reconstruct exposure. Capture dates, treatment history, switching and batch information when relevant and available.
3. Use comparative knowledge correctly. Consider reference-product and class evidence without replacing product-specific assessment.
4. Match evidence to the question. Use clinical, immunogenicity, epidemiological, quality and other evidence according to the uncertainty being investigated.
5. Document the conclusion. Preserve the reasoning, uncertainty, decision and follow-up so that the assessment remains reconstructable.

These controls apply the general GVP framework to the specific scientific context of biosimilars. They do not create a separate pharmacovigilance system.

Key Takeaways

A biosimilar is a biological medicinal product that has been shown through a structured comparability exercise to be highly similar to an authorised reference biological medicine. The concept is based on a totality of evidence rather than a single analytical or clinical test.

The biosimilar approach differs fundamentally from the conventional generic-medicine pathway because biological active substances are produced through complex biological systems and cannot generally be demonstrated to be equivalent through the same type of pharmaceutical equivalence and bioequivalence approach used for chemically synthesised small molecules.

The reference medicinal product is central to biosimilar development because it provides the comparator and an established body of scientific and clinical knowledge. That knowledge remains valuable after authorisation, but the biosimilar remains a distinct medicinal product with its own identity and pharmacovigilance history.

Biosimilar pharmacovigilance therefore combines two requirements that must be kept together: use comparative knowledge appropriately and preserve product-specific evidence. A case involving a biosimilar should remain identifiable as a biosimilar case even when the reference product provides important context for interpretation.

The most important operational consequences concern product and batch traceability, exposure history, switching history, appropriate interpretation of immunogenicity, integration of reference-product knowledge, connection with quality and manufacturing information, and evidence-based signal evaluation.

Actionable Checklist

Relationship With the Wider QPPV.com Pharmacovigilance Framework

The biosimilar series sits within the broader biological-product framework established by the preceding QPPV.com articles. The biological-product classification explains why product identity, manufacturing characteristics, immunogenicity and traceability can matter. The biosimilar framework adds the particular relationship between a biosimilar and its reference medicinal product.

This relationship should then be connected to the general pharmacovigilance processes described elsewhere in the knowledge base. Individual case processing provides the exposure-specific evidence; signal management evaluates emerging patterns; aggregate reporting integrates the broader evidence base; risk management governs identified and potential risks; and benefit-risk evaluation connects safety findings with therapeutic benefit.

The biosimilar context changes the evidence that enters those processes, not the existence of the processes themselves. A biosimilar should therefore not be treated as a special pharmacovigilance system. It should be treated as a biological medicinal product for which comparative scientific knowledge and product-specific surveillance must operate together.

This distinction provides the foundation for the next articles in the biosimilar series. The comparison with generic medicines will examine why the development and safety evidence differ. The reference-product article will examine how established safety knowledge should influence biosimilar surveillance without replacing it. Later articles can then address traceability, switching, immunogenicity and biosimilar-specific signal management in greater depth.

References

1. European Medicines Agency. Biosimilar medicines: Overview. EMA. Current overview of the definition of a biosimilar, the reference medicine relationship and post-authorisation pharmacovigilance.
2. European Medicines Agency. Guideline on good pharmacovigilance practices (GVP): Product- or Population-Specific Considerations II: Biological medicinal products. EMA/168402/2014. In particular, sections concerning immunogenicity, traceability and reference products, biosimilars and related biological products.
3. European Medicines Agency. Guideline on similar biological medicinal products (Rev. 1). CHMP/437/04 Rev.1. Adopted 29 October 2014; legal effective date 30 April 2015. EMA's current effective overarching guideline pending adoption of the proposed revision.
4. European Medicines Agency. Biosimilar medicines: Marketing authorisation — post-authorisation safety variations and communication. EMA procedural guidance, including considerations for reference medicinal products and biosimilars with the same active substance.
5. European Medicines Agency. Guideline on similar biological medicinal products containing biotechnology-derived proteins as active substance: non-clinical and clinical issues. EMA/CHMP/BMWP/42832/2005 Rev. 1, and associated product-specific biosimilar guidance.
6. European Medicines Agency. Guideline on similar biological medicinal products containing biotechnology-derived proteins as active substance: quality issues. EMA/CHMP/BWP/247713/2012 Rev. 1, and associated product-specific quality guidance.
7. European Medicines Agency. Guideline on immunogenicity assessment of biotechnology-derived therapeutic proteins. EMA/CHMP/BMWP/14327/2006 Rev. 1.
8. European Medicines Agency. Good pharmacovigilance practices (GVP). General GVP modules and product- or population-specific considerations.
9. European Parliament and Council. Directive 2001/83/EC on the Community code relating to medicinal products for human use, as amended.
10. European Parliament and Council. Regulation (EC) No 726/2004 laying down Community procedures for the authorisation, supervision and pharmacovigilance of medicinal products for human and veterinary use, as amended.
11. International Council for Harmonisation. ICH Q5E: Comparability of Biotechnological/Biological Products Subject to Changes in Their Manufacturing Process.

Regulatory Note

This article distinguishes legal requirements from scientific and regulatory guidance. EU legislation establishes the legal framework for medicinal-product authorisation and pharmacovigilance. EMA guidelines provide scientific and regulatory guidance for applicants, assessors and other stakeholders and should not be presented as legislation.

The overarching EMA biosimilar guideline currently effective in the EU remains Rev. 1. EMA opened a public consultation on a proposed revision on 22 July 2026, with consultation closing on 31 October 2026. The proposed revision is not itself the applicable final guideline and should not be presented as a current legal or regulatory requirement. [3]

Operational controls described in this article, such as preserving product-level traceability and reconstructing switching history, are presented as pharmacovigilance practice informed by the applicable regulatory framework. They should not be interpreted as additional legal requirements unless the applicable legislation, regulatory guidance or product-specific regulatory documentation establishes such a requirement.

Regulatory and scientific guidance can change. Current EU legislation, the applicable EMA GVP guidance, the effective biosimilar guidelines, product-specific regulatory documentation and relevant national requirements should therefore be checked when applying this framework to a particular product or regulatory decision.