Release Testing for Biologics – Regulatory Requirements for GMP Compliance

Release testing is the final quality gate in biologics manufacturing, ensuring each batch of a drug meets all quality standards before patients ever receive it. By rigorously analyzing critical attributes like purity, potency, identity, and sterility, manufacturers confirm the product’s safety and efficacy. This article explores what release testing entails, why it is crucial for biologics, the key quality attributes and analytical methods involved, the regulatory requirements (FDA and EMA) governing these tests, and best practices and common pitfalls in achieving Good Manufacturing Practice (GMP) compliance. 

What Is Release Testing and Why It Matters in Biologics Manufacturing? 

Release testing refers to the battery of quality control assays performed on each batch of a biologic drug (whether a drug substance or finished drug product) before it is released for use in clinical trials or commercial distribution. It is a mandatory GMP step that verifies the batch meets all predefined specifications approved by regulators. In practice, this means physicochemical, biological, and microbiological tests are conducted to ensure the product’s identity, strength, purity, and safety conform to set standards. Only if the batch passes all these criteria can the manufacturer’s quality unit (or a Qualified Person in the EU) certify the batch for release. 

This process matters enormously in biologics manufacturing because biologics are complex, sensitive products produced in living systems. Release testing provides final confirmation that the manufacturing process operated correctly and consistently, and that the product will be safe and effective for patients. It is the last opportunity to catch any impurities, loss of potency, contamination, or other issues before the product leaves the factory. In essence, release testing protects patients by preventing substandard or unsafe batches from reaching the market. It also ensures compliance with the product’s regulatory submissions – each lot must conform to the specification that was reviewed and approved by authorities during development. 

Effective release testing signals that the upstream manufacturing process is in control. If a batch fails release specifications (for example, if potency is too low or a contaminant is detected), it not only delays supply but also triggers investigations into the production process. Thus, comprehensive release testing serves both as a quality safeguard and a feedback mechanism: it verifies product quality and provides data to confirm that manufacturing and purification steps are performing as intended.  

Given the high stakes – patient safety, regulatory compliance, and company reputation – release testing in biologics manufacturing is an indispensable practice. Many biopharmaceutical companies turn to specialized biologics CDMO partners for support at this critical stage. At Mabion, we not only conduct a comprehensive GMP release testing panel for drug substances and medicinal products, but also offer batch release services through a Qualified Person (QP), integrating final regulatory control into our services. By rigorously testing every batch and certifying results, such integrated approaches ensure that only biologic products meeting all quality requirements move forward to patients. 

Critical Quality Attributes Required for Biological Drugs Release 

Regulatory guidelines and industry best practices define several critical quality attributes (CQAs) that every biologic must be evaluated for prior to release. These CQAs are properties of the product that have a direct impact on its safety, efficacy, or quality. For biologics, the key attributes can be grouped into four main categories – Identity, Purity, Potency, and Safety (including sterility) – with additional physical characteristics also assessed as needed. Each batch of a biological drug must meet acceptance criteria for each of these attributes as part of its release specifications. 

Identity 

Identity testing confirms that the product is exactly what it is supposed to be – the correct biologic entity produced from the right cell line or expression system. For example, a monoclonal antibody’s identity is established by verifying its protein structure (amino acid sequence and expected modifications) or specific binding characteristics. Regulations require an identity test on the final lot to distinguish it from any other product. Highly specific methods are used, such as peptide mapping by mass spectrometry or immunochemical assays (e.g., ELISA, Western blot), to ensure the molecule’s identity matches the reference standard. Identity testing is critical because it prevents mix-ups and ensures that every vial contains the intended therapeutic, properly labeled and traceable. 

Purity 

Purity measures the degree to which the biologic product is free from impurities and contaminants. Biologics often have complex impurity profiles, including product-related impurities (e.g. aggregated forms, fragmented molecules, misfolded variants) and process-related impurities (such as host cell proteins, residual DNA, or reagents from production). A released batch must achieve a high level of purity, typically defined by a percentage of the main active ingredient and limits on specific impurities.  

For instance, guidelines set strict limits on aggregates and degraded forms because they can affect safety or efficacy. Purity is usually assessed by multiple complementary tests – for example, high-performance liquid chromatography and electrophoresis can reveal product variants, and immunoassays can detect host cell protein contaminants. A pure biologic product ensures that patients are not exposed to unwanted proteins or substances that could trigger immune reactions or reduce the drug’s effectiveness. 

Potency 

Potency is a measure of the biological activity of the product – essentially, it answers the question: does the product have the expected effect, and how strong is that effect? For therapeutic proteins like antibodies or cytokines, potency reflects the ability to bind to a target or elicit a biological response at a specified level. Regulatory authorities in both the US and EU require a quantitative potency assay for all biological medicines. In the U.S., potency is legally defined as the product’s specific ability to achieve its intended effect, as demonstrated by suitable laboratory tests or clinical data. Thus, each batch must be tested with a validated bioassay (which could be an in vitro cell-based assay, an enzyme activity assay, an ELISA, or another method reflecting the product’s mechanism of action) to confirm it meets the potency specification.  

Potency testing is critical for ensuring consistent efficacy from batch to batch – a vaccine, for example, must induce a sufficient immune response, and a monoclonal antibody must bind its antigen with the requisite strength. If a batch’s potency drifts below the set specification, it cannot be released because it may not produce the desired therapeutic effect in patients. 

Safety  

Safety attributes encompass the freedom from contaminants that could harm patients. Chief among these for an injectable biologic is sterility – the absence of viable bacteria or fungi in the product. Because most biologics are administered parenterally (intravenously, subcutaneously, etc.), sterility is an absolute requirement. Each lot must undergo a sterility test to confirm no microbial growth; a batch that fails sterility cannot be released.  

In fact, 21 CFR 610.12 and EU guidelines make sterility testing mandatory for biologic products that are supposed to be sterile. In addition to sterility, other safety-related tests include endotoxin levels, which must be below strict thresholds (e.g. per USP <85> for endotoxins) to prevent fever or shock in patients, and mycoplasma testing for products derived from cell culture to ensure no insidious cell-wall-free bacteria are present. These safety tests collectively ensure the biologic product will not introduce infections or toxic reactions.  

Biologics release panels, therefore, always include sterility (and often endotoxin) tests as critical release criteria. For example, a monoclonal antibody lot would be tested to confirm sterility and that endotoxin levels are below the maximum allowable limits set by USP <85> or EU Ph. Eur. Only batches that meet sterility and endotoxin specifications are suitable for human use.

Beyond the big four above, release testing also covers general physicochemical properties to confirm the product’s proper formulation and consistency. While these tests are often considered “less critical” than the identity, purity, potency, and sterility, they are nonetheless important for overall product quality and patient experience. For instance, checking pH and osmolality ensures the injection will not cause tissue irritation or instability of the protein. Appearance and clarity checks ensure there are no unexpected precipitates or coloration that might indicate a process problem. These parameters are typically included in release specifications and must fall within predefined ranges. 

Release testing of biologics is built around verifying these critical quality attributes. It confirms that the correct product has been made (identity), that it is pure, potent, and safe for use, and that it conforms to all predefined quality measures. If any one of these dimensions is out of spec, the batch cannot be released. 

Analytical Methods Commonly Used in Release Testing of Biologics 

Ensuring that a biologic meets all its release criteria requires a toolkit of diverse analytical methods. Biologic drugs are far more complex than traditional small-molecule drugs, so a wide range of specialized assays is employed to measure each critical attribute. These methods span traditional chemistry techniques, advanced biophysical analyses, biological assays and microbiological tests – each chosen and validated to accurately assess a particular aspect of the product’s quality. 

High-Performance Liquid Chromatography (HPLC) 

High-Performance Liquid Chromatography (HPLC) is a workhorse in biologics quality control, used extensively to assess purity, heterogeneity, and in some cases quantity of the drug. Various modes of HPLC are applied: for example, Size-Exclusion Chromatography (SEC) HPLC is routinely used to detect and quantify protein aggregates or fragments in a biologic product. An SEC-HPLC assay will separate the sample by molecular size, allowing analysts to see if the majority of protein is the correct monomer and if any high-molecular-weight aggregates or low-molecular-weight fragments are present, and at what percentages. A predominantly monomeric peak with minimal aggregate peaks indicates the product meets purity requirements.  

HPLC can also measure the concentration of the active protein by comparing peak areas to a standard. Overall, HPLC methods give a detailed fingerprint of the biologic’s composition. For instance, an SEC-HPLC chromatogram can confirm that, say, 98% of the protein is monomer and only 2% is dimer or higher aggregates – information critical for batch release. It should be noted that while HPLC reveals the chemical purity and structural variants of the product, it does not measure biological activity. A size-exclusion HPLC chromatogram might show a protein is predominantly monomeric, but that alone “does not provide information about its biological effect,” so a separate potency assay is required to define the drug’s activity. 

HPLC is a workhorse in biologics quality control, used extensively to assess purity, heterogeneity, and in some cases quantity of the drug. Various modes of HPLC are applied. 

Size-Exclusion Chromatography (SEC-HPLC) is routinely used to detect and quantify protein aggregates or fragments in a biologic product. An SEC-HPLC assay will separate the sample by molecular size, allowing analysts to see if the majority of protein is the correct monomer and if any high-molecular-weight aggregates or low-molecular-weight fragments are present, and at what percentages. A predominantly monomeric peak with minimal aggregate peaks indicates the product meets purity requirements.  

Ion-Exchange Chromatography (IEX-HPLC) separates molecules based on charge differences, detecting charge variants or isoforms that may arise from post-translational modifications or process-related changes. IEX-HPLC provides insight into identity and consistency of the biologic, as well as purity in terms of variant distribution. 

Reversed-Phase HPLC (RP-HPLC) is used to characterize hydrophobic variants, degraded species, or certain post-translational modifications. This method helps confirm the structural integrity of the product and supports assessment of purity. 

Quantification of active protein is achieved by comparing HPLC peak areas to validated reference standards. This measurement ensures that each batch meets the potency specification, confirming consistent biological performance when combined with functional bioassays. 

Analysis of formulation components, such as excipients (e.g., Polysorbate 80), can also be performed using HPLC. Monitoring excipient levels ensures proper formulation, stability, and patient safety, linking HPLC results to physicochemical quality attributes. 

By integrating these complementary HPLC methods, release testing generates a comprehensive chemical and structural fingerprint of each batch. All assays are fully validated, aligned with regulatory requirements, and included in the release panel to confirm that each lot meets predefined specifications. It should be noted that while HPLC reveals the chemical purity and structural variants of the product, it does not measure biological activity.  

Mass spectrometry 

Mass spectrometry (MS) is a powerful analytical technique increasingly used in biologics release and characterization for its ability to precisely determine molecular mass and structure. In release testing, mass spectrometry is commonly employed to confirm identity and detect molecular variants of the biologic. One typical approach is peptide mapping: the protein is enzymatically digested (e.g. with trypsin) into peptides, which are then analyzed by LC-MS to verify the amino acid sequence and any post-translational modifications by matching the peptide masses to the expected values. This provides a high-resolution identity check – essentially a molecular fingerprint – ensuring that the product’s primary structure is correct.  

Mass spec can also perform intact mass analysis of the whole protein, which is useful for confirming the presence of the correct heavy and light chains of an antibody and identifying variants like glycoforms. Additionally, MS methods are capable of identifying impurities: for example, if an unknown peak appears in an HPLC purity assay, mass spectrometry can help identify that impurity by its mass and fragmentation pattern. Regulatory agencies accept MS-based identity tests, and indeed a comprehensive LC-MS identity strategy for biologics release has been outlined by scientists to increase the robustness of identity confirmation.  

In current practice, mass spectrometry provides critical high-detail data that complement other assays: it assures that each batch’s molecular makeup is as expected and that no stealth changes have occurred in production. The adoption of MS in QC labs (once limited due to complexity) is growing, reflecting its value in ensuring biologic products’ consistency and compliance with molecular specifications. 

Enzyme-Linked Immunosorbent Assay (ELISA) 

Enzyme-Linked Immunosorbent Assay (ELISA) is a staple bioanalytical method in biologics testing, prized for its specificity and sensitivity in detecting proteins or antibodies. In release testing, ELISAs are frequently used either to measure the potency of a biologic or to quantify trace contaminants. A classic example is a binding ELISA to measure the potency of an antibody: plates are coated with the target antigen, and the biologic (antibody) is added – the amount that binds (detected via a secondary antibody and colorimetric readout) indicates the antibody’s functional binding activity. This can serve as a surrogate for biological activity when the mechanism of action is binding to a specific ligand. ELISA can provide a quantitative readout of concentration as well; for instance, a sandwich ELISA might be used to determine the exact concentration of the therapeutic protein in the final container by comparing it against a standard curve.  

ELISAs are also extensively used for impurity testing, such as the host cell protein (HCP) ELISA – a broad specificity polyclonal antibody-based assay that detects residual host cell proteins from the production cells. For a biologic made in CHO cells, an HCP ELISA will ensure that total contaminant proteins are below a ppm-level threshold in the batch. In the context of release, ELISAs are valued for their high specificity (antibodies can distinguish the product or impurity of interest amidst many other components) and relative ease of use in a QC lab. They do require well-characterized antibodies and standards, and their accuracy hinges on those reagents. When properly developed and validated, however, an ELISA can reliably assure, for example, that the drug’s potency is on target (say, 100±20% of label claim) or that undesirable proteins (like host cell protein or cytokine impurities) are under control. ELISA methods are typically part of the release specifications for biologics where a specific binding activity or contaminant level must be measured. As a result, they play a central role in demonstrating that the batch is not only chemically correct but also biologically active and clean from a immunological standpoint. 

Visible and Subvisible Particles 

Because most biologics are delivered via injection, the presence of particulate matter is a major quality and safety concern. Visible particles are particles large enough to see with the naked eye (typically >100 microns), and subvisible particles are smaller (down to about 10 microns) that require instrumentation to detect. Release testing includes stringent tests for both categories. Vials or syringes of the product are all 100% visually inspected – either manually or using automated vision systems – against dark and light backgrounds to ensure no visible particulates are present. The product must be essentially free of visible particles to pass release (pharmacopeias state an injectable solution should not contain any visible particulates).  

For subvisible particles, specialized instruments like light obscuration particle counters or microscopes are used on a sample of the batch to count particles in size ranges like ≥10 µm and ≥25 µm, following standards such as USP <788>. The release specification will set an upper limit (e.g., not more than 6000 particles per container ≥10 µm, and not more than 600 ≥25 µm, per USP requirements for small-volume injectables). Ensuring compliance with these limits is critical: particles in an IV infusion can cause blood vessel blockage or immune reactions, especially aggregates of protein could be immunogenic. Therefore, particulate testing is a critical quality aspect for biologics.  

Analytical methods here are typically compendial – e.g., using a light obscuration method (also called liquid particle counting) and sometimes a microscopic method as a cross-check. Instruments like HIAC or light obscuration counters are commonly used to perform the subvisible count. If a batch has particle counts above the limit, it cannot be released, as that signals a possible issue in filtration or filling. By testing for visible and subvisible particles, manufacturers ensure the clarity and safety of the injectable biologic product. This testing also provides process feedback: for instance, a spike in subvisible particles might indicate a filter integrity issue or a solution stability problem that needs investigation. Thus, particulate analysis is both a release requirement and a quality monitoring tool. 

Extractable Volume and Dosage Unit Uniformity 

For biologics in liquid dosage forms (vials, prefilled syringes) or lyophilized cake to be reconstituted, it’s important to verify that each unit provides the correct dose to the patient. Extractable volume testing (a compendial test, described in USP and Ph. Eur.) is performed to ensure that one can withdraw at least the labeled volume from the container with a normal technique. For example, if a vial is labeled to contain 5 mL of solution, the extractable volume test will confirm that at least 5 mL (often a bit more to account for overfill) can be withdrawn – meaning the patient will get the full intended dose. This guards against short-filling during manufacturing. Typically, a sample of containers is tested by drawing out liquid until no more can be reasonably extracted, and the volume is measured. All tested units must meet the minimum volume requirement to pass.  

Uniformity of dosage units is another consideration: if the biologic is in a format where multiple doses or units are produced in a batch (for instance, a multi-dose vial or a lyophilized powder that’s filled by weight, or even capsules/tablets for oral biologic formulations), the content of active drug should be consistent across units. In classic pharmaceuticals, USP <905> tests for content uniformity or weight variation are used. In biologics, when dealing with liquids, dose uniformity is largely ensured by accurate fill volume and consistent concentration. If the product is a lyophilized cake, the fill of each vial (volume of liquid before drying or the weight of dried cake) is checked during manufacturing, and assay of active protein in a sample of units can confirm uniform content.  

Release specifications often include a requirement like “each vial contains 95–105% of the labeled protein content on average” with no individual unit far outside that range. This ensures patients receiving doses from different vials within a batch receive essentially the same amount of drug. To achieve this, sampling of units from throughout the filling run (beginning, middle, end) may be tested. Consistency here is both a quality and compliance issue – regulators expect that each dose delivered is within the labeled claim, and have set guidelines on how uniformity should be assessed. By including extractable volume and dose uniformity tests in release, manufacturers verify the proper dosing and administration characteristics of the product. In summary, these tests confirm that what’s on the label (in terms of dose or volume) is truly what the user can withdraw and administer, which is a fundamental aspect of product quality. 

Physicochemical Property Testing 

Biologic products have defined physicochemical characteristics that must remain consistent for the product to be considered in specification. Quality control laboratories perform a suite of simple but important tests to check these properties for each batch. Appearance is examined to ensure the solution or powder is as expected (for instance, a monoclonal antibody solution might need to be colorless to pale yellow, clear to slightly opalescent). Any cloudiness, unusual coloration, or precipitation would be cause for investigation. Color and clarity tests are usually done visually or with instruments like a turbidimeter for clarity.  

pH is measured with a calibrated pH meter to ensure it falls within the set range (e.g., pH 6.8–7.2) for the formulation – pH outside the range might indicate a buffer issue or could affect product stability or patient safety.  

Osmolality is measured (often by freezing point depression osmometer) especially for products that must be near physiological tonicity (around 300 mOsm/kg) if administered intravenously. An incorrect osmolality could cause pain or cell stress upon injection. Conductivity may be measured for certain products, particularly if ionic strength is critical (though for final biologic drug products, pH and osmolality are more common measures than raw conductivity).  

Other related tests can include extractable volume (discussed above), reconstitution time for lyophilized powders (how long it takes to dissolve in diluent), and residual moisture in lyophilized products (checked by techniques like Karl Fischer titration to ensure the cake is properly dried for stability).  

These physicochemical tests are generally based on compendial standards and are straightforward, but they serve to catch any gross abnormalities and to confirm consistency with the historical data. They are also part of demonstrating that the product was manufactured correctly – for example, if a batch’s pH is out of range, it might mean an error in buffer preparation. Including these tests in release criteria helps ensure product uniformity and acceptability. 

Best Practices for Setting Specifications, Sampling, and Data Review 

Designing an effective release testing program for biologics involves more than just running a set of assays. It requires strategic planning of specifications, sampling plans, and rigorous data review to ensure that the process is both scientifically sound and compliant with regulations. 

The release specifications (tests and their acceptance criteria) should be established based on a thorough understanding of the product and its clinical requirements. A best practice is to use a Quality by Design (QbD) approach during development to identify the product’s Critical Quality Attributes (CQAs) – select from them those that affect safety and efficacy – and then set specifications that will ensure those attributes remain within acceptable ranges. Each specification limit should ideally be justified by analytical characterization, process capability, stability studies, or clinical data (i.e. it’s clinically relevant or at least within manufacturing capability observed during development).  

Specification limits may start broad in early clinical phases and tighten later as more data on process capability and clinical tolerance become available. This phase-appropriate tightening is expected, but by the time of commercial release, specifications are usually fixed based on demonstreted manufacturing process consistency and clinical safety andefficacy considerations. Additionally, companies should avoid setting limitss unnecessarily tight (which can cause high rejection rates of good batches) or too lax (which could allow sub-par product through).  

Statistical analysis of manufacturing data (mean ± variation) and clinical batch data can help in choosing rational limits. Once set, specifications should be periodically revisited – for example, during annual product quality review – to see if they remain appropriate or could be refined. Overall, a best practice for specifications is that they truly ensure fitness-for-use: if a batch meets all limits, it should be safe and effective; if it fails a limit, that failure may correlate with a potential problem for the product’s performance. This rational approach ensures the relevance of release testing. 

Proper sampling is essential to gain an accurate picture of the whole batch. Biologic drug substance batches can be large volumes, and drug product batches can consist of thousands of vials – obviously, not every milliliter or vial can be tested, so representative sampling is key. A best practice is to follow written sampling procedures that define how and when samples are taken, ensuring they statistically represent the batch.  

For large bulk drug substance, the tank should be adequately mixed and sample aliquots collected from predefined locations. The sampling plan should also specify the number of units or volume needed for each test, based on compendial or regulatory standards (e.g., sterility test might require 20 units tested). Randomization and adequate sample size help ensure confidence that test results reflect the entire batch’s quality. FDA’s guidance and EU GMP both emphasize that sampling has to be representative, risk-based and properly documented. For example, if certain filling points have historically shown more variability, additional samples may be taken from those locations. Using composites for some assays can be effective (pooling multiple vials for an assay like protein content to get an average dose strength, though individual unit testing is needed for uniformity tests).  

In addition to end-product sampling, in-process sample testing (as mentioned earlier) is a best practice to catch issues early – while not part of final release criteria, it helps ensure the final product will likely pass. Manufacturers routinelytest intermediate pools (for purity, bioburden, etc.) and only allow material to proceed if those meet in-process limits; this reduces the chance of an OOS at final release. 

Conducting the assays is only one part of QC – equally important is the meticulous review of results and records before any batch release decision. Best practices here start with the analysts following written procedures and documenting all raw data (chromatograms, assay plates, calculations) in a complete, contemporaneous and traceable manner. Then, a second-person (peer or supervisor) review of the data should verify that the test was performed according to method, calculations are correct, instrument system suitability was within limits, and no anomalies were overlooked.  

Any Out-of-Specification (OOS) or atypical results must be investigated according to an SOP – one cannot ignore or arbitrarily invalidate failing results. All deviations or errors observed during testing (e.g., an analyst noticed a pipetting error and repeated the test) should be recorded and justified. The final decision on the batch should only occur after resolving these issues. A comprehensive review by the Quality Assurance in US or QP in EU will cover the batch production record and the QC results together, ensuring everything is complete: for example, checking that sterility tests were started and completed, that all assay results meet their acceptance criteria, that reference standards and reagents were within expiry, and that any incidents have appropriate conclusions.  

Modern best practices also emphasize data integrity and ALCOA principles—ensuring that records are attributable, legible, contemporaneous, original, and accurate. As part of data review, electronic records must be assessed to confirm they are complete and unaltered, audit trails should be examined for any unexpected or unauthorized activities, and any printed copies must be consistent with the corresponding electronic data.Trend analysis is another valuable practice: rather than just accepting results that pass, QC and QA should also look at trends over time (e.g., is the potency gradually decreasing batch by batch? Are certain impurities creeping up even if still within spec?). Identifying out-of-trend results can prompt proactive action before an actual OOS occurs.  

Finally, companies ensure that all original data (lab notebooks, electronic files) are retained in accordance with regulatory and internal requirements. This allows any future inquiries or audits to refer back to what exactly was done. Embracing digital systems can facilitate this review process, but the principle remains the same: no batch is released until a qualified reviewer confirms that all testing was properly conducted, all results meet criteria, and all paperwork is complete. At that point, the Quality Unit or QP can confidently authorized the batch for release. Implementing these thorough review practices not only ensures compliance (inspectors will check that companies follow their own review procedures) but also prevents batches with potential issues from slipping through. It is a crucial last step where “the dots are connected” between raw data and the final certification of the batch for use. 

Regulatory Requirements for GMP-Compliant Release Testing 

Release testing for biologics is not just a best practice – it is a strict regulatory requirement enforced by health authorities. Both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), along with other global regulators, have clear guidelines mandating that each batch of a drug (including biologics) must undergo specified quality control tests and meet pre-set criteria before it can be released for human use. Failing to comply can lead to batch rejection, regulatory enforcement actions, or product recalls. 

In the U.S., biologics are regulated under the Public Health Service Act and the Federal Food, Drug, and Cosmetic Act, with specific FDA regulations detailing quality requirements. 21 CFR 211 (the cGMP regulations for finished pharmaceuticals) requires that for each batch of drug product, there must be laboratory determination of satisfactory conformance to final specifications for identity, strength (potency), quality, and purity before release. In practice, this means a company cannot distribute a biologic lot until QC testing has confirmed it passes all release specifications, including the critical quality attributes discussed earlier. If the product is supposed to be sterile or pyrogen-free (which injectable biologics are), 21 CFR 211.165 additionally requires appropriate laboratory testing of each batch for sterility and absence of objectionable microbes and endotoxins.  

The FDA also has specific regulations in 21 CFR Part 610 for biologics: for example, 21 CFR 610.10 and 610.1.4 mandate that each lot must be tested for potency and identity with methods specific to the product. These regulations underscore that potency tests should be designed to measure the biological function of the product adequately, and an identity test on the final container of each lot is required to ensure correct labeling. There are also requirements for purity (freedom from certain contaminants) in these regulations, effectively aligning with the idea that the product should be safe and pure. All test methods used for release must themselves be validated for accuracy, sensitivity, specificity, and reproducibility (per 21 CFR 211.165(e)). Documentation is a huge part of compliance: FDA expects complete batch records, including all test results and any deviations, to be reviewed and approved by the Quality Unit. The Quality Unit (Quality Control/Quality Assurance) has the authority and responsibility to approve or reject any batch (21 CFR 211.22), and no batch can be released without their sign-off. In summary, U.S. regulations force a company to have a robust release testing program – every lot tested, no skipping tests, using validated methods – and to retain records demonstrating that each lot met all specifications prior to distribution. 

In the EU, the GMP and marketing authorization frameworks similarly insist on thorough batch testing and control. A cornerstone of EU compliance is the Qualified Person certification: under EU law, each batch of medicinal product must be certified by a Qualified Person before release for sale or supply. The QP is a highly trained individual who takes legal responsibility to ensure that a batch has been manufactured and tested in accordance with GMP and the marketing authorization dossier. This means that the QP must review the batch manufacturing records and all QC test results, ensuring that all specifications have been met and any deviations are resolved, then formally certify the batch. Only after QP certification can the batch be released to the market or for a clinical trial. EMA expects that the set of release tests and specifications for a biologic are agreed during the marketing authorization process (or in the IMP dossier for clinical trial material) – typically aligned with ICH Q6B guidelines.  

For biologics, this includes tests for identity, potency, purity, impurities, sterility, endotoxins, etc., just as in the US. The EMA (and other agencies in the EU) also require that test methods be validated per ICH and Pharmacopeial standards, and that laboratories operate under GMP (meaning controlled procedures, data integrity, etc.). In certain cases, especially for vaccines or some blood products, EU authorities themselves conduct Official Control Authority Batch Release (OCABR) before the product can be used. But for most biologics, it is the manufacturer’s own testing plus the QP oversight that suffices. It is worth noting that batch release in the EU is very formally regulated: Annex 16 of EU GMP provides detailed guidance on QP batch certification and circumstances under which a QP can certify a batch (for example, if certain testing is pending but justified). The take-home message is that in Europe, no batch reaches patients without a QP’s signature, which in turn is only possible if all required release tests are passed and all production and quality records are in order. This system strongly ties release testing to regulatory compliance. 

Common Pitfalls in Biologics Release Testing and How to Avoid Them 

Even with robust systems in place, biologics release testing is a complex undertaking and certain pitfalls occur across the industry. Awareness of these common pitfalls and proactively addressing them is an important part of continuous improvement in Quality Control (QC) and Quality Assurance (QA) for biologics. 

Tab. 1. Examples of accidents in biological drug release testing. 

Humans are a major source of laboratory errors, whether in performing tests, recording data, or calculating results. Common mistakes include pipetting errors, mislabeling samples, transcription mistakes, or using incorrect instrument settings. In a pharmaceutical QC lab, such errors can lead not only to failing results but also to data integrity issues if not caught. The root causes often trace back to inadequate training, rushed work, or complacency. By understanding that the most common source of QC errors is human error, managers can put in place fail-safes – like templates, checklists, and peer reviews – specifically to intercept those errors. Lab management should promote an environment where analysts do not feel undue time pressure that might cause them to cut corners. 

A common pitfall is not controlling the cleanroom or laminar flow hood environment during sterility tests. If a lab has inadequate aseptic technique, a sterile batch could fail due to a lab-introduced contaminant (which still means the batch can’t be released). Or an endotoxin test could fail because of technician error (say, interfering substances not dealt with, or simple calculation error in dilution). To avoid these, labs must maintain high aseptic standards: perform sterility tests in certified cleanrooms or isolators, use positive controls to ensure the media and method can detect organisms, and have alert/action levels for environmental monitoring of the micro lab. Another pitfall is slow turnaround for tests like sterility (14-day test) or mycoplasma (traditionally 28 days by culture). These can delay release. Many companies mitigate this by adopting rapid methods (e.g., rapid qPCR-based mycoplasma tests that can give results in days, or rapid sterility tests) where regulatory permitted, or by carefully scheduling manufacturing so that these tests start as early as possible. Diligence in the microbiology lab prevents both false failures and false passes (ensuring any contamination would be caught). 

In the modern QC lab, a significant pitfall is poor data integrity – examples include not recording an event, altering data to pass a test, or using “scratch paper” instead of controlled worksheets. Such practices are strictly forbidden by GMP, but if a lab’s culture is not strong or if oversight is weak, they can occur. This could lead to unreliable results or regulatory findings. To avoid data integrity issues, labs must enforce ALCOA principles: every result must be Attributable (who performed it), Legible, Contemporaneous (recorded at the time of activity), Original, and Accurate. Use of electronic systems with audit trails is encouraged because they automatically capture a lot of this information. 

One pitfall is relying on assays that are not fully validated or not strictly following the validated protocol. Biologic assays (e.g., bioassays for potency) can be inherently variable; if the method isn’t well optimized and validated, it may produce spurious Out-of-Specification results that trigger investigations even when the batch is actually fine. Conversely, a poorly designed method might pass a batch that has a real problem. To avoid this, companies must rigorously validate each release test method for accuracy, precision, specificity, etc., under GMP conditions. After validation, it’s a best practice to monitor ongoing assay performance – for example, track how often system suitability failures or OOS results occur, track the reference standard trends, and look for any decline in assay precision. 

Conclusion 

Release testing of biologics is built around verifying these critical quality attributes: that the correct product has been made (identity), that it is pure, active, and safe for use, and that it conforms to various quality measures set during development. If any one of these dimensions is out of limits, the batch cannot be released. By enforcing stringent criteria on identity, purity, potency, sterility, and other quality measures, manufacturers uphold the high standards necessary for biologics, which by their nature are complex and sensitive medicinal products. 

While biologics release testing is challenging, understanding these common pitfalls allows companies to put targeted controls and cultural practices in place to prevent them. Strong training and human factors management address many lab errors. A rigorous quality system with proper investigations and data oversight prevents procedural mistakes. An emphasis on building quality in upstream reduces the burden on release tests. By learning from industry pitfalls – often documented in regulatory warning letters and case studies – manufacturers of biologics can continuously refine their release testing processes. The result is a more reliable supply of high-quality biologic medicines, released on time and in full compliance with all GMP and regulatory requirements.

FAQ

Prepared by:

Amanda Jabłońska

Physicochemical and Biological Testing Division Manager

a.jablonska@mabion.eu

Amanda Jabłońska

Physicochemical and Biological Testing Division Manager

Amanda leads the Quality Control team ensuring products meet all quality, safety, and regulatory standards. She oversees daily operations, managing staff, developing procedures, handling investigations (OOS, deviations), and driving continuous improvement for accurate, reliable results in a high-stakes environment. Amanda Jabłońska develops and administers budgets, schedules and performance requirements.

Jakub Knurek

Marketing Specialist

j.knurek@mabion.eu

Jakub Knurek

Marketing Specialist

Jakub Knurek is a marketing and business development expert specializing in CDMO operations with scientific and biopharmaceutical background. During the COVID-19 pandemic, he contributed to the development of the Novavax protein vaccine. As a side project, he runs his own pharma company.

As the author of numerous articles, he is recognized as an important voice of the younger generation of scientists. He is a member of Mabion’s representation at industry trade shows, including BIO International Convention 2025 in Boston, 2nd Global Biologics India 2025 in Hydrabad, CPHI 2024 in Milan, CPHI 2023 in Barcelona, Life Sciences Baltics 2023 in Vilnius. He actively participates in academic, business and industry discussions, such as the “Building the Future Pharma Workforce” panel at CPHI Milan 2024.

References

1. European Medicines Agency. ICH Q5C Quality of biotechnological products: Stability testing of biotechnological/biological products. 1996. 
2. European Medicines Agency. ICH Q6B Specifications: test procedures and acceptance criteria for biotechnological/biological products. 1999. 
3. European Medicines Agency. ICH Q4B Evaluation and recommendation of pharmacopoeial texts for use in the ICH regions. 2024. 
4. European Medicines Agency. Guideline on real-time release testing. 2012. 
5. European Commission. EU GMP Annex 16: Certification by a Qualified Person and Batch Release. 2015. 
6. US Pharmacopeia <71> Sterility Testing. 
7. US Pharmacopeia <85> Bacterial Endotoxins. 
8. US Pharmacopeia <788>  Particulate Contamination. 
9. US Pharmacopeia <905>  Uniformity of Dosage Units. 
10. U.S. Food and Drug Administration. Q7A Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients. 2001. 
11. U.S. Food and Drug Administration. Current Good Manufacturing Practice (CGMP) Regulations. 2025. 
12. Bracewell DG, Francis R, Smales CM. The future of host cell protein (HCP) identification during process development and manufacturing linked to a risk-based management for their control. Biotechnol Bioeng. 2015; 112: 1727-1737. 
13. Wolf K. Attributable Data Integrity in Modern Biopharma Using ALCOA Principles. Outsourced Pharma, 2022. 
14. van Moll C, Egberts T, Wagner C, Zwaan L, Ten Berg M. The Nature, Causes, and Clinical Impact of Errors in the Clinical Laboratory Testing Process Leading to Diagnostic Error: A Voluntary Incident Report Analysis. J Patient Saf. 2023; 19: 573-579.