This question and answer page is developed and maintained by the CHMP Biologics Working Party (BWP) and provides agreed positions by the Biologics Working Party position on issues that can be subject to different interpretation or require clarification, typically arising from discussions or correspondence during assessment procedures of biological human medicinal products.

In order to obtain information on a topic, please click on the topics/questions. Please note that this page has been produced to provide transparency and additional information, and should be read in conjunction with the European Pharmacopoeia, CHMP guidelines on quality and other guidance documents.

Reprocessing (3.2.S.2.2, 3.2.P.3.3)

If reprocessing is not mentioned in the dossier, it is assumed it is not applied for. However, Applicants are encouraged to explicitly state in section 3.2.S.2.2 or 3.2.P.3.3 either

  • at which step(s) reprocessing may be performed. This should be supported by appropriate process validation data,
  • that there is no reprocessing at any step in the manufacturing process. Reprocessing may be added post-approval through a variation procedure.

Raw materials and media components (3.2.S.2.3)

Where media are sourced from an external supplier and quantitative details of the media components are not available, a qualitative composition of media components is sufficient. In such cases, a confirmation that an agreement is in place with the supplier to notify the MAH in case of changes to the medium should be included in section 3.2.S.2.3.

Method identification numbers (3.2.S.4.1, 3.2.P.5.1)

Identifiers for in-house analytical methods should be included in the specification table. The method descriptions and the method validation summaries should be updated to include in-house method identification numbers for the non-compendial methods. The information is required in order to provide a clear link between the release and stability specifications and the descriptions and validations of analytical procedures used for testing.

It is acceptable not to routinely test for process related impurities if consistent elimination has been demonstrated by validation studies and sufficient batch data is available. Preferably, the reduction of impurities is studied in process evaluation studies by spiking experiments or demonstration of robust reduction capacity in the relevant manufacturing steps. It should be justified that the relevant manufacturing step is capable of removing impurities to a sufficient level when run under worst-case conditions.

This is not applicable to impurities with a high safety risk and proteinaceous impurities (e.g. HCPs), which normally require routine control.

Host cell proteins testing, drug substance specification (3.2.S.3.2, 3.2.S.4.1, 3.2.S.4.5)

Host cell protein (HCP) testing is typically part of the drug substance specification, as appropriate. Routine control of HCP is deemed important as this may be a relevant safety parameter, i.e. it is not considered appropriate omit HCP testing based on process validation studies only. Until adequate manufacturing experience together with extensive batch data demonstrating consistent low levels of HCP is available, a release specification should be included in S.4.1 for HCP with a clinically qualified upper limit justified in S.4.5. HCP may be tested on an intermediate and reported as a critical in-process control, if the following is fulfilled:

  • the Applicant has extensive knowledge and control of the manufacturing process (critical process parameters affecting HCP levels should be identified),
  • scale-down process qualification studies followed by at-scale process validation and batch data results demonstrate HCP clearance,
  • it is confirmed that exceeding the acceptance criterion for the IPC will lead to batch rejection,
  • the proposed IPC limit is clinically qualified.
  • HCP testing will be part of comparability assessments of future process changes where relevant.

Regardless whether HCP is routine tested as an IPC or as a release test, the HCP assay should be well described and validated and acceptance limits should be justified; all documentation should be included in the CTD (either in section S.4 or section S.2.4). The suitability of the detecting polyclonal antibody (coverage of HCP representative of the process, as mentioned in Ph.Eur.2.6.34) should be assessed. In addition, other recommendations from Ph. Eu 2.6.34, should also be addressed by the Applicant.

Biosimilar medicinal products: characterization, side-by-side comparison, specification, biosimilarity, analytical comparability (3.2.S, 3.2.S.3.1, 3.2.S.4.1, 3.2.P.5.1, 3.2.R)

Since for most biosimilar applications only a limited number of clinical batches are used, it is not possible to set and clinically justify specification limits solely based on clinical batches of the proposed biosimilar. Therefore, characterisation results of the reference product (as obtained by the applicant using their own qualified/validated test methods intended for the proposed biosimilar) may be used for clinical justification of the specification limits of the proposed biosimilar. Result ranges obtained for marketed reference product batches can be assumed to represent a clinically qualified range for the respective quality parameters.

As regards process-related impurities (e.g. host cell DNA and HCP), since processes are as such not expected to be similar, in most cases the applicant cannot refer to characterisation results from the reference product to justify the specification limits and the control strategy for process-related impurities should be established based on the manufacturing experience for the biosimilar.

In order to demonstrate biosimilarity/analytical comparability, it is not generally required to perform a side by side comparison (i.e. testing data from a single analytical experiment/run). A side by side comparison is important only for those tests with high intrinsic between-run variability, in order to minimize such variability. In other cases, data from different experiments are acceptable.

Where an Applicant can demonstrate that a monoclonal antibody (mAb) binds to a soluble target which has no transmembrane variant or is not known to be cell/membrane-associated, then characterisation testing for Fc functionality assays (ADCC/CDC/ADCP) can be omitted. In such cases, Fc functionality testing is not required to demonstrate comparability after manufacturing changes or for biosimilarity testing.

The evaluation of ADCC activity should not be based solely on reporter gene assays. A “classical” ADCC assay approach using a two cell format, i.e. target cells plus effector cells (such as NK cells or PBMCs), is required for demonstrating biosimilarity of mAbs with ADCC function.

Where binding to Fc?RIIa is a relevant quality parameter, the biosimilarity exercise should include binding to both polymorphic receptor variants 131H and 131R.

Where binding to Fc?RIIIa is a relevant quality parameter, the biosimilarity exercise should include binding to both polymorphic receptor variants 158V and 158F.

Monoclonal antibodies specification, ADCC activity (3.2.S.4.1, 3.2.P.5.1)

For mAbs with Antibody Dependent Cell-mediated Cytotoxicity (ADCC) activity, it is sufficient to only have one parameter in the specifications that verifies this function. Possible tests include a cellular ADCC assay, Fc?RIIIa binding, or relevant testing of the glycoprofile; the two latter parameters being more reliable, one of them is to be preferred to the ADCC assay depending on their correlation to ADCC assay. Indeed, where control of effector function is based on testing of the Fc?RIIIa binding or the glycoprofile, a correlation should be demonstrated between ADCC and the proposed Fc?RIIIa binding assay or the glycosylation parameters. Depending on the specific molecule, control may be based on afucosylation (G0+G1+G2), high mannose forms (e.g. M5+M6+M7+M8), total afucosylation (G0+G1+G2+high mannose forms) or a combination of several of these parameters, whatever is most relevant as indicator for ADCC.

Polysorbate testing in finished product specification (3.2.P.5)

Where polysorbate is included in the finished product formulation and it has been demonstrated in formulation development studies that polysorbate is a relevant component to prevent particle formation, or that particle formation is linked to polysorbate degradation, a test for polysorbate should be included not only in the routine release but also in the stability specifications. Alternatively, sufficient pharmaceutical/formulation development data to demonstrate that polysorbate levels remain stable over the proposed shelf life of the finished product, could be provided to substantiate omission of such a test during stability studies.

Low Endotoxin Recovery, Endotoxin masking effect (3.2.P.5.3)

For product formulations that contain a combination of a surfactant (e.g. polysorbate) and a chelator (e.g. EDTA, citrate, phosphate, histidine), studies investigating Low Endotoxin Recovery (LER) should be submitted in the MAA dossier. For that purpose, spike/ hold studies should be performed on undiluted samples. Based on current scientific state of the art, a minimum of four time-points should be conducted to ensure valid and accurate results. Two consecutive data points falling below 50% recovery (lower compendial limit), should be considered as LER.

In case that LER is detected, the Applicant should propose an adequate mitigation strategy (e.g. the compendial method should be optimized or an alternative method developed). For LER exhibiting products, it is strongly recommended to set the finished product specification limit for bacterial endotoxin as low as reasonably achievable, according to actual manufacturer`s data. This approach would help to ensure that a larger safety margin is built into the finished product endotoxin specification limit. The recommended location of the LER studies is CTD section 3.2.P.5.3 (method validation).

Non-novel excipients manufactured using recombinant technology (3.2.P.4, 3.2.A.3)

For excipients manufactured using recombinant technology, that are not considered novel, the submission of certain manufacturing and control information is required to ensure consistent quality. In addition to the CTD module 3.2.P.4 “Control of excipients” (specifications, analytical methods, method validation and justification of specifications), applicants should also provide detailed information on the following aspects: manufacturers, description of the manufacturing process, control of materials, process validation, characterization, impurity testing, stability and viral safety assessment (including proof of process capability to remove/clear relevant model viruses). Information should be presented in section 3.2.A.3 Excipients.

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