Function

As a product, the TB vaccine candidate progresses from a design on paper and prototypes in a laboratory into a commercial product in a vial. The aim of this function is to define how the vaccine should be characterised at each stage, and to define the criteria for quality. There is an increased level of control on the specifications of the vaccine candidate as it progresses through the stages, to become a safe and effective product against TB. This includes specifications for the drug substance (the biologically active ingredients), the excipients, and the contaminants that are included in the final drug product, together with the assays to accurately monitor these quality attributes.

Stage 
A
Perform discovery, safety, immunogenicity and efficacy evaluation in initial animal model
Gate 
A
Progress to proof of concept (POC) studies in animals
Main Activities
  • Screen and select antigen(s), adjuvants, other excipients and delivery system
  • Characterise vaccine candidate. In particular, demonstrate antigen expression and purity (e.g. proteins)
CRITERIA REQUIRED
  • Antigens, adjuvants, other excipients, delivery system selected
  • Characterisation tests defined and characteristics of the vaccine candidate documented
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Guidance

Discovery is the stage where the technology and design of TB vaccine candidates are made, and when TB antigens, adjuvants, delivery system are screened based on expression (yield) and immune response in animals.

Key for the characterisation of the drug substance are assays to measure its identity, potency, purity, and stability. These assays require specific development and depend on the type of vaccine, for example a TB subunit vaccine will require a different assay for identity than a recombinant BCG. Identification and expression of the substance often includes gel electrophoresis, western-blot, or Enzyme Linked Immunosorbent Assay (ELISA) for a protein, and Polymerase Chain Reaction (PCR) for recombinant DNA. Potency could be bacterial viability (colony-forming unit) for a recombinant BCG, coupled to a marker assay for an immunological relevant effect representing protection. For a subunit vaccine it could be the concentration linked to a protective immunological effect, and for a viral vectored vaccine it would be titre linked to a similar output. For TB vaccines, T-cell epitopes and associated responses can be evaluated as markers for immunogenicity and potency. Examples include- antigenspecific stimulation of Interferon gamma production, measured by ELISpot, other cytokines, specific T-cell populations such as polyfunctional T-cells. Purity assays measure contaminants that originate from the expression system and culture medium used, such as host cell protein, host cell DNA, endotoxin or serum components, or from the process conditions used, e.g. detergents (Triton) or DNAse (benzonase).

The characteristics of modified TB as live attenuated TB vaccine have been published in the ‘Geneva Consensus’ publications (Geneva consensus and 2nd Geneva consensus).

The following guidelines on quality control of vaccine development provide further information: ICH Q8 Pharmaceutical Development, August 2009 (ICH Q8), ICH Q11 Development and Manufacture of Drug Substances (chemical entities and biotechnological/biological entities), May 2012  (ICH Q11) and ICH Q2, Validation of Analytical Procedures: Text and Methodology, nov 2005 (ICH Q2).

Stage 
B
Perform POC studies in animals
Gate 
B
Progress to Pre-Clinical
Main Activities
  • Document vaccine product stability
  • Select assays to monitor product quality, including an assay for potency
CRITERIA REQUIRED
  • Initial product stability defined
  • Feasible assays for product quality attributes selected, including for potency
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Guidance

There is further characterisation of the vaccine substance / product for its identity, purity and potency. Evaluation of stability under the expected storage conditions must be performed at this stage, and this becomes a criterion for selection.

There is no correlate of protection for TB vaccines. This presents a challenge to determine the potency of vaccine candidate. Beside its concentration, several different marker assays are used as indicated above. The recently developed mycobacterial growth inhibition assay (MGIA) could be considered as a surrogate measure of a protective immune response.

The assays required for the testing of Critical Quality Attributes (CQA), the most relevant criteria for product quality with respect to safety and efficacy, are selected.

Stage 
C
Perform Pre-Clinical evaluations
Gate 
C
Progress to preparation for Phase 1, First-In-Human
Main Activities
  • Optimise and finalise vaccine composition and route of administration
  • Develop release assays and stability tests
  • Prepare batch release
CRITERIA REQUIRED
  • Vaccine characteristics critical for vaccine immunogenicity (e.g., antigen sequence, adjuvant, delivery system, route of administration) finalised
  • Target Bill of Testing (BOT) defined with target specifications for final product, drug substance (potency), excipients, impurity profile and product composition
  • Quality control (QC) tests selected and their feasibility demonstrated, incl. for potency/ relevant biological activity, identity, purity, and stability
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Guidance

The assays selected for quality control and characterisation are developed, together with target specifications, for identity, potency, purity etc. These quality parameters of the substance and the product are referred as Bill of Testing (BoT), or Quality Target Product Profile (QTPP).

Note: the raw materials used for production of the substance and the product should be checked before being used in the lab. This quality control procedure is mandatory for current Good Manufacturing Practice (cGMP) operations. Certificates of Analysis of raw material must be collected and assays with target specifications selected for release.

Stage 
D
Perform GMP and toxicity studies and prepare Clinical Trial Application
Gate 
D
Progress to First-In-Human/Phase1
Main Activities
  • Release batch for the toxicology studies
  • Qualify assays related to critical quality attributes (CQA, product) and critical process parameters (CPP)
  • Release seed lots and banks
  • Release drug substance (DS) and drug product (DP) for FIH/Phase 1
  • Optimise buffer formulation and generate stability data on DS and DP
CRITERIA REQUIRED
  • Batch for toxicology studies released
  • Critical assays qualified
  • Seed lots and banks released
  • Clinical DS and DP meet specifications and are released. Equivalence to batch used for toxicology confirmed
  • Stability data on formulated vaccine sufficient to support clinical trial
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Guidance

In preparation for manufacturing of GMP material, the assays used for quality control and the Critical Process Parameters (CPP) must be qualified. The list of parameters that needs to be tested to release a product batch is confirmed and recorded in the BoT. Beyond this point the Product Specifications cannot be changed outside the original ranges without having major consequences (except for the excipients).

The material used for the toxicity study is produced according to cGMP or equivalent to GMP and must be characterised and released accordingly. The Phase I material is also produced and released.

Stage 
E
Perform, First-in-human/Ph1
Gate 
E
Progress to Ph2
Main Activities
  • Fine tune (if needed) quality control (QC) assays
  • Qualify and/or validate QC procedures
  • Characterise newly produced drug substance (DS) and drug product (DP)
  • Perform stability studies
CRITERIA REQUIRED
  • QC assays refined (if needed)
  • Plan to ensure validation of QC procedures established
  • DP and DS pass the tentative product specifications recorded in the Target Bill of Testing (BOT); impact of changes and deviations on DS and DP are documented
  • Stability data sufficient to support clinical trial
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Guidance

During Phase 1, the assays for CQA continue their qualification, progressing to validation. The assays used for product characterisation could be slightly modified, to improve the sensitivity or accuracy of the test. This should not change the qualification or later validation status of the assays. Up to this point, the product reference would be from well described R&D production runs, and used to standardise assays. It could now be replaced by a GMP compliant reference.  
The assays are used to release any new GMP material produced, or document changes in the drug product (within certain limits), and in the continuing stability studies.

Stage 
F
Perform Ph2 (including Pre-POC) studies
Gate 
F
Progress to Ph2b Efficacy
Main Activities
  • As in previous Stage
CRITERIA REQUIRED
  • As in previous Stage
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Guidance

As previous stage

Stage 
G
Perform Ph2b Efficacy
Gate 
G
Progress to Ph3
Main Activities
  • Confirm specifications of final formulation
  • Compare drug product (DP) used in different studies, as relevant
  • Continue stability testing
  • Define and validate final Quality Control (QC) analytical methods, for the release of batches and final product
CRITERIA REQUIRED
  • Specifications for product from consistency runs in finalised Target Bill of Testing (BOT) are defined
  • Comparability of products used in different clinical studies is available
  • Stability acceptable
  • QC assays are validated
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Guidance

At the end of this stage, the assays used for quality control should be validated, with final specifications, for the release of Phase 3 GMP material and of the consistency lots.

Stage 
H
Perform Ph3
Gate 
H
Progress to licensure
Main Activities
  • Release Good Manufacturing Practices (GMP) Phase 3 and consistency batches
  • Evaluate stability data against TPP
CRITERIA REQUIRED
  • No major out-of-specs for the product as listed in the Bill of Testing (BOT). Consistency of batches documented
  • Stability studies completed and data support TPP
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Guidance

Stability data have been generated from the first R&D lot and for each manufacturing lot. These stability data should be compared, as part of the characterisation of the product.