[Lingkang Times CDMO] Application of QbD in the development of protein vaccine prescriptions
- Challenges in vaccine prescription development
Vaccine formulation development faces many challenges, such as:
The concentration of a single dose of vaccine may be as low as single digit micrograms. In contrast, the stock solution usually has a higher concentration. It is necessary to ensure the stability of both the stock solution and the preparation;
For polyvalent vaccines containing several active vaccine ingredients, formulations need to be developed that stabilize all active ingredients;
Most protein vaccines require the addition of adjuvants, such as aluminum salts, MF59, AS01, CpG, etc., to enhance the immune response, which increases the complexity of vaccine prescription.
QbD as a guiding principle for vaccine formulation development. According to ICH Q8 R2, QbD is "a systematic research and development approach that starts with pre-set goals, is based on reliable science and quality risk management, and emphasizes the understanding of the target product and production process and the control of the process." Recipe development refers to the QbD principle and is applied to the entire process from R&D to production. QbD-based formulation development usually includes the following steps: (1) Formulation of the Quality Target Product Profile (QTTP); (2) Identify product CQAs (Critical Quality Attributes) based on the required quality profile, and list CQAs that may be affected by the formulation formulation; (3) Conduct pre-formulation studies and strong degradation studies to characterize the molecular degradation pathways, and initially screen degradation formulation factors and adjuvant-protein interactions; (4) Update CQA through pre-formulation studies and assess the (potential) impact of quality attributes on drug safety and effectiveness; (5) Develop formulation formulations through screening studies; (6) Develop and control the production process according to product CQA, and formulate production control strategies.
Pre-formulation studies: Also called pre-formulation studies, pre-formulation studies provide a scientific basis for prescription development. The physicochemical properties of all antigenic components and adjuvants are studied with the aim of characterizing their impact and the impact of their combination on product CQAs. Preformulation research purposes include, but are not limited to: (1) Development of analytical methods to support antigen structure elucidation and future formulation development; (2) Identification of biomolecule characteristics relevant to antigen safety and efficacy; (3) Identification of antigen degradation pathways and sensitivity to associated stress conditions, such as thermal and shear stress, pH, oxidation, freeze-thaw, etc.; (4) Screening studies are used to initially identify formulation factors (pH, buffers, excipients) and initially assess compatibility with other formulation ingredients (e.g., container closure systems, adjuvants). Preformulation studies provide essential information for identifying protein characteristics, including degradation pathways and their probability of occurrence under common stress conditions. The list of product quality attributes should be updated through preformulation studies to serve as a reference for subsequent formulation development.
Formulary development and optimization 4.1 Determining the appropriate dosage form Based on the complexity of the structure of protein antigens, the simultaneous presence of multiple antigens, and the presence of adjuvants, determining the appropriate dosage form of protein vaccines is a challenging task. Maintenance of the native protein structure is critical to ensuring product quality and ensuring product stability during the shelf life. When designing the dosage form of a new vaccine, various factors must be considered (usually described in QTPP), such as: (1) Required administration method: parenteral administration, transdermal administration, etc.; (2) Required product form: liquid, lyophilized powder; (3) Type of adjuvant system: such as aluminum salt, emulsion, etc.; (4) Dosage: such as protein/adjuvant ratio, dose volume; (5) Container closure system: such as vials, prefilled needle syringes, etc.; (6) Logistics: transportation, storage temperature, required shelf life, etc. Liquid formulations stored in vials or prefilled syringes at 2 to 8°C are often preferred for commercialization as it simplifies the production process and product logistics, as well as vaccine administration to vaccine recipients. 4.2 Screening of formulation components Formulation development begins by screening the most appropriate formulation factors (such as pH, buffers, other excipients, containers/closure systems), and in the subsequent process confirms the concentration of excipients and the range of each factor in the formulation, and finally confirms the formulation. Throughout the development studies, the compatibility of all ingredients in the final drug product and the impact on the manufacturing process should also be considered. (1) pH and buffer pH, buffer type, and buffer concentration are all factors that need to be considered during the prescription development stage. Since there may be many combinations of buffer systems and pH to be evaluated, high-throughput screening can be used to evaluate different pH, buffer types and concentrations with limited materials and time, and screen out the most suitable product composition. (2) Excipients, also known as excipients, the formulation composition of the vaccine should be as simple as possible; if it is necessary to stabilize the antigen or significantly improve vaccine delivery or production, excipients other than buffers and adjuvants can be added. The purpose of excipients is to improve the physical stability of the antigen and also to reduce the interaction of the antigen with container or process-related contact materials. Surfactants (e.g., polysorbates), amino acids, and sugars (e.g., sucrose, trehalose) can be used to reduce these interactions. Other excipients are often used to increase oxidative stability (e.g., methionine, ascorbic acid, EDTA) or to ensure a sterile environment in the presence of multiple doses. During the screening process, various candidate formulations should be evaluated using different stress conditions to predict stability under production, shipping, or live storage conditions. (3) Container closure systems The most common container closure systems used for parenteral vaccine products are vials or prefilled syringes, and compatibility studies should be conducted during the development process. (4) Adjuvant An adjuvant is a pharmacological substance that can enhance or modulate the vaccinee's immune response to an antigen and is usually an integral part of a vaccine. Currently, the most commonly used adjuvants in marketed vaccines are aluminum adjuvants and oil-in-water emulsions (such as MF59). In addition, there are a large number of other adjuvants used in recently marketed vaccines and vaccines under development. One example is the AS01 adjuvant system, a liposome-based system containing two immunostimulants, 3-O-desacetyl-40 monophosphate lipid A (MPL) and the saponin QS-21, used in conjunction with the shingles vaccine Shingrix. When undertaking formulation development, compatibility of the adjuvant with all formulation ingredients should be included as part of the development. Some adjuvants interact with antigens. Adjuvants such as aluminum usually adsorb antigen, and the percentage of antigen adsorbed is an important quality attribute during formulation development. In contrast, other adjuvants generally do not interact with antigens, e.g., AS01, MF59. Because this knowledge is critical to defining and controlling all CQAs for vaccine products, interaction studies should begin during preformulation studies. 4.3 Prescription Robustness Study After determining the composition of the target product, it is necessary to confirm the range of each component in the prescription through multi-variable research, usually DoE research, to prove that when the content of each component in the prescription fluctuates within a certain range, it can also meet production, transportation and long-term storage. 4.4 Compatibility study of freeze-dried vaccines and reconstitution solvents Before vaccination, freeze-dried vaccine products need to be reconstituted with reconstitution solvents. The reconstitution solvent may be water or an adjuvant system. When using adjuvants for reconstitution, compatibility should be assessed theoretically and experimentally. The figure below shows the compatibility assessment of lyophilized vaccines with respect to relevant quality attributes. This study compared vaccines reconstituted with water and vaccines reconstituted with adjuvant, with reconstitution time as point 0 and analyzed after 4 hours at 25°C. The experimental results obtained support the compatibility of this vaccine product.
Summary QbD, as a basic principle, is actually applied in all aspects of drug research and development. For vaccine prescription development, it is necessary to clarify the CQAs at each development stage and the relationship between CQAs and safety and effectiveness, in order to more accurately understand the development goals. This also requires the joint efforts of the formulation department and clinical and analytical colleagues. References [1] QbD approach to formulation development for protein-based vaccines. Practical Aspects of Vaccine Development. 2022; 137-156. [2] Formulation development and comparability studies with an aluminum-salt adjuvanted SARS-CoV-2 Spike ferritin nanoparticle vaccine antigen produced from two different cell lines. bioRxiv. 2023: doi: 10.1101/2023.04.03.535447. Preprint