Abstract
Biologics are licensed under Section 351 of the Public Health Service (PHS) Act. The PHS Act requires that biological products be safe, pure, and potent, and manufactured in facilities designed to ensure the continued safety, purity and potency of such products. Under the Federal Food, Drug, and Cosmetic Act (FD&C Act) “biological products” are also drugs. A subset of biologics, specified biologics (21 CFR 601.2(a)(3) & (4)), are regulated by the Center of Drug Evaluation and Research (CDER). The Biotechnology Manufacturing Team (BMT) in the Division of Manufacturing and Product Quality in CDER’s Office of Compliance evaluates the Chemistry, Manufacturing and Controls (CMC) section of Biologics License Applications (BLAs) for monoclonal antibody and therapeutic recombinant DNA-derived products (therapeutic biological proteins) and conducts pre-license/pre-approval inspections of establishments engaged in their manufacture. CMC review responsibilities handled by BMT include assessment of microbial controls of the drug substance manufacturing process. This review includes elements such as monitoring of bioburden and bacterial endotoxins during cell culture or fermentation, harvest, purification, formulation and bulk filling operations. The sterility assurance information for the aseptic fill manufacturing process and microbiological quality attributes are assessed for the drug product. BMT leads the pre-approval/pre-license inspections of establishments involved in the production of biologics, which must meet CGMP requirements (21 CFR 601.2(d)). Cross-contamination risks are also assessed during inspections. This article discusses the elements evaluated during the CMC microbiology review and during inspections and presents recent review deficiencies and inspectional observations.
Introduction
In recent years, there has been an increase in the pace of the discovery, clinical testing and requests for US Food and Drug Administration (FDA) approval to license novel biological drugs for marketing. CDER is responsible for reviewing BLAs for therapeutic DNA plasmid products, synthetic peptide products of 40 or fewer amino acids, monoclonal antibody products for in vivo use and therapeutic recombinant DNA-derived products (21 CFR 601.2 [1]). The regulatory authority of therapeutic biological proteins (TBPs) was transferred from the Center for Biologics Evaluation and Research to CDER in 2003 [2]. This article discusses the review of microbiological aspects of the CMC section of a BLA for TBPs and the conduct of inspections of manufacturing and testing sites required for approval. Some common review issues and recent inspectional observations are presented.
Regulatory Framework
Section 351 (a)(2)(B) of the PHS Act [3] states that a BLA shall be approved only if it has been demonstrated that the biological product is safe, pure and potent. The manufacturing, processing, packaging and storage facilities must meet standards designed to assure the manufacture of a safe, pure and potent product.
Several differences exist for the regulation of pharmaceutical small molecule products and biological products. While both biologics and small molecules are regulated under provisions of the FD&C Act [4], only biologics are licensed under Section 351 of the PHS Act. Investigational drug applications for both are submitted in accordance with 21 CFR 312 to permit their use in human clinical trials. New drug applications are required prior to approval of small molecule drugs while BLAs are required for biologics. The approval of the latter is granted by the issuance of a biologics license. The license can be suspended or revoked (21 CFR 601.5 and 601.6). The application (or license) may not be filed if all required information and data have not been provided to the Agency. Furthermore, 21 CFR 600.21 provides the authority to inspect an establishment listed in a pending BLA while it is in operation and manufacturing the product for which the BLA has been submitted. The same chapter authorizes the Agency to inspect each licensed establishment at least once every two years.
Manufacturing Process
Traditional drug products, generally referred to as small molecule drugs, usually consist of pure chemical substances that are easily analyzed and identified after manufacture using relatively simple production processes. However, TBPs consist of large, complex molecules with secondary and tertiary structures that cannot be easily characterized. They are produced by living cells and as a result, variable systems. Large molecules are isolated using extensive purification processes. Finished products are manufactured using aseptic processing methods due to their heat sensitivity (protein denaturation) and complex properties. Product quality is extremely sensitive and variable to process changes. Changes in the manufacturing process, equipment or facilities can result in changes in the biological product itself. As a result, additional clinical studies may be required in some cases in order to demonstrate the product’s safety, purity and potency. Process control and consistency is of the utmost importance for the manufacture of a biologic with the expected quality attributes.
Biotechnology Manufacturing Team (BMT)
BMT is in CDER’s Office of Compliance, Division of Manufacturing and Product Quality. Our public health mission is to ensure that safe, pure and potent therapeutic biological products are available to the public. This is accomplished through reviews of the CMC section of submissions, pre-license and pre-approval establishment inspections, and meetings with industry.
BMT evaluates the CMC section of BLAs and supplements from the microbial control, sterility assurance and product quality microbiology perspective. The second core function of BMT is to conduct and lead establishment inspections required for the licensure of PDUFA products (PHS Act, 601.2(d), 601.20(d)). Furthermore, BMT participates in formal meetings with sponsors regarding product and process development, requirements for licensure, and new facilities. All these functions are accomplished through routine collaboration with the clinical divisions in the Office of New Drugs and the product quality reviewers in the Office of Biotechnology Products (OBP).
Review Function
BMT reviews the drug substance and drug product CMC section of BLAs and supplements. Regarding the drug substance, the microbial control (bioburden and endotoxin) strategy for all manufacturing steps is assessed using a scientific and risk-based approach. Potential risks to product quality attributes or process consistency are identified by evaluating the in-process controls and their effectiveness through process validation at scale. BMT assesses the microbial specifications for release of the bulk drug substance, the qualification of microbiological methods employed for in-process and release testing, and the microbial control and hold conditions for intermediates, in-process pools, media, and buffer solutions. In addition, validation data summaries for shipping the bulk drug substance to the drug product manufacturing facility are evaluated. The bulk may be transported globally frozen or refrigerated, and supporting data for shipping conditions and configurations are reviewed. Cross-contamination control is also evaluated when additional products are introduced into a licensed facility.
The drug product review consists of assessing the microbial control strategy for thawing and holding the bulk drug substance prior to sterile filtration, and the sterility assurance of the final drug product through the submission of: bacterial filter retention studies, validation data for the depyrogenation, sterilization of components, and steam-in-place of equipment in direct contact with sterile product, media fills and the description of the environmental monitoring program [5]. The microbiological product quality attributes for inprocess, release (sterility, endotoxin) and stability (sterility, endotoxin, container-closure integrity, in-use storage conditions following reconstitution, etc.) testing are reviewed. Shipping validation data are assessed as the drug product is frequently transported at refrigerated conditions. The lyophilization cycle development and parameters are evaluated for lyophilized products.
Establishment Inspections
BMT plans, leads and conducts pre-license and pre-approval inspections of biotechnology manufacturing facilities to assess their CGMP compliance status, to assess that products are manufactured in accordance with the standards established in the BLA and to verify the information and data in the BLA. A systems-based approach is employed using the 6 systems: Quality, Facilities and Equipment, Production, Materials, Laboratory Control, and Labeling and Packaging. The primary goal is to evaluate the capability of the manufacturing processes to consistently produce products that are safe, pure and potent and audit data integrity. In addition, cross-contamination risks are assessed, where appropriate. Several FDA guidance documents and compliance policy guides serve as tools for the inspection [6,7,8].
Product reviewers from OBP in the Office of Pharmaceutical Science participate in pre-license and pre-approval inspections. Their role is to assess the in-process controls (including viral clearance, where appropriate), assays and product specifications as specified in the CMC section of the BLA. The inspection report becomes part of the approval file of the application. There are cases where the inspection may be waived by applying certain internal criteria determined by BMT in consultation with OBP. The inspection waiver memo becomes part of the file of the application.
Examples of Review Deficiencies
Certain CMC microbiology deficiencies most frequently encountered in submissions to the FDA lead to application approval delays or non-approvals. Some examples are shared as illustrations that we hope will help reduce the number of information requests and review cycles for BLA approvals.
One obstacle to facilitating inspection plans and as a result, the review process and timelines, is the lack of registration of facilities and production schedules in the BLA. All facilities should be registered prior to submitting the application. The application must include all the facilities engaged in the manufacture and testing of the drug substance and drug product including their addresses, responsible person(s) and FDA Establishment Identifier (FEI) number. A preliminary production schedule should be submitted to facilitate planning the inspection during the review cycle as it is critical that manufacturing sites must be inspected while in operation and while manufacturing the product for which the application is pending (21 CFR 600.21). Ideally, production should be scheduled during the first half of the review cycle to allow for timely resolution of inspectional issues identified and completion of BMT’s review within the deadlines. This is especially important for new BLAs with priority status and prior approval supplements due to the short review timeline (4-6 months).
Regarding the drug substance, all manufacturing steps should be described in adequate detail to assess microbial control and limits. Oftentimes, the presence of 0.2 μm filters and routine monitoring for bioburden and bacterial endotoxins are not described. Bioburden and endotoxin limits have not been established and the methods have not been qualified. In other cases, submitted bioburden and endotoxin limits are too high to ensure process consistency and microbial control. Some processes are poorly designed for microbial control, (e.g., lack of filtration at key steps or equipment sterilization or sanitization). Bioburden control is of the utmost importance as high counts can result in protein degradation, uncontrolled impurities originating from different microorganisms, stability excursions due to the presence of microbial enzymes, and ultimately, loss of potency and purity leading to a potential loss of safety.
Furthermore, BMT’s application review considers the uses of water for injection (WFI) and purified water. WFI should be used in purification steps where no endotoxin reduction exists and in the formulation of the biological drug substance as frequently, the drug substance is not further formulated for the manufacture of an injectable product. Purified water should not be used as it is not designed for adequate control of bacterial endotoxins or other microbial by-products and may contain a considerable microbial load [9].
Other review deficiencies encountered include inadequate validation and control of hold conditions for process intermediates and pools and lack of shipping validation studies for transporting the drug substance to the drug product manufacturing facility. Inadequate monitoring or validation of process hold conditions can be detrimental to product quality due to the potential of increased bioburden and variable quality of intermediates and pools that can affect their stability as well as the stability of the bulk. Most drug substances are stored frozen or refrigerated, and then transported under frozen or refrigerated conditions. Shipping validation studies should be conducted and submitted to assess product quality during shipment.
Regarding the drug product, applications should contain adequate and scientifically sound microbiological validation data for thawing the bulk drug substance (if frozen) and storing it prior to formulation (if applicable) and sterile filtration. Microbial proliferation concerns increase for longer hold times. Other factors that should be considered include the microbial growth potential of the bulk, the presence of pre-filtration steps and the retentive capabilities of the filters to ensure final product sterility. A good number of submissions provide limited information on the production and validation filtration parameters, the bubble point values of the filters tested, the study controls (for example, the 0.45 μm size control filter that is generally used as a positive control) and the filtration method (bacterial challenge with product vs. product recirculation followed by the bacterial challenge).
The container-closure integrity studies also are frequently deficient. The sensitivity of the method and the controls are not provided. Furthermore, the studies may have been conducted without appropriate challenges: no vacuum or pressure and/or low concentration of dye or microorganisms.
Regarding moist heat sterilization of components and equipment, adequate summaries of validation studies using minimum and maximum load configurations are not submitted in some applications or are not supported by the provided data. Some submissions do not state whether fixed loads are used and do not identify the worst case load configuration for annual requalification. Alternatively, the rationale for the worst case load may not be supported by data and there may be inadequate bracketing of load configurations. In some cases, applicants neglect to provide sterilization validation data for gamma-irradiated product components, such as filters or receiving bags, which come into contact with sterile-filtered product.
Recent Inspectional Observations
Recent observations from BMT inspections of facilities manufacturing and/or testing biological proteins are discussed in the following section. Observations have been slightly modified for purposes of this article.
Manufacturing facilities must be free of insect infestation, cleaned and disinfected adequately since they are engaged in the manufacture of drug products. In many cases, these products are administered intravenously, intramuscularly or subcutaneously. A firm was cited for not maintaining the facility satisfactorily.
- Buildings used in the manufacture of drug products are not free of insect infestation. Specifically, insect traps are positioned in all controlled areas, with assigned alert limits. Alert limits were exceeded in the media formulation room […], an ISO 8 area. In addition, a spider was recovered from room […], an ISO 6 area in the aseptic core area of Building Y.
- The cleaning and disinfection program is inadequate. Specifically,
a) Vacuum cleaners are used in the aseptic processing areas (ISO 5, 6, and 7) in Building X.
b) None of the solutions used in the ISO 8 areas are sporicidal.
Banned carcinogenic substances were used for cleaning validation. Such substances should not be used on manufacturing equipment for cleaning validation or other activities.
The validation of the production process of […] is inadequate. Specifically, no studies have been performed to assess the removal of the […] dye (trisodium-2-hydroxy-1-[4-sulfonato-1Naphthylazo] naphthalene-6, 8-Disulfonate) used to demonstrate spray ball coverage of tanks and bioreactors in Building X, and no risk assessment was performed. This compound is a food additive that is banned in the US.
Three additional observations illustrate the importance of validated production processes, adequate microbial monitoring and control in the manufacture of a biological drug substance:
- Multiple lots of drug substance were released which had unacceptable high levels of bioburden during the final purification steps. In addition, bioburden limits have not been established for each step in the purification process.
- Hold times for four column eluates [column steps x, y, z) have not been adequately validated microbiologically. No microbial limits are established for these processing steps, and results show high bioburden levels (>1000 CFU/mL).
- There is no assurance that adequate microbial controls are in place during […] manufacturing. For example, during the harvest of the unprocessed bulk, sublots of Lot xxxx and Lot yyyy exceeded the established action limits for bioburden.
Ultimately, the drug substance lots with high bioburden were not released or were subsequently destroyed at considerable economic loss to the firm.
The following observation highlights the firm’s not following SOPs and inadequate quality oversight to ensure that all materials are appropriately tested. Several water samples were not obtained at the specified frequency. These omissions were not detected until several months had passed, which was one week prior to the inspection.
Inadequate quality oversight to make sure that materials are appropriately tested and the results are reported. Specifically,
a) Some of the Water for Injection (WFI) endotoxin test samples were not obtained at the specified frequency stated in the sampling schedule per SOP xxxx.
b) Similarly, there is inadequate tracking or documentation to verify that all environmental monitoring samples have been obtained as stated in the sampling schedule.
The purified water system is critical for manufacturing operations as it is used to produce WFI and clean steam and feeds clean-in-place systems and washers. The following observation highlights the inadequacy of the water system:
The water purification system is not adequate for generating water for its intended use. For example, deionized water, with a bioburden limit of 100 CFU/mL, has had bioburden results of “too numerous to count” (TNTC) on multiple occasions from several sampling locations in 2008. This water is used for clean in place (CIP) procedures of cell culture and harvest equipment, which in most instances do not include a water for injection (WFI) final rinse.
Conclusions
The intent of the authors is to provide guidance and a description of frequent review and inspectional issues encountered during BLA review and pre-license and pre-approval inspections. Special focus is presented on highlighting some of the issues for biologics that differ from those encountered with small molecules, as well as the challenges of the review and inspection process for these complex pharmaceutical drug products.
References
1. Title 21, U.S. Code of Federal Regulations.
2. Federal Register, Department of Health and Human Services, Food and Drug Administration. Drug and Biological Product Consolidation; Vol. 68, No. 123; June 26, 2003.
3. Public Health Service Act, Biological Products; 1944.
4. Federal Food, Drug and Cosmetic Act, as Amended.
5. U.S. Department of Health and Human Services, Food and Drug Administration. Guidance for Industry for the Submission Documentation for Sterilization Process Validation in Applications for Human and Veterinary Drug Products. Rockville, MD; 1994.
6. U.S. Department of Health and Human Services, Food and Drug Administration. Guidance for Industry: Q7A Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients. Rockville, MD; 2001.
7. U.S. Department of Health and Human Services, Food and Drug Administration. Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing – Current Good Manufacturing Practice. Rockville, MD; 2004.
8. U.S. Department of Health and Human Services, Food and Drug Administration. Compliance Program Guidance Manual, Program 7356.002M, Inspections of Licensed Biological Therapeutic Drug Products. Rockville, MD; 2003.
9. U.S. Pharmacopeia; 2009.
Anastasia G. Lolas, M.S. is a Microbiologist with the Biotech Manufacturing Team in the Division of Manufacturing and Product Quality in the Office of Compliance, CDER, FDA. She has over 4 years of experience as a microbiology reviewer of drug applications at the FDA. Anastasia holds a B.S. in Biology from Virginia Polytechnic Institute and State University and a M.S. in Food Science from the University of Illinois at Urbana-Champaign.
Bo Chi, Ph.D., is a Microbiologist with the Biotech Manufacturing Team in the Division of Manufacturing and Product Quality in the Office of Compliance, CDER, FDA. She has been with FDA since 2002 holding positions in CBER and CDER. Bo earned her Ph.D. degree in Microbiology from State University New York at Buffalo.
Patricia F. Hughes, Ph.D. is the Team Leader in the Biotech Manufacturing Team in the Division of Manufacturing and Product Quality in the Office of Compliance in CDER, FDA. She has over twenty years experience in the Pharmaceutical/Biotech industry in fermentation & cell culture process development and manufacturing. In addition, she has over six years of experience as a microbiology reviewer at the FDA, in CDER and CBER. Patricia holds a Ph.D. in Microbiology from Georgetown University.
Kalavati Suvarna, Ph.D., is a Microbiologist with the Biotech Manufacturing Team in the Division of Manufacturing and Product Quality in the Office of Compliance, CDER, FDA. She has over seven years of experience as a microbiology reviewer at the FDA. Kalavati holds a Ph.D. in Biological Sciences from Northern Illinois University.
To correspond with author, please e-mail her at: [email protected]