Introduction
The objective of this document is to propose an achievement of product microbial Real Time Release (RTR) based on process and product understanding. The four stages of Design for Manufacture/Quality by Design need to be applied to develop the RTR model for the microbial Critical Quality Attribute (CQA) as presented below.
Design Intent
The Microbial Limit Test is a regulatory specification for the final drug product and is considered to be an appropriate CQA based on the manufacturing, quality and commercial history of the product.
In the first phase of the product process redesign project, each unit operation needs to be evaluated for its impact on the microbial quality. A review of the manufacturing process and quality systems for the drug product need to indicate a high level of microbiological assurance and control. The review led to a greater understanding of the microbiological control mechanisms and identified additional opportunities for enhancing these mechanisms. These opportunities have to be identified using a risk analysis tool.
DESIGN SELECTION
Process understanding obtained during the first phase of the process redesign project enabled the company project team to identify the attributes potentially critical to ensuring the drug product meets the microbial CQA. The exercise to determine the appropriate quality attributes and parameters is in-progress. The propose control strategy for the microbial CQA will be based on the Critical Quality Attributes for materials and components (MC CQA) and Quality Critical Process Parameters (QCPP) defined for monitoring of the manufacturing environment. The microbial QCPPs will be environmental monitoring sampling points critical to the drug product quality as determined by using risk analysis tools. Potential MC CQAs and QCPPs for the microbial CQA are listed below.
MC CQA:
Excipients
API
Components
Prefiltration bulk solution
QCPP: Critical environmental monitoring of air and surfaces
Control Definition
In the third stage of DfM, the control strategy will be defined. For the microbial CQA, Rapid Microbiological Methods (RMM) are being investigated to monitor the MC CQAs and QCPPs. The proposed RMM for monitoring QCPPs and MC CQAs provide more timely measurements during processing and provide higher level of control based on the increased sensitivity of the methodology.
GSK Parma, Italy site is currently using bioluminescence test system for Microbial Limit testing of the final drug product. This RMM was approved September 23, 2003 and the manufacturing facility has 3 years of experience applying this technology. Additionally, a comparability protocol for applying RMM to the testing of pharmaceutical grade waters was approved February 20, 2004. The bioluminescence testing methodology was validated at the site and in use.
For monitoring of the MC CQA and QCPP defined during Design Selection stage, the following technologies are being investigated: chemiluminescence’s and bioluminescence. Technology for each MC CQA and QCPP will be selected based on historical data and system capabilities. A brief description of each technology is provided below.
Chemiluminescence technology
This method of solid phase cytometry utilizes membrane filtration to separate potential microbial contaminants from filterable samples prior to labeling of the captured cells with a universal viability substrate. Once within the cytoplasm of metabolically active microorganisms, the non-fluorescent substrate is enzymatically cleaved to release free fluorochrome by the hydrolytic enzyme esterase. Only the viable microorganisms with membrane integrity have the ability to retain the marker used in the assay. A laser-based detector then automatically scans the membrane, and the number of fluorescent labeled cells immediately reported. The data can be confirmed visually using an epifluorescence microscope.
As this method eliminates the need for cell multiplication, sensitivities to the single cell level, independent of volume filtered, are possible for all microbial cells including spores, stressed organisms and fastidious organisms. Since more sensitive end-point detection mechanism is employed when compared with traditional growth based techniques, near real time results are obtained, typically within 2-3 hours of sample preparation.
Note: the chemiluminescence technology is included in the Comparability Protocol for pharmaceutical grade water testing approved by FDA February 20, 2004.
Pass/fail (qualitative) bioluminescence system
The ATP bioluminescence test system consists of a conventional photo-multiplier tube (PMT) luminometer which senses light given off by a reaction between the bioluminescent enzymes in the system reagents and the ATP found in all living micro-organisms.
The system is easy to use, versatile and portable luminometer that can be used qualitatively to detect the presence or absence of microorganisms. For some applications pre-enrichment in media may be required. The system can be used very effectively in the rapid evaluation of filterable products.
Quantitative bioluminescence system
The quantitative bioluminescence microbial enumeration system also permits qualitative screening. It is a combination of new technology and conventional microbiology. It has the potential for single micro-colony forming unit (micro-cfu) detection on a highly specialized membrane.
The system uses conventional ATP bioluminescent enzymology. Light is detected using a highly sensitive Charged Coupled Device (CCD) camera. In addition, a specialized membrane has been developed for the capture and segregation of microorganisms. Membrane filters are transferred to media and incubated for approximately 24 hours before being exposed to ATP bioluminescent reagents. The system intensifies the bioluminescence from microorganisms on the membrane through an image intensifier device and captures the light signals with the CCD camera. An image processor enumerates the microorganisms and displays them on screen. All these factors combine to produce a rapid, sensitive quantitative test system which is suitable for evaluating the microbial quality of filterable products.
Increased Sensitivity of Collection Techniques for Environmental Monitoring
Surfaces
The Parma team is also investigating the use of a new flocked swab for surface sampling in the environmental monitoring program. The recovery capability for the current swabs is approximately 20%. The new swabs have been demonstrated to recover approximately 65- 70% of the challenge organisms.
Air
The current air sampling procedure collects 1 m3 of air in approximately 10 minutes. Studies have been performed to demonstrate that the current technology can be used to collect an air sample for eight hours using one collection membrane. This collection period translates to a sample size of 48 m3 of air.
This increased sensitivity of the collection methods could potentially impact the current applied alert and action levels for the manufacturing environment. During the Control Definition phase, the company has to considered the needs to apply higher limits to the alert and action levels for environmental monitoring for drug product released due to the increased sensitivity of the collection techniques and testing methodology. Statistical analysis tools need to be used to determine the appropriate data set for re-evaluating the levels applied to environmental monitoring.
The idea is to validate the three described RMMs for environmental monitoring (air and surface samples) and apply the appropriate technology based on analysis of historical data and system capabilities. Specific methods will be then registered for monitoring the MC CQAs.
The design space for the microbial CQA has to be confirmed using multicombinato-rial/statistical analysis of MC CQA and QCPPs.
Control Verification
The fourth phase of Design for Manufacture, Control Verification, for the microbial CQA needs to be defined in the overall strategy for Real Time Release.
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Gilberto Dalmaso is the manager of the Aseptic QA & Biological Lab Group within the Quality Assurance Directorate in GlaxoSmithKline Manufacturing SpA Parma site. In this role the main activity is to assure the microbiological quality of the products within Parma facility.
His laboratory obtained from the FDA the first microbiological PAT approval in the world for a rapid microbiological testing on a GSK nasal spray and process waters. His laboratory also obtained the same approval from the EMEA member states. Rapid Microbiological tests are now routinely used for WFI monitoring and the US release for a GSK nasal spray. Gilberto is: GSK Worldwide team member for rapid microbiological technologies development, speaker to a number of symposium and conferences in microbiology in Europe and US, quality system ISO 9000 inspector and HACCP inspector.
To correspond with the author, please contact the editor at: [email protected]