Advanced analytical and microbial methods for biopharmaceutical and pharmaceutical products and processes

Abstract

In recent years, pharmaceutical research has begun to shift from the development of small molecule chemical entities, to complex high value, low volume biologics. The cost of batch losses or product recall due to the presence of microbial, chemical or physical contaminants can have serious implications for a business. It is therefore important that as the complexity of pharmaceutical products increases, the techniques utilised in the analysis and characterisation of these products and their excipients also moves forward, thereby ensuring product quality and patient safety. This research explores three areas of analysis and characterisation relating to pharmaceutical products: microbial testing; oxidative stability testing and container integrity testing. The detection and identification of microbiological contamination using traditional microbial methods (TMMs) have a number of limitations such as long testing times and reliance on subjective assessment leading to operator error. More recently developed rapid microbial methods (RMMs) have been designed to overcome these limitations and their uptake would enable microbial testing to align with the process analytical technology (PAT) approach to process monitoring and control. A review of available techniques and those implemented by a large pharmaceutical company, GlaxoSmithKline has highlighted that a number of RMMs are being utilised, but their widespread adoption in the pharmaceutical industry faces several barriers including: economic and financial; institutional; legislative and regulatory; and technical. Another important area of pharmaceutical product analysis is that of oxidative stability testing. A comparison was undertaken of two machines for measuring oxidative stability (the Rancimat (Metrohm) and the ACL Instrument (ACL Instruments, Switzerland) to investigate their performance and assess their applicability for the testing of pharmaceutical excipients. The testing of corn oil, selected as a model substance, revealed a strong correlation between the results from the two machines. An aspect of oxidative stability testing is concerned with residual levels of peroxides therefore the ACL Instrument was compared to iodometric titration, a highly empirical traditional approach, for the quantification of peroxides in corn and Menhaden oil. Good correlation was found between peroxide levels measured by the two methods, but the results from the ACL Instrument showed a dependence on oil type, meaning that a standard would be required each oil type. Additional testing was carried out on Page | iii polysorbates, pharmaceutical excipients that are known to pose stability issues in final formulations, due to containing residual amounts of peroxides. Using the ACL Instrument it was possible to detect differences in oxidative stability between grades and types of polysorbate. It was not possible to discriminate between batches of the same grade. The final testing that is carried out on pharmaceutical products stored in glass vials, is container integrity testing. High voltage leak detection (HVLD) is one method utilised and concerns exist as to whether the high voltages present can cause ozone formation in the container headspace, leading to degradation of the drug product. A method involving potassium indigo trisulphonate was developed for the detection of ozone and a test protocol implemented. This approach showed that ozone was produced in containers with a low fill volume, but at a very low concentration and hence it should not affect the stability of the final product. The research carried out in this thesis has drawn together evidence on RMMs; furthered understanding of the applicability of oxidative stability testing for pharmaceutical excipients; and has highlighted the importance of investigating the effect of container integrity testing methods on the final pharmaceutical product.