RAPID METHODS AND THE DRUG DEVELOPMENT PROCESS The drug development process can be divided into three broad areas:

• Research,

• Development, and • Manufacture.

During the research phase, new chemical entities (NCEs) are produced from natural sources and chemical synthesis. These compounds are screened for signs of pharmaceutical activity before they go on to preliminary toxicological evaluation. In the past this screening process has been somewhat random. Huge banks of microbial isolates and natural products have been evaluated. This situation is changing rapidly. Automation, robotics, biotechnology, and combinatorial chemistry are having a huge impact on drug discovery. Combinatorial chemistry is slashing the time taken to develop NCEs. It is also expanding the potential number of candidate compounds because of the precise way in which active molecules can be manipulated. Biotechnology is now beginning to have an impact also. New biological entities (NBEs) are emerging. The message here is that the number of active compounds coming into drug development pipelines is increasing at an alarming rate. New rapid screening methods that will allow the efficient processing of large numbers of compounds are required. Current pharmacopeia methods such as preservative efficacy and antibiotic screening are too labor intensive. New methods that will allow high throughput evaluation of potential NCEs and NBEs are needed.

During the development phase, potential active compounds are taken into preclinical and clinical evaluation stages. A huge amount of information is generated on the pharmacology, toxicology, chemistry, and microbiology of the active compound and its route of manufacture. Synthesis, scale-up, and manufacture processes are developed, evaluated, and finalized. Drug stability programs are developed and are run for up to several years. Analytical methods are developed and validated. The development phase culminates in the production of a regulatory submission. A product is ready for sale only when a manufacturing license has been granted. This whole process takes several years. The active compound will be under patent by OVERVIEW OF ALTERNATIVE RAPID MICROBIOLOGICAL TECHNOLOGIES 29

then, so the longer the development process takes the shorter the patent life for the final product. Drug development is expensive, costing in the range of £200 M to £300 M. Rapid methods are needed in the development phase for both in-process testing and product release testing. Details of the product release test will have to be registered in the regulatory submission. The FDA and European regulatory authorities will need to scrutinize any new method. Details of the test and validation data will need to be supplied, along with a justification and demonstration of equivalence with more traditional methods. It is for this reason that dialogue among the regulatory authorities, manufacturers of new technologies, and potential users is essential. It is quite unthinkable that regulatory submission for a new product could be delayed due to the introduction of unfamiliar microbiological test methods. Years of work could be wasted and revenue lost. This situation begins to explain the innate conservatism of the pharmaceutical industry. It also underlines the difficulties experienced by unwitting technology suppliers accustomed to less regulated markets.

During the manufacturing process, the registered product is produced for sale to the public. Microbiological data are generated in three main areas: raw material testing; in-process controls, including environmental monitoring; and product release testing. The degree and amount of testing will depend on whether the product is sterile or nonsterile. Bottlenecks will be process dependent. Real-time analysis is not yet possible. Real-time data for raw materials and in-process testing would significantly contribute to reducing production losses. Emerging technologies offer the potential of single cell detection within 2 to 3 hours; examples are the ScanRDI and bioluminescence, particularly adenylate kinase.

Cost

A major consideration in the successful introduction of new technologies into industrial microbiology is cost. In general, increased sensitivity requires expensive detection systems. The use of such techniques will depend on the size and wealth of the manufacturing company and the relative value of the product involved. It is important to consider the overall savings a new method will create in the manufacturing process. The method may require specialist advice. Software to assist nonfinancial specialists to do this sort of complex economic evaluation is increasingly available. Process bottlenecks and estimated losses due to batch failure or recall must be considered. This type of economic evaluation is not normal practice for the pharmaceutical microbiologist. In fact it is not common practice at all to consider the impact of individual parts of a manufacturing process on the overall efficiency of the system. Such analysis is essential, however, if the real benefits of rapid methods to the overall process are to be realized. It is an encouraging sign that many pharmaceutical companies are beginning to consider process optimazation.

New Method Requirements

New methods have been introduced very successfully in the food and beverage sectors over the past 20 years. These technologies have been given the collective name of Rapid Methods and include ATP bioluminescence, impedance, the direct epifluorescent filter technique (DEFT), and others. To date none of these techniques have been widely used by the pharmaceutical sector, in part because of a lack of sensitivity of many of these rapid methods. However, a more fundamental problem has been the failure of the technology suppliers to understand the specific technical and regulatory requirements of the pharmaceutical sector. These requirements are very different from those of the food and beverage industries. Initially it was hoped that methods from one industry could be easily transferred into the pharmaceutical sector. There was little, if any, communication between the manufacturers of these techniques and the potential users in pharmaceutical microbiology. As a result little technology transfer was seen between the different industry sectors. The suppliers appeared to overpromise and underdeliver. This has created a considerable amount of skepticism among pharmaceutical microbiologists toward rapid methods in general.

Because the pharmaceutical sector is highly regulated and conservative, introduction of any new method is a complex issue. Successful introduction of new test methodology into pharmaceutical microbiology requires several ingredients:

• fitness of purpose (the ability to do the job); • validation package and support;

• regulatory acceptance; and • time, money, and commitment.

“Fitness of purpose,” an expression gaining ground in the area of rapid methods, means that the test method in question must be able to do what it says it can do. The ability to do the job is a little more difficult to demonstrate, for the following reasons. Equivalence with a reference method is required. Unfortunately many of the “gold standard” reference methods, such as membrane filtration and agar plate methods, are not perfect. They can be less sensitive than emerging techniques, and direct comparison can result in poor correlation. A good example is microbial enumeration using ATP bioluminescence compared to

agar plate methods. In bioluminescence the amount of light produced by an enzymatic reaction, luciferin-luciferase, is used to quantify the number of microorganisms present. The amount of light produced is directly proportional to the ATP present. Pour plating, on the other hand, requires the growth of individual organisms on nutrient media to produce visible colonies. Microorganisms in nature, however, tend to exist in clusters, not as single organisms. The nutrient media and conditions used can adversely influence the recovery of microorganisms, particularly if they are stressed in the transition from natural environments. The direct comparison between microbial ATP content and the ability to grow on nutrient media can therefore lead to differences between bioluminescent-based methods and traditional plate techniques.

Validation is the process required to demonstrate that a given method can achieve what it sets out to do. With rapid methods validation is an important consideration. Software and hardware must be fully validated to the requirements of GMP. Documented proof must be made available to prospective users and regulatory bodies. It is also vital that the user and the supplier of new techniques design a suitable performance qualification (PQ). The PQ must be able to demonstrate accuracy, sensitivity, robustness, and suitability of the new method to the task at hand. Guidelines on how to implement and validate microbiological rapid methods are beginning to emerge. One such document is the Parenteral Drug Association Technical Report No. 33 “Evaluation, Validation, and Implementation of New Microbiological Testing Methods.” This document is an invaluable guide to anyone interested in implementing microbiological rapid methods.

Above all, dialogue among the industry user, technology supplier, and regulatory authorities is essential. Encouraging signs that this process has started are that new techniques are emerging and regulatory approval is being given. In 1997 the UK’s Medicines Control Agency approved the use of an ATP-based method for the rapid screening of nonsterile product testing (Weatherhead 2000). This new breed of rapid methods results from close collaboration of government agencies, the industry, and the rapid method manufacturers (Wills et al. 1997b). An important difference from earlier attempts is not the technologies themselves; they are in fact similar to earlier methods. Instead, the difference is the way in which these methods have been designed to satisfy the needs of the pharmaceutical sector in both functional and regulatory aspects.