Early phase method

For early phase methods emphasis is placed on specificity and these methods generally require less extensive validation than those in final development. The following method parameters should be included in... 

For early phase methods, the precision tests only include injection repeatability (also referred to as system repeatability) and method repeatability (also referred to as analysis repeatability). The former is demonstrated by repeating injections of a standard solution and the latter by preparing multiple samples over multiple concentration levels (usually at 80%, 100%, and 120% of the nominal concentration) from the same lot of a composite sample of the dosage form. 

Early phase methods usually adopt a simple way to establish method sensitivity by preparing a 0.05% solution of the API relative to the standard solution, which is injected multiple times during validation to obtain an RSD value (<15%, N=6). Later, this solution is injected every time the method is used to assure that adequate sensitivity is observed at the time of use. 

An additional key validation criterion for early phase methods is an evaluation of solution stability to establish that the API and related substances do not degrade in the solvent system used for sample preparation. This allows for limits to be set for solution lifetime. 

Information in regulatory files (e.g., clinical trial applications). Existing literature and current compliance guidelines and procedures. Feedback on early phase methods. 

An example of the minimum requirement for potency assay of the drug substance and drug product is tabulated in Table 4. Note that the postponement of intermediate precision is aligned with previous discussion that the use of early phase analytical method resides mainly in one laboratory and is used only by a very limited number of analysts. Each individual company s phased method validation procedures and processes will vary, but the overall philosophy is the same. The extent of and expectations from early phase method validation are lower than the requirements in the later stages of development. The validation exercise becomes larger and more detailed and collects a larger body of data to ensure that the method is robust and appropriate for use at the commercial site. 

The validation report should contain reference to the analytical methods (specific code number used as identifier within the pharmaceutical organization) and the corresponding drug substance or product name. Note that for early-phase method validation reports the results maybe filled in a predefined table and compared against the acceptance criteria. However, for late-phase validation, more explicit reports are generated explaining each and every experiment, with detailed steps of sample and standard preparation. 

It is unrealistic to envision that a single method can be developed for the determination of the API and related substances in both drug substance and drug product and, at the same time, be optimized to support all phases of pharmaceutical development. Instead, the development of a test method should be conducted in the context of a critical examination of what the method will be used to measure and the method validated to demonstrate that these criteria have been met. For early-phase methods, regulatory guidelines are unspecific, whereas, for late-phase methods, regulatory expectations provide a comprehensive set of performance goals that a method should achieve. 

Accordingly, the method development guidelines provided here for early-phase methods are flexible and are intended as guidance only. For late-phase methods, there is considerably less flexibility in approach. A comprehensive discussion of method validation is presented in Chapter 12. Validation issues will be addressed here only in the context of developing methods that satisfy the requisite validation requirements. 

Drug Substance. Methods should separate the API and the synthetic process impurities and drug substance degradation products observed at significant levels (see Chapter 4) using the early-phase methods. 

Early-phase method development typically begins with the receipt of drug substance from laboratory-scale synthesis and purification. Along with the API, the following information should be requested (or generated) ... 

Unlike early-phase methods, the criteria for late-phase release and stability studies are well defined by regulatory guidelines (see Chapter 12). Although it has been emphasized earlier that discussion of validation issues will not be a primary focus of this chapter, method development must be performed in the context of meeting regulatory expectations. Minimal discussion of regulatory considerations will, therefore, be interjected, where applicable, to the discussion of method development. 

Results of the study indicate that it is possible to simultaneously detect the active drug substance and most related substances at 0.1% (w/w). Furthermore, the method provides different selectivity than reversed-phase HPLC. As a broader conclusion, this indicates orthogonality to reversed-phase HPLC and suggests the viability of SFC in support of early-phase method development. 

All phases of analytical development are ideally supported by chemical separation techniques such as HPLC, TLC, GC, SFC, and CE. HPLC continues to be the primary method of analysis throughout the pharmaceutical development process. Although HPLC is limited in its ability to separate more than 15-20 components in a single analysis, and variations in columns and instrumentation manufacturer to manufacturer complicate transfer of methods, HPLC can readily be implemented to meet ICH requirements for method performance. For early-phase methods, HPLC can be coupled dynamically to mass and nuclear magnetic resonance spectrometers to facilitate the identification of unknown impurities. In later phases, HPLC can be implemented in a fully automated format as a high-throughput method for release and stability testing. 

Table 8.5. Suggested Columns and Mobile Phase Conditions for Early-Phase Methods...

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