Early drug development, HPLC

However, compared with the traditional analytical methods, the adoption of chromatographic methods represented a signihcant improvement in pharmaceutical analysis. This was because chromatographic methods had the advantages of method specihcity, the ability to separate and detect low-level impurities. Specihcity is especially important for methods intended for early-phase drug development when the chemical and physical properties of the active pharmaceutical ingredient (API) are not fully understood and the synthetic processes are not fully developed. Therefore the assurance of safety in clinical trials of an API relies heavily on the ability of analytical methods to detect and quantitate unknown impurities that may pose safety concerns. This task was not easily performed or simply could not be carried out by classic wet chemistry methods. Therefore, slowly, HPLC and GC established their places as the mainstream analytical methods in pharmaceutical analysis. 

Whereas the other separation methods have been demonstrated to also provide the requisite performance for release and stability testing for select drug substances and drug products, more typically the techniques are applied as supportive methods for HPLC during early-phase development and in niche areas during late-phase development. Because each separation method provides a different mechanism of separation to HPLC, utilization in early-phase development can be used to confirm specificity of HPLC methods. In later phases, both SFC and CE have shown applicability to chiral separations, and GC remains as the unique technique for the determination of residual solvents. 

More than half of small druglike molecules are chiral. The Food and Drug Administration (FDA) requires testing of pure enantiomers. Such testing is most useful early on in drug development. SFC is dramatically superior to HPLC for chiral separations. SFC offers dramatically faster method development and should be the technique of choice for any molecules soluble in organic solvents (i.e., most druglike molecules). Further, unlike capillary electrophoresis, SFC is fully scalable. A method developed at the analytical scale should work equally well at the semiprep level. 

This chapter reviews the use of HPLC in pharmaceutical analysis from drug discovery to quality control. The focus is on HPLC analysis of drug substances (DS) and products (DP) such as assay for potency, purity evaluation, and dissolution testing. A case study of the various HPLC methods used during early clinical development illustrates the versatility of this technique. Detailed descriptions of HPLC applications in pharmaceutical development and LC/MS analysis in drug discovery and bioanalytical studies can be found elsewhere.1-6 The regulatory aspects in pharmaceutical testing are covered in Chapter 9. 

---