Natural Products as Leads to Potential Drugs: An Old Process or the New Hope for Drug Discovery?

Abstract

From approximately the early 1980s, the “influence of natural products” upon drug discovery in all therapeutic areas apparently has been on the wane because of the advent of combinatorial chemistry technology and the “associated expectation” that these techniques would be the future source of massive numbers of novel skeletons and drug leads/new chemical entities (NCE) where the intellectual property aspects would be very simple. As a result, natural product work in the pharmaceutical industry, except for less than a handful of large pharmaceutical companies, effectively ceased from the end of the 1980s. What has now transpired (cf. evidence shown in Newman and Cragg, 2007 and Figures 1 and 2 below showing the continued influence of natural products as leads to or sources of drugs over the past 26 years (1981–2006)) is that, to date, there has only been one de novo combinatorial NCE approved anywhere in the world by the U.S. Food and Drug Administration (FDA) or its equivalent in other nations for any human disease, and that is the kinase inhibitor sorafenib (1, Chart 1), which was approved by the FDA in late 2005 for renal carcinoma. However, the techniques of combinatorial chemistry have revolutionized the deVelopment of active chemical leads where currently, instead of medicinal chemists making derivatives from scratch, a procedure is used whereby syntheses are based on combinatorial processes so that modifications can be made in an iterative fashion. An example of such a process would be the methods underlying the ultimate synthesis of the antibiotic linezolid (Zyvox, 2) by the Pharmacia (now Pfizer) chemists starting from the base molecules developed in the late 1980s by DuPont Pharmaceutical, who reported the underlying antibiotic activity and mechanism of action of this novel class of molecules, the oxazolidinones.