Stephen F. Carroll
The Discovery Process 85
Nonclinical Development and Testing 98
IND-Enabling Studies 102
Added Discovery Work 103
The discovery of new products for patient use takes place in laboratories at universities, in the government, or in pharmaceutical companies; actually, it starts in the minds of scientists with a scientific innovation or idea for creating a new therapeutic molecule that may be a biological or drug. This research is performed through carefully done studies, either with the physiology of humans or other species, disease models, or some core structure of a molecule, through a host of different scientific technologies. Sometimes, a drug discovery is an accidental finding related to an unexpected action of a drug being studied for other uses, such as Viagra® for impotence. Each molecule may have an impact on a general physiologic process such as inflammation and thus have the potential to be used in many organ systems and diseases, or it may impact a specific receptor on a cell, such as a tyrosine kinase, and be used only when the receptor system goes awry. Knowledge of the discovery and early development process creates a basis for understanding how potential new therapeutics advance from the research laboratory to the clinic and some of the issues involved.
Molecules designed for therapeutic use come in many sizes and shapes. Although most of the therapeutics on the market today are "small molecules," also called drugs, such as aspirin (13 atoms, excluding hydrogen atoms), Viagra® (33 atoms), and Taxol® (62 atoms), increasing efforts are being placed on the development of larger "biological" molecules. Included among the biologics are molecules like insulin (408 atoms), erythropoietin (2,634 atoms), and antibodies (10,402 atoms). Most small molecules are produced by excretions from microbial fermentation or produced by chemical synthesis, often in combination with structural modifications produced by techniques of medicinal chemistry. Biologics are manufactured by complex living systems (e.g., recombinant techniques), where transfection of the appropriate gene into a suitable cell line (either micro-bial or mammalian) allows production of the therapeutic protein. For some products like monoclonal antibodies, hybridomas that produce the antibody initially are created from murine and lymphoid myeloma cells for antibody production. These hybridomas then can be used to produce the monoclonal antibody or, more commonly, the antibody genes are transferred to another host cell, such as Chinese hamster ovary (CHO) cells for clinical production. Each class of compounds, small molecules and biologics, has unique advantages and disadvantages that can be utilized and tailored to address specific therapeutic needs.
In this chapter, we will discuss the steps involved in the discovery and early development of new therapeutics, leading up to an Investigational New Drug (IND) application. We will also try to discuss some of the issues encountered along the way. These topics will be covered in seven sections (discovery process, targets, products, nonclinical development and testing, IND-enabling studies, added discovery work, and a summary) and 42 figures.
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