The drug development process is where new drugs are currently discovered and developed, frequently using a rational approach involving experimental evidence. Often this process may begin with the screening of a multitude of compounds, selecting one that can inhibit (inactivate) certain molecular targets or receptors (structure or site on the surface or interior of a cell that binds with substances such as hormones, antigens, drugs, or neurotransmitters). Once a suitable compound is found, it can then be modified to enhance its effectiveness based on its interactions with the target. Molecular target screenings are increasingly utilized to study natural products for anticancer therapy, among other therapies.

Novel chemical entities (NCEs) are compounds that emerge from the process of drug discovery. These will have promising activity against a particular biological target thought to be important in disease processes. However, little will be known about the safety, toxicity, pharmacokinetics, and metabolism of this NCE in humans until clinical trials are performed.

Historically, most drugs have been discovered either by identifying the active ingredient from traditional remedies and manufacturing it, or by chance, known as serendipitous drug discovery.

The rational approach, which has much promise for the future, seeks to understand how disease and infection are controlled at the molecular (simple or basic structure or form) and physiological (entire living organism) level, and to target specific entities based on this knowledge, such as drug receptors on target tissues. This practical process includes identifying candidates, synthesis and characterization of the compound, and screening or testing for therapeutic efficacy. Another method of screening possible compounds includes the use of human cell lines. In cancer research, these cell lines have known characteristics regarding drug response, growth factor dependence, and oncogene (genes that may be related to cancer) expression. A comparison can then be made between the response patterns of the experimental compounds and other agents. If a compound proves valuable through these tests, it will then be further developed before clinical trials begin.

Animal testing, drug discovery, high throughput screening (HTS), investigational new drug (IND), new drug application (NDA), novel chemical entities (NCE), phase I studies, phase II studies, phase III studies, phase IV studies, rational drug design, serendipitous drug discovery.