How are new drugs discovered?

Developing a new medicine begins with understanding the disease or condition as thoroughly as possible. Basic research provides clues about how to treat diseases and potential ways to target the symptoms or underlying causes. Researchers work to understand biological targets of the drug they want to develop which can be protein, RNA, DNA, and other molecule that is related to the disease. The researcher work to discover a lead compound which is a promising molecule that could influence target and has a potential to be developed into a medicine.

Clinical Trials

Clinical trials are necessary in drug development process. They are the most time and budget consuming in research and development process. The company that intends to conduct the clinical trials must file an Investigational New Drug (IND) application to Food and Drug Administration (FDA) to allow the investigational drug to be tested in human volunteers and the clinical trial must be carefully designed to test benefits and risks of the treatment. Every clinical trial must be led by medical doctor, researchers, and a team of nurses. To prove drug safety and effectiveness, a broader group of volunteers must be included in the clinical trial. Moreover, all IND applications must be approved by Ethics Committee of the trial sites prior to submission to FDA.

In drug discovery and research process, a great number of candidate medicines are not successfully developed to a new medicine. From the statistics, it if found that less than 12% of the candidate medicines that make it into Phase I clinical trials will be approved as a new medicine as portrayed in the below figure.

FDA Review and Approval

All imported and locally manufactured drugs must be registered with FDA. In case of new drug, the clinical trial results are important information to prove that the drug is safe and effective. Consequently, there is a great deal of documentation on information for new drug registration

For Thailand, after submission, the FDA will have the files reviewed by experts and consider their advice prior to granting approval for such application.

Overall life cycle of drug from discovery to post marketing can be seen in the below chart.

Let’s learn more about drug classes

Apart from scientific problems encountered during R&D, another drug challenge is varying classes of medicines, e.g. small molecules, biotherapeutics, and vaccines are usually characterised by systemic scientific challenges. Solutions for one drug class may not be applicable for other drug classes that the technological focus is fundamentally different.

Small Molecules

Small molecules are light-weight medicine synthesized from chemical compound that can potentially treat or manage diseases. This type of medicine works by inhibiting or inducing certain responses in biological pathway. The R&D of small molecules can be classified to 3 general innovation tracks: molecular discovery, formulation, and physiological interaction.

Small molecule discovery is an engineering process of molecule which can be categorized by function when a group of molecules works together to increase overall efficacy of drug. Next, the formulation generally known as drug formula is an important process because it combines all molecules with different functions to work together to treat a patient. The challenge of formulation is how to make a medicine that can treat disease and is safe at the same time. Any drug that is discovered to treat particular disease may be further researched and developed to be useful for other indications in the future. According to the statistics, approximately 1 in 5,000 screened molecules may eventually become the only available medicine.


Biotherapeutic medicines are derived from proteins and other compounds produced by living organisms, such as cells, viruses, and bacteria. Biotherapeutics aim to closely mimic compounds that are naturally produced in the human body. R&D in this area is often more complicated than small molecules research because underlying organism’s genetic and molecular makeup must be fully understood in order to induce production of therapeutic compounds.

Like small molecules development, biotherapeutics R&D begins the with discovery, formulation and medicine interaction. The discovery process generally involves mapping biotherapeutics interactions. However, biotherapeutics are complicated because it is produced from living organisms, protein folding, and functional group orientation. Therefore, they are very sensitive to experimental conditions e.g. temperature, pH, etc. In addition to understanding the aforementioned process, researchers must genetically map living organisms to produce therapeutic compounds.

Although the research is successful, companies still face the problem of scaling up production to launch to market. This process is completely different from small molecules. Having living organisms as the underlying compounds, it is difficult to mass produce this type of medicine.


Vaccines are biological products that help build human immunity. Vaccines are derived from antigens which are surface proteins of living organisms. With the right amount of antigens, vaccines aim to stimulate antibody production in patient’s immune system so that the immune system is equipped to combat future infections that exhibit corresponding antigens.

The discovery of vaccine focuses on identifying pathogenic antigens. This process involves studying a pathogen’s surface proteins and identifying candidate antigens that can be further developed. Next, it is to study the antigen safety. Since the antigen will eventually be injected to human body, antigen safety studies are essential to determine whether immunological responses are proportional to the introduced antigens, for example, viral vaccines e.g. influenza, can utilize whole virus, split virus, surface virus, or live attenuated antigens. Therefore, there is no “one size fits all” answer for vaccine use.

When appropriate and safe antigens and vaccines are found, the R&D shifts to scaling up the production of antigen and formulating effective and safe inoculations. Similar to biotherapeutics R&D, it is difficult to scale up the production because of the living organisms used to produce antigens. Meanwhile, other research focuses on formulating appropriate inoculations. The goal is to produce a preparation that is relatively stable in a variety of “in the field” conditions for vaccine needs.