Drug discovery and development is very complex, time consuming and costly process which requires large number of collaboration of individuals and groups from various departments such as research, development, formulation, medical, marketing and business management.
Drug discovery defined as the process of identifying molecules that have the potential to become the applicable new treatment approach. This drug discovery involves the sequential steps which consists of – target selection, drug selection and product development. Target Selection involves choosing a disease to treat and then developing a model for that disease.
Common Ways of Developing New Drugs:
1. From Natural Sources e.g. Plants and animals
2. By modification of chemical structure of existing molecules
3. Studying disease processes
4. By using Computer-Aided Drug Discovery approach to design new drugs
Different Approaches Used in Drug Discovery Process:
1. Identification of novel path that involves with disease, selection of targets in that path and development of screens.
2. High throughput screening of large number of compounds for desired biological activity.
3. Molecular modelling methods to generate 3D structure of target molecules and model. Docking method to find binding affinity towards target protein.
4. Combinatorial chemistry consists of systemically modifying an existing compound chemically to act on a selected target.
The main objectives to perform preclinical tests are-
1. develop a pharmacological profile of the drug.
2. determine the acute toxicity of the drug in at least two species of animals
3. conduct the short term toxicity studies ranging from 2 weeks to 3 months, depending on the proposed duration of use of the substance in the clinical trials.
Clinical development or clinical research is done in four phases (I, II, III, IV).
Phase I- This phase addressed the following-
- How drug is absorbed?
- What is and where is the drug distributed in the body?
- Which organ or organs involves in the metabolism and excretion of the drug?
- How rapidly the drug eliminated from the body?
- What is the mechanism of action of the drug in humans?
Phase II- This phase addressed the following-
- What is the most effective dosage range and is the drug safe within the range?
- What is the minimum effective dose?
- Is the drug effective in mild, moderate and severe cases of the disease or condition?
- Is the drug effective for all expected indications?
- What is the maximum tolerated effective dose?
Phase III- This phase addressed the following-
- Overall risk-benefit relationship.
- The ideal dosage regimen.
- Adverse reactions in a large group of patients over a longer period of exposure.
- Should the drug is allowed to be marketed?