Development: from the molecule to the medicine
- Stage 1
Produce a sufficient quantity of the selected molecule (active substance) while following a certain number of quality criteria such as purity.
- Stage 2
Test the drug candidate to evaluate its efficacy and undesirable effects (preclinical studies).
Study the fate of the medicine in the body and its interactions with the body, particularly its efficacy (pharmacology) and possible toxicity (toxicology).
- Stage 3
Make it possible to administer the drug in a suitable form (capsule, tablet, solution for injection, patch, syrup, suppository, cream, etc.) by combining the active substance with excipients.
Continue to monitor closely the undesirable effects and try to optimize the doses that will be administered in the first clinical trials.
- Stage 4
Test the medicine in humans (if the preclinical steps are satisfactory) in the form of clinical trials.
Phase I - Evaluating safety and pharmacokinetics
The study is conducted in a small number of healthy volunteers (who do not have the disease), with a very gradual increase in doses; the subjects are closely monitored by teams that are specialized in this kind of study.
The aim is:
- to evaluate the product’s pharmacodynamic effects in humans;
- to evaluate the safety of single doses and repeated doses and thus to establish the safety threshold for treatment (maximum safe dose in humans).
Phase II - Determining the product's safety in patients with the disease
Phase IIa: this is carried out in a small number of patients and makes it possible to determine if the medicine is active against the targeted disease, and therefore to decide whether to continue with development. It is a key phase in the life of the product.
Phase IIb: this makes it possible:
- to determine the best dose to use, i.e. one that ensures the best efficacy with the minimum amount of undesirable effects,
- to continue to evaluate the undesirable effects, as is the case in all stages of development.
Phase III- Evaluating safety and efficacy in conditions that resemble current practice
Phase III studies are conducted in a large number of patients (between several hundred and tens of thousands) in conditions that represent normal practice. They make it possible to establish the benefit/risk ratio of the medicine in the targeted indication on a large scale and over a long period, and to determine the precautions for use. A dossier may then be submitted to the health authorities in order to obtain a Marketing Authorization (MA).
Phase IV - Further studies after approval
After the MA is granted, Phase IV studies monitor the medicine’s safety and efficacy profile, evaluating its effects in specific subgroups of patients that were not studied before or comparing it with new reference drugs. This phase takes place alongside monitoring of the product’s safety by pharmacovigilance programs.