Clinical Trials and Results

Did you know it takes on average ten years to develop a new medicine?

And preparing a candidate medicine or vaccine for clinical trials takes two to four years. The process starts first with:

  • a scientific understanding of a disease
  • identification of a "target," a gene or protein associated with the disease in focus
  • selection of the most active, yet safest substances to provide treatment, relief or prevention

After preclinical development, clinical trials are conducted on the candidate medicine or vaccine. Clinical trials, like vaccine trials, are carried out in phases, starting from phase I through phase IV.

Only after successful completion of the phase trials and approval by regulatory authorities can a new medicine be allowed access to the general population.

What is a clinical trial?

A clinical trial (also called clinical study) is any research that tests a new medicine, procedure, or device on humans to assess its effect on health.

In the case of a new medicine, the chemical compound is compared either to a placebo (a substance with no pharmacological activity) or to existing treatments. This comparison will determine whether the candidate medicine is more or less effective.

Clinical trials are carried out in phases, starting from phase I through phase IV. During the phase trials the optimal dose regimen and efficacy are discovered. Unwanted effects, as well as the nature and frequency of side effects are also determined.

Sanofi clinical trials and results

Details of on-going and completed phase I to IV clinical trials run by Sanofi are available to view on public websites (i.e. and

Results of Sanofi clinical trials are published on public websites (including and  and peer reviewed journals.

Our data sharing commitments

Sharing data with research communities is part of our long history. In July 2014, we further extended our data sharing activities and endorsed the Principles for Responsible Sharing of Clinical Trial Data.

Clinical trials: phases I-IV explained

Phase I

Typically, phase I trials are the first clinical trials in humans, performed using a small number of volunteers. It is normal to have several phase I trials, each answering different questions about the drug, such as:

  • How safe it is
  • How the drug is absorbed, distributed, broken down and removed from the body
  • What the drug does to the body
  • If it interacts with other medicines
  • How is it handled by different people like the elderly, certain ethnic groups and people with liver and kidney disease

Phase II

Is carried out in a small number of patients, approximating 200, to detect any meaningful therapeutic activity (efficacy) of the drug. Its safety is also checked.

Additional phase 2 trials can then decide which dose of the drug will work best whilst continuing safety assessments.

Phase III

Phase III trials can have patient numbers ranging from 500 to 1000. The aim is to gather enough information to satisfy regulators that the drug is fit for use as a treatment by the general population.

Phase IV

Phase IV trials are conducted across very large patient numbers sometimes exceeding 10,000. Their objective is to confirm the treatment effect and safety profile remain the same and cost-effective.

United by purpose

MAT-XU-2400404 (v1.0)

March 2024