At the start of any new drug or vaccine lies an understanding of a disease, the identification of a target (therapeutic or vaccine) and a selection of the most active yet safest substances to provide treatment, relief or prevention. It takes two to four years of work to prepare a candidate drug or vaccine for development.

What is a Clinical Trial?

A clinical trial (also called clinical study) is any research that tests an intervention (normally a new drug, but can even be procedures and devices) on humans to assess effect on health. 

In case of a new drug, the compound or investigational product is compared either to a placebo (a substance with no pharmacological activity) or to existing treatments, to determine whether it is more or less effective.

Trials are carried out in phases, starting from phase I and all the way to phase IV, during which the optimal dose regimen, efficacy and unwanted effects, as well as the nature and frequency of side effects are determined.

Pharmaceutical companies such as Sanofi rigorously test new drugs for their safety, effect and quality in phase I to IV trials to enable access the general population.

Clinical Trials: Phases I to IV Explained

Phase 1

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

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

Phase 2

Is carried out in a small number of patients approximating 200 to detect any meaningful therapeutic activity (efficacy) of the drug whilst checking its safety.

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

Phase 3

Phase 3 trials can have patient numbers ranging from 500 to 1000 aiming to gather enough information to satisfy regulators that the drug is fit for use as a treatment by the general population.

Phase 4

Phase 4 trials are conducted across very large patient numbers sometimes exceeding 10,000 aiming to confirm the treatment effect and safety profile remains the same and cost effective.

Where does Sanofi disclose information on on-going 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.

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

Our Data Sharing Commitments

Sanofi believes that making clinical trial data available to the research community promises to advance science and medicine, contributes to improvements in public health and improves knowledge about and trust in pharmaceutical drug development.

The concept of sharing data for research purposes is not new for Sanofi. Our company has a history of contributing to initiatives where data sets are pooled for research purposes.

The pharmaceutical industry as a whole demonstrated its support for sharing of clinical data when in July 2013, the members of the Pharmaceutical Research and Manufacturers of America (PhRMA) and the European Federation of Pharmaceutical Industries and Associations (EFPIA) developed and endorsed a set of Principles for Responsible Sharing of Clinical Trial Data

Job bag number MAT-GB-2001220(v1.0)
Date of Preparation November 2020