Clinical Trial Phases

Clinical trials are essential to determine whether new drugs, diagnostics or procedures in the laboratory are both safe and effective when used to diagnose or treat people.

Clinical research follows strict scientific standards to protect patients and help produce reliable study results. A clinical trial “protocol” outlines how the study is designed, including what types of patients are eligible to take part in the research in order to ensure that new approaches are tested on similar groups of people.  While eligibility criteria differ from trial to trial, factors such as age, gender, genetic markers, the type and stage of disease, previous treatments, and other health problems are often considered. In each part of the study, a goal - called an “endpoint” - is identified to determine whether the study has been successful, and the methodology for how the data will be analyzed.

The gold-standard is called a double-blind randomized control trial, in which patients are randomly assigned to two or more groups, with the “experimental” group receiving a potential new medicine and a “control” group receiving a placebo or an already approved treatment, to determine which approach is better to treat a given disease. The trial is called “double-blind” because neither the patients nor the doctors know who has been enrolled  each group until after the results have been assessed to eliminate bias.

Traditionally, clinical trials are broken into parts, called phases:

  • In Phase 1, researchers evaluate the safety of a new experimental compound in a small number of healthy volunteers or people who have exhausted all other treatment options.

  • Phase 2 studies test the potential treatment in a larger group of patients, looking further at the safety and efficacy of the medicine being investigated. In Phase 2 trials, different doses of the treatment are studied to determine the ideal dose to give patients.

  • Phase 3 expands the scope of study to test for safety and efficacy in hundreds or thousands of patients. In this phase, outcomes for those taking the new medicine are typically compared head-to-head with outcomes for those getting a placebo or the standard-of-care therapy.  Rigorous statistical tests are done to make sure that the demonstrated benefit is genuine.

  • Clinical studies can also include a Phase 4 option to identify and evaluate the long-term effects of treatments over a lengthy period for a greater number of patients, following regulatory approval.  

At Roche, we are committed to bringing innovative medicines to patients faster than ever before. Our Product Development team is working closely with governments and regulatory authorities around the world to reduce the amount of time it takes for our medicines to be approved and accessible to patients. This is part of our commitment to innovating the science of drug discovery and development.

To learn more about clinical trials or to find a Roche-sponsored study, visit our

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