What do “Phase 1”, “Phase 2” or “Phase 3” studies mean?

The development of new drugs takes place in various phases of clinical trials that build on each other. In an early development phase, the focus is on the tolerability (phase 1) of a new drug in healthy individuals and patients. In the next step, the first indications of possible efficacy (phase 2) are determined. Once the tolerability studies (phases 1 and 2), in which 50-200 ALS patients participate, have been successful, extensive efficacy studies (phase 3) follow, in which several ALS centers and 200-700 ALS patients are usually involved. The studies follow a defined protocol that is drawn up by the drug manufacturer and reviewed and approved by drug authorities and ethics committees.