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Table 2 Study phase classification scheme for drug trials and non-drug trials

From: Impact of investigator initiated trials and industry sponsored trials on medical practice (IMPACT): rationale and study design

Phase of drug trial/non-drug trial Classification criteria
1/S Safety study
Question: “Is the therapy safe?”
The trial focuses on the safety of a drug/therapy. The aim is to determine a safe dose range as well as the most common and serious adverse events associated with the drug/therapy. It is conducted with a small number of healthy participants.
2/A Pilot, feasibility, tolerability study
Question: “Is there a therapy effect?”
The trial is explicitly defined as a pilot study or feasibility study or it can be assumed from the description that the therapy is either new or has never been investigated with regard to a specific outcome. The clinical trial collects initial data on drug/ treatment efficacy, i.e. whether or not a drug/treatment works in a specific study population, while continuing to monitor drug safety as well as short-term adverse events.
3/B Efficacy study
Question: “How large is the therapy effect?” or “Is the effect larger than the effect of other therapies?”
Investigation and comparison of efficacy and safety under controlled conditions. The drug/therapy has already been tested, but more information is needed to establish the therapy. The clinical trial delves deeper into the safety and efficacy of a drug/treatment using different study populations, drug/treatment dosages, and combinations with other established drugs/treatments.
4/C Effectiveness study
Question: How can the effect be improved?
Effectiveness and safety under real-life condition. The drug/therapy is approved for marketing/established, but needs to be optimized, implemented in practice and evaluated over a longer time period under routine conditions. Additional information on the safety, efficacy and/or optimal use of a drug/therapy is collected.