What are investigational compounds?

An investigational compound is a drug that is being actively developed through the clinical trial process but has not yet received regulatory approval for any indication. In the US, investigational drugs are administered under an Investigational New Drug (IND) application filed with the FDA; in the EU, under an equivalent Clinical Trial Authorisation.

Retatrutide is the current highest-profile example in this catalog. Its phase-2 data (Jastreboff 2023 NEJM in obesity, Rosenstock 2023 Lancet in diabetes) established that the compound produces large effects, but the phase-3 program is ongoing and approval has not yet been granted. Compounds in this position have real human safety data (from phase 1 and 2) and real efficacy signals (from phase 2), but the definitive phase-3 evidence has not yet been generated.

Investigational status is distinct from Research Use Only status. RUO compounds may never have entered formal clinical development at all — they are sold as research reagents outside the regulatory framework. Investigational compounds are inside the regulatory framework but have not yet reached the approval endpoint. The evidence tier for an investigational compound depends on how much phase-2/3 data has been generated at any given point.

When a compound page describes a compound as 'investigational', that framing carries specific meaning: the compound is in active regulated development, human evidence is emerging but not definitive, and future approval is possible but not guaranteed. Some investigational compounds succeed and reach approval; others fail phase 3 and are discontinued.