Access to an unapproved drug for a seriously ill patient who has no other options—granted on a case-by-case basis outside of clinical trials.Compassionate use (expanded access) is a regulatory pathway allowing patients with serious or life-threatening conditions to access investigational drugs outside clinical trials when no comparable alternative exists. In the US, FDA grants expanded access through individual patient INDs, intermediate-size programs, or treatment INDs. For peptide therapeutics, compassionate use data occasionally provides human exposure data for compounds not yet in formal Phase I trials, though such data lacks the controls needed for efficacy assessment.