TEAEs

Treatment-emergent adverse events (TEAEs) are adverse events that arise or worsen after the initiation of a study treatment in a clinical trial. TEAEs are distinguished from adverse events that were present at baseline or before treatment, which are not counted as TEAEs unless they change after dosing begins. They are typically collected during the treatment period and coded using standardized medical terminology, such as MedDRA, and categorized by system organ class and preferred term. The counting window for TEAEs varies by protocol but commonly includes events occurring from the first dose through a defined period after the last dose (for example, 28 days). TEAEs are graded by severity, and investigators may assess relatedness to the study drug, although causality is not established by observation alone.

In reporting, TEAEs are summarized by treatment group to characterize safety and tolerability. Serious TEAEs (those meeting criteria for serious adverse events) are reported separately. TEAEs can influence trial conduct, including dose interruptions, dose reductions, discontinuation, or withdrawal. Common TEAEs often reflect the drug’s safety profile and may differ across therapies.

Interpretation notes: TEAEs indicate temporally associated events during treatment and do not prove causality. Their frequency depends on trial population, concomitant medications, and follow-up duration. Regulatory assessments use TEAE data to evaluate the risk-benefit balance and to inform labeling and post-marketing surveillance.