Adverse Event Reporting

## Adverse Event Definitions

An **adverse event (AE)** is any untoward medical occurrence in a clinical trial participant, whether or not it is related to the study drug. This broad definition captures all negative health events during the trial period. An **adverse drug reaction (ADR)** is a subset where a causal relationship with the drug is at least reasonably possible.

A **serious adverse event (SAE)** meets any of these criteria: death, life-threatening condition, hospitalization or prolongation of hospitalization, persistent or significant disability, congenital anomaly, or any event requiring medical intervention to prevent one of these outcomes.

## Reporting Timelines

### Investigator to Sponsor

Investigators must report all SAEs to the sponsor within 24 hours of awareness. Non-serious AEs are reported according to the protocol-defined schedule, typically at each study visit.

### Sponsor to Regulatory Authority

The sponsor must report unexpected and related fatal or life-threatening SAEs to the FDA within 7 calendar days (with a follow-up within 8 additional days). All other unexpected and related SAEs must be reported within 15 calendar days. Annual safety reports (Development Safety Update Reports, DSURs) provide comprehensive safety summaries.

### Sponsor to Investigators and IRBs

Sponsors must notify all participating investigators and their Institutional Review Boards of any safety information that could affect participant safety or willingness to continue participation.

## Causality Assessment

Investigators assess the relationship between the adverse event and the study drug using categories:

- **Unrelated**: Clear alternative explanation; no temporal relationship
- **Unlikely**: Alternative explanation more likely; weak temporal relationship
- **Possible**: Temporal relationship exists; alternative explanation equally likely
- **Probable**: Strong temporal relationship; no obvious alternative
- **Definite**: Clear temporal relationship confirmed by rechallenge or specific testing

## Severity Grading

The Common Terminology Criteria for Adverse Events (CTCAE) provides a standardized five-grade system: Grade 1 (mild), Grade 2 (moderate), Grade 3 (severe), Grade 4 (life-threatening), Grade 5 (death). Severity and seriousness are independent -- a Grade 1 AE (mild rash) can be an SAE if it requires hospitalization.

## MedDRA Coding

All adverse events are coded using the Medical Dictionary for Regulatory Activities (MedDRA), which provides standardized terminology across a five-level hierarchy from System Organ Class down to Lowest Level Term. This enables consistent safety data aggregation across trials and sponsors.

## Key Takeaways

- All adverse events are captured, regardless of suspected relationship to the drug
- Serious adverse events must be reported to sponsors within 24 hours
- Fatal or life-threatening SAEs require regulatory notification within 7 days
- Causality assessment ranges from unrelated to definite
- Standardized coding (MedDRA) and grading (CTCAE) enable cross-trial comparison