Liraglutide vs Exenatide

## Overview

Exenatide was the first GLP-1 receptor agonist approved (2005), derived from exendin-4 (Gila monster saliva peptide with 53% GLP-1 homology). Liraglutide is a GLP-1 analog with 97% GLP-1 homology. Exenatide is available as twice-daily (Byetta) or once-weekly extended release (Bydureon). Liraglutide is once-daily.

## Mechanism of Action

Both activate GLP-1 receptors. Exenatide's lower homology to human GLP-1 means different receptor binding kinetics and greater immunogenicity risk (more anti-exenatide antibodies than anti-liraglutide antibodies in clinical trials).

## Pharmacokinetics

Exenatide IR: half-life ~2.4 h, twice daily. Exenatide ER (Bydureon): microsphere depot, once weekly, complex release kinetics. Liraglutide: half-life ~13 h, once daily.

## Clinical Efficacy

LEAD trials (liraglutide): consistently superior HbA1c reduction compared to exenatide IR in head-to-head comparisons. DURATION trials (exenatide ER vs liraglutide): generally comparable but some showing liraglutide advantage. LEADER (liraglutide): positive CV outcome trial. EXSCEL (exenatide ER): neutral on CV events.

## Cardiovascular Evidence

Liraglutide (LEADER): 13% significant MACE reduction. Exenatide ER (EXSCEL): non-inferior to placebo (not statistically significant reduction). Liraglutide has a clear CV advantage over exenatide.

## Key Takeaways

- Liraglutide: 97% GLP-1 homology (less immunogenic), once daily, proven CV benefit
- Exenatide: 53% GLP-1 homology, first approved, BID or QW, no positive CV outcome data
- Liraglutide superior in efficacy and cardiovascular evidence