Biased Agonism

Biased Agonism designates the pharmacological phenomenon where different ligands activating the same receptor preferentially stimulate distinct downstream signalling pathways rather than activating all receptor-mediated signalling equally, enabling selective engagement of therapeutically beneficial pathways while avoiding pathways associated with adverse effects.

The pharmaceutical industry has embraced biased agonism as a drug design strategy particularly at G protein-coupled receptors where different signalling arms produce distinct physiological outcomes. Opioid receptor biased agonists favouring G protein signalling over beta-arrestin recruitment aim to provide analgesia while reducing tolerance and respiratory depression associated with balanced agonism. Angiotensin receptor biased ligands favouring beta-arrestin signalling may improve cardiovascular outcomes. Biased agonism complicates standard pharmacological characterisation requiring pathway-specific assays. As structural biology reveals the molecular basis of signalling bias, rational design of biased ligands continues advancing enabling pathway-selective therapeutic targeting with improved safety profiles.