Angiotensin Receptor Antibodies

The angiotensin receptor family comprises two class A G protein-coupled receptors, AT₁ and AT₂, encoded by AGTR1 and AGTR2, respectively, both of which are activated by angiotensin II. AT₁ is widely expressed in adult tissues, including vascular smooth muscle, the kidneys, adrenal glands, and heart, where it mediates vasoconstriction, aldosterone secretion, and renal sodium retention. It signals predominantly through Gq/11, and sustained activation can promote inflammation, fibrosis, and cardiovascular remodeling. Agonist-induced phosphorylation by G protein-coupled receptor kinases promotes β-arrestin recruitment, which contributes to AT₁ desensitization and internalization and can also initiate distinct signaling responses. AT₂ is widely expressed during fetal development and has a more restricted distribution in adults, where its activation can promote nitric oxide-dependent vasodilation and oppose some AT₁-mediated effects. The Mas receptor, encoded by MAS1, is a distinct GPCR associated with the ACE2–angiotensin-(1–7) axis, although direct activation of Mas by angiotensin-(1–7) remains debated. Selective AT₁ antagonists such as losartan, valsartan, and candesartan are used clinically to treat hypertension and, depending on the drug, heart failure or diabetic kidney disease. Intravenous angiotensin II is approved as a vasopressor for adults with septic or other distributive shock. The selective AT₂ agonist buloxibutid (C21) is being evaluated in a phase 2b trial for idiopathic pulmonary fibrosis, and no selective AT₂- or Mas-targeted drug is currently approved.