Aliskiren hemifumarate is a hemifumarate salt form of Aliskiren. Aliskiren is a direct renin inhibitor with an IC50 of 0.72?nM against renin. Renin is the first enzyme in the renin-angiotensin-aldosterone system which plays a role in blood pressure control. Renin cleaves angiotensinogen to angiotensin I, which is in turn converted by (ACE) to angiotensin II. Angiotensin II has both direct and indirect effects on blood pressure. It directly causes arterial smooth muscle to contract, leading to vasoconstriction and increased blood pressure. Angiotensin II also stimulates the production of aldosterone from the adrenal cortex, which causes the tubules of the kidneys to increase reabsorption of sodium, with water following thereby increasing plasma volume and blood pressure. Aliskiren binds to the S3bp binding pocket of renin, essential for its activity. Binding to this pocket prevents the conversion of angiotensinogen to angiotensin I. Aliskiren is also available as combin