What protein's function does lipitor primarily target?

What protein does Lipitor target?

Lipitor's active ingredient, atorvastatin, binds to and inhibits HMG-CoA reductase. This enzyme catalyzes the rate-limiting step in cholesterol synthesis inside liver cells.

How does atorvastatin inhibit HMG-CoA reductase?

Atorvastatin resembles the natural substrate HMG-CoA. It binds competitively to the enzyme's active site, blocking conversion of HMG-CoA into mevalonate. The inhibition lowers intracellular cholesterol levels, which auslöses compensatory mechanisms that pull LDL receptors to the surface of hepatocytes.

What triggers the LDL-lowering effect?

Once more LDL receptors appear on the liver surface, they clear circulating LDL particles from the blood. The process reduces serum LDL cholesterol by 40-60% at usual doses.

Why are companies challenging this patent?

Lipitor's original compound patent expired in 2011, but later patents covered specific salt forms and formulations. Generic manufacturers filed Paragraph IV challenges against these follow-on patents, triggering litigation that ended in settlements rather than full court rulings.

When does exclusivity expire?

The final U.S. exclusivity periods on Lipitor formulations ended around 2012-2013. Since then, dozens of generic versions of atorvastatin have entered the market.

Can biosimilars enter before patent expiry?

Atorvastatin is a small-molecule drug rather than a biologic, therefore biosimilar pathways do not apply.