AstraZeneca has filed a lawsuit against the Food and Drug Administration (FDA) alleging new regulations would illegally broaden new uses for the generic versions its best selling cholesterol drug, Crestor. But before you praise AstraZeneca for trying to protect patients from the “substantial risks” the regulations would pose, it’s important to understand the company has a lot more at stake.

Crestor is used to treat high cholesterol, which can reduce the risk of heart attack, strokes, and other related conditions. It’s also AstraZeneca’s best selling drug, netting a whopping $5 billion in sales last year; but, the patent granting the company exclusive manufacturing rights expires July 8, 2016.

AstraZeneca has been preparing for the expiration. Last month, the company received FDA approval for a new use of Crestor. The drug can now be used to treat a condition in children called homozygous familial hypercholesterolemia or HoFH. The condition causes very high cholesterol and is extremely rare.

Under the Orphan Drug Act, drug manufacturers who obtain approval for a drug that treats a particularly rare or orphan disease will receive an additional seven years to exclusively market the drug for the treatment of that rare disease. This means AstraZeneca has the exclusive right to manufacture and market Crestor for the treatment of HoFH for seven years.

AstraZeneca’s labeling for Crestor will now include prescribing information and risks for treating HoFH, but generic versions of Crestor will not have the same labeling, and this is where the problem lies.

Doctors might choose to prescribe a patient with HoFH a generic version of Crestor, but the generic label won’t include prescribing information for the condition. AstraZeneca is contending this could lead doctors to prescribe incorrect dosages of the drug.

The intention of the lawsuit is to require generic versions of Crestor to contain the same labeling information. However, this would require generic versions to go through the approval process for treating HoFH, which will take years. If AstraZeneca succeeds, it will maintain a monopoly on Crestor while generic manufacturers go through the lengthy FDA approval process.