The UK pharmaceutical giant, AstraZeneca, has had a rough few weeks both at home and abroad. The pharmaceutical and medical device industries are still reeling from the Brexit vote that created a massive cloud of uncertainty for the future of AstraZeneca and many other UK-based healthcare companies.

In the US, AstraZeneca has come under scrutiny for its heartburn medication, Nexium, which has been shown to cause chronic kidney disease and kidney failure. More recently, the Center for Disease Control and Prevention (CDC) recently advised doctors not to administer AstraZeneca’s FluMist nasal spray vaccination because its effectiveness falls well below traditional flu shots.

But the stakes are highest for AstraZeneca with the soon to be expired exclusivity for its best selling drug, Crestor. Crestor is a medication helping patients manage cholesterol levels, and it’s a big money maker for AstraZeneca. Crestor earns AstraZeneca $7 million in sales every day; if generic versions of the drug are allowed onto the market, the company will lose billions in revenue to cheaper alternatives.

But AstraZeneca isn’t ready to let go of exclusive marketing rights without a fight. The company recently received approval for a new use of the drug to treat a rare condition in children called homozygous familial hypercholesterolemia or HoFH. Because HoFH is considered a rare or orphan disease, approval for treating HoFH also grants AstraZeneca an additional seven years of marketing exclusivity for Crestor in treating HoFH specifically.

AstraZeneca then used this new approval to file a lawsuit against the Food and Drug Administration (FDA), alleging allowing generics into the market would illegally broaden uses for generic versions of Crestor. Generic versions of Crestor will not have prescribing information for HoFH, 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 and have disastrous consequences for patients.

But lawmakers aren’t fooled. Senator Bernie Sanders sent a letter to the FDA encouraging the approval of generic versions of Crestor. Senator Sanders, among many others, believe allowing AstraZeneca additional years of exclusivity would prevent millions of Americans from getting lower cost generic equivalents just so the company could maintain profits.

AstraZeneca has ruffled many feathers with the lawsuit, but the stakes are incredibly high for the company. With so much uncertainty in the European market, losing the battle with generic competitors could spell disaster for the company.