AstraZeneca has filed a lawsuit to prevent the US Food and Drug Administration (FDA) from approving the sale of generic versions of Crestor, its multi-billion-dollar cholesterol drug. Crestor’s initial patent protection ended on Jul. 8 but the drugmaker recently won a seven-year extension for a rare pediatric indication – homozygous familial hypercholesterolemia (HoFH), a rare genetic disorder which causes very high cholesterol in children – and now wants to extend this for all uses.

The British-Swedish drugmaker has applied for a temporary court order to stop the FDA from allowing more “copycat” versions to hit the market until a final decision on Crestor’s exclusivity is taken. The drug currently provides AstraZeneca with annual revenues of more than $5 billion, with more than half of sales in the US, but this figure could plummet if generic versions flood the market.

US patents for the drug are due to expire in January 2021 with pediatric exclusivity until July 2021.

Senator and presidential candidate Bernie Sanders along with other US representatives have written to the FDA urging the regulator to approve the queue of applications to sell generic versions of the statin, highlighting the potential to drastically cut healthcare costs. They argue that AstraZeneca’s legal wrangling is a blatant attempt to block generic competition and maximize profits.

Separately, AstraZeneca has settled patent litigation with Sandoz relating to a generic version of Faslodex, its breast cancer drug. On Jul. 12, a federal court in New Jersey entered a consent judgment filed by AstraZeneca and Sandoz which includes an injunction that prevents Sandoz from launching a generic version until Mar. 25 2019, or earlier in some circumstances.

Faslodex is AstraZeneca’s top-selling oncology product with sales of $704 million in 2015. The company is expecting even more sales of the drug after the FDA cleared its use with Pfizer’s Ibrance in March this year. The combined therapy would treat women with advanced or metastatic breast cancer.