AstraZeneca announced Tuesday that the company filed a lawsuit against the FDA seeking to overturn the agency’s recent decision rejecting two Citizen Petitions for Seroquel (quetiapine). The drugmaker said it “will vigorously defend its legal rights.”

The company wants an injunction barring the regulator from granting final marketing approval of generic versions of the immediate-release form of Seroquel until December 2, when regulatory exclusivity expires on certain clinical trial data, or until a federal court has “a meaningful opportunity to review imminent FDA action regarding the pending generic marketing applications.” AstraZeneca filed the two petitions last year asking that generic versions of Seroquel contain similar warnings to the branded versions about blood sugar levels and possible suicide.

Generic versions of the immediate-release product are due to be launched in the U.S. on March 26 when AstraZeneca’s patent expires. Panmure analyst Savvas Neophytou said that the drugmaker’s chance of overturning the FDA ruling is a “low probability event,” adding that “if the company is successful in keeping generics out until 2 December, it would result in around 15 percent EPS upgrades to consensus. Some will view this as a windfall.”

Seroquel generated annual revenue of $5.8 billion last year.