AstraZeneca has filed a lawsuit in New Jersey, USA in a bid to stop Canadian drugmaker Apotex from marketing its generic version of the asthma drug Pulmicort Respules.

The Anglo-Swedish drugmaker is seeking a declaration of patent infringement a week after the US Food and Drug Administration granted approval for a copycat version of Pulmicort Respules (budesonide inhalation suspension) to Apotex. AstraZeneca is heading to the courts as a result of Apotex’s “indication of intent” to market its generic in the USA prior to patent expiry there. Patents covering Pulmicort Respules expire in 2018 with paediatric exclusivity extending to 2019.

Additionally, AstraZeneca has asked the judge in New Jersey to grant a “motion for interim relief”, ie an order that would block Apotex from selling its generic product until the patent case is concluded. The court will hear oral arguments regarding the motion on April 16.

AstraZeneca said that it has “full confidence in the strength of its intellectual property rights” protecting the treatment “and will continue to vigorously defend and enforce” them. Full-year US sales for Pulmicort reached $982 million in 2008 and about 90% of that total is accounted for by Pulmicort Respules.

The court battle with Apotex comes just a few months after AstraZeneca entered into a settlement with Teva Pharmaceutical Industries concerning Pulmicort Respules. The Israel-headquartered firm started shipping its generic product in November before being hit by a temporary restraining order in the same New Jersey court that will be looking at the Apotex case.

AstraZeneca made plans for its own authorised generic to be shipped by Par Pharmaceuticals. However, an agreement was reached whereby Teva agreed that it will not resume selling its budesonide inhalation suspension product until December 15 this year and then only under an exclusive licence granted by AstraZeneca which will receive a “significant undisclosed royalty” on sales of Teva's product.

However, there would be “a marked step down in payments” if additional at-risk generic products enter the marketplace.