LONDON -- AstraZeneca's (AZN 5.25%) (AZN 0.49%) share price remains resiliently steady following news that the Federal Court of Australia has found three patents protecting Crestor -- AstraZeneca's rosuvastatin medication, for the treatment of high cholesterol -- to be invalid.

The company was quick to point out that the judgment is limited to Australia and has no impact on patents held elsewhere in the world. It also stated that it doesn't materially affect AstraZeneca's financial guidance for 2013.

Sales of Crestor in Australia during 2012 totaled about $350 million, and the patents were all due to run until at least 2020, so the company could potentially lose a large amount of revenue there if generic alternatives were available. The company said that it will be exploring all legal avenues open to it, which could include appealing the court's decision, or seeking to maintain existing injunctions.

The patent blow comes on the back of poor trading figures from the company at the end of January, when it announced that annual sales had slipped 17%, largely due to the loss of patent protection and exclusivity on some of its best-selling treatments, including Seroquel IR (a treatment for schizophrenia and bipolar disorder) and Nexium (a heartburn remedy).

And the problems seem set to continue to for some time, with the company already anticipating a mid-to-high single-digit percentage drop in revenue for 2013, with core earnings per share set to decline even more significantly, owing to higher core operating costs.

Despite all this, AstraZeneca remains a favorite of investment guru Neil Woodford, who has a remarkable track record of picking winners.

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