Drug developer QLT (NASDAQ:QLTI) announced earlier today that the European Union has approved the six-month formulation of its hormone therapy Eligard.

Eligard reduces hormone levels to slow tumor growth in early- and mid-stage prostate cancer sufferers. Since its approval in 2002, it has been marketed in various dosage strengths by QLT's partner Sanofi-Aventis (NYSE:SNY) in the U.S. and by Astellas in the European Union.

The six-month version of the drug has been on the market in Germany since last year, but only the one- and three-month versions had been approved for use in the rest of the EU before yesterday. Astellas will be able to begin marketing the higher-strength, longer-lasting dose in the other 23 countries once it negotiates formal reimbursement costs of the drug in each individual EU country.

One of the principal benefits of Eligard is its dosing, which is more convenient than some competing treatments from competitors like Abbott Laboratories (NYSE:ABT). This means fewer trips to the doctor, thus saving patients or their insurers money, so approval for this six-month formulation will have a meaningful effect on sales.  

The six-month formulation of Eligard is already on the market in the U.S. The drug experienced 70% year-over-year worldwide sales growth to $86 million in the first six months of 2007, although some of that growth is related to favorable comps from a temporary suspension of sales last year because of a patent fight. Earlier in the year, QLT settled this U.S. patent fight for $113 million, although there are still outstanding lawsuits in Germany.

At the end of the second quarter, QLT raised its Eligard sales guidance for the year by $20 million on both sides of its range, to $160 million to $180 million in 2007 sales. With sales of its age-related macular degeneration treatment, Visudyne, in the dumps, it's impossible to understate just how important Eligard is to QLT.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has formulated a long-lasting disclosure policy.