Much of the past few months' investor excitement over BioMarin Pharmaceutical (Nasdaq: BMRN) has focused on its recently FDA-approved drug Kuvan. But on Monday, one of its enzyme replacement therapies, Naglazyme, made its own headlines by winning Japanese marketing approval.

Cracking the Japanese pharmaceuticals market is hard for almost any drugmaker, especially one as small as BioMarin. As it's done for Aldurazyme with Genzyme (Nasdaq: GENZ), and potentially Kuvan in the European Union, BioMarin will have a marketing partner, AnGes, sell Naglazyme in Japan.

Kuvan, Naglazyme, and Aldurazyme form BioMarin's triumvirate of drugs approved by the FDA (and likely soon the European Union). Revenue from the compounds is expected to reach $255 million to $306 million this year, after BioMarin brought in $122 million in revenue last year.

Despite securing U.S. marketing approval three years ago, Naglazyme's sales are still growing strongly, if more slowly than before. BioMarin has guided for $105 million to $116 million in Naglazyme net sales this year, up at least 22% over last year, after experiencing 56% year-over-year sales growth with the drug in the fourth quarter.

BioMarin also expects Kuvan to get approved in Japan this year, and it will receive a substantial "north of 20% royalty" on Japanese sales of the drug. Although it's easy to forget it, Japan represents the world's third-largest geographic pharmaceutical market, after the United States and the European Union. (It's the second-largest if you count the European countries individually.)

In its fourth-quarter earnings announcement earlier in the month, BioMarin didn't mention whether it had included Japanese approval of Naglazyme in its 2008 financial guidance. Still, given Japan's importance as a market for pharmaceuticals sales, the approval of Naglazyme and potentially Kuvan there could be a nice boon for BioMarin.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has an A+ disclosure policy.