It has been a busy couple of months for Rule Breakers pick BioMarin (Nasdaq: BMRN).

Shares are up more than 30% since the beginning of December after the company won FDA approval to market Kuvan, its enzyme replacement drug. BioMarin launched the drug in the U.S. in early January and says it could bring sales of $35 million to $70 million in 2008.

The wide-ranging forecast is partly because BioMarin doesn't know how many patients will respond to Kuvan, and partly because other factors affect how it's taken -- for example, the weight of patients, which affects the dosage. At the Wachovia health-care conference in Boston today, BioMarin said that both the average weight of patients and the doses they have been taking are tracking higher than expected, which is a positive sign for its sales potential. BioMarin estimates that 50% to 60% of the 13,000 patients in the U.S. with the underlying genetic disorder that Kuvan treats will respond to its use; it's charging $57,000 a year for the drug.

BioMarin filed a marketing application for Kuvan in the European Union in November. The company puts the number of people in the developed world with this genetic disorder at 50,000, and will start a phase 1 trial this quarter for another drug, dubbed Peg-Pal, that treats patients who aren't responding adequately to Kuvan. As with its rapid three-year development timeline for Kuvan, BioMarin plans to have Peg-Pal in phase 3 testing by the middle of 2009, if all goes according to plan.

BioMarin's other lead pipeline candidate, 6R-BH4 for a host of cardiovascular and other disorders, is expected to bring early and mid-stage clinical trial results in the second half of the year and through early 2009. In August, BioMarin also acquired the rights to a preclinical-stage cystic fibrosis drug program and expects to begin human clinical trials for the lead drug within two years.

BioMarin expects to finally become profitable in the second half of 2008, thanks to Kuvan and sales of its other two enzyme-replacement drugs, which are Aldurazyme, marketed by Genzyme (Nasdaq: GENZ), and Naglazyme. Look for full financial guidance when the company announces its fourth-quarter results on Feb. 26.

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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.