The past 12 months should have been good ones for BioMarin Pharmaceuticals ( BMRN). So why have investors bailed on the stock? Last April, the Food and Drug Administration approved BioMarin's first drug, Aldurazyme, as a treatment for a rare genetic disorder. Before the end of the current quarter, the company is expected to release pivotal, phase III study results for a second drug, Aryplase, also to treat a rare genetic disease. If the data is positive, BioMarin will file Aryplase with the FDA in the second half of this year. Just last week, BioMarin purchased a profitable pediatric drug business from Medicis Pharmaceutical ( MRX) that includes an oral asthma medicine, Orapred, which is expected to generate about $42 million in sales this year. BioMarin says the deal is accretive immediately. Yet with all that, BioMarin shares are down 35% since last April, closing Friday at $6.92, just above its 52-week low. In this same time period, the Amex Biotech Index is up nearly 50%, with small-cap stocks similar to BioMarin performing better still. So what gives? Well, the Aldurazyme launch has not lived up to some lofty expectations for reasons that can't all be laid on BioMarin -- even if investors haven't seen it that way. But the Orapred purchase and the pending Aryplase data are positives, and should help BioMarin reach profitability faster. If the company follows through on its promises, the stock could head higher.