As you may have heard this summer, Biogen (NASDAQ: BIIB) is taking out a $1.5 billion-dollar loan to fund its acquisition of rare disease drug developer Reata Pharmaceuticals (NASDAQ: RETA) for $7.3 billion in cash. Buying Reata Pharmaceuticals will accomplish a couple of things for Biogen. First, it'll gain control of Reata's newly approved drug Skyclarys, which is the only medicine approved to treat Friedreich's ataxia.