Why It's Fierce: Idenix Pharmaceuticals is letting no dust settle on its feet. Between the time it was shortlisted for the Fierce 15 and today's issue, the company launched its IPO amid tough market conditions. Clearly, Idenix's top brass feel they have a good story to tell. The company has zeroed in on new treatments for hepatitis B, hepatitis C, and HIV. Last May, Idenix announced that its first clinical trial of the experimental NM283 achieved a spectacular mean viral load reduction of 92% in adult patients with chronic hep C within 15 days of treatment. And they tackled one of the toughest strains of the virus: HCV genotype 1, the most common in the U.S. A whopping 87% of their patients had previously failed interferon-based therapies. Big financial commitments from Swiss drug group Novartis give Idenix the resources to complete its ambitious development plan.

What to look for: Combo trials involving NM283 and pegylated interferon over a four-week treatment period and longer trials in the last half of the year.