Vicuron Pharmaceuticals' (NASDAQ:MICU) stock value has grown 20% in the past five days of trading, thanks to positive news surrounding its new "super-tough" antibiotic, dalbavancin. In Phase II trials, Vicuron's dalbavancin outperformed competitor vancomycin with response rates of 87% to 50%.

Vancomycin is the "antibiotic of last resort" in hospitals used treat tough bacterial infections resistant to penicillin-derived versions. However, even mighty vancomycin has been defeated by crafty superbugs bred by the overuse of antibiotics.

Vicuron's eyeing to grab a piece of the pie from vancomycin, which has annual sales in the $300 million range. Stiffening its competitive stance, dalbavancin is injected only once weekly, while vancomycin is injected twice daily.

In addition to this trial, which was centered on acquired bloodstream infections, Vicuron has dalbavancin in two Phase III trials for skin and soft tissue infections. In this application, the drug maker's competitor is Cubist Pharmaceuticals (NASDAQ:CBST), which has an already approved drug called Cubicin. However, Cubicin must be injected once daily compared to dalbavancin's once-weekly dosing.

Vicuron is not a one-trick pony, though. The company has filed a New Drug Application for their lead antifungal drug, anidulafungin. Vicuron faces some stiff competition in this market, with big pharma players like Pfizer's (NYSE:PFE) Diflucan (recently off-patent) and Vfend, along with Merck's (NYSE:MRK) Cancidas crowding the space.

These drugs are poised to generate about $1.5 billion in revenue, with more than $600 million coming from the newer Vfend and Cancidas. Fungal infections are a growing market, due to increasing numbers of immuno-compromised patients, and the market can most likely support another effective anti-fungal. At the same time, revenues will likely be closer to the $500 million mark at their peak, rather than the $1 billion mark that defines a blockbuster drug.

With the recent run-up, however, Vicuron is sporting an enterprise value north of $1 billion. Given the size of the markets and the many competing drugs, it is getting harder to justify those lofty heights.

David Nierengarten, Ph.D., works with a biotechnology venture capital fund. He often contributes to Fool.com and is an active member of the TMF community as DavidMN. He owns shares of Vicuron. He appreciates your comments at davidnierengarten@mac.com and on the Biotechnology discussion board.