In a move to bolster its anti-infective franchise, Pfizer ( PFE) said Thursday it would pay $1.9 billion in cash -- representing a gigantic premium -- to acquire Vicuron Pharmaceuticals ( MICU). Vicuron has two anti-infective drugs pending before the Food and Drug Administration, which should rule on both later this year. Pfizer's offer places a value on Vicuron's stock at $29.10 a share. The stock jumped to $27.53 on Thursday, adding $11.73 or 74.2%. The shares rose as high as $27.93 and easily vaulted past the 52-week high of $18.33. Pfizer's stock was off 4 cents to $28.39. The deal is expected to close during the third quarter, subject to regulatory approval and a vote by Vicuron's shareholders. Pfizer has four big anti-infective drugs that produced $4.72 billion in sales last year, representing 9% of corporate revenue. But one of those drugs, Diflucan, an antifungal, lost patent U.S. protection in July 2004 and is losing sales. Its $945 million in sales last year represented a 20% drop from 2003. An even bigger drug, the antibiotic Zithromax, will lose U.S. patent protection in November. Zithromax had worldwide sales of $1.85 billion last year, down 8% from 2003. The drug is most often used in treating respiratory infections. On Monday, the FDA approved Zmax, a one-dose version of Zithromax, as a treatment for mild to moderate acute bacterial sinusitis and community-acquired pneumonia in adults. The other Pfizer anti-infectives are Zyvox ($463 million in sales last year) and Vfend ($287 million in 2004 sales).