Glaxo Sheds $7 Billion in Value After $5 Billion Tesaro Deal

(Bloomberg) -- GlaxoSmithKline Plc shares slumped the most in intraday trading since 2008, wiping about 5.7 billion pounds ($7.25 billion) off the drugmaker’s market value, after it agreed to buy Tesaro Inc. for $5.1 billion on Monday.

Bloomberg first reported Tesaro was looking to sell itself in November. An analyst at Piper Jaffray said at the time a deal would be a “headscratcher,” given the headwinds facing Tesaro’s drug Zejula, as well as an immuno-oncology portfolio “that is still not ready for prime time.” Glaxo’s $75 per share offer is a 62 percent premium to Tesaro’s Friday close.

Glaxo shares were down about 8 percent at 3:10 p.m. in London. Tesaro was up 59 percent at $73.77.

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