Why Allergan (AGN) Stock Soared in After Market Trading Today

NEW YORK (TheStreet) -- Allergan  (AGN) soared in after-hours trading on Monday amid news that activist investor William Ackman and Valeant Pharmaceuticals International have joined forces to pursue a takeover of the health care company.

Ackman is the founder and CEO of hedge fund Pershing Square Capital Management, which has built an almost 10% stake in Allergan, according to CNBC. The company is worth approximately $4 billion.

Allergan closed at $142, an all-time high, and then surged 19% after the market closed. More than 9 million shares changed hands, more than triple the average volume of 2,944,310. 

STOCKS TO BUY: TheStreet Quant Ratings has identified a handful of stocks that can potentially TRIPLE in the next 12 months. Learn more.

AGN Chart

AGN data by YCharts

STOCKS TO BUY: TheStreet Quant Ratings has identified a handful of stocks that can potentially TRIPLE in the next 12 months. Learn more.

Editor's Note: Any reference to TheStreet Ratings and its underlying recommendation does not reflect the opinion of TheStreet, Inc. or any of its contributors including Jim Cramer or Stephanie Link.

If you liked this article you might like

Jim Cramer: Drug Stocks on the Move

Jim Cramer: Drug Stocks on the Move

Allergan Exec on Medical Aesthetics: 'The Future Is About Market Expansion'

Allergan Exec on Medical Aesthetics: 'The Future Is About Market Expansion'

Cramer: 10 Stock Surprises

Cramer: 10 Stock Surprises

Purdue Pharma to Downplay Opioids, Dump 50% of Sales Staff

Purdue Pharma to Downplay Opioids, Dump 50% of Sales Staff

Generic Drug Makers Hurt By Latest Federal Government Budget

Generic Drug Makers Hurt By Latest Federal Government Budget