After-hours buzz: Baxalta, SunEdison & more

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Check out the companies making headlines after the bell Thursday:

Baxalta shares fell more than 5 percent after the company announced a special shareholders meeting on May 27 to vote on its merger with Shire.

Ensco shares fell nearly 5 percent after the company announced that it will begin a public offering of 50 million Class A ordinary shares. The offshore drilling company intends to use the proceeds for "general corporate purposes."

Ixia shares sunk more than 14 percent after the company reported preliminary first quarter results below estimates. The company now expects first quarter revenue of $108 million to $111 million compared to a FactSet estimate of $123.3 million.

"Our topline performance was primarily impacted by an unexpected and marked slowdown in network test spending ... and we continued to experience delays in closing network visibility deals," said Bethany Mayer, Ixia's president and CEO.

Shares of Viacom climbed about 1 percent after a judge denied a request to depose Sumner Redstone as a part of a lawsuit that challenges his mental competency.

SunEdison shares swung back and forth on heavy volume after its internal investigation failed to find material misstatements in its past financial statements.

— Reuters and CNBC's Tae Kim contributed to this report.