Bill Ackman goes to Congress

Hedge fund billionaire Bill Ackman will testify before the United States Senate on Wednesday, answering questions about his relationship with Valeant Pharmaceuticals.

Ackman sits on the board of the embattled company, and is one of its major shareholders. In 2014 he helped Valeant with its failed bid to acquire Allergan Pharmaceuticals.

Valeant's outgoing CEO, Michael Pearson, and its former interim CEO, Howard Schiller will also testify before the Senate Committee on Aging.

The hearing has been scheduled since December, when the committee called on Valeant and three other pharmaceutical firms to answer for their drug pricing practices. At that point, Valeant had been under government scrutiny for some time, and that combined with accusations from a short seller sent the company's stock down around 70%.

The government is most concerned with Valeant's business model. The company pioneered the practice of using tax inversions to lower costs, cutting research and development, and growing through acquisitions.

"This year alone, Americans are expected to spend more than $328 billion on prescription drugs," said the Aging Committee in a statement. "Of this amount, individuals will pay about $50 billion out-of-pocket. The federal government will pick up another $110 billion in payments through Medicare, Medicaid, Veterans Affairs, and other programs."

The hearing starts at 3:30 PM EST.