Ackman's Pershing Square Holdings saw returns for its main fund tumble 13.5 percent net of fees in 2016.
Attorney Jay Clayton sought to assure his congressional vetters that he'll act only in the public interest and will show no favoritism.
Democrats on the Senate Banking Committee raised concerns about his professional ties to Wall Street.
Chipotle Mexican Grill said four of its 12 directors would not stand for re-election to the burrito chain's board at its shareholder meeting in May.
The hedge fund reported that it bought 3 million more shares on Tuesday, increasing its stake to about 5.2 percent.
The "Fast Money" traders look at stocks owned by Pershing Square CEO Bill Ackman.
Marc Levine, Illinois State Board of Investment chairman, discusses why he decided to pull money from hedge funds, in the wake of Bill Ackman exiting out of Valeant.
Charley Grant, Wall Street Journal, shares his outlook on Valeant following Bill Ackman's pullout from the company. With CNBC's Meg Tirrell.
Valeant's stock dropped Tuesday, after news surfaced Monday that the billionaire hedge fund manager sold his remaining shares.
CNBC's Scott Wapner and Jim Cramer take a look at the state of activist investing following Bill Ackman's exit from Valeant.
CNBC's Leslie Picker takes a look a Bill Ackman's other not-so-successful trades in the wake of his pullout from Valeant.
Valeant plunges following Bill Ackman's decision to sell his entire position. Discussing the potential ripple effect for hedge funds with Bethany McLean, Vanity Fair contributing editor, and Herb Greenberg, Pacific Square Research.
CNBC's Meg Tirrell takes a closer look at the history of Bill Ackman's involvement in Valeant.
David Maris, Wells Fargo senior analyst who once called Valeant’s sharp fall, discusses what Bill Ackman's exit means for the future of the company.
Valeant sinks as Pershing Square's Bill Ackman throws in the towel. Karen Firestone, Aureus Asset Management, and Kourtney Gibson, Loop Capital president, weigh in.
CNBC's Leslie Picker takes a look at Bill Ackman's stock-picking history, including winners and losers.
"Fast Money Halftime Report" trader Josh Brown weighs in on Valeant, as the stock plunges following Bill Ackman's decision to sell his entire stake.
In a Trump market it's just a disaster, says "Squawk on the Street's" Jim Cramer discussing Bill Ackman's huge loss in Valeant with David Faber.
Hedge fund investor Bill Ackman is throwing in the towel on his pharma bet on Valeant, reports CNBC's David Faber.
Sources said Ackman sold his 27.2 million shares at around $11 each.