On Tuesday, shares of Valeant Pharmaceuticals plunged and closed down 51%. This cost Bill Ackman and his Pershing Capital a $1 billion loss in a single day. Following the massive loss, Ackman said to take more role in the company.

Valeant Pharmaceuticals filed its unaudited earnings report for the fourth quarter on Tuesday instead of annual comprehensive overview. The report did not ease the investors concern and continuous delay to its mandatory filing may result a default risk.

Following the report, the company's stock was slashed down to half of its value to $33.54 a share in Tuesday trading. The loss cut a stagerring $35.50 off each share. For Bill Ackman and his Pershing Square which own 30,711,122 of the company's shares, that is equal to a paper loss of $1.09 billion.

Bill Ackman started purchasing Valeant in February last year at the cost of $161 a share.

However, the activist investors said to take more active role in Valeant Pharmaceuticals. In his short letter on Tuesday, as cited by USA Today he said, "We continue to believe that the value of the underlying business franchises that comprise Valeant are worth multiples of the current market price." He signed the short letter as Bill.

"Getting to those values, however, will require restoration of shareholder confidence in the management and governance of the company." Furthermore he stated, "We are going to take a much more proactive role at the company to protect and maximize the value of our investment."

Pershing Square is the third-biggest shareholder of Valeant with 9% shares, including 6.3% of the outstanding common shares. Last week, senior partner and vice chairman of Pershing Square Stephen Fraidin has joined Valeant's board.

After a staggering loss in Valeant, Bloomberg reported Pershing Square Holdings Ltd has lost 26.4% this year through March 15. The firm was caught in the controversy surrounding Valeant Pharmaceuticals which caused the drugmaker to be under investigation from many agencies from Congress, attorney's offices and the Securities and Exchange Commission.

In an attempt to regain its loss, Pershing Square sold his biggest investment in Mondelez International Inc. after the market closed. Wall Street Journal reported the hedge fund sold its 20 million shares in Mondelez which yield $834 million at current prices. Pershing Square still own 5.6% of the Oreo maker.

The year 2016 has not started well for Pershing Square as two of its investment has given a big loss to the hedge fund. Aside from Valeant, its investment in Platform Specialty Products Corp has also went down, as the chemical maker's shares plunged by 35% this year.

Following a huge slump in Valeant Pharmaceutical stocks on Tuesday, Pershing Capital has lost more than $1 billion. However Bill Ackman said to stick to Valeant and take more active role in the drugmaker.