(Reuters) - Billionaire investor John Paulson, whose hedge fund firm is the biggest owner of Valeant Pharmaceuticals International Inc VRX.TOVRX.N shares, on Monday joined the ailing drug company's board as it restructures to repay debt.

FILE PHOTO: A sign for the headquarters of Valeant Pharmaceuticals International Inc is seen in Laval, Quebec June 14, 2016. REUTERS/Christinne Muschi/File Photo

Investors appeared to see Paulson’s becoming a director as a vote of confidence in Valeant, sending its U.S.-listed shares up 5.1. percent at $13.29.

The move comes as Valeant sells off assets to pay down its $30 billion debt. “With his significant business and financial expertise, John will be a strong addition to the board,” Valeant Chief Executive Officer Joe Papa said in a statement. “His experience will be especially valuable as we continue to execute on our transformational strategy to turnaround Valeant.”

The 61-year old Paulson, best known for a bet against the overheated housing market that earned his firm $15 billion in 2007, has not served on many corporate boards. He is currently a director at insurer American International Group Inc AIG.N, which recently removed its CEO.

A Paulson spokesman declined to comment.

Paulson & Co, owns 19.4 million shares, or 5.7 percent of Canada-based Valeant. His firm, like many other hedge funds, has suffered heavy losses as Valeant’s stock price plummeted some 96 percent since mid-2015 after it became embroiled in an accounting scandal and was investigated for hefty price hikes. The stock price is still 80 percent off its peak.

Paulson will be the second investor along with Robert Hale, a partner at hedge fund firm ValueAct, to sit on the 11-person board that was overhauled a year ago by activist investor William Ackman, who was long the company’s biggest public supporter.

Ackman recruited Papa after firing former CEO Michael Pearson who grew Valeant into one of the hedge fund industry’s most widely owned companies.

Paulson will work with Papa and other board members to narrow Valeant's focus to its dermatology, gastrointestinal and eye care businesses and sell off other assets. In November talks to sell Salix, one of its crown jewels, to Japanese company Takeda 4502.T fell apart.

A few months later in March, Ackman abruptly sold his position and exited the board but not before the Valeant investment cost his firm, Pershing Square Capital Management, some $3 billion in losses.

Valeant has also taken a bite out of Paulson’s performance. His firm’s assets, which had $36 billion in assets at its peak in 2011, have shrunk to roughly $10 billion with Paulson’s personal assets making up the bulk of the capital.

Last year Paulson Partners Enhanced merger arbitrage fund tumbled 50 percent before falling further in early 2017.

Also, a string of employees have been leaving. Most recently, portfolio manager Sheru Chowdry, who co-managed the Paulson Credit Opportunities Fund along with Ty Wallach, said he would leave.