Shares of Valeant Pharmaceuticals tumbled on Tuesday after the company cut its 2016 revenue forecast by about 12 percent and said a delay in filing its annual report could pose a debt default risk.

The stock closed down more than 51 percent on Tuesday.

One of its big investors, Bill Ackman, said he is still confident in Valeant and he plans to be more proactive in his dealings with it. However short seller Andrew Left of Citron Research told CNBC’s “Fast Money” on Thursday that the price drop in Valeant is a reflection of the problems with the company’s business model.

“If you look at what we saw today, really it was an unwind of the whole platform strategy, how Valeant goes about repairing their business. … How are they going to make these franchises more valuable than when they acquired them without having to raise prices? That’s obviously difficult,” Left explained.

Bill Ackman at the New York Stock Exchange.

Brendan McDermid | Reuters
Bill Ackman at the New York Stock Exchange.

For the full year, the company expects earnings of $9.50 to $10.50 a share. Revenue was seen at $11 billion to $11.2 billion, compared with its previous estimate of $12.5 billion to $12.7 billion.

The Canadian drugmaker, the target of U.S. investigations into its business and accounting practices, reiterated that it would put off filing its annual report with U.S. regulators but for the first time raised the specter of a default.

Valeant said failure to file the report by Tuesday’s deadline would mean it would be in breach of a covenant, and that holders of at least 25 percent of any series of notes may deliver a notice of default. Defaulting on debt could prompt lenders to demand faster repayment and place restrictions on Valeant’s ability to borrow further.

Left added that from the intraday move on Tuesday, it’s clear the market is pricing in the possibility of a default. With that said Left said he’s not tempted to buy or short the stock here.

“There has to be better places for me to deploy my capital. At the end of the day, Valeant is a black box,” he said.

As of Sept. 30, Valeant had about $30 billion of long-term debt. The company said it would repay at least $1.7 billion this year, down from an earlier forecast of $2.25 billion.

However, Chief Executive Officer Michael Pearson said he was “comfortable” with the company’s liquidity and expected Valeant to meet obligations.

“Our business is not operating on all cylinders, but we are committed to getting it back on track,” said Pearson, who returned last month from a medical leave of absence.

Valeant, which has rapidly expanded in recent years through acquisitions, is now looking to sell noncore assets, Pearson said, without being specific.

The company said last month it would delay filing its annual report while a board committee looked into its accounting practices. It also said it would restate 2014 and 2015 financial statements.

Valeant’s troubles began late last year when questions were raised about its drug pricing and allegations emerged that it was using distributor Philidor RX Services to inflate revenue in its dermatology business.

Laval, Quebec-based Valeant has since cut ties with Philidor, which has gone out of business.

Valeant is under investigation by the U.S. Securities and Exchange Commission over its relationship with Philidor, Reuters has reported. The company is also the subject of U.S. state investigations for steep price increases on some drugs.

The company posted fourth-quarter adjusted earnings per share of $2.50, compared with $2.58 a share in the year-earlier period. Revenue for the quarter came in at $2.79 billion, hurt by softer-than-expected sales in its gastrointestinal business.

Analysts had expected Valeant to report adjusted earnings of about $2.61 a share on $2.75 billion in revenue, according to a consensus estimate from Thomson Reuters.

The embattled company also reduced its first-quarter and full-year outlook. Valeant now forecasts first-quarter earnings of $1.30 to $1.55 a share, on revenue of $2.3 billion to $2.4 billion.

It all comes as high drug prices have been central to rhetoric from presidential hopefuls like Hillary Clinton.

Ackman sent an email to investors on Tuesday saying the board of hisPershing Square Holdings will take a more proactive role at Valeant given the new guidance. The letter also said that Pershing Square Holdings sees value in the pharmaceutical company and will protect its investment in Valeant.

“We continue to believe that the value of the underlying business franchises that comprise Valeant are worth multiples of the current market price,” Ackman wrote in the email. “Getting to those values, however, will require restoration of shareholder confidence in the management and governance of the company.”