The private equity firm has been working with JPMorgan Chase & Co and Evercore Partners Inc to find a buyer for the Montreal-based drugmaker in a sale process that has been under way for several months, said the sources, who asked not to be named because the matter is confidential.

A number of potential buyers, however, thought TPG's asking price of more than $3 billion was too high and decided not to bid, and it remains unclear if there will be a deal, two of the sources said.

Raleigh, North Carolina-based Salix Pharmaceuticals and Indian drugmaker Sun Pharmaceutical Industries Ltd are among the companies that passed on bidding after taking a look, the sources said.

Representatives for TPG, Aptalis and Sun Pharma did not immediately respond to requests for comment. Salix, JPMorgan and Evercore declined to comment.

TPG, one of the most active private equity investors in the healthcare space, bought the drugmaker, formerly known as Axcan Pharma, for $1.3 billion in 2008 and merged it with Eurand Pharmaceuticals in 2011. The combined company was renamed Aptalis.

The specialty pharmaceutical company has a number of drugs that treat cystic fibrosis and gastrointestinal disorders and sells the products primarily in North America and Europe.

In the fiscal 2012 year, Aptalis was projected to have $615 million in revenues and $269 million in adjusted earnings before interest, tax, depreciation and amortization (EBITDA), according to its website.

The exploration of a potential sale comes at a time when there has been a flurry of deals in the pharmaceutical space over the past few months.

In July, U.S. drugmaker Perrigo Co agreed to buy Ireland-based Elan Corp for $8.6 billion. Earlier this year also saw Actavis Inc's $5 billion acquisition of Dublin-based Warner Chilcott Plc, as well as the $8.7 billion takeover of eye care company Bausch & Lomb Holdings by Valeant Pharmaceuticals International.

(Reporting by Jessica Toonkel and Soyoung Kim in New York; Editing by John Wallace and Andrew Hay)

By Jessica Toonkel and Soyoung Kim