Even as PRA International explores a possible initial public stock offering, the clinical trials firm is also reportedly the target of private equity bidders who could buy the company for up to $1.3 billion.

Reuters reports that private equity firms KKR & Co., Warburg Pincus LLC and Cinven Ltd. are weighing bids for the Raleigh contract research organization. Reuters did not identify the sources, describing them only as “several people familiar with the matter.”

PRA last month filed a confidential draft registration statement with the Securities and Exchange Commission. That’s the document outlining the company’s possible IPO plans. PRA did not indicate either the number of shares to be offered or a price range for the offering. But the company did say that it would use proceeds from the proposed IPO to pay down debt as well as for working capital and corporate purposes.

Reuters said that KKR, Warburg Pincus and Cinven are among those preparing second-round bids later this month to acquire PRA. PRA is currently owned by another private equity firm, Genstar Capital, which acquired PRA in 2007 for $797 million. The sources told Reuters that Genstar would pursue the private equity offering if the private equity bidders fail to meet price expectations. PRA’s value of $1.3 billion is based on annual earnings before interest, tax, depreciation and amortization of about $130 million, the sources said.

PRA has about 5,000 employees worldwide. The CRO, founded in 1976, relocated its headquarters from Virginia to Raleigh in 2008.