Merck & Co. Inc. said Wednesday its board of directors approved the buyback of up to $5 billion in common stock for the drug developer's treasury.

The company, based in Whitehouse Station, N.J., said the program has no expiration. Overall, the company is now authorized to buy back up to $6.4 billion in common stock.

Merck has about 3.08 billion shares of common stock outstanding.

The move comes ahead of the company's scheduled release of its first-quarter financial results on Friday.

"Merck has a history of leadership in returning cash to shareholders," President and CEO Kenneth C. Frazier said in a statement. "Together with our strong dividend, today's action reflects our confidence in Merck's strategy and demonstrates our commitment to delivering shareholder value."

On Monday, the company's development pipeline got a boost when the Food and Drug Administration posted a review of the potential hepatitis C drug boceprevir. The review said the drug appears to cure more patients in less time than established drugs that have been used for 20 years. But the agency has questions about how the drug should be combined with older medicines for the maximum effect.

The agency is holding a public meeting Wednesday to consider whether to approve the drug candidate.

Shares of Merck closed at $35.06 Tuesday. The stock has traded between $30.70 and $37.68 over the past year.