Orexigen Therapeutics Inc. on Monday set the terms of its pending initial public offering at 6 million common shares with an estimated price range between $11 and $13 a share.

The San Diego biopharmaceutical company has granted the underwriters an option to purchase up to 900,000 additional shares to cover overallotments, the company said in an amended prospectus filed with the Securities and Exchange Commission.

Existing stockholders have invested a total of $76.05 million into the company at an average share price of $4.03, according to the filing. The company's major stockholders include: Domain Associates, with a 21.3% stake, which will become 16.2% after the offering; KPCB Holdings, with a 20% stake that becomes 15.1% post-IPO; Sofinnova Venture Partners VI LP, with a 15% stake that becomes 11.4%; Scale Venture Partners II LP, with a 14.8% stake that becomes 11.3%; Montreux Equity Partners, with 7.4% which becomes 5.6%; and Morgenthaler Partners VII LP, with a 5.9% stake that becomes 4.5% after the offering.

The company's market capitalization is estimated at $322 million, based on the higher end of the estimated price range and 24.8 million shares expected to be outstanding after the offering.

Merrill Lynch & Co., J.P. Morgan, JMP Securities and Leerink Swann & Co. are listed as underwriters for the offering.

The company said it expects to use the net proceeds from this offering to fund clinical development of its product candidates and for working capital and other general corporate purposes.

The company said it expects to list its stock on the Nasdaq Global Market under the symbol OREX.