Portola Pharmaceuticals Inc., of South San Francisco, priced its underwritten public offering of about 8 million shares of common stock at a price to the public of $28 per share. Underwriters of the offering have been granted a 30-day option to purchase up to about 1.2 million more shares. The deal is expected to close Friday. Goldman Sachs & Co. LLC, Citigroup, Cowen, and William Blair are acting as joint book-running managers. Oppenheimer & Co. Inc. is serving as lead manager.