The S&P 500 rose 0.25% to 1,869.57 in afternoon trading Monday.
The Dow Jones Industrial Average was up 0.18% to 16,437, while the Nasdaq was up 0.45% to 4,113.94.
The yield on a 10-year Treasury bond was down 0.70% to 2.70%.
The price of gold slipped 0.41% to $1,288.60 per ounce.
Newport Beach-based patent licensing company Acacia Research Corp. was off about 10% to $15.41 for a market value of $744.75 million. The company reported disappointing first-quarter results after market close on Thursday, prior to the Good Friday holiday.
Anaheim-based drug maker Questcor Pharmaceuticals Inc. was up about 2% to $78.43 for a market value of $4.61 billion. The company said Monday that results from an investigator-initiated clinical study of its core drug H.P. Acthar Gel was proved to be "potentially useful therapy" for patients with the kidney disorder nephrotic syndrome.