The S&P 500 was down 0.3% to 2,079.61 in midday trading.
The Dow Jones Industrial Average was up 0.4% to 17,896.40, and the Nasdaq was down 0.3% to 4,929.33.
The yield on a 10-year Treasury bond declined 1.4% to 1.94%.
The price of gold fell 0.2% to $1,182.
Tustin-based Peregrine Pharmaceuticals Inc. was up 4.3% to $1.44 and a $271 million market cap. The cancer drug developer said clinical data from a phase-1 trial for a potential breast cancer treatment showed “objective tumor response in 85% of patients.” About 2 million shares had traded hands compared with a full-day 90-day average of 1.2 million shares.