The S&P 500 climbed 0.1% in midday trading to 2,391.03.
The Dow Jones Industrial Average rose 0.1% to 20,936.86.
The NASDAQ was flat at 6,092.57.
The yield on a 10-year Treasury bond fell 1% to 2.30%.
The price of gold increased 0.1% to $1,256.
Aerie Pharmaceuticals Inc. in Irvine fell 3.8% to $42.20 and $1.4 billion market cap. The developer of eye care drugs is scheduled to report first-quarter earnings after the close of business today.
Irvine-based ChromaDex Corp., a maker of ingredients for dietary supplements and other products, jumped 16% to $3.72 and a $141 million market cap. The shares have climbed about 60% since last week when the company said Hong Kong investor Li Ka-shing, the wealthiest person in Asia, would buy up to $25 million of its common stock in a private placement.