U.S. Stocks Retreat After Early Gains

New York — U.S. stocks fell Friday, led by biotechnology companies amid concern about government scrutiny of drug prices, after the Standard & Poor’s 500 index rose to a record earlier in the session on optimism about the economy.

Gilead Sciences Inc. slid 4.6 percent and Biogen Idec tumbled the most since 2008 as lawmakers questioned Gilead about its $84,000 hepatitis drug. Symantec slumped 13 percent after firing its CEO. About 9.9 billion shares changed hands in the United States, the most since June, amid a quarterly event known as quadruple witching when futures and options contracts on indexes and individual stocks expire.

“It’s a combination of it being witching day, plus the continuation of uncertainty on the geopolitical front,” Chad Morganlander, a Florham Park, N.J.-based fund manager at Stifel Nicolaus & Co., which oversees about $150 billion of assets, said in a telephone interview. “That’s forced the traders to square their books going into the weekend. Days like this are typically volatile.”

The S&P 500 lost 0.3 percent to 1,866.52. The gauge climbed 1.4 percent last week and earlier on Friday rose above its previous intraday record reached March 7. The Dow Jones industrial average slipped 28.28 points, or 0.2 percent, to 16,302.77 after climbing as much as 125 points earlier.

Stocks erased earlier gains Friday after the S&P 500 reached levels it has repeatedly failed to surpass this month. Before Friday, its previous intraday high was 1,883.57, reached March 7, and the gauge touched 1,881.94 on March 6 and 1,882.35 on March 11.

The S&P 500 on Thursday recovered most of its drop from Wednesday when Federal Reserve Chair Janet Yellen said the central bank’s stimulus program could end this fall and benchmark interest rates could rise about six months later. Stocks gained Thursday as data on leading indicators and regional manufacturing fueled economic optimism, overshadowing concern that interest rates may rise in the middle of next year.

Three rounds of Fed stimulus and low interest rates have helped boost the equity gauge as much as 178 percent from a 12-year low as U.S. stocks enter the sixth year of a bull market.