Also pushing prices lower were weak economic news and ongoing concern that the Federal Reserve will soon begin scaling back its economic stimulus.
The Dow Jones industrial average (^DJI) fell 64 points, or 0.4 percent, to 14,946, the Standard & Poor's 500 index (^GPSC) lost 6 points, or 0.4 percent, to 1,656 and the Nasdaq composite index (^IXIC) dipped fractionally to 3,657.
Amgen surged nearly 8 percent, the biggest gain in the Standard & Poor's 500 index, after the biotech giant said it plans to buy Onyx Pharmaceuticals for $10.4 billion.
In another drug deal, AstraZeneca agreed to privately held U.S. biotech company Amplimmune for up to $500 million. The move is a way for AstraZeneca to boost its pipeline of cancer-fighting drugs. Shares of AstraZeneca (AZN) fell 0.4 percent to $50.47
In economic news, the government reported that orders for long-lasting manufactured goods plunged 7.3 percent last month, the steepest drop in nearly a year. Demand for commercial aircraft sank and businesses spent less on computers and electrical equipment.
The Federal Reserve is to start a two-day meeting Sept. 17 at which officials will discuss easing Fed support for the economy. Congress returns from vacation next week and will have to take up a new budget before the new fiscal year starts on Oct. 1.
More Stocks in the News:
- Anadarko Petroleum (APC) climbed 1.4 percent to $91.02. The oil and gas producer said late Sunday that it's selling part of its stake in a natural-gas site off the shores of Mozambique for $2.64 billion.
- Tesla Motors (TSLA), the electric-car maker, climbed 1.5 percent, to $164.22, following reports that, in California, Tesla's Model S outsold Cadillac, Porsche, Jaguar and other brands in June.
- Pratt & Whitney, a unit of United Technologies (UTX), is in a deal with the Pentagon to build engines for F-35 Joint Strike Fighters in a deal valued at more than $1 billion, according to sources familiar with the matter. Nonetheless, United Tech shares slipped 0.5 percent to $102.30.
- In another deal, the Pritzker Organization said it will acquire scrap metal broker TMS International (TMS) for $17.50 a share, a premium of about 12 percent to TMS's Friday close of $15.57. TMS shares gained more than 12 percent to $17.48.
- Standard & Poor's releases the S&P/Case-Shiller index of home prices for June and the second quarter at 9 a.m. Eastern time.
- The Conference Board releases the Consumer Confidence Index for August at 10 a.m.