* More cars and trucks sold in November than analysts expected
* Otsuka to buy Avanir; Cypress Semi to buy Spansion
* Biogen rallies on expansion of Alzheimer's drug testing
* Indexes up: Dow 0.4 pct, S&P 0.5 pct, Nasdaq 0.4 pct (Updates prices, changes byline)
By Rodrigo Campos
NEW YORK, Dec 2 (Reuters) - U.S. stocks rose on Tuesday, led by gains in the energy sector, and as Biogen rallied on news about an experimental treatment for Alzheimer's disease.
The day's gains were broad, with nine of the 10 S&P 500 industry sectors higher. The only group to fall was telecoms , down 1.6 percent with AT&T down 2.1 percent and Verizon down 1.5 percent. Sprint announced it will cut in half the monthly price of service for Verizon and AT&T customers who switch to Sprint.
Energy shares on the S&P 500 rose 1.6 percent even as crude oil prices resumed their fall. U.S. crude fell 2.6 percent to near a five-year low while Brent lost 2.2 percent.
Exxon Mobil and Chevron were among the largest gainers on both the Dow and the S&P.
At 2:42 p.m. (1942 GMT) the Dow Jones industrial average rose 94.27 points, or 0.53 percent, to 17,871.07, the S&P 500 gained 12.43 points, or 0.61 percent, to 2,065.87 and the Nasdaq Composite added 26.75 points, or 0.57 percent, to 4,754.09.
Carmaker shares advanced as the top six automakers sold more cars and trucks in November than analysts expected. GM gained 1.5 percent to $33.42 and Fiat Chrysler gained 2.6 percent to $13.05.
Biogen Idec Inc advanced 5.7 percent to $326.07. Its research chief said the company is planning a late-stage trial of its experimental treatment for Alzheimer's disease after the drug significantly improved cognition in a small early-stage study.
Avanir Pharmaceuticals was among the most traded stocks on the Nasdaq, rising 12.8 percent to $16.92 as Japanese drugmaker Otsuka Holdings plans to buy it for about $3.5 billion.
Cypress Semiconductor Corp added 12.2 percent to $11.70 after it said it will buy peer Spansion Inc for $1.59 billion in stock. Spansion shares rallied 19.1 percent to $27.21.
Advancing issues outnumbered declining ones on the NYSE by 2,023 to 1,034, for a 1.96-to-1 ratio; on the Nasdaq, 1,820 issues rose and 866 fell for a 2.10-to-1 ratio.
The S&P 500 was posting 79 new 52-week highs and 5 new lows; the Nasdaq Composite was recording 97 new highs and 81 new lows. (Reporting by Rodrigo Campos; Editing by Nick Zieminski)