April 21 (Reuters) - U.S. stocks rose slightly on Monday as investors found few reasons to push indexes sharply higher following a strong rally last week and ahead of key earnings releases. The Dow Jones industrial average was up 0.23 percent at 16,446.81, the S&P 500 was up 0.31 percent at 1,870.71 and the Nasdaq Composite was up 0.51 percent at 4,116.438.
** HALLIBURTON CO, $62.77, +3.07 pct
The world's No. 2 oilfield services company, reported better-than-expected quarterly results, helped by robust drilling activity in Russia, Saudi Arabia and Angola.
** SAREPTA THERAPEUTICS INC, $35.4304, +45.21 pct
** PROSENSA HOLDING NV, $5.2999, +4.53 pct
Sarepta said it would start new trials to revive the chance of approval for its experimental muscle disorder drug after the U.S. Food and Drug Administration advised the company to submit new safety and efficacy data.
Prosensa makes drisapersen, a competing drug that failed a late-stage trial in September 2012.
** PFIZER INC, $30.88, +2.08 pct
** ASTRAZENECA PLC, $67.967, +7.05 pct
U.S. pharmaceutical giant Pfizer has approached British rival AstraZeneca to propose a 60 billion pound ($101 billion) takeover, Britain's Sunday Times reported.
** PINNACLE ENTERTAINMENT INC, $23.595, +6.86 pct
Pinnacle Entertainment shareholder Orange Capital LLC said it had asked the casino operator to consider spinning off its real estate into a separately traded real estate investment trust.
** NVR INC, $1,081, -3.19 pct
The homebuilder's quarterly profit fell 32 percent and new orders were down 5 percent. Home closings during the quarter was also down 3 percent. Orders are a key indicator of the performance of builders as their revenue is recognized only after a house is handed over to the buyer.
** HNI CORP, $35.17, +4.86 pct
Raymond James on Monday raised its rating on the office furniture maker to "outperform" from "market perform" after the company on Wednesday reported a better-than-expected first-quarter profit helped by strong growth in its hearth division sales, and raised its full-year 2014 earnings outlook to a range of $1.70-$1.85 per share from Previous outlook of $1.60-1.80 per share.
** TARENA INTERNATIONAL INC, $7.731, +14.70 pct
The provider of IT education in China said It has signed a cooperation agreement with Bank of China Consumer Finance Co Ltd (BOCCFC). BOCCFC will offer student loans to Tarena students to assist them in paying for tuition fees, the company said.
** WALTER ENERGY INC, $7.195, -9.04 pct
** ALPHA NATURAL RESOURCES INC, $4.37, -0.68 pct
** ARCH COAL INC, $4.96, -1.00 pct
Analysts at Goldman Sachs reduced benchmark met coal price forecasts for 2014 to $133 per metric tonne from $141, citing an expected lackluster recovery in met coal prices.
** SEARS HOMETOWN AND OUTLET STORES INC, $23.41, +4.79 pct
Edward Lampert, the beneficial owner of the home appliance retailer, filed with regulators on Thursday to disclose a purchase of 173,574 shares of the company's stock at $20.62 each.
** PLUG POWER, $7.0596, -3.56 pct
** BALLARD POWER SYSTEMS INC, $3.96, +4.76 pct
The Canadian fuel cell maker said on Monday it had agreed to form a joint venture with South Korea's Hyundai Hysco Co Ltd , a steel supplier to Hyundai Motor, to develop and sell hydrogen fuel cells in Asia.
Shares of Ballard, one of the biggest clients Plug Power, were also up.
** KNOLL INC, $18.95, +3.67 pct
Raymond James raised its price target on the furnishings, textiles and fine leather maker's stock to $21 from $20 after the company reported better-than-expected quarterly results on Thursday. The brokerage also said it expects continued improvement in margins as Knoll increases its exposure to the high-end residential furniture industry.
Raymond James said it expects the company to also benefit from improved demand for office furniture throughout 2014 and into 2015.
** GASLOG LTD, $27.16, -3.14 pct
Analysts at brokerage firm Jefferies & Co downgraded the operator of liquefied natural gas carrier to "hold" as they expect the near-term liquefied natural gas shipping outlook to remain weak.
** AASTROM BIOSCIENCES INC, $4.36, +23.86 pct
The company said it agreed to acquire French drugmaker Sanofi SA's cell therapy and regenerative medicine business for $6.5 million, which will give it global commercial rights to three marketed autologous cell therapy products.
Revenues of the three products - Carticel, Epicel and MACI - were $44 million in 2013.
Aastrom will also acquire global manufacturing and production centers located in the United States and Denmark.
** WIPRO LTD, $13.25, -2.65 pct
India's third-largest software exporter's IT revenue forecast for the quarter ending June was seen as below estimates by some analysts. Wipro on Thursday said it expects IT services revenues to be in the range of $1.72 billion to $1.76 billion.
** MONEYGRAM INTERNATIONAL INC, $12.76, -13.84 pct
JMP Securities downgraded the world's second-largest money transfer company's stock to "market perform" after Wal-Mart Stores Inc said it would launch a domestic money transfer service.
Analysts said more than a third of MoneyGram's earnings were associated with Walmart-to-Walmart transactions. No direct costs could be cut if these transactions go to Wal-Mart's new service.
BofA Merrill Lynch lowered its target price on the stock to $19 from $23.
** CBEYOND INC, $9.83, +38.84 pct
** EARTHLINK HOLDINGS CORP, $3.84, +9.71 pct
Privately held enterprise Internet-based communications services provider Birch Communications Inc said it agreed to buy the data center and networking services provider Cbeyond Inc for about $323 million in cash to expand its optical fiber and data center network.
Cbeyond shareholders will get between $9.97 and $10 per share. At $9.97 per share, the offer represents a premium of 40.8 percent over the closing price of Cbeyond's stock on Thursday.
Shares of rival Earthlink Holdings also rose.
** ADVANCED MICRO DEVICES INC, $4.16, +12.74 pct
The chipmaker reported better-than-expected quarterly results on Thursday and its second-quarter revenue forecast was above analysts' estimates.
At least two brokerages raised their price targets on the stock on Monday.
** CALPINE CORP, $22.08, +3.32 pct
U.S. power and energy infrastructure owner LS Power Equity Advisors LLC said it has agreed to buy about 3,500 MW of generation resources in the southeastern United States from Calpine for $1.57 billion. The portfolio consists of six combined-cycle generation facilities which use natural gas as the primary fuel source, LS Power Equity said.
Calpine mainly owns and operates natural gas-fired and geothermal power plants in North America.
** NEWMONT MINING CORP, $24.83, +5.48 pct
The talks between Barrick Gold Corp and Newmont Mining over a combination that would create a gold mining behemoth have hit a snag, but two sources close to the situation say the companies remain keen on a deal and discussions are likely to resume.
** COMCAST CORP, $49.66, +1.14 pct
** CHARTER COMMUNICATIONS INC, $124.88, +5.98 pct
Comcast is in talks with Charter Communications over selling or spinning off roughly 3 million subscribers worth approximately $18 billion to $20 billion as part of the divestitures related to its $45.3 billion takeover of Time Warner Cable, according to a source familiar with the matter.
** VIMPELCOM LTD, $9.215, +2.39 pct
Russia's Vimpelcom has resolved a long-running dispute with the Algerian government by selling it a majority stake in the country's biggest telecoms operator for $2.6 billion, while it will keep control and slash debt.
** LULULEMON ATHLETICA INC, $48.55, -6.11 pct
A U.S. judge has issued final dismissals of lawsuits accusing Lululemon and various company officials of defrauding shareholders by concealing defects in yoga pants.
** ATHENAHEALTH, $138.07, -5.16 pct
The healthcare IT services company on Thursday reported first-quarter adjusted earnings and revenue that fell below Wall Street estimates.
Three brokerages, including Oppenheimer, Deutsche Bank and B. Riley cut their price targets on the company' stock, citing weakness in its Epocrates business - a mobile medical application.
** SELECT COMFORT CORP, $19.73, +11.15 pct
The specialty mattress maker on Thursday reported first-quarter sales that beat analysts' estimates, helped by a 2 percent rise in comparable sales.
** WEIBO CORP, $23.2, +14.62 pct
The Chinese Twitter-like messaging service company's U.S.-listed shares were up premarket on Monday after they soared 19 percent on their debut on Thursday.
** CHINDEX INTERNATIONAL INC, $23.68, +3.23 pct
Chinese drugmaker Shanghai Fosun Pharmaceutical Group Co Ltd has raised its offer for U.S.-listed Chindex International Inc by 15 percent to $223.6 million after a bidding war for the China-focused hospital chain.
** RADIOSHACK CORP, $1.44, +2.13 pct
The struggling U.S. electronics chain is mired in talks with its lenders over its plans to close about 1,100 stores, complicating its turnaround efforts, the Wall Street Journal reported, citing sources close to the talks.
RadioShack, which operates about 4,300 stores in the United States, said in March that the plan needed permission from its lenders, adding that its credit agreements allowed it to close only about 200 stores without the approval of lead lenders, the Journal said late on Wednesday. (r.reuters.com/vyg68v)
The company reported a wider quarterly loss and a huge drop in sales during the holiday season. (Compiled by Rohit T.K. in Bangalore; Editing by Joyjeet Das)