* Futures off: Dow 44 pts, S&P 6 pts, Nasdaq 14.5 pts
By Chuck Mikolajczak
NEW YORK, Sept 23 (Reuters) - U.S.-listed shares of Tekmira Pharmaceuticals were climbing on Tuesday, up 8.9 percent at $25.70 as one of the most actively trades Nasdaq stocks as its Ebola drug will be one of several to be tested in West Africa in a bid to win fast-track trials.
Volume of nearly 170,000 places the stock among the top three most actively traded shares on the Nasdaq before the opening bell and represents about 5 percent of its 10-day average.
Tekmira shares rose more than 17 percent on Monday after U.S. and Canadian regulators authorized the use of its Ebola treatment in patients who have confirmed or suspected infections from the deadly virus.
Shares of AbbVie were down 4.6 percent at $55.99 in premarket trading after the Obama administration took several actions late Monday that will reduce the tax benefits available to companies that have done inversion deals, while also making new inversions more difficult to do and potentially less rewarding.
Consolidated volume of nearly 400,000 made AbbVie the most actively traded issue on the New York Stock Exchange and represented about 3.1 percent of its 10-day average.
AbbVie has agreed to a deal to acquire Shire, which fell 5.5 percent and was also among the most actively traded Nasdaq names.
U.S. stock index futures were moving lower on Tuesday, putting the S&P on track for a third straight decline, as conflict in the Middle East intensified and after the U.S. Treasury moved to curb "tax inversion" deals.
The United States and Arab allies bombed Syria for the first time on Tuesday, killing dozens of Islamic State fighters and members of a separate al Qaeda-linked group, pursuing a campaign against militants into a war at the heart of the Middle East.
Data expected on Tuesday includes the flash September reading on manufacturing from financial data firm Markit at 9:45 a.m. (1345 GMT). Expectations call for a reading in the main purchasing managers' index of 58 versus the final 57.9 in August.
Salix Pharmaceuticals was trading up 9.3 percent at $174.76 in the premarket after a person familiar with the matter said on Monday that Allergan Inc had revived discussions to buy the company.
Norway's Yara and Chicago-based CF Industries are in talks about a merger of equals that could create a $27 billion global fertilizer producer, rivaling Canada's Potash Corp in size in a fragmented and oversupplied market.
* S&P 500 e-minis were falling 6 points, or 0.3 percent, with 174,767 contracts changing hands.
* Nasdaq 100 e-minis were down 14.5 points, or 0.36 percent, in volume of 28,821 contracts.
* Dow e-minis were down 44 points, or 0.26 percent, with 24,277 contracts changing hands.
Reporting by Chuck Mikolajczak; Editing by Lisa Von Ahn