US STOCKS-Futures flat, few incentives to buy; S&P 500 off record

* Biotech stocks edge up, continuing recent rally

* Digital Ally (NasdaqCM: DGLY - news) gains before bell, has tripled this month

* Futures up: Dow 22 pts, S&P 2.5 pts, Nasdaq 6 pts

By Ryan Vlastelica

NEW YORK, Aug 26 (Reuters) - U.S. stock index futures were little changed on Tuesday, with investors finding few reasons to buy after a rally in the previous session that took the S&P 500 above 2,000 for the first time.

* The S&P failed to hold that level on Monday, though the benchmark index ended at a new closing high. Equities have rallied lately, with both the Dow and S&P advancing in seven of the last 10 sessions, while the Nasdaq has climbed in eight of the last 10 trading days.

* That momentum is still considered intact, and the S&P's price-to-earnings ratio is within historical norms, leading many analysts to believe the market is not overvalued. Nonetheless, further gains may be a challenge without positive catalysts and amid potential headwinds such as a reduction in Federal Reserve stimulus and a simmering conflict between Ukraine and Russia.

* Much of the market's recent gains have come on low volume, suggesting many traders may be reluctant to jump in at current levels.

* S&P 500 e-mini futures rose 2.5 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average e-mini futures added 22 points and Nasdaq 100 e-mini futures added 6 points.

* Biotechnology stocks were among the biggest drivers during Monday's rally. That appeared to continue Tuesday, with Achillion Pharmaceuticals (NasdaqGS: ACHN - news) up 6.1 percent to $11.44 before the opening bell. Gilead Sciences Inc (NasdaqGS: GILD - news) rose 0.6 percent to $108.13.

* Shares (Frankfurt: DI6.F - news) of Best Buy Co Inc fell 4.7 percent to $30.50 in premarket trading after the electronics retailer reported lower second-quarter revenue and forecast a drop in same-store sales in the second half of the year.

* Digital Ally Inc jumped 6.4 percent to $13.30 in premarket trading, extending a recent surge that has seen shares of the wearable camera maker more than triple this month alone. The recent fatal police shooting of an unarmed black teenager in Missouri has fueled interest in the company's devices. The stock was the Nasdaq's heaviest premarket mover.

* Amazon.com Inc late Monday agreed to buy the live-streaming gaming network Twitch Interactive for about $970 million in cash.

(Editing by Bernadette Baum)