Early movers: BIIB, XRX, MSFT, AMZN, SBUX & more

These are the stocks posting the largest moves before the bell.

Check out which companies are making headlines before the bell:

Biogen (NASDAQ: BIIB)'s stock was under pressure ahead of the bell after the company's first-quarter sales of Tecfidera, an oral multiple sclerosis drug, came in at $824.90 million, below consensus estimates, according to Reuters.

Xerox (NYSE: XRX) shares fell more than 3 percent after the company posted quarterly earnings and revenue that missed analysts' expectations. The company also cut its full-year forecast amid a strong U.S. dollar.

AstraZeneca (London Stock Exchange: AZN-GB) shares fell more than 3 percent in premarket trading after the company reported that sales fell by 6 percent in the first quarter, citing a rising dollar and competition from Nexium generics, according to Reuters.

American Airlines (NASDAQ: AAL) posted first-quarter profits that topped Wall Street's expectations. Diluted earnings per share for the airline came in at $1.73, while analysts expected $1.71. Nevertheless, the company also reported a 1.7 percent year-over-year drop in revenue, citing a strong dollar and competitive capacity growth, according to Reuters.

Amazon (NASDAQ: AMZN)'s stock soared more than 10 percent ahead of the bell as investors continued digesting Wednesday's news that its Web services sector generated revenue of $1.57 billion last quarter.

Microsoft (NASDAQ: MSFT) shares rose more than 3 percent in premarket trading as investors kept cheering the company's latest quarterly earnings report.

Google (NASDAQ: GOOGL) shares rose more than 3 percent in premarket trading despite having reported first-quarter earnings and revenue that fell short of Wall Street's expectations. The company posted earnings per share of $6.57 and revenue of $17.26 billion, with analysts expecting $6.60 earnings per share and $17.50 billion in revenue.

Starbucks (NASDAQ: SBUX) rose more than 4 percent before the bell as the company carried over momentum from Thursday's quarterly earnings report. The coffee giant posted second-quarter earnings per share of 33 cents, in line with expectations, and revenue of $4.56 billion, above Wall Street's estimates. Global same-store sales also rose 7 percent.

Goldman Sachs (NYSE: GS) reiterated its "buy" rating on Cisco Systems (NASDAQ: CSCO) and added the stock to its Conviction list, citing upside to fiscal-year 2016 "from an emerging product cycle in campus switching and enterprise WLAN, driven by the move to 802.11ac Wave 2, which requires an upgrade to multi-gigabit switching speeds."

J.P. Morgan downgraded Best Buy (NYSE: BBY)'s stock from "overweight" to "neutral" citing a "slow start" to this year's sales and a growing dependency on "the topline/gross profit dollar expansion."

Comcast (NASDAQ: CMCSA) could drop its bid for Time Warner Cable (NYSE: TWC) as soon as Friday, a source told CNBC.

(DISCLOSURE: Comcast is the parent company of NBCUniversal and CNBC.)

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