Check out which companies are making headlines before the bell:
Comcast – Comcast offered to buy British broadcaster Sky for $31 billion, in a challenge to 21st Century Fox. The NBCUniversal parent's per-share offer is about 16 percent higher than Fox's prior agreement to buy the portion of Sky that it doesn't already own. NBCUniversal is the parent of CNBC.
Toll Brothers – Toll reported better-than-expected earnings and revenue for its first quarter, as the luxury home builder sold more homes at higher prices. Orders for new homes rose nearly 20 percent from a year earlier.
Discovery Communications – The TV network operator beat estimates by 6 cents a share, with adjusted quarterly profit of 47 cents per share. Revenue also beat forecasts as U.S. ad sales increased. Discovery also received Justice Department clearance for its planned purchase of Scripps Networks Interactive.
Palo Alto Networks – Palo Alto reported adjusted quarterly profit of 86 cents per share, 7 cents a share above estimates. Revenue also topped expectations. The cybersecurity company's results were helped in part by a surge in sales of its firewall protection software.
Fitbit – Fitbit reported a loss of 2 cents per share for its latest quarter, compared to analyst expectations of a breakeven quarter. Revenue also fell below estimates for the maker of wearable fitness devices, and the company also gave lower-than-expected guidance as newly launched products fall short of initial projections.
SeaWorld Entertainment – The theme park operator lost 24 cents per share for its latest quarter, five cents wider than expected, but revenue did beat Street forecasts. SeaWorld also announced that CEO Joel Manby is stepping down, to be succeeded on an interim basis by current Chief Parks Operations Officer John Reilly.
Microsemi – Microsemi is in advanced talks to be bought by Microchip Technology, according to both The Wall Street Journal and Reuters. The potential deal that would unite the chipmakers is said to be roughly in the mid-$60s per share, although sources say there is no guarantee a transaction will be finalized.
American Airlines – American and Qantas are trying to a second time to gain U.S. regulatory approval for a joint venture to coordinate prices and schedules. An initial request was rejected in 2016 after rivals Hawaiian Airlines and JetBlue objected.
Broadcom – Broadcom's pursuit of rival chipmaker Qualcomm is being examined by CFIUS, the inter-agency panel that examines deals for possible national security concerns, according to sources who spoke to Reuters.
Toyota Motor – Toyota has developed a magnet which reduces the use of the rare earth metal neodymium in electric car production. The new technology would save on production costs as well as cut the risk of a materials supply shortage.
Akorn – Akorn's deal to be bought by German health-care group Fresenius is in doubt, because of a Food and Drug Administration probe into data integrity at Akorn. Fresenius said it was conducting its own investigation into alleged breaches by the U.S.-based maker of liquid generic drugs.
Xerox — Activist investor Darwin Deason is seeking to nominate a new Xerox board, as he and fellow investor Carl Icahn continue to oppose a takeover by Japan's Fujifilm.
Apple – Apple is rolling out new primary care health-care clinics for its own employees, according to several sources.
United Parcel Service – UPS is suing European regulators for blocking its $7 billion acquisition of Dutch delivery company TNT Express in 2013. Following that rejection, TNT was bought by UPS rival FedEx.
Delta Air Lines – Delta has been threatened with the loss of Georgia-based tax breaks, after discontinuing discounts for members of the National Rifle Association. Lt. Gov. Case Cagle said the lawmakers would strike down a $50 million sales tax exemption if Delta did not restore the discounts.
Tenet Healthcare – Tenet beat estimates on both the top and bottom lines, with the hospital operator also raising its 2018 forecasts. Tenet's results were helped by an increase inpatient admissions.
Nutrisystem – The diet systems provider reported adjusted quarterly profit of 42 cents per share, beating estimates by 2 cents a share. Revenue also came in above forecasts. The company also raised its dividend by 43 percent to 25 cents per share, however shares were coming under pressure because of a lighter-than-expected 2018 forecast.
Mallinckrodt – The U.K.-based drugmaker earned an adjusted $2.01 per share for its latest quarter, beating the consensus estimate of $1.69. Revenue was also above consensus.