Stocks making the biggest moves premarket: Berkshire Hathaway, General Electric, Twitter & more

Check out the companies making headlines before the bell:

General Electric – GE announced the sale of its bio pharma drug unit to Danaher for $21.4 billion, including $21 billion in cash. GE plans to use the proceeds to reduce leverage and strengthen the balance sheet, and expects the deal to close during the fourth quarter of this year.

Newmont MiningBarrick Gold has made an all-stock offer to merge with its mining rival, following reports Friday that it was considering such a move. Newmont is currently in the process of acquiring smaller rival Goldcorp, but Barrick said this deal offers far superior value.

Berkshire Hathaway – Berkshire reported quarterly profit of $2.32 per share, above the $1.85 a share consensus estimate. Revenue came in below forecasts. In his annual letter to shareholders, Berkshire's Warren Buffett noted the difficulty in finding large acquisitions.

Kraft Heinz – Shares are staging a slight rebound after tumbling Friday on news of worse-than-expected earnings and a Securities and Exchange Commission investigation. During his appearance on Squawk Box, Warren Buffett said he and partner 3G Capital did not overpay for Heinz, but did overpay when Heinz acquired Kraft Foods.

Twitter – Twitter co-founder Evan Williams is stepping down as a member of the board at the end of February. Williams said he wanted to focus his time on other projects.

Spark Therapeutics – The drugmaker agreed to be bought by Switzerland's Roche for $4.3 billion or $114.50 per share in cash. The price is more than double Spark's Friday closing price of $51.56.

Kraft Heinz – Kraft Heinz has hired Credit Suisse to review options for its Maxwell House coffee business, according to people familiar with the matter who spoke to CNBC. The unit could fetch $3 billion or more in a sale.

Qualcomm – The chipmaker rolled a series of 5G networking chips for a wide range of uses including cars and home broadband. The product announcements came at the Mobile World Congress event in Barcelona.

Sony – Sony also made product announcements at the Mobile World Congress event, unveiling new smartphones with movie-style screens.

Caesars Entertainment – Caesars is in talks with Carl Icahn to offer him a role in selecting a new CEO for the casino operator, according to a Reuters report.

PG&E – The utility company will drop its plan to award $130 million in bonuses to employees, following protests from victims of California wildfires.

Norwegian Cruise Line – The stock was upgraded to "outperform" from "neutral" at Macquarie, which noted a reduce risk profile given strong bookings and the potential for a dividend later this year.