Take a look at some of the biggest movers in the premarket:

Hilton Grand Vacations (HGV) – The timeshare company posted a wider-than-expected loss for its latest quarter, while revenue was also below Wall Street forecasts. Hilton Grand Vacations said the pandemic has created a challenging environment but said 85% of its properties are now open and operating. Its shares fell 2.3% in premarket trading.

NRG Energy (NRG) – The energy provider reported better-than-expected profit and revenue for its latest quarter, and also said the financial impact of the extreme weather in Texas is expected to be within NRG’s current guidance range. The company’s shares jumped 5.5% in the premarket.

Perrigo (PRGO) – Perrigo shares initially jumped 4.1% in premarket action after the drugmaker announced a deal to sell its Generic Rx Pharmaceuticals business to private-equity firm Altaris Capital for $1.55 billion in cash and other considerations. The gains disappeared, however, after Perrigo reported lower-than-expected earnings for its latest quarter as sales fell.

Johnson & Johnson (JNJ) – J&J rose 2.1% in the premarket after its Covid-19 vaccine received emergency use authorization from the Food and Drug Administration over the weekend, followed by an endorsement from the Centers for Disease Control and Prevention. Administration officials say deliveries of the vaccine should begin Tuesday.

Berkshire Hathaway (BRK.B) – Berkshire reported a 23% increase in fourth-quarter profit to $35.8 billion, helped by a surge in the value of Berkshire’s stock market holdings. Berkshire also bought back nearly $25 billion in stock during 2020, with CEO Warren Buffett explaining in his annual letter that the move increased shareholder value while still leaving ample cash for other opportunities that might arise. Berkshire Class B shares rose 2.1% premarket.

Twitter (TWTR) – Twitter rose 1% in premarket trading after it announced its intention to sell $1.25 billion in convertible notes due in 2026, subject to market conditions.

Walmart (WMT) – The retailer dropped its $35 minimum charge for its two-hour express delivery service. However, the $35 minimum will still apply for regularly delivery, curbside pickup and Walmart+ delivery services. Walmart shares rose 1% in the premarket.

L3Harris Technologies (LHX) – The defense contractor struck a deal to sell its military training division to Canadian aerospace company CAE (CAE) for $1.05 billion. The deal will enhance CAE’s defense business.

Logitech (LOGI) – Logitech shares fell 1.5% premarket after it said operating income for fiscal 2022 would be between $750 million and $800 million, down from the $1.1 billion it expects to report for fiscal 2021. Logitech had seen a boom in demand for devices like computer mice and keyboards due to the pandemic, with more people working and attending school from home.

Twilio (TWLO) – Twilio is in talks to invest up to $750 million in messaging company Syniverse Technologies, according to people familiar with the matter who spoke to The Wall Street Journal. They said that the expected investment by the cloud communications company would value Syniverse – currently owned by private-equity firm Carlyle Group (CG) – at $2 billion to $3 billion. Twilio rose 2.3% in premarket action.

AstraZeneca (AZN) – The drugmaker sold its stake in Moderna (MRNA) for more than $1 billion, according to the London Times. The paper said the sale occurred after Moderna shares soared following approval of its Covid-19 vaccine, although the exact timing was unclear. Moderna shares rose 1.8% in premarket trading.

Vector Acquisition (VACQ) – The special purpose acquisition company will take space transportation startup Rocket Lab public through a merger deal that values Rocket Lab at $4.1 billion. The deal is expected to be completed during the second quarter. Vector shares surged 17.1% in premarket trading.

Wayfair (W) – The home goods retailer’s shares rose 2.1% in the premarket after Truist Securities upgraded the stock to “buy” from “hold,” saying it sees an improved picture for long-term profitability and a faster growth trajectory.

Catalent (CTLT) – The pharmaceutical technology company has been struggling with vaccine production problems, according to a report in the Financial Times. Catalent fills vaccine vials for both Johnson & Johnson and Moderna, and the report said issues with automation technology have meant that vials have had to be checked by hand.

Citigroup (C) – Citigroup shares rose 2.1% in premarket trading as Jane Fraser takes over as Chief Executive Officer of the bank today, becoming the first woman to run a major U.S. bank.