All three major US stock indexes were in the red in late-morning trading Monday, with the Nasdaq Composite leading the way down at over minus 3%, as the emergence of Chinese startup DeepSeek has sent shares of other artificial intelligence companies stocks tumbling.

In company news, shares of Nvidia (NVDA) and other AI companies were down meaningfully after the rapid rise of DeepSeek, which launched an open-source AI model that can possibly run on less-advanced chips. The DeepSeek application was ranked first on Apple's (AAPL) App Store over the weekend, Wedbush Securities said in a note Monday. Shares of Nvidia, OpenAI investor Microsoft (MSFT), Broadcom (AVGO) and Arm Holdings (ARM) were down 15.6%, 3.7%, 16.5% and 10.3%, respectively, around midday.

AT&T (T) reported Q4 adjusted earnings Monday of $0.54 per share, the same as the year-ago period and above the estimate of analysts surveyed by FactSet calling for $0.50. Total operating revenue in Q4 was $32.30 billion, up from $32.02 billion a year earlier and above the FactSet consensus estimate of $32.02 billion. The company said it expects full-year 2025 adjusted EPS in a range of $1.97 to $2.07, below the FactSet consensus estimate of $2.16. AT&T shares were up 5.9%.

SoFi Technologies (SOFI) reported Q4 adjusted earnings Monday of $0.05 per diluted share, up from $0.02 a year earlier and above the FactSet consensus estimate of $0.04. Total Q4 net revenue was $734.1 million, up from $615.4 million in the year-ago period and above the FactSet consensus of $674.6 million. The company expects Q1 GAAP EPS of $0.03 on adjusted net revenue of $725 million to $745 million. For the full year 2025, the company expects GAAP EPS of $0.25 to $0.27 on adjusted net revenue of $3.20 billion to $3.28 billion. SoFi shares were down 11.2%.

Walgreens Boots Alliance (WBA) shares fell Monday following a report by CNBC's David Faber stating that the company's talks with Sycamore Partners on a go-private deal are "mostly dead," according to media reports. Walgreens shares were down 5.9%.

QXO (QXO) said Monday it has launched an all-cash tender offer to acquire Beacon Roofing Supply's (BECN) outstanding shares for $124.25 each for an enterprise value of roughly $11 billion. QXO shares were down 4.8%, while those of Beacon were up 1.3%.

Emerson Electric (EMR) on Monday agreed to acquire the remaining minority stake in Aspen Technology (AZPN) that it doesn't currently own and take the industrial software company private in an all-cash deal worth $7.2 billion. Emerson shares were down 2%, while those of Aspen were up 3.3%.

Spotify Technology (SPOT) and Universal Music Group said Sunday they have signed multi-year agreements to collaborate on recorded music and music publishing. Spotify shares were up 0.5%.

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