Stocks making the biggest moves premarket: Airbnb, Oracle, American Express and more
Supporters of Airbnb hold a rally on the steps of New York City Hall showing support for the company, Oct. 30, 2015.

Check out the companies making headlines in premarket trading.

Zynex, Coherus BioSciences , Universal Insurance Holdings — Coherus, Zynex and Universal Insurance stock fell on news from S&P 500 Dow Jones indices that the stocks would be moving within small-cap indexes. Coherus is leaving the MidCap 400 for the MidCap 600, while Universal Insurance is leaving the MidCap 600 altogether. Zynex tumbled nearly 6% on news that the firm is leaving the SmallCap 600 index.

American Express — Stock in the credit card giant ticked up 0.5% following an upgrade to outperform from sector perform from RBC earlier Tuesday.

Airbnb — Shares of the vacation rental company rose more than 4% on the heels of the S&P Dow Jones Indices announcement Friday that Airbnb will join the S&P 500 later this month. The S&P 500 is widely tracked by large index funds, which could create buying pressure on Airbnb's stock in the weeks ahead.

NextGen Healthcare — The health-care stock climbed more than 11% following a Bloomberg report Monday that the company was in late-stage talks with potential acquirer Thoma Bravo.

Oracle — The software stock added 1.5% in premarket trading following an upgrade to overweight from equal weight by Barclays. The firm said the company's cloud business should feel tailwinds from artificial intelligence.

Brady Corporation — Shares climbed nearly 11% after the company reported quarterly results. Brady Corporation posted an adjusted $1.04 in profit per share, while analysts polled by FactSet forecast 93 cents.

Warner Bros. Discovery — Shares dipped 1.2% after the company warned that strikes from writers and actors could negatively affect cash flow by a range of $300 million to $500 million.

— CNBC's Alex Harring and Jesse Pound contributed reporting.