Stock futures were dropping on Tuesday a run-up in bond yields set the market on edge at the start of what is historically the worst month for the S&P 500.

Artificial-intelligence stocks were struggling as investors ditched risk assets. Shares of memory-card maker Sandisk slid 3.2% ahead of the opening bell. Glassmaker Corning, chip manufacturer Intel, and chips and networking company Marvell were also falling in premarket trading.

Robinhood Markets rose 2.3% to $107.22 after Morgan Stanley upgraded the stock to Overweight and raised its price target to $150 from $124, citing signs that the company's broader product capabilities were improving the economics of its installed customer base.

Novartis jumped 4.5% after the Swiss drugmaker announced positive Phase III trial results for its multiple sclerosis treatment. That came after Novartis paused eight clinical trials of an experimental therapy targeting autoimmune disorders after three patients died.

Cybersecurity company Palo Alto Networks, server maker Dell, data-center connectivity provider Credo, and database system developer MongoDB are set to report earnings after the closing bell.