Check out the companies making headlines after hours on Thursday:

Ross Stores — Shares of the discount retailer rose about 0.5% in after-hours trading on the back of a surprise profit and better-than-expected revenues. Ross posted a profit of 6 cents per share, which includes a benefit of 19 cents per share, and revenue of $2.68 billion for the first quarter. Analysts polled by FactSet expected a loss of 28 cents per share n revenue of $2.51 billion. However, CEO Barbara Rentler said: “There remains significant uncertainty on how the pandemic will continue to evolve and affect consumer demand and the economy, and the potential exists for additional government mandated shutdowns.”

OSI Systems — The X-Ray machine developer’s stock slid more than 3% after the company issued disappointing revenue guidance for fiscal 2021. OSI Systems expects revenue to range between $1.09 billion and $1.14 billion. That’s below a FactSet median estimate of $1.19 billion.

Sorrento Therapeutics — Sorrento shares climbed 2.6% after the biopharmaceutical company agreed to buy SmartPharm Therapeutics for up to $19.4 million in common stock. The deal is expected to close next month. “The merger with Sorrento presents a tremendous opportunity to advance our next-generation, non-viral gene therapy technology,” said SmartPharm CEO Jose Trevejo in a statement.

Keysight Technologies — Keysight Technologies shares popped more than 6% in after-hours trading after the company posted better-than-expected results for its fiscal third quarter. Keysight reported a profit of $1.19 per share on revenue of $1.01 billion. Analysts expected earnings of 83 cents per share on revenue of $915.4 million, according to FactSet.