Check out the companies making headlines after the bell:

Sonos stock plunged more than 13 percent in after-hours trading after reporting third-quarter earnings, the company's first quarterly earnings report since its initial public offering in August. The smart speaker company reported $208 million in revenue, meeting analysts' expectations. Sonos also reported a loss of 45 cents per share.

Nutanix shares rose more than 3 percent in the extended session following the announcement of a $20 million deal with the U.S. Department of Defense. An agency within the DoD will use the cloud computing company's software to operate 15 remote sites. The deal is the largest in Nutanix's history, the company said.

Casey's General Stores stock rose over 3 percent in after-hours trading after the company reported first-quarter earnings that beat analysts' expectations. The convenience store chain reported $2.59 billion in revenue, higher than the $2.58 billion analysts expected. The company also reported earnings of $1.90 per share, 23 cents higher than the $1.67 per share estimated by analysts.

Endocyte shares fell over 4 percent in the extended session after the biopharmaceutical company announced a $175 million proposed public offering of common stock. The underwriters would also be granted a 30-day option to purchase up to an additional $26.25 million in stock on the same terms. "There can be no assurance as to whether or when the offering may be completed, or as to the actual size or terms of the offering," the company said in a statement.