Generac signed a $2.4 billion deal to sell data-center generators to Amazon.com. Shares jumped 35%, to $237, in after-hours trading Wednesday.

Vicor granted a license to a new original equipment manufacturer. The stock gained 11%, to $204, after the bell.

Longeveron said a recent trial to treat a heart condition in children failed to meet its primary endpoint. Shares sank 60%, to $2.69.

Viant Technology said one of its stockholders would offer 8.5 million shares in an underwritten public offering. The stock shed 10%, to $11.10.