Mike Segar | Reuters
Jack Dorsey, CEO and co-founder of Twitter and founder and CEO of Square, speaks at the Consensus 2018 blockchain technology conference in New York City, New York.
Square stock tumbled 8 percent in after-hours trading following news that CFO Sarah Friar is stepping down. Friar will stay at the company until December before departing to become CEO of Nextdoor, a localized social network for neighborhoods.
"I'm saddened by the news," Square CEO Jack Dorsey, who is also CEO of Twitter, said in a note to employees.
Fluor shares plunged 12 percent in after-hours trading after the construction company reported preliminary third-quarter earnings that missed analysts' expectations. The company expects $4.6 billion in revenue, while analysts had estimated $4.95 billion. Fluor will release final third-quarter earnings numbers on Nov. 1.
Crispr Therapeutics shares jumped 13 percent in the extended session after the Food and Drug Administration lifted a hold on clinical trials for the company's CTX001 sickle cell gene therapy. The companies said that they are on track to initiate clinical studies by the end of the year.
Shares of Vertex Pharmaceuticals, which is partnering with Crispr to develop the therapy, initially rose about 2 percent in after-hours trading before reversing to trade 1 percent lower.