Curis Inc. (Nasdaq: CRIS) shares climbed 14% to $3.34, on three million shares, or five times its daily average, after the drug developer and its partner Roche Group announced positive results from a midstage study of their skin-cancer treatment.

Citigroup Inc. (NYSE: C) traded in 263 million shares Monday, closing in on a daily average of 482 million. C announced Monday it will slash the number of common shares outstanding through a 1-for-10 reverse stock split, and reintroduce a dividend

Sprint Nextel Corp. (NYSE: S) shares declined 13.4% to $4.38, on volume of 134 million shares, better than double its daily average of 55 million, a trading day after rival AT&T Inc. (NYSE: T) said it would acquire T-Mobile USA from Deutsche Telekom AG in a $39-billion deal that would make AT&T the largest U.S. wireless carrier.