Forest's shares were up 16 percent in after-hours trading.
Lexapro is a member of the class of antidepressants known as serotonin-selective reuptake inhibitors, which also includes Prozac, Zoloft and Paxil. Lexapro is chemically similar to Celexa, another Forest antidepressant for which generics are already available.
Teva still has the option of launching its generic version of Lexapro, risking possible damages if it loses on appeal. Teva officials could not be immediately reached for comment.