Shifting fraud theories helped sink an attempted securities class action appeal by former employees of the pharmaceutical company Covis.

The U.S. Court of Appeals for the Second Circuit ruled in Brown v. Cerberus Capital Management, 17-63, that the defendants had “abandoned the theory of securities fraud that they pressed before the district court,” in favor of an insider trading charge “for the first time.”

The employees had sued over the restructuring of a major investor, private equity firm Cerberus Capital Management.