Federal prosecutors on Friday unsealed a new conspiracy charge against former pharmaceutical executive Martin Shkreli and his former lawyer, Evan Greebel.

Both men were arrested last December and accused of scheming to steal money from pharmaceutical company Retrophin Inc., where Mr. Shkreli had been the chief executive, to cover up losses suffered by investors in Mr. Shkreli’s hedge funds. Retrophin’s board ousted Mr. Shkreli as CEO in 2014.

Mr. Shkreli had pleaded not guilty to seven counts of securities fraud and conspiracy. Mr. Greebel had pleaded not guilty to one count of wire-fraud conspiracy.

On Friday, Brooklyn federal prosecutors added a new securities fraud conspiracy charge against both men related to Mr. Shkreli’s alleged failure to disclose to the Securities and Exchange Commission his control over certain shares of Retrophin. Mr. Greebel had served as outside counsel to Retrophin.

Benjamin Brafman, a lawyer for Mr. Shkreli, said in a statement: “There is nothing in the new indictment that impacts in any way on the flawed theory of the case as applied to Mr. Shkreli.”