Alexander, who has dressed starlets such as Paris Hilton, is accused of meeting women on the Internet and assaulting them when they visited about modeling opportunities between 2002 and 2007. His defense has claimed some of the women made the allegations to seek fame.
At least 18 women and girls, ranging in age from 14 to 27, have accused him of abuse.
He now faces more than 40 felony and misdemeanor counts of sexual assault that include rape, sexual battery and committing a lewd act on a child, said Jane Robison, a spokeswoman for the Los Angeles County district attorney's office.
He has pleaded not guilty to all previous charges and could face life in prison if convicted on all counts.
He is free on bail after being arrested in March. Superior Court Judge Elden Fox denied a prosecution request Tuesday to increase Alexander's bail to $2.3 million (EUR1.72 million).
Alexander's new attorney, Danny Davis, said outside court that there is a "common, unifying source" among the victims but declined to elaborate, and he said the evidence would likely be revealed at a preliminary hearing.
"It appears to me this case, fairly, is gossip among young models that has gone a little wild," Davis said. "There's been a great deal of contamination and sharing of stories."
Alexander was arrested in March at his Beverly Hills apartment. There also are criminal investigations in New York and Massachusetts, Robison said.
Before the court hearing, Alexander also was arrested on three warrants from Dallas, where prosecutors plan to seek indictments on suspicion of sexual assault, said Jamille Bradford, a spokeswoman for the Dallas County district attorney.
Two warrants are include allegations of sexual assault, and a third accuses him of sexual assault of a child younger than 17, all second-degree felonies, Bradford said. Alexander is accused of assaulting two of the victims in both California and Texas.
Bail on the warrants was set at $500,000 (EUR374,672), and an extradition hearing was waived. It was not clear when Alexander would travel to Texas.