Larry Gagosian responded yesterday to a lawsuit by client Ronald O Perelman over money lost in the exchange of 11 works valued at over $45 million, including an unfinished Jeff Koons sculpture, a Cy Twombly painting, and a sculpture by Richard Serra. In a series of papers filed this week in New York State Supreme Court, Gagosian claims that he had lost money in the transactions, and that Perelman’s claims were “frivolous.”