MGM, maintaining a business-as-usual stance, has acquired its first new property since Sony Corp. signed a definitive takeover agreement to buy the studio. Mischa Barton, star of Fox's "The O.C.," has signed on to topline "Hexxx." MGM-based Jennifer Klein is producing through her Apartment 3B Prods. Mark Gibson and John Raffo penned the horror thriller, which revolves around the world of voodoo and is set against the backdrop of New Orleans. Toby Jaffe and Pete Chiarelli are the executives on the project. Other projects in the works at Apartment 3B include the Kate Kondell-penned "Don't Tell My Mother," the urban classroom comedy "F+" and "Truce," a World War I drama that Klein will produce for Warner Independent Pictures. Barton and Gibson, whose credits include "Snow Dogs" and "The In Crowd," are repped by WMA. Raffo is repped by Evolution Entertainment.