The developer of the $1.5 billion Assembly Row project is buying the former Ikea property on the Somerville site, where it may build a supermarket, homes, and offices, executives said Monday.

Federal Realty Investment Trust of Maryland has signed a purchase and sale agreement to acquire the 12-acre site from the Swedish retailing giant, which canceled plans in July for a 350,000-square-foot emporium on the property. The sale price was not disclosed.