In its largest local expansion to date, Facebook will occupy 263,500 additional square feet in a new Kendall Square development that gained two new investors this week in a $1.2 billion deal.

The social media giant subleased the entire 50 Binney St. office building, which was developed by Alexandria Real Estate Equities, and recapitalized with Norges Bank and Metlife joining Alexandria in the ownership structure.

In an email, Facebook spokeswoman Jamila Reeves said only that the building will be used for an expansion of its “tech and engineering teams”.

Facebook emerged as the potential new tenant for the building after Cambridge-based Bluebird Bio offered the space for sublease this summer. Bluebird Bio, in turn, had subleased the space from Sanofi Genzyme at a rent of nearly $100 per square foot from 2021 to 2030, but never occupied the building.

The Facebook sublease calls for annual rent of $28 million, according to an SEC filing, which equates to over $106 per square foot. Facebook is scheduled to take over the space by Dec. 31, 2022.

Facebook has been scouting potential expansion sites in Greater Boston since 2020, and the 50 Binney St. property is located next to its 130,000-square-foot offices at 100 Binney St.

Bluebird Bio reduced its real estate footprint after spinning off a portion of its business into a new entity, and leased 61,000 square feet at Assembly Row in Somerville for its new headquarters in 2023.

Editor’s note: This report has been updated with a statement from Facebook.