Vertex's two-building headquarters opened earlier this month.

BOSTON- Senior Housing Properties Trust said late Monday afternoon it had agreed to acquire Vertex Phamaceuticals’ newly opened headquarters here for $1.125 billion, or about $682 per square foot. The Vertex headquarters, consisting of two 15-story office buildings, is part of the Fallon Co.‘s Fan Pier mixed-use development.

The Boston Business Journal reported this past October that developer Joseph Fallon would consider selling the Vertex towers for $1 billion or more, but that such an offer wasn’t forthcoming as yet. The buildings, which total 1.65 million square feet, are 96% occupied by Vertex, which has a remaining lease term of 15 years there as it relocates from Cambridge, MA.  

David Hegarty, SNH’s president and COO, says the acquisition represents “a unique opportunity to further diversify SNH’s portfolio and increase our exposure to the medical office building segment.” He adds that it’s “consistent with our stated strategy to focus on medical office buildings and private-pay properties, and we expect the transaction to be immediately accretive to normalized funds from operations per share.”

The deal establishes a new price-per-square-foot watermark for office properties in the Seaport District. This past December, TIAA-CREF acquired 51 Sleeper St. for $60.2 million; at the time, the deal set a new record for the neighborhood at $400 per square foot.

Simultaneous with entering the agreement to acquire these buildings, the Newton, MA-based seniors housing REIT received a term loan commitment for $800 million from Jefferies Finance LLC and Wells Fargo Bank. The term loan will have an interest rate of Libor plus 140 basis points, can be repaid in part or whole at any time without penalty and will mature five years from closing. Prior to closing on the Vertex headquarters acquisition, the term loan is expected to be syndicated to a group of banks, and the term loan is expected to close simultaneous with the closing of this acquisition.