Ventas Inc. (VTR) agreed to acquire Cogdell Spencer Inc. (CSA) in a deal that values the company at about $217 million and will expand the health-care real estate investment trust's presence in the medical office building sector.

Cogdell holders will receive $4.25 a share, an approximately 8% premium to Friday's close. The stock last closed above the offer price in September. Meanwhile, preferred stock holders will receive $25 a share. Ventas valued its investment, including debt, at about $760 million to $770 million, before transaction expenses.

The deal, which includes 72 medical office buildings, is expected to immediately add to Ventas's normalized funds from operations and is seen closing in the second quarter. The offer values the properties at just over $200 a square foot.

"Cogdell's high-quality properties enhance our medical office building market presence, especially in the Southeast, and provide an opportunity to scale our Lillibridge Healthcare Services subsidiary platform," Ventas Chairman and Chief Executive Debra A. Cafaro said.

Meanwhile, Cogdell Chief Executive Raymond Braun said the board conducted a thorough review of strategic options and said the sale to Ventas will deliver the most value to shareholders.

Cogdell also has reached an agreement to sell its design-build and development business, Erdman, to an affiliate of private-equity firm Lubar & Co. prior to completion of the Ventas transaction.

Ventas, the largest U.S. owner of senior housing and assisted-living facilities, earlier this year acquired rival Nationwide Health Properties in a move aimed at better capitalizing on growing demand for senior housing.

Last month, the company reported its third-quarter earnings surged 78% as recent acquisitions helped it more than double its revenue from a year earlier.

Shares of both companies were inactive premarket. Ventas closed Friday at $54.94, while Cogdell closed at $3.92.

-By Lauren Pollock, Dow Jones Newswires; 212-416-2356; lauren.pollock@dowjones.com