Alexandria Real Estate Equities has agreed to acquire the 644,000-square-foot One Kendall Square tech campus in Cambridge for $725 million.

The seller, DivcoWest, paid just $394 million for the seven-building complex just two years ago. The 8-acre complex is currently 98 percent leased to approximately 50 office, lab and retail tenants, but Alexandria sees significant opportunities for rent upgrades with more than half of the leases expiring through 2019. Current in-place rents average $47 per square foot, according to an SEC filing, well below the market in East Cambridge where some lab space is renting for close to $90 per foot.

Alexandria also sees upside by converting office space into labs, which fetch higher rents. Currently, the complex contains 48 percent office space, 36 percent lab space and 16 percent retail.

With stiff demand for office and lab space in Cambridge, Alexandria also said it plans to move ahead with a 172,500-square-foot office and lab building at 399 Binney St. DivcoWest received approval for that project, which includes a new pedestrian plaza and redesigns to the 1,530-space Kendall Square parking garage entrances, in March.

Alexandria will assume $203 million in existing debt as part of the acquisition, with an interest rate of 4.8 percent and a maturity date of February 2024. It’s also announced an offering of 6.5 million shares of common stock to finance the acquisition.

Newmark Grubb Knight Frank’s Boston office represented DivcoWest in the property transaction, which is expected to close this fall.

Pasadena, California-based Alexandria already owns 5.6 million square feet of commercial real estate in Cambridge. It just completed the 380,000-square-foot 75-125 Binney St. complex which is leased to IBM Watson and Ariad Pharmaceuticals. That helped boost Cambridge lab absorption to an all-time record of 902,000 square feet in the second quarter, according to Boston-based Encompass Real Estate Strategies, making Cambridge the first city in the world with more than 10 million square feet of lab inventory.

Alexandria’s development pipeline also includes the 1 million-square-foot Alexandria Center at Kendall Square at 50-60 and 100 Binney St. Sanofi Genzyme is moving to a new 274,734-square-foot headquarters at 50 Binney St. in 2018, while bluebird bio has leased 255,743 square feet at 60 Binney St.

Bristol-Myers Squibb Co. has leased 400,000 square feet at 100 Binney St. for a new research facility that will open in early 2018, replacing sites in Wallingford, Connecticut and Waltham.

Despite the busy pace of new construction, lab vacancies fell to 1.6 percent in the second quarter, according to an Emcompass report, with the vast majority of new construction pre-leased.