SAN FRANCISCO-Apartment REIT BRE Properties Inc. has paid $41.4 million for two development sites that have the potential for up to 360 apartment units and 17,000 square feet of retail in the Mission Bay district. The company says that the sites, adjacent to the San Francisco Giants ballpark, are among the last remaining market-rate apartment parcels in the Mission Bay master plan, which will include 6,000 residential units; 280,000 square feet of neighborhood-serving retail; 4.4 million square feet of commercial, medical and biotech lab space; and more than 41 acres of parks and open space.

The parcels can be developed in phases. Phase one is planned for 170 market-rate apartment units and 17,000 square feet of retail; the second phase can be developed with an additional 190 market-rate units.

BRE says it found the project sites attractive because of their Mission Bay location, which is close to a substantial employment base, including the new UCSF Medical Center and research campus, Bayer Healthcare Pharmaceuticals, FibroGen, Nektar Therapeutics, and Old Navy headquarters. Mission Bay also is home to the future two-million-square-foot corporate campus of Salesforce.com.

Stephen C. Dominiak, BRE EVP and chief investment officer, commented in a prepared statement: “The lack of available land, strong anticipated revenue growth, limited supply, and proximity to local employers and mass transit will create an ideal environment” for the projects. The company expects pre-development work to take place over the next 12 to 15 months, with construction commencing in mid-2012. The seller of the parcels was not disclosed.