Housing developer Toll Brothers has paid $44.1 million to acquire a site approved for a 525-unit apartment complex in the Quadrangle section of Cambridge’s Alewife neighborhood.

Developer Westbrook Partners received planning board approval in December 2017 to demolish an office building at 55 Wheeler St. to make way for the three-building complex, including 90 affordable units, on the 6-acre parcel.

Two groups of neighborhood residents filed appeals with the state Department of Environmental Protection challenging the Cambridge conservation commission’s approval of the project, citing potential harm to water quality at Fresh Pond and alleged faulty stormwater calculations by the developers.

The appeal was dismissed in September at the petitioners’ request, according to a DEP filing.

The complex will be served by 448 parking basement and ground-level parking spaces, along with 555 long-term and 53 short-term bicycle spaces.

Alewife’s Quadrangle section just south of the MBTA commuter rail tracks is attracting intensified interest from developers because of its availability of older commercial properties suitable for lab and multifamily conversions.

The city of Cambridge’s Alewife District Plan released this month identifies the Quadrangle and the nearby shopping center district on Alewife Brook Parkway as significant growth areas for additional housing. Between 2013 and 2016, nearly 1,400 multifamily units were completed in the Alewife neighborhood, primarily on Cambridgepark Drive. Developer Cabot, Cabot & Forbes last week proposed a 1 million-square-foot residential and commercial project near the 55 Wheeler site.