The trophy office building Rockrose Development is redeveloping with former New York Gov. Elliot Spitzer's family firm, Spitzer Enterprises, just landed its first new office tenant.

Financial consulting firm Cornerstone Research is leasing 43k SF in the north building of the project at 2000 L St NW, the Washington Business Journal reports.

The L Street building is being redeveloped in combination with the adjacent 2001 K St NW to create the 800k SF Alexander Court. This is the second-largest privately developed office building in years, behind Carr Properties 875k SF Fannie Mae HQ.

Rockrose bought the L Street building in 2013 for $192M and Spitzer's father bought the K Street building in 2001. Pelli Clark Pelli Architects is designing a 12-story atrium, rendered above, connecting the buildings where an alley now sits.

The redevelopment is slated for completion in late 2017 and Cornerstone Research will begin occupying the space in March 2018. Before the deal to combine the buildings was struck, Spitzer’s building was 95% occupied, and Rockrose’s was 75% occupied. Some of those leases will expire to coincide with the finished construction, meaning broker Avison Young can sign more leases like Cornerstone's at trophy prices. [WBJ]