The office building at 520 Fifth Ave, a 1,002-foot tall luxury condo tower at East 43rd Street, is now more than 40% leased after nine months of marketing. The new leases were for four companies including Headlands Technology, Abrams Capital, MFA Financial Inc. and 1832 Partners. The building also offers 210,000 square feet of office space with 12-foot-high ceilings. The asking price for the building is between $100 and $200 per square foot.