NEW YORK—AppNexus has signed a long-term, 220,000-sq.-ft. lease expansion and extension at 28 & 40 West 23rd Street.

Colliers International’s Andrew Roos, vice chairman, leads the leasing efforts at the property on behalf of its owners, which include the Cohen, Roos and Carmel families. Michael Cohen, president of Colliers International Tri-State, also represented the leasing efforts on behalf of the owners, while Mark Weiss and Rob Eisenberg of Newmark Grubb Knight Frank represented the tenant.

AppNexus, a real-time advertising technology firm, began its operations at the building with 24,500 sq. ft. less then three years ago. As the firm grew, the property ownership was able to update the property to accommodate the company, which is now the anchor tenant.

“We have gone to great lengths to create a campus-style complex that is appealing to digital, media and fashion companies,” said Roos. “There has been a synergistic relationship with AppNexus since they first moved into the complex, and we are thrilled to extend our partnership with them for at least the next 10 years.”

AppNexus’ new lease includes the entire second floor, 43,000 sq. ft. on the fifth floor and 19,600 sq. ft. on the sixth floor, including the penthouse. The company plans to move to its expanded space in the third quarter of this year.

Additional tenants at the property include Home Depot, Nike and the InterPublic Group, among others.