JDS Development Group took out $660 million in interest-only, three-year loans for the almost-completed American Copper Buildings at 626 First Avenue in Manhattan.

That includes a $500 million senior loan from AIG, and a $160 million mezzanine loan from Apollo Global Management and SL Green, announced December 27 by JLL Capital Markets.

“Due to the building’s 421-a tax abatement designation, the towers were able to be constructed in what would otherwise have been a prohibitive funding environment,” said Aaron Appel, managing director for JLL, who with executive vice president Michael Diaz and senior vice president Mark Fisher led the JLL team that structured the transaction. “There is really no comparable product in the city, which made this a highly sought-after lending opportunity.”

Designed by ShoP Architects, the copper-clad towers include 601 market-rate and 160 affordable apartments.