The Kushner Companies’ purchase in 2007 of 666 Fifth Avenue, an aluminum-clad office tower in Midtown Manhattan, for a record price of $1.8 billion is considered a classic example of reckless underwriting. The transaction was so highly leveraged that the cash flow from rents amounted to only 65 percent of the debt service.

As many real estate specialists predicted, the deal ran into trouble. Instead of rising, rents declined as the recession took hold, and new leases were scarce. In 2010, the loan was transferred to a special servicer on the assumption that a default would occur once reserve funds being used to subsidize the shortfall were bled dry.

But the story may yet have a happy ending for Kushner, a family-owned business that moved its headquarters from Florham Park, N.J., to 666 Fifth, its first major acquisition in Manhattan.

Instead of foreclosing on the 39-story building, which stretches from 52nd Street to 53rd Street, the lenders agreed last month to reduce the principal and defer some of the interest payments on the interest-only loan and extend its maturity for two years, until February 2019. In exchange, Kushner and its powerful new partner in the deal, Vornado Realty Trust, agreed to pour tens of millions of dollars into the building to improve its leasing prospects. The 1.5-million-square feet office building is currently 30 percent vacant.