Blackstone Group has reached an agreement to restructure about $7bn of the remaining debt tied to its epic 2007 purchase of Sam Zell's Equity Office Properties Trust, the largest leveraged buyout ever, according to people familiar with the matter.

The deal marks the second major restructuring Blackstone has pulled off this year as the credit markets have thawed, enabling well-capitalised owners to restructure properties that were purchased near the top of the market.