200 Clarendon, Boston Properties’ most iconic trophy office holding in its namesake city. iStock photo

Private equity giant Bain Capital renewed its high-profile headquarters lease at 200 Clarendon in Back Bay while expanding to 378,000 square feet at the BXP-owned tower.

The $185 billion money manager originally relocated to the Back Bay landmark previously known as the Hancock Tower in 2011, when it leased 208,000 square feet on seven floors for 15 years. It currently occupies 315,000 square feet, spokesman Ernesto Anguilla said.

BXP is updating the 1.7 million-square-foot skyscraper with a new tenant-only “200 Club” including fitness, conference and lounge areas. The project will result in higher tenant retention and rents, Chief Financial Officer Michael LaBelle said during a conference call last week.

It’s part of a larger trend among Boston’s trophy office building owners to stack their properties full of amenities to “earn the commute” from tenants’ workers.

BXP completed 195,000 square feet of leasing during the second quarter in Boston’s Back Bay and Financial District.

“The Back Bay continues to outperform the financial district, which continues to have to digest the new construction pipeline,” President Douglas Linde told analysts.