The deal will allow Canary Wharf Contractors to make a start on building 25 Churchill Place, which is expected to create around 1,000 construction jobs.
A consortium of Barclays, Deutsche Pfandbriefbank, Lloyds TSB and The Royal Bank of Scotland will provide the £190m development and investment loan.
Canary Wharf managing director of finance Peter Anderson said: “We are delighted to have concluded this facility in the current difficult financial market.
“It shows that with a good consortium of lenders and the right project it is still possible to raise significant construction funding.
“We can now start construction in early 2012 knowing we have secured all necessary finance.”
Songbird Estates, the owner of Canary Wharf, said it had cleared the way for construction after also previously signing a pre-let for half the building to the European Medicines Agency.
The agreed rent on the 25-year lease is £46.50sq ft, starting from January 2015. EMA will receive a three-year rent holiday in exchange for fitting out the building.
Churchill Place will be one of the most energy efficient office buildings on the Canary Wharf Estate to date.
Environmental features will include elevators that store and reuse energy elsewhere in the building, the latest air-conditioning equipment that recycles the energy from exhaust air and photo voltaic cells to generate energy from the sun’s rays.
The building will also have a ‘green’ roof and is designed to achieve an ‘excellent’ BREEAM rating and an Energy Performance Certificate rating of 40 or better.