Investment Technology Group, an agency brokerage and financial technology firm, has leased 73,076 square feet at 100 High St. in Boston.

John Hennessey and Jim Griffin of GVA Thompson Hennessey & Partners represented ITG, according to a statement.

The landlord, Equity Office Properties, was represented by Ronald Perry and Roger Breslin of Colliers Meredith & Grew.

ITG is the first major tenant to commit to 100 High St. after Bingham McCutchen outgrew its space and relocated last year. Since then, Equity Office Properties has rebuilt the building’s infrastructure, renovated the building’s lobbies and reoriented the building’s main address to High Street.

ITG’s anticipated move date is May 2010.