Leases by a pair of local life science companies have driven the occupancy rate at 65 Hayden Ave. in Lexington up to 70 percent.

Concert Pharmaceuticals and Accent Therapeutics leased 55,522 square feet and 15,200 square feet, respectively, in the 213,004-square-foot office and lab building. 65 Hayden Ave. is part of the 37-acre Hayden Research Campus, which is owned by a joint venture of Cambridge-based King Street Properties and HCP Inc.

Concert Pharmaceuticals will relocate and expand its headquarters from 99 Hayden Ave., where its 50,000-square-foot lease expires Sept. 30. The 10-year lease at 65 Hayden Ave. calls for base rent of $2.8 million in the first year, and a tenant improvement allowance of $5 million, according to an SEC filing.

Cancer researchers Accent Therapeutics will occupy a portion of the third floor in the 65 South building this month for a new headquarters.

JLL’s Joe Flaherty, Don Domoretsky and Ben Coffin represented ownership in both transactions. Newmark Knight Frank’s Mark Winters and Matt Malatesta represented Concert Pharmaceuticals, while NGK’s Juliette Reiter represented Accent Therapeutics.