Biosciences firm CSL Behring LLC is to become the sole occupant of 500 N. Gulph Rd., a 100,000-square-foot office property being redeveloped in King of Prussia by Brandywine Realty Trust.

CSL will lease the North Gulph Road building, in addition to the roughly 240,000 square feet it already rents at its nearby headquarters campus at 1020 First Ave., which is also owned by Brandywine, CSL spokeswoman Natalie de Vane said in an interview Tuesday.

Brandywine, based in Philadelphia, is revamping the facade of the aged five-story North Gulph Road building, overhauling and expanding its interior, and building a new parking garage.

CSL plans to move into the building in early 2019, de Vane said. The additional space will allow the company to boost its existing headcount of 1,100 employees and contractors by more than 400, she said.