Cambridge-based Foundation Medicine has signed the biggest commercial lease in Boston’s Seaport District in eight years, consolidating 1,100 employees at 400 Summer St. and giving new momentum to the neighborhood’s growing life science cluster.

WS Development will develop the 16-story, 646,000-square-foot office and lab building scheduled to begin construction later this year for completion in 2022.

“The relocation ensures Foundation Medicine is well-positioned to support the company’s strategic growth trajectory as it continues its patient-centric mission to transform cancer care by advancing the science and application of molecular medicine in clinical care,” Foundation Medicine said in a statement.

Foundation Medicine’s 580,000-square-foot lease is the biggest in the Seaport District since Vertex Pharmaceuticals agreed to occupy a 1.1-million-square-foot headquarters on the Fan Pier in 2011. Alexion Pharmaceuticals leased 150,000 square feet at 121 Seaport and relocated its headquarters from New Haven, Connecticut last year, while the former Mass Innovation Labs, now known as SmartLabs, leased 54,000 square feet at the Innovation Square (isQ) Seaport development in 2017.

Foundation Medicine began scouting expansion locations around Greater Boston and zeroed in on the Seaport location in late winter.

WS Development submitted plans to the Boston Civic Design Commission this spring for the building, designed by New York-based architects Morris Adjmi with architects of record Stantec. Set on parcel P, the site borders the elevated section of Summer Street, and will include a new public staircase connecting to the Congress Street level.

Foundation Medicine, which develops individually customized cancer treatments, currently occupies 123,200 square feet at 150 Second St. in Cambridge, where its lease expires in 2024, along with 38,000 square feet at 10 Canal Park. Roche Pharmaceuticals paid a combined $3.4 billion for the company in a pair of transactions in 2015 and 2018.