Image courtesy of Handel Architects

As Vertex Pharmaceuticals weighs whether to relocate its headquarters, Boston-based Beacon Capital Partners is aggressively pursuing a new lab project that could lure the life science firm from its Fan Pier perch.

Despite the downturn in lab demand and glut of life science space in Greater Boston, Beacon Capital is seeking to add a second building next to its 500,000-square-foot 2 Harbor St. building, now nearing completion without an announced tenant.

Known as the South Boston Innovation Campus, the 4.4-acre site is located near Vertex’ Jeffrey Leiden Center for Cell and Genetic Therapies which occupies 269,000 square feet at 6 Tide St.

Vertex also has leased 344,000 square feet at 22 Drydock Ave., where a development team recently announced plans to break ground this spring.

Vertex has been focusing on sites in the eastern side of the Seaport, the Boston Globe recently reported. Industrial parcels within the Raymond L. Flynn Marine Park have attracted a surge of demand for lab projects in recent years, but many developers have pulled back from pursuing new projects amid a steep dropoff in tenant demand since 2022. Only 28 percent of the 7.4 million square feet of lab space under development in Greater Boston is preleased, according to a recent JLL report.

But the prospect of luring Vertex to establish a new megacampus in a neighborhood where it’s already expanding represents a rare opportunity for developers to land a major tenant in an otherwise quiet leasing environment.

Beacon Capital is seeking approval to add a second building on the Harbor Street site, located at the corner of Northern Avenue across from the Harpoon Brewery.

A single 500,000 square foot life science building was approved in December 2020 and is nearing completion without an announced tenant commitment.

But in February, Beacon Capital submitted plans to redesign the project site, adding a second building totaling 350,000 square feet by eliminating a surface parking lot. The surface parking would be replaced by an underground garage beneath the new building, known as 4 Harbor.

Beacon Capital declined to comment on a potential tenant. At a public meeting in March, Beacon Capital Managing Director Eric Ewer said the firm has its eye on a specific target.

“The whole industry has had a pretty dry year but things have picked up this year, and we have our fingers crossed with a very big tenant in our neighborhood that may be interested,” Ewer told a Boston Planning & Development Agency impact advisory group. “But it’s too early to say anything.”

Handel Architects, which designed MP Boston’s Winthrop Center skyscraper, already is promoting 4 Harbor as a significant new addition to the marine park landscape that blends the neighborhood’s maritime industrial history with its modern innovation cluster.

Another option for Vertex is Boston-based Marcus Partners’ 742,000-square-foot lab project at 310 Northern Ave., which was approved in 2022 but has yet to break ground. Marcus Partners declined to comment.

Vertex’ Fan Pier headquarters was developed by The Fallon Co. of Boston, which sold it shortly after its 2014 completion for $1.1 billion, to Newton-based Senior Housing Properties Trust, an affiliate of RMR Group that is now known as Diversified Healthcare Trust.

Vertex did not return messages seeking comment.