Stamford-based genetic-testing firm GeneDx Holdings Corp. said it’s still trying to sublease part of its headquarters building and Connecticut lab spaces, which went dark in 2022 after the company announced plans to exit its reproductive health and somatic oncology businesses.
GeneDx, formerly known as Sema4, disclosed in its 2024 annual report published earlier this year that it’s still trying to find tenants to sublet laboratory space it leased in Stamford (63,000 square feet at 62 Southfield Ave.) and Branford (37,000 square feet at 1 Commercial St.).
The company shuttered those lab operations in 2022, as part of a restructuring that led to hundreds of job cuts. However, the leases for the Stamford and Branford lab spaces remain in place until the end of 2036 and 2030, respectively, according to the company’s annual report.
The company is also still trying to sublet part of its 87,000-square-foot headquarters at 333 Ludlow St. The lease at that location expires in 2034.
GeneDx also has a satellite meeting space in New York City.
A company spokesperson wouldn’t say how much space GeneDx is trying to sublet at its Stamford home base. She did say Stamford remains the company’s corporate headquarters, while its primary operating laboratory is located in Gaithersburg, Maryland.
In May 2022, Sema4 acquired Gaithersburg, Maryland-based genomic testing firm GeneDx for $623 million and renamed itself GeneDx.
Later that year, GeneDx shuttered its Stamford and Branford labs and laid off hundreds of workers.
Notably, in its 2025 first-quarter earnings press release that was published on April 30, GeneDx used a Gaithersburg, Maryland dateline, which typically designates a company’s main base of operations. GeneDx previously used a Stamford dateline in its press releases.
“We chose to update the dateline in our press releases to Gaithersburg to recognize the important work being done at our lab there and to honor that location’s contribution,” the spokesperson said.
The spokesperson also said the company has parties interested in leasing its Connecticut lab spaces, but she didn’t provide further details.
Before becoming GeneDx, Sema4 received $15.5 million in state loans to expand its presence in Connecticut.
