Image courtesy of Elkus Manfredi Architects.

A 500,000-square-foot office-lab tower will begin to rise in the Fenway this year following leases by a life science-focused venture capital firm and Cambridge biotech company.

Third Rock Ventures will move its East Coast headquarters from Newbury Street into 24,000 square feet at Samuels & Assoc.’s planned 14-story tower at 201 Brookline Ave. And one of its portfolio companies, Tango Therapeutics, will relocate from Kendall Square into 65,000 square feet on two floors.

“It’s an important milestone for us in that [Third Rock Ventures] have selected the Fenway,” said Peter Sougarides, a principal at Samuels & Associates. “It starts to send the message that the Fenway is an important market for life science and biotech companies to look at.”

Demolition of a 2-story section of the former Landmark Center began this month to make way for the new tower, which is scheduled for completion in spring 2022. Boston-based Samuels & Assoc. is partnering with J.P. Morgan Asset Management on the project.

With offices in Back Bay and San Francisco, Third Rock Ventures has raised $2.7 billion since 2007 for its investments in more than 50 life science companies. In June 2017, it announced the closing of its fifth fund after raising $770 million.

Third Rock Ventures’ move places it closer to the Longwood Medical Area health care cluster, a “budding innovation scene” in the Fenway and nearby amenities, COO Kevin Gillis said in a statement. Last June, Time Out Market opened a 25,000-square-foot food hall at 401 Park, which is also owned by Samuels & Assoc.

Tango Therapeutics specializes in targeted cancer therapies. Currently headquartered at 100 Binney St. in Cambridge, it will more than double its footprint with the move to 201 Brookline Ave. 

In 2017, Samuels received Boston Planning & Development Agency approval for 201 Brookline Ave., its first life science building in the Fenway, but held off on groundbreaking pending significant leasing activity.

A building permit was issued on Feb. 14 for the $160 million tower, which will include a roof deck, fourth-floor garden terrace and private balconies on seven floors. The Elkus Manfredi Architects-designed building features 40,000 square plates, lab infrastructure and over 14-foot floor-to-floor heights.

The launch of the life science tower represents the latest stage in Samuels’ transformation of the Fenway, which began with a series of luxury residential towers. Samuels repositioned the former Landmark Center as a startup destination with its Hatch Fenway incubator in 2014, and confirmed the neighborhood’s potential to attract class A office tenants at the Van Ness, a 238,000-square-foot office tower anchored by digital health records specialist Optum. That building also attracted corporate migration from Cambridge with leases by Decibel Therapeutics and health insurer CRICO.

The Van Ness and 401 Park are now 99 percent leased, Sougarides said.

“We’ve been seeing great interest from tenants who are here and want to grow, and tenants coming from outside and want to relocate to the Fenway,” he said.

Third Rock Ventures provided $55 million in series A funding for Tango Therapeutics’ launch in 2017.

The leases leave 400,000 square feet available at 201 Brookline Ave. Newmark Knight Frank represents ownership in leasing.