A Cambridge tech company’s steady expansion could anchor the office portion of a high-visibility air rights development in Back Bay.

Online vehicle marketplace CarGurus is in negotiations with Boston-based Samuels & Assoc. to occupy the bulk of the 1001 Boylston St. office tower, according to multiple real estate sources. The 20-story, 450,000-square-foot building is planned for the Massachusetts Department of Transportation’s Parcel 12, located above the Massachusetts Turnpike at the end of Newbury and Boylston streets.

The project joins a recent flurry of potential development activity at the western edge of Back Bay. The Massachusetts Convention Center Authority last month authorized the sale of the nearby Hynes Convention Center. And Boston-based Trinity Financial has been in talks with the Harvard Club of Boston on a potential 200-room hotel built on the club’s rear parking lot at 415 Newbury St.

CarGurus occupies three buildings in East Cambridge, including all 53,000 square feet of office space at developer Urban Spaces’ 121 First St. which opened last winter. The company also has offices at 55 Cambridge Parkway and maintains its headquarters at 2 Canal Park.

In August, the Boston Planning and Development Agency approved Samuels & Assoc.’ plans for the 657,000-square-foot Back Bay development consisting of a pair of office and hotel-condo towers which will flank a new pedestrian plaza and elevated terrace overlooking the Turnpike.

Designs by Elkus Manfredi Architects call for the buildings to be located next to, rather than directly above, the highway’s travel lanes. Marketing materials from CBRE New England, which represents ownership in leasing, tout the office building’s multiple outdoor terraces and “iconic” branding opportunities including a rooftop logo visible to the 140,000 vehicles traveling daily on the Turnpike.

Samuels & Assoc. declined comment beyond a statement that no leases have yet been executed for the office building. The developer previously said that final designs are nearing completion and that groundbreaking could take place in the first quarter of 2020.

CarGurus declined to comment. In August, the company reported second quarter revenues of $145 million, up 31 percent from the same period in 2018, and net income of $6 million.

The Parcel 12 project is the latest in decades of attempts by developers to build office towers and housing above the Turnpike in the South End, Back Bay and Fenway, despite the complications and costs associated with construction above an active highway.

Another developer, Boston-based Weiner Ventures, recently abandoned plans for a 108-unit luxury condo tower named 1000 Boylston St. on another nearby Turnpike air rights parcel.

Developers Gerding Edlen and Meredith Management Co. broke ground in January 2018 on a 315-unit apartment tower which includes a 12,500-square-foot air rights segment above the MBTA’s Lansdowne station. A future phase could add 430,000 square feet of office and residential space above the Turnpike.