The CB3 building is currently undergoing restructuring, led by WO2 and designed by the firm Ateliers 2/3/4/. Unoccupied since 2016, this office building is being transformed into a low-carbon model. In future, it will offer 34,400 m² of office space and 2,800 m² of outdoor space. By aiming for low-carbon construction, for example by using bio-based materials, it is becoming the first building in La Défense to target the Excellent level of the Low Carbon Building (BBCA) Renovation label.

Designed by the architectural firm Ateliers 2/3/4 and developed by WO2, CB3 aims to stand out from the traditional real estate offerings in La Défense. The building will offer open, collaborative workspaces, with five office floors covering 3,800 m² and offering a ceiling height of 3.2 metres on the first floor. It will also feature a large central patio, dining areas, an auditorium, integrated services, as well as ground-level terraces and loggias.

The CB3 project is part of an ambitious low-carbon restructuring initiative based on the reuse of materials and the use of solid wood. This approach will reduce carbon emissions by 48% compared to a new building. This will enable the building to become the first to aim for the Low Carbon Building (BBCA) Renovation label at the Excellent level.

Sanofi has chosen the CB3 project, located in the heart of La Défense, to house the future headquarters of its French operations in a low-carbon environment. The group has announced that, starting in the second half of 2027, nearly 3,000 employees — mainly from the sales, manufacturing & supply and corporate departments — will move into this iconic building.

The CB3 building, formerly known as SGAM, was built in 1978 and renovated in 2006. In the 1980s, the architects who designed the project, Roger Saubot, François Jullien, Skidmore and Associates, took the opposite approach to the vertical logic of the business district and built a 30,000 m² complex (equivalent to a first-generation tower, no more than 37 m high).

Despite its horizontality, the building is in keeping with the agency's other projects, with its glass façades, silver aluminium profiles and dark blue spandrels.