Watertown’s life-science scene is getting a serious shot in the arm. Four biotechs launched by Flagship Pioneering are packing up their labs in Boston and Cambridge and heading to a single suburban address at 99 Coolidge Ave. Local reporting names Repertoire Immune Medicines, Ampersand Biomedicines, Abiologics and ProFound Therapeutics as the companies slated to move in, concentrating a cluster of Flagship-founded research teams under one roof and shifting more day-to-day lab work out of the traditional downtown strongholds, as per the Boston Business Journal.
According to the Boston Business Journal, all four companies have committed to space at 99 Coolidge Ave. The outlet reports that three of the moves are tied to the end of Flagship Pioneering’s Southline Boston lease in 2027, framing this as part of a broader plan to cluster Flagship-backed ventures in Watertown.
About the Building and Developers
The new home base at 99 Coolidge Ave. is a roughly 255,000-square-foot life-science redevelopment on the former Mount Auburn Club site. It is marketed as lab-ready space with large floorplates, on-site amenities and LEED certification. The property listing highlights a cafe, a fitness center and flexible lab floors, while local real estate coverage identifies Alexandria Real Estate Equities and National Development as key players behind the project. LoopNet and other commercial real estate reporting provide the building specifications and ownership details.
Who’s Moving and When
The first clear timing clue comes from Ampersand Biomedicines, which has posted job listings that explicitly say the company "will be moving to Watertown in summer 2026." In those listings, Ampersand's job posting notes that current South Boston roles will shift to the Watertown site. The Boston Business Journal identified the three other Flagship companies that are also heading to 99 Coolidge Ave.
What It Means for Watertown and the Market
The relocations fit into a steady migration of lab tenants into inner-suburban hubs where bigger, newer lab buildings are available and, in some cases, easier to secure than space in Boston and Cambridge. Banker & Tradesman reported earlier large leases at 99 Coolidge Ave. and cited market data showing elevated availability across the inner suburbs, a trend that has nudged some startups to pick Watertown over denser urban blocks.
The consolidation at 99 Coolidge is expected to bring more on-site lab jobs, vendor activity and commuting traffic into Watertown, aligning neatly with the pitch building owners and brokers have been making to tenants that feel priced out or boxed in by tighter Cambridge footprints. Formal statements from Flagship Pioneering and the individual companies are still to come, and more details on lab build-outs and exact move dates are likely as those plans are finalized.
The Boston Business Journal first reported the relocations and initial tenant list. This story will be updated as additional information is released.
