500 Forge, a three-story life science building at Arsenal Yards, refinanced with a Tishman Speyer mezzanine loan
Watertown, MA, August 16, 2025
Tishman Speyer closed a $25.2 million mezzanine loan to refinance 500 Forge at Arsenal Yards, paired with a $94.0 million senior loan from LBBW. The financing, provided to a joint venture led by Boylston Properties with institutional investors advised by J.P. Morgan Asset Management, primarily retired a 2021 construction loan and funded leasing costs tied to a new Mariana Oncology lease. This marks the first investment from Tishman Speyer’s new real estate debt platform. 500 Forge is a three‑story, 162,000 sq ft life science building completed in 2023 and now fully leased to life science tenants.
Watertown, MA — A new financing package has been completed for 500 Forge, a three-story life science building at Arsenal Yards. The package includes a $25.2 million mezzanine loanTishman Speyer and a $94.0 million senior loan from Landesbank Baden‑Württemberg (LBBW). The mezzanine portion is the first investment launched from Tishman Speyer’s new real estate debt platform, which is targeting institutional-quality projects across major U.S. cities.
The proceeds will be used mainly to retire a 2021 construction loan on the fully leased property and to cover leasing costs tied to a newly signed tenant, Mariana Oncology, a subsidiary of Novartis. The mezzanine loan was provided to a joint venture led by Boylston Properties along with institutional investors advised by J.P. Morgan Asset Management. The refinancing was arranged by JLL Capital Markets’ Debt Advisory team.
The deal highlights a growing appetite for life science lending that can support completed, income-producing lab buildings. The mezzanine investment by the new platform signals a push by an established developer and investor to expand into debt products such as mezzanine loans, preferred equity, construction financing and loan portfolio acquisitions.
500 Forge sits at the edge of West Cambridge and Allston in East Watertown and was completed in 2023. The building has roughly 162,000 square feet across three stories and is now fully leased. Tenants include Mariana Oncology, Orna Therapeutics, and AvenCell Therapeutics. The building offers advanced lab and office space, outdoor balconies, covered parking and interior ceiling heights that range from 15 to 18 feet.
Arsenal Yards is a larger mixed-use, innovation-focused campus with more than 1 million square feet of labs, offices, retail, restaurants and wellness amenities. The master plan calls for more than 50 retailers and restaurants, a seven-screen theater, over 300 residences, a 150-room hotel and substantial open public spaces that connect to a revitalized Arsenal Park and the nearby multi-use bike path.
The campus continues to attract lab tenants. Recently, a cell therapy company, SQZ Biotech, signed a 63,477-square-foot lease at Arsenal Yards and plans to relocate and expand there later this year. SQZ completed a $72 million Series C financing and expanded a clinical and commercial collaboration with a major pharma partner, strengthening its growth case. Local brokers reported that the SQZ lease is part of a broader trend of life science firms moving into Watertown, marking the sixth new life science lease in the area over the past 18 months.
Boylston Properties, a Boston-based developer, leads the JV that owns 500 Forge and is a co-developer of Arsenal Yards alongside Wilder and investors advised by J.P. Morgan Asset Management. Boylston has a long track record of mixed-use and life science projects in Greater Boston, including nearby lab buildings such as LINX, a fully leased 185,000-square-foot project across the street. Tishman Speyer is active in the Boston market as well, currently developing a research campus in Allston and having completed other life science projects through earlier ventures.
The refinancing was put together by members of JLL Capital Markets’ Debt Advisory team. The two-tier financing — senior debt from a large European bank and a U.S.-based mezzanine from a prominent real estate operator entering debt markets — shows a blended approach to funding stabilized life science assets. The new debt platform is expected to back similar institutional-quality projects and a range of capital products going forward.
Look for continued leasing activity at Arsenal Yards and nearby Watertown properties as life science firms seek space close to research institutions, venture capital, and skilled workers. Follow-on moves may include more debt placements from the new platform and additional tenant announcements across the campus as remaining space is taken up.
The package includes a $94.0 million senior loan from LBBW and a $25.2 million mezzanine loan provided by Tishman Speyer’s new real estate debt platform.
The mezzanine loan was provided to a joint venture led by Boylston Properties together with institutional investors advised by J.P. Morgan Asset Management.
Proceeds are primarily being used to retire a 2021 construction loan and to fund leasing costs tied to the newly executed tenant lease with Mariana Oncology.
500 Forge is a three-story building of about 162,000 square feet, completed in 2023, and is now fully leased to life science tenants.
Cell therapy company SQZ Biotech signed a 63,477-square-foot lease and plans to substantially expand its footprint at Arsenal Yards after recent financing and a collaboration update.
| Item | Detail |
|---|---|
| Property | 500 Forge at Arsenal Yards, East Watertown |
| Building size | Approximately 162,000 sq ft, three stories |
| Completion | Completed in 2023 |
| Tenants | Mariana Oncology, Orna Therapeutics, AvenCell Therapeutics |
| Senior lender | LBBW — $94.0M |
| Mezzanine lender | Tishman Speyer — $25.2M |
| Use of proceeds | Retire 2021 construction loan; fund leasing costs tied to Mariana Oncology |
| Campus size | Arsenal Yards: over 1 million sq ft of mixed uses (labs, offices, retail, residences) |
| Notable nearby activity | SQZ Biotech 63,477-sf lease; local life science growth in Watertown |
| Financing arranger | JLL Capital Markets Debt Advisory team |
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