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 joint venture led by Boylston Properties and institutional investors advised by J.P. Morgan Asset Management has closed a refinancing package that includes a $25.2 million mezzanine loan from Tishman Speyer alongside a $94.0 million senior loan from Landesbank Baden‑Württemberg (LBBW). The financing repays a 2021 construction loan and supports leasing costs tied to a newly signed tenant.
The mezzanine loan marks the first investment from Tishman Speyer’s newly launched real estate debt platform, a capital vehicle aimed at backing institutional‑quality projects across major U.S. cities. The platform will provide mezzanine loans, preferred equity, construction financing, and acquire loan portfolios as part of its lending toolkit.
The financing was provided to the ownership group of 500 Forge, a three‑story, roughly 162,000‑square‑foot lab and office building within the Arsenal Yards campus on the edge of West Cambridge and Allston. Proceeds were used mainly to retire the 2021 construction loan and to fund contractual leasing costs associated with a new tenant lease involving Mariana Oncology, a subsidiary of Novartis.
500 Forge was completed in 2023 and is now fully leased. Current occupants include Mariana Oncology, Orna Therapeutics, and AvenCell Therapeutics. The building delivers advanced lab and office space with interior ceiling heights ranging from 15 to 18 feet, outdoor balconies, and covered parking.
The building benefits from proximity to regional research institutions, venture capital firms, and a deep skilled workforce, positioning it well for life science tenants. Arsenal Yards itself is an innovation‑driven mixed‑use campus offering more than 1 million square feet of labs, offices, retail, restaurants, and wellness amenities. The master plan calls for over 50 retailers and restaurants, a seven‑screen theater, more than 300 residences, a hotel, and expanded public spaces tied to a revitalized Arsenal Park and a multi‑use bike path.
Boylston Properties recently announced that cell therapy company SQZ Biotech signed a 63,477‑square‑foot lease at Arsenal Yards and will expand its operations there after completing a $72 million Series C and extending a collaboration with Roche. This deal will significantly increase SQZ’s footprint in Watertown and underscores a trend of growing life science demand in the area, with multiple leases completed over the past 18 months.
The refinancing was arranged by JLL Capital Markets’ Debt Advisory team. Boylston Properties is developing Arsenal Yards with partners Wilder and J.P. Morgan. Tishman Speyer continues to expand its Boston presence, developing the Harvard Enterprise Research Campus in Allston and having previously delivered a fully leased life science project called The 105 through its Breakthrough Properties joint venture. Breakthrough Properties also holds other Boston sites including 232 A Street and One Canal in East Cambridge.
The transaction illustrates how sponsors and lenders are structuring layered capital to support life science assets that are fully leased but still need to convert construction financing into longer‑term capital and satisfy lease‑related obligations. The new Tishman Speyer debt platform is positioning itself to meet these needs by combining market expertise and lender relationships to back specialized assets in core markets.
The refinancing package includes a $25.2 million mezzanine loan from Tishman Speyer and a $94.0 million senior loan from LBBW, used mainly to retire a 2021 construction loan and fund leasing costs tied to a new tenant.
The property is owned by a joint venture led by Boylston Properties with institutional investors advised by J.P. Morgan Asset Management.
This mezzanine loan is the first investment from Tishman Speyer’s new real estate debt platform, which is targeting institutional‑quality projects and offering products such as mezzanine loans, preferred equity, construction financing, and loan portfolio acquisitions.
500 Forge is a three‑story, roughly 162,000‑square‑foot lab and office building completed in 2023, with high ceilings, outdoor balconies, and covered parking. It is fully leased to life science and biotech tenants.
Arsenal Yards is a mixed‑use campus with lab and office space, retail, restaurants, a theater, residences, and a hotel. Recent activity includes a large lease by SQZ Biotech and ongoing development of public spaces and connectivity to the local bike path.
| Feature | Detail |
|---|---|
| Location | 500 Forge, Arsenal Yards, Watertown, MA (edge of West Cambridge and Allston) |
| Loan package | $25.2M mezzanine (Tishman Speyer) + $94.0M senior (LBBW) |
| Borrower/Owner | JV led by Boylston Properties and institutional investors advised by J.P. Morgan Asset Management |
| Use of proceeds | Retire 2021 construction loan; fund leasing costs tied to Mariana Oncology lease |
| Building size & age | ~162,000 SF, 3 stories, completed 2023 |
| Tenants | Mariana Oncology (Novartis subsidiary), Orna Therapeutics, AvenCell Therapeutics |
| Campus | Arsenal Yards — >1M SF mixed-use, lab/office inventory, retail, residences, theater, hotel |
| Refinancing arranger | JLL Capital Markets Debt Advisory team |
| Strategic note | First investment from Tishman Speyer’s new real estate debt platform targeting institutional projects |
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