Upstream Bio, Inc. Leases Disclosure
7. Leases
As of December 31, 2025, the Company was a party to a lease related to commercial real estate under a non-cancelable lease term and a short-term lease related to commercial real estate.
In July 2024, the Company entered into an operating lease agreement for office space located at 890 Winter Street in Waltham, Massachusetts. The lease commenced in September 2024 and the Company began paying monthly rent starting one month after the lease commenced. The Company occupies approximately 16,801 square feet of space under a three-year agreement expiring in October 2027. Initial base rent was approximately $0.7 million for the first year and approximately $0.8 million for the second and third year.
During the year ended December 31, 2024, the Company had an operating lease for office space at 460 Totten Pond Road, Waltham, Massachusetts. In July 2024, the Company provided notice of termination. This notice became effective on October 9, 2024, after which the Company’s rights and obligations under this lease ceased. The lease expired on June 30, 2024, after which the Company continued to pay rent on a month-to-month basis until October 9, 2024. Under its lease, the Company pays a proportional share of operating expenses. Such operating expenses are subject to annual adjustment and are accounted for as variable payments in the period in which they are incurred.
The components of lease cost, which are included in the consolidated statements of operations and comprehensive loss, were as follows (in thousands):
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December 31, |
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2025 |
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2024 |
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Lease Cost: |
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Operating lease cost |
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$ |
739 |
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|
$ |
256 |
|
Short-term lease cost |
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— |
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|
|
202 |
|
Variable lease cost |
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|
— |
|
|
|
19 |
|
Total lease cost |
|
$ |
739 |
|
|
$ |
477 |
|
Supplemental disclosure of cash flow information related to leases were as follows (in thousands):
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December 31, |
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2025 |
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2024 |
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Cash paid for amounts included in the measurement of lease liabilities |
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$ |
742 |
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|
$ |
207 |
|
The weighted-average discount rate and remaining lease term were as follows:
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December 31, |
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2025 |
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2024 |
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||
Weighted-average discount rate — operating leases |
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|
11.7 |
% |
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|
11.7 |
% |
Weighted-average remaining lease term — operating leases |
|
|
1.8 |
|
|
|
2.8 |
|
The maturities of operating lease liabilities were as follows (in thousands):
Year Ended December 31, |
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Amount |
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2026 |
|
|
|
|
759 |
|
2027 |
|
|
|
|
644 |
|
Total lease payments |
|
|
|
|
1,403 |
|
Less: imputed interest |
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|
|
|
(134 |
) |
Present value of lease liabilities |
|
|
|
|
1,269 |
|
Less: operating lease liabilities, current portion |
|
|
|
|
(720 |
) |
Operating lease liabilities, net of current portion |
|
|
|
$ |
549 |
|
Historical Timeline
| Fiscal Year | Filed | |
|---|---|---|
| 2025 | Mar 26, 2026 | Showing above |
| 2024 | Mar 12, 2025 | |
About Leases Disclosures
Lease disclosures under ASC 842 provide a comprehensive view of a company's leased asset portfolio, including the split between operating and finance leases, discount rates used to present-value future payments, and the maturity schedule of lease obligations. This section reveals a significant source of off-balance-sheet commitments that were largely hidden before the current standard.
Key signals: the weighted-average discount rate affects the size of recorded lease liabilities — a higher rate reduces the reported obligation, so compare the chosen rate against the company's incremental borrowing rate. The operating versus finance lease mix affects both EBITDA and operating income presentation. Watch the maturity table for concentration risk: large payment cliffs in specific years may create cash flow pressure. Variable lease payments excluded from the liability measurement represent real obligations that do not appear on the balance sheet. Compare total lease costs against prior-year operating lease expense to assess the true economic burden.