Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 333

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 333
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 2020 for a 12-monthperiod and was classified as a short-term lease. The Natick Lease was subsequently extended three times and the lease term ended in June 2023. Waltham, Massachusetts In May 2022, the Company entered into a noncancelable facility lease agreement to lease 24,051 square feet of office and laboratory space in Waltham, Massachusetts (“Waltham Lease”), which became the Company headquarters in January 2023 following the completion of construction of the prebuilt office and lab space, and when the Company received full access and control over the leased space. Upon execution of the Waltham Lease, the Company was required to prepay $0.2 million, which was included in the prepaid expenses and other current assets as of December 31, 2022 and included in the initial measurement of the right-of-useasset in 2023 when the Waltham Lease commenced. At commencement of the lease the right-of-useasset was $9.5 million, which was reduced by $0.4 million of lease incentives, offset by $0.2 million of lease prepayments, and the lease liability was $9.7 million. F-17

The original term for the Waltham Lease is for the period from January 2023 through November 2030, and the Company has the option to extend the Waltham Lease for an additional five-year term at market-based rates. The renewal option is not reasonably certain to occur, and as such, it was not considered in the measurement of the right-of-useasset and lease liability. The Waltham Lease has escalating base rent payments, which commenced in September 2023 and continue through the expiration of the lease. The Company received eight months of free rent and five additional months of 50% rent abatement. The Company is responsible for other fixed and variable payments including operating expenses and property taxes. Per the terms of the Waltham Lease, the Landlord agreed to construct $0.4 million of leasehold improvements that the Company concluded were the landlord’s asset and therefore were not recorded by the Company. In addition, the Landlord provided the Company an option to finance up to $0.4 million (the “TI Option”) in additional leasehold improvements over the lease term at a 9% per annum interest rate through higher rent payments. The Company exercised the TI Option in June 2022, and the Waltham Lease was amended to account for the increase in rental payments. The