Note 8. Commitments and Contingencies

Cystic Fibrosis Foundation Agreement

On September 25, 2023, the Company amended its Development Program Letter Agreement, dated May 16, 2017 and as amended July 13, 2018 and August 1, 2019, with the Cystic Fibrosis Foundation (“CFF”). Pursuant to the amendment, (i) CFF increased the amount it will award to advance LUNAR-CF to $24.6 million from approximately $15.6 million, and (ii) the Company agreed to incur at least $15.0 million toward activities under the research plan. During the fourth quarter of 2023, the Company received the full payment from CFF related to the amendment. Total contra expense recognized was $0.2 million and $0.5 million for the three and six months ended June 30, 2026 respectively, and $0.3 million and $0.7 million for the three and six months ended June 30, 2025, respectively. As of June 30, 2026 and December 31, 2025, $5.9 million and $6.4 million, respectively, remained in accrued liabilities.

Thermo Fisher Agreement

In June 2026, the Company entered into a series of agreements with Thermo Fisher Scientific Inc. (“Thermo Fisher”) and certain of Thermo Fisher’s affiliates to establish a strategic collaboration for the provision of contract development and manufacturing organization (“CDMO”) and contract research organization (“CRO”) services in connection with the development of ARCT-032, our investigational mRNA therapeutic for cystic fibrosis (“CF”). Under the agreement, Thermo Fisher has agreed to provide qualifying clinical manufacturing services with an aggregate value of up to $40.0 million. Upon the Company's decision to advance ARCT-032 into Phase 3 clinical development, the Company has agreed to engage Thermo Fisher's affiliate, PPD, Inc. (“PPD”), to perform

qualifying clinical research organization ("CRO") services for an aggregate value of up to $40.0 million for the Phase 3 clinical trial and related open-label extension study.

The agreement also contemplates that, following regulatory approval of ARCT-032 and subject to execution of a future commercial supply agreement and Thermo Fisher's continued ability to manufacture ARCT-032 in compliance with applicable regulatory requirements, Thermo Fisher would receive certain exclusive commercial manufacturing rights. As of June 30, 2026, no commercial supply agreement had been executed and no amounts had been recognized related to these provisions.

Leases

In October 2017, the Company entered into a non-cancellable operating lease agreement for office space adjacent to its previously occupied headquarters. The commencement of the lease began in March 2018 and the lease extended for approximately 84 months from the commencement date with a remaining lease term through March 2025. In March 2024, the Company negotiated with the lessor to extend the lease through March 2027. Monthly rental payments are due under the lease and there are escalating rent payments during the term of the lease. The Company is also responsible for its proportional share of operating expenses of the building and common areas. In conjunction with the new lease, the Company received free rent for four months and received a tenant improvement allowance of $0.1 million. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $0.1 million upon executing the lease which is included (along with additional funds required to secure the letter of credit) in the balance of non-current restricted cash.

In December 2025, the Company vacated this office space with no intention of operating out of the location in the future. The Company remains obligated to make the remaining lease payments through March 2027. An impairment loss of $1.9 million was recorded for this lease in the year ended December 31, 2025.

In September 2021, the Company entered into a non-cancellable lease agreement for office, research and development, engineering and laboratory space near its current headquarters, and such lease term commenced during the second quarter of 2022. The initial term of this lease extends ten years and eight months from the date of possession, and the Company has the right to extend the term of the lease for an additional five-year period. When the lease term was determined for the operating lease right-of-use assets and lease liabilities, the extension option for the lease was not included. The lease has a monthly base rent ranging from $0.3 million to $0.4 million which escalates over the lease term. The Company received a free rent period of four months and also pays for various operating costs, including utilities and real property taxes. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $2.0 million upon executing the lease which is included (along with additional funds required to secure the letter of credit) in the balance of non-current restricted cash.

Operating lease right-of-use assets and liabilities on the consolidated balance sheets represent the present value of remaining lease payments over the remaining lease terms. The Company does not allocate lease payments to non-lease components; therefore, payments for common-area-maintenance and administrative services are not included in the operating lease right-of-use assets and liabilities. The Company uses its incremental borrowing rate to calculate the present value of the lease payments, as the implicit rate in the lease is not readily determinable.

Operating lease costs consist of the fixed lease payments included in operating lease liabilities and are recorded on a straight-line basis over the lease terms. Operating lease costs were $0.9 million and $1.9 million for the three and six months ended June 30, 2026, respectively, and $1.3 million and $2.5 million for the three and six months ended June 30, 2025, respectively.