In July 2021, the Company entered into a non-cancelable operating lease agreement pursuant to which the Company leased its principal office facility in Boston, Massachusetts at 225 Franklin Street ("225 Lease"). The 225 Lease commencement date was January 1, 2022 and the lease term runs through December 31, 2026. The 225 Lease does not contain any options for renewal or extension.

In connection with the 225 Lease commencement, the Company recorded a ROU asset and operating lease liability of $2,938 and $2,873 as of January 1, 2022.

The following assets and liabilities are recorded on the consolidated balance sheet as of December 31, 2025 and 2024.


	As of December 31,
	2025		2024
Right-of-use asset	$	634	$	1,243
Current operating lease liability		843		800
Non-current operating lease liability		—		842

The components of the lease expense which are allocated between the general and administrative expenses and the research and development expenses on the consolidated statement of operations and comprehensive loss for the years ended December 31, 2025 and 2024 were as follows:


	Year Ended December 31,
	2025		2024
Operating lease costs	$	646	$	646
Variable lease costs		62		56
Total lease costs	$	708	$	702

The variable lease costs for the years ended December 31, 2025 and 2024 include common area maintenance and other operating charges associated with the 225 Lease. As the 225 Lease does not provide an implicit rate, the Company utilized its incremental borrowing rate to discount lease payments, which reflects the fixed rate at which the Company estimates it could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment.


	As of December 31,
	2025			2024
Remaining lease term (in years)		1.0			2.0
Discount rate	3.1		%	3.1		%

Future minimum payments under the 225 Lease, the Company’s only operating lease as of December 31, 2025 were as follows:


As of December 31, 2025
2026	$	855
Total lease payments		855
Less amount representing implied interest		(12	)
Total lease liability	$	843
Current portion of operating lease liabilities		843
Noncurrent portion of operating lease liabilities	$	—

Rent expense recognized was $646 for the years ended December 31, 2025 and 2024.

The Company maintains a deposit of $131 and $197, respectively, with the landlord, which is included in other assets in the consolidated balance sheets as of December 31, 2025 and 2024.

In December 2021, the Company entered into a license agreement (“Merck License Agreement”) with MSD International GmbH, an affiliate of Merck & Co, Inc. (“Merck”) for the development, manufacture and commercialization of ruzasvir. Ruzasvir is the NS5A inhibitor the Company is developing in combination with bemnifosbuvir for the treatment of HCV.

Pursuant to the terms of the Merck License Agreement, the Company obtained from Merck a worldwide exclusive (subject to certain reserved rights to conduct internal research) and sublicensable license under certain Merck patents and know-how to research, develop, manufacture, have manufactured, use, import, export, sell, offer for sale, and otherwise commercialize ruzasvir or products containing ruzasvir (each a “Product”) for all therapeutic or prophylactic uses in humans.

In addition to a non-refundable upfront payment that the Company made in February 2022, the Company agreed to pay Merck milestone payments upon its achievement of certain development, regulatory and sales-based milestones. Additionally, the Company will pay Merck tiered royalties based on annual net sales of Products ranging from high single digits to mid-teens percentages. The Company’s royalty payment obligations will continue until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country. The Company may terminate the Merck License Agreement for convenience upon prior written notice. The first milestone in the amount of $5,000 became due and payable and the related expense was recognized in April 2025 upon the initiation of the HCV Phase 3 clinical trial referred to as C-Beyond. The next potential milestone under the Merck License Agreement, in the amount of $10,000, is payable upon the acceptance by the US Food and Drug Administration of a new drug application covering a product candidate including ruzasvir which the Company expects will be the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV.

The Company has an agreement with a consultant that requires payment of a success fee calculated as a percentage of certain product sales, subject to a cumulative maximum payout of $5,000. This success payment is contingent upon the occurrence of future events and the timing and likelihood of such payment is neither probable nor estimable.

The Company enters into certain types of contracts that contingently requires the Company to indemnify various parties against claims from third parties. These contracts primarily relate to (i) the Company’s bylaws, under which the Company must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship with the Company, (ii) contracts under which the Company must indemnify directors and certain officers and consultants for liabilities arising out of their relationship with the Company, and (iii) procurement, service or license agreements under which the Company may be required to indemnify vendors, service providers or licensees for certain claims, including claims that may be brought against them arising from the Company’s acts or omissions with respect to the Company’s products, technology, intellectual property or services.

From time to time, the Company may receive indemnification claims under these contracts in the normal course of business. In the event that one or more of these matters were to result in a claim against the Company, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on the Company’s future business, operating results or financial condition. It is not possible to determine the maximum potential amount payable under these contracts since the Company has no history of prior indemnification claims and the unique facts and circumstances involved in each particular claim will be determinative.

The Company is not currently party to, or aware of, any material legal proceedings. If the Company were to become a party to or aware of a material legal proceeding, at each reporting date, the Company would evaluate whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company would expense as incurred the costs related to any such legal proceedings.