12. Collaboration Agreements

Research Collaboration Agreement with ARTBIO, Inc.

In May 2024, the Company entered into a research collaboration agreement with ARTBIO, Inc. (“ARTBIO”) to co-develop multiple Helicon-enabled alpha particle radioligand therapies (HEARTs) for the treatment of cancer. Under the terms of this agreement, the Company is responsible for equally participating on joint committees and carrying out at least four research programs with respect to each collaboration target. The Company and ARTBIO share in the costs of the research programs equally, with ARTBIO responsible for funding the first $10.0 million of development costs incurred by both parties and the Company responsible for funding the next $10.0 million of development costs. Any further development costs beyond these initial funding amounts will also be shared equally by both parties. Under certain circumstances, either party can terminate the agreement, or opt out of further participation in any research programs, and the Company may be obligated to refund, to ARTBIO, amounts received during the initial funding periods, such that the total costs incurred through the effective date of termination would be shared equally.

Upon later regulatory approval and commercialization of related product(s), the parties will share equally in all net profits or losses. The agreement expires upon (1) the date on which products arising from the collaboration are no longer commercialized or developed for commercialization, or (2) termination by one or both parties.

The Company determined the agreement was a collaboration arrangement under ASC Topic 808, Collaborative Arrangements. The agreement provides for the parties to jointly oversee and actively participate in the research and development activities under the agreement. In addition, both parties are exposed to the significant risks and potential rewards under the agreement.

No costs were incurred by the Company during the three and six months ended June 30, 2026. During the three and six months ended June 30, 2025, the Company incurred $0.8 million and $2.4 million, respectively, in costs related to the research programs within the scope of the agreement, which have been fully reimbursed by ARTBIO. Pursuant to the contract termination and funding provisions noted above, and based on the current development plan, the Company recorded a liability representing its portion of the research and development expense incurred to date. No increase in the liability balance was recorded during the three and six months ended June 30, 2026. During the three and six months ended June 30, 2025, the Company recorded increases to the liability of $0.5 million and $1.4 million, respectively. The Company recorded the remaining amount of $0.3 million and $1.0 million as a reduction of research and development expenses within the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2025, respectively. As of June 30, 2026 and December 31, 2025, the liability balance totaled $2.7 million and is classified in accrued expenses and other current liabilities and other liabilities, respectively, on the condensed consolidated balance sheets.

On April 16, 2026, ARTBIO sent notice of its intent to opt out of all the research programs under the research collaboration agreement. On May 26, 2026, the Company sent a notice of termination of the research collaboration agreement to ARTBIO. No eligible costs were incurred by the Company or ARTBIO during the six months ended June 30, 2026.

License and Collaboration Agreement with Regeneron

On May 15, 2026, the Company entered into the Regeneron Agreement with Regeneron to discover, develop, and commercialize Helicons, with a particular focus on Antibody-Helicon Conjugates (“AHCs”), directed to a set of specified targets (each, a “Collaboration Target”).

Under the terms of the Regeneron Agreement and during the research term for each Collaboration Target, the Company will perform certain research and preclinical development activities, including screening, generating, testing and evaluating new Helicons and AHCs directed to such Collaboration Target (each, a “Product”). Under the Regeneron Agreement, there are five initial Collaboration Targets, with Regeneron having the right to replace up to two targets for no additional consideration and the option to nominate up to five additional Collaboration Targets, subject to an additional option payment from Regeneron. For one initial

Collaboration Target, Regeneron may add one or more additional programs with respect to such Collaboration Target, subject to payment of additional program fees. Following Regeneron’s nomination of a Product to be a “Licensed Product” during the research term for the applicable Collaboration Target (including additional Collaboration Targets), Regeneron has the sole right to advance through development, manufacturing and worldwide commercialization of Licensed Products, including clinical and regulatory strategy, pricing, and promotion.

Under the terms of the Regeneron Agreement, Regeneron agreed to make a $50.0 million upfront payment, which the Company received in June 2026, and invest $75.0 million in the Company's next equity financing if such financing occurred prior to the second anniversary of the execution of the Regeneron Agreement (the “Regeneron Equity Commitment”). The IPO triggered Regeneron’s $75.0 million equity investment whereby Regeneron purchased 4,166,666 shares of common stock in a concurrent private placement at a per share price equal to 90% of the public offering price, or $18.00 per share. For the initial Collaboration Targets, the Company is eligible to receive: (i) up to $470.0 million in development milestone payments; (ii) up to $575.0 million in regulatory milestone payments; (iii) up to $1.15 billion in commercial milestone payments; and (iv) tiered royalty payments, ranging in the high single digits to low double digits during the period commencing upon the first commercial sale of such Licensed Product in a given country and expiring on the latest of: (a) expiration of the last valid claim of a royalty term-extending patent right of such Licensed Product in such country, (b) 12 years after the first commercial sale of such Licensed Product in such country, and (c) loss of regulatory exclusivity for such Licensed Product in such country, subject to customary reductions.

Under the terms of the Regeneron Agreement, the Company is subject to an exclusivity obligation for each Collaboration Target until the last to expire royalty term for Licensed Products directed to such Collaboration Target. Unless earlier terminated pursuant to its terms, the Regeneron Agreement will remain in effect until the expiration of the last royalty term for the last Licensed Product under the Regeneron Agreement. Regeneron has the right to terminate the Regeneron Agreement for convenience and for certain violations of the Company’s exclusivity covenants.

The Company determined that the Regeneron Agreement represents a contract with a customer within the scope of ASC 606. ASC 606 requires that share based consideration granted to a customer in connection with a revenue transaction be accounted for under ASC 718. More specifically, the discount associated with the Regeneron Equity Commitment of $8.3 million was accounted for in accordance with the guidance in ASC 718 and was recognized as a reduction of the ASC 606 transaction price upon the completion of the Company’s IPO. The Company recorded the common stock issued in conjunction with the Regeneron Equity Commitment at its fair value of $83.3 million.

The Company identified the following promises under the agreement: (i) exclusive licenses granted to Regeneron for each Collaboration Target (the “Exclusive License”) and (ii) preclinical research and development services for each Collaboration Target (the “Research Services”). In addition, the Company concluded that Regeneron’s right to replace up to two Collaboration Targets (each, a “Replacement Collaboration Target”) for no additional consideration represents material rights under the agreement.

The Company concluded that the Exclusive License and Research Services for each Collaboration Target should be combined into one performance obligation as the licenses are not capable of being distinct. Regeneron can only benefit from the license with the services to be provided by the Company which are specialized in nature. Further, the specialized services, which include the Company’s expertise using its Helicon platform to identify potential binding sites and Helicons that are capable of binding to such sites, further modify and enhance the exclusive license such that the exclusive license is not distinct in the context of the contract. As such, the Company has identified five performance obligations related to each of the five Collaboration Targets that include the combined obligation to provide an exclusive license and research services and two performance obligations related to the material right to replace two Collaboration Targets.

The transaction price, which subsequent to the recognition of the Regeneron Equity Commitment is $41.7 million, was allocated to the performance obligations on a relative selling price basis. As of June 30, 2026, the aggregate amount of the transaction price allocated to unsatisfied or partially unsatisfied performance obligations was $41.5 million. The Company expects to recognize this amount as collaboration revenue through at least 2029, although the timing of recognition will depend on the performance of the research services and the exercise or expiration of the replacement-target rights.

The Company determined the estimated standalone selling price for each Exclusive License and Research Services performance obligation using a discounted cash flow model that determined the present value of the probability weighted cash inflows and outflows associated with each Collaboration Target. The Company determined the estimated standalone selling price for material rights by estimating the incremental costs to perform the additional services and estimating the probability the replacement right will be exercised. For sales-based milestones and royalties, the Company will recognize revenue when the underlying product revenue is recognized by Regeneron. All other contingent payments are fully constrained as of June 30, 2026, as the achievement of the milestones underlying such contingent payments is based on either the Company or Regeneron’s ability to execute under the research plans, which is not certain at contract inception.

Revenue associated with the Exclusive License and Research Services performance obligations is recognized as the underlying services are provided as control is transferred over time. The Company measures progress based on the amount of costs incurred relative to the total costs expected to fulfill the combined performance obligation. In management’s judgment, this input method is the

best measure of progress towards satisfying the combined performance obligation and reflects a faithful depiction of the transfer of goods and services. Revenue associated with the material rights will be recognized upon expiry if the option is not exercised. The amounts allocated to the material rights, if exercised, will be recognized over the period of performance of the underlying performance obligations.