License And Collaboration Agreements	12 Months Ended
Dec. 31, 2022
License and collaboration agreements [Abstract]
License and Collaboration Agreements	3. LICENSE AND COLLABORATION AGREEMENTS Asset Acquisition In May 2022, we obtained worldwide exclusive rights to RLYB331, with Kymab Limited ("Sanofi") a preclinical antibody. We believe RLYB331 has the potential to address a significant unmet need for patients with severe anemias with ineffective erythropoiesis and iron overload, including beta thalassemia and a subset of lower risk myelodysplastic syndromes. Under the terms of the license agreement, we made an upfront payment to Sanofi of $3.0 million in the second quarter of 2022 for the exclusive license to KY1066. We could also be required to pay up to an aggregate of $43.0 million in development and regulatory milestones and up to an aggregate of $150.0 million in commercial milestones for a product in its first indication, plus tiered low-to-mid double digit percentages of such milestone amounts for up to three additional indications, and mid to high single digit royalties on net sales. The license was accounted for as an asset acquisition as substantially all of the fair value of the asset acquired was concentrated in a single asset and thus the acquisition was deemed not to be a business combination. The acquired license rights represent an IPR&D asset that was determined to have no alternative future use. Accordingly, the Company recorded an IPR&D charge of $3.1 million to research and development expense, including transaction costs associated with this asset acquisition of $0.1 million, in the accompanying consolidated statements of operations and comprehensive loss for the year ended December 31, 2022. AbCellera Collaboration In December 2022, the Company entered into a multi-year, multi-target collaboration with AbCellera to discover, develop, and commercialize novel antibody-based therapeutics for rare diseases. Under the terms of the agreement, AbCellera and Rallybio will co-develop and share the development costs of up to five rare disease therapeutic targets, which will be chosen together by both companies. At the point one party in the collaboration opts-out of future co-development cost sharing, that party will be entitled to a share of future profit sharing from commercialization of the collaboration target, dependent on the proportion of their co-development contributions compared to the total development costs of a target as defined within the agreement. The agreement also has defined profit sharing floors that correspond to the stage of development at the time a collaboration party opts-out of co-developing a target. The Company concluded that the agreement with AbCellera will be accounted under the scope of ASC 808 as both parties will actively participate in joint operating activities and are exposed to significant risks and rewards that depend on the commercial success of those activities. Under ASC 808, certain transactions between collaborative arrangement participants should follow the accounting for revenue under ASC 606 when the collaborative arrangement participant is a customer. The Company determined that co-development arrangement as defined in our agreement with AbCellera does not meet the definition of a customer as defined by ASC 606. As a result, these activities will be accounted for as research and development costs. Payments due because of the co-development will be recorded as research and development expense in the period such expenses are incurred and for payments owed to us from our collaboration partner for the reimbursement of research and development costs will be recorded as a contra-research and development expense in the period such expenses are incurred. Costs related to the AbCellera collaboration were not material for the year ended December 31, 2022.

License And Collaboration Agreements

12 Months Ended

Dec. 31, 2022

License and collaboration agreements [Abstract]

3. LICENSE AND COLLABORATION AGREEMENTS

Asset Acquisition

In May 2022, we obtained worldwide exclusive rights to RLYB331, with Kymab Limited ("Sanofi") a preclinical antibody. We believe RLYB331 has the potential to address a significant unmet need for patients with severe anemias with ineffective erythropoiesis and iron overload, including beta thalassemia and a subset of lower risk myelodysplastic syndromes. Under the terms of the license agreement, we made an upfront payment to Sanofi of $3.0 million in the second quarter of 2022 for the exclusive license to KY1066. We could also be required to pay up to an aggregate of $43.0

million in development and regulatory milestones and up to an aggregate of $150.0 million in commercial milestones for a product in its first indication, plus tiered low-to-mid double digit percentages of such milestone amounts for up to three additional indications, and mid to high single digit royalties on net sales.

The license was accounted for as an asset acquisition as substantially all of the fair value of the asset acquired was concentrated in a single asset and thus the acquisition was deemed not to be a business combination. The acquired license rights represent an IPR&D asset that was determined to have no alternative future use. Accordingly, the Company recorded an IPR&D charge of $3.1 million to research and development expense, including transaction costs associated with this asset acquisition of $0.1 million, in the accompanying consolidated statements of operations and comprehensive loss for the year ended December 31, 2022.

AbCellera Collaboration

In December 2022, the Company entered into a multi-year, multi-target collaboration with AbCellera to discover, develop, and commercialize novel antibody-based therapeutics for rare diseases. Under the terms of the agreement, AbCellera and Rallybio will co-develop and share the development costs of up to five rare disease therapeutic targets, which will be chosen together by both companies. At the point one party in the collaboration opts-out of future co-development cost sharing, that party will be entitled to a share of future profit sharing from commercialization of the collaboration target, dependent on the proportion of their co-development contributions compared to the total development costs of a target as defined within the agreement. The agreement also has defined profit sharing floors that correspond to the stage of development at the time a collaboration party opts-out of co-developing a target.

The Company concluded that the agreement with AbCellera will be accounted under the scope of ASC 808 as both parties will actively participate in joint operating activities and are exposed to significant risks and rewards that depend on the commercial success of those activities. Under ASC 808, certain transactions between collaborative arrangement participants should follow the accounting for revenue under ASC 606 when the collaborative arrangement participant is a customer.

The Company determined that co-development arrangement as defined in our agreement with AbCellera does not meet the definition of a customer as defined by ASC 606. As a result, these activities will be accounted for as research and development costs. Payments due because of the co-development will be recorded as research and development expense in the period such expenses are incurred and for payments owed to us from our collaboration partner for the reimbursement of research and development costs will be recorded as a contra-research and development expense in the period such expenses are incurred. Costs related to the AbCellera collaboration were not material for the year ended December 31, 2022.