Significant Contracts	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Contracts	6. Significant Contracts Agreements with Vertex For purposes of this Note 6 and Note 7, CASGEVY (exagamglogene autotemcel [exa-cel]) is referred to as “CASGEVY”. 2015 collaboration In 2015, the Company entered into a strategic collaboration, option and license agreement, or the 2015 Collaboration Agreement, with Vertex Pharmaceuticals Incorporated, or Vertex. The 2015 Collaboration Agreement is focused on the use of the Company’s CRISPR/Cas9 gene editing technology to discover and develop potential new treatments aimed at the underlying genetic causes of human disease. The Company and Vertex amended the 2015 Collaboration Agreement in 2017 and 2019 with Amendment No. 1 and Amendment No. 2, respectively, namely to clarify Vertex’s option rights under the 2015 Collaboration Agreement and to modify certain definitions and provisions of the 2015 Collaboration Agreement to make them consistent with the JDA (as defined below) and a strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of Duchenne muscular dystrophy, or DMD, and myotonic dystrophy type 1, or DM1. In 2017, Vertex exercised an option granted to it under the 2015 Collaboration Agreement to obtain a co-exclusive license to develop and commercialize hemoglobinopathy and beta-globin targets, and in 2019, Vertex exercised the remaining options granted to it under the 2015 Collaboration Agreement to exclusively license certain collaboration targets developed under the 2015 Collaboration Agreement. Hemoglobinopathies collaboration In 2017, following Vertex’s exercise of its option to obtain a co-exclusive license to develop and commercialize hemoglobinopathy and beta-globin targets, the Company and Vertex entered into a joint development and commercialization agreement, or the JDA, and agreed for potential hemoglobinopathy treatments, including CASGEVY, the Company and Vertex would share equally all research and development costs and worldwide revenues. In 2021, the Company and Vertex amended and restated the JDA, as amended and in effect, from time to time, or the A&R Vertex JDCA, pursuant to which the parties agreed to, among other things, (a) adjust the governance structure for the collaboration and adjust the responsibilities of each party thereunder, whereby Vertex leads and has all decision making (i.e., control) in relation to the CASGEVY program prospectively; (b) adjust the allocation of net profits and net losses between the parties with respect to CASGEVY only, which will be allocated 40% to the Company and 60% to Vertex, prospectively; and (c) exclusively license (subject to the Company’s reserved rights to conduct certain activities) certain intellectual property rights to Vertex relating to the specified product candidates and products (including CASGEVY) that may be researched, developed, manufactured and commercialized on a worldwide basis under the A&R Vertex JDCA. Additionally, for 2022, 2023, and 2024, the Company had an option to defer a portion of its share of costs under the A&R Vertex JDCA if spending on the CASGEVY program exceeded specified amounts. Any deferred amounts under the A&R Vertex JDCA are only payable to Vertex as an offset against future profitability of the CASGEVY program and the amounts payable are capped at a specified maximum amount per year. In December 2023, the Company entered into an amendment to the A&R Vertex JDCA, or Amendment No. 1 to the A&R Vertex JDCA, with Vertex related to the global development, manufacturing, and commercialization of CASGEVY. Pursuant to Amendment No. 1 to the A&R Vertex JDCA, among other things, the Company and Vertex agreed to (a) allocate certain costs arising from a license agreement with a third party, resulting in a current payment due to Vertex by the Company of $20.0 million upon an event specified in Amendment No. 1 to the A&R Vertex JDCA, and (b) adjust, under certain specified circumstances, the timing of and portion of the Company’s share of costs it is permitted to defer under the agreement. Letter Agreement In May 2024, Vertex and the Company entered into a letter agreement, or the Letter Agreement, with respect to the priority review voucher issued by the U.S. Food and Drug Administration to Vertex as the sponsor of the rare pediatric disease product application for CASGEVY. Vertex and the Company agreed that if Vertex utilizes or transfers the priority review voucher prior to the first calendar year in which the CASGEVY program generates a net profit, Vertex will pay the Company $43.0 million or an amount equal to 42% of the net proceeds from such transfer, as applicable. If the CASGEVY program begins generating calendar-year net profits prior to such utilization or transfer, Vertex will instead pay the Company up to $43.0 million set-off by deductions Vertex would otherwise be eligible to take against the CASGEVY program’s net profits due to the Company related to amounts deferred previously by the Company. Collaboration in the field of diabetes In 2021, the Company and ViaCyte, Inc., or ViaCyte, entered into a joint development and commercialization agreement, as amended and in effect, from time to time, or the ViaCyte JDCA, to jointly develop and commercialize product candidates and shared products for the diagnosis, treatment or prevention of diabetes type 1, diabetes type 2 or insulin dependent / requiring diabetes throughout the world. In the third quarter of 2022, Vertex acquired ViaCyte, and ViaCyte became a wholly-owned subsidiary of Vertex. In March 2023, (1) the Company and ViaCyte entered into an amendment to the ViaCyte JDCA, or the ViaCyte JDCA Amendment, and adjusted certain rights and obligations of the Company and ViaCyte under the ViaCyte JDCA, and (2) the Company and Vertex entered into a non-exclusive license agreement, or the Non-Ex License Agreement, pursuant to which the Company agreed to license to Vertex, on a non-exclusive basis, certain of its gene editing intellectual property to exploit certain products for the diagnosis, treatment or prevention of diabetes type 1, diabetes type 2 or insulin dependent / requiring diabetes throughout the world. Subsequently, ViaCyte elected to opt-out of the ViaCyte JDCA. Per the opt-out terms, the on-going collaboration assets are now wholly owned by the Company, subject to a royalty on future sales owed to ViaCyte. The opt-out became effective in early February 2024. Accounting Analysis For purposes of this Note 6, the 2015 Collaboration Agreement, Amendment No. 1, Amendment No. 2, A&R Vertex JDCA, and Amendment No. 1 to the A&R Vertex JDCA are collectively referred to as the “Vertex Hemoglobinopathy Agreements” and the Non-Ex License Agreement and ViaCyte JDCA Amendment are collectively referred to as the “March 2023 Diabetes Agreements.” The Vertex Hemoglobinopathy Agreements and the March 2023 Diabetes Agreements include components of a customer-vendor relationship as defined under ASC 606, Revenue from Contracts with Customers, or ASC 606, collaborative arrangements as defined under ASC 808, Collaborative Agreements, or ASC 808, and research and development costs as defined under ASC 730, Research and Development, or ASC 730. Specifically, with regards to the March 2023 Diabetes Agreements, the Company concluded that the non-exclusive license is a performance obligation under ASC 606 and the ongoing research and development services under the ViaCyte JDCA Amendment are a unit of account under ASC 808. The Company has determined that recognition criteria for the Letter Agreement has not been met and will not be met until the priority review voucher is (i) utilized or (ii) there is sufficient profitability such that Vertex is obligated to pay the Company under the Letter Agreement. Accounting Analysis Under ASC 606 Accounting for the Vertex Hemoglobinopathy Agreements Recognition of Revenue No revenue was recognized under the Vertex Hemoglobinopathy Agreements for the three and six months ended June 30, 2026 and 2025. Milestones under the Vertex Hemoglobinopathy Agreements The Company has evaluated the milestones that may be received in connection with the Vertex Hemoglobinopathy Agreements. Under the 2015 Collaboration Agreement and subsequent amendments, the Company is eligible to receive up to $410.0 million in additional development, regulatory and commercial milestones and royalties on net product sales for each of the three collaboration targets that Vertex licensed in 2019. Each milestone is payable only once per collaboration target, regardless of the number of products directed to such collaboration target that achieve the relevant milestone event. The Company has the option to conduct research at its own cost in certain defined areas. If such research is beneficial to the CASGEVY program and CASGEVY ultimately achieves regulatory approval in such areas, the Company could be entitled to receive from Vertex certain milestone payments aggregating to high eight digits. Each of the remaining milestones described above are fully constrained as of June 30, 2026. There is uncertainty as to whether the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs. Accounting Analysis under ASC 808 Vertex Hemoglobinopathy Agreements In connection with the Vertex Hemoglobinopathy Agreements, the Company identified the following collaborative elements, which are accounted for under ASC 808: (i) development and commercialization services for shared products, including any transition services related to CASGEVY under the A&R Vertex JDCA; (ii) R&D Services for follow-on products; and (iii) committee participation. The related impact of the cost sharing under the Vertex Hemoglobinopathy Agreements is included within collaboration expense, net, in the condensed consolidated statements of operations and comprehensive loss. During the three and six months ended June 30, 2026, the Company recognized $40.3 million and $86.2 million, respectively, of collaboration expense, net, related to the Vertex Hemoglobinopathy Agreements. Collaboration expense, net, during the three and six months ended June 30, 2026 was net of $3.0 million and $4.2 million, respectively, of reimbursements from Vertex. During the three and six months ended June 30, 2025, the Company recognized $45.2 million and $102.7 million of collaboration expense, net, respectively. Collaboration expense, net, during the three and six months ended June 30, 2025 was net of $0.6 million and $0.7 million of reimbursements from Vertex, respectively. Additional Accounting Considerations The Company is eligible to receive potential future payments of up to $775.0 million upon the successful achievement of specified development, regulatory and commercial milestones under a strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of DMD and DM1. The Company is also eligible to receive tiered royalties on future net sales on any products that may result from this collaboration; however, the Company has the option to forego the DM1 milestones and royalties to co-develop and co-commercialize all DM1 products globally. Each of the remaining milestones under the strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of DMD and DM1 are fully constrained as of June 30, 2026. There is uncertainty that the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs. As of June 30, 2026, there was $12.3 million of current deferred revenue, which is unchanged from December 31, 2025. The transaction price allocated to the remaining performance obligations was $12.3 million. Subsequent to June 30, 2026, the Company was notified by Vertex that it will not exercise an option granted under an amendment to the 2015 Collaboration Agreement to co-develop and co-commercialize a specified target and, as a result, the Company expects to recognize the related deferred revenue in the third quarter of 2026. As of June 30, 2026, the Company is eligible to receive potential future milestone payments from Vertex of up to $125.0 million in the aggregate under the Non-Ex License Agreement depending on the achievement of pre-determined research, development and commercial milestones for certain products utilizing the licensed intellectual property. Additionally, the Company is eligible to receive tiered royalties on the sales of certain products in the low to mid-single digits. Each of the remaining milestones under the Non-Ex License Agreement are fully constrained as of June 30, 2026. There is uncertainty as to whether the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs. Agreement with Sirius Therapeutics In May 2025, the Company entered into a collaboration, option and license agreement, or the Sirius Agreement, with Sirius Therapeutics and certain of its affiliates, or Sirius, pursuant to which, among other things, (1) Sirius and the Company will collaborate on the research, development, manufacture, commercialization and use of certain collaboration products utilizing Sirius’ siRNA technology for targeting Factor XI, including CTX611, collectively, the Sirius Collaboration Products; and (2) Sirius granted to the Company options to exclusively license Sirius siRNA technology to target up to two licensed targets from a list of seven reserved targets for the research, development, manufacture and commercialization of licensed products, collectively the siRNA Licensed Products, in exchange for the potential to receive certain option fees, milestone payments and royalties. In connection with entering into the Sirius Agreement, the Company made an upfront cash payment to Sirius of $25.0 million and also entered into a share issuance agreement with Sirius, pursuant to which the Company registered and issued to Sirius 1,842,105 common shares, nominal value CHF 0.03 per share, or common shares, equal to approximately $70.0 million based on a price per common share equal to $38.00, or the Sirius Shares. With respect to Sirius Collaboration Products, the Company and Sirius will share equally all development and commercialization costs. For the first Sirius Collaboration Product successfully developed, the Company will be the lead party responsible for Phase 3 global development and commercialization efforts in the United States and Sirius will be the lead party responsible for Phase 3 development (subject to the global development plan) and commercialization efforts in Greater China. The parties will determine the lead party responsible for commercialization in the rest of the world at a future date. The Company and Sirius will share equally net profits and net losses incurred under the Sirius Agreement with respect to all Sirius Collaboration Products, except in the event that a party opts out of the joint development and commercialization. The Company will pay Sirius certain specified future development and regulatory milestones of up to an aggregate of $87.5 million for the first Sirius Collaboration Products to achieve the applicable milestone events. At the Company’s sole election, such milestone payments may be paid in cash, common shares of the Company, or a combination thereof. With respect to the siRNA Licensed Products, if the Company elects to exercise its option to a licensed target to research, develop, manufacture and commercialize siRNA Licensed Products, the Company will make a one-time $10.0 million payment per option exercise, each, a Sirius Option Payment, to Sirius. The Sirius Option Payment is payable up to two times. In addition, the Company will pay Sirius certain specified future development, regulatory and sales milestones of up to an aggregate of $300.0 million for the first siRNA Licensed Product relating to each licensed target to achieve the applicable milestone events, as well as tiered royalty payments in the mid-single digits to low double digits range on future sales of a commercialized siRNA Licensed Product. The royalty payments are subject to reduction under certain specified conditions set forth in the Sirius Agreement. In addition, at the Company’s sole election, such milestones may be paid in cash, common shares of the Company, or a combination thereof. The Company is solely responsible for all research, development, manufacturing and global commercialization activities and associated costs for the siRNA Licensed Products, as well as all associated costs related to Sirius activities set forth in any applicable research plan relating thereto. Accounting for the Sirius Agreement The Sirius Agreement includes components of collaborative arrangements as defined under ASC 808 and research and development costs as defined under ASC 730. Specifically, development and commercialization costs for the Sirius Collaboration Products contain collaborative elements accounted for under ASC 808, and the related impact of cost sharing for the Sirius Collaboration Products under the Sirius Agreement is included within research and development expenses in the condensed consolidated statements of operations and comprehensive loss. Costs related to siRNA Licensed Products under the Sirius Agreement are included within research and development expenses in the consolidated statement of operations and comprehensive loss. Research and development costs under the Sirius Agreement related to the Sirius Collaboration Products were $3.4 million and $5.0 million for the three and six months ended June 30, 2026, respectively, and were net of $0.5 million and $0.7 million in reimbursements from Sirius, respectively. Research and development costs under the Sirius Agreement related to the siRNA Licensed Products were not material for the three and six months ended June 30, 2026. All research and development costs under the Sirius Agreement were not material for the three and six months ended June 30, 2025.

Significant Contracts

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

6. Significant Contracts

Agreements with Vertex

For purposes of this Note 6 and Note 7, CASGEVY (exagamglogene autotemcel [exa-cel]) is referred to as “CASGEVY”.

2015 collaboration

In 2015, the Company entered into a strategic collaboration, option and license agreement, or the 2015 Collaboration Agreement, with Vertex Pharmaceuticals Incorporated, or Vertex. The 2015 Collaboration Agreement is focused on the use of the Company’s CRISPR/Cas9 gene editing technology to discover and develop potential new treatments aimed at the underlying genetic causes of human disease. The Company and Vertex amended the 2015 Collaboration Agreement in 2017 and 2019 with Amendment No. 1 and Amendment No. 2, respectively, namely to clarify Vertex’s option rights under the 2015 Collaboration Agreement and to modify certain definitions and provisions of the 2015 Collaboration Agreement to make them consistent with the JDA (as defined below) and a strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of Duchenne muscular dystrophy, or DMD, and myotonic dystrophy type 1, or DM1. In 2017, Vertex exercised an option granted to it under the 2015 Collaboration Agreement to obtain a co-exclusive license to develop and commercialize hemoglobinopathy and beta-globin targets, and in 2019, Vertex exercised the remaining options granted to it under the 2015 Collaboration Agreement to exclusively license certain collaboration targets developed under the 2015 Collaboration Agreement.

Hemoglobinopathies collaboration

In 2017, following Vertex’s exercise of its option to obtain a co-exclusive license to develop and commercialize hemoglobinopathy and beta-globin targets, the Company and Vertex entered into a joint development and commercialization agreement, or the JDA, and agreed for potential hemoglobinopathy treatments, including CASGEVY, the Company and Vertex would share equally all research and development costs and worldwide revenues. In 2021, the Company and Vertex amended and restated the JDA, as amended and in effect, from time to time, or the A&R Vertex JDCA, pursuant to which the parties agreed to, among other things, (a) adjust the governance structure for the collaboration and adjust the responsibilities of each party thereunder, whereby Vertex leads and has all decision making (i.e., control) in relation to the CASGEVY program prospectively; (b) adjust the allocation

of net profits and net losses between the parties with respect to CASGEVY only, which will be allocated 40% to the Company and 60% to Vertex, prospectively; and (c) exclusively license (subject to the Company’s reserved rights to conduct certain activities) certain intellectual property rights to Vertex relating to the specified product candidates and products (including CASGEVY) that may be researched, developed, manufactured and commercialized on a worldwide basis under the A&R Vertex JDCA. Additionally, for 2022, 2023, and 2024, the Company had an option to defer a portion of its share of costs under the A&R Vertex JDCA if spending on the CASGEVY program exceeded specified amounts. Any deferred amounts under the A&R Vertex JDCA are only payable to Vertex as an offset against future profitability of the CASGEVY program and the amounts payable are capped at a specified maximum amount per year.

In December 2023, the Company entered into an amendment to the A&R Vertex JDCA, or Amendment No. 1 to the A&R Vertex JDCA, with Vertex related to the global development, manufacturing, and commercialization of CASGEVY. Pursuant to Amendment No. 1 to the A&R Vertex JDCA, among other things, the Company and Vertex agreed to (a) allocate certain costs arising from a license agreement with a third party, resulting in a current payment due to Vertex by the Company of $20.0 million upon an event specified in Amendment No. 1 to the A&R Vertex JDCA, and (b) adjust, under certain specified circumstances, the timing of and portion of the Company’s share of costs it is permitted to defer under the agreement.

Letter Agreement

In May 2024, Vertex and the Company entered into a letter agreement, or the Letter Agreement, with respect to the priority review voucher issued by the U.S. Food and Drug Administration to Vertex as the sponsor of the rare pediatric disease product application for CASGEVY. Vertex and the Company agreed that if Vertex utilizes or transfers the priority review voucher prior to the first calendar year in which the CASGEVY program generates a net profit, Vertex will pay the Company $43.0 million or an amount equal to 42% of the net proceeds from such transfer, as applicable. If the CASGEVY program begins generating calendar-year net profits prior to such utilization or transfer, Vertex will instead pay the Company up to $43.0 million set-off by deductions Vertex would otherwise be eligible to take against the CASGEVY program’s net profits due to the Company related to amounts deferred previously by the Company.

Collaboration in the field of diabetes

In 2021, the Company and ViaCyte, Inc., or ViaCyte, entered into a joint development and commercialization agreement, as amended and in effect, from time to time, or the ViaCyte JDCA, to jointly develop and commercialize product candidates and shared products for the diagnosis, treatment or prevention of diabetes type 1, diabetes type 2 or insulin dependent / requiring diabetes throughout the world. In the third quarter of 2022, Vertex acquired ViaCyte, and ViaCyte became a wholly-owned subsidiary of Vertex. In March 2023, (1) the Company and ViaCyte entered into an amendment to the ViaCyte JDCA, or the ViaCyte JDCA Amendment, and adjusted certain rights and obligations of the Company and ViaCyte under the ViaCyte JDCA, and (2) the Company and Vertex entered into a non-exclusive license agreement, or the Non-Ex License Agreement, pursuant to which the Company agreed to license to Vertex, on a non-exclusive basis, certain of its gene editing intellectual property to exploit certain products for the diagnosis, treatment or prevention of diabetes type 1, diabetes type 2 or insulin dependent / requiring diabetes throughout the world. Subsequently, ViaCyte elected to opt-out of the ViaCyte JDCA. Per the opt-out terms, the on-going collaboration assets are now wholly owned by the Company, subject to a royalty on future sales owed to ViaCyte. The opt-out became effective in early February 2024.

Accounting Analysis

For purposes of this Note 6, the 2015 Collaboration Agreement, Amendment No. 1, Amendment No. 2, A&R Vertex JDCA, and Amendment No. 1 to the A&R Vertex JDCA are collectively referred to as the “Vertex Hemoglobinopathy Agreements” and the Non-Ex License Agreement and ViaCyte JDCA Amendment are collectively referred to as the “March 2023 Diabetes Agreements.”

The Vertex Hemoglobinopathy Agreements and the March 2023 Diabetes Agreements include components of a customer-vendor relationship as defined under ASC 606, Revenue from Contracts with Customers, or ASC 606, collaborative arrangements as defined under ASC 808, Collaborative Agreements, or ASC 808, and research and development costs as defined under ASC 730, Research and Development, or ASC 730. Specifically, with regards to the March 2023 Diabetes Agreements, the Company concluded that the non-exclusive license is a performance obligation under ASC 606 and the ongoing research and development services under the ViaCyte JDCA Amendment are a unit of account under ASC 808.

The Company has determined that recognition criteria for the Letter Agreement has not been met and will not be met until the priority review voucher is (i) utilized or (ii) there is sufficient profitability such that Vertex is obligated to pay the Company under the Letter Agreement.

Accounting Analysis Under ASC 606

Accounting for the Vertex Hemoglobinopathy Agreements

Recognition of Revenue

No revenue was recognized under the Vertex Hemoglobinopathy Agreements for the three and six months ended June 30, 2026 and 2025.

Milestones under the Vertex Hemoglobinopathy Agreements

The Company has evaluated the milestones that may be received in connection with the Vertex Hemoglobinopathy Agreements.

Under the 2015 Collaboration Agreement and subsequent amendments, the Company is eligible to receive up to $410.0 million in additional development, regulatory and commercial milestones and royalties on net product sales for each of the three collaboration targets that Vertex licensed in 2019. Each milestone is payable only once per collaboration target, regardless of the number of products directed to such collaboration target that achieve the relevant milestone event.

The Company has the option to conduct research at its own cost in certain defined areas. If such research is beneficial to the CASGEVY program and CASGEVY ultimately achieves regulatory approval in such areas, the Company could be entitled to receive from Vertex certain milestone payments aggregating to high eight digits.

Each of the remaining milestones described above are fully constrained as of June 30, 2026. There is uncertainty as to whether the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs.

Accounting Analysis under ASC 808

Vertex Hemoglobinopathy Agreements

In connection with the Vertex Hemoglobinopathy Agreements, the Company identified the following collaborative elements, which are accounted for under ASC 808: (i) development and commercialization services for shared products, including any transition services related to CASGEVY under the A&R Vertex JDCA; (ii) R&D Services for follow-on products; and (iii) committee participation. The related impact of the cost sharing under the Vertex Hemoglobinopathy Agreements is included within collaboration expense, net, in the condensed consolidated statements of operations and comprehensive loss.

During the three and six months ended June 30, 2026, the Company recognized $40.3 million and $86.2 million, respectively, of collaboration expense, net, related to the Vertex Hemoglobinopathy Agreements. Collaboration expense, net, during the three and six months ended June 30, 2026 was net of $3.0 million and $4.2 million, respectively, of reimbursements from Vertex. During the three and six months ended June 30, 2025, the Company recognized $45.2 million and $102.7 million of collaboration expense, net, respectively. Collaboration expense, net, during the three and six months ended June 30, 2025 was net of $0.6 million and $0.7 million of reimbursements from Vertex, respectively.

Additional Accounting Considerations

The Company is eligible to receive potential future payments of up to $775.0 million upon the successful achievement of specified development, regulatory and commercial milestones under a strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of DMD and DM1. The Company is also eligible to receive tiered royalties on future net sales on any products that may result from this collaboration; however, the Company has the option to forego the DM1 milestones and royalties to co-develop and co-commercialize all DM1 products globally.

Each of the remaining milestones under the strategic collaboration and license agreement from 2019 for the development and commercialization of products for the treatment of DMD and DM1 are fully constrained as of June 30, 2026. There is uncertainty that the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs.

As of June 30, 2026, there was $12.3 million of current deferred revenue, which is unchanged from December 31, 2025. The transaction price allocated to the remaining performance obligations was $12.3 million. Subsequent to June 30, 2026, the Company was notified by Vertex that it will not exercise an option granted under an amendment to the 2015 Collaboration Agreement to co-develop and co-commercialize a specified target and, as a result, the Company expects to recognize the related deferred revenue in the third quarter of 2026.

As of June 30, 2026, the Company is eligible to receive potential future milestone payments from Vertex of up to $125.0 million in the aggregate under the Non-Ex License Agreement depending on the achievement of pre-determined research, development and commercial milestones for certain products utilizing the licensed intellectual property. Additionally, the Company is eligible to receive tiered royalties on the sales of certain products in the low to mid-single digits.

Each of the remaining milestones under the Non-Ex License Agreement are fully constrained as of June 30, 2026. There is uncertainty as to whether the events to obtain the research and developmental milestones will be achieved given the nature of clinical development and the stage of the CRISPR/Cas9 technology. The remaining research, development and regulatory milestones will be constrained until it is probable that a significant revenue reversal will not occur. Commercial milestones and royalties relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The commercial milestones and royalties are accounted for under the royalty recognition constraint and will be accounted for as constrained variable consideration. The Company applies the royalty recognition constraint for each commercial milestone and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs.

Agreement with Sirius Therapeutics

In May 2025, the Company entered into a collaboration, option and license agreement, or the Sirius Agreement, with Sirius Therapeutics and certain of its affiliates, or Sirius, pursuant to which, among other things, (1) Sirius and the Company will collaborate on the research, development, manufacture, commercialization and use of certain collaboration products utilizing Sirius’ siRNA technology for targeting Factor XI, including CTX611, collectively, the Sirius Collaboration Products; and (2) Sirius granted to the Company options to exclusively license Sirius siRNA technology to target up to two licensed targets from a list of seven reserved targets for the research, development, manufacture and commercialization of licensed products, collectively the siRNA Licensed Products, in exchange for the potential to receive certain option fees, milestone payments and royalties.

In connection with entering into the Sirius Agreement, the Company made an upfront cash payment to Sirius of $25.0 million and also entered into a share issuance agreement with Sirius, pursuant to which the Company registered and issued to Sirius 1,842,105 common shares, nominal value CHF 0.03 per share, or common shares, equal to approximately $70.0 million based on a price per common share equal to $38.00, or the Sirius Shares.

With respect to Sirius Collaboration Products, the Company and Sirius will share equally all development and commercialization costs. For the first Sirius Collaboration Product successfully developed, the Company will be the lead party responsible for Phase 3 global development and commercialization efforts in the United States and Sirius will be the lead party responsible for Phase 3 development (subject to the global development plan) and commercialization efforts in Greater China. The parties will determine the lead party responsible for commercialization in the rest of the world at a future date. The Company and Sirius will share equally net profits and net losses incurred under the Sirius Agreement with respect to all Sirius Collaboration Products, except in the event that a party opts out of the joint development and commercialization. The Company will pay Sirius certain specified future development and regulatory milestones of up to an aggregate of $87.5 million for the first Sirius Collaboration Products to achieve the applicable milestone events. At the Company’s sole election, such milestone payments may be paid in cash, common shares of the Company, or a combination thereof.

With respect to the siRNA Licensed Products, if the Company elects to exercise its option to a licensed target to research, develop, manufacture and commercialize siRNA Licensed Products, the Company will make a one-time $10.0 million payment per option exercise, each, a Sirius Option Payment, to Sirius. The Sirius Option Payment is payable up to two times. In addition, the Company will pay Sirius certain specified future development, regulatory and sales milestones of up to an aggregate of $300.0 million for the first siRNA Licensed Product relating to each licensed target to achieve the applicable milestone events, as well as tiered royalty payments in the mid-single digits to low double digits range on future sales of a commercialized siRNA Licensed Product. The royalty payments are subject to reduction under certain specified conditions set forth in the Sirius Agreement. In addition, at the Company’s sole election, such milestones may be paid in cash, common shares of the Company, or a combination thereof. The Company is solely responsible for all research, development, manufacturing and global commercialization activities and associated costs for the siRNA Licensed Products, as well as all associated costs related to Sirius activities set forth in any applicable research plan relating thereto.

Accounting for the Sirius Agreement

The Sirius Agreement includes components of collaborative arrangements as defined under ASC 808 and research and development costs as defined under ASC 730.

Specifically, development and commercialization costs for the Sirius Collaboration Products contain collaborative elements accounted for under ASC 808, and the related impact of cost sharing for the Sirius Collaboration Products under the Sirius Agreement is included within research and development expenses in the condensed consolidated statements of operations and comprehensive loss. Costs related to siRNA Licensed Products under the Sirius Agreement are included within research and development expenses in the consolidated statement of operations and comprehensive loss.

Research and development costs under the Sirius Agreement related to the Sirius Collaboration Products were $3.4 million and $5.0 million for the three and six months ended June 30, 2026, respectively, and were net of $0.5 million and $0.7 million in reimbursements from Sirius, respectively. Research and development costs under the Sirius Agreement related to the siRNA Licensed Products were not material for the three and six months ended June 30, 2026. All research and development costs under the Sirius Agreement were not material for the three and six months ended June 30, 2025.