Licensing and Commercialization Agreements	12 Months Ended
Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Licensing and Commercialization Agreements	Licensing and Commercialization Agreements ACP License Agreement with Archemix Corp. In September 2011, the Company entered into an amended and restated exclusive license agreement with Archemix Corp. ("Archemix") relating to anti-C5 aptamers (as amended, the "C5 License Agreement"). The C5 License Agreement superseded a July 2007 agreement between the Company and Archemix. Under the C5 License Agreement, the Company holds exclusive worldwide licenses, subject to certain pre–existing rights, under specified patents and technology owned or controlled by Archemix to develop, make, use, sell, offer for sale, distribute for sale, import and export pharmaceutical products comprised of or derived from an anti-C5 aptamer, including ACP, for the prevention, treatment, cure or control of human indications, diseases, disorders or conditions of the eye, adnexa of the eye, orbit and optic nerve, other than certain expressly excluded applications. In connection with the C5 License Agreement, the Company paid Archemix an upfront licensing fee of $1.0 million and issued to Archemix an aggregate of 2,000,000 shares of its series A-1 preferred stock and 500,000 shares of its series B-1 preferred stock. The Company has paid Archemix an aggregate of $9.0 million in fees based on its achievement of specified clinical milestone events under the C5 License Agreement, including two milestone payments of $1.0 million and $6.0 million, respectively, triggered by the positive 12-month data from, and by completion of, the GATHER1 trial, which the Company paid in March 2020 and October 2020, respectively. Under the C5 License Agreement, for each anti-C5 aptamer product that the Company may develop under the agreement, including ACP, it is obligated to make additional payments to Archemix of up to an aggregate of $50.5 million if it achieves specified development, clinical and regulatory milestones, with $24.5 million of such payments relating to a first indication, $23.5 million of such payments relating to second and third indications and $2.5 million of such payments relating to sustained delivery applications. Under the C5 License Agreement, it is also obligated to make additional payments to Archemix of up to an aggregate of $22.5 million if it achieves specified commercial milestones based on net product sales of all anti-C5 products licensed under the agreement. It is also obligated to pay Archemix a double-digit percentage of specified non-royalty payments it may receive from any sublicensee of its rights under the C5 License Agreement. The Company is not obligated to pay Archemix a running royalty based on net product sales in connection with the C5 License Agreement. Unless earlier terminated, the C5 License Agreement will expire upon the latest of 12 years after the first commercial sale in any country of the last licensed product, the expiration of the last-to-expire valid claim of the licensed patents that covers a licensed product, and the date on which no further payments of sublicensing income are to be received by the Company. Either the Company or Archemix may terminate the C5 License Agreement if the other party materially breaches the agreement and the breach remains uncured for a specified period. Archemix may also terminate the C5 License Agreement, or may convert the Company's exclusive license under the agreement to a non-exclusive license, if the Company challenges or assists a third party in challenging the validity or enforceability of any of the patents licensed under the agreement. The Company may terminate the agreement at any time and for any or no reason effective at the end of a specified period following its written notice of termination to Archemix. License Agreement with University of Massachusetts for the miniCEP290 Program In July 2019, the Company entered into the miniCEP290 License Agreement with UMass. Under the miniCEP290 License Agreement, UMass granted it a worldwide, exclusive license under specified patent rights and specified biological materials and a non-exclusive license under specified know-how to make, have made, use, offer to sell, sell, have sold and import products for the treatment of diseases associated with mutations in the CEP290 gene, including LCA10. In July 2019, the Company issued to UMass 75,000 shares of its common stock following execution of the miniCEP290 License Agreement pursuant to an exemption from registration afforded by Section 4(a)(2) of the Securities Act. In September 2019, it paid UMass a $0.4 million upfront license fee, which was recorded as a research and development expense, and it paid UMass accrued patent prosecution expenses of approximately $18 thousand, which was recorded as a general and administrative expense. The Company has also agreed to pay UMass an annual license maintenance fee in the low double-digit thousands of dollars, which will be payable on an annual basis until the expiration of the royalty term for the licensed products. Furthermore, it has agreed to reimburse UMass for the costs and expenses of patent prosecution and maintenance related to the licensed patent rights. The Company has further agreed to pay UMass up to an aggregate of $14.75 million in cash and issue up to 75,000 shares of its common stock if it achieves specified clinical and regulatory milestones with respect to a licensed product. In addition, the Company has agreed to pay UMass up to an aggregate of $48.0 million if it achieves specified commercial sales milestones with respect to a licensed product. The Company is also obligated to pay UMass royalties at a low single-digit percentage of net sales of licensed products. Its obligation to pay royalties under the miniCEP290 License Agreement will continue on a licensed product-by-licensed product and country-by-country basis until the later of: (a) the expiration of the last-to-expire licensed patent rights covering the sale of the applicable licensed product in the country of sale, or (b) 10 years from the first commercial sale of the applicable licensed product in the country of sale. Beginning with the calendar year following receipt of marketing approval for a licensed product, it is also obligated to pay certain minimum royalties, not to exceed an amount in the mid-double-digit thousands of dollars on an annual basis, which minimum royalties are creditable against its royalty obligation with respect to net sales of licensed products due in the year the minimum royalty is paid. If the Company or any of its affiliates sublicenses any of the licensed patent rights or know-how to a third party, it will be obligated to pay UMass a high single-digit to a mid-tens percentage of the consideration received in exchange for such sublicense, with the applicable percentage based upon the stage of development of the licensed products at the time it or the applicable affiliate enters into the sublicense. If the Company receives a rare pediatric disease priority review voucher from the FDA in connection with obtaining marketing approval for a licensed product, and it subsequently uses such priority review voucher in connection with a different product candidate outside the scope of the miniCEP290 License Agreement, it will be obligated to pay UMass a low-tens percentage of the fair market value of the priority review voucher at the time of approval of such product candidate and a low-twenties percentage of the fair market value of the priority review voucher at the time of achievement of a specified commercial sales milestone for such other product candidate. In addition, if it sells such a priority review voucher to a third party, it will be obligated to pay UMass a low-thirties percentage of any consideration received from such third party in connection with such sale. The miniCEP290 License Agreement, unless earlier terminated by the Company or UMass, will expire upon the expiration of its obligation to pay royalties to UMass on net sales of licensed products. The Company may terminate the miniCEP290 License Agreement at any time for any reason upon prior written notice to UMass. It may also terminate the miniCEP290 License Agreement if UMass materially breaches the miniCEP290 License Agreement and does not cure such breach within a specified cure period. UMass may terminate the miniCEP290 License Agreement if the Company materially breaches the miniCEP290 License Agreement and does not cure such breach within a specified cure period. License Agreement with DelSiTech Ltd. On June 30, 2022, the Company entered into a license agreement (the “DelSiTech License Agreement”) with DelSiTech Ltd. (“DelSiTech”). Under the DelSiTech License Agreement, DelSiTech granted the Company a worldwide, exclusive license under specified patent rights and know-how to develop, have developed, make, have made, use, offer to sell, sell, have sold, otherwise commercialize, export and import ACP using DelSiTech’s silica-based sustained release technology for the treatment of diseases of the eye in humans (the “Licensed Product”). The Company may grant sublicenses of the licensed patent rights and know-how without DelSiTech’s consent. The Company paid DelSiTech a €1.25 million upfront license fee, which was recognized as a research and development expense during the three months ended June 30, 2022. Under the DelSiTech License Agreement, the Company is further obligated to pay DelSiTech, up to an aggregate of €35.0 million, if the Company achieves specified clinical and development milestones with respect to the Licensed Product. In addition, the Company is also obligated to pay DelSiTech up to an aggregate of €60.0 million if the Company achieves specified commercial sales milestones with respect to worldwide net sales of the Licensed Product. Due to the uncertainty of the achievement of these milestones, the Company will account for any additional payments if and when such milestones are met. The Company is also obligated to pay DelSiTech royalties at a low single-digit percentage of net sales of the Licensed Product. The royalties payable by the Company are subject to reduction under specified circumstances. The Company’s obligation to pay royalties under the DelSiTech License Agreement will continue on a country-by-country basis until the later of: (a) the expiration of the last-to-expire licensed patent rights covering the Licensed Product in the country of sale, or (b) expiration of all regulatory exclusivity for the Licensed Product in the country of sale. Future milestones and royalties will be recognized in their entirety when achieved. Unless earlier terminated by the Company or DelSiTech, the DelSiTech License Agreement will expire on a country-by-country basis upon the expiration of the Company’s obligation to pay royalties to DelSiTech on net sales of the Licensed Product. Upon expiration of the DelSiTech License Agreement, the licenses granted by DelSiTech to the Company will become fully paid up and irrevocable. The Company may terminate the agreement at any time for any reason upon 60 days’ prior written notice to DelSiTech. Either party may also terminate the DelSiTech License Agreement if the other party materially breaches the DelSiTech License Agreement and does not cure such breach within a specified cure period. Following any termination of the DelSiTech License Agreement prior to expiration of the term of the DelSiTech License Agreement, all rights to the licensed patent rights and know-how that DelSiTech granted to the Company will revert to DelSiTech, subject to the Company’s right to sell off any Licensed Product in the Company’s inventory as of the effectiveness of such termination.

In September 2011, the Company entered into an amended and restated exclusive license agreement with Archemix Corp. ("Archemix") relating to anti-C5 aptamers (as amended, the "C5 License Agreement"). The C5 License Agreement superseded a July 2007 agreement between the Company and Archemix. Under the C5 License Agreement, the Company holds exclusive worldwide licenses, subject to certain pre–existing rights, under specified patents and technology owned or controlled by Archemix to develop, make, use, sell, offer for sale, distribute for sale, import and export pharmaceutical products comprised of or derived from an anti-C5 aptamer, including ACP, for the prevention, treatment, cure or control of human indications, diseases, disorders or conditions of the eye, adnexa of the eye, orbit and optic nerve, other than certain expressly excluded applications.

In connection with the C5 License Agreement, the Company paid Archemix an upfront licensing fee of $1.0 million and issued to Archemix an aggregate of 2,000,000 shares of its series A-1 preferred stock and 500,000 shares of its series B-1 preferred stock. The Company has paid Archemix an aggregate of $9.0 million in fees based on its achievement of specified clinical milestone events under the C5 License Agreement, including two milestone payments of $1.0 million and $6.0 million, respectively, triggered by the positive 12-month data from, and by completion of, the GATHER1 trial, which the Company paid in March 2020 and October 2020, respectively.

Under the C5 License Agreement, for each anti-C5 aptamer product that the Company may develop under the agreement, including ACP, it is obligated to make additional payments to Archemix of up to an aggregate of $50.5 million if it achieves specified development, clinical and regulatory milestones, with $24.5 million of such payments relating to a first indication, $23.5 million of such payments relating to second and third indications and $2.5 million of such payments relating to sustained delivery applications. Under the C5 License Agreement, it is also obligated to make additional payments to Archemix of up to an aggregate of $22.5 million if it achieves specified commercial milestones based on net product sales of all anti-C5 products licensed under the agreement. It is also obligated to pay Archemix a double-digit percentage of specified non-royalty payments it may receive from any sublicensee of its rights under the C5 License Agreement. The Company is not obligated to pay Archemix a running royalty based on net product sales in connection with the C5 License Agreement.

Unless earlier terminated, the C5 License Agreement will expire upon the latest of 12 years after the first commercial sale in any country of the last licensed product, the expiration of the last-to-expire valid claim of the licensed patents that covers a licensed product, and the date on which no further payments of sublicensing income are to be received by the Company.

Either the Company or Archemix may terminate the C5 License Agreement if the other party materially breaches the agreement and the breach remains uncured for a specified period. Archemix may also terminate the C5 License Agreement, or may convert the Company's exclusive license under the agreement to a non-exclusive license, if the Company challenges or assists a third party in challenging the validity or enforceability of any of the patents licensed under the agreement. The Company may terminate the agreement at any time and for any or no reason effective at the end of a specified period following its written notice of termination to Archemix.

In July 2019, the Company entered into the miniCEP290 License Agreement with UMass. Under the miniCEP290 License Agreement, UMass granted it a worldwide, exclusive license under specified patent rights and specified biological materials and a non-exclusive license under specified know-how to make, have made, use, offer to sell, sell, have sold and import products for the treatment of diseases associated with mutations in the CEP290 gene, including LCA10.

In July 2019, the Company issued to UMass 75,000 shares of its common stock following execution of the miniCEP290 License Agreement pursuant to an exemption from registration afforded by Section 4(a)(2) of the Securities Act. In September 2019, it paid UMass a $0.4 million upfront license fee, which was recorded as a research and development expense, and it paid UMass accrued patent prosecution expenses of approximately $18 thousand, which was recorded as a general and administrative expense.

The Company has also agreed to pay UMass an annual license maintenance fee in the low double-digit thousands of dollars, which will be payable on an annual basis until the expiration of the royalty term for the licensed products. Furthermore, it has agreed to reimburse UMass for the costs and expenses of patent prosecution and maintenance related to the licensed patent rights.

The Company has further agreed to pay UMass up to an aggregate of $14.75 million in cash and issue up to 75,000 shares of its common stock if it achieves specified clinical and regulatory milestones with respect to a licensed product. In addition, the Company has agreed to pay UMass up to an aggregate of $48.0 million if it achieves specified commercial sales milestones with respect to a licensed product.

The Company is also obligated to pay UMass royalties at a low single-digit percentage of net sales of licensed products. Its obligation to pay royalties under the miniCEP290 License Agreement will continue on a licensed product-by-licensed product and country-by-country basis until the later of: (a) the expiration of the last-to-expire licensed patent rights covering the sale of the applicable licensed product in the country of sale, or (b) 10 years from the first commercial sale of the applicable licensed product in the country of sale. Beginning with the calendar year following receipt of marketing approval for a licensed product, it is also obligated to pay certain minimum royalties, not to exceed an amount in the mid-double-digit thousands of dollars on an annual basis, which minimum royalties are creditable against its royalty obligation with respect to net sales of licensed products due in the year the minimum royalty is paid.

If the Company or any of its affiliates sublicenses any of the licensed patent rights or know-how to a third party, it will be obligated to pay UMass a high single-digit to a mid-tens percentage of the consideration received in exchange for such sublicense, with the applicable percentage based upon the stage of development of the licensed products at the time it or the applicable affiliate enters into the sublicense.

If the Company receives a rare pediatric disease priority review voucher from the FDA in connection with obtaining marketing approval for a licensed product, and it subsequently uses such priority review voucher in connection with a different product candidate outside the scope of the miniCEP290 License Agreement, it will be obligated to pay UMass a low-tens percentage of the fair market value of the priority review voucher at the time of approval of such product candidate and a low-twenties percentage of the fair market value of the priority review voucher at the time of achievement of a specified commercial

sales milestone for such other product candidate. In addition, if it sells such a priority review voucher to a third party, it will be obligated to pay UMass a low-thirties percentage of any consideration received from such third party in connection with such sale.

The miniCEP290 License Agreement, unless earlier terminated by the Company or UMass, will expire upon the expiration of its obligation to pay royalties to UMass on net sales of licensed products. The Company may terminate the miniCEP290 License Agreement at any time for any reason upon prior written notice to UMass. It may also terminate the miniCEP290 License Agreement if UMass materially breaches the miniCEP290 License Agreement and does not cure such breach within a specified cure period.

On June 30, 2022, the Company entered into a license agreement (the “DelSiTech License Agreement”) with DelSiTech Ltd. (“DelSiTech”). Under the DelSiTech License Agreement, DelSiTech granted the Company a worldwide, exclusive license under specified patent rights and know-how to develop, have developed, make, have made, use, offer to sell, sell, have sold, otherwise commercialize, export and import ACP using DelSiTech’s silica-based sustained release technology for the treatment of diseases of the eye in humans (the “Licensed Product”). The Company may grant sublicenses of the licensed patent rights and know-how without DelSiTech’s consent.

The Company paid DelSiTech a €1.25 million upfront license fee, which was recognized as a research and development expense during the three months ended June 30, 2022. Under the DelSiTech License Agreement, the Company is further obligated to pay DelSiTech, up to an aggregate of €35.0 million, if the Company achieves specified clinical and development milestones with respect to the Licensed Product. In addition, the Company is also obligated to pay DelSiTech up to an aggregate of €60.0 million if the Company achieves specified commercial sales milestones with respect to worldwide net sales of the Licensed Product. Due to the uncertainty of the achievement of these milestones, the Company will account for any additional payments if and when such milestones are met.

The Company is also obligated to pay DelSiTech royalties at a low single-digit percentage of net sales of the Licensed Product. The royalties payable by the Company are subject to reduction under specified circumstances. The Company’s obligation to pay royalties under the DelSiTech License Agreement will continue on a country-by-country basis until the later of: (a) the expiration of the last-to-expire licensed patent rights covering the Licensed Product in the country of sale, or (b) expiration of all regulatory exclusivity for the Licensed Product in the country of sale. Future milestones and royalties will be recognized in their entirety when achieved.

Unless earlier terminated by the Company or DelSiTech, the DelSiTech License Agreement will expire on a country-by-country basis upon the expiration of the Company’s obligation to pay royalties to DelSiTech on net sales of the Licensed Product. Upon expiration of the DelSiTech License Agreement, the licenses granted by DelSiTech to the Company will become fully paid up and irrevocable. The Company may terminate the agreement at any time for any reason upon 60 days’ prior written notice to DelSiTech. Either party may also terminate the DelSiTech License Agreement if the other party materially breaches the DelSiTech License Agreement and does not cure such breach within a specified cure period. Following any termination of the DelSiTech License Agreement prior to expiration of the term of the DelSiTech License Agreement, all rights to the licensed patent rights and know-how that DelSiTech granted to the Company will revert to DelSiTech, subject to the Company’s right to sell off any Licensed Product in the Company’s inventory as of the effectiveness of such termination.