Nature of the Business and Basis of Presentation	9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Background and Basis of Presentation Korsana Biosciences, Inc. and subsidiaries (“Korsana” or the “Company”), formerly known as Cyclerion Therapeutics, Inc. ("Cyclerion"), is a biotechnology company that is the result of the reverse recapitalization discussed below. Prior to the reverse recapitalization, the private company Korsana Biosciences, Inc. ("Pre-Merger Korsana") was established and incorporated under the laws of the state of Delaware on November 8, 2024. Korsana was founded and launched to research and develop antibody candidates licensed from Paragon Therapeutics, Inc. (“Paragon”), an antibody discovery engine founded by Fairmount Funds Management LLC (“Fairmount”). The Company is based in Waltham, Massachusetts. Korsana was formed to develop therapies built on Therapeutic Targeting (THETATM), a next generation blood-brain barrier (BBB) platform, with an initial focus on neurodegenerative disorders, including its lead product candidate, KRSA-028, an anti-amyloid beta (“Ab”) antibody that combines the proprietary “THETA™” platform with well-validated aspects from other anti-Ab products that have achieved regulatory approval or are in late-stage clinical trials. The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, the ability to complete preclinical and clinical trials, the ability to obtain regulatory approval for product candidates, development by competitors of new technological innovations, dependence on key personnel, the ability to attract and retain qualified employees, reliance on third-party organizations, protection of proprietary technology, compliance with government regulations, product liability, uncertainty of market acceptance of products and the ability to raise additional capital to fund operations. The Company’s potential product candidates will require approval from the U.S. Food and Drug Administration or comparable foreign authorities prior to the commencement of commercial sales. There can be no assurance that the Company’s potential product candidates will receive all the required approvals. In addition, there can be no assurance that the Company’s potential product candidates, if approved, will be accepted in the marketplace, that any future product candidates can be developed or manufactured at an acceptable cost and with appropriate performance characteristics, or that such product candidates will be successfully marketed, if at all. The accompanying unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. Accordingly, these interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Pre-Merger Korsana included in the Registration Statement on Form S-4 (File No. 333-295175) declared effective on July 24, 2026. In the opinion of management, the unaudited interim condensed consolidated financial statements reflect all normal recurring adjustments considered necessary for a fair presentation of the Company’s financial position and the results of its operations for the interim periods presented. The results of operations for the three and nine months ended September 30, 2026 and 2025 are not necessarily indicative of the results that may be expected for the full year or any other subsequent interim period. The condensed consolidated financial statements include the accounts of the Company and its consolidated subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. As the Merger was accounted for as a reverse recapitalization, the historical financial statements prior to September 8, 2026 reflect the operations of Pre-Merger Korsana and its consolidated subsidiary. Reverse Recapitalization and Pre-Closing Financing On September 8, 2026 (the "Closing Date"), the Company consummated the transaction (the "Closing") pursuant to that certain Agreement and Plan of Merger and Reorganization, dated as of April 1, 2026, which agreement was subsequently amended on April 17, 2026 (as amended, the "Merger Agreement"), by and among Pre-Merger Korsana, Cyclerion, Cariboos Merger Sub Corp., a Delaware corporation and wholly owned subsidiary of Cyclerion ("First Merger Sub"), and Cariboos Merger Sub II, LLC, a Delaware limited liability company and wholly owned subsidiary of Cyclerion ("Second Merger Sub"). As part of the Closing, First Merger Sub merged with and into Pre-Merger Korsana, with Pre-Merger Korsana continuing as a wholly owned subsidiary of Cyclerion and the surviving corporation (the “First Merger”). Immediately following the First Merger and as part of the same overall transaction, Pre-Merger Korsana merged with and into Second Merger Sub (the “Second Merger” and, together with the First Merger, the “Merger”), with Second Merger Sub being the surviving entity of the Second Merger. Second Merger Sub changed its name to "Korsana Biosciences Operating Company, LLC" and Cyclerion changed its name to "Korsana Biosciences, Inc." The Company is led by Pre-Merger Korsana's management team and remains focused on developing therapies for neurodegenerative disorders. In accordance with an exchange ratio determined in accordance with the terms of the Merger Agreement (the “Exchange Ratio”), at the effective time of the First Merger (the “First Effective Time”), (i) each then-outstanding share of common stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana common stock") (including shares of Pre-Merger Korsana common stock issued in connection with the Pre-Closing Financing (as defined below)) automatically converted into the right to receive a number of shares of common stock, no par value per share, of Cyclerion (the "Cyclerion common stock") equal to the Exchange Ratio, (ii) each then-outstanding share of Series Seed Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series Seed Preferred Stock") was converted into the right to receive a number of shares of Series B Non-Voting Convertible Preferred Stock, no par value, of Cyclerion (the "Series B Preferred Stock"), equal to the Exchange Ratio divided by 1,000, (iii) each-then-outstanding share of Series A Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series A Preferred Stock") automatically converted into the right to receive to a number of shares of Cyclerion common stock equal to the Exchange Ratio; provided, that to the extent the shares of Cyclerion common stock otherwise issuable to any holder would exceed such holder's beneficial ownership limitation (initially set at a percentage of up to 9.99% of the outstanding Cyclerion common stock), such holder received, in lieu of the excess shares, pre-funded warrants to purchase an equal number of shares of Cyclerion common stock, subject to adjustment as set forth in the form of the pre-funded warrant, (iv) each then-outstanding option to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into an option to purchase shares of Cyclerion common stock, adjusted for the Exchange Ratio, (v) each then-outstanding warrant to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into a warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement, (vi) each then-outstanding share of Pre-Merger Korsana restricted stock was assumed by Cyclerion, subject to adjustment as set forth in the Merger Agreement, and (vii) each then-outstanding pre-funded warrant to purchase shares of Pre-Merger Korsana common stock was converted into a pre-funded warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement and the form of pre-funded warrant. The Exchange Ratio was calculated as 0.2074 shares of Cyclerion common stock for each share of Pre-Merger Korsana common stock (and 0.0002074 shares of Series B Preferred Stock for each share of Pre-Merger Korsana Series Seed Preferred Stock) on the Closing Date, which gives effect to a 1-for-7 reverse stock split of Cyclerion common stock immediately prior to the Merger. The par value per share and the number of authorized shares were not adjusted as a result of the Exchange Ratio. The shares of the Company's common stock underlying outstanding stock options, restricted stock awards, and other equity instruments were proportionately reduced and the respective exercise prices, if applicable, were proportionately increased in accordance with the terms of the agreements governing such securities. All references to common stock, options to purchase common stock, common stock share data, per share data, and related information contained in the condensed consolidated financial statements have been retrospectively adjusted to reflect the effect of the Exchange Ratio for all periods presented, unless otherwise specifically indicated or the context otherwise requires. Immediately prior to the completion of the Merger, and in order to provide Korsana with additional capital for its development programs, Pre-Merger Korsana entered into a securities purchase agreement (the "Securities Purchase Agreement") with certain institutional and accredited investors, pursuant to which Pre-Merger Korsana issued and sold 140,516,578 shares of Pre-Merger Korsana common stock and 20,171,961 pre-funded warrants, exercisable for 20,171,961 shares of Pre-Merger Korsana common stock, at a purchase price of $2.3648 per share and $2.3647 per warrant, in each case before giving effect to the Exchange Ratio, for an aggregate purchase price of $380.0 million in a private placement (the “Pre-Closing Financing”). Entities affiliated with Fairmount and Venrock, both related parties of the Company, participated in the Pre-Closing Financing for aggregate purchase prices of $75.0 million and $60.0 million, respectively (see Note 13). At the Closing of the Merger, based on the exchange ratio, the Pre-Merger Korsana common stock and pre-funded warrants subscribed for were converted into the right to receive 29,143,142 shares of common stock and 4,183,665 pre-funded warrants. Shares of Pre-Merger Korsana common stock and pre-funded warrants to purchase shares of Korsana common stock issued pursuant to the Securities Purchase Agreement were converted into shares of Cyclerion common stock and pre-funded warrants to purchase shares of Cyclerion common stock at Closing per the Merger Agreement. In connection with the Merger, the Company entered into a contingent value rights agreement (the “CVR Agreement”), pursuant to which certain legacy Cyclerion stockholders became entitled to receive contingent payments associated with the potential future monetization of certain legacy Cyclerion assets, including its equity investment in Tisento Therapeutics, Inc. (collectively, the “CVRs”). Payments under the CVRs are contingent upon the realization of proceeds from the underlying assets in accordance with the terms of the CVR Agreement. The Company determined that the CVRs represent a single freestanding derivative liability measured at fair value (see Note 2). The Merger was accounted for as a reverse recapitalization in accordance with U.S. GAAP. Under this method of accounting, Pre-Merger Korsana was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the fact that, immediately following the Merger: (i) Pre-Merger Korsana stockholders own a substantial majority of the voting rights in the combined company; (ii) Pre-Merger Korsana's largest stockholders retain the largest interest in the combined company; (iii) Pre-Merger Korsana designated a majority of the initial members of the board of directors of the combined company; and (iv) Pre-Merger Korsana's executive management team became the management team of the combined company. Accordingly, for accounting purposes: (i) the Merger was treated as the equivalent of Pre-Merger Korsana issuing stock to acquire the net assets of Cyclerion, and (ii) the reported historical operating results of the combined company prior to the Merger are those of Pre-Merger Korsana. Additional information regarding the Merger is included in Note 3. Liquidity and Going Concern Since its inception, the Company has devoted substantially all of its resources to advancing the development of its portfolio of programs, organizing and staffing the Company, business planning, raising capital, and providing general and administrative support for these operations. Current and future programs will require significant research and development efforts, including preclinical and clinical trials, and regulatory approvals to commercialization. Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operating activities through a combination of equity offerings and debt financings. The Company has not generated any revenue from product sales or other sources and has incurred significant operating losses and negative cash flows from operations since inception. The Company expects that its research and development and general and administrative costs will continue to increase significantly, including in connection with conducting future pre-clinical activities and clinical trials and manufacturing for its existing product candidates and any future product candidates to support commercialization and providing general and administrative support for its operations, including the costs associated with operating as a public company. The Company has incurred net losses of $46.4 million and $77.3 million during the three and nine months ended September 30, 2026, respectively. As of September 30, 2026, the Company had an accumulated deficit of $113.0 million. As of September 30, 2026, the Company had $456.2 million in cash and cash equivalents. The Company’s management expects that its existing cash and cash equivalents will be sufficient to fund the Company’s operating plans for at least twelve months from the date these condensed consolidated financial statements are issued.

Background and Basis of Presentation

Korsana Biosciences, Inc. and subsidiaries (“Korsana” or the “Company”), formerly known as Cyclerion Therapeutics, Inc. ("Cyclerion"), is a biotechnology company that is the result of the reverse recapitalization discussed below. Prior to the reverse recapitalization, the private company Korsana Biosciences, Inc. ("Pre-Merger Korsana") was established and incorporated under the laws of the state of Delaware on November 8, 2024. Korsana was founded and launched to research and develop antibody candidates licensed from Paragon Therapeutics, Inc. (“Paragon”), an antibody discovery engine founded by Fairmount Funds Management LLC (“Fairmount”). The Company is based in Waltham, Massachusetts. Korsana was formed to develop therapies built on Therapeutic Targeting (THETATM), a next generation blood-brain barrier (BBB) platform, with an initial focus on neurodegenerative disorders, including its lead product candidate, KRSA-028, an anti-amyloid beta (“Ab”) antibody that combines the proprietary “THETA™” platform with well-validated aspects from other anti-Ab products that have achieved regulatory approval or are in late-stage clinical trials.

The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, the ability to complete preclinical and clinical trials, the ability to obtain regulatory approval for product candidates, development by competitors of new technological innovations, dependence on key personnel, the ability to attract and retain qualified employees, reliance on third-party organizations, protection of proprietary technology, compliance with government regulations, product liability, uncertainty of market acceptance of products and the ability to raise additional capital to fund operations.

The Company’s potential product candidates will require approval from the U.S. Food and Drug Administration or comparable foreign authorities prior to the commencement of commercial sales. There can be no assurance that the Company’s potential product candidates will receive all the required approvals. In addition, there can be no assurance that the Company’s potential product candidates, if approved, will be accepted in the marketplace, that any future product candidates can be developed or manufactured at an acceptable cost and with appropriate performance characteristics, or that such product candidates will be successfully marketed, if at all.

The accompanying unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. Accordingly, these interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto of Pre-Merger Korsana included in the Registration Statement on Form S-4 (File No. 333-295175) declared effective on July 24, 2026. In the opinion of management, the unaudited interim condensed consolidated financial statements reflect all normal recurring adjustments considered necessary for a fair presentation of the Company’s financial position and the results of its operations for the interim periods presented.

The results of operations for the three and nine months ended September 30, 2026 and 2025 are not necessarily indicative of the results that may be expected for the full year or any other subsequent interim period. The condensed consolidated financial statements include the accounts of the Company and its consolidated subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. As the Merger was accounted for as a reverse recapitalization, the historical financial statements prior to September 8, 2026 reflect the operations of Pre-Merger Korsana and its consolidated subsidiary.

On September 8, 2026 (the "Closing Date"), the Company consummated the transaction (the "Closing") pursuant to that certain Agreement and Plan of Merger and Reorganization, dated as of April 1, 2026, which agreement was subsequently amended on April 17, 2026 (as amended, the "Merger Agreement"), by and among Pre-Merger Korsana, Cyclerion, Cariboos Merger Sub Corp., a Delaware corporation and wholly owned subsidiary of Cyclerion ("First Merger Sub"), and Cariboos Merger Sub II, LLC, a Delaware limited liability company and wholly owned subsidiary of Cyclerion ("Second Merger Sub"). As part of the Closing, First Merger Sub merged with and into Pre-Merger Korsana, with Pre-Merger Korsana continuing as a wholly owned subsidiary of Cyclerion and the surviving corporation (the “First Merger”). Immediately following the First Merger and as part of the same overall transaction, Pre-Merger Korsana merged with and into Second Merger Sub (the “Second Merger” and, together with the First Merger, the “Merger”), with Second Merger Sub being the surviving entity of the Second Merger. Second Merger Sub changed its name to "Korsana Biosciences Operating Company, LLC" and Cyclerion changed its name to "Korsana Biosciences, Inc." The Company is led by Pre-Merger Korsana's management team and remains focused on developing therapies for neurodegenerative disorders.

In accordance with an exchange ratio determined in accordance with the terms of the Merger Agreement (the “Exchange Ratio”), at the effective time of the First Merger (the “First Effective Time”), (i) each then-outstanding share of common stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana common stock") (including shares of Pre-Merger Korsana common stock issued in connection with the Pre-Closing Financing (as defined below)) automatically converted into the right to receive a number of shares of common stock, no par value per share, of Cyclerion (the "Cyclerion common stock") equal to the Exchange Ratio, (ii) each then-outstanding share of Series Seed Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series Seed Preferred Stock") was converted into the right to receive a number of shares of Series B Non-Voting Convertible Preferred Stock, no par value, of Cyclerion (the "Series B Preferred Stock"), equal to the Exchange Ratio divided by 1,000, (iii) each-then-outstanding share of Series A Preferred Stock, par value $0.0001 per share, of Pre-Merger Korsana (the "Pre-Merger Korsana Series A Preferred Stock") automatically converted into the right to receive to a number of shares of Cyclerion common stock equal to the Exchange Ratio; provided, that to the extent the shares of Cyclerion common stock otherwise issuable to any holder would exceed such holder's beneficial ownership limitation (initially set at a percentage of up to 9.99% of the outstanding Cyclerion common stock), such holder received, in lieu of the excess shares, pre-funded warrants to purchase an equal number of shares of Cyclerion common stock, subject to adjustment as set forth in the form of the pre-funded warrant, (iv) each then-outstanding option to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into an option to purchase shares of Cyclerion common stock, adjusted for the Exchange Ratio, (v) each then-outstanding warrant to purchase Pre-Merger Korsana common stock was assumed by Cyclerion and was converted into a warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement, (vi) each then-outstanding share of Pre-Merger Korsana restricted stock was assumed by Cyclerion, subject to adjustment as set forth in the Merger Agreement, and (vii) each then-outstanding pre-funded warrant to purchase shares of Pre-Merger Korsana common stock was converted into a pre-funded warrant to purchase shares of Cyclerion common stock, subject to adjustment as set forth in the Merger Agreement and the form of pre-funded warrant.

The Exchange Ratio was calculated as 0.2074 shares of Cyclerion common stock for each share of Pre-Merger Korsana common stock (and 0.0002074 shares of Series B Preferred Stock for each share of Pre-Merger Korsana Series Seed Preferred Stock) on the Closing Date, which gives effect to a 1-for-7 reverse stock split of Cyclerion common stock immediately prior to the Merger. The par value per share and the number of authorized shares were not adjusted as a result of the Exchange Ratio. The shares of the Company's common stock underlying outstanding stock options, restricted stock awards, and other equity instruments were proportionately reduced and the respective exercise prices, if applicable, were proportionately increased in accordance with the terms of the agreements governing such securities. All references to common stock, options to purchase common stock, common stock share data, per share data, and related information contained in the condensed consolidated financial statements have been retrospectively adjusted to reflect the effect of the Exchange Ratio for all periods presented, unless otherwise specifically indicated or the context otherwise requires.

Immediately prior to the completion of the Merger, and in order to provide Korsana with additional capital for its development programs, Pre-Merger Korsana entered into a securities purchase agreement (the "Securities Purchase Agreement") with certain institutional and accredited investors, pursuant to which Pre-Merger Korsana issued and sold 140,516,578 shares of Pre-Merger Korsana common stock and 20,171,961 pre-funded warrants, exercisable for 20,171,961 shares of Pre-Merger Korsana common stock, at a purchase price of $2.3648 per share and $2.3647 per warrant, in each case before giving effect to the Exchange Ratio, for an aggregate purchase price of $380.0 million in a private placement (the “Pre-Closing Financing”). Entities affiliated with Fairmount and Venrock, both related parties of the Company, participated in the Pre-Closing Financing for aggregate purchase prices of $75.0 million and $60.0 million, respectively (see Note 13). At the Closing of the Merger, based on the exchange ratio, the Pre-Merger Korsana common stock and pre-funded warrants subscribed for were converted into the right to receive 29,143,142 shares of common stock and 4,183,665 pre-funded warrants. Shares of Pre-Merger Korsana common stock and pre-funded warrants to purchase shares of Korsana common stock issued pursuant to the Securities Purchase Agreement were converted into shares of Cyclerion common stock and pre-funded warrants to purchase shares of Cyclerion common stock at Closing per the Merger Agreement.

In connection with the Merger, the Company entered into a contingent value rights agreement (the “CVR Agreement”), pursuant to which certain legacy Cyclerion stockholders became entitled to receive contingent payments associated with the potential future monetization of certain legacy Cyclerion assets, including its equity investment in Tisento Therapeutics, Inc. (collectively, the “CVRs”). Payments under the CVRs are contingent upon the realization of proceeds from the underlying assets in accordance with the terms of the CVR Agreement. The Company determined that the CVRs represent a single freestanding derivative liability measured at fair value (see Note 2).

The Merger was accounted for as a reverse recapitalization in accordance with U.S. GAAP. Under this method of accounting, Pre-Merger Korsana was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the fact that, immediately following the Merger: (i) Pre-Merger Korsana stockholders own a substantial majority of the voting rights in the combined company; (ii) Pre-Merger Korsana's largest stockholders retain the largest interest in the combined company; (iii)

Pre-Merger Korsana designated a majority of the initial members of the board of directors of the combined company; and (iv) Pre-Merger Korsana's executive management team became the management team of the combined company. Accordingly, for accounting purposes: (i) the Merger was treated as the equivalent of Pre-Merger Korsana issuing stock to acquire the net assets of Cyclerion, and (ii) the reported historical operating results of the combined company prior to the Merger are those of Pre-Merger Korsana. Additional information regarding the Merger is included in Note 3.

Since its inception, the Company has devoted substantially all of its resources to advancing the development of its portfolio of programs, organizing and staffing the Company, business planning, raising capital, and providing general and administrative support for these operations. Current and future programs will require significant research and development efforts, including preclinical and clinical trials, and regulatory approvals to commercialization. Until such time as the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operating activities through a combination of equity offerings and debt financings.

The Company has not generated any revenue from product sales or other sources and has incurred significant operating losses and negative cash flows from operations since inception. The Company expects that its research and development and general and administrative costs will continue to increase significantly, including in connection with conducting future pre-clinical activities and clinical trials and manufacturing for its existing product candidates and any future product candidates to support commercialization and providing general and administrative support for its operations, including the costs associated with operating as a public company. The Company has incurred net losses of $46.4 million and $77.3 million during the three and nine months ended September 30, 2026, respectively. As of September 30, 2026, the Company had an accumulated deficit of $113.0 million. As of September 30, 2026, the Company had $456.2 million in cash and cash equivalents.

The Company’s management expects that its existing cash and cash equivalents will be sufficient to fund the Company’s operating plans for at least twelve months from the date these condensed consolidated financial statements are issued.