X0609 4 2026-08-14 0001755237 Cyclerion Therapeutics, Inc. CYCN 0002002981 Graul Regina Margaret false C/O CYCLERION THERAPEUTICS, INC. 245 FIRST STREET, 18TH FLOOR CAMBRIDGE MA 02142 true true false false See Remarks false Common Stock, no par value 2026-08-14 4 M false 55849 3.30 A 156152 D Common Stock, no par value 2026-08-14 4 F false 48629 3.79 D 107523 D Option to Purchase 3.30 2026-08-14 4 M false 55849 0 D 2034-08-03 Common Stock 55849 0 D The Reporting Person was granted an option on August 5, 2024 to purchase up to 55,849 shares of the Corporation's common stock pursuant to the 2019 Equity Incentive Plan, vesting ratably in monthly installments over a 48-month period commencing August 31, 2024 and ending July 31, 2028, provided that the Reporting Person remained employed by Cyclerion Therapeutics, Inc. on such applicable vesting date, subject to certain exemptions. On July 17, 2026, the Issuer's Board of Directors elected to accelerate in full the vesting of all then unvested options and all then unvested restricted shares for the Reporting Person. The Reporting Person exercised the option in full on August 14, 2026 and paid for the exercise by means of a cashless exercise, forfeiting options to purchase 48,629 shares as payment to the Issuer for the full exercise price. President and Chief Executive Officer /s/ Regina Margaret Graul 2026-08-18