X0609 4 2026-08-14 0001755237 Cyclerion Therapeutics, Inc. CYCN 0001740376 CHICKO RHONDA M. false C/O CYCLERION THERAPEUTICS, INC. 245 FIRST STREET, 18TH FLOOR CAMBRIDGE MA 02142 false true false false Chief Financial Officer false Common Stock, no par value 2026-08-14 4 M false 25000 2.355 A 25018 D Option to Purchase 2.355 2026-08-14 4 M false 25000 0 D 2035-08-06 Common Stock 25000 0 D The Reporting Person was granted an option on August 7, 2025 to purchase up to 25,000 shares of the Corporation's common stock pursuant to the Issuer's 2019 Equity Incentive Plan. These 25,000 shares provided for vesting as follows: (i) 8,750 shares became immediately exercisable, and (ii) the remaining 16,250 shares were to vest ratably in monthly installments commencing August 31, 2025 and ending on February 28, 2028, provided that the Reporting Person remained as a consultant or employee of 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 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 cash payment to the Issuer for the full purchase price. /s/ Rhonda Chicko 2026-08-18