Cyclerion Therapeutics (CYCN) 10-Q 4 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 02, 2022
Cover [Abstract]
Entity Registrant Name	CYCLERION THERAPEUTICS, INC.
Document Type	10-Q
Document Period End Date	Mar. 31, 2022
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		43,448,360
Entity Central Index Key	0001755237
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Entity Tax Identification Number	83-1895370
Entity File Number	001-38787
Entity Incorporation, State or Country Code	MA
Entity Address, Address Line One	245 First Street
Entity Address, Address Line Two	18th Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	857
Local Phone Number	327-8778
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	CYCN
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 41,125	$ 53,961
Accounts receivable	227	100
Prepaid expenses	1,007	928
Other current assets	477	468
Total current assets	42,836	55,457
Property and equipment, net	17	65
Operating lease right-of-use asset	1,356	1,402
Other assets	2,316	2,407
Total assets	46,525	59,331
Current liabilities:
Accounts payable	2,519	1,828
Accrued research and development costs	4,538	6,353
Accrued expenses and other current liabilities	2,434	2,904
Total current liabilities	9,491	11,085
Commitments and contingencies
Stockholders' equity
Common stock, no par value, 400,000,000 shares authorized and 43,310,089 issued and outstanding at September 30,2021 and 400,000,000 shares authorized and 34,047,300 issued and outstanding at December 31, 2020	0	0
Accumulated deficit	(228,054)	(215,076)
Paid-in capital	265,112	263,345
Accumulated other comprehensive loss	(24)	(23)
Total stockholders' equity	37,034	48,246
Total liabilities and stockholders' equity	$ 46,525	$ 59,331

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	43,448,360	43,410,185
Common stock, shares outstanding	43,448,360	43,410,185

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenues:
Revenue from development agreement	$ 225	$ 62
Revenue from grants	486
Total revenues	711	62
Cost and expenses:
Research and development	9,743	8,092
General and administrative	3,952	5,365
Total cost and expenses	13,695	13,457
Loss from operations	(12,984)	(13,395)
Interest and other income (expense), net	6	(4)
Net loss	$ (12,978)	$ (13,399)
Net loss per share:
Basic and diluted net loss per share (in dollars per share)	$ (0.30)	$ (0.39)
Weighted average shares used in calculating:
Basic and diluted net loss per share (in shares)	43,425	34,081
Other comprehensive loss:
Net loss	$ (12,978)	$ (13,399)
Other comprehensive loss:
Foreign currency translation adjustment (loss) gain	(1)	391
Comprehensive loss	$ (12,978)	$ (13,399)

Condensed Consolidated and Comb

Condensed Consolidated and Combined Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common stock	Paid-in capital	Accumulated deficit	Accumulated other comprehensive loss
Beginning balance at Dec. 31, 2020	$ 59,493		$ 222,949	$ (163,429)	$ (27)
Beginning balance (in shares) at Dec. 31, 2020		34,047,300
Net loss	(13,399)			(13,399)
Issuance of common stock upon exercise of stock options, RSUs and employee stock purchase plan	27		27
Issuance of common stock upon exercise of stock options, RSUs and employee stock purchase plan (in shares)		82,625
Share-based compensation expense related to issuance of stock options and RSUs to employees and employee stock purchase plan	1,921		1,921
Foreign currency translation adjustment (loss) gain	391		391
Ending balance at Mar. 31, 2021	48,433		225,288	(176,828)	(27)
Ending balance (in shares) at Mar. 31, 2021		34,129,925
Beginning balance at Dec. 31, 2021	$ 48,246		263,345	(215,076)	(23)
Beginning balance (in shares) at Dec. 31, 2021	43,410,185	43,410,185
Net loss	$ (12,978)			(12,978)
Issuance of common stock upon exercise of stock options, RSUs and employee stock purchase plan (in shares)		38,175
Share-based compensation expense related to issuance of stock options and RSUs to employees and employee stock purchase plan	1,476		1,476
Share‑based compensation expense related to issuance of stock options to non-employees	291		291
Foreign currency translation adjustment (loss) gain	(1)				(1)
Ending balance at Mar. 31, 2022	$ 37,034		$ 265,112	$ (228,054)	$ (24)
Ending balance (in shares) at Mar. 31, 2022	43,448,360	43,448,360

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (12,978)	$ (13,399)
Adjustments to reconcile net loss to net cash (used in) operating activities:
Depreciation and amortization	48	258
Net loss on disposal of property and equipment	0	(12)
Share-based compensation expense	1,767	2,312
Changes in operating assets and liabilities:
Accounts receivable	(127)	0
Related party accounts receivable	0	127
Prepaid expenses	(79)	(396)
Other current assets	(9)	(92)
Operating lease assets	46	1,006
Other assets	91	91
Accounts payable	691	(54)
Related party accounts payable	0	(286)
Accrued research and development costs	(1,815)	199
Operating lease liabilities	0	(774)
Accrued expenses and other current liabilities	(470)	(3,435)
Net cash (used in) operating activities	(12,835)	(14,455)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sale of property and equipment	0	1,462
Net cash provided by (used in) investing activities	0	1,462
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercises of stock options and ESPP	0	27
Net cash provided by financing activities	0	27
Effect of exchange rate changes on cash and cash equivalents	(1)	0
Net decrease in cash, cash equivalents and restricted cash	(12,836)	(12,966)
Cash, cash equivalents and restricted cash, beginning of period	53,961	58,232
Cash, cash equivalents and restricted cash, end of period	41,125	45,266
Supplemental cash flow disclosure:
Cash and cash equivalents	41,125	41,429
Restricted cash	0	3,837
Total cash, cash equivalents and restricted cash	$ 41,125	$ 45,266

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Nature of Operations Cyclerion Therapeutics, Inc. (“Cyclerion”, the “Company” or “we”) is a clinical-stage biopharmaceutical company on a mission to develop treatments that restore cognitive function. Our lead asset, CY6463, is a pioneering, central nervous system ("CNS") penetrant, soluble guanylate cyclase ("sGC") stimulator that is currently in clinical development for Alzheimer’s disease with vascular pathology ("ADv"), cognitive impairment associated with schizophrenia ("CIAS"), and Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like episodes ("MELAS"). sGC stimulators are small molecules that act synergistically with nitric oxide ("NO") as positive allosteric modulators of sGC to boost production of cyclic guanosine monophosphate ("cGMP"). cGMP is a key second messenger that, when produced by sGC, regulates diverse and critical biological functions in the CNS including neuronal function, neuroinflammation, cellular bioenergetics, and vascular function. Cyclerion GmbH, a wholly owned subsidiary, was incorporated in Zug, Switzerland on May 3, 2019. Cyclerion GmbH is an operational entity with one employee who is the Company’s Chief Scientific Officer. The functional currency is the Swiss franc. Cyclerion Securities Corporation, a wholly owned subsidiary, was incorporated in Massachusetts on November 15, 2019, and was granted securities corporation status in Massachusetts for the 2019 tax year. Cyclerion Securities Corporation has no employees. Company Overview The Company’s mission is to develop treatments that restore cognitive function. Its priorities are advancing its ongoing CY6463 clinical programs and next generation compound, CY3018. CNS assets. CY6463 is an orally administered CNS-penetrant sGC stimulator that is being developed as a symptomatic and potentially disease modifying therapy for serious CNS diseases. NO-sGC-cGMP is a fundamental signaling network that is widely used in the nervous system. CY6463 enhances the brain’s natural ability to produce cGMP, an important second messenger in the CNS, by stimulating sGC, a key node in the NO-sGC-cGMP pathway. This pathway is critical to basic CNS functions and deficient NO-sGC-cGMP signaling is believed to play an important role in the pathogenesis of many neurodegenerative diseases. Agents that stimulate sGC to produce cGMP may compensate for deficient NO signaling. On January 13, 2020, we announced positive results from our Phase 1 first-in-human study that provided the foundation for continued development of CY6463. The results from this study indicate that CY6463 was well tolerated. Pharmacokinetic ("PK") data, obtained from both blood and cerebral spinal fluid ("CSF"), support once-daily dosing, with or without food, and demonstrated CY6463 penetration of the blood-brain-barrier with CSF concentrations expected to be pharmacologically active. On October 14, 2020, we announced positive topline results from our CY6463 Phase 1 translational pharmacology study in healthy elderly participants. Treatment with CY6463 for 15-days in this 24-subject study confirmed and extended results seen in the earlier first-in-human Phase 1 study: once daily oral treatment demonstrated blood-brain-barrier penetration with expected CNS exposure and target engagement. Results also showed significant improvements in neurophysiological and objective performance measures as well as in inflammatory biomarkers associated with aging and neurodegenerative diseases. CY6463 was safe and generally well tolerated in this study. Significant effects on cerebral blood flow and markers of bioenergetics were not observed in this study of healthy elderly participants. We believe that these results, together with nonclinical data, support continued development of CY6463 as a potential new medicine for serious CNS diseases. We have initiated exploratory clinical trials with CY6463 in ADv, CIAS, and MELAS. The ADv study is supported in part by a grant from the Alzheimer’s Association’s Part the Cloud-Gates Partnership Grant Program (the "PTC Grant"), which provides Cyclerion with $2 million of funding over two years. Our next generation CNS asset, CY3018, is a differentiated CNS-penetrant sGC stimulator with greater CSF-to-plasma exposure relative to CY6463. CY3018 is intended to expand the potential of sGC stimulation for the treatment of disorders of the CNS. Non-CNS assets. We have other assets that are outside of our current strategic focus. These non-core assets are not being internally developed at this time. Praliciguat is an orally administered, once-daily systemic sGC stimulator. On June 3, 2021, we entered into the License Agreement (as defined below) with Akebia Therapeutics, Inc. ("Akebia") relating to the exclusive worldwide license to Akebia of our rights to the development, manufacture, medical affairs and commercialization of pharmaceutical products containing praliciguat and other related products and forms thereof enumerated in such agreement. Olinciguat is an orally administered, once-daily, vascular sGC stimulator that was evaluated in a Phase 2 study of participants with sickle cell disease. We released topline results from this study in October 2020. Olinciguat is available for licensing to a third party partner. The Separation On April 1, 2019, Ironwood Pharmaceuticals, Inc. ("Ironwood") completed the separation of its sGC business, and certain other assets and liabilities, into a separate, independent publicly traded company by way of a pro-rata distribution of all of the outstanding shares of common stock of Cyclerion Therapeutics, Inc. through a dividend distribution of one share of the Company’s common stock, with no par value per share, for every 10 shares of Ironwood common stock held by Ironwood stockholders as of the close of business on March 19, 2019, the record date for the Distribution (the entire transaction being the “Separation”). As a result of the Separation, the Company became an independent public company and commenced trading under the symbol “CYCN” on the Nasdaq Global Select Market on April 2, 2019. 2020 Equity Private Placement On July 29, 2020, the Company entered into a Common Stock Purchase Agreement (the "2020 Equity Private Placement") for the private placement of 6,062,500 shares of the Company's common stock, for total gross proceeds of approximately $ 24.3 million. The closing of the 2020 Equity Private Placement occurred on July 29, 2020. The Company did not utilize the services of a placement agent or broker and accordingly incurred no material related transaction fees or commissions. 2021 Equity Private Placement On June 3, 2021, the Company entered into a Common Stock Purchase Agreement (the “2021 Equity Private Placement”) for the private placement of 5,735,988 shares of the Company’s common stock, for total gross proceeds of approximately $ 18 million. The closing of the 2021 Equity Private Placement occurred on June 7, 2021. The Company did not utilize the services of a placement agent or broker and accordingly incurred no material related transaction fees or commissions. At-the-Market Offering On July 24, 2020, the Company filed a Registration Statement on Form S-3 (the "Shelf") with the Securities and Exchange Commission (the “SEC”) in relation to the registration of common stock, preferred stock, debt securities, warrants and units of any combination thereof for an aggregate initial offering price not to exceed $ 150.0 million. The Shelf was declared effective as of July 31, 2020. On September 3, 2020, the Company entered into a Sales Agreement (the “Sales Agreement”) with Jefferies LLC (“Jefferies”) with respect to an at-the-market offering (the “ATM Offering”) under the Shelf. Under the ATM Offering, the Company may offer and sell, from time to time at its sole discretion, shares of its common stock, having an aggregate offering price of up to $ 50.0 million through Jefferies as its sales agent. The Company will pay to Jefferies cash commissions of 3.0 percent of the gross proceeds of sales of common stock under the Sales Agreement. The Company has sold 3,353,059 shares of its common stock for net proceeds of $ 12.5 million under the ATM Offering since entering into the Sales Agreement, with no shares of common stock issued or sold under the ATM Offering during the three months ended March 31, 2022. Basis of Presentation The condensed consolidated financial statements and the related disclosures are unaudited and have been prepared in accordance with accounting principles generally accepted in the U.S. Additionally, 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 condensed consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, which was filed with the Securities and Exchange Commission on February 24, 2022. 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 months ended March 31, 2022 and 2021 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 financial statements of the Company and its wholly owned subsidiaries, Cyclerion GmbH, and Cyclerion Securities Corporation. All significant intercompany accounts and transactions have been eliminated in the preparation of the accompanying condensed consolidated financial statements. Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company’s evaluation entails analyzing prospective operating budgets and forecasts for expectations of the Company’s cash needs and comparing those needs to the current cash and cash equivalent balances. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company has experienced negative operating cash flows for all historical periods presented and the Company expects these losses to continue into the foreseeable future as the Company continues the development and clinical testing of its product candidates CY6463, CY3018 and its discovery research programs. Through March 31, 2022, the Company had raised an aggregate of $ 219.8 million (in net proceeds) from equity private placements and the ATM Offering. After considering the Company’s current research and development plans and the timing expectations related to the progress of its programs, and after considering its existing cash and cash equivalents of $ 41.1 million as of March 31, 2022 , the Company did not identify conditions or events that would raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date these financial statements were issued.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The accounting policies of the Company are set forth in Note 2. Summary of Significant Accounting Policies to the consolidated financial statements contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021. Use of Estimates The preparation of consolidated financial statements in accordance with U.S. generally accepted accounting principles ("GAAP") requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the amounts of expenses during the reported periods. On an ongoing basis, the Company’s management evaluates its estimates, judgments, and methodologies. Significant estimates and assumptions in the consolidated financial statements include those related to revenue, impairment of long-lived assets, valuation procedures for right-of-use ("ROU") assets and operating lease liabilities, income taxes, including the valuation allowance for deferred tax assets, research and development expenses, contingencies, share-based compensation and going concern. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ materially from these estimates under different assumptions or conditions. Changes in estimates are reflected in reported results in the period in which they become known. New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by the Company as of the specified effective date. Except as discussed elsewhere in the notes to the consolidated financial statements, the Company did not adopt any new accounting pronouncements during the three months ended March 31, 2022 that had a material effect on its condensed consolidated financial statements. In June 2016 the FASB issued ASU 2016-13, Financial Instruments-Credit Losses. This standard requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. As a smaller reporting company, ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2022, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2016-13 will have on its financial statements and related disclosures. In May 2021 the FASB issued Accounting Standards Update No. 2021-04, Earnings Per Share ("Topic 260"), Debt-Modifications and Extinguishments ("Subtopic 470-50"), Compensation-Stock Compensation ("Topic 718"), and Derivatives and Hedging-Contracts in Entity’s Own Equity ("Subtopic 815-40"): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options, a consensus of the Emerging Issues Task Force ("EITF") , which amends the FASB Accounting Standards Codification ("ASC" or the “Codification”) to provide explicit guidance, and, thus, reduce diversity in practice, on accounting by issuers for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after the modification or exchange. This amendment provides that for an entity that presents earnings per share ("EPS") in accordance with Topic 260, the effects of a modification or an exchange of a freestanding equity-classified written call option that is recognized as a dividend should be an adjustment to net income (or net loss) in the basic EPS calculation. The amended guidance is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years, and should be applied prospectively to modifications or exchanges occurring on or after the effective date. The Company adopted ASU 2021-04 in the first quarter of 2022, and the adoption of this standard did not have a material impact on the Company's financial position or results of operations. No other accounting standards known by the Company to be applicable to it that have been issued by the FASB or other standard-setting bodies and that do not require adoption until a future date are expected to have a material impact on the Company’s condensed consolidated financial statements upon adoption.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	. Fair Value of Financial Instruments The Company’s cash equivalents are generally classified within Level 1 of the fair value hierarchy. The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values as of March 31, 2022 and December 31, 2021 (in thousands): Fair Value Measurements as of March 31, 2022: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 40,072 $ — $ — $ 40,072 Cash equivalents $ 40,072 $ — $ — $ 40,072 Fair Value Measurements as of December 31, 2021: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 52,917 $ — $ — $ 52,917 Cash equivalents $ 52,917 $ — $ — $ 52,917 During the three months ended March 31, 2022 and 2021, there were no transfers between levels. The fair value of the Company’s cash equivalents, consisting of money market funds, is based on quoted market prices in active markets with no valuation adjustment. The Company believes the carrying amounts of its prepaid expenses and other current assets, restricted cash, accounts payable, and accrued expenses approximate their fair value due to the short-term nature of these amounts.

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment, net consisted of the following (in thousands): March 31, December 31, 2022 2021 Software 2,214 $ 2,214 Computer equipment 51 51 Property and equipment, gross 2,265 2,265 Less: accumulated depreciation and amortization ( 2,248 ) ( 2,200 ) Property and equipment, net $ 17 $ 65 As of March 31, 2022, and December 31, 2021, the Company’s property and equipment was primarily located in Cambridge, Massachusetts. Depreciation and amortization expense of the Company’s property and equipment was a de minimis amount and approximately $ 0.3 million for the three months ended March 31, 2022 and 2021 , respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2022
Accrued Liabilities and Other Liabilities [Abstract]
Accrued Expenses and Other Current Liabilities	5. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, 2022 2021 Accrued incentive compensation $ 520 $ 1,369 Salaries 455 266 Accrued vacation 363 345 Professional fees 710 398 Accrued severance and benefit costs — 28 Other 386 498 Accrued expenses and other current liabilities $ 2,434 $ 2,904

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	. Commitments and Contingencies Other Funding Commitments In the normal course of business, the Company enters into contracts with clinical research organizations and other third parties for clinical and preclinical research studies and other services and products for operating purposes. These contracts are generally cancellable, with notice, at the Company’s option and do not have any significant cancellation penalties. Guarantees On September 6, 2018, Cyclerion was incorporated in Massachusetts and its officers and directors are indemnified for certain events or occurrences while they are serving in such capacity. The Company enters into certain agreements with other parties in the ordinary course of business that contain indemnification provisions. These typically include agreements with directors and officers, business partners, contractors, clinical sites and customers. Under these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of the Company’s activities. These indemnification provisions generally survive termination of the underlying agreements. The maximum potential amount of future payments the Company could be required to make under these indemnification provisions is unlimited. However, to date the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these obligations is minimal. Accordingly, the Company did not have any liabilities recorded for these obligations as of March 31, 2022 and December 31, 2021 .

Leases

Leases	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Leases	7. Leases On April 30, 2021, the Company entered into a Termination Agreement (the "Termination Agreement") for its Head Lease (the "Head Lease") for the Company's former headquarters located at 301 Binney Street, Cambridge, MA, as initially amended on February 28, 2020, and further amended on September 15, 2020. Pursuant to the Termination Agreement, the Company surrendered the leased space of approximately 57,000 square feet to the building’s landlord. The Company did not pay any termination fees in connection with the Termination Agreement. As a result of the termination of the Head Lease, the related right-of-use asset was written off, the lease liability was derecognized, and the $ 3.8 million security deposit was returned to the Company and recorded as part of our cash balance. Lease cost was recognized on a straight-line basis over the lease term. For the three months ended March 31, 2021, the Company recognized a total of approximately $ 1.6 million of total lease costs and $ 0.5 million of variable lease costs, related to the Head Lease. The Company did no t record any lease costs related to the Head Lease during the three months ended March 31, 2022. For the three months ended March 31, 2021, the Company paid $ 1.4 million related to its lease liability. In May 2021, the Company signed a membership agreement to lease space with WeWork at 501 Boylston Street, Boston, Massachusetts. The lease commenced on August 1, 2021 and was accounted for as a short term lease. The Company recorded $0.1 million lease expense associated with the membership agreement during the three months ended March 31, 2022. On September 15, 2020, the Company entered into a Sublease Termination Agreement (the "Sublease Termination Agreement") to terminate its sublease of 15,700 rentable square feet of its leased premises under the Head Lease. Under the terms of the Sublease Termination Agreement, the subtenant was relieved of its obligation to provide future cash rental payments to the Company. The agreements requiring the former subtenant to provide licensed rooms and services to the Company free of charge through the original sublease term survived the sublease termination. The Company gained access to the licensed rooms and services beginning in the third quarter of 2021. The letter of credit security deposit related to the sublease was released. The Company determined that the Sublease Termination Agreement constituted a non-monetary exchange under ASC 845 Nonmonetary Transactions ("ASC 845") where, in return for the free rooms and the services, the Company agreed to terminate its rights and obligations under the sublease agreement. In accordance with ASC 845, the Company determined that the accounting for the transaction should be based on the fair value of assets or services involved. The Company estimated the fair value of the rooms and services to be approximately $ 1.5 million and $ 2.9 million, respectively. The Company determined that the licensed rooms represent a lease under ASC Topic 842, Leases. The Company obtained control of the rooms in the third quarter of 2021 and the prepaid rooms balance of approximately $ 1.4 million was reclassified from other assets to a ROU asset. The related lease expense is recognized on a straight-line basis over the lease term of 8.88 years. The Company recorded a de minimis amount of lease expense during the three months ended March 31, 2022. The Company determined that the licensed services represent a non-lease component, which is recognized separately from the lease component for this asset class. The expense related to the licensed services is recognized on a straight-line basis over the period the services are received. The Company recorded $ 0.1 million for the three months ended March 31, 2022 . Both the lease expense and services expense are recognized as a component of research and development costs in the condensed consolidated statements of operations and comprehensive loss.

Share-based Compensation Plans

Share-based Compensation Plans	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Share-based Compensation Plans	8. Share-based Compensation Plans In 2019, Cyclerion adopted share-based compensation plans. Specifically, Cyclerion adopted the 2019 Employee Stock Purchase Plan (“2019 ESPP”) and the 2019 Equity Incentive Plan (“2019 Equity Plan”). Under the 2019 ESPP, eligible employees may use payroll deductions to purchase shares of stock in offerings under the plan, and thereby acquire an interest in the future of the Company. The 2019 Equity Plan provides for stock options and restricted stock units (“RSUs”). Cyclerion also mirrored two of Ironwood’s existing plans, the Amended and Restated 2005 Stock Incentive Plan (“2005 Equity Plan”) and the Amended and Restated 2010 Employee, Director and Consultant Equity Incentive Plan (“2010 Equity Plan"). These mirror plans were adopted to facilitate the exchange of Ironwood equity awards for Cyclerion equity awards upon the Separation as part of the equity conversion. As a result of the Separation and in accordance with the EMA, employees of both companies retained their existing Ironwood vested options and received a pro-rata share of Cyclerion options, regardless of which company employed them post-Separation. For employees that were ultimately employed by Cyclerion, unvested Ironwood options and RSUs were converted to unvested Cyclerion options and RSUs. The following table provides share-based compensation reflected in the Company’s condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2022 and 2021 (in thousands): Three Months Ended 2022 2021 Research and development $ 830 $ 982 General and administrative 937 1,330 $ 1,767 $ 2,312 A summary of stock option activity for the three months ended March 31, 2022, is as follows: Weighted Weighted Average Average Average Remaining Intrinsic Number Exercise Contractual Value (in of Options Price Term (Years) thousands) Outstanding as of December 31, 2021 7,080,426 $ 10.73 6.9 — Granted 1,437,950 1.25 Exercised — 0.00 Cancelled or forfeited ( 247,978 ) ( 13.30 ) Outstanding as of March 31, 2022 8,270,398 $ 9.01 7.4 $ 0 Exercisable at March 31, 2022 4,618,482 $ 13.05 6.1 $ 0 As of March 31, 2022, the unrecognized share-based compensation expense, net of estimated forfeitures, related to all unvested time-based stock options held by the Company’s employees is $ 7.9 million and the weighted average period over which that expense is expected to be recognized is 3.4 years. A summary of RSU activity for the three months ended March 31, 2022 is as follows: Weighted Average Number Grant Date of Shares Fair Value Unvested as of December 31, 2021 92,804 $ 13.70 Granted — — Vested ( 38,175 ) 15.01 Forfeited — — Unvested as of March 31, 2022 54,629 $ 12.78 As of March 31, 2022, the unrecognized share-based compensation expense, net of estimated forfeitures, related to all unvested restricted stock units by the Company’s employees is $ 0.5 million and the weighted-average period over which that expense is expected to be recognized is 1.1 years. The Company has granted to certain employees performance-based options to purchase shares of common stock. These options are subject to performance-based milestone vesting. During the three months ended March 31, 2022 and 2021 there were no shares that vested as a result of performance milestone achievements. The Company recorded no share-based compensation expense related to these performance-based options for the three months ended March 31, 2022 and 2021. The Company also has granted to certain employees stock options containing market conditions that vest upon the achievement of specified price targets of the Company’s share price for a period through December 31, 2024. Vesting is measured based upon the average closing price of the Company’s share price for any thirty consecutive trading days, subject to certain service requirements. Stock compensation cost is expensed on a straight-line basis over the derived service period for each stock price target within the award, ranging from approximately 4.0 to 4.6 years. The Company accelerates expense when a stock price target is achieved prior to the derived service period. As of March 31, 2022, there were 450,000 outstanding stock options containing market conditions with a weighted average exercise price of $ 2.01 . As of March 31, 2022 there was $ 0.2 million of unrecognized compensation costs related to stock options containing market conditions, which is expected to be recognized over a weighted-average period of 1.93 years.

Loss per share

Loss per share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Loss per share	9. Loss per share Basic and diluted net loss per common share is computed by dividing net loss by the weighted average number of common shares outstanding during the period as follows: Three Months Ended 2022 2021 Numerator: Net loss (in thousands) $ ( 12,978 ) $ ( 13,399 ) Denominator: Weighted average shares used in calculating net loss per share — basic and diluted (in thousands) 43,425 34,081 Net loss per share — basic and diluted $ ( 0.30 ) $ ( 0.39 ) We exclude shares of common stock related to stock options and RSUs from the calculation of diluted net loss per share since the inclusion of such shares would be anti-dilutive. The following table sets forth potential shares that were considered anti-dilutive for the three months ended March 31, 2022 and 2021: Three Months Ended 2022 2021 Stock Options $ 8,270,398 $ 7,346,250 RSUs 54,629 131,020 $ 8,325,027 $ 7,477,270

Defined Contribution Plan

Defined Contribution Plan	3 Months Ended
	Mar. 31, 2022
Retirement Benefits [Abstract]
Defined Contribution Plan	10. Defined Contribution Plan Subsequent to the Separation, Cyclerion adopted a defined contribution 401(k) Savings Plan similar to the plan in place at Ironwood. The plan assets under the Ironwood defined contribution 401(k) Savings Plan were transferred to the Cyclerion plan. Subject to certain IRS limits, eligible employees may elect to contribute from 1 % to 100 % of their compensation. Cyclerion contributions to the plan are at the sole discretion of the board of directors. Currently, Cyclerion provides a matching contribution of 75 % of the employee’s contributions, up to $ 6,000 annually. Included in compensation expense is approximately $ 0.1 million and $ 0.2 million related to the defined contribution 401(k) Savings Plan for the three months ended March 31, 2022 and 2021, respectively.

Workforce Reduction

Workforce Reduction	3 Months Ended
	Mar. 31, 2022
Restructuring and Related Activities [Abstract]
Workforce Reduction	11. Workforce Reduction 2020 Workforce Reduction On November 5, 2020, the Company began a reduction of its current workforce by forty-eight (48) full-time employees to align its resources with its current priorities of focusing on the MELAS study, the planned ADv study and further characterization of CY6463 novel pharmacology. The workforce reduction was completed by the end of the first quarter of 2021. The following table summarizes the accrued liabilities activity recorded in connection with the reduction in workforce for the three months ended March 31, 2022 (in thousands): Amounts Charges Amount Adjustments Amounts 2020 workforce reduction $ 28 $ 0 $ 26 $ 2 $ — Total $ 28 $ — $ 26 $ 2 $ —

License Agreement

License Agreement	3 Months Ended
	Mar. 31, 2022
License Agreement [Abstract]
License Agreements	12. License Agreement Akebia License Agreement On June 3, 2021, the Company and Akebia entered into a License Agreement (the “License Agreement”) relating to the exclusive worldwide license by the Company to Akebia of our rights to the development, manufacture, medical affairs and commercialization of pharmaceutical products containing the pharmaceutical compound known as praliciguat and other related products and forms thereof enumerated in the License Agreement (collectively, the “Products”). Pursuant to the License Agreement, Akebia will be responsible for all future research, development, regulatory, and commercialization activities for the Products. Akebia paid a $ 3.0 million up-front payment to the Company upon signing of the License Agreement and the Company is eligible to receive additional milestone cash payments of up to $ 12.0 million in the next 18 months. Further milestone cash payments by Akebia are scheduled in the License Agreement based on the initiation of phase 3 clinical trials in the U.S. for Products for first and second indication, for FDA approvals, for approvals in certain other major markets, and for certain sales milestones. In addition to these cash milestone payments, Akebia will pay the Company tiered royalty payments on net sales in certain major markets at percentages ranging from the mid-single digits to the high-teens, subject to certain reductions and offsets. Pursuant to the License Agreement, the Company determined the License Agreement represents a service arrangement under the scope of ASC 606. Given the reversion of the rights under the License Agreement represents a penalty in substance for a termination by Akebia, the contract term would be the stated term of the License Agreement. The Company determined that the grant of license to our patents and trademarks, know how transfer, the assignment of regulatory submissions and trademarks and additional knowledge transfer assistance obligations represent a single promise and performance obligation to be transferred to Akebia over time due to the nature of the promises in the contract. The provision of development materials on hand was identified as a separate performance obligation. However, it is immaterial in the context of the contract as the development materials are low value and do not have an alternative use to the Company. The consideration related to sales-based milestone payments, including royalties, will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license. The Company will re-evaluate the probability of achievement of the milestones and any related constraints each reporting period. Akebia Supply Agreement On August 3, 2021, the Company and Akebia entered into a Supply Agreement (the “Supply Agreement”) relating to the manufacturing by the Company of the Initial Supply of the Drug Product and placebo ("Initial Supply") for Akebia's use pursuant to the License Agreement. Akebia will pay the Company for the manufacturing costs at mutually agreed upon rates. The Company determined the Supply Agreement has stand-alone value under the scope of ASC 606 and should not be combined with the License Agreement. Given that the Supply Agreement can be terminated at any time without cause with 30 days notice, the Company deemed the Supply Agreement to be a month-to-month contract. The manufacturing of the Initial Supply by the Company represents a single performance obligation and consideration related to the manufacturing costs will be recognized over time as costs are incurred, based on an input method. The Company recorded $ 0.2 million as revenue from the Supply Agreement in the three months ended March 31, 2022 .

Grant Revenue

Grant Revenue	3 Months Ended
	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Grant Revenue	13. Grant Revenue In August 2021, the Company was approved to receive funding from the PTC Grant for the Phase 2 study of CNS sGC stimulation in AD with vascular features. The granting period is July 1, 2021, to December 31, 2022, and the Company will receive an award of up to $ 2 million. The Company determined that this transaction is non-reciprocal as there is not considered to be a commensurate value exchanged with the Alzheimer's Association as the funding provider. Where commensurate value is not exchanged for goods and services provided, a recipient assesses whether the grant is conditional or unconditional. The Company considered all conditions and barriers associated with this grant and determined the grant is conditional and revenue will be recognized upon achieving certain milestones and incurring internal costs specifically covered by this grant. Under ASC 958-605, revenues will be recognized as the Company incurs expenses related to the PTC Grant. The Company incurred approximately $ 0.5 million of allowable expenses and recognized a corresponding amount of grant revenue for the three months ended March 31, 2022. The Company had a deferred revenue balance of approximately $ 0.3 million related to advance billings as of March 31, 2022 .

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events The Company has evaluated all events and transactions that occurred after the balance sheet date through the date the condensed consolidated financial statements were issued and determined that there were no such events requiring recognition or disclosure in the condensed consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements and the related disclosures are unaudited and have been prepared in accordance with accounting principles generally accepted in the U.S. Additionally, 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 condensed consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021, which was filed with the Securities and Exchange Commission on February 24, 2022. 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 months ended March 31, 2022 and 2021 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 financial statements of the Company and its wholly owned subsidiaries, Cyclerion GmbH, and Cyclerion Securities Corporation. All significant intercompany accounts and transactions have been eliminated in the preparation of the accompanying condensed consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with U.S. generally accepted accounting principles ("GAAP") requires the Company’s management to make estimates and judgments that may affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the amounts of expenses during the reported periods. On an ongoing basis, the Company’s management evaluates its estimates, judgments, and methodologies. Significant estimates and assumptions in the consolidated financial statements include those related to revenue, impairment of long-lived assets, valuation procedures for right-of-use ("ROU") assets and operating lease liabilities, income taxes, including the valuation allowance for deferred tax assets, research and development expenses, contingencies, share-based compensation and going concern. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ materially from these estimates under different assumptions or conditions. Changes in estimates are reflected in reported results in the period in which they become known.
New Accounting Pronouncements	New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies that are adopted by the Company as of the specified effective date. Except as discussed elsewhere in the notes to the consolidated financial statements, the Company did not adopt any new accounting pronouncements during the three months ended March 31, 2022 that had a material effect on its condensed consolidated financial statements. In June 2016 the FASB issued ASU 2016-13, Financial Instruments-Credit Losses. This standard requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. As a smaller reporting company, ASU 2016-13 will become effective for the Company for fiscal years beginning after December 15, 2022, and early adoption is permitted. The Company is currently evaluating the impact that ASU 2016-13 will have on its financial statements and related disclosures. In May 2021 the FASB issued Accounting Standards Update No. 2021-04, Earnings Per Share ("Topic 260"), Debt-Modifications and Extinguishments ("Subtopic 470-50"), Compensation-Stock Compensation ("Topic 718"), and Derivatives and Hedging-Contracts in Entity’s Own Equity ("Subtopic 815-40"): Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options, a consensus of the Emerging Issues Task Force ("EITF") , which amends the FASB Accounting Standards Codification ("ASC" or the “Codification”) to provide explicit guidance, and, thus, reduce diversity in practice, on accounting by issuers for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after the modification or exchange. This amendment provides that for an entity that presents earnings per share ("EPS") in accordance with Topic 260, the effects of a modification or an exchange of a freestanding equity-classified written call option that is recognized as a dividend should be an adjustment to net income (or net loss) in the basic EPS calculation. The amended guidance is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years, and should be applied prospectively to modifications or exchanges occurring on or after the effective date. The Company adopted ASU 2021-04 in the first quarter of 2022, and the adoption of this standard did not have a material impact on the Company's financial position or results of operations. No other accounting standards known by the Company to be applicable to it that have been issued by the FASB or other standard-setting bodies and that do not require adoption until a future date are expected to have a material impact on the Company’s condensed consolidated financial statements upon adoption.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Schedule of financial assets measured at fair value on a recurring basis and indicating the level of the fair value hierarchy	The Company’s cash equivalents are generally classified within Level 1 of the fair value hierarchy. The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values as of March 31, 2022 and December 31, 2021 (in thousands): Fair Value Measurements as of March 31, 2022: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 40,072 $ — $ — $ 40,072 Cash equivalents $ 40,072 $ — $ — $ 40,072 Fair Value Measurements as of December 31, 2021: Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 52,917 $ — $ — $ 52,917 Cash equivalents $ 52,917 $ — $ — $ 52,917

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): March 31, December 31, 2022 2021 Software 2,214 $ 2,214 Computer equipment 51 51 Property and equipment, gross 2,265 2,265 Less: accumulated depreciation and amortization ( 2,248 ) ( 2,200 ) Property and equipment, net $ 17 $ 65

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2022
Accrued Liabilities and Other Liabilities [Abstract]
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, 2022 2021 Accrued incentive compensation $ 520 $ 1,369 Salaries 455 266 Accrued vacation 363 345 Professional fees 710 398 Accrued severance and benefit costs — 28 Other 386 498 Accrued expenses and other current liabilities $ 2,434 $ 2,904

Share-based Compensation Plans

Share-based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Schedule of share-based compensation expense	The following table provides share-based compensation reflected in the Company’s condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2022 and 2021 (in thousands): Three Months Ended 2022 2021 Research and development $ 830 $ 982 General and administrative 937 1,330 $ 1,767 $ 2,312
Schedule of stock option activity	A summary of stock option activity for the three months ended March 31, 2022, is as follows: Weighted Weighted Average Average Average Remaining Intrinsic Number Exercise Contractual Value (in of Options Price Term (Years) thousands) Outstanding as of December 31, 2021 7,080,426 $ 10.73 6.9 — Granted 1,437,950 1.25 Exercised — 0.00 Cancelled or forfeited ( 247,978 ) ( 13.30 ) Outstanding as of March 31, 2022 8,270,398 $ 9.01 7.4 $ 0 Exercisable at March 31, 2022 4,618,482 $ 13.05 6.1 $ 0
Summary of RSU activity	A summary of RSU activity for the three months ended March 31, 2022 is as follows: Weighted Average Number Grant Date of Shares Fair Value Unvested as of December 31, 2021 92,804 $ 13.70 Granted — — Vested ( 38,175 ) 15.01 Forfeited — — Unvested as of March 31, 2022 54,629 $ 12.78

Loss per share (Tables)

Loss per share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Schedule of basic and diluted earnings per share	Basic and diluted net loss per common share is computed by dividing net loss by the weighted average number of common shares outstanding during the period as follows: Three Months Ended 2022 2021 Numerator: Net loss (in thousands) $ ( 12,978 ) $ ( 13,399 ) Denominator: Weighted average shares used in calculating net loss per share — basic and diluted (in thousands) 43,425 34,081 Net loss per share — basic and diluted $ ( 0.30 ) $ ( 0.39 )
Schedule Of Earnings Per Share Diluted By Common Class	The following table sets forth potential shares that were considered anti-dilutive for the three months ended March 31, 2022 and 2021: Three Months Ended 2022 2021 Stock Options $ 8,270,398 $ 7,346,250 RSUs 54,629 131,020 $ 8,325,027 $ 7,477,270

Workforce Reduction (Tables)

Workforce Reduction (Tables)	3 Months Ended
	Mar. 31, 2022
Restructuring and Related Activities [Abstract]
Schedule of accrued liabilities activity allocated to Cyclerion in connection with the reduction in workforce	The following table summarizes the accrued liabilities activity recorded in connection with the reduction in workforce for the three months ended March 31, 2022 (in thousands): Amounts Charges Amount Adjustments Amounts 2020 workforce reduction $ 28 $ 0 $ 26 $ 2 $ — Total $ 28 $ — $ 26 $ 2 $ —

Nature of Business (Details)

Nature of Business (Details)	Jun. 03, 2021USD ($)shares	Sep. 03, 2020USD ($)	Jul. 29, 2020USD ($)shares	Apr. 01, 2019	Mar. 31, 2022USD ($)shares	Jul. 24, 2020USD ($)	Nov. 15, 2019Employee	May 03, 2019Employee
Nature of Business
Health care trust fund, Description					We have initiated exploratory clinical trials with CY6463 in ADv, CIAS, and MELAS. The ADv study is supported in part by a grant from the Alzheimer’s Association’s Part the Cloud-Gates Partnership Grant Program (the "PTC Grant"), which provides Cyclerion with $2 million of funding over two years.
Common stock dividend issued (shares of Cyclerion per ten shares of Ironwood)				0.1
Common stock issued or sold under the ATM Offering					$ 0
Cash Equivalents, at Carrying Value					41,100,000
Private Placement
Nature of Business
Issuance of common stock equity private placement and ATM (in shares) | shares	5,735,988		6,062,500
Proceeds from June 2021 equity private placement and ATM	$ 18,000,000		$ 24,300,000
Proceeds from 2020 Equity private placement and ATM	$ 18,000,000		$ 24,300,000
Net proceeds from issuance of shares to accredited investors					$ 219,800,000
IPO
Nature of Business
Maximum amount of Aggregate initial offering price						$ 150,000,000
ATM Offering | Jefferies LLC
Nature of Business
Number of common stock sold | shares					3,353,059
Cash commission of gross proceeds of sales of common stock, percentage		3.00%
Net Proceeds from Issuance of Common Stock					$ 12,500,000
ATM Offering | Maximum | Jefferies LLC
Nature of Business
Issuance of common stock equity private placement and ATM		$ 50,000,000
Cyclerion GmbH
Nature of Business
Number of employees | Employee								1
Cyclerion Securities Corporation
Nature of Business
Number of employees | Employee							0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Cash equivalents:
Total cash equivalents	$ 40,072	$ 52,917
Level 1
Cash equivalents:
Total cash equivalents	40,072	52,917
Money market funds
Cash equivalents:
Total cash equivalents	40,072	52,917
Money market funds | Level 1
Cash equivalents:
Total cash equivalents	$ 40,072	$ 52,917

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Property and Equipment
Property and equipment. gross	$ 2,265	$ 2,265
Less: accumulated depreciation and amortization	(2,248)	(2,200)
Property and equipment, net	17	65	$ 65
Depreciation and amortization	48	258
Net loss on disposal of property and equipment	0	12
Property and Equipment [Member]
Property and Equipment
Depreciation and amortization	300	300
Software
Property and Equipment
Property and equipment. gross	2,214	2,214
Computer equipment
Property and Equipment
Property and equipment. gross	$ 51	$ 51

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued Liabilities and Other Liabilities [Abstract]
Accrued incentive compensation		$ 1,369
Salaries		266
Accrued vacation		345
Professional fees		398
Accrued severance and benefit costs		28
Other		498
Accrued expenses and other current liabilities	$ 2,434	$ 2,904

Leases - Summary (Details)

Leases - Summary (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Apr. 30, 2021USD ($)ft²	Sep. 15, 2020ft²
Leases
Term of lease	8 years 10 months 17 days
Rentable space terminated from lease agreement (in square feet) | ft²					15,700
Operating lease right-of-use asset	$ 1,356		$ 1,402
Total lease costs	$ 0	$ 1,600
Second Lease Amendment
Leases
Current portion of operating lease liabilities		1,400
Variable lease costs		$ 500
Termination Agreement
Leases
Surrendered Lease Space | ft²				57,000
Security Deposit Returned				$ 3,800

Leases - Sublease as Lessor (De

Leases - Sublease as Lessor (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Sep. 15, 2020ft²
Sublease as lessor
Rentable space terminated from lease agreement (in square feet) | ft²			15,700
Sublease termination agreement estimated fair value of rooms	$ 1,500
Sublease termination agreement estimated fair value of services	2,900
Other current assets	477	$ 468
Prepaid rooms balance reclassified from other assets	$ 1,400
Term of lease	8 years 10 months 17 days
License And Service
Sublease as lessor
lease expense	$ 100

Share-based Compensation Plan_2

Share-based Compensation Plans (Details)	3 Months Ended
	Mar. 31, 2022USD ($)TradingDay$ / sharesshares	Mar. 31, 2021USD ($)shares	Dec. 31, 2021$ / sharesshares
Share-based Compensation Plans
Share-based compensation	$ 1,767,000	$ 2,312,000
Expected period to recognize the expense	1 year 11 months 4 days
Number of shares vested | shares	0	0
Unrecognized share-based compensation expense | $	$ 200,000
outstanding stock options | shares	450,000
weighted average exercise price | $ / shares	$ 2.01
Restricted Stock Units
Share-based Compensation Plans
Unrecognized share-based compensation expense	$ 500,000
Expected period to recognize the expense	1 year 1 month 6 days
Stock options
Share-based Compensation Plans
Share-based compensation	$ 0	$ 0
Unrecognized share-based compensation expense	$ 7,900,000
Expected period to recognize the expense	3 years 4 months 24 days
Stock options forfeited | shares	247,978
Cancelled or forfeited (in dollars per share) | $ / shares	$ 13.30
outstanding stock options | shares	8,270,398		7,080,426
weighted average exercise price | $ / shares	$ 9.01		$ 10.73
Performance stock options
Share-based Compensation Plans
Threshold consecutive trading days, used as a base for measurement of vesting of stock awards | TradingDay	30
Performance stock options | Minimum [Member]
Share-based Compensation Plans
Expected option term (in years)	4 years
Performance stock options | Maximum
Share-based Compensation Plans
Expected option term (in years)	4 years 7 months 6 days

Share-based Compensation Plan_3

Share-based Compensation Plans - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 1,767	$ 2,312
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	830	982
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 937	$ 1,330

Share-based Compensation Plan_4

Share-based Compensation Plans - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Options
Outstanding at end of the year (in shares)	450,000
Weighted Average Exercise Price
Outstanding at end of the year (in dollars per share)	$ 2.01
Stock options
Number of Options
Outstanding at beginning of the year (in shares)	7,080,426
Granted (in shares)	1,437,950
Exercised (in shares)	0
Cancelled or forfeited (in shares)	(247,978)
Outstanding at end of the year (in shares)	8,270,398	7,080,426
Exercisable (in shares)	4,618,482
Weighted Average Exercise Price
Outstanding at beginning of the year (in dollars per share)	$ 10.73
Granted (in dollars per share)	1.25
Exercised (in dollars per share)	0
Cancelled or forfeited (in dollars per share)	13.30
Outstanding at end of the year (in dollars per share)	9.01	$ 10.73
Exercisable (in dollars per share)	$ 13.05
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	7 years 4 months 24 days	6 years 10 months 24 days
Weighted Average Remaining Contractual Term (years)	6 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding	$ 0	$ 0
Aggregate Intrinsic Value, Exercisable	$ 0

Share-based Compensation Plan_5

Share-based Compensation Plans - Summary of RSU Activity (Details) - Restricted Stock Units - $ / shares	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Number of Shares
Unvested as of December 31, 2021		92,804	54,629
Granted (in shares)	0
Vested (in shares)	(38,175)
Forfeited (in shares)	0
Weighted-Average Grant Date Fair Value
Unvested as of December 31, 2021	$ 12.78	$ 13.70
Granted (in dollars per share)	0
Vested (in dollars per share)	15.01
Forfeited (in dollars per share)	0
Unvested restricted common stock at the end of the period (in dollars per share)	$ 12.78

Loss per share (Details)

Loss per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net loss	$ (12,978)	$ (13,399)
Denominator:
Weighted average shares used in calculating net loss per share — basic and diluted (in thousands)	43,425	34,081
Net loss per share — basic and diluted	$ (0.30)	$ (0.39)

Defined Contribution Plan (Deta

Defined Contribution Plan (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Contribution Plan
401 (k) Savings Plan	us-gaap:QualifiedPlanMember
Matching contribution (as a percent of employee's contributions)	75.00%
Maximum amount of employer matching contribution	$ 6,000
Compensation expense related to the defined contribution 401(k) Savings Plan	$ 100,000	$ 200,000
Minimum
Defined Contribution Plan
Percent of compensation eligible employees may elect to contribute	1.00%
Maximum
Defined Contribution Plan
Percent of compensation eligible employees may elect to contribute	100.00%

Workforce Reduction (Details)

Workforce Reduction (Details) $ in Thousands	Nov. 05, 2020Employees	Mar. 31, 2022USD ($)
2020 Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Beginning of period		$ 28
Charges		0
Amount paid		26
Adjustments		2
End of period		$ 0
Current workforce reductions | November 2020 Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Reduction in workforce, number of employees | Employees	48

License Agreement - Additional

License Agreement - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 03, 2021	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 711	$ 62
Akebia Research License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up Front Payment Received	$ 3,000
Revenues		$ 200
Akebia Research License Agreement [Member] | Forecast [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional milestone cash payment				$ 12,000

Grant Revenue (Additional Infor

Grant Revenue (Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended	18 Months Ended
	Mar. 31, 2022	Dec. 31, 2022
Revenue Recognition and Deferred Revenue [Abstract]
PTC Grant Award		$ 2
Allowable Expenses on Grant Revenue	$ 0.5
Deferred Revenue	$ 0.3