Comparable stake leader
Fairmount Funds Management LLC
SEC ownership of Cyclerion Therapeutics, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001755237.
Disclosed value leader
Fairmount Funds Management LLC
Comparable rows
30/50
Latest evidence
09 Sep 2026
- Public ticker
- CYCN on Nasdaq
- Parsed ownership sources
-
3/4/5, 13D/G, and 13F
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
Fairmount Funds Management LLC
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
30 of 50
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
Fairmount Funds Management LLC
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
09 Sep 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0001755237
- Issuer location
- Cambridge, MA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of Cyclerion Therapeutics, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
Fairmount Funds Managemen...
Disclosed value leader
Fairmount Funds Managemen...
Comparable rows
30/50
Latest evidence
09 Sep 2026
3/4/5
13D/G
13F
Lead comparable stake: 20%
20 rows are not safely comparable across share classes.
13D/G row: Fairmount Funds Management LLC
Showing 1-8 of 50 holder rows.
Quick read
Fairmount Funds Management LLC leads the comparable SEC ownership view at 20%.
30 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens Fairmount Funds Management LLC's linked filing trail.
Comparable ownership
Top 5
Fairmount Funds Management LLC
20%
Peter M. Hecht
19%
FMR LLC
15%
Venrock Healthcare Capital Partne...
9.9%
BALYASNY ASSET MANAGEMENT L.P.
7.3%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Fairmount Funds Management LLC |
3/4/5
13D/G
Director, 10%+ Owner · Tomas Kiselak
|
20%
from 13D/G
|
$30,861,640
9,152,174 shares
mixed-class rows
|
— | 09 Sep 2026 |
| Peter M. Hecht |
3/4/5
13D/G
Director, 10%+ Owner
|
19%
from 13D/G
|
$3,086,022
910,336 shares
mixed-class rows
|
— | 16 Jul 2026 |
| FMR LLC |
13F
13D/G
Company
|
15%
from 13D/G
|
$2,201,963
649,547 shares
|
— | 30 Jun 2026 |
| Venrock Healthcare Capital Partners III, L.P. |
13D/G
|
9.9%
|
—
4,552,277 shares
|
$0 | 08 Sep 2026 |
| BALYASNY ASSET MANAGEMENT L.P. |
13D/G
13F
Company
|
7.3%
|
$1,247,818
317,511 shares
|
$0 | 30 Jun 2026 |
| ADAR1 Capital Management, LLC |
13D/G
13F
Company
|
7%
|
$1,174,115
298,757 shares
|
$0 | 30 Jun 2026 |
| GENERAL ATLANTIC, L.P. |
13D/G
|
6.8%
|
—
3,201,131 shares
|
$0 | 08 Sep 2026 |
| Wellington Biomedical Innovation Master Investors (Cayman) II L.P. |
13D/G
|
6.1%
|
—
2,775,788 shares
|
$0 | 09 Sep 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 23 Sep 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-20 of 30 reporting-owner rows connected to Cyclerion Therapeutics, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
30
Largest Forms 3/4/5 holder
Tomas Kiselak
Net 12M change
$0
Latest report
09 Sep 2026
Recent insider transactions for Cyclerion Therapeutics, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Michelle Patricia Pernice | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | Direct | |||
| Fairmount Funds Management LLC | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | By: Tomas Kiselak | |||
| Fairmount Funds Management LLC | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | By: Tomas Kiselak | |||
| Fairmount Funds Management LLC | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | By: Tomas Kiselak | |||
| Fairmount Funds Management LLC | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | By: Tomas Kiselak | |||
| Fairmount Funds Management LLC | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | By: Tomas Kiselak | |||
| Nimish P. Shah | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | Direct | |||
| Andrew Gottesdiener | CYCN | Stock Option (Right to Buy) | Award | 48,445 | 48,445 | 09 Sep 2026 | Direct | |||
| Rhonda M. Chicko | CYCN | Common Stock, no par value | Options Exercise | 138888.9% | 25,000 | 25,018 | 14 Aug 2026 | Direct | ||
| Rhonda M. Chicko | CYCN | Option to Purchase | Options Exercise | -100% | -25,000 | 0 | 14 Aug 2026 | Direct | ||
| Regina Margaret Graul | CYCN | Common Stock, no par value | Tax liability | -31.1% | -48,629 | 107,523 | 14 Aug 2026 | Direct | ||
| Regina Margaret Graul | CYCN | Common Stock, no par value | Options Exercise | 55.7% | 55,849 | 156,152 | 14 Aug 2026 | Direct | ||
| Regina Margaret Graul | CYCN | Option to Purchase | Options Exercise | -100% | -55,849 | 0 | 14 Aug 2026 | Direct | ||
| Peter M. Hecht | CYCN | Common Stock | Conversion of derivative security | 62.8% | 351,037 | 910,240 | 16 Jul 2026 | Direct | ||
| Peter M. Hecht | CYCN | Series A Convertible Preferred Stock | Conversion of derivative security | -100% | -351,037 | 0 | 16 Jul 2026 | Direct |
* marks a reported price that did not pass the local price check.