Fairmount fund trims Cogent Biosciences (COGT) stake after 7M-share sale

Rhea-AI Filing Summary

Fairmount Healthcare Fund II LP, an entity associated with Fairmount Funds Management LLC, converted 28,000 shares of Cogent Biosciences Series A Convertible Preferred Stock into 7,000,000 shares of Common Stock for no cash consideration on March 31, 2026. The fund then sold 7,000,000 Common shares in an open-market transaction at $34.66 per share, reducing its indirect Common Stock holdings to 5,503,418 shares. Following the conversion, it continues to hold 39,414 shares of Series A Convertible Preferred Stock, each convertible into 250 Common shares, subject to a 9.9% beneficial ownership cap.

Positive

• None.

Negative

• Fairmount Healthcare Fund II LP sold 7,000,000 shares of Cogent Biosciences Common Stock at $34.66, cutting its indirect common holdings from 12,503,418 to 5,503,418 shares in a single day.

Insights

Equity capital markets analyst

Large fund converts preferred, then sells 7M Cogent common shares.

The filing shows Fairmount Healthcare Fund II LP converting 28,000 Series A Convertible Preferred shares into 7,000,000 Cogent Biosciences common shares at no cash cost, then selling the same 7,000,000 common shares at $34.66 each.

This looks like a full monetize-after-conversion move: common holdings fell from 12,503,418 to 5,503,418 shares, so more than half the fund’s common stake was sold. The fund still retains both common shares and 39,414 preferred shares, but its economic exposure is notably reduced.

The Series A Preferred carries a 9.9% beneficial ownership limit, which constrains how much can be converted at once. Future changes in exposure, if any, would likely appear through additional conversions or sales by the fund reported in later filings.

Insider Trade Summary

Net Seller: 7,000,000 shares ($242,620,000)

Net Sell 3 txns

Insider Fairmount Funds Management LLC

Role Director

Sold 7,000,000 shs ($242.62M)

Type	Security	Shares	Price	Value
Conversion	Series A Convertible Preferred Stock	28,000	$0.00	--
Conversion	Common Stock	7,000,000	$0.00	--
Sale	Common Stock	7,000,000	$34.66	$242.62M

Holdings After Transaction: Series A Convertible Preferred Stock — 39,414 shares (Indirect, Fairmount Healthcare Fund II LP); Common Stock — 12,503,418 shares (Indirect, Fairmount Healthcare Fund II LP)

Footnotes (1)

1. Each share of Series A Convertible Preferred Stock is convertible into shares of Common Stock at any time at the option of the holder thereof, into 250 shares of Common Stock, subject to certain limitations, including that a holder of Series A Preferred Stock is prohibited from converting shares of Series A Preferred Stock into shares of Common Stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than 9.9% of the total number of shares of Common Stock issued and outstanding immediately after giving effect to such conversion. On March 31, 2026, the Reporting Persons converted 28,000 shares of Series A Convertible Preferred Stock into 7,000,000 shares of Common Stock for no cash consideration, in accordance with the Certificate of Designations for the Series A Convertible Preferred Stock. Fairmount Funds Management LLC and Fairmount Healthcare Fund II GP LLC have voting power and investment power over the securities held by Fairmount Healthcare Fund II LP ("Fund II"). They disclaim beneficial ownership of securities held by Fund II for purposes of Rule 16a-1(a)(2), except to the extent of their pecuniary interest therein.

Key Figures

Preferred shares converted: 28,000 shares Common shares acquired on conversion: 7,000,000 shares Common shares sold: 7,000,000 shares +5 more

8 metrics

Preferred shares converted 28,000 shares Series A Convertible Preferred Stock converted on March 31, 2026

Common shares acquired on conversion 7,000,000 shares Common Stock received from preferred conversion

Common shares sold 7,000,000 shares Open-market sale at $34.66 per share

Sale price $34.66 per share Price for Common Stock sale on March 31, 2026

Common shares held after transaction 5,503,418 shares Indirect Common Stock holdings following sale

Preferred shares held after transaction 39,414 shares Remaining Series A Convertible Preferred Stock

Conversion ratio 250 common per preferred share Series A Convertible Preferred to Common Stock

Beneficial ownership cap 9.9% Maximum Common ownership post-conversion for a holder

Key Terms

Series A Convertible Preferred Stock, beneficially own more than 9.9%, Certificate of Designations, Rule 16a-1(a)(2), +2 more

6 terms

Series A Convertible Preferred Stock financial

"Each share of Series A Convertible Preferred Stock is convertible into shares of Common Stock"

Series A convertible preferred stock is a class of shares sold in an early funding round that gives investors a mix of protection and upside: it pays a priority claim over common shares if the company is sold or closes, but can be converted into ordinary shares to share in future growth. Think of it like a hybrid between a safer stake and a ticket to ownership; it matters to investors because it affects who controls the company, how future gains are split, and how much their investment is protected from downside.

beneficially own more than 9.9% regulatory

"prohibited from converting ... if ... would beneficially own more than 9.9% of the total number of shares"

Certificate of Designations regulatory

"for no cash consideration, in accordance with the Certificate of Designations for the Series A Convertible Preferred Stock"

Rule 16a-1(a)(2) regulatory

"They disclaim beneficial ownership of securities held by Fund II for purposes of Rule 16a-1(a)(2)"

derivative security financial

"Conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

open-market sale financial

"Sale in open market or private transaction"

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Fairmount Funds Management LLC

(Last) (First) (Middle)

200 BARR HARBOR DRIVE, SUITE 400

(Street)

WEST CONSHOHOCKEN PENNSYLVANIA 19428

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Cogent Biosciences, Inc. [ COGT ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/31/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/31/2026		C		7,000,000	A	(1)	12,503,418	I	Fairmount Healthcare Fund II LP(2)
Common Stock	03/31/2026		S		7,000,000	D	$34.66	5,503,418	I	Fairmount Healthcare Fund II LP(2)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A Convertible Preferred Stock	(1)	03/31/2026		C			28,000	(1)	(1)	Common Stock	7,000,000	$0.00	39,414	I	Fairmount Healthcare Fund II LP(2)

Explanation of Responses:

1. Each share of Series A Convertible Preferred Stock is convertible into shares of Common Stock at any time at the option of the holder thereof, into 250 shares of Common Stock, subject to certain limitations, including that a holder of Series A Preferred Stock is prohibited from converting shares of Series A Preferred Stock into shares of Common Stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than 9.9% of the total number of shares of Common Stock issued and outstanding immediately after giving effect to such conversion. On March 31, 2026, the Reporting Persons converted 28,000 shares of Series A Convertible Preferred Stock into 7,000,000 shares of Common Stock for no cash consideration, in accordance with the Certificate of Designations for the Series A Convertible Preferred Stock.

2. Fairmount Funds Management LLC and Fairmount Healthcare Fund II GP LLC have voting power and investment power over the securities held by Fairmount Healthcare Fund II LP ("Fund II"). They disclaim beneficial ownership of securities held by Fund II for purposes of Rule 16a-1(a)(2), except to the extent of their pecuniary interest therein.

Remarks:

This Form 4 is filed jointly with Fairmount Healthcare Fund II GP LLC. The Reporting Person may be deemed a director by deputization of Issuer by virtue of the fact that Peter Harwin serves on the board of directors of Issuer and is also a Managing Member of Fairmount Funds Management LLC.

	/s/ Tomas Kiselak for Fairmount Funds Management LLC	03/31/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did Fairmount report in Cogent Biosciences (COGT)?

Fairmount Healthcare Fund II LP converted 28,000 Series A Convertible Preferred shares into 7,000,000 Common shares, then sold all 7,000,000 Common shares at $34.66 each, significantly reducing its indirect common stock position in Cogent Biosciences.

How many Cogent Biosciences shares did Fairmount sell in this Form 4?

The fund sold 7,000,000 shares of Cogent Biosciences Common Stock. These shares were first obtained by converting 28,000 Series A Convertible Preferred shares, and the sale price was $34.66 per share in an open-market transaction on March 31, 2026.

What is Fairmount’s remaining Cogent Biosciences common stock holding after the sale?

After selling 7,000,000 Cogent Biosciences Common shares, Fairmount Healthcare Fund II LP indirectly holds 5,503,418 Common shares. Before the transaction, it held 12,503,418 Common shares, so the filing shows a substantial reduction in its common equity exposure.

What is the conversion ratio of Cogent’s Series A Convertible Preferred Stock?

Each share of Cogent’s Series A Convertible Preferred Stock is convertible into 250 shares of Common Stock. The filing notes this conversion is at the holder’s option and is subject to a 9.9% beneficial ownership cap to limit post-conversion ownership.

Does Fairmount still hold Cogent Biosciences preferred stock after this transaction?

Yes. Following the conversion of 28,000 preferred shares, Fairmount’s affiliated fund still holds 39,414 shares of Cogent’s Series A Convertible Preferred Stock. These remaining preferred shares are also convertible into Common Stock, subject to the 9.9% beneficial ownership limitation.

Who has voting and investment power over the Cogent shares mentioned in this Form 4?

The shares are held by Fairmount Healthcare Fund II LP. Fairmount Funds Management LLC and Fairmount Healthcare Fund II GP LLC have voting and investment power over these securities but disclaim beneficial ownership except to the extent of their pecuniary interest, as stated under Rule 16a-1(a)(2).