Atlas Venture funds sell Dyne (DYN) shares under 10b5-1 plan

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director-affiliated investment funds reported open-market sales of a combined 834,302 shares of common stock over April 20–22, 2026. The transactions were executed at weighted-average prices generally between $19.035 and $20.354 per share.

The shares are held indirectly through Atlas Venture funds and related general partners, and the reporting person Jason P. Rhodes disclaims Section 16 beneficial ownership except for any pecuniary interest. The sales were made pursuant to a Rule 10b5-1 trading plan adopted on March 19, 2026.

Insider Trade Summary 10b5-1

Net Seller: 834,302 shares ($16,477,388)

Net Sell 16 txns

Insider Rhodes Jason P

Role null

Sold 834,302 shs ($16.48M)

Type	Security	Shares	Price	Value
Sale	Common Stock	75,866	$19.68	$1.49M
Sale	Common Stock	150,942	$19.68	$2.97M
Sale	Common Stock	1,485	$19.68	$29K
Sale	Common Stock	59,663	$19.68	$1.17M
Sale	Common Stock	71,499	$19.51	$1.39M
Sale	Common Stock	142,253	$19.51	$2.78M
Sale	Common Stock	1,398	$19.51	$27K
Sale	Common Stock	56,228	$19.51	$1.10M
Sale	Common Stock	769	$20.05	$15K
Sale	Common Stock	1,530	$20.05	$31K
Sale	Common Stock	15	$20.05	$300.75
Sale	Common Stock	605	$20.05	$12K
Sale	Common Stock	71,676	$20.06	$1.44M
Sale	Common Stock	142,604	$20.06	$2.86M
Sale	Common Stock	1,401	$20.06	$28K
Sale	Common Stock	56,368	$20.06	$1.13M

Holdings After Transaction: Common Stock — 1,738,617 shares (Indirect, See footnote)

Footnotes (1)

Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 19, 2026. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.88 to $20.354 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote. The shares are owned directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, LP ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. The Reporting Person is a member of AVAO II LLC and disclaims Section 16 beneficial ownership of such securities held by AVOF II, except to the extent of his pecuniary interest therein, if any. The shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas Venture Fund XI"). The general partner of Atlas Venture Fund XI is Atlas Venture Associates XI, L.P. ("AVA XI LP"). Atlas Venture Associates XI, LLC ("AVA XI LLC") is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of such securities held by Atlas Venture Fund XI, except to the extent of his pecuniary interest therein, if any. The shares are held directly by AVA XI LP. AVA XI LLC is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of the securities held by AVA XI LP, except to the extent of his pecuniary interest therein, if any. The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("AVOF I"). The general partner of AVOF I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. The Reporting Person is a member of AVAO I LLC and disclaims Section 16 beneficial ownership of such securities held by AVOF I, except to the extent of his pecuniary interest therein, if any. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.035 to $20.0301 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $20.04 to $20.0829 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.05 to $20.02 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

Key Figures

Shares sold: 834,302 shares Price range footnote group 1: $19.88–$20.354 per share Price range footnote group 2: $19.035–$20.0301 per share +3 more

6 metrics

Shares sold 834,302 shares Total common shares sold across 16 open-market transactions

Price range footnote group 1 $19.88–$20.354 per share Weighted-average sale price range described in one footnote

Price range footnote group 2 $19.035–$20.0301 per share Weighted-average sale price range described in another footnote

Price range footnote group 3 $20.04–$20.0829 per share Additional weighted-average sale price range disclosed

Example remaining position 5,554,904 shares Indirect holding for one Atlas Venture-affiliated fund after an April 20, 2026 sale

Sell transactions 16 transactions Total count of reported open-market sales of common stock

Key Terms

Rule 10b5-1 trading plan, Section 16 beneficial ownership, weighted average price, indirect ownership, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 19, 2026."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

Section 16 beneficial ownership regulatory

"disclaims Section 16 beneficial ownership of such securities held by AVOF II, except to the extent of his pecuniary interest therein"

weighted average price financial

"The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

indirect ownership financial

"direct_or_indirect": "I", "nature_of_ownership": "See footnote""

pecuniary interest financial

"disclaims Section 16 beneficial ownership of such securities held by AVOF II, except to the extent of his pecuniary interest therein"

Form 4 Insider Transactions: What Each Field Means →

04/22/2026 - 06:27 PM

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^*

Rhodes Jason P

(Last)

(First)

(Middle)

C/O DYNE THERAPEUTICS, INC.

830 WINTER ST.

(Street)

WALTHAM

MASSACHUSETTS

02451

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Dyne Therapeutics, Inc. [ DYN ]

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)
04/20/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	04/20/2026		S⁽¹⁾		71,676	D	$20.06⁽²⁾	1,886,751	I	See footnote⁽³⁾
Common Stock	04/20/2026		S⁽¹⁾		142,604	D	$20.06⁽²⁾	5,554,904	I	See footnote⁽⁴⁾
Common Stock	04/20/2026		S⁽¹⁾		1,401	D	$20.06⁽²⁾	14,561	I	See footnote⁽⁵⁾
Common Stock	04/20/2026		S⁽¹⁾		56,368	D	$20.06⁽²⁾	1,402,200	I	See footnote⁽⁶⁾
Common Stock	04/21/2026		S⁽¹⁾		71,499	D	$19.51⁽⁷⁾	1,815,252	I	See footnote⁽³⁾
Common Stock	04/21/2026		S⁽¹⁾		142,253	D	$19.51⁽⁷⁾	5,412,651	I	See footnote⁽⁴⁾
Common Stock	04/21/2026		S⁽¹⁾		1,398	D	$19.51⁽⁷⁾	13,163	I	See footnote⁽⁵⁾
Common Stock	04/21/2026		S⁽¹⁾		56,228	D	$19.51⁽⁷⁾	1,345,972	I	See footnote⁽⁶⁾
Common Stock	04/21/2026		S⁽¹⁾		769	D	$20.05⁽⁸⁾	1,814,483	I	See footnote⁽³⁾
Common Stock	04/21/2026		S⁽¹⁾		1,530	D	$20.05⁽⁸⁾	5,411,121	I	See footnote⁽⁴⁾
Common Stock	04/21/2026		S⁽¹⁾		15	D	$20.05⁽⁸⁾	13,148	I	See footnote⁽⁵⁾
Common Stock	04/21/2026		S⁽¹⁾		605	D	$20.05⁽⁸⁾	1,345,367	I	See footnote⁽⁶⁾
Common Stock	04/22/2026		S⁽¹⁾		75,866	D	$19.68⁽⁹⁾	1,738,617	I	See footnote⁽³⁾
Common Stock	04/22/2026		S⁽¹⁾		150,942	D	$19.68⁽⁹⁾	5,260,179	I	See footnote⁽⁴⁾
Common Stock	04/22/2026		S⁽¹⁾		1,485	D	$19.68⁽⁹⁾	11,663	I	See footnote⁽⁵⁾
Common Stock	04/22/2026		S⁽¹⁾		59,663	D	$19.68⁽⁹⁾	1,285,704	I	See footnote⁽⁶⁾

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on March 19, 2026.

2. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.88 to $20.354 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

3. The shares are owned directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, LP ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. The Reporting Person is a member of AVAO II LLC and disclaims Section 16 beneficial ownership of such securities held by AVOF II, except to the extent of his pecuniary interest therein, if any.

4. The shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas Venture Fund XI"). The general partner of Atlas Venture Fund XI is Atlas Venture Associates XI, L.P. ("AVA XI LP"). Atlas Venture Associates XI, LLC ("AVA XI LLC") is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of such securities held by Atlas Venture Fund XI, except to the extent of his pecuniary interest therein, if any.

5. The shares are held directly by AVA XI LP. AVA XI LLC is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of the securities held by AVA XI LP, except to the extent of his pecuniary interest therein, if any.

6. The shares are held directly by Atlas Venture Opportunity Fund I, L.P. ("AVOF I"). The general partner of AVOF I is Atlas Venture Associates Opportunity I, L.P. ("AVAO I LP"). Atlas Venture Associates Opportunity I, LLC ("AVAO I LLC") is the general partner of AVAO I LP. The Reporting Person is a member of AVAO I LLC and disclaims Section 16 beneficial ownership of such securities held by AVOF I, except to the extent of his pecuniary interest therein, if any.

7. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.035 to $20.0301 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

8. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $20.04 to $20.0829 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

9. The price reported in Column 4 is a weighted average price. These securities were sold in multiple transactions at prices ranging from $19.05 to $20.02 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of securities sold at each separate price within the range set forth in this footnote.

	/s/ Ommer Chohan, Attorney-in-Fact	04/22/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What insider activity did Dyne Therapeutics (DYN) disclose in this Form 4?

Dyne Therapeutics disclosed that investment funds affiliated with director Jason P. Rhodes sold 834,302 shares of common stock. These were open-market transactions reported as indirect sales through Atlas Venture entities rather than personal direct sales by Rhodes.

Over what dates were the Dyne Therapeutics (DYN) shares sold and at what prices?

The reported sales occurred from April 20 to April 22, 2026. Footnotes state the shares were sold in multiple trades at weighted-average prices within ranges roughly between $19.035 and $20.354 per share, depending on the specific transaction group.

Who actually owns the Dyne Therapeutics (DYN) shares involved in these transactions?

The shares are owned by Atlas Venture funds and related partnerships, including Atlas Venture Opportunity Fund II, Atlas Venture Fund XI, and other affiliated entities. Jason P. Rhodes is a member of the relevant general partner LLCs and disclaims Section 16 beneficial ownership except for any pecuniary interest.

Were the Dyne Therapeutics (DYN) insider sales made under a Rule 10b5-1 trading plan?

Yes. A footnote explains that the shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 19, 2026. Such plans pre-schedule trades, which can indicate the timing was determined in advance rather than based on near-term developments.

How many transactions and what type of trades were reported for Dyne Therapeutics (DYN)?

The summary data show 16 sell transactions and no purchases. All reported trades involved non-derivative common stock and are described as sales in the open market or private transactions, executed indirectly through Atlas Venture-affiliated entities holding Dyne Therapeutics shares.

What Dyne Therapeutics (DYN) holdings remain after these reported insider sales?

Each entity’s remaining position is reported separately. For example, one Atlas Venture-affiliated fund shows 5,554,904 shares of Dyne Therapeutics common stock following an April 20, 2026 sale, while other related funds report smaller but still substantial indirect holdings after their respective transactions.