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  4. [Form 4] Dyne Therapeutics, Inc. Insider Trading Activity

Atlas Venture funds tied to Dyne (DYN) director sell 227,337 shares

Filing Impact
(Very High)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

Dyne Therapeutics, Inc. director-associated investment funds reported open-market sales of an aggregate 227,337 shares of Common Stock on April 28, 2026. The trades were executed at weighted-average prices around $18.38–$19.00 per share under a pre-arranged Rule 10b5-1 trading plan.

The shares are held through Atlas Venture-affiliated funds and partnerships, and the reporting person disclaims Section 16 beneficial ownership beyond any pecuniary interest. Following these transactions, the entities continue to hold large positions, including 4,939,489 shares in one fund and other seven-figure stakes in additional Atlas vehicles.

Positive

  • None.

Negative

  • None.
Insider Rhodes Jason P
Role null
Sold 227,337 shs ($4.18M)
Type Security Shares Price Value
Sale Common Stock 59,870 $18.38 $1.10M
Sale Common Stock 119,115 $18.38 $2.19M
Sale Common Stock 1,170 $18.38 $22K
Sale Common Stock 47,082 $18.38 $865K
Sale Common Stock 26 $19.00 $494.00
Sale Common Stock 52 $19.00 $988.00
Sale Common Stock 1 $19.00 $19.00
Sale Common Stock 21 $19.00 $399.00
Holdings After Transaction: Common Stock — 1,577,432 shares (Indirect, See footnote)
Footnotes (1)
  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 $18.00 to $18.98 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.
Shares sold 227,337 shares Aggregate Common Stock sales on April 28, 2026
Sale price (block 1) $19.00 per share Several sale entries on April 28, 2026
Sale price (block 2) $18.38 per share Additional sale entries on April 28, 2026
Post-sale holdings (largest fund) 4,939,489 shares Common Stock held indirectly after transactions
Post-sale holdings (other fund) 1,577,432 shares Common Stock held indirectly after transactions
Post-sale holdings (third fund) 1,158,944 shares Common Stock held indirectly after transactions
Rule 10b5-1 plan adoption date March 19, 2026 Plan governing April 28, 2026 sales
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.
weighted average price financial
"The price reported in Column 4 is a weighted average price."
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.
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, if any."
open-market sale financial
"transaction_action: open-market sale"
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.
pecuniary interest financial
"except to the extent of his pecuniary interest therein, if any."
Form 4 Insider Transactions: What Each Field Means →
SEC Form 4
FORM 4UNITED 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).
X
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)
XDirector10% Owner
Officer (give title below)Other (specify below)
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
04/28/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock04/28/2026S(1)59,870D$18.38(2)1,577,432ISee footnote(3)
Common Stock04/28/2026S(1)119,115D$18.38(2)4,939,489ISee footnote(4)
Common Stock04/28/2026S(1)1,170D$18.38(2)8,512ISee footnote(5)
Common Stock04/28/2026S(1)47,082D$18.38(2)1,158,944ISee footnote(6)
Common Stock04/28/2026S(1)26D$191,577,406ISee footnote(3)
Common Stock04/28/2026S(1)52D$194,939,437ISee footnote(4)
Common Stock04/28/2026S(1)1D$198,511ISee footnote(5)
Common Stock04/28/2026S(1)21D$191,158,923ISee 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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
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 $18.00 to $18.98 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.
/s/ Ommer Chohan, Attorney-in-Fact04/30/2026
** Signature of Reporting PersonDate
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) report in this Form 4?

Dyne Therapeutics reported that Atlas Venture–affiliated funds associated with director Jason P. Rhodes sold 227,337 shares of Common Stock in open-market transactions. These trades occurred on April 28, 2026 at weighted-average prices around $18.38 to $19.00 per share.

Were the Dyne Therapeutics (DYN) insider sales made under a trading plan?

Yes. The filing states the shares were sold under a Rule 10b5-1 trading plan adopted on March 19, 2026. Such plans pre-schedule trades, indicating the timing of these sales was planned in advance rather than being a discretionary decision on the trade date.

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

The shares are held by Atlas Venture funds and related partnerships, including Atlas Venture Opportunity Fund II and Atlas Venture Fund XI entities. Jason P. Rhodes reports these indirectly and disclaims Section 16 beneficial ownership except for any pecuniary interest he may have.

How many Dyne Therapeutics (DYN) shares did the entities hold after the sales?

After the April 28, 2026 transactions, the entities retained significant positions, including 4,939,489 shares in one fund, 1,577,432 shares in another, and 1,158,944 shares in a third, according to the post-transaction share balances disclosed in the Form 4 filing.

What price range did the Dyne Therapeutics (DYN) insider sales cover?

The filing notes a weighted-average price and explains that the Common Stock sales occurred in multiple trades between $18.00 and $18.98 per share. Specific lines show representative prices of $18.38 and $19.00 for different transaction blocks reported that day.

Are these Dyne Therapeutics (DYN) insider trades open-market sales or something else?

All reported transactions are non-derivative Common Stock sales coded “S,” described as open-market or private sales. There are no option exercises, gifts, or tax-withholding entries in this Form 4, and derivative holdings are not listed in the derivative summary.