DYN insider ownership: who sold, why, and what they still hold

What stands out

Brian Posner bought 18K shares for $315K, first on Mar 6, 2026.Purchase, Mar 6, 2026

Outside holders and shareholders represented on the board, not part of management, sold heavily: Jason Rhodes ($129M) and Dirk Kersten ($38.6M).Jason Rhodes: largest sale, Aug 14, 2026 · Dirk Kersten: largest sale, Jul 27, 2026

A share of stake is shown for 0 of the 4 officers and directors who sold. 13 are left out

Left out: John Cox, Erick Lucera, David Lubner, Johanna Friedl-Naderer, Douglas Kerr, Brian Posner, Jason Rhodes, Edward Hurwitz, Dirk Kersten, Catherine Stehman-Breen, Carlo Incerti, Vikram Karnani and Barry Greene (share of stake is being verified).

Disclosed company stock is not an insider's whole wealth.

Who sold, and how much of their stake

Officers and directors, past 12 months. Their share of stake is being verified and is not shown yet; amounts and trading plans are below.

John Cox

CEO & President, Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$444KDisclosed plan

Douglas Kerr

Chief Medical Officer

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$233KDisclosed plan

Erick Lucera

Chief Financial Officer

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$229K79% planned, 21% to cover taxes

Johanna Friedl-Naderer

Chief Commercial Officer

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$43KDisclosed plan

Amounts, filings and trading plans for each seller

Selling by month

Officers and directors, Oct 2025 to Oct 2026. Each sale is counted once: under a disclosed plan, else to cover taxes, else no plan disclosed.

Disclosed planTo cover taxesOne dollar scale for every month; the tallest bar is labeled

Recent activity

Past 30 days, Sep 14, 2026 to Oct 13, 2026

Oct 2, 2026Brian Posner bought 2.5K shares ($40K).

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Brian Posner Director	2,500	$16.00	n/a	n/a	Oct 2, 2026	Oct 6, 2026

"% of total stake" is the shares in an event against all the vested shares the person held that day, across every share class and holding entity, after that day's vesting. "n/a" means the person's holdings are not confirmed, or the row is a purchase. "Holdings record incomplete" means more shares were sold than the filings show the person held that day, so a percentage would be wrong.

Outside holders, reported separately

Jason Rhodes (for the outside shareholder represented on the board) sold $129M and Dirk Kersten (for the outside shareholder represented on the board) sold $38.6M in the past 12 months. Large shareholders and the funds or companies that board members represent are not part of management, so they are left out of the figures above.

Details

Common questions

Is the Dyne Therapeutics, Inc. CEO selling stock?

Yes. John Cox sold 22K shares ($444K) in the past 12 months, all of it under a trading plan disclosed in the filings.

Why are Dyne Therapeutics, Inc. insiders selling?

Filings rarely give a reason, and we don't guess at one. What they show is how the sales were made: 95% of sales by value ran under 10b5-1 trading plans disclosed in the filings and 5% were to cover taxes. A trading plan schedules sales in advance.

Are any Dyne Therapeutics, Inc. insiders buying?

Yes. 1 officer or director reported 8 purchases in the past 12 months (Form 4 code P; rows the filings describe as reinvested dividends, plan purchases, private deals or moves into the person's own trust are not counted).

The evidence

Who sold4 officers and directors: amount, % of holdings, trading plan

Who sold	Amount	% of holdings	Trading plan
John Cox CEO & President, Director	$444K 22K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Douglas Kerr Chief Medical Officer	$233K 11K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Erick Lucera Chief Financial Officer	$229K 11K shares	Not confirmed share of stake is being verified. Why	79% under a disclosed plan, 21% to cover taxes
Johanna Friedl-Naderer Chief Commercial Officer	$43K 2K shares	Not confirmed share of stake is being verified. Why	Disclosed plan

Board members representing outside shareholders, reported separately: Jason Rhodes (the shareholder sold $129M), Dirk Kersten (the shareholder sold $38.6M), Edward Hurwitz. Details

The full ownership picture0 of 13 officers and directors confirmed

Vested shares across all share classes, held directly and through trusts, LLCs and family members, as reported on SEC Forms 3, 4 and 5. Unvested awards and options are never counted as owned shares.

Insider

Held Oct 13, 2025

Sold

Held Oct 13, 2026

Still held

John Cox

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for John Cox are complete.

CEO & President, Director

n/a

−22K

n/a

Vesting, gifts, unvested awards and holding lines for John Cox

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for John Cox are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
679,853	$26.06	Mar 24, 2034	$0
232,100	$29.44	Dec 3, 2034	$0
197,285	$9.33	Jul 15, 2035	$1.3M
285,000	$16.00	Feb 11, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Erick Lucera

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Erick Lucera are complete.

Chief Financial Officer

n/a

−11K

n/a

Vesting, gifts, unvested awards and holding lines for Erick Lucera

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Erick Lucera are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
214,500	$10.46	Mar 30, 2035	$1.2M
105,000	$16.00	Feb 11, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

David Lubner

Director

n/a

Vesting, gifts, unvested awards and holding lines for David Lubner

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for David Lubner are complete; balances and unit counts will be added when the check is finished.

−54Kgifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Johanna Friedl-Naderer

Chief Commercial Officer

n/a

−2K

n/a

Vesting, gifts, unvested awards and holding lines for Johanna Friedl-Naderer

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Johanna Friedl-Naderer are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
185,300	$31.94	Sep 2, 2034	$0
60,300	$29.44	Dec 3, 2034	$0
51,255	$9.33	Jul 15, 2035	$342K
90,000	$16.00	Feb 11, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Douglas Kerr

Chief Medical Officer

n/a

−11K

n/a

Vesting, gifts, unvested awards and holding lines for Douglas Kerr

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Douglas Kerr are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
150,300	$31.94	Sep 2, 2034	$0
76,600	$29.44	Dec 3, 2034	$0
65,110	$9.33	Jul 15, 2035	$434K
130,000	$16.00	Feb 11, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Brian Posner

Director

n/a

Vesting, gifts, unvested awards and holding lines for Brian Posner

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Brian Posner are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
70,000	$12.50	Sep 30, 2035	$245K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Jason Rhodes

Director

n/a

Vesting, gifts, unvested awards and holding lines for Jason Rhodes

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Jason Rhodes are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Edward Hurwitz

Director

n/a

Vesting, gifts, unvested awards and holding lines for Edward Hurwitz

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Edward Hurwitz are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Dirk Kersten

Director

n/a

Vesting, gifts, unvested awards and holding lines for Dirk Kersten

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Dirk Kersten are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Catherine Stehman-Breen

Director

n/a

Vesting, gifts, unvested awards and holding lines for Catherine Stehman-Breen

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Catherine Stehman-Breen are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Carlo Incerti

Director

n/a

Vesting, gifts, unvested awards and holding lines for Carlo Incerti

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Carlo Incerti are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
22,693	$8.69	Mar 1, 2032	$166K
25,133	$31.53	May 21, 2034	$0
35,000	$11.96	May 29, 2035	$141K
35,152	$17.04	Jun 4, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Vikram Karnani

Director

n/a

Vesting, gifts, unvested awards and holding lines for Vikram Karnani

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Vikram Karnani are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
59,665	$20.78	Dec 21, 2035	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Barry Greene

Director

n/a

Vesting, gifts, unvested awards and holding lines for Barry Greene

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Barry Greene are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
57,463	$20.87	Jun 21, 2036	$0

Estimate: options held × ($16.00 − strike price), using the most recent insider trade price on Form 4 (Oct 2, 2026), not a market close.

Holdings and share of stake for Dyne Therapeutics, Inc. are being verified, so no balances, unit counts or percentages are shown. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings.

What explains the selling$949K of sales by plan status, purpose, seller and month

Officer and director open-market sales: $949K across 46,168 shares. Plan status and stated purpose are separate questions, and a sale can have both.

By plan status

Disclosed plan · $901K · 95%

The lighter segment is sales with no plan disclosed in the filing ($48K), including tax-related sales outside a plan.

Taxes

$949K of sales (100.0%) cite tax obligations in their footnotes, $901K of them also under a plan. Example: Douglas Kerr, Sep 8, 2026

Purchases · 1 buyer (8 trades)

1 officer or director bought shares in this period, in 8 trades(Form 4 code P, leaving out rows the filings describe as reinvested dividends, plan purchases, private deals or moves into the person's own trust). Across all their filings on record there are 17 purchase trades.

Seller	Shares sold	Proceeds	Under a disclosed plan	Share of total	Sales dates
John Cox CEO & President, Director	22K	$444K	100%	47%	Dec 5, 2025 to Sep 8, 2026
Douglas Kerr Chief Medical Officer	11K	$233K	100%	25%	Dec 5, 2025 to Sep 8, 2026
Erick Lucera Chief Financial Officer	11K	$229K	79%	24%	Apr 1, 2026 to Aug 13, 2026
Johanna Friedl-Naderer Chief Commercial Officer	2K	$43K	100%	5%	Dec 5, 2025 to Sep 8, 2026

Sales by month

Month	Sale proceeds	Disclosed plan	To cover taxes	No plan disclosed
Oct 2025	$0	$0	$0	$0
Nov 2025	$0	$0	$0	$0
Dec 2025	$76K	$76K	$0	$0
Jan 2026	$0	$0	$0	$0
Feb 2026	$0	$0	$0	$0
Mar 2026	$56K	$56K	$0	$0
Apr 2026	$107K	$107K	$0	$0
May 2026	$120K	$120K	$0	$0
Jun 2026	$116K	$68K	$48K	$0
Jul 2026	$0	$0	$0	$0
Aug 2026	$225K	$225K	$0	$0
Sep 2026	$248K	$248K	$0	$0
Oct 2026	$0	$0	$0	$0

Board members representing outside shareholders (3)Listed and sourced; not part of the management totals or the answer line

Directors whose reported holdings sit mostly in an investment fund or a corporate shareholder they represent, not in their own name, with beneficial ownership disclaimed except for their own financial interest. Listed and sourced here; not part of the management totals or the answer line. Shares a fund hands to its own investors are distributions, not sales.

Board member	Held Oct 13, 2025	Sold	Held Oct 13, 2026	Still held
Jason Rhodes ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Jason Rhodes are complete. Director	n/a	−5.69M	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Jason Rhodes Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Jason Rhodes are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)
Dirk Kersten ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Dirk Kersten are complete. Director	n/a	−1.88M	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Dirk Kersten Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Dirk Kersten are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)
Edward Hurwitz ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Edward Hurwitz are complete. Director	n/a	0	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Edward Hurwitz Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Edward Hurwitz are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)

Is this normal? Selling year by year5 earlier years to compare with

Less than usual: about one-tenth of the 5-year average. 4 insiders sold; the average is 6 a year.

12 months ending	Shares sold	Insiders who sold	Proceeds
Oct 13, 2026 Latest 12 months	46K	4	$949K
Oct 13, 2025 1 year earlier	56K	6	$1.1M
Oct 13, 2024 2 years earlier	1.68M	6	$43.1M
Oct 14, 2023 3 years earlier	485K	6	$6.1M
Oct 14, 2022 4 years earlier	222K	6	$2.7M
Oct 14, 2021 5 years earlier	14K	5	$226K

Open-market sales (Form 4 code S) by people who were officers or directors, in split-adjusted shares. Earlier years include people who have since left. A sale that an outside holder also reports (a family trust, a fund) is counted with outside holders in every year. Shares, not dollars, are compared, so a change in the stock price doesn't look like a change in selling. Years the filings don't fully cover are shown but left out of the average.

Known gaps and uncertainty13 officers and directors not confirmed

Holdings and share of stake are being verified. Balances, unit counts and every share-of-stake figure for Dyne Therapeutics, Inc. are held back until that check is finished. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings and are complete.

External context: we only cite outside events when a documented connection exists. None is shown for this period.

Sources and methodology360 filings on record, 61 filed in the 12-month period, and how we read them

All 360 Forms 3, 4 and 5 on record for Dyne Therapeutics, Inc. (SEC CIK 1818794), filed from Sep 16, 2020 to Oct 6, 2026; 61 of them were filed in the 12 months this page covers, retrieved from SEC EDGAR on Oct 13, 2026. Prices are the ones reported in each filing, often weighted averages.

Holdings. Each holding line (a share class plus an owner, such as a trust or LLC) carries its last reported balance forward. Entities first reported during the period start at zero, so transfers between an insider's own trusts don't count as selling. Lines not reported for three years or more are listed separately and left out of totals.

Sales. A sale counts as under a 10b5-1 plan if its footnote cites one or the filing's Rule 10b5-1 box is checked, and as tax-related if its footnote cites tax obligations or sell-to-cover. Shares withheld by the company for taxes are listed separately. Sales with neither attribute are labeled "no plan disclosed".

Full methodology

Former or inactive filers (15)No filing in 18 months; last reported balances, not in any total

Name	Last filed	Last reported balance
Oxana Beskrovnaya	Mar 13, 2025	43,001 shares, last reported balance as of Mar 11, 2025
Richard Scalzo	Mar 13, 2025	13,276 shares, last reported balance as of Mar 11, 2025
Susanna High	Sep 19, 2024	17,183 shares, last reported balance as of Sep 18, 2024
Jonathan McNeill	Aug 20, 2024	15,231 shares, last reported balance as of Aug 19, 2024
Wildon Farwell	Aug 20, 2024	32,814 shares, last reported balance as of Aug 19, 2024
Joshua Brumm	Mar 12, 2024	24,085 shares, last reported balance as of Mar 11, 2024
Atlas Venture Fund XI, L.P.	Mar 5, 2024	11,120,322 shares, last reported balance as of Mar 1, 2024
Lawrence Klein	Jul 6, 2022	10,725 shares, last reported balance as of Sep 21, 2020
VV Manager II, LLC	Sep 23, 2020	2,960,046 shares, last reported balance as of Sep 21, 2020
CureDuchenne Ventures, LLC	Sep 23, 2020	602,972 shares, last reported balance as of Sep 21, 2020
Logos Global Management LP	Sep 23, 2020	1,504,392 shares, last reported balance as of Sep 21, 2020
MPM BIOVENTURES 2018, L.P.	Sep 23, 2020	4,951,303 shares, last reported balance as of Sep 21, 2020
Wellington Biomedical Innovation Master Investors (Cayman) I L.P.	Sep 23, 2020	1,608,785 shares, last reported balance as of Sep 21, 2020
RA CAPITAL MANAGEMENT, L.P.	Sep 23, 2020	2,805,045 shares, last reported balance as of Sep 21, 2020
Romesh Subramanian	Sep 18, 2020	566,249 shares, last reported balance as of Sep 17, 2020

Spotted something wrong on this page? Report an error. We check every report against the SEC filing and list what we fix in the corrections log.

Dyne Therapeutics, Inc. insiders sold $949K in the past 12 months. How much of their stake is that?

What stands out

Who sold, and how much of their stake

Selling by month

Recent activity

Outside holders, reported separately

Common questions

Is the Dyne Therapeutics, Inc. CEO selling stock?

Why are Dyne Therapeutics, Inc. insiders selling?

Are any Dyne Therapeutics, Inc. insiders buying?

The evidence

Taxes

Purchases · 1 buyer (8 trades)

Sales by month