# EDGAR Filing Document

**Accession Number:** 0001729505
**File Stem:** 0001193125-23-029988
**Filing Date:** 2023-2
**Character Count:** 28061
**Document Hash:** 6e28cc797870de6648a93e63c9bb9ff6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-23-029988.hdr.sgml**: 20230209

**ACCESSION NUMBER**: 0001193125-23-029988

**CONFORMED SUBMISSION TYPE**: SC 13G/A

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20230209

**DATE AS OF CHANGE**: 20230209

**GROUP MEMBERS**: ANSBERT GADICKE

**GROUP MEMBERS**: ED HURWITZ

**GROUP MEMBERS**: LUKE EVNIN

**GROUP MEMBERS**: MPM ASSET MANAGEMENT INVESTORS BV2018 LLC

**GROUP MEMBERS**: MPM BIOVENTURES 2018 (B), L.P.

**GROUP MEMBERS**: MPM BIOVENTURES 2018 GP LLC

**GROUP MEMBERS**: MPM BIOVENTURES 2018 LLC

**GROUP MEMBERS**: TODD FOLEY

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Dyne Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001818794
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **IRS NUMBER:** 364883909
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-91706
- **FILM NUMBER:** 23606153

**BUSINESS ADDRESS:**
- **STREET 1:** 1560 TRAPELO ROAD
- **CITY:** WALTHAM
- **STATE:** MA
- **ZIP:** 02451
- **BUSINESS PHONE:** (781) 786-8230

**MAIL ADDRESS:**
- **STREET 1:** 1560 TRAPELO ROAD
- **CITY:** WALTHAM
- **STATE:** MA
- **ZIP:** 02451
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MPM BIOVENTURES 2018, L.P.
- **CENTRAL INDEX KEY:** 0001729505
- **IRS NUMBER:** 823687697
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SC 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** 450 KENDALL STREET
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142
- **BUSINESS PHONE:** 617-425-9200

**MAIL ADDRESS:**
- **STREET 1:** 450 KENDALL STREET
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142

------

------

**UNITED STATES** 

**SECURITIES AND EXCHANGE COMMISSION** 

**Washington, D.C. 20549** 

------

## SCHEDULE 13G
**Under the Securities Exchange Act of 1934** 

**(Amendment No. 1)\*** 

------

**Dyne Therapeutics, Inc.** 

**(Name of Issuer)** 

**Common Stock** 

**(Title of Class of Securities)** 

**26818M108** 

**(CUSIP Number)** 

**December 31, 2022** 

**(Date of Event Which Requires Filing of This Statement)** 

------

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☐ Rule 13d-1(c)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;☒ Rule 13d-1(d)

\* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

------

CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; MPM BioVentures 2018, L.P.

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; Delaware

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,614,943 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,614,943 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,614,943

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 8.9%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; PN

Page 2 of 16

------

CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; MPM BioVentures 2018 (B), L.P.

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; Germany

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;245,279 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;245,279 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 245,279

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 0.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; PN

Page 3 of 16

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CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; MPM Asset Management Investors BV2018 LLC

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; Delaware

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;91,081 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;91,081 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 91,081

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 0.2%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; OO

Page 4 of 16

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CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; MPM BioVentures 2018 GP LLC

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; Delaware

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,860,222\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,860,222\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,860,222\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.3%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; PN

\* Consists of 4,614,943 shares held by MPM BioVentures 2018, L.P. ("BV 2018") and 245,279 shares held by MPM BioVentures 2018(B), L.P. ("BV 2018(B)"). MPM BioVentures 2018 GP LLC ("BV 2018 GP") and MPM BioVentures 2018 LLC ("BV 2018 LLC") are the direct and indirect general partners of BV 2018 and BV 2018(B). 

Page 5 of 16

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CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; MPM BioVentures 2018 LLC

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; Delaware

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,951,303\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; OO

\* Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by MPM Asset Management Investors BV2018 LLC ("AM BV 2018 LLC"). BV 2018 GP and BV 2018 LLC are the direct and indirect general partners of BV 2018 and BV 2018(B). BV 2018 LLC is the manager of AM BV 2018 LLC. 

Page 6 of 16

------

CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; Luke Evnin

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; United
States

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,951,303\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; IN

\* Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM BV 2018 LLC. The Reporting Person is a managing director of BV 2018 LLC.

Page 7 of 16

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CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; Ansbert Gadicke

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; United
States

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,951,303\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; IN

\* Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM BV 2018 LLC. The Reporting Person is a managing director of BV 2018 LLC.

Page 8 of 16

------

CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; Todd Foley

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; United
States

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;0 |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,951,303\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; IN

\* Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM BV 2018 LLC. The Reporting Person is a managing director of BV 2018 LLC.

Page 9 of 16

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CUSIP No. 26818M108

1. &nbsp;&nbsp;&nbsp;&nbsp; Name of Reporting Persons &nbsp;&nbsp;&nbsp;&nbsp; Ed Hurwitz

2. &nbsp;&nbsp;&nbsp;&nbsp; Check the Appropriate Box
if a Member of a Group (See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; (a) ☐ (b) ☒

3. &nbsp;&nbsp;&nbsp;&nbsp; SEC USE ONLY

4. &nbsp;&nbsp;&nbsp;&nbsp; Citizenship or Place of
Organization &nbsp;&nbsp;&nbsp;&nbsp; United
States

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 5. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;19,596\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 6. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Voting Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\*\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 7. | &nbsp;&nbsp;&nbsp;&nbsp;Sole Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;19,596\* |
| &nbsp;&nbsp;&nbsp; Number of<br> Shares<br> Beneficially <br> Owned by<br> Each<br> Reporting<br> Person<br> With: | 8. | &nbsp;&nbsp;&nbsp;&nbsp;Shared Dispositive Power<br>&nbsp;&nbsp;&nbsp;&nbsp;4,951,303\*\* |

---

9. &nbsp;&nbsp;&nbsp;&nbsp; Aggregate Amount Beneficially Owned by Each Reporting Person &nbsp;&nbsp;&nbsp;&nbsp; 4,970,899\* \*\*

10. &nbsp;&nbsp;&nbsp;&nbsp; Check if the Aggregate
Amount in Row (9) Excludes Certain Shares (See Instructions)

11. &nbsp;&nbsp;&nbsp;&nbsp; Percent of
Class Represented by Amount in Row (9) &nbsp;&nbsp;&nbsp;&nbsp; 9.5%

12. &nbsp;&nbsp;&nbsp;&nbsp; Type of Reporting Person
(See Instructions) &nbsp;&nbsp;&nbsp;&nbsp; IN

\* Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM BV 2018 LLC. The Reporting Person is a managing director of BV 2018 LLC.

\*\* Includes 19,596 shares exercisable pursuant to options within 60 days of December 31, 2022.

Page 10 of 16

------

**Item 1.**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) Name of Issuer

Dyne Therapeutics, Inc.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Address of Issuer's Principal Executive Offices

80 Winter Street

Waltham MA 02451

**Item 2.**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) Name of Person Filing

MPM BioVentures 2018, L.P.

MPM BioVentures 2018(B), L.P.

MPM Asset Management Investors BV2018 LLC

MPM BioVentures 2018 GP LLC

MPM BioVentures 2018 LLC

Luke Evnin

Ansbert Gadicke

Todd Foley

Ed Hurwitz

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Address of Principal Business Office or, if none, Residence

c/o MPM Capital LLC

399 Boylston Street, Suite 1100

Boston, MA 02116

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c) Citizenship

All entities were organized in Delaware. The individuals are all United States citizens.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d) Title of Class of Securities

Common Stock

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(e) CUSIP Number

26818M108

**Item 3.** **If this statement is filed pursuant to §§240.13d-1(b), or 240.13d-2(b) or (c), check whether the person filing is a:** <br>

Not applicable

Page 11 of 16

------

**Item 4.** **Ownership** <br>

---

| | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|
| **MPM Entity** | **Shares<br>Held<br>Directly** | **Sole Voting<br>Power** | **Shared<br>Voting<br>Power** | **Sole<br>Dispositive<br>Power** | **Shared<br>Dispositive<br>Power** | **Beneficial<br>Ownership** | **Percentage<br>of Class** |
|  BV 2018 | 4614943 | 4614943 | 0 | 4614943 | 0 | 4614943 | 8.9% |
|  BV 2018(B) | 245279 | 245279 | 0 | 245279 | 0 | 245279 | 0.5% |
|  AM BV 2018 LLC | 91081 | 91081 | 0 | 91081 | 0 | 91081 | 0.2% |
|  BV 2018 GP(1) | 0 | 0 | 4860222 | 0 | 4860222 | 4860222 | 9.3% |
|  BV 2018 LLC(2) | 0 | 0 | 4951303 | 0 | 4951303 | 4951303 | 9.5% |
|  Luke Evnin(3) | 0 | 0 | 4951303 | 0 | 4951303 | 4951303 | 9.5% |
|  Ansbert Gadicke(3) | 0 | 0 | 4951303 | 0 | 4951303 | 4951303 | 9.5% |
|  Todd Foley(3) | 0 | 0 | 4951303 | 0 | 4951303 | 4951303 | 9.5% |
|  Ed Hurwitz(3)(4) | 19596 | 19596 | 4951303 | 19596 | 4951303 | 4970899 | 9.5% |

---

(1) Consists of 4,614,943 shares held by BV 2018 and 245,279 shares held by BV 2018(B). BV 2018 GP and BV 2018 LLC
are the direct and indirect general partners of BV 2018 and BV 2018(B).

(2) Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM
BV2018 LLC. BV 2018 GP and BV 2018 LLC are the direct and indirect general partners of BV 2018 and BV 2018(B). BV 2018 LLC is the manager of AM BV2018 LLC.

(3) Consists of 4,614,943 shares held by BV 2018, 245,279 shares held by BV 2018(B) and 91,081 shares held by AM
BV2018 LLC. The Reporting Person is a managing director of BV 2018 LLC.

(4) Includes 19,596 shares exercisable pursuant to options within 60 days of December 31, 2022.

**Item 5.** **Ownership of Five Percent or Less of a Class** <br>

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following ☐.

**Item 6.** **Ownership of More than Five Percent on Behalf of Another Person** <br>

Not Applicable

**Item 7.** **Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.** <br>

Not Applicable

**Item 8.** **Identification and Classification of Members of the Group** <br>

Not Applicable

**Item 9.** **Notice of Dissolution of a Group** <br>

Not Applicable

**Item 10.** **Certification** <br>

Not Applicable

Page 12 of 16

------

**<u>SIGNATURE</u>**

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

---

| | |
|:---|:---|
| Date: February 8, 2023 | Date: February 8, 2023 |
| **MPM BIOVENTURES 2018, L.P.** | **MPM BIOVENTURES 2018, L.P.** |
| By: | MPM BioVentures 2018 GP LLC, |
|  | its General Partner |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM BIOVENTURES 2018 (B), L.P.** | **MPM BIOVENTURES 2018 (B), L.P.** |
| By: | MPM BioVentures 2018 GP LLC, |
|  | its General Partner |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM ASSET MANAGEMENT INVESTORS BV2018 LLC** | **MPM ASSET MANAGEMENT INVESTORS BV2018 LLC** |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Manager |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM BIOVENTURES 2018 GP LLC** | **MPM BIOVENTURES 2018 GP LLC** |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |

---

Page 13 of 16

------

---

| | |
|:---|:---|
| **MPM BIOVENTURES 2018 LLC** | **MPM BIOVENTURES 2018 LLC** |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| By: | /s/ Todd Foley |
| Name: | Todd Foley |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| By: | /s/ Ansbert Gadicke |
| Name: | Ansbert Gadicke |
| By: | /s/ Edward Hurwitz |
| Name: | Edward Hurwitz |

---

**EXHIBITS** 

A: Joint Filing Agreement

Page 14 of 16

## Ex-99.A

<u>EXHIBIT A</u> 

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the Common Stock of Dyne Therapeutics, Inc. and further agree that this agreement be included as an exhibit to such filing. Each party to the agreement expressly authorizes each other party to file on its behalf any and all amendments to such statement. Each party to this agreement agrees that this joint filing agreement may be signed in counterparts.

In evidence whereof, the undersigned have caused this Agreement to be executed on their behalf this 8<sup>th</sup> day of February, 2023.

---

| | |
|:---|:---|
| **MPM BIOVENTURES 2018, L.P.** | **MPM BIOVENTURES 2018, L.P.** |
| By: | MPM BioVentures 2018 GP LLC, |
|  | its General Partner |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM BIOVENTURES 2018 (B), L.P.** | **MPM BIOVENTURES 2018 (B), L.P.** |
| By: | MPM BioVentures 2018 GP LLC, |
|  | its General Partner |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM ASSET MANAGEMENT INVESTORS BV2018 LLC** | **MPM ASSET MANAGEMENT INVESTORS BV2018 LLC** |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Manager |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| **MPM BIOVENTURES 2018 GP LLC** | **MPM BIOVENTURES 2018 GP LLC** |
| By: | MPM BioVentures 2018 LLC, |
|  | Its Managing Member |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |

---

Page 15 of 16

------

---

| | |
|:---|:---|
| **MPM BIOVENTURES 2018 LLC** | **MPM BIOVENTURES 2018 LLC** |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| Title: | Managing Director |
| By: | /s/ Todd Foley |
| Name: | Todd Foley |
| By: | /s/ Luke Evnin |
| Name: | Luke Evnin |
| By: | /s/ Ansbert Gadicke |
| Name: | Ansbert Gadicke |
| By: | /s/ Edward Hurwitz |
| Name: | Edward Hurwitz |

---

Page 16 of 16