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).

1. Name and Address of Reporting Person* MPM BIOVENTURES 2018, L.P. (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Dyne Therapeutics, Inc. [ DYN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 09/21/2020
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

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	09/21/2020		C		4,614,943	A	(1)(5)	4,614,943	I	See footnote(2)
Common Stock	09/21/2020		C		245,279	A	(1)(5)	245,279	I	See footnote(3)
Common Stock	09/21/2020		C		91,081	A	(1)(5)	91,081	I	See footnote(4)

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 Preferred Stock	(1)	09/21/2020		C			13,980,992	(1)	(1)	Common Stock	4,215,076	$0.00	0	I	See footnote(2)
Series A Preferred Stock	(1)	09/21/2020		C			743,076	(1)	(1)	Common Stock	224,025	$0.00	0	I	See footnote(3)
Series A Preferred Stock	(1)	09/21/2020		C			275,932	(1)	(1)	Common Stock	83,188	$0.00	0	I	See footnote(4)
Series B Preferred Stock	(5)	09/21/2020		C			1,326,313	(5)	(5)	Common Stock	399,867	$0.00	0	I	See footnote(2)
Series B Preferred Stock	(5)	09/21/2020		C			70,492	(5)	(5)	Common Stock	21,254	$0.00	0	I	See footnote(3)
Series B Preferred Stock	(5)	09/21/2020		C			26,176	(5)	(5)	Common Stock	7,893	$0.00	0	I	See footnote(4)

1. Name and Address of Reporting Person* MPM BIOVENTURES 2018, L.P. (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* MPM BIOVENTURES 2018 (B), L.P. (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* MPM ASSET MANAGEMENT INVESTORS BV2018 LLC (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* MPM BioVentures 2018 GP LLC (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* MPM BioVentures 2018 LLC (Last) (First) (Middle) 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* EVNIN LUKE (Last) (First) (Middle) C/O MPM CAPITAL 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* Foley Todd (Last) (First) (Middle) C/O MPM CAPITAL 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

1. Name and Address of Reporting Person* GADICKE ANSBERT (Last) (First) (Middle) C/O MPM CAPITAL 450 KENDALL STREET (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)

Explanation of Responses:

1. On September 21, 2020, the Series A Preferred Stock automatically converted into Common Stock on a 3.3169-for-one basis without payment of further consideration upon closing of the initial public offering of the Issuer's common stock. The shares had no expiration date.

2. The shares are held directly by MPM BioVentures 2018, L.P. ("BV 2018"). The general partner of BV 2018 is MPM BioVentures 2018 GP LLC ("BV 2018 GP"). MPM BioVentures 2018 LLC ("BV 2018 LLC") is the managing member of BV 2018 GP. Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley are the Managing Directors of BV 2018 LLC. Each of BV 2018 GP, BV 2018 LLC, Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley disclaims Section 16 beneficial ownership of the securities held by BV 2018, except to the extent of its pecuniary interest therein, if any.

3. The shares are held directly by MPM BioVentures 2018 (B), L.P. ("BV 2018(B)"). The general partner of BV 2018(B) is BV 2018 GP. BV 2018 LLC is the managing member of BV 2018 GP. Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley are the Managing Directors of BV 2018 LLC. Each of BV 2018 GP, BV 2018 LLC, Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley disclaims Section 16 beneficial ownership of the securities held by BV 2018(B), except to the extent of its pecuniary interest therein, if any.

4. The shares are held directly by MPM Asset Management Investors BV2018 LLC ("MPM Asset Management"). The manager of MPM Asset Management is BV 2018 LLC. Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley are the Managing Directors of BV2018 LLC. Each of BV 2018 LLC, Edward Hurwitz, Luke Evnin, Ansbert Gadicke, and Todd Foley disclaims Section 16 beneficial ownership of the securities held by MPM Asset Management, except to the extent of his pecuniary interest therein, if any.

5. On September 21, 2020, the Series B Preferred Stock automatically converted into Common Stock on a 3.3169-for-one basis without payment of further consideration upon closing of the initial public offering of the Issuer's common stock. The shares had no expiration date.

Remarks:

	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC, the general partner of MPM BioVentures 2018, L.P.	09/23/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC, the general partner of MPM BioVentures 2018 (B), L.P.	09/23/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the manager of MPM Asset Management Investors BV2018 LLC	09/23/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC	09/23/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC	09/23/2020
	/s/ Luke Evnin	09/23/2020
	/s/ Todd Foley	09/23/2020
	/s/ Ansbert Gadicke	09/23/2020
	** Signature of Reporting Person	Date
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