SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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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. Date of Event Requiring Statement (Month/Day/Year) 09/16/2020	3. Issuer Name and Ticker or Trading Symbol Dyne Therapeutics, Inc. [ DYN ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. 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 Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A Preferred Stock	(1)	(1)	Common Stock	4,215,076	(1)	I	See footnote(2)
Series A Preferred Stock	(1)	(1)	Common Stock	224,025	(1)	I	See footnote(3)
Series A Preferred Stock	(1)	(1)	Common Stock	83,188	(1)	I	See footnote(4)
Series B Preferred Stock	(5)	(5)	Common Stock	399,867	(5)	I	See footnote(2)
Series B Preferred Stock	(5)	(5)	Common Stock	21,254	(5)	I	See footnote(3)
Series B Preferred Stock	(5)	(5)	Common Stock	7,893	(5)	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. The Series A Preferred Stock is convertible into common stock on a 3.3169-for-1 basis into the number of shares of common stock shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have 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 BV 2018 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. The Series B Preferred Stock is convertible into common stock on a 3.3169-for-1 basis into the number of shares of common stock shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have 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.	09/16/2020
	/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.	09/16/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the manager of MPM Asset Management Investors BV2018 LLC	09/16/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC, the managing member of MPM BioVentures 2018 GP LLC	09/16/2020
	/s/ Ed Hurwitz, managing director of MPM BioVentures 2018 LLC	09/16/2020
	/s/ Luke Evnin	09/16/2020
	/s/ Todd Foley	09/16/2020
	/s/ Ansbert Gadicke	09/16/2020
	** Signature of Reporting Person	Date
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