Rishi Gupta Form 3 Dimension Therapeutics / Rishi Gupta ownership change

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^*

Gupta Rishi

(Last) (First) (Middle)

C/O DIMENSION THERAPEUTICS, INC.

840 MEMORIAL DRIVE, 4TH FLOOR

(Street)

CAMBRIDGE MA 02139

(City) (State) (Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
10/21/2015

3. Issuer Name and Ticker or Trading Symbol
Dimension Therapeutics, Inc. [ DMTX ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	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)

X	Form filed by One Reporting Person
	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	3,250,085(1)	(1)	I	See Footnotes(3)(4)
Series B Preferred Stock	(2)	(2)	Common Stock	1,947,613(2)	(2)	I	See Footnotes(3)(4)

Explanation of Responses:

1. These securities are shares of Series A Preferred Stock (the "Series A Shares") of the Issuer, and are convertible at any time into shares of the Issuer's Common Stock at the holders' election and automatically upon the closing of the Issuer's initial public offering, into the number of shares of Common Stock shown in column 3 above.

2. These securities are shares of Series B Preferred Stock (the "Series B Shares") of the Issuer, and are convertible at any time into shares of the Issuer's Common Stock at the holders' election and automatically upon the closing of the Issuer's initial public offering, into the number of shares of Common Stock shown in column 3 above.

3. These securities are held of record by OrbiMed Private Investments V, LP ("OPI V"). OrbiMed Capital GP V LLC ("GP V") is the sole general partner of OPI V. OrbiMed Advisors LLC ("Advisors") is the managing member of GP V. Samuel D. Isaly ("Isaly"), a natural person, is the managing member of and owner of a controlling interest in Advisors. By virtue of such relationships, GP V, Advisors and Isaly may be deemed to have voting and investment power over the securities held by OPI V and as a result may be deemed to have beneficial ownership over such securities. The Reporting Person is an employee of Advisors.

4. Each of GP V, Advisors, Isaly, and the Reporting Person disclaims beneficial ownership of the securities reported herein for purposes of Rule16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its or his pecuniary interest therein, if any. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

Remarks:

[Exhibit 24.1: Limited Power of Attorney]

	/s/ Mary Thistle, as Attorney-in-Fact for Rishi Gupta	10/21/2015
	** Signature of Reporting Person	Date
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 5 (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).
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