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SEC FORM 3 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*
Booth Bruce
(Last) (First) (Middle)
C/O MAGENTA THERAPEUTICS, INC
50 HAMPSHIRE STREET
(Street)
CAMBRIDGE MA 02139
(City) (State) (Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
06/20/2018 		3. Issuer Name and Ticker or Trading Symbol
Magenta Therapeutics, Inc. [ MGTA ]
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director 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)
Common Stock 96,749 I See Footnote(3)
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 4,667,797 (1) I See Footnote(3)
Series B Preferred Stock (2) (2) Common Stock 79,079 (2) I See Footnote(3)
Explanation of Responses:
1. Each share of Series A Preferred Stock is convertible into shares of the Issuer's common stock, $0.001 par value per share ("Common Stock") on a 2.58398:1 basis. Upon the closing of the Issuer's initial public offering, all shares of Series A Preferred Stock will convert into shares of Common Stock of the Issuer. The Series A Preferred Stock has no expiration date.
2. Each share of Series B Preferred Stock is convertible into shares of the Issuer's Common Stock on a 2.58398:1 basis. Upon the closing of the Issuer's initial public offering, all shares of Series B Preferred Stock will convert into shares of Common Stock of the Issuer. The Series B Preferred Stock has no expiration date.
3. The shares are held directly by Atlas Venture Fund X, L.P. ("Atlas Venture Fund X"). The general partner of Atlas Venture Fund X is Atlas Venture Associates X, L.P. ("AVA X LP"). Atlas Venture Associates X, LLC ("AVA X LLC") is the general partner of AVA X LP. Dr. Booth is a member of AVA X LLC and disclaims beneficial ownership of such securities held by Atlas Venture Fund X, except to the extent of his pecuniary interest therein, if any.
Remarks:
Exhibit 24.1: Power of Attorney
/s/ Ommer Chohan, Attorney-in-Fact for Bruce Booth 06/20/2018
** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
                                 POWER OF ATTORNEY

        Know all by these presents that the undersigned hereby constitutes and
appoints Ommer Chohan with full power of substitution, the undersigned's true
and lawful attorney-in-fact to:

        (1)   prepare, execute in the undersigned's name and on the
              undersigned's behalf, and submit to the U.S. Securities and
              Exchange Commission (the "SEC") a Form ID, including amendments
              thereto, and any other documents necessary or appropriate to
              obtain codes and passwords enabling the undersigned to make
              electronic filings with the SEC of reports required by Section
              16(a) of the Securities Exchange Act of 1934 or any rule or
              regulation of the SEC;

        (2)   execute for and on behalf of the undersigned, in the undersigned's
              capacity as an officer and/or director of Magenta Therapeutics,
              Inc. (the "Company"), Forms 3, 4, and 5 in accordance with Section
              16(a) of the Securities Exchange Act of 1934 and the rules
              thereunder;

        (3)   do and perform any and all acts for and on behalf of the
              undersigned which may be necessary or desirable to complete and
              execute any such Form 3, 4, or 5, complete and execute any
              amendment or amendments thereto, and timely file such form with
              the SEC and any stock exchange or similar authority; and

        (4)   take any other action of any type whatsoever in connection with
              the foregoing which, in the opinion of such attorney-in-fact, may
              be of benefit to, in the best interest of, or legally required by,
              the undersigned, it being understood that the documents executed
              by such attorney-in-fact on behalf of the undersigned pursuant to
              this Power of Attorney shall be in such form and shall contain
              such terms and conditions as such attorney-in-fact may approve in
              such attorney-in-fact's discretion.

        The undersigned hereby grants to such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this power of attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in- fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of June 14, 2018.

                                        /s/ Bruce Booth
                                        -------------------------------
                                                  Signature

                                                            Bruce Booth
                                        -------------------------------
                                                     Name