Sec Form 3 Filing - Zone Healthcare Holdings, LLC @ Generation Bio Co. - 2020-06-11

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Zone Healthcare Holdings, LLC 2. Issuer Name and Ticker or Trading Symbol Generation Bio Co. [ GBIO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) X __ Other (specify below) Member of Group Owning 10% (Last) (First) (Middle) C/O FARALLON CAPITAL MANAGEMENT, L.L.C., ONE MARITIME PLAZA, SUITE 2100 3. Date of Earliest Transaction (MM/DD/YY) 06/11/2020 (Street) SAN FRANCISCO, CA94111 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 C Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,518,819 D ( 2 ) ( 3 ) ( 4 ) Series C Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,518,819 I See Footnotes ( 2 ) ( 3 ) ( 4 ) ( 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Zone Healthcare Holdings, LLC C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Member of Group Owning 10% FARALLON CAPITAL MANAGEMENT LLC ONE MARITIME PLAZA SUITE 2100 SAN FRANCISCO, CA94111 X Manager of ZHH LLC FARALLON PARTNERS L L C/CA ONE MARITIME PLAZA SUITE 2100 SAN FRANCISCO, CA94111 X Farallon General Partner Dreyfuss Philip D C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member Fisch Michael B. C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member FRIED RICHARD B C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member Kim David T C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member Linn Michael G C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member PATEL RAJIV A C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member Roberts Thomas G. Jr. C/O FARALLON CAPITAL MANAGEMENT, L.L.C. ONE MARITIME PLAZA, SUITE 2100 SAN FRANCISCO, CA94111 X Managing Member Signatures /s/ Michael B. Fisch, as an authorized signatory for Zone Healthcare Holdings, LLC 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as a managing member of Farallon Capital Management, L.L.C. 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as a managing member of Farallon Partners, L.L.C. 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for Philip D. Dreyfuss 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for Richard B. Fried 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for David T. Kim 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for Michael G. Linn 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for Rajiv A. Patel 06/11/2020 Signature of Reporting Person Date /s/ Michael B. Fisch, as attorney-in-fact for Thomas G. Roberts, Jr. 06/11/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of Series C Preferred Stock of Generation Bio Co. (the "Issuer") are convertible into shares of Common Stock of the Issuer on a 1.7663-for-one basis without payment of further consideration; are convertible by the holder at any time at the holder's election and convert automatically upon the closing of a qualified public offering by the Issuer; and have no expiration date. ( 2 )The entities and individuals identified in the footnotes of this Form 3 may be deemed members of a group holding equity securities of the Issuer. The filing of this Form 3 and any statements included herein shall not be deemed to be an admission that such entities and individuals are members of such a group. ( 3 )Since the number of reporting persons that may be listed on a Form 3 is limited, the entities and individuals identified as reporting persons in these footnotes that are not reporting persons on this Form 3 are filing one or more additional Forms 3 on the date hereof as reporting persons with respect to the securities described herein (each, a "Parallel Form 3"). Information regarding these entities and individuals is included in this Form 3 for purposes of clarification and convenience only, and is duplicative of the information reported in any Parallel Form 3. ( 4 )The amount of securities shown in this row is owned directly by Zone Healthcare Holdings, LLC ("ZHH LLC"). ( 5 )Farallon Capital Management, L.L.C. (the "Management Company"), as the manager of ZHH LLC, may be deemed to be a beneficial owner of the Issuer's securities held by ZHH LLC. The Management Company disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (the "'34 Act"), or otherwise, except to the extent of its pecuniary interest, if any. ( 6 )The members of ZHH LLC are FCP SS 2019, LLC ("FCP SS"), FCIP SS 2019, LLC ("FCIP SS"), FCOI II SS 2019, Ltd. ("FCOI II SS"), Farallon Capital Institutional Partners, II, L.P. ("FCIP II"), Farallon Capital Institutional Partners III, L.P. ("FCIP III"), Four Crossings Institutional Partners V, L.P. ("FCIP V"), Farallon Special Situation Partners VI, L.P. ("FSSP VI") and Farallon Special Situations Fund, L.P. ("FSSF"). Each such member of ZHH LLC disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the '34 Act or otherwise. ( 7 )The sole member of FC P SS is Farallon Capital Partners, L.P. ("FCP"). The sole member of FCIP SS is Farallon Capital Institutional Partners, L.P. ("FCIP"). The sole member of FCOI II SS is Farallon Capital Offshore Investors II, L.P. ("FCOI II"). Each of FCP, FCIP and FCOI II disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the '34 Act or otherwise. ( 8 )Farallon Partners, L.L.C. (the "Farallon General Partner"), as the general partner of each of FCP, FCIP, FCIP II, FCIP III and FCOI II, the sole member of the respective general partners of FCIP V and FSSP VI and the sole member of the director of FCOI II SS, may be deemed to be a beneficial owner of the Issuer's securities held indirectly by each of FCP, FCIP, FCIP II, FCIP III , FCOI II, FCIP V and FSSP VI. The Farallon General Partner disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the '34 Act, or otherwise, except to the extent of its pecuniary interest, if any. ( 9 )Each of Philip D. Dreyfuss, Michael B. Fisch, Richard B. Fried, David T. Kim, Michael G. Linn, Rajiv A. Patel, Thomas G. Roberts, Jr., William Seybold, Andrew J. M. Spokes, John R. Warren, and Mark C. Wehrly (collectively, the "Managing Members"), as a managing member or senior managing member, as the case may be, of the Management Company and the Farallon General Partner, and a manager or senior manager, as the case may be, of the respective general partners of FCIP V, FSSP VI and FSSF, in each case with the power to exercise investment discretion, may be deemed to be a beneficial owner of the Issuer's securities held by ZHH LLC. Each of the Managing Members disclaims any beneficial ownership of any of the Issuer's securities reported or noted herein for purposes of Section 16 of the '34 Act or otherwise, except to the extent of his pecuniary interest, if any.

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