UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.     )

Filed by the Registrant  ☒                             Filed by a Party other than the Registrant  ☐

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☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting Material Pursuant to §240.14a-12

SANGAMO THERAPEUTICS, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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☐ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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BARCODE See the reverse side of this notice to obtain proxy materials and voting instructions. BROKER LOGO HERE 1 OF 2 12 15 1234567 1234567 1234567 1234567 1234567 1234567 1234567 Broadridge Internal Use Only Job # Envelope # Sequence # # of # Sequence # *** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Shareholder Meeting to Be Held on <mtgdate>. You are receiving this communication because you hold shares in the above named company. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. Meeting Information Meeting Type: <mtgtype> For holders as of: <recdate> Date: Time: <mtgtime> Location: 0000336381_1 R1.0.1.15 SANGAMO THERAPEUTICS, INC. Annual Meeting June 05, 2017 June 05, 2017 9:00 AM PDT April 17, 2017 Sangamo Therapeutics, Inc. 501 Canal Boulevard Richmond, CA 94804 Return Address Line 1 Return Address Line 2 Return Address Line 3 51 MERCEDES WAY EDGEWOOD NY 11717 Investor Address Line 1 Investor Address Line 2 Investor Address Line 3 Investor Address Line 4 Investor Address Line 5 John Sample 1234 ANYWHERE STREET ANY CITY, ON A1A 1A1

How To Vote Please Choose One of the Following Voting Methods Internal Use Only Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: How to View Online: Have the information that is printed in the box marked by the arrow (located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow (located on the following page) in the subject line. g g Vote In Person: If you choose to vote these shares in person at the meeting, you must request a "legal proxy." To do so, please follow the instructions at www.proxyvote.com or request a paper copy of the materials, which will contain the appropriate instructions. Many shareholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a voting instruction form. g 0000336381_2 R1.0.1.15 1. Form 10-K 2. Notice & Proxy Statement Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 22, 2017 to facilitate timely delivery.

BARCODE 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 123456789012 Broadridge Internal Use Only xxxxxxxxxx xxxxxxxxxx Cusip Job # Envelope # Sequence # # of # Sequence # Voting items 0000336381_3 R1.0.1.15 The Board of Directors recommends you vote FOR the following proposal(s): 1. Election of Directors Nominees 1A H. Stewart Parker 1B Robert F. Carey 1C Stephen G. Dilly* 1D Alexander D. Macrae** 1E Steven J. Mento, Ph.D. 1F Saira Ramasastry 1G William R. Ringo The Board of Directors recommends you vote FOR the following proposal(s): 2. To approve, on an advisory basis, the compensation of the Company's named executive officers, as described in the Proxy Statement. The Board of Directors recommends you vote 1 YEAR on the following proposal: 3. To approve, on an advisory basis, whether the advisory stockholder vote to approve the compensation of the Company's named executive officers should occur every year, once every two years or once every three years. The Board of Directors recommends you vote FOR the following proposal(s): 4. To ratify the appointment of Ernst & Young LLP as the Company's independent registered public accounting firm for the year ending December 31, 2017. 0000 0000 0000 0000

THIS SPACE RESERVED FOR LANGUAGE PERTAINING TO BANKS AND BROKERS AS REQUIRED BY THE NEW YORK STOCK EXCHANGE Voting Instructions THIS SPACE RESERVED FOR SIGNATURES IF APPLICABLE P99999-010 12 15 # OF # Broadridge Internal Use Only Job # Envelope # Sequence # # of # Sequence # Reserved for Broadridge Internal Control Information Voting items Continued 0000336381_4 R1.0.1.15 NOTE: Such other business as may properly come before the meeting or any adjournment thereof. *Stephen G. Dilly, M.B.B.S., Ph.D. **Alexander "Sandy" Macrae, M.B., Ch.B., Ph.D.