Exhibit 10.1

FIFTH AMENDMENT OF

THE RESEARCH AND COMMERCIAL LICENSE OPTION AGREEMENT

This F IFTH A MENDMENT OF THE R ESEARCH AND C OMMERCIAL L ICENSE O PTION A GREEMENT (this “ Fifth Amendment ”) is made and effective as of May 14, 2010 (the “ Fifth Amendment Effective Date ”) by and between S ANGAMO B IO S CIENCES , I NC ., a Delaware corporation having its principal place of business at Point Richmond Tech Center, 501 Canal Boulevard, Suite A100, Richmond, California 94804 (“ Sangamo ”), and D OW A GRO S CIENCES LLC , a Delaware limited liability company having its principal place of business at 9330 Zionsville Road, Indianapolis, Indiana 46268 (“ DAS ”) (each of Sangamo and DAS being a “ Party ,” and collectively, the “ Parties ”).

WHEREAS, Sangamo and DAS are parties to certain Research and Commercial License Option Agreement, dated as of October 1, 2005 (as previously amended, the “ Agreement ”);

WHEREAS, on or about June 18, 2008, DAS exercised the Option; and

WHEREAS, Sangamo and DAS now desire to amend the Agreement in accordance with Section 14.4 as set forth below.

NOW THEREFORE, in consideration of the mutual promises and agreements set forth herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties agree as follows:

Section 1.65 shall be amended to read in its entirety as follows:

“1.65 ‘Sublicensing Revenues’ means any cash consideration that DAS receives from a Sublicensee in connection with a Technology License, which may include (without limitation) upfront license fees, annual license or maintenance payments, milestone payments, royalties, credits against DAS’ future expenses, or reductions in royalties or other payments otherwise owed to the Sublicensee. Sublicensing Revenue also includes all cash consideration received by DAS (a) in connection with any research license it grants pursuant to Section 2.1(a)(ii), (b) in connection with the grant of an option to obtain a research license or Technology License, and (c) for the sale of ZFP Products to Sublicensees, to the extent that such consideration exceeds DAS’ cost for such ZFP Products. Sublicensing Revenue does not include the value of non-cash consideration received by DAS, the Parties having expressly agreed that DAS is not obligated to account to Sangamo for such consideration.”

“ (b) Additional Grants to DAS Effective after Exercise of Option. Subject to the terms and conditions of this Agreement, Sangamo hereby grants to DAS and its Affiliates, effective upon DAS’s exercise of the Option (which exercise shall include timely provision of the Option Exercise Notice and timely

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CONFIDENTIAL

payment of the fee set forth in Section 8.6), the following additional licenses and rights under Sangamo Technology:

(i) a royalty bearing, world-wide, exclusive license to make, use, and import ZFP Products for use in the Field, which DAS shall exercise for the sole purposes of

(1) generating DAS Products; or

(2) offering for sale and selling ZFP Products to Sublicensees for use in the Field for the sole purpose of generating Licensed Products;

provided, however, that with respect to the Manufacture of ZFP Products for use in the Field, such license is co-exclusive with Sangamo and any Contract Manufacturer selected by Sangamo to fulfill some or all of Sangamo’s obligations under Section 7.1, DAS shall not exercise such license until Sangamo has transferred its Manufacturing technology to DAS pursuant to Section 7.2, and Sangamo shall only use its coexclusive rights in the Field with respect to Manufacture of ZFP Products to fulfill its obligations under Section 7.1; and

(ii) a royalty bearing, world-wide, exclusive license to make, use, sell, offer for sale, and import DAS Products.”

“ (c) Sublicensing . DAS shall not have the right to sublicense its right to grant research licenses and Technology Licenses under Section 2.1(a) and shall have the right to sublicense its rights under Section 2.1(b)(i)only to a Contract Manufacturer selected by DAS and approved by Sangamo for the sole purpose of Manufacturing ZFP Products in accordance with the terms of this Agreement. Without the prior written consent of Sangamo, such Contract Manufacturer shall not have the right to sell the ZFP Products Manufactured pursuant to such sublicense to any person or entity other than DAS or a Sublicensee, and the cost to Sublicensee for any ZFP Product supplied to it by such Contract Manufacturer must be no greater than the cost to DAS for similar ZFP Products supplied to DAS by such Contract Manufacturer. The license set forth in Section 2.1(b)(ii) shall be freely sublicensable. Sublicensees may be given the right to further sublicense Licensed Products that they develop under Technology Licenses, and Sublicensees may be given the right to license Third Parties to make, use, offer to sell, sell, or import products containing ZFP Traits that the Sublicensees develop under Technology Licenses (i.e., license their Traits), provided that licenses do not grant any sublicenses under or rights with respect to Sangamo Technology.”

“ 5.4 Research Licenses . DAS shall ensure that all research licenses granted pursuant to Section 2.1(a)(ii) comply with the following requirements:

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(a) the Sublicensee will not transfer any ZFP Product to any other person or entity without prior written approval of DAS and without such other person or entity entering into a material transfer agreement with DAS that contains substantially similar terms to those in the research license with such Sublicensee (and such mat