FIRST AMENDMENT TO AGREEMENT AND PLANOF MERGER

Exhibit 10.1

FIRST AMENDMENT TO AGREEMENT AND PLAN OF MERGER

This FIRST AMENDMENT TO AGREEMENT AND PLAN OF MERGER (this “Amendment”), dated as of January 29, 2014, is by and among Intrexon Corporation, a Virginia corporation (“Parent”), XON Cells, Inc., a Nevada corporation and a wholly owned subsidiary of Parent (“Merger Sub”), and Medistem Inc., a Nevada corporation (the “Company”).

WHEREAS, Parent, Merger Sub and the Company are parties to that Agreement and Plan of Merger, dated as of December 19, 2013 (the “Agreement”);

WHEREAS, Parent, Merger Sub and the Company desire to amend the Agreement on the terms and conditions set forth herein;

WHEREAS, Section 7.3 of the Agreement provides that: (i) the Agreement may be amended by the parties by action taken by or on behalf of their respective Boards of Directors at any time prior to the Closing Date; provided, however, that, after approval of the Merger by the stockholders of the Company, no amendment may be made that, by Law or in accordance with the rules of any relevant stock exchange, requires further approval by such stockholders; and (ii) the Agreement may not be amended except by an instrument in writing signed by the parties hereto; and

WHEREAS, the respective Boards of Directors of the parties to the Agreement have approved this Amendment prior to the approval of the Merger by the stockholders of the Company.

NOW, THEREFORE, in consideration of the foregoing and the respective representations, warranties, covenants and agreements set forth below and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto, intending to be legally bound, do hereby agree as follows:

“Section 5.17. If, prior to the Closing, there are any Company Stockholders who have properly exercised and preserved dissenters’ rights and such exercise has not been withdrawn or otherwise satisfied immediately prior to the Effective Time, then, immediately following the Effective Time of the Merger, Parent shall cause the Surviving Corporation to merge, in accordance with applicable Law, with and into a limited liability company and wholly owned subsidiary of Parent (“Second Merger Sub”), with Second Merger Sub surviving such merger (the “Subsequent Merger”). For these purposes, the parties hereby confirm that it is intended that the Merger and the Subsequent Merger constitute an integrated plan of the type contemplated in IRS Revenue Ruling 2001-46, 2001-2 C.B. 321 (the “Integrated Transaction”) and that in the event that the Integrated Transaction is to qualify as a “reorganization” within the

meaning of Section 368(a) of the Code, and the regulations promulgated thereunder, then the parties intend for this Agreement to constitute a plan of reorganization within the meaning of Section 368(a) of the Code for U.S. federal income Tax purposes. The parties further acknowledge and agree that in no way shall such restructuring result in any change in the Cash Consideration, the Stock Consideration, the Merger Consideration or in the economics or other material terms of the transactions contemplated by this Agreement to the Company or its stockholders, or Parent, Merger Sub or their shareholders and stockholders, respectively.”

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IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the date first written above by their respective officers thereunto duly authorized.