Business Combination On September 20, 2016, the Company entered into an agreement with Viventia Bio Inc. , a corporation incorporated under the laws of the Province of Ontario, Canada (Viventia), the shareholders of Viventia named therein (the Selling Shareholders) and, solely in its capacity as seller representative, Clairmark Investments Ltd., a corporation incorporated under the laws of the Province of Ontario, Canada (Clairmark) (the Share Purchase Agreement), pursuant to which the Company agreed to and simultaneously completed the acquisition of all of the outstanding capital stock of Viventia from the Selling Shareholders (the Acquisition). In connection with the closing of the Acquisition, the Company issued 4,013,431 shares of its common stock to the Selling Shareholders, which represented approximately 19.9% of the voting power of the Company as of immediately prior to the issuance of such shares of the Company's common stock. The Selling Shareholders includes Clairmark, an affiliate of one of the Companys directors, and the Companys CEO. In addition, under the Share Purchase Agreement, the Company is obligated to pay to the Selling Shareholders certain post-closing contingent cash payments upon the achievement of specified milestones and based upon net sales, in each case subject to the terms and conditions set forth in the Share Purchase Agreement, including: (i) a one-time milestone payment of $12.5 million payable upon the first sale of Vicinium TM or any variant or derivative thereof, other than Proxinium TM (the Purchased Product), in the United States; (ii) a one-time milestone payment of $7.0 million payable upon the first sale of the Purchased Product in any one of certain specified European countries; (iii) a one-time milestone payment of $3.0 million payable upon the first sale of the Purchased Product in Japan; and (iv) and quarterly earn-out payments equal to two percent ( 2% ) of net sales of the Purchased Product during specified earn-out periods. Such earn-out payments are p