DMTX Dimension Therapeutics, Inc.

The Offer and withdrawal rights expired as scheduled at 12:00 midnight, New York City time, at the end of the day on November 6, 2017 (such date and time, the “ Expiration Time ”). American Stock Transfer & Trust Company, LLC, the depositary, advised that, as of the Expiration Time, 21,947,871 Shares had been validly tendered and not properly withdrawn pursuant to the Offer, representing approximately 86.5% of the aggregate number of then issued and outstanding Shares. Because the Shares validly tendered and not validly withdrawn constituted a majority of the outstanding Shares entitled to vote, the minimum tender condition for the Offer was satisfied. All other conditions to the Offer were also satisfied as of the expiration of the Offer. As a result, Purchaser has accepted for payment all Shares that were validly tendered and not properly withdrawn pursuant to the Offer.

On November 7, 2017, pursuant to the terms of the Merger Agreement and in accordance with Section 251(h) of the Delaware General Corporation Law (“ DGCL ”), Purchaser was merged with and into the Company, with the Company being the surviving corporation (the “ Merger ”). Upon completion of the Merger, the Company became a wholly-owned subsidiary of Ultragenyx.

At the effective time of the Merger (the “ Effective Time ”), as a result of the Merger, and pursuant to the terms and subject to the conditions of the Merger Agreement, each Share issued and outstanding immediately prior to the Effective Time was converted into the right to receive the Offer Price, in cash, without interest thereon and subject to any required tax withholding, other than (i) Shares held by the Company as treasury stock, or by Ultragenyx or Purchaser or (ii) Shares held by stockholders who properly exercised appraisal rights under the DGCL.

The effect of the Merger on Company stock options and other equity-based awards is described on pages 4-5 of the Company’s Solicitation/Recommendation Statement on Schedule 14D-9 filed with the SEC on October 2, 2017, as amended on October 11, 2017, October 12, 2017, October 17, 2017, October 23, 2017, October 26, 2017 and October 27, 2017, which description is incorporated herein by reference.

Upon the closing of the Merger, Ultragenyx paid the aggregate consideration of approximately $152.3 million, not including related transaction fees and expenses. Ultragenyx provided Purchaser with the funds necessary to complete the Offer and Merger in accordance with the Merger Agreement. Ultragenyx funded these payments with available cash on hand.

The foregoing summary description of the Merger Agreement does not purport to be complete and is qualified in its entirety by reference to the terms of the Merger Agreement, which is included as Exhibit 2.1 to this Current Report on Form 8-K and is incorporated herein by reference.