ACHN 2018 Proxy Statement

PROPOSAL 4—RATIFICATION OF SELECTION OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM Our Audit Committee has selected the firm of PricewaterhouseCoopers LLP as our independent registered public accounting firm for the current fiscal year. PricewaterhouseCoopers LLP has served as our independent registered public accounting firm since 2002. Although stockholder approval of the selection of PricewaterhouseCoopers LLP is not required by law, the Board of Directors believes that it is advisable to give stockholders an opportunity to ratify this selection. If this proposal is not approved at our Annual Meeting, our Audit Committee will reconsider its selection of PricewaterhouseCoopers LLP. Representatives of PricewaterhouseCoopers LLP are expected to be present at the Annual Meeting and will have the opportunity to make a statement if they desire to do so and will also be available to respond to appropriate questions from stockholders. Board Recommendation The Board of Directors believes that the selection of PricewaterhouseCoopers LLP as our independent registered public accounting firm is in the best interests of Achillion and the best interests of our stockholders, and therefore, recommends a vote FOR this proposal. 26