On April 3, 2017, James Topper notified Sierra Oncology, Inc. of his decision to resign from the Board of Directors of the company and the Nominating and Corporate Governance Committee (the Nominating Committee), effective April 10, 2017. In connection with Dr. Topper's resignation, the Board appointed Donald Parfet as the interim Chair of the Nominating Committee, effective April 10, 2017. Dr. Topper's decision was not the result of any disagreement with the company. On April 3, 2017, the board appointed Daniel Estes to the board as a Class II director, effective April 10, 2017. There is no arrangement or understanding with any person pursuant to which Dr. Estes was appointed as a member of the board.