Exhibit 3.1

AMENDMENT NO. 1 TO

AMENDED AND RESTATED

BYLAWS

OF

EXPRESS SCRIPTS HOLDING COMPANY

Effective March 7, 2018, Express Scripts Holding Company amended its Amended and Restated Bylaws inserting the following as Section 6.11 thereof:

Section 6.11. Forum for Adjudication of Certain Disputes. Unless the corporation consents in writing to the selection of an alternative forum (an “Alternative Forum Consent”), the Delaware Court of Chancery shall be the sole and exclusive forum for (i) any derivative action or proceeding brought on behalf of the corporation, (ii) any action asserting a claim of breach of a fiduciary duty owed by any director, officer, stockholder, employee or agent of the corporation to the corporation or the corporation’s stockholders, including a claim alleging the aiding and abetting of such a breach of fiduciary duty, (iii) any action asserting a claim against the corporation or any current or former director, officer, stockholder, employee or agent of the corporation arising out of or relating to any provision of the General Corporation Law of Delaware or the corporation’s Certificate of Incorporation or Bylaws, (iv) any action asserting a claim related to or involving the corporation or any director, officer, stockholder, employee or agent of the corporation that is governed by the internal affairs doctrine of the State of Delaware, or (v) any action asserting an “internal corporate claim” as that term is defined in Section 115 of the General Corporation Law of the State of Delaware; provided, however, that, in the event that the Delaware Court of Chancery lacks subject matter jurisdiction over any such action or proceeding, the sole and exclusive forum for such action or proceeding shall be another state or federal court located within the State of Delaware. Failure to enforce the foregoing provisions would cause the corporation irreparable harm and the corporation shall be entitled to equitable relief, including injunctive relief and specific performance, to enforce the foregoing provisions. Any person or entity purchasing or otherwise acquiring any interest in shares of capital stock of the Corporation shall be deemed to have notice of and consented to the provisions of this Section 6.11. If any action the subject matter of which is within the scope of this Section 6.11 is filed in a court other than the Delaware Court of Chancery (or any other state or federal court located within the State of Delaware, as applicable) (a “Foreign Action”) by or in the name of any stockholder, such stockholder shall be deemed to have consented to (i) the personal jurisdiction of the Delaware Court of Chancery (or such other state or federal court located within the State of Delaware, as applicable) in connection with any action brought in any such court to enforce this Section 6.11 and (ii) having service of process made upon such stockholder in any such action by service upon such stockholder’s counsel in the Foreign Action as agent for such stockholder. The existence of any prior Alternative Forum Consent shall not act as a waiver of the corporation’s ongoing consent right as set forth above in this Section 6.11 with respect to any current or future actions or claims.