Exhibit 4.3

ADVANCE NOTICE BY-LAW

BY-LAW NO. 2013-1

A BY-LAW RELATING GENERALLY TO THE ADVANCE

NOTICE REQUIREMENTS FOR THE NOMINATION OF

DIRECTORS OF ACASTI PHARMA INC.

(the “Corporation”)

INTRODUCTION

The purpose of this advance notice by-law (the “Advance Notice By-Law”) is to establish the conditions and framework under which holders of record of common shares of the Corporation may exercise their right to submit director nominations by fixing a deadline by which such nominations must be submitted by a shareholder to the Corporation prior to any annual or special meeting of shareholders, and sets forth the information that a shareholder must include in the notice to the Corporation for the notice to be in proper form.

It is the position of the Corporation that this Advance Notice By-Law is beneficial to shareholders and other stakeholders of the Corporation.

NOMINATIONS OF DIRECTORS

a. by or at the direction of the Board, including pursuant to a notice of meeting;

b. by or at the direction or request of one or more shareholders of the Corporation pursuant to a proposal made in accordance with the provisions of the Act, or a requisition of meeting of the shareholders of the Corporation made in accordance with the provisions of the Act; or

c. by any person (a “Nominating Shareholder”): (A) who, at the close of business on the date of the giving of the notice provided below in this Advance Notice By-Law and on the record date for notice of such meeting, is entered in the securities register of the Corporation as a holder of one or more shares carrying the right to vote at such meeting or who beneficially owns shares that are entitled to be voted at such meeting; and (B) who complies with the notice procedures set forth below in this Advance Notice By-Law.

a. in the case of an annual meeting of shareholders, not less than 30 nor more than 65 days prior to the date of the annual meeting of shareholders; provided, however, that in the event that the annual meeting of shareholders is to be held on a date that is less than 50 days after the date on which the first public announcement (the “Notice Date”) of the date of the annual meeting was made, notice by the Nominating Shareholder may be made not later than the close of business on the 10th day following the Notice Date; and

b. in the case of a special meeting (which is not also an annual meeting) of shareholders called for the purpose of electing directors (whether or not called for other purposes), not later than the close of business on the 15th day following the day on which the first public announcement of the date of the special meeting of shareholders was made.

c. In no event shall any adjournment or postponement of a meeting of shareholders or the announcement thereof commence a new time period for the giving of a Nominating Shareholder’s notice as described above.

a. as to each person whom the Nominating Shareholder proposes to nominate for election as a director: (A) the name, age, business address and residential address of the person; (B) the principal occupation or employment of the person; (C) the class or series and number of shares in

the capital of the Corporation which are controlled or which are owned beneficially or of record by the person as of the record date for the meeting of shareholders (if such date shall then have been made publicly available and shall have occurred) and as of the date of such notice; and (D) any other information relating to the person that would be required to be disclosed in a dissident’s proxy circular in connection with solicitations of proxies for election of directors pursuant to the Act and Applicable Securities Laws (as defined below); and

b. as to the Nominating Shareholder giving the notice, any proxy, contract, arrangement, understanding or relationship pursuant to which such Nominating Shareholder has a right to vote any shares of the Corporation and any other information relating to such Nominating Shareholder that would be required to be made in a dissident’s proxy circular in connection with solicitations of proxies for election of directors pursuant to the Act and Applicable Securities Laws (as defined below).

The Corporation may require any proposed director nominee to furnish such other information as may reasonably be required by the Corporation to determine the eligibility of such proposed director nominee to serve as an independent director of the Corporation or that could be material to a reasonable shareholder of the Corporation’s understanding of the independence, or lack thereof, of such proposed director nominee.

a. “public announcement” shall mean disclosure in a press release reported by a national news service in Canada, or in a document publicly filed by the Corporation under its profile on the System of Electronic Document Analysis and Retrieval at www.sedar.com; and

b. “Applicable Securities Laws” means the applicable securities legislation of each relevant province of Canada, as amended from time to time, the rules, regulations and forms made or promulgated under any such statute and the published national instruments, multilateral instruments, policies, bulletins and notices of the securities commission and similar regulatory authority of each province of Canada.

Notwithstanding the foregoing, the Board may, in its sole discretion, waive any requirement in this Advance Notice By-Law.

Adopted by the Board May 9, 2013.

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