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

1. Subject only to the Quebec Business Corporations Act (the “Act”) and the articles, only persons who are nominated in accordance with the following procedures shall be eligible for election as directors of the Corporation. Nominations of persons for election to the board of directors of the Corporation (the “Board”) may be made at any annual meeting of shareholders or at any special meeting of shareholders if one of the purposes for which the special meeting was called was the election of directors. Such nominations may be made in the following manner:

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.

2. In addition to any other applicable requirements, for a nomination to be made by a Nominating Shareholder, the Nominating Shareholder must have given timely notice thereof in proper written form to the Corporate Secretary of the Corporation at the principal executive offices of the Corporation.

3. To be timely, a Nominating Shareholder’s notice to the Corporate Secretary of the Corporation must be made:

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.

4. To be in proper written form, a Nominating Shareholder’s notice to the Corporate Secretary of the Corporation must set forth:

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.

5. No person shall be eligible for election as a director of the Corporation unless nominated in accordance with the provisions of this Advance Notice By-Law; provided, however, that nothing in this Advance Notice By-Law shall be deemed to preclude discussion by a shareholder (as distinct from the nomination of directors) at a meeting of shareholders of the Corporation of any matter in respect of which it would have been entitled to submit a proposal pursuant to the provisions of the Act. The chairman of the meeting shall have the power and duty to determine whether a nomination was made in accordance with the procedures set forth in the foregoing provisions and, if any proposed nomination is not in compliance with such foregoing provisions, to declare that such defective nomination shall be disregarded.

6. For purposes of this Advance Notice By-Law:

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.

7. Notwithstanding any other provision of this Advance Notice By-Law, notice given to the Corporate Secretary of the Corporation may only be given by personal delivery, facsimile transmission or by email (at such email address as stipulated from time to time by the Corporate Secretary of the Corporation for purposes of this notice), and shall be deemed to have been given and made only at the time it is served by personal delivery, email (at the aforesaid address) or sent by facsimile transmission (provided that receipt of confirmation of such transmission has been received) to the Corporate Secretary of the Corporation at the address of the principal executive offices of the Corporation; provided that if such delivery or electronic communication is made on a day which is a not a business day or later than 5:00 p.m. (Montreal time) on a day which is a business day, then such delivery or electronic communication shall be deemed to have been made on the subsequent day that is a business day.

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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