KNOW ALL PERSONS BY THESE PRESENTS that the undersigned hereby
constitutes, designates and appoints Janelle D'Alvise, Francois Paradis, Matthew
Oliver and Jason Comerford as such person's true and lawful attorneys-in-fact
and agents, each with full power of substitution and resubstitution and full
power to act alone and without the other, for the undersigned and in the
undersigned's name, place and stead, in any and all capacities, to:

   (a)  prepare, execute in the undersigned's name and on the undersigned's
behalf, and submit to the U.S. Securities and Exchange Commission (the "SEC") a
Form ID (or any successor form), including amendments thereto, and any other
documents necessary or appropriate to obtain codes and passwords enabling the
undersigned to make electronic filings with the SEC of reports required by
Section 16(a) or any rule or regulation of the SEC promulgated thereunder;

   (b)  execute for and on behalf of the undersigned, in the undersigned's
capacity as an officer and/or director of Acasti Pharma Inc. (the "Company"),
Forms 3, 4, and 5 in accordance with Section 16(a) of the Securities Exchange
Act of 1934 and the rules thereunder (or any successor forms);

   (c)  do and perform any and all acts for and on behalf of the undersigned
which may be necessary or desirable to complete and execute any such Form 3, 4,
or 5, complete and execute any amendment or amendments thereto, and timely file
such form with the SEC and any stock exchange or similar authority; and

   (d)  take any other action of any type whatsoever in connection with the
foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,
in the best interest of, or legally required by, the undersigned, it being
understood that the documents executed by such attorney-in-fact on behalf of the
undersigned pursuant to this Power of Attorney shall be in such form and shall
contain such terms and conditions as such attorney-in-fact may approve in such
attorney-in-fact's discretion.

        The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perform any and every act and thing whatsoever
requisite, necessary, or proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes, shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact, except that in respect of any person herein
appointed as an attorney-in-fact of the undersigned, this Power of Attorney
shall be revoked and shall cease to be effective immediately with respect to
such person at such time as such person shall no longer be employed by any of
the Company and its subsidiaries.

                            [Signature Page Follows]

        IN WITNESS WHEREOF, the undersigned has executed this instrument as of
the 30th day of March, 2022.

Name: Michael L. Derby                        /s/ Michael L. Derby