Liminal BioSciences : Supplement to the Arrangement Circular – Special Meeting September 2023

These materials are important and require your immediate attention. If you are a shareholder of Liminal BioSciences Inc. ("Liminal BioSciences" or the "Company") and have any questions regarding the information contained in this Supplement to the Management Information Circular dated August 16, 2023, please contact Carson Proxy Advisors, the Company's proxy solicitor, at North American toll free phone at 1-800-530-5189, local (collect outside North America): 416-751-2066 or by email at info@carsonproxy.com.

Shareholders in the United States should read the section "Notice to Shareholders in the United States" on page 3 of the management information circular dated August 16, 2023, which is available on the Company's corporate website at www.liminalbiosciences.com and under Liminal BioSciences' profiles on SEDAR+ at www.sedarplus.ca and EDGAR at www.sec.gov.

Supplement to the

Management Information Circular dated August 16, 2023

In Respect of an

Arrangement

Involving

Liminal BioSciences Inc.

and

Structured Alpha LP

Dated September 12, 2023

IF YOU HAVE PREVIOUSLY SUBMITTED A PROXY IN CONNECTION WITH THE ARRANGEMENT, SUCH PROXY WILL, UNLESS REVOKED, CONTINUE TO BE VALID AT THE MEETING.

NO SECURITIES REGULATORY AUTHORITY IN ANY PROVINCE OF TERRITORY OF CANADA, AND NEITHER OF THE U.S. SECURITIES AND EXCHANGE COMMISSION, THE NASDAQ CAPITAL MARKET, NOR ANY SECURITIES REGULATORY AUTHORITY IN ANY STATE IN THE UNITED STATES, HAS APPROVED OR DISAPPROVED OF THE TRANSACTION DESCRIBED HEREIN OR PASSED UPON THE FAIRNESS OR MERITS OF SUCH TRANSACTION, NOR HAS ANY SECURITIES REGULATORY AUTHORITY IN ANY PROVINCE OF TERRITORY OF CANADA, THE U.S. SECURITIES AND EXCHANGE COMMISSION, THE NASDAQ CAPITAL MARKET OR ANY SECURITIES REGULATORY AUTHORITIES OF ANY STATE IN THE UNITED STATES PASSED ON THE ADEQUACY OR ACCURACY OF THIS SUPPLEMENT. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENCE.

SUPPLEMENT DATED SEPTEMBER 12, 2023 TO THE MANAGEMENT INFORMATION CIRCULAR DATED AUGUST 16, 2023

This supplement (the "Supplement") modifies and supplements the Management Information Circular (the "Circular") of Liminal BioSciences Inc. ("Liminal BioSciences" or the "Company") dated August 16, 2023 prepared in connection with the special meeting of shareholders of the Company (the "Meeting"). The Circular is available on the Company's corporate website at https://investors.liminalbiosciences.com/shareholder-informationand under Liminal BioSciences' profiles on SEDAR+ at www.sedarplus.caand EDGAR at www.sec.gov. Terms with initial capital letters not otherwise defined in this Supplement have the meanings ascribed thereto in the Circular. This Supplement shall form part of and be deemed to be included in the Circular. To the extent that any statement contained in this Supplement modifies, supplements or amends any statement contained in the Circular, such statement in the Circular shall be deemed to be so modified, supplemented or amended.

General Comments About the Information Contained in This Supplement

No person has been authorized to give any information or to make any representation in connection with the Arrangement and other matters described herein other than those contained in the Circular and this Supplement, and, if given or made, any such information or representation should be considered not to have been authorized by the Company. Information contained in the Circular and this Supplement should not be construed as legal, tax or financial advice and Shareholders are urged to consult their own professional advisors in connection therewith. Except as expressly amended or supplemented by this Supplement, all financial and non- financial information in the Circular remains unchanged. Readers are cautioned to review Liminal BioSciences' public filings subsequent to the date of the Circular, available at www.sedarplus.ca, and its filings under the Securities Exchange Act of 1934, as amended, available at www.sec.gov, including, without limitation, materials furnished to the U.S. Securities and Exchange Commission on Form 6-K. Unless otherwise indicated, references to "$" or "C$" refer to the lawful currency of Canada and references to "US$" refer to the lawful currency of the United States of America.

Attending and Participating at the Meeting

Registered Shareholders and duly appointed proxyholders (including non-registered Shareholders who duly appointed themselves as proxyholders) will be able to attend, participate and vote at the Meeting online at https://web.lumiagm.com/465634100(meeting ID: 465-634-100). Recommended internet browsers are Google Chrome, Firefox, Internet Explorer 11, Microsoft Edge and Safari. Such persons may then join the Meeting by entering a Username and Password before the start of the Meeting:

• Registered shareholders: The control number located on the form of proxy or in the email notification you received is the Username. The Password to the Meeting is "liminal2023" (case sensitive).
  If, as a registered shareholder, you are using your control number to login to the Meeting and you accept the terms and conditions, you will be revoking any and all previously submitted proxies for the Meeting and will be provided the opportunity to vote by online ballot on the matters put forth at the Meeting. If you do not wish to revoke a previously submitted proxy, as the case may be, you will not be able to participate at the Meeting online.
• Duly appointed proxyholders: Computershare will provide the proxyholder with a Username by e-mail after the voting deadline has passed. The Password to the Meeting is "liminal2023" (case sensitive).

LIMINAL BIOSCIENCES INC.

P a g e | 2Supplement dated September 12, 2023 to the Management Information Circular dated August 16, 2023

Only registered Shareholders and duly appointed proxyholders will be entitled to attend, participate and vote at the Meeting. Non-registered Shareholders who have not duly appointed themselves as proxyholder will not be able to attend, participate, vote or ask questions at the Meeting.

Shareholders who wish to appoint a third-party proxyholder to represent them at the Meeting (including non-registered Shareholders who wish to appoint themselves as proxyholder to attend, participate, vote or ask questions at the Meeting) MUST submit their duly completed proxy or voting instruction form AND register the proxyholder. See "Appointment of a Third Party as Proxy" in the Circular.

If you are a non-Registered Shareholder located in the United States and wish to attend, participate, vote or ask questions at the Meeting or, if permitted, appoint a third party as your proxyholder, you MUST also submit your legal proxy to Computershare. See "Appointment of a Third Party as Proxy" in the Circular.

If you attend the Meeting online, it is important that you are connected to the internet at all times during the Meeting in order to vote when balloting commences. It is your responsibility to ensure connectivity for the duration of the Meeting. You should allow ample time to check into the Meeting online and complete the related procedure.

Depositing Proxies

Your proxy can be submitted to Computershare either in person, or by mail or courier, to 1500 Robert-Bourassa Boulevard, Montreal QC H3A 3S8, Attention: Proxy Department or100 University Avenue, Toronto ON M5J 2Y1 Attention: Proxy Department or via the internet at www.investorvote.com. The proxy must be deposited with Computershare by no later than 5:00 p.m. (Eastern time) on September 13, 2023, or if the Meeting is adjourned or postponed, not less than 48 hours, excluding Saturdays, Sundays and statutory holidays, before the commencement of such adjourned or postponed Meeting.

If you have received a voting instruction form, you should carefully follow the instructions set out therein to ensure that your Shares are voted at the Meeting in accordance with your instructions. If you are a non-registered Shareholder, you should also carefully follow the instructions provided by your Intermediary to ensure that your Shares are voted at the Meeting in accordance with your instructions.

Revocation of Proxies

If you are a registered shareholder, you may revoke your proxy at any time before it is acted upon in any manner permitted by law, including by stating clearly, in writing, that you wish to revoke your proxy and by delivering this written statement to Computershare, no later than the last Business Day before the day of the Meeting. If as a registered shareholder you are using your control number to login to the Meeting and you accept the terms and conditions, you will be revoking any and all previously submitted proxies and will be provided the opportunity to vote by online ballot on the matters put forth at the Meeting. If you do not wish to revoke a previously submitted proxy, as the case may be, you will not be able to participate at the Meeting online.

If you are a non-registered Shareholder and wish to revoke previously provided voting instructions, you should follow carefully the instructions provided by your Intermediary.

LIMINAL BIOSCIENCES INC.

P a g e | 3Supplement dated September 12, 2023 to the Management Information Circular dated August 16, 2023

Letter to Shareholders

The fourth, fifth and sixth paragraphs under the heading "Letter to Shareholders" on page i of the Circular are hereby deleted in their entirety and replaced with the following:

"A special committee of the Board consisting entirely of disinterested directors (the "Special Committee") conducted, with the assistance of its legal and financial advisors, a review of the Company's alternatives available to the Company and obtained an independent valuation of the Shares. Following this process, and after, among other things, receiving outside legal and financial advice in evaluating the Arrangement and careful consideration of various matters, the Special Committee unanimously determined

1. that the Arrangement is fair to the Unaffiliated Securityholders and (ii) that the Arrangement and the entering into of the Arrangement Agreement (as defined below) is in the best interests of the Company, and unanimously recommended that the Board

approve the Arrangement and recommends that the Minority Shareholders vote IN FAVOURof the Arrangement Resolution."

On the unanimous recommendation of the Special Committee, and after, among other things, receiving outside legal and financial advice in evaluating the Arrangement and careful consideration of various matters, the Board, with Messrs. Eugene Siklos and Alek Krstajic (being the two directors on the Board affiliated with SALP) having recused themselves, unanimously determined (i) that the Arrangement is fair to the Unaffiliated Securityholders and (ii) that the Arrangement and the entering into of the Arrangement Agreement is in the best interests of the Company, and recommends that the Minority Shareholders vote IN FAVOURof the Arrangement Resolution.

In evaluating the Arrangement, the Special Committee consulted with the Company's management and the Special Committee's legal and financial advisors and carefully reviewed the proposed Arrangement and the terms and conditions of the Arrangement Agreement and related agreements and documents and, in determining that the Arrangement is in the best interests of the Company and fair to the Unaffiliated Securityholders, the Special Committee considered and relied upon a number of substantive factors as more fully described in the accompanying management information circular (the "Circular").

Table of Contents

The Circular is hereby amended by adding a subheading entitled "Certain Prospective Financial Information" beneath "Interests of Certain Persons in the Arrangement" on page 5 of the Circular and "Appendix G Directors and Officers of the Purchaser Filing Parties" beneath "Appendix F Section 190 of the Canada Business Corporations Act" on page 7 of the Circular.

The Circular is further amended by replacing the heading "Benefit of the Arrangement for the Company's Minority Shareholders" beneath "The Arrangement" with "Benefit of the

Arrangement for the Company's Minority Shareholders (including Unaffiliated Securityholders)" and by replacing the heading "Detriments of the Arrangement for the Company's Minority Shareholders" beneath "The Arrangement" with "Detriments of the

Arrangement for the Company's Minority Shareholders (including Unaffiliated Securityholders)".

Directors and Officers of the Purchaser Filing Parties

The Circular is hereby amended by adding "Appendix G Directors and Officers of the Purchaser Filing Parties", attached as Schedule A to this Supplement, after "Appendix F Section 190 of the Canada Business Corporations Act" on page 140 of the Circular.

LIMINAL BIOSCIENCES INC.

P a g e | 4Supplement dated September 12, 2023 to the Management Information Circular dated August 16, 2023

Information Concerning the Purchaser Filing Parties

The first and second paragraphs under the subheading "Purchaser and Thomvest" on page 17 of the Circular are hereby deleted in their entirety and replaced with the following:

"Structured Alpha LP, the Purchaser, is a limited partnership existing under the laws of the Cayman Islands, managed by its general partner, Thomvest Asset Management Ltd., a corporation existing under the laws of the Province of Ontario, with a registered head office located at 65 Queen Street West, Suite 2400 Toronto, Ontario M5H 2M8. The telephone number of the Purchaser's principal executive office is 1-416-364-8700.

Thomvest and its affiliates are a group of investment companies which make investments on behalf of Peter J. Thomson and his family, and the Purchaser is a holding company controlled by Thomvest through which Peter J. Thomson and his family make such investments. Mr. Thomson is the founder, chief executive officer and a director of Thomvest. Mr. Siklos is a director and president of Thomvest and also a director of the Company."

The first and second paragraphs under the heading "Information Concerning the Purchaser Filing Parties" on page 87 of the Circular are hereby deleted in their entirety and replaced with the following:

"The Purchaser is a limited partnership existing under the laws of the Cayman Islands, managed by its general partner, Thomvest Asset Management Ltd., a corporation existing under the laws of the Province of Ontario, with a registered head office located at 65 Queen Street West, Suite 2400 Toronto, Ontario M5H 2M8. The telephone number of the Purchaser's principal executive office is 1-416-364-8700.

Thomvest and its affiliates are a group of investment companies which make investments on behalf of Peter J. Thomson and his family, and the Purchaser is a holding company controlled by Thomvest through which Peter J. Thomson and his family make such investments. Mr. Thomson is the founder, chief executive officer and a director of Thomvest. Mr. Siklos is a director and president of Thomvest and also a director of the Company."

Directors and Executive Officers

The Circular is hereby amended by adding "Appendix H Directors and Officers of the Company", attached as Schedule B to this Supplement, beneath "Appendix G Directors and Officers of the Purchase Filing Parties".

The last paragraph under the heading "Directors and Executive Officers" on page 91 of the Circular is amended and supplemented by adding the following after the last sentence:

"The name, business address, present principal occupation or employment, material occupations or employment in the past five years, and citizenship of each director and executive officer of Liminal BioSciences Inc. are set forth in Appendix H to this Circular and is incorporated by reference herein."

LIMINAL BIOSCIENCES INC.

P a g e | 5Supplement dated September 12, 2023 to the Management Information Circular dated August 16, 2023