Aptose Biosciences Inc. — Proxy Solicitation & Information Statement 2023

Apr 26, 2023

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8th Floor, 100 University Avenue Toronto, Ontario M5J 2Y1 www.computershare.com

Security Class

Holder Account Number

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Form of Proxy - Annual and Special Meeting to be held on May 23, 2023

This Form of Proxy is solicited by and on behalf of Management.

Notes to proxy

1. Every holder has the right to appoint some other person or company of their choice, who need not be a holder, to attend and act on their behalf at the meeting or any adjournment or postponement thereof. If you wish to appoint a person or company other than the Management Nominees whose names are printed herein, please insert the name of your chosen proxyholder in the space provided (see reverse).

2. If the securities are registered in the name of more than one owner (for example, joint ownership, trustees, executors, etc.), then all those registered should sign this proxy. If you are voting on behalf of a corporation or another individual you may be required to provide documentation evidencing your power to sign this proxy with signing capacity stated.

3. This proxy should be signed in the exact manner as the name(s) appear(s) on the proxy.

4. If a date is not inserted in the space provided on the reverse of this proxy, it will be deemed to bear the date on which it was mailed to the holder by Management.

5. The securities represented by this proxy will be voted as directed by the holder, however, if such a direction is not made in respect of any matter, and the proxy appoints the Management Nominees listed on the reverse, this proxy will be voted as recommended by Management.

6. The securities represented by this proxy will be voted in favour, or withheld from voting, or voted against each of the matters described herein, as applicable, in accordance with the instructions of the holder, on any ballot that may be called for. If you have specified a choice with respect to any matter to be acted on, the securities will be voted accordingly.

7. This proxy confers discretionary authority in respect of amendments or variations to matters identified in the Notice of Meeting and Management Information Circular or other matters that may properly come before the meeting or any adjournment or postponement thereof, unless prohibited by law.

8. This proxy should be read in conjunction with the accompanying documentation provided by Management.

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Proxies submitted must be received by 5:00 pm, Eastern Daylight Time, on May 18, 2023.

VOTE USING THE TELEPHONE OR INTERNET 24 HOURS A DAY 7 DAYS A WEEK!

• To Receive Documents To Virtually Attend

• To Vote Using the Telephone To Vote Using the Internet Electronically the Meeti ~~n~~ g

• • Call the number listed BELOW from a touch • Go to the following web • You can enroll to receive future securityholder • You can attend the meeting virtually by tone telephone. site: www.investorvote.com communications electronically by visiting visiting the URL provided on the back of

• 1-866-732-VOTE (8683) Toll Free • Scan the QR code Smartphone? www.investorcentre.com. this document. to vote now.

If you vote by telephone or the Internet, DO NOT mail back this proxy.

Voting by mail may be the only method for securities held in the name of a corporation or securities being voted on behalf of another individual. Voting by mail or by Internet are the only methods by which a holder may appoint a person as proxyholder other than the Management Nominees named on the reverse of this proxy. Instead of mailing this proxy, you may choose one of the two voting methods outlined above to vote this proxy.

To vote by telephone or the Internet, you will need to provide your CONTROL NUMBER listed below.

CONTROL NUMBER

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Appointment of Proxyholder

I/We being holder(s) of securities of Aptose Biosciences Inc. (the “Corporation”) hereby appoint: William G. Rice, or failing this person, Denis Burger (the “Management Nominees”)

Print the name of the person you are OR appointing if this person is someone other than the Management Nominees listed herein.

Note: If completing the appointment box above YOU MUST go to http://www.computershare.com/aptose and provide Computershare with the name and email address of the person you are appointing. Computershare will use this information ONLY to provide the appointee with a user name to gain entry to the online meeting.

as my/our proxyholder with full power of substitution and to attend, act and to vote for and on behalf of the holder in accordance with the following direction (or if no directions have been given, as the proxyholder sees fit) and on all other matters that may properly come before the Annual and Special Meeting of shareholders of the Corporation to be held on May 23, 2023 at 9:00 am, Pacific Daylight Time, in person at Highlands Corporate Center - Conference Room, 12730 High Bluff Drive, Cantina Ste, San Diego, 92130 or by live webcast accessible directly online at https://web.lumiagm.com/472428776 (the “Meeting”) and at any adjournment or postponement thereof.

VOTING RECOMMENDATIONS ARE INDICATED BY HIGHLIGHTED TEXT OVER THE BOXES.

1. Election of Directors

1. Election of Directors
	For	Against			For	Against			For	Against
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01. Carol Ashe				02. Dr. Denis Burger			03. Dr. Eric Platzer
04. Dr. William G. Rice				05. Dr. Mark D. Vincent			06. Warren Whitehead
07. Dr. Bernd R. Seizinger
								For	Abstain Against
2. Appointment of Auditors Appointment of KPMG, LLP as the independent accounting frm				for the Corporation.
								For	Abstain Against
3. Amendment to 2021 Stock Incentive Plan
Resolution approving an amendment to the Corporation’s			2021	stock incentive plan to increase the number of shares available thereunder by
1,027,758 shares.
								For	Abstain Against
4. Reverse Stock Split
Special resolution approving the adoption of an amendment to the Corporation’s articles to effect a reverse stock						split of the Corporation’s outstanding
shares at a ratio in the range of 1-for-10 to 1-for-20.
								For	Abstain Against
5. Multiple Adjournments Resolution approving one or more adjournments of the Meeting, if necessary or appropriate, if a quorum is present, to permit further solicitation of proxies if there are not suffcient votes at the time of the Meeting to approve Proposals No. 3 and 4.											Fold
								For	Abstain Against

6. Say-on-Pay

Advisory (non-binding) resolution on the compensation of the Corporation’s named executive officers.

Signature of Proxyholder

Signature(s) Date

I/We authorize you to act in accordance with my/our instructions set out above. I/We hereby revoke any proxy previously given with respect to the Meeting. If no voting instructions are indicated above, and the proxy appoints the Management Nominees, this Proxy will be voted as recommended by Management.

MM / DD / YY

Interim Financial Statements – Mark this box if you would like to receive Interim Financial Statements and accompanying Management’s Discussion and Analysis by mail.

Annual Financial Statements – Mark this box if you would NOT like to receive the Annual Financial Statements and accompanying Management’s Discussion and Analysis by mail.

If you are not mailing back your proxy, you may register online to receive the above financial report(s) by mail at www.computershare.com/mailinglist.

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