Third Amendment

Exhibit 99.4

Third Amendment

This Amendment (the "Third Amendment") effective as of May 19, 2016 (the "Effective Date"), is entered into by and between CRYSTALGENOMICS, INC., a South Korean corporation having a place of business at 5th F. Bldg.A, Korea Bio Park, 700 Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-400 Korea ("CG") and APTOSE BIOSCIENCES, INC., a Canadian corporation having a place of business at 0000 Xxxxxxx Xxxx, Xxxxx 000, Xxxxxxxxxxx, Xxxxxxx, X0X 0X0, Xxxxxx ("Aptose"). CG and Aptose are sometimes referred to herein individually as a "Party" and collectively as the "Parties".

The Parties hereby desire to make an amendment of the OPTION AND LICENSE AGREEMENT (the "Agreement") between CG and Aptose with an Execution Date of March 24, 2016 to revise the following terms and conditions per below, pursuant to Section 2.1 of the Agreement.

	1.	The Parties agree to extend the Evaluation Period until June 6, 2016.
	2.	Upon Aptose's decision to obtain the option on or before June 6, 2016, Aptose shall pay CG, as evidenced by a wire transfer receipt, the Option Grant Fee by the end of business, 5pm US Eastern Standard Time (EST), June 6, 2016.

This Third Amendment hereby replaces the First Amendment, which was executed on April 26, 2016.

IN WITNESS WHEREOF, the parties hereto have caused this Third Amendment to be executed as of the Effective Date written above by their respective authorized representatives. The parties hereby affirm that this Third Amendment accurately and completely reflects their understanding and agreements.

CRYSTALGENOMICS, INC.			APTOSE BIOSCIENCES, INC.
By:	/s/ Dr. Joong Xxxxx Xxx		By:	/s/ Xxxxxxx Xxxxxxxx
Name:	Dr. Joong Xxxxx Xxx		Name:	Xxxxxxx Xxxxxxxx
Title:	CEO		Title:	SVP, Chief Business Officer
Date:	May 19, 2016		Date:	May 19, 2016