July 29, 2019
Securities and Exchange Commission
100 F Street N.E.
Washington, D.C. 20549
We have been furnished with a copy of Item 4.01 of Form 8-K for the event that occurred on July 29, 2019, to be filed by Mateon Therapeutics, Inc. We agree with the statements made in paragraph 2 of that Item 4.01 insofar as they relate to OUM & Co. LLP.
Very truly yours,
/s/ OUM & CO. LLP
San Francisco, California
July 29, 2019