Exhibit 15
LETTER REGARDING UNAUDITED INTERIM FINANCIAL INFORMATION
Securities and Exchange Commission
100 F Street, N.E.
Washington, D.C. 20549
Commissioners:
We are aware that our report (which includes an explanatory paragraph as to the Company’s ability to continue as a going concern) dated August 6, 2015 on our reviews of the interim financial information of CTI BioPharma Corp. as of June 30, 2015 and for the three and six-month interim periods ended June 30, 2015 and 2014 and included in the Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2015 is incorporated by reference in this Registration Statement on Form S-8 of CTI BioPharma Corp.
Yours very truly,
/s/ Marcum LLP
Marcum LLP
San Francisco, California
September 28, 2015