June 9, 2017

BVF Partners L.P.
One Sansome Street, 39th Floor
San Francisco, CA 94104
Ladies and Gentlemen:
By execution below, each of CTI BioPharma Corp., a Washington corporation (the
“Company”), and BVF Partners L.P. (together with its affiliates, the
“Shareholder”) agree as follows:
1.Exchange.
a.    Subsequent to the consummation of the underwritten public offering (the
“Offering”) of an aggregate of 22,500 shares of the Company’s Series N-3
Preferred Stock, no par value per share, pursuant to the Underwriting Agreement,
dated June 6, 2017, by and among the Company and Jefferies LLC, as
representative of the several underwriters named therein and if necessary to
limit the Shareholder’s beneficial ownership of the Company’s common stock, no
par value per share (the “Common Stock”) to 9.99% of the Company’s issued and
outstanding Common Stock, the Company agrees, subject to the approval of the
Company’s Board of Directors (the “Board”) and the Audit Committee of the Board,
that the Shareholder may make a one-time election to exchange shares of Common
Stock purchased by the Shareholder directly from the Company or underlying
shares of Preferred Stock purchased by the Shareholder directly from the Company
into shares of a new series of convertible, non-voting preferred stock of the
Company with substantially similar terms as the Preferred Stock issued in the
Offering, including a “blocker” on conversion into Common Stock initially set at
9.99% of the Company’s Common Stock, but without the automatic conversion
provisions (the “Exchange ”). The Company also agrees to use commercially
reasonable efforts to cooperate with the Shareholder to effectuate the Exchange,
provided that such Exchange does not adversely affect the Company’s ability to
effect a reverse stock split without the necessity for stockholder approval and
complies with applicable federal and state securities laws. The Exchange (and
the subsequent conversion of the Blocker Preferred back into Common Stock) shall
be effected pursuant to Section 3(a)(9) under the Securities Act of 1933, and
shall be an exempt transaction pursuant to Section 16b-3 of the Exchange Act.
b.    Shareholder’s right to effectuate the Exchange will terminate when the
Shareholder ceases to beneficially own at least 5% of the Company’s outstanding
Common Stock on a fully-diluted basis.
c.    For purposes of this Paragraph 1, “beneficial ownership” shall be
determined in accordance with Rule 13d-3 promulgated under the Securities
Exchange Act of 1934, as amended, on an as-converted to Common Stock basis,
without regard to any blockers.
2.
Miscellaneous.

a.    This Letter Agreement may not be amended, supplemented or modified except
in writing, duly executed by all of the parties.
b.    This Letter Agreement constitutes the entire agreement of the parties with
respect to the subject matter hereof. Each of the parties represents that they
has been advised by counsel in connection with their review, execution and
delivery of this Letter Agreement.
c.    This Letter Agreement shall be governed by and construed in accordance
with the internal substantive laws of the State of New York.
d.    This Letter Agreement may be executed in more than one counterpart. Each
such counterpart shall be deemed an original and all counterparts, taken
together, shall constitute one and the same instrument.

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e.    Neither this Letter Agreement nor any rights or obligations hereunder
shall be assigned or delegated by any party without the prior written consent of
the other party.
[Signature Page to Follow]

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IN WITNESS WHEREOF, the parties have caused this Letter Agreement to be executed
in multiple originals by their authorized officers, all as of the date and year
first written above.

 
CTI BIOPHARMA CORP.

By:    /s/ Bruce J. Seeley        
Name:    Bruce J. Seeley            
Title:    Executive Vice President, Chief     
Commercial Officer and
    Administrative     Officer            

[Signature Page to Letter Agreement]

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BVF PARTNERS L.P.

By: /s/ Matthew Perry            
Name:    Matthew Perry            
Title:    President