SELLAS Life Sciences (SLS) 8-K Changes in Registrant's Certifying Accountant

Exhibit 16.1

May 16, 2013

Securities and Exchange Commission

100 F Street N.E.

Washington, D.C. 20549

We have been furnished with a copy of the response to Item 4.01 of Form 8-K for the event that occurred on May 13, 2013, to be filed by our former client, Galena Biopharma, Inc. We agree with the statements made in response to that Item insofar as they relate to our Firm.

Very truly yours,

/s/ BDO USA, LLP

Seattle, Washington