On December 17, 2018, Gene Mack submitted his resignation as Chief Financial Officer and Treasurer of SELLAS Life Sciences Group, Inc., effective immediately. On December 17, 2018, the company engaged Aleksey Krylov as a consultant to provide financial services to the company on an interim basis for an initial term of three months. Mr. Krylov previously served as the company's Chief Financial Officer from October 24, 2017 through April 20, 2018.

On December 17, 2018, the Board of Directors of the company appointed John T. Burns, the company's Vice President, Finance and Corporate Controller, as the company's interim principal accounting officer. Mr. Burns joined the company in May 2013 and has held various positions of increasing responsibility during his tenure, including his current position of Vice President, Finance and Corporate Controller which he has held since December 30, 2017. Prior to joining the company, Mr. Burns was a Securities and Exchange Reporting Manager at Pixelworks, Inc. and began his career in public accounting at Moss Adams LLP.