First Amendment to Amended and Restated Exclusive License Agreement between SLSG Limited LLC and Memorial Sloan Kettering Cancer Center, effective as of September 29, 2020

This First Amendment to Amended and Restated Exclusive License Agreement (this “Amendment”), effective as of September 29, 2020 (the “Effective Date”), is entered into by and between SLSG Limited LLC (together with its affiliates, hereinafter collectively “Company”), a Delaware limited liability company with a place of business at 15 West 38th Street, 10th Floor, New York, New York 10018, and Memorial Sloan Kettering Cancer Center, a New York not-for-profit corporation with a principal office address at 1275 York Avenue, New York, New York 10065 (“MSK”).

WHEREAS, the Company is a wholly-owned subsidiary of Sellas Life Sciences Group Ltd., an exempted limited company incorporated under the laws of Bermuda with offices at Clarendon House, 2 Church Street, Hamilton HM11, Bermuda (“Sellas Limited”); and

WHEREAS, Sellas Limited is a wholly-owned subsidiary of SELLAS Life Sciences Group, Inc., a Delaware corporation with a place of business at 15 West 38th Street, 10th Floor, New York, New York 10018; and

WHEREAS, Sellas Limited and MSK entered into that certain Amended and Restated Exclusive License Agreement, dated as of October 10, 2017 (the “Agreement”); and

WHEREAS, Sellas Limited assigned all of its right, title and interest in and to the Agreement to the Company pursuant to that certain Assignment of License dated as of June 28, 2019 by and between Sellas Limited, as assignor, and the Company, as assignee (the “Assignment”); and

WHEREAS, following and as a result of the execution of the Assignment, the Company is the successor-in-interest to Sellas Limited under the Agreement and is as of the Effective Date a Party and the Licensee under and pursuant to the Agreement; and

WHEREAS, the Parties to the Agreement desire to, and hereby do, amend the Agreement in accordance with the terms hereof.

NOW, THEREFORE, in exchange for the promises set forth herein, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, intending to be legally bound, the Parties hereby agree as follows:

1. Definitions. Capitalized terms used, but otherwise not defined herein shall have the meanings given to such terms in the Agreement.

2. Original Patent Rights – Exhibit A. Exhibit A to the Agreement is hereby amended by deleting such Exhibit A in its entirety and substituting in place thereof the copy of Exhibit A attached hereto as Appendix 1 to this Amendment and made a part hereof. The definition of Original Patent Rights is automatically and without any further action by the Parties amended to include all of the patents and patent applications included within Exhibit A, as amended by this Amendment.

3. Additional Patent Rights – Exhibit B. Exhibit B to the Agreement is hereby amended by deleting such Exhibit B in its entirety and substituting in place thereof the copy of Exhibit B attached hereto as Appendix 2 to this Amendment and made a part hereof. The definition of Additional Patent Rights is automatically and without any further action by the Parties amended to include all of the patents and patent applications included within Exhibit B, as amended by this Amendment.

4. Governing Law. The validity, enforcement, construction, and interpretation of this Amendment are governed by the laws of the State of New York and the federal laws of the United States of America, excluding the laws of those jurisdictions pertaining to resolution of conflicts with laws of other jurisdictions.

5. Successors and Assigns. This Amendment is binding on, and inures to the benefit of, the Parties, their authorized and permitted heirs, successors and assigns.

6. Counterparts; Effective Date. The Parties may execute this Amendment by facsimile or other electronic transmission, in pdf file format or otherwise, and in counterparts. Each executed counterpart of this

Amendment will constitute an original document, and all executed counterparts, together, will constitute the same agreement. This Amendment will become effective as of the Effective Date.

7. Complete Agreement; Ratification and Confirmation. The headings of the Sections of this Amendment are solely for convenient reference and neither constitutes a part of this Amendment nor affect its meaning, interpretation, or effect. This Amendment, together with the Agreement, records the entire understanding of the Parties with respect to the terms of this Amendment and the Agreement and the restrictions and subject matter stated in it and them, and supersedes any previous or contemporaneous agreement, representation, or understanding, oral or written, by either of them. The Agreement, as amended by this Amendment, is in full force and effect, and is hereby ratified and confirmed by the Parties in every respect.