Washington, D.C. 20549






Proxy Statement Pursuant to Section 14(a)

of the Securities Exchange Act of 1934




Filed by the Registrant  x                             Filed by a Party other than the Registrant  ¨

Check the appropriate box:

¨ Preliminary Proxy Statement
¨ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
¨ Definitive Proxy Statement
x Definitive Additional Materials
¨ Soliciting Material Pursuant to § 240.14a-12



(Name of Registrant as Specified In Its Charter)


(Name of Person(s) Filing Proxy Statement if Other Than the Registrant)


Payment of Filing Fee (Check the appropriate box)

x No fee required.
¨ Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.


Title of each class of securities to which transaction applies:



Aggregate number of securities to which transaction applies:



Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (Set forth the amount on which the filing fee is calculated and state how it was determined):



Proposed maximum aggregate value of transaction:



Total fee paid:


¨ Fee paid previously with preliminary materials.
¨ Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.


Amount Previously Paid:



Form, Schedule or Registration Statement No.:



Filing Party:



Date Filed:












C 1234567890 ENDORSEMENT_LINE SACKPACK MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 ADD 5 ADD 6 Online Go to www.envisionreports.com/SLS or scan the QR code — login details are located in the shaded bar below. Votes submitted electronically must be received by 9:00 a.m., Eastern Daylight Time, on June 7, 2020. Important Notice Regarding the Availability of Proxy Materials for the SELLAS Life Sciences Group, Inc. Company Stockholder Meeting to be Held on June 9, 2020 Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual stockholders’ meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy. The items to be voted on and location of the annual meeting are on the reverse side. Your vote is important! This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The 2020 proxy statement and annual report to shareholders are available at: Easy Online Access — View your proxy materials and vote. Step 1: Go to www.envisionreports.com/SLS. Step 2: Click on the icon on the right to view meeting materials. Step 3: Return to the investorvote.com window and follow the instructions on the screen to log in. Step 4: Make your selections as instructed on each screen for your delivery preferences. Step 5: Vote your shares. When you go online, you can also help the environment by consenting to receive electronic delivery of future materials. Obtaining a Copy of the Proxy Materials – If you want to receive a copy of the proxy materials, you must request one. There is no charge to you for requesting a copy. Please make your request as instructed on the reverse side on or before May 15, 2020 to facilitate timely delivery.







Stockholder Meeting Notice SELLAS Life Sciences Group, Inc.’s Annual Meeting of Stockholders will be held on June 9, 2020 at 15 West 38th Street, 4th Floor, New York, NY 10018, at 8:30 a.m. Eastern Daylight Time. Proposals to be voted on at the meeting are listed below along with the Board of Directors’ recommendations. The Board of Directors recommends a vote FOR all the nominees listed and FOR Proposals 2 and 3: 1. To Elect Three Class I Directors. Directors are elected by a plurality of the votes of the holders of shares present in person or represented by proxy and entitled to vote on the election of directors. Accordingly, the nominee receiving the highest number of affirmative votes will be elected. The nominees for Class I director to be considered at the annual meeting are Jane Wasman, John Varian and Robert Van Nostrand. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the foregoing slate of Class I Directors. 2. To Ratify the Selection by the Audit Committee of Moss Adams LLP as our Independent Registered Public Accounting Firm for the Fiscal Year Ending December 31, 2020. The affirmative vote of the holders of shares of common stock representing a majority of the votes cast on the matter is required for the ratification of the selection of Moss Adams LLP as our independent registered public accounting firm for the current fiscal year. 3. To approve, on a nonbinding advisory basis, the compensation of our Named Executive Officers. This proposal calls for a nonbinding, advisory vote, and accordingly there is no “required vote” that would constitute approval. However, our Board of Directors, including our compensation committee, values the opinions of our stockholders and we will consider our stockholders’ concerns to the extent there are a substantial number of votes cast against the executive officer compensation as disclosed in this proxy statement and evaluate what actions may be appropriate to address those concerns. PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must go online or request a paper copy of the proxy materials to receive a proxy card. If you wish to attend and vote at the meeting, please bring this notice with you. Here’s how to order a copy of the proxy materials and select delivery preferences: Current and future delivery requests can be submitted using the options below. If you request an email copy, you will receive an email with a link to the current meeting materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a copy of the proxy materials. Internet Go to www.envisionreports.com/SLS. Phone – Call us free of charge at 1-866-641-4276. Email – Send an email to investorvote@computershare.com with “Proxy Materials SELLAS Life Sciences Group, Inc.” in the subject line. Include your full name and address, plus the number located in the shaded bar on the reverse side, and state that you want a paper copy of the meeting materials. To facilitate timely delivery, requests for a paper copy of proxy materials must be received by May 15, 2020.