Narrative Disclosure To Summary Compensation Table

TheNon-Equity Incentive Plan Short Term Compensation Committee

Annual bonuses for our executive officers are based on the achievement of corporate goals typically meets at least quarterlycomprised of a mix of clinical, financial and with greater frequency if necessary. The agenda for each meeting is usually developed by the Chairman of the Compensation Committee, in consultation with the Chief Executive Officer. The Compensation Committee meets regularly in executive session. However, from time to time, various members of management and other employees as well as outside advisors or consultants may be invited by the Compensation Committee to make presentations, to provide financial or other background information or advice or to otherwise participate in Compensation Committee meetings. The Chief Executive Officer may not participate in, or be present during, any deliberations or determinations of our Compensation Committee regarding his compensation or individualbusiness development performance objectives. The chartercorporate goals are approved by the Board of Directors on an annual basis at the start of each year. Dr. Stergiou’s bonus is based 100% on the level of achievement of the Compensation Committee grantscorporate goals, while the Compensation Committee full access to all books, records, facilities and personnelbonuses of the Company. In addition, under the charter, the Compensation Committee has the authority to obtain, at the expenseother executive officers are computed based on a combination of the Company, adviceachievement of corporate goals and assistance from compensation consultants and internal and external legal, accounting or other advisors and other external resources that the Compensation Committee considers necessary or appropriate in the performance of its duties. The Compensation Committee has direct responsibility for the oversight of the work of any consultants or advisers engaged for the purpose of advising our Compensation Committee. In particular, the Compensation Committee has the sole authority to retain, in its sole discretion, compensation consultants to assist in its evaluation of executive and director compensation, including the authority to approve the consultant’s reasonable fees and other retention terms. Under the charter, the Compensation Committee may select, or receive advice from, a compensation consultant, legal counsel or other adviser to the Compensation Committee, other than in-house legal counsel and certain other types of advisers, only after taking into consideration six factors, prescribed by the SEC and Nasdaq, that bear upon the adviser’s independence; however, there is no requirement that any adviser be independent.individual performance.

During the year ended December 31, 2019,Equity Grants

In March 2020, the Compensation Committee recommended, and our Board approved, the grant of 8,500, 3,300, 1,80070,000 and 1,00025,000 options to Dr. Stergiou and Ms. Wood, Mr. Burns, and Dr. Sarlis respectively, at an exercise price of $69.00$1.89 per share.share, which was the fair market value on the grant date. One quarter of the shares subject to these options vested in March 20202021 and the remaining shares subject to the options will vest and become exercisable in equal monthly installments for 36 months thereafter. During the year ended December 31, 2018,In March 2020, the Compensation Committee recommended, and our Board approved the grant of 1,900, 1,000, 400, and 1,400 optionsalso granted to Dr. Stergiou, Ms. Wood, Mr. Burns, and Dr. Sarlis respectively,Cicic, pursuant to his employment offer letter described below, 35,000 options at an exercise price of $262.00$1.89 per share.share, which was the fair market value on the grant date. One quarter of the shares subject to these options vested in March 20192021 and the remaining shares subject to the options will vest and become exercisable in equal monthly installments for 36 months thereafter. In addition, in March 2020, the Compensation Committee recommended, and our Board approved, the grant of 95,000, 35,000 and 25,000 performance-based restricted stock units to Dr. Stergiou, Ms. Wood and Dr. Cicic, respectively (the “March 2020 RSUs”). The March 2020 RSUs will vest as follows: (i) 50% on meeting the primary endpoint in the Company’s Phase 3 REGAL study for its lead clinical candidate, galinpepimut-S (“GPS”) and (ii) 50% upon approval by the U.S. Food and Drug Administration (“FDA”) of a biologics license application (“BLA”) for GPS.

We have entered into employment agreements with each of the named executive officers described below, which include standard confidential information and/or inventions assignment agreements, and under which each of the named executive officers has agreed not to disclose our confidential information. The named executive officers are each eligible to participate in, subject to applicable eligibility requirements, all of our employee retirement and welfare benefit plans and programs made available to senior level executives. All severance benefits payable to the named executive officers under their employment agreements are subject to their signing, not revoking and complying with a release of claims in favor of us and are subject to applicable taxes and withholding.

Angelos M. Stergiou, M.D., Sc.D. h.c.

In September 2016, Private SELLAS entered into an employment agreement, or 2016 Stergiou Agreement, with Dr. Stergiou, President and Chief Executive Officer. The 2016 Stergiou Agreement was replaced and superseded in March 2019 by a new employment agreement, or the 2019 Stergiou Agreement, with Dr. Stergiou. Under 2016 Stergiou Agreement, which was governed by Bermuda law, Dr. Stergiou was entitled to an annual base salary of $400,000, net of all legally required applicable taxes, withholdings and deductions (subject to review and adjustment in the discretion of the Board or the compensation committee) and a discretionary annual cash bonus, with a target amount no less than 30% of Dr. Stergiou’s then effective base salary (subject to continued employment and the achievement of certain performance objectives established by the Board of Directors or compensation committee). The 2016 Stergiou Agreement also provided that Dr. Stergiou would receive a monthly housing allowance of $10,000, net of all legally required applicable taxes, withholdings and deductions, and would be eligible to receive an additional discretionary bonus as determined by the Company in its sole discretion.

The 2016 Stergiou Agreement did not have a specified term and either party could terminate such agreement by providing written notice at any time, with or without cause.

The 2019 Stergiou Agreement became effective as of July 1, 2019, at which time it replaced and superseded the 2016 Stergiou Agreement. The 2019 Stergiou Agreement has an initial two-year term unless terminated prior thereto (i) by us with cause (at any time) or without cause (upon at least 30 days’ prior written notice), or (ii) by Dr. Stergiou for good reason (upon at least 90 days prior written notice of the reason with a cure period of 30 days for us to correct the act or failure to act that constitutes good reason), or without good reason (upon at least 90 days prior written notice) or (iii) due to Dr. Stergiou’s death or disability. The 2019 Stergiou Agreement shall continue until terminated in accordance with its terms.

Pursuant to the terms of the 2019 Stergiou Agreement, Dr. Stergiou is entitled to an annual base salary of $525,000 (subject to review and adjustment in the sole discretion of the Board or the compensation committee thereof) and a discretionary annual cash bonus, with a target amount no less than 50% of Dr. Stergiou’s then effective base salary (subject to continued employment and the achievement of certain performance objectives established by the Board of Directors or compensation committee of the Board). The agreement also provides that to the extent that any benefit distributable pursuant to the terms of the agreement would be subject to the excise tax imposed under Section 4999 of the Internal Revenue Code of 1986, as amended, or the IRC, then the total payments payable to Dr. Stergiou will be reduced as set forth in the agreement (but not below zero) so that the maximum amount of such payments (after the reduction) shall be one dollar ($1.00) less than the amount which would cause such payments to be subject to the excise tax.

In addition, Dr. Stergiou is eligible to receive equity awards in the sole discretion of the Board or the compensation committee thereof.Compensation Committee.

Nicholas J. Sarlis, M.D., Ph.D., FACP

In September 2016, Private SELLAS entered into an employment agreement with Dr. Sarlis, or the Sarlis Employment Agreement, which was in effect during the years ended December 31, 2017 and 2018. The Sarlis Employment Agreement provided for a four-year term with an annual base salary of $345,000. Pursuant to the terms of such agreement, Dr. Sarlis was eligible to receive a discretionary annual cash bonus of up to 25% of his base salary (subject to continued employment and the achievement of certain performance objectives established by the Board of Directors or compensation committee). Dr. Sarlis was also eligible to receive an additional discretionary bonus.

In January 2019, we entered into a new agreement with Dr. Sarlis, or the Transition Agreement, which superseded the Sarlis Employment Agreement. The Transition Agreement provided that Dr. Sarlis would resign from his position as Chief Medical Officer and become a consultant effective May 15, 2019. Pursuant to the terms of the Transition Agreement, until the termination of his employment, Dr. Sarlis continued to receive his base salary of $380,000 per annum, and continued to participate in our benefit plans and programs. Dr. Sarlis was also entitled to a pro rata cash bonus for the period of his employment in 2019 following determination thereof by the compensation committee and was reimbursed for COBRA coverage for health benefits for the period between the termination of his employment and December 31, 2019. Following the termination of his employment until December 31, 2019, Dr. Sarlis provided consulting services to us for not less than 25 hours per week for a monthly fee of $23,500. Upon termination of Dr. Sarlis’ transition period of employment, Dr. Sarlis received a lump sum payment, paid in February 2020, consisting of his pro-rata incentive bonus for 2019, in an amount that was determined by the board based upon our achievement of the approved corporate goals for 2019, with a target percentage of 40% prorated for the actual number of days in the transition employment period.

Barbara A. Wood, Esq.

Effective March 14, 2018, we entered into an employment letter agreement with Ms. Wood. Under this agreement, Ms. Wood is entitled to an annual base salary of $365,000 (subject to review and adjustment in the discretion of the Board of Directors or the compensation committee)Compensation Committee) and a discretionary annual cash bonus, with a target amount of up to 40% of Ms. Wood’s then-effective base salary (subject to continued employment and the achievement of certain performance objectives established by our Board or compensation committee)Compensation Committee).

In connection with Ms. Wood entering into her employment letter agreement, and pursuant to the terms thereof, we granted to Ms. Wood incentive stock options to purchase up to 1,000 shares of our common stock. The option has an exercise price equal to the market price of our common stock upon the date of grant and vests as to one quarter after one year from grant and with the remainder over 36 equal monthly installments thereafter, so that the option will be fully vested and exercisable four years from the date of grant.

Ms. Wood’s employment letter agreement does not have a specified term and either party may terminate Ms. Wood’s employment agreement by providing written notice at any time, with or without cause. In December 2018, we entered into a severance agreement with Ms. Wood, or the Wood Severance Agreement, pursuant to which Ms. Wood may receive additional compensation in the event that Ms. Wood’s employment was terminated under certain conditions. See the discussion below under “Potential Payments Upon Termination or Change of Control.” In addition to the payment of severance amounts, the Wood Severance Agreement also provides that to the extent that any benefit distributable pursuant to the terms of the Wood Severance Agreement would be subject to the excise tax imposed under Section 4999 of the IRC, then the total payments payable to Ms. Wood shall be reduced as set forth in the Wood Severance Agreement (but not below zero) so that the maximum amount of such payments (after the reduction) shall be one dollar ($1.00) less than the amount which would cause such payments to be subject to the excise tax.

John T. BurnsDragan Cicic, M.D.

Effective December 30, 2017,January 2, 2020, we entered into an employment letter agreement with Mr. Burns, or the 2017 Burns Agreement.Cicic. Under this agreement, Mr. BurnsCicic is entitled to an annual base salary of $235,000$330,000 (subject to review and adjustment in the discretion of the Board of Directors or the compensation committee)Compensation Committee) and a discretionary annual cash bonus, with a target amount of up to 30% of Mr. Burns’sCicic’s then-effective base salary (subject to continued employment and the achievement of certain performance objectives established by our Board or compensation committee)Compensation Committee).

In January 2021, the target amount was increased to 35%. Mr. Burns’sCicic’s employment letter agreement does not have a specified term and either party may terminate Mr. Burns’sCicic’s employment agreement by providing written notice at any time, with or without cause. The employment letter agreement also provides that Mr. Burns may receive additional compensation in the event that Mr. Burns’s employment was terminated under certain conditions.

In connection with Mr. Cicic’s hiring, we granted to Mr. Cicic incentive stock options to purchase up to 35,000 shares of our common stock. The option has an exercise price equal to the market price of our common stock upon the date of grant and vests as to one quarter after one year from grant and with the remainder over 36 equal monthly installments thereafter, so that the option will be fully vested and exercisable four years from the date of grant.

Outstanding Equity Awards At 20192020 Fiscal Year-End

The following table discloses certain information regarding all outstanding equity awards at fiscal year-end for each of the officers named in the Summary Compensation Table.

Potential Payments Upon Termination or Change of Control

Angelos M. Stergiou

Potential Payments Made Upon Termination with Cause or Without Good Reason. The 2019 Stergiou Agreement provides that if Dr. Stergiou employment is terminated with cause by us, or by Dr. Stergiou without good reason, we will pay Dr. Stergiou all his accrued benefits, and all other rights and benefits of Dr. Stergiou will terminate upon such termination, except for any right to the continuation of benefits otherwise provided by law.

Potential Payments Made Upon Termination Without Cause or for Good Reason. The 2019 Stergiou Agreement provides that if we terminate Dr. Stergiou’s employment without cause or Dr. Stergiou resigns for good reason, we will pay Dr. Stergiou the following amounts in equal installments over a defined 12 month period: (i) an amount equal to 18 months of his then-current base salary, less standard employment-related withholdings and deductions and (ii) an amount equal to a pro-rated portion of his annual short-term incentive compensation for the year in which his employment terminates, without regard to whether the performance goals with respect to such bonus have been established or met and less standard employment-related withholdings and deductions. In addition, Dr. Stergiou will be entitled, if he so elects, to receive reimbursement for Consolidated Omnibus Budget Reconciliation Act of 1986 (“COBRA”) monthly premiums for a specified period of time.

Potential Payments Upon Termination Related to Change in Control.The 2019 Stergiou Agreement provides that if we terminate Dr. Stergiou’s employment without cause or he resigns for good reason within a one month period prior to or one year following a change in control we will pay him the following amounts in equal installments over a 12 month period: (i) an amount equal to 24 months of his then-current Base Salary, less standard employment-related withholdings and deductions; and (ii) an amount equal to one and one-half times his target bonus for the year in which his employment terminates, without regard to whether the performance goals with respect to such target bonus have been established or met and less standard employment-related with holdings and deductions. In addition, Dr. Stergiou will be entitled, if he so elects, to receive reimbursement for COBRA monthly premiums for a specified period of time. Furthermore, the vesting of all of his equity awards will immediately vest in full and become exercisable as of the date of termination.

Barbara A. Wood

Potential Payments Made Upon Termination Without Cause or for Good Reason.Pursuant to the terms of the Wood Severance Agreement, in the event that Ms. Wood’s employment is terminated by us without cause or by Ms. Wood for good reason, we will pay Ms. Wood the following amounts in equal installments over a 12- month period: (i) an amount equal to 12 months of the then-current base salary, less standard employment-related withholdings and deductions, and (ii) an amount equal to a pro-rated portion of Ms. Wood annual short-term incentive compensation for the year in which the employment terminates, without regard to whether the performance goals with respect to such bonus have been have been established or met and less standard employment-related withholdings and deductions. In addition, Ms. Wood will be entitled, if she so elects, to receive reimbursement for COBRA monthly premiums for a specified period of time.

Potential Payments Upon Termination Related to Change in Control.The Wood Severance Agreement provides that if we terminate Ms. Wood’s employment without cause or she resigns for good reason within one year following a change in control we will pay her the following amounts in equal installments over a 18 month period: (i) an amount equal to 18 months of her then-current Base Salary, less standard employment-related withholdings and deductions; and (ii) an amount equal to her target bonus for the year in which her employment terminates, without regard to whether the performance goals with respect to such target bonus have been established or met and less standard employment-related with holdings and deductions. In addition, Ms. Wood will be entitled, if she so elects, to receive reimbursement for COBRA monthly premiums for a specified period of time.

John T. Burns

Potential Payments Made Upon Termination Without Cause or for Good Reason. The 2017 Burns Agreement provides that if we terminate Mr. Burns’s employment without cause or Mr. Burns resigns for good reason, we will pay Mr. Burns the  continuing severance pay at a rate equal to one hundred percent (100%) of Employee’s Base Salary, as then in effect (less applicable withholding), for a period of nine (9) months from the effective date of such termination, to be paid periodically in accordance with the Company’s normal payroll practices.

Director Compensation

The following table shows the total compensation paid or accrued during the fiscal year ended December 31, 20192020 to each of our non-employee directors. Directors who are employed by us are not compensated for their service on our Board of Directors.

Director Compensation Policy

Our Board and its compensation committeethe Compensation Committee have adopted the following compensation for our directors:

Securities Authorized for Issuance Under Equity Compensation Plans

The following table provides certain aggregate information with respect to all of the Company’s equity compensation plans in effect as of December 31, 2019.2020.

Equity Compensation Plan Information as of December 31, 20192020

Related Person Transactions Policy and Procedures

We have adopted a written Related Person Transactions and SEC Compliance Policy that sets forth our policies and procedures regarding the identification, review, consideration and approval or ratification of “related persons transactions.” For purposes of our policy only, a “related person transaction” is a transaction, arrangement or relationship (or any series of similar transactions, arrangements or relationships) in which we and any “related person” are participants involving an amount that exceeds $120,000. Transactions involving compensation for services provided to us as an employee, director, consultant or similar capacity by a related person are not covered by this policy. A related person is any executive officer, director, or more than 5% stockholder, including any of their immediate family members, and any entity owned or controlled by such persons.

Under the policy, where a transaction has been identified as a related person transaction, management must present information regarding the proposed related person transaction to our Audit Committee (or, where Audit Committee approval would be inappropriate, to another independent body of our Board) for consideration and approval or ratification. The presentation must include a description of, among other things, the material facts, the interests, direct and indirect, of the related persons, the benefits of the transaction to us and whether any alternative transactions were available. To identify related person transactions in advance, we rely on information supplied by our executive officers, directors and certain significant stockholders. In considering related person transactions, our Audit Committee takes into account the relevant available facts and circumstances including, but not limited to (a) the risks, costs and benefits to us, (b) the impact on a director’s independence in the event the related person is a director, immediate family member of a director or an entity with which a director is affiliated, (c) the terms of the transaction, (d) the availability of other sources for comparable services or products and (e) the terms available to or from, as the case may be, unrelated third parties or to or from employees generally. In the event a director has an interest in the proposed transaction, the director must recuse himself or herself form the deliberations and approval. The policy requires that, in determining whether to approve, ratify or reject a related person transaction, our Audit Committee consider, in light of known circumstances, whether the transaction is in, or is not inconsistent with, our best interests and those of our stockholders, as our Audit Committee determines in the good faith exercise of its discretion.

DELINQUENT SECTION 16(a) REPORTS

Our records reflect that all reports which were required to be filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, as amended, were filed on a timely basis.

PROPOSAL 1

ELECTION OF DIRECTORS

Our Board of Directors currently consists of five members, classified into three classes as follows: (1) Jane Wasman and Robert Van Nostrand and John Varian are members of Class I with a term ending at the 2020 Annual Meeting;2023 annual meeting; (2) David A. Scheinberg is thea member of Class II with a term ending at the 2021 annual meeting;Annual Meeting; and (3) Angelos M. Stergiou is a memberand John Varian are members of Class III with a term ending at the 2022 annual meeting. At each annual meeting of stockholders, directors are elected for a full term of three years to succeed those directors whose terms are expiring. Our Board of Directors is nominating Jane Wasman, Robert Van Nostrand and John VarianDavid A. Scheinberg for election at the 20202021 Annual Meeting as a Class I directorsII director to serve for a term of three years until their respectivehis death, resignation or removal pursuant to our Bylaws.

In order to more evenly divide the classes of directors, and consistent with our Bylaws, John Varian has agreed that, if he is reelected at the 2020 Annual Meeting as a Class I director, he will resign from his Class I director seat, and the Board will simultaneously appoint him to a newly created directorship in Class III.  As a result, Mr. Varian would be up for reelection with other Class III directors at the 2022 annual meeting, rather than with the Class I directors at the 2023 annual meeting.

Unless authority to vote for these nomineesthis nominee is withheld, the shares represented by proxies solicited by the enclosed proxyBoard will be voted “FOR” the election of the foregoing Class I directors.II director. In the event that any of the foregoing nomineesnominee becomes unable or unwilling to serve, the shares represented by proxies solicited by the enclosed proxyBoard will be voted for the election of such other person as our Board of Directors may recommend in that nominee’s place. We have no reason to believe that any of the foregoing nomineesnominee will be unable or unwilling to serve as directors.a director.

THE board of directors UNANIMOUSYUNANIMOUSLY Recommends The Election Of JANE WASMAN, ROBERT VAN NOSTRAND AND JOHN VARIANDAVID A. SCHEINBERG As A CLASS I DirectorS,II Director, And Proxies Solicited By Our board of directors Will Be Voted In Favor Thereof Unless A Stockholder Has Indicated Otherwise On The Proxy.

PROPOSAL 2

RATIFICATION OF APPOINTMENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Audit Committee of our Board has appointed Moss Adams LLP, or Moss Adams, as our independent registered public accounting firm for the fiscal year ended December 31, 20202021 and has further directed that management submit the appointment of its independent registered public accounting firm for ratification by the stockholders at the 20202021 Annual Meeting.

Moss Adams currently serves as our independent registered public accounting firm and audited our financial statements for the year ended December 31, 2019.2020. Moss Adams has served as our auditors since 2018. Moss Adams does not have and has not had any financial interest, direct or indirect, in our Company, and does not have and has not had any connection with our company except in its professional capacity as our independent auditors.

Our Audit Committee and our Board believe that the continued retention of Moss Adams to serve as our independent registered public accounting firm is in the best interests of the Company and its stockholders. As a matter of good corporate governance, we are asking stockholders to ratify such appointment. If this appointment is not ratified at the 20202021 Annual Meeting, the Audit Committee intends to reconsider its selection of Moss Adams. Even if the appointment is ratified, the Audit Committee in its sole discretion may direct the appointment of a different independent registered public accounting firm at any time during the fiscal year if the Audit Committee determines that such a change would be in the best interests of our company and its stockholders.

Audit and non-audit services to be provided by Moss Adams are subject to the prior approval of the Audit Committee. In general, the Audit Committee’s policy is to grant such approval where it determines that the non-audit services are not incompatible with maintaining the independent registered public accounting firm’s independence and there are costs or other efficiencies in obtaining such services from the independent registered public accounting firm as compared to other possible providers. Representatives of Moss Adams are expected to be present at the 20202021 Annual Meeting, will have an opportunity to make a statement if they desire to do so, and will be available to respond to questions.

Our Audit Committee is directly responsible for appointing, compensating and providing oversight of the performance of our independent registered public accounting firm for the purpose of issuing audit reports and related work regarding our financial statements and the effectiveness of our internal control over financial reporting. The Audit Committee is also responsible for approving the audit feeand non-audit fees of our independent registered public accounting firm. In order to assure continuing auditor independence, the Audit Committee periodically considers whether there should be a regular rotation of the independent registered public accounting firm.

“FOR” votes from holders of a majority of the shares present in person or represented by proxy and entitled to vote on the matter at the 20202021 Annual Meeting that cast votes is required to ratify the appointment of Moss Adams. Abstentions and broker non-votes will count towards a quorum but will have no effect on the outcome of this Proposal 2.

Principal Accountant Fees and Services

The following table represents aggregate fees billed to us for the years ended December 31, 20192020 and 2018,2019, by Moss Adams, our principal accountant.

All fees described above were pre-approved by the Audit Committee.

We furnished the foregoing disclosure to Moss Adams.

Pre-Approval Procedures

Our Audit Committee pre-approves of audit and non-audit services rendered by our independent registered public accounting firm, Moss Adams. Our Audit Committee pre-approves specified services in the defined categories of audit services, audit-related services and tax services up to specified amounts. Pre-approval may also be given as part of our Audit Committee’s approval of the scope of the engagement of the independent auditor or on an individual, explicit, case-by-case basis before the independent auditor is engaged to provide each service.

Our Audit Committee has determined that the rendering of services other than audit services by Moss Adams is compatible with maintaining the principal accountant’s independence.

THe board of directors UNAnIMOUSLY Recommends A Vote To Ratify The Appointment Of MOSS ADAmS As Our Independent Registered Public Accounting Firm, And Proxies Solicited By Our board of directors Will Be Voted In Favor Of Such Ratification Unless A Stockholder Indicates Otherwise On The Proxy.

PROPOSAL 3

TO APPROVE, ON A NON-BINDING, ADVISORY BASIS, THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

At our 2019 annual meeting of stockholders, the stockholders indicated their preference that we solicit a non-binding advisory vote on the compensation of our named executive officers, commonly referred to as a “say-on-pay vote,” every year. The Board of Directors adopted a policy that is consistent with that preference. In accordance with that policy, this year, we are again asking the stockholders to approve, on an advisory basis, the compensation of our named executive officers as disclosed in this proxy statement in accordance with SEC rules.

ThisAt our 2020 annual meeting of stockholders, we sought an advisory “say-on-pay” vote is not intendedon our Company’s executive compensation program.  The 2020 say-on-pay proposal was approved by approximately 58% of the votes cast. The votes cast against the 2020 say-on-pay proposal represented approximately 5% of the Company’s total outstanding shares and our research has indicated that the great majority of these votes against the 2020 say-on-pay proposal came from individual stockholders who submitted their votes anonymously. We have been unable to addressidentify any specific item of compensation, but rathervotes against the overall compensation2020 say-on-pay proposal submitted by institutional stockholders or other accredited investors. We take very seriously the views of our namedstockholders regarding our executive officerscompensation and we consider a 58% vote in favor of the philosophy, policies2020 say-on-pay proposal to be an unsatisfactory result. However, because of the nature of the votes cast against the proposal, we have not been able to engage more specifically with stockholders who submitted notable votes against the 2020 say-on-pay proposal.

 Our Compensation Committee and Management are committed to considering and being responsive to stockholder views on executive compensation. We continue to re-evaluate our pay practices describedand compensation programs with guidance from our independent compensation consultant, Radford. Additionally, during the last twelve months, Dr. Stergiou, together with other members of management, has periodically held meetings with stockholders and participated in this proxy statement. investor conferences which has provided him with the opportunity to understand stockholder views on the status of the Company’s clinical trial programs, financial performance, strategic business plans, corporate governance, executive compensation, and related subjects.

The summary compensation of our named executive officers subject to the vote is disclosed in the compensation tables and the related narrative disclosure contained in this Proxy Statement. We believe that ourOur Compensation Committee has adopted compensation policies and makes decisions which are focused on pay-for-performance principles, with the primary goal of strongly aligned with our stockholders’aligning the interests and effective in achieving the overall objectives of our executives and employees with the interests of our stockholders. The structure of the compensation program. Compensation ofprogram for our named executive officers is designed to enable us to attract and retain talented and experienced executives to lead us successfully in a competitive environment.

In response to receiving an approximately 56% positive say-on-pay vote at our 2019 Annual Meeting of Stockholders, we have conducted outreach to key shareholders to discuss our compensation programs. We have held telephonic meetings with certain of these key shareholders and, based on the feedback we have received, we are continuing to re-evaluate our pay practices and compensation programs with guidance from our independent compensation consultant, Radford.

Accordingly, our Board is asking the stockholders to indicate their support for the compensation of our named executive officers as described in this proxy statement by casting a non-binding advisory vote “FOR” the following resolution:

“RESOLVED, that the compensation paid to our named executive officers, as disclosed pursuant to Item 402 of Regulation S-K, including the compensation tables and narrative discussion is hereby APPROVED.”

Because the vote is advisory, it is not binding on the Board. Nevertheless, the views expressed by the stockholders, whether through this vote or otherwise, are important to management and the Board and, accordingly, our Board and our Compensation Committee intend to consider the results of this vote in making determinations in the future regarding executive compensation arrangements.

Advisory approval of this Proposal 3 requires that the proposal receive “FOR” votes from the holders of a majority of the shares present in personvoting online or represented by proxy and entitled to vote on the matter at the 20202021 Annual Meeting that cast votes with respect to this Proposal 3. Abstentions and broker non-votes will count towards a quorum but will have no effect on the outcome of this Proposal 3. Unless the Board decides to modify its policy regarding the frequency of soliciting advisory votes on the compensation of our named executive officers, the next scheduled say-on-pay vote will be at the 20212022 annual meeting of stockholders.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE TO APPROVE THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS, AND PROXIES SOLICITED BY OUR BOARD OF DIRECTORS WILL BE VOTED IN FAVOR OF SUCH APPROVAL UNLESS A STOCKHOLDER INDICATES OTHERWISE ON THE PROXY.

PROPOSAL 4

TO APPROVE THE 2021 EMPLOYEE STOCK PURCHASE PLAN

On April 22, 2021, our Board unanimously approved, subject to stockholder approval at the meeting, the adoption of the 2021 Employee Stock Purchase Plan (the “ESPP”).  The ESPP provides eligible employees with the opportunity to purchase shares of our common stock at a discount, on a tax-favored basis, through regular payroll deductions in compliance with Section 423 of the IRC.

The ESPP is being submitted to stockholders for approval at the meeting in order to ensure favorable federal income tax treatment under Section 423 of the IRC for purchases of shares by our employees under the ESPP.

The ESPP allows all of the full-time and certain part-time employees of the Company to purchase shares of our common stock at a discount to fair market value.  Employees will purchase shares in September and March of each year using funds deducted from their paychecks during the preceding six months. The ESPP is expected to be an important component of the benefits package that we offer to our employees. We believe that the ESPP will aid us in retaining existing employees, recruiting and retaining new employees and aligning and increasing the interest of all employees in our success.

Our Board believes it is in the best interest of the Company and its stockholders that the ESPP be approved. If approved, eligible employees who elect to participate in the ESPP will first be granted options to purchase common stock under the ESPP on September 15, 2021.

Summary of Material Features of the ESPP

The following description of the material features of the ESPP is intended to be a summary only.  This summary is qualified in its entirety by the full text of the ESPP that is attached to this proxy statement as Appendix A.

Administration. The ESPP will be administered under the direction of the Compensation Committee. The Compensation Committee has authority to interpret the ESPP and to make all other determinations necessary or advisable in administering it.

Eligibility. All full-time employees and certain part-time employees who have been continuously employed for at least one month prior to an offering date will be eligible to participate in the ESPP. For part-time employees to be eligible, they must have customary employment of more than five months in any calendar year and more than 20 hours per week. However, no employee shall be eligible to participate to the extent that, immediately after the grant, (i) that employee would own stock and/or options or securities to purchase stock possessing 5% or more of the combined voting power or the value of all classes of our stock, or (ii) his or her rights to purchase stock under all of our employee stock purchase plans accrues at a rate that exceeds $25,000 for each calendar year in which such rights are outstanding and exercisable.  All of our employees will be eligible to participate in the ESPP. Participation in the ESPP is at the election of each eligible employee and the amounts received by a participant under the ESPP depend on the fair market value of our common stock on future dates; therefore, the benefits or amounts that will be received by any participant if the ESPP is approved by our stockholders, are not currently determinable.

Shares Available for Issuance. Assuming the ESPP is approved by our stockholders at the meeting, there will be 300,000 shares of our common stock available for issuance under the ESPP.

Participation. To participate in the ESPP, an eligible employee authorizes payroll deductions in an amount not less than 1% nor greater than 20% of his or her “eligible earnings” (i.e., regular rate of salary or wages, including overtime pay but not including incentive payments, bonuses, commissions or other additional payments) for each full payroll period in the offering period. The maximum number of shares of common stock that may be purchased by any participant during an offering period shall equal the lesser of 5,000 shares or $25,000 divided by the fair market value of our common stock on the first day of an offering period.  To ensure that IRS share limitations are not exceeded, we do not accept contributions from an individual participant in excess of $25,000 per calendar year.

Purchases. Eligible employees enroll in a six-month offering period during the open enrollment period prior to the start of that offering period. A new offering period begins approximately every September 15 and March 15.  At the end of each offering period, the accumulated deductions are used to purchase shares of our common stock from us during an offering period.  Shares are purchased at a price equal to 85% of the lower of the fair market value of our common stock on the first business day or the last business day of an offering period. On April 22, 2021, the closing market price per share of our common stock was $7.75 as reported by the Nasdaq Stock Market.

Termination of Employment. If a participating employee voluntarily resigns or is terminated by the Company prior to the last day of an offering period, the employee’s option to purchase terminates and the amount in the employee’s account is returned to the employee.

Transferability. Neither contributions credited to a participant’s account nor any rights with regard to the exercise of an option or to receive shares under the ESPP may be assigned, transferred, pledged or otherwise disposed of in any way (other than by will, the laws of descent or distribution to a designated beneficiary upon the participant’s death) by the participant.

Adjustments upon Change in Capitalization. Subject to any required action by our stockholders, the number of shares of common stock covered by unexercised options under the ESPP, the number of shares of common stock which have been authorized for issuance under the ESPP but are not yet subject to options, the maximum number of shares of common stock that may be purchased by a participant in an offering period, as well as the price per share of common stock covered by each unexercised option under the ESPP, shall be proportionately adjusted for any increase or decrease in the number of issued shares of common stock resulting from a stock split, reverse stock split, stock dividend, combination or reclassification of the common stock.

In the event of the proposed dissolution or liquidation of the Company, any offering period then in progress will terminate immediately prior to the consummation of such proposed action, unless otherwise provided by our Board.  In the event of a proposed sale of all or substantially all of the assets of the Company, or merger, consolidation or other capital reorganization of the Company with or into another corporation, each option outstanding under the ESPP shall be assumed or an equivalent option shall be substituted by such successor corporation unless our Board determines, in its sole discretion and in lieu of assumption or substitution, to shorten an offering period then in progress.

Participation Adjustment. If the number of unsold shares that are available for purchase under the ESPP is insufficient to permit exercise of all rights deemed exercised by all participating employees, a participation adjustment will be made, and the number of shares purchasable by all participating employees will be reduced proportionately. Any funds remaining in a participating employee’s account after such exercise are refunded to the employee, without interest.

Amendment. Our Board may amend the ESPP at any time and in any respect unless stockholder approval of the amendment in question is required under Section 423 of the IRC, any national securities exchange or system on which our common stock is then listed or reported, or under any other applicable laws, rules, or regulations.

Termination. Our Board may terminate the ESPP at any time and for any reason or for no reason, provided that no termination shall impair any rights of participating employees that have vested at the time of termination. Without further action of our Board, the ESPP shall terminate on April 22, 2031 or, if earlier, at such time as all shares of our common stock that may be made available for purchase under the ESPP have been issued.

Federal Income Tax Consequences

The ESPP, and the rights of participant employees to make purchases thereunder, qualify for treatment under the provisions of Sections 421 and 423 of the IRC. Under these provisions, no income will be taxable to a participant until the shares purchased under the ESPP are sold or otherwise disposed of.

Upon sale or other disposition of the shares, the participant will generally be subject to tax and the amount of the tax will depend upon the holding period. If the shares are sold or otherwise disposed of more than two years from the first day of the relevant offering period (and more than one year from the date the shares are purchased), then the participant generally will recognize ordinary income measured as the lesser of:

Any additional gain should be treated as long-term capital gain.

If the shares are sold or otherwise disposed of before the expiration of this holding period, the participant will recognize ordinary income at the time of such disposition generally measured as the excess of the fair market value of the shares on the date the shares are purchased over the purchase price. Any additional gain or loss on such sale or disposition will be long-term or short-term capital gain or loss, depending on the holding period.

The Company is not entitled to a deduction for amounts taxed as ordinary income or capital gain to a participant except to the extent ordinary income is recognized by participants upon a sale or disposition of shares prior to the expiration of the holding period(s) described above.  In all other cases, no deduction is allowed to the Company.

The foregoing tax discussion is a general description of certain expected federal income tax results under current law. No attempt has been made to address any state, local, foreign or estate and gift tax consequences that may arise in connection with participation in the ESPP.

Vote Required

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 approval of the proposal.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE TO APPROVE THE 2021 EMPLOYEE STOCK PURCHASE PLAN, AND PROXIES SOLICITED BY OUR BOARD OF DIRECTORS WILL BE VOTED IN FAVOR OF SUCH APPROVAL UNLESS A STOCKHOLDER INDICATES OTHERWISE ON THE PROXY.

OTHER MATTERS

The Board, at the time of the preparation of this Proxy Statement, knows of no other matters to come before the 20202021 Annual Meeting other than thatthose referred to herein. If any other matters should properly come before the 20202021 Annual Meeting, the persons named in the proxy cardacting as proxies will have discretionary authority to vote all proxies in accordance with his or hertheir best judgment.

By Order of the Board of Directors

Barbara A. Wood

Executive Vice President, General Counsel

and Corporate Secretary

 APPENDIX A

2021 EMPLOYEE STOCK PURCHASE PLAN

SELLAS LIFE SCIENCES GROUP, INC.

EMPLOYEE STOCK PURCHASE PLAN

The following constitute the provisions of the 2021 Employee Stock Purchase Plan (the “Plan”) of Sellas Life ScienceSciences Group, Inc. (the “Company”).

1.            Purpose. The purpose of the Plan is to provide Employees of the Company and its Designated Subsidiaries with an opportunity to purchase Common Stock of the Company. It is the intention of the Company to have the Plan qualify as an “Employee Stock Purchase Plan” under Section 423 of the Code. The provisions of the Plan shall, accordingly, be construed so as to extend and limit participation in a manner consistent with the requirements of that section of the Code.

2.            Definitions.

(a)               “Board” shall mean the Board of Directors of the Company, or a committee of the Board of Directors named by the Board to administer the Plan.

(b)               “Code” shall mean the Internal Revenue Code of 1986, as amended, including any successor statute, regulation and guidance thereto.

(c)               “Common Stock” shall mean the common stock, $0.0001 par value per share, of the Company.

(d)               “Company” shall mean Sellas Life Sciences Group, Inc., a Delaware corporation.

(e)               “Compensation” shall mean the regular rate of salary or wages received by the Employee from the Company or a Designated Subsidiary that is taxable income for federal income tax purposes or applicable tax law, including payments for overtime and shift premium, but excluding incentive compensation, incentive payments, bonuses, commissions, relocation, expense reimbursements, tuition or other reimbursements or compensation received from the Company or a Designated Subsidiary.

(f)                “Continuous Status as an Employee” shall mean the absence of any interruption or termination of service as an Employee. Continuous Status as an Employee shall not be considered interrupted in the case of a leave of absence agreed to in writing by the Company, provided that such leave is for a period of not more than ninety (90) days or reemployment upon the expiration of such leave is guaranteed by contract or statute.

(g)               “Contributions” shall mean all amounts credited to the account of a participant pursuant to the Plan.

(h)               “Designated Subsidiaries” shall mean the Subsidiaries which have been designated by the Board from time to time in its sole discretion as eligible to participate in the Plan.

(i)                “Employee” shall mean any person who is employed by the Company or one of its Designated Subsidiaries for tax purposes and who is customarily employed for at least twenty (20) hours per week and more than five (5) months in a calendar year by the Company or one of its Designated Subsidiaries.

(j)                “Exercise Date” shall mean the last business day of each Offering Period of the Plan.

(k)               “Exercise Price” shall mean with respect to an Offering Period, an amount equal to 85% of the fair market value (as defined in Section 7(b)) of a share of Common Stock on the Offering Date or on the Exercise Date, whichever is lower.

(l)                 “Offering Date” shall mean the first business day of each Offering Period of the Plan.

(m)              “Offering Period” shall mean a period of six months as set forth in Section 4 of the Plan.

(n)               “Plan” shall mean this Sellas Life Sciences Group, Inc. Employee Stock Purchase Plan.

(o)              “Subsidiary” shall mean a corporation, domestic or foreign, of which not less than 50% of the voting shares are held by the Company or a Subsidiary, whether or not such corporation now exists or is hereafter organized or acquired by the Company or a Subsidiary.

3.            Eligibility.

(a)              Any person who has been continuously employed as an Employee for one (1) month as of the Offering Date of a given Offering Period shall be eligible to participate in such Offering Period under the Plan and further, subject to the requirements of Section 5(a) and the limitations imposed by Section 423(b) of the Code. All Employees granted options under the Plan with respect to any Offering Period will have the same rights and privileges except for any differences that may be permitted pursuant to Section 423.

(b)              Any provisions of the Plan to the contrary notwithstanding, no Employee shall be granted an option under the Plan (i) if, immediately after the grant, such Employee (or any other person whose stock would be attributed to such Employee pursuant to Section 424(d) of the Code) would own stock and/or hold outstanding options to purchase stock possessing five percent (5%) or more of the total combined voting power or value of all classes of stock of the Company or of any Subsidiary of the Company or (ii) which permits his or her rights to purchase stock under all employee stock purchase plans (described in Section 423 of the Code) of the Company and its Subsidiaries to accrue at a rate which exceeds $25,000 of fair market value of such stock as defined in Section 7(b) (determined at the time such option is granted) for each calendar year in which such option is outstanding at any time. In addition, the maximum number of shares of Common Stock that may be purchased by any participant during an Offering Period shall equal the lesser of (i) 5,000 shares of Common Stock or (ii) $25,000 divided by the fair market value of the Common Stock on the first trading day of such Offering Period, which price shall be adjusted if the price per share is adjusted pursuant to Section 18. Any option granted under the Plan shall be deemed to be modified to the extent necessary to satisfy this Section 3(b).

4.            Offering Periods. The Plan shall be implemented by a series of Offering Periods, with a new Offering Period commencing on March 15 and September 15 of each year or the first business day thereafter (or at such other time or times as may be determined by the Board).

5.            Participation.

(a)               An eligible Employee may become a participant in the Plan by completing an Enrollment Form provided by the Company and filing it with the Company or its designee at least ten (10) days prior to the applicable Offering Date, unless a later time for filing the Enrollment Form is set by the Board for all eligible Employees with respect to a given Offering Period. The Enrollment Form and its submission may be electronic as directed by the Company. The Enrollment Form shall set forth the percentage of the participant’s Compensation (which shall be not less than one percent (1%) and not more than twenty percent (20%) to be paid as Contributions pursuant to the Plan.

(b)               Payroll deductions shall commence with the first payroll following the Offering Date, unless a later time is set by the Board with respect to a given Offering Period, and shall end on the last payroll paid on or prior to the Exercise Date of the Offering Period to which the Enrollment Form is applicable, unless sooner terminated as provided in Section 10.

6.            Method of Payment of Contributions.

(a)               Each participant shall elect to have payroll deductions made on each payroll during the Offering Period in an amount not less than one percent (1%) and not more than twenty percent (20%) of such participant’s Compensation on each such payroll (or such other percentage as the Board may establish from time to time before an Offering Date). All payroll deductions made by a participant shall be credited to his or her account under the Plan. A participant may not make any additional payments into such account.

A participant may discontinue his or her participation in the Plan as provided in Section 10, or, on one occasion only during the Offering Period, may decrease, but may not increase, the rate of his or her Contributions during the Offering Period by completing and filing with the Company a new Enrollment Form authorizing a change in the deduction rate. The change in rate shall be effective as of the beginning of the next payroll period following the date of filing of the new Enrollment Form, if the Enrollment Form is submitted at least ten (10) days prior to such date, and, if not, as of the beginning of the next succeeding payroll period.

(b)              Notwithstanding the foregoing, to the extent necessary to comply with Section 423(b)(8) of the Code and Section 3(b), a participant’s payroll deductions may be decreased to 0% at such time during any Offering Period which is scheduled to end during the current calendar year that the aggregate of all payroll deductions accumulated with respect to such Offering Period and any other Offering Period ending within the same calendar year equals $21,250. Payroll deductions shall recommence at the rate provided in such participant’s Enrollment Form at the beginning of the first Offering Period which is scheduled to end in the following calendar year, unless terminated by the participant as provided in Section 10.

7.             Grant of Option.

(a)               On the Offering Date of each Offering Period, each eligible Employee participating in such Offering Period shall be granted an option to purchase on the Exercise Date of such Offering Period a number of shares of the Common Stock determined by dividing such Employee’s Contributions accumulated prior to such Exercise Date and retained in the participant’s account as of the Exercise Date by the applicable Exercise Price; provided however, that such purchase shall be subject to the limitations set forth in Sections 3(b) and 12. The fair market value of a share of the Common Stock shall be determined as provided in Section 7(b).

(b)               The fair market value of the Common Stock on a given date shall be (i) if the Common Stock is listed on a national securities exchange or traded in the over-the-counter market and sales prices are regularly reported for the Common Stock, the closing or last sale price of the Common Stock for such date (or, in the event that the Common Stock is not traded on such date, on the immediately preceding trading date), on the composite tape or other comparable reporting system; or (ii) if the Common Stock is not listed on a national securities exchange and such price is not regularly reported, the mean between the bid and asked prices per share of the Common Stock at the close of trading in the over-the-counter market.

8.            Exercise of Option. Unless a participant withdraws from the Plan as provided in Section 10, his or her option for the purchase of shares will be exercised automatically on the Exercise Date of the Offering Period, and the maximum number of full shares subject to the option will be purchased for him or her at the applicable Exercise Price with the accumulated Contributions in his or her account. If a fractional number of shares results, then such number shall be rounded down to the next whole number and any unapplied cash shall be carried forward to the next Exercise Date, unless the participant requests a cash payment. The shares purchased upon exercise of an option hereunder shall be deemed to be transferred to the participant on the Exercise Date. During a participant’s lifetime, a participant’s option to purchase shares hereunder is exercisable only by him or her.

9.            Delivery. Upon the written request of a participant, certificates representing the shares purchased upon exercise of an option will be issued as promptly as practicable after the Exercise Date of each Offering Period to participants who wish to hold their shares in certificate form, except that the Board may determine that such shares shall be held for each participant’s benefit by a broker designated by the Board. Any payroll deductions accumulated in a participant’s account which are not sufficient to purchase a full Share shall be retained in the participant’s account for the subsequent Offering Period, subject to earlier withdrawal by the participant as provided in Section 10 below. Any other amounts left over in a participant’s account after an Exercise Date shall be returned to the participant.

10.          Withdrawal; Termination of Employment. A participant may withdraw all but not less than all the Contributions credited to his or her account under the Plan at any time prior to the Exercise Date of the Offering Period by giving written notice to the Company or its designee. All of the participant’s Contributions credited to his or her account will be paid to him or her promptly after receipt of his or her notice of withdrawal and his or her option for the current period will be automatically terminated, and no further Contributions for the purchase of shares will be made during the Offering Period.

(a)               Upon termination of the participant’s Continuous Status as an Employee prior to the Exercise Date of the Offering Period for any reason, including retirement or death, the Contributions credited to his or her account will be returned to him or her or, in the case of his or her death, to the person or persons entitled thereto under Section 14, and his or her option will be automatically terminated.

(b)               In the event an Employee fails to remain in Continuous Status as an Employee for at least 20 hours per week during the Offering Period in which the Employee is a participant, he or she will be deemed to have elected to withdraw from the Plan and the Contributions credited to his or her account will be returned to him or her and his or her option terminated.

A participant’s withdrawal from an Offering Period will not have any effect upon his or her eligibility to participate in a succeeding offering or in any similar plan which may hereafter be adopted by the Company.

11.          Interest. No interest shall accrue on the Contributions of a participant in the Plan.

12.          Stock.

(a)               The maximum number of shares of Common Stock which shall be made available for sale under the Plan shall be 300,000 shares, subject to adjustment upon changes in capitalization of the Company as provided in Section 18. If the total number of shares which would otherwise be subject to options granted pursuant to Section 7(a) on the Offering Date of an Offering Period exceeds the number of shares then available under the Plan (after deduction of all shares for which options have been exercised), the Company shall make a pro rata allocation of the shares remaining available for option grants in as uniform a manner as shall be practicable and as it shall determine to be equitable. Any amounts remaining in an Employee’s account not applied to the purchase of shares pursuant to this Section 12 shall be refunded on or promptly after the Exercise Date. In such event, the Company shall give written notice of such reduction of the number of shares subject to the option to each Employee affected thereby and shall similarly reduce the rate of Contributions, if necessary.

(b)               The participant will have no interest or voting right in shares covered by his or her option until such option has been exercised.

13.          Administration. The Board shall supervise and administer the Plan and shall have full power to adopt, amend and rescind any rules deemed desirable and appropriate for the administration of the Plan and not inconsistent with the Plan, to construe and interpret the Plan, to correct any defect or supply any omission or reconcile any inconsistency or ambiguity in the Plan and to make all other determinations necessary or advisable for the administration of the Plan, including without limitation, adopting subplans applicable to particular Designated Subsidiaries or locations, which subplans may be designed to be outside the scope of Section 423 of the Code..

14.          Designation of Beneficiary. A participant may designate a beneficiary who is to receive any shares and cash, if any, from the participant’s account under the Plan in the event of such participant’s death subsequent to the end of the Offering Period but prior to delivery to him or her of such shares and cash. In addition, a participant may designate a beneficiary who is to receive any cash from the participant’s account under the Plan in the event of such participant’s death prior to the Exercise Date of the Offering Period. If a participant is married and the designated beneficiary is not the spouse, spousal consent shall be required for such designation to be effective. Beneficiary designations shall be made either in writing or by electronic delivery as directed by the Company.

(a)               Such designation of beneficiary may be changed by the participant (and his or her spouse, if any) at any time by submission of the required notice, which may be electronic. In the event of the death of a participant and in the absence of a beneficiary validly designated under the Plan who is living at the time of such participant’s death, the Company shall deliver such shares and/or cash to the executor or administrator of the estate of the participant, or if no such executor or administrator has been appointed (to the knowledge of the Company), the Company, in its discretion, may deliver such shares and/or cash to the spouse or to any one or more dependents or relatives of the participant, or if no spouse, dependent or relative is known to the Company, then to such other person as the Company may designate.

15.          Transferability. Neither Contributions credited to a participant’s account nor any rights with regard to the exercise of an option or to receive shares under the Plan may be assigned, transferred, pledged or otherwise disposed of in any way (other than by will, the laws of descent and distribution or as provided in Section 14) by the participant. Any such attempt at assignment, transfer, pledge or other disposition shall be without effect, except that the Company may treat such act as an election to withdraw funds in accordance with Section 10.

16.          Use of Funds. All Contributions received or held by the Company under the Plan may be used by the Company for any corporate purpose, and the Company shall not be obligated to segregate such Contributions.

17.          Reports. Individual accounts will be maintained for each participant in the Plan. Statements of account will be given to participating Employees promptly following the Exercise Date, which statements will set forth the amounts of Contributions, the per share purchase price, the number of shares purchased and the remaining cash balance, if any.

18.          Adjustments upon Changes in Capitalization. Subject to any required action by the stockholders of the Company, the number of shares of Common Stock covered by unexercised options under the Plan and the number of shares of Common Stock which have been authorized for issuance under the Plan but are not yet subject to options under Section 12(a) (collectively, the “Reserves”), the maximum number of shares of Common Stock that may be purchased by a participant in an Offering Period set forth in Section 3(b) as well as the price per share of Common Stock covered by each unexercised option under the Plan, shall be proportionately adjusted for any increase or decrease in the number of issued shares of Common Stock resulting from a stock split, reverse stock split, stock dividend, combination or reclassification of the Common Stock. Such adjustment shall be made by the Board, whose determination in that respect shall be final, binding and conclusive.

In the event of the proposed dissolution or liquidation of the Company, an Offering Period then in progress will terminate immediately prior to the consummation of such proposed action, unless otherwise provided by the Board. In the event of a proposed sale of all or substantially all of the assets of the Company, or the merger, consolidation or other capital reorganization of the Company with or into another corporation, each option outstanding under the Plan shall be assumed or an equivalent option shall be substituted by such successor corporation or a parent or subsidiary of such successor corporation, unless the Board determines, in the exercise of its sole discretion and in lieu of such assumption or substitution, to shorten the Offering Period then in progress by setting a new Exercise Date (the “New Exercise Date”). If the Board shortens the Offering Period then in progress in lieu of assumption or substitution in the event of a merger or sale of assets, the Board shall notify each participant in writing, at least ten days prior to the New Exercise Date, that the Exercise Date for his or her option has been changed to the New Exercise Date and that his or her option will be exercised automatically on the New Exercise Date, unless prior to such date he or she has withdrawn from the Offering Period as provided in Section 10. For purposes of this section, an option granted under the Plan shall be deemed to be assumed if, following the sale of assets, merger or other reorganization, the option confers the right to purchase, for each share of Common Stock subject to the option immediately prior to the sale of assets, merger or other reorganization, the consideration (whether stock, cash or other securities or property) received in the sale of assets, merger or other reorganization by holders of Common Stock for each share of Common Stock held on the effective date of such transaction (and if such holders were offered a choice of consideration, the type of consideration chosen by the holders of a majority of the outstanding shares of Common Stock); provided, however, that if such consideration received in such transaction was not solely common stock of the successor corporation or its parent (as defined in Section 424(e) of the Code), the Board may, with the consent of the successor corporation, provide for the consideration to be received upon exercise of the option to be solely common stock of the successor corporation or its parent equal in fair market value to the per share consideration received by holders of Common Stock in the sale of assets, merger or other reorganization.

The Board may, if it so determines in the exercise of its sole discretion, also make provision for adjusting the Reserves, as well as the price per share of Common Stock covered by each outstanding option, in the event that the Company effects one or more reorganizations, recapitalizations, rights offerings or other increases or reductions of shares of its outstanding Common Stock, and in the event of the Company being consolidated with or merged into any other corporation.

19.          Amendment or Termination.

(a)               The Board may at any time terminate or amend the Plan. Except as provided in Section 18, no such termination may affect options previously granted, nor may an amendment make any change in any option theretofore granted which adversely affects the rights of any participant provided that an Offering Period may be terminated by the Board on an Exercise Date or by the Board’s setting a new Exercise Date with respect to an Offering Period then in progress if the Board determines that termination of the Offering Period is in the best interests of the Company and the stockholders or if continuation of the Offering Period would cause the Company to incur adverse accounting charges in the generally-accepted accounting rules applicable to the Plan. In addition, to the extent necessary to comply with Section 423 of the Code (or any successor rule or provision or any applicable law or regulation), the Company shall obtain stockholder approval in such a manner and to such a degree as so required.

(b)               Without stockholder consent and without regard to whether any participant rights may be considered to have been adversely affected, the Board shall be entitled to change the Offering Periods, limit the frequency and/or number of changes in the amount withheld during an Offering Period, establish the exchange ratio applicable to amounts withheld in a currency other than U.S. dollars, permit payroll withholding in excess of the amount designated by a participant in order to adjust for delays or mistakes in the Company’s processing of properly completed withholding elections, establish reasonable waiting and adjustment periods and/or accounting and crediting procedures to ensure that amounts applied toward the purchase of Common Stock for each participant properly correspond with amounts withheld from the participant’s Compensation, and establish such other limitations or procedures as the Board determines in its sole discretion advisable that are consistent with the Plan.

20.          Notices. All notices or other communications by a participant to the Company under or in connection with the Plan shall be deemed to have been duly given when received in the form specified by the Company at the location, or by the person, designated by the Company for the receipt thereof.

21.          Conditions upon Issuance of Shares. Shares shall not be issued with respect to an option unless the exercise of such option and the issuance and delivery of such shares pursuant thereto shall comply with all applicable provisions of law, domestic or foreign, including, without limitation, the Securities Act of 1933, as amended, the Securities Exchange Act of 1934, as amended, the rules and regulations promulgated thereunder, and the requirements of any stock exchange upon which the shares may then be listed, and shall be further subject to the approval of counsel for the Company with respect to such compliance.

As a condition to the exercise of an option, the Company may require the person exercising such option to represent and warrant at the time of any such exercise that the shares are being purchased only for investment and without any present intention to sell or distribute such shares if, in the opinion of counsel for the Company, such a representation is required by any of the aforementioned applicable provisions of law.

22.          Information Regarding Disqualifying Dispositions. By electing to participate in the Plan, each participant agrees to provide any information about any transfer of shares of Common Stock acquired under the Plan that occurs within two years after the first business day of the Offering Period in which such shares were acquired as may be requested by the Company or any Subsidiaries in order to assist it in complying with the tax laws.

23.          Right to Terminate Employment. Nothing in the Plan or in any agreement entered into pursuant to the Plan shall confer upon any Employee the right to continue in the employment of the Company or any Subsidiary, or affect any right which the Company or any Subsidiary may have to terminate the employment of such Employee.

24.          Rights as a Stockholder. Neither the granting of an option nor a deduction from payroll shall constitute an Employee the owner of shares covered by an option. No Employee shall have any right as a stockholder unless and until an option has been exercised, and the shares underlying the option have been registered in the Company’s share register.

25.          Term of Plan. The Plan became effective upon its adoption by the Board on April 22, 2021 and shall continue in effect through April 22, 2031, unless sooner terminated under Section 19.

26.          Applicable Law. This Plan shall be governed in accordance with the laws of the State of Delaware, applied without giving effect to any conflict-of-law principles.

1 U P X 01 - Jane Wasman 02 - John Varian 03 - Robert Van Nostrand For Withhold For WithholdDavid A. Scheinberg For Withhold 3. To approve, on a non-binding advisory basis, the compensation of our Named Executive Officers. This proposal callsThese proposals call for a non-binding, 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. 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, 2020.2021. 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. Using a black ink pen, mark your votes with an X as shown in this example. Please do not write outside the designated areas. 03927B + + Proposals — The Board of Directors recommends a votev A ote FOR all the nominees listed and FOR A Proposals 2, 3 and 3.4. Please sign exactly as your name(s) appear(s) hereon. All holders must sign. When signing in a fiduciary capacity, please indicate full title as such. If a corporation or partnership, please sign in full corporate or partnership name by authorized person. Date (mm/dd/yyyy) — Please print date below. Signature 1 — Please keep signature within the box. Signature 2 — Please keep signature within the box. B Authorized Signatures — This section must be completed for your vote to be counted. — Date and Sign Below q IFqIF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.q Annual Meeting Proxy Card 1. To Elect ThreeOne Class I Directors.II Director. 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 nomineesnominee for Class III director to be considered at the annual meeting are Jane Wasman, John Varian and Robert Van Nostrand.is David A. Scheinberg. 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.II Director. For Against Abstain 4. To approve the 2021 Employee Stock Purchase Plan. Our Board of Directors unanimously approved the adoption of the 2021 Employee Stock Purchase Plan (the “ESPP”). The ESPP provides eligible employees with the opportunity to purchase shares of our common stock at a discount, on a tax-favored basis, through regular payroll deductions in compliance with Section 423 of the IRC. We believe that the ESPP will aid us in retaining existing employees, recruiting and retaining new employees and aligning and increasing the interest of all employees in our success. 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 approval of the proposal 000004 MR A SAMPLE DESIGNATION (IF ANY) ADD 1 ADD 2 ADD 3 ADD 4 ADD 5 ADD 6 ENDORSEMENT_LINE______________ SACKPACK_____________ 1234 5678 9012 345 MMMMMMMMM MMMMMMMMMMMMMMM 4 5 8 0 2 3 8 8 MR A SAMPLE (THIS AREA IS SET UP TO ACCOMMODATE 140 CHARACTERS) MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND MR A SAMPLE AND C 1234567890 J N T C123456789 MMMMMMMMMMMM M MMMMMMM 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext 000000000.000000 ext If no electronic voting, delete QR code and control # Δ ≈ You may vote online or by phone instead of mailing this card. Online Go to www.envisionreports.com/SLS or scan the QR code — login details are located in the shaded bar below. Save paper, time and money! Sign up for electronic delivery at www.envisionreports.com/SLS Phone Call toll free 1-800-652-VOTE (8683) within the USA, US territories and Canada Votes submitted electronically must be received by 9:00 a.m., Eastern Daylight Time, on June 7, 2020. Your vote matters – here’s how to vote!

Small steps make an impact. Help the environment by consenting to receive electronic delivery, sign up at www.envisionreports.com/SLS PROXY FOR 20202021 ANNUAL MEETING OF STOCKHOLDERS THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS OF SELLAS LIFE SCIENCES GROUP, INC. AND MAY BE REVOKED BY THE STOCKHOLDER PRIOR TO ITS EXERCISE. The undersigned stockholder of SELLAS Life Sciences Group, Inc., a Delaware corporation, acknowledges receipt of the Notice of Annual Meeting of Stockholders and Proxy Statement, each dated April 22, 2020.23, 2021. The undersigned stockholder hereby also designates Angelos M. Stergiou, President and Chief Executive OfficeOfficer, Barbara A. Wood, Executive Vice President, Secretary and General Counsel, or any of them, as proxies and attorneys-in-fact, with full power to each other of substitution, on behalf and in the name of the undersigned, to represent the undersigned at the 20202021 Annual Meeting of Stockholders of SELLAS Life Sciences Group, Inc. to be held on Tuesday, June 9, 2020,8, 2021, at 8:30 a.m., EDT, at 15 West 38th Street, 4th Floor, New York, NY 10018virtually via the internet and at any adjournment thereof, and to vote all shares of Common Stock which the undersigned would be entitled to vote, if then and there personally present, on the matters set forth on the reverse side. THE SHARES PRESENTED BY THIS PROXY WILL BE VOTED AS DIRECTED, OR IF NO CONTRARY DIRECTION IS INDICATED, WILL BE VOTED “FOR” PROPOSALS 1, 2, 3 AND 3,4, AND AS SAID PROXIES (OR ANY OF THEM) DEEM ADVISABLE ON SUCH OTHER MATTERS AS MAY PROPERLY COME BEFORE THE MEETING OR ANY POSTPONEMENT OR ADJOURNMENT THEREOF. THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE “FOR” PROPOSALS 1, 2, 3 AND 3.4. CONTINUED AND TO BE SIGNED ON REVERSE SIDE Proxy — SELLAS Life Sciences Group, Inc. IFqIF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.ENVELOPE.q The 2021 Special Meeting of Stockholders of SELLAS Life Sciences Group, Inc. will be held on Tuesday, June 8, 2021 at 8:30 am local time, virtually via the internet at www.meetingcenter.io/287191590. To access the virtual meeting, you must have the information that is printed in the shaded bar located on the reverse side of this form. The password for this meeting is — SLS2021.

1 U P X 01 - David A. Scheinberg For Withhold 3. To approve, on a non-binding advisory basis, the compensation of our Named Executive Officers. These proposals call for a non-binding, 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. 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, 2021. 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. Using a black ink pen, mark your votes with an X as shown in this example. Please do not write outside the designated areas. + + Proposals — The Board of Directors recommends a v A ote FOR all the nominees listed and FOR Proposals 2, 3 and 4. Please sign exactly as your name(s) appear(s) hereon. All holders must sign. When signing in a fiduciary capacity, please indicate full title as such. If a corporation or partnership, please sign in full corporate or partnership name by authorized person. Date (mm/dd/yyyy) — Please print date below. Signature 1 — Please keep signature within the box. Signature 2 — Please keep signature within the box. B Authorized Signatures — This section must be completed for your vote to be counted. — Date and Sign Below qIF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.q Annual Meeting Proxy Card 1. To Elect One Class II Director. 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 nominee for Class II director to be considered at the annual meeting is David A. Scheinberg. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the foregoing Class II Director. 4. To approve the 2021 Employee Stock Purchase Plan. Our Board of Directors unanimously approved the adoption of the 2021 Employee Stock Purchase Plan (the “ESPP”). The ESPP provides eligible employees with the opportunity to purchase shares of our common stock at a discount, on a tax-favored basis, through regular payroll deductions in compliance with Section 423 of the IRC. We believe that the ESPP will aid us in retaining existing employees, recruiting and retaining new employees and aligning and increasing the interest of all employees in our success. 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 approval of the proposal MMMMMMMMM 5 0 2 3 8 8 MMMMMMMMMMMM

PROXY FOR 2021 ANNUAL MEETING OF STOCKHOLDERS THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS OF SELLAS LIFE SCIENCES GROUP, INC. AND MAY BE REVOKED BY THE STOCKHOLDER PRIOR TO ITS EXERCISE. The undersigned stockholder of SELLAS Life Sciences Group, Inc., a Delaware corporation, acknowledges receipt of the Notice of Annual Meeting of Stockholders and Proxy Statement, each dated April 23, 2021. The undersigned stockholder hereby also designates Angelos M. Stergiou, President and Chief Executive Officer, Barbara A. Wood, Executive Vice President, Secretary and General Counsel, or any of them, as proxies and attorneys-in-fact, with full power to each other of substitution, on behalf and in the name of the undersigned, to represent the undersigned at the 2021 Annual Meeting of Stockholders of SELLAS Life Sciences Group, Inc. to be held on Tuesday, June 8, 2021, at 8:30 a.m., EDT, virtually via the internet and at any adjournment thereof, and to vote all shares of Common Stock which the undersigned would be entitled to vote, if then and there personally present, on the matters set forth on the reverse side. THE SHARES PRESENTED BY THIS PROXY WILL BE VOTED AS DIRECTED, OR IF NO CONTRARY DIRECTION IS INDICATED, WILL BE VOTED “FOR” PROPOSALS 1, 2, 3 AND 4, AND AS SAID PROXIES (OR ANY OF THEM) DEEM ADVISABLE ON SUCH OTHER MATTERS AS MAY PROPERLY COME BEFORE THE MEETING OR ANY POSTPONEMENT OR ADJOURNMENT THEREOF. THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS A VOTE “FOR” PROPOSALS 1, 2, 3 AND 4. CONTINUED AND TO BE SIGNED ON REVERSE SIDE Proxy — SELLAS Life Sciences Group, Inc. qIF VOTING BY MAIL, SIGN, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.q