As filed with the Securities and Exchange Commission on August 14, 2020

Registration No. 333-  

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SELLAS Life Sciences Group, Inc.

(Exact name of registrant as specified in its charter)

7 Times Square, Suite 2503

New York, New York 10036

(917) 438-4353

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

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

President and Chief Executive Officer

7 Times Square, Suite 2503

New York, New York 10036

(917) 438-4353

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Joel I. Papernik, Esq.

Daniel A. Bagliebter, Esq.

Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.

666 Third Avenue

New York, New York 10017

(212) 935-3000

If the only securities being registered on this form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. ¨ 

If any of the securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. x 

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨ 

If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨ 

If this form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ¨ 

If this form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ¨ 

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company.  See the definitions of "large accelerated filer," "accelerated filer" "smaller reporting company" and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ¨ 

CALCULATION OF REGISTRATION FEE

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

The information in this prospectus is not complete and may be changed.  A registration statement relating to these securities has been filed with the Securities and Exchange Commission.  The selling stockholders may not sell these securities until the Securities and Exchange Commission declares the registration statement effective.  This prospectus is not an offer to sell these securities and is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED AUGUST 14, 2020

PROSPECTUS

5,488,156 Shares of Common Stock

The selling stockholders of SELLAS Life Sciences Group, Inc.  (“SELLAS,” “we,” “us” or the “Company”) listed beginning on page 8 of this prospectus may offer and resell under this prospectus (i) up to 2,744,078 shares of our Common Stock and (ii) up to 2,744,078 shares of our Common Stock issuable upon exercise of warrants acquired by certain of the selling stockholders under the Purchase Agreement (defined below) (the “Warrants”).  The selling stockholders acquired the shares of Common Stock and the Warrants from us pursuant to a Securities Purchase Agreement (the “Purchase Agreement”, dated July 31, 2020, by and among the Company and the investors listed therein (the “Investors”).

We are registering the resale of the shares of Common Stock covered by this prospectus as required by the Registration Rights Agreement we entered into with the Investors on July 31, 2020.  The selling stockholders will receive all of the proceeds from any sales of the shares offered hereby.  We will not receive any of the proceeds, but we will incur expenses in connection with the offering.  To the extent the Warrants are exercised for cash, if at all, we will receive the exercise price of the Warrants.

The selling stockholders may sell these shares through public or private transactions at market prices prevailing at the time of sale or at negotiated prices.  The timing and amount of any sale are within the sole discretion of the selling stockholders.  Our registration of the shares of Common Stock covered by this prospectus does not mean that the selling stockholders will offer or sell any of the shares.  For further information regarding the possible methods by which the shares may be distributed, see “Plan of Distribution” beginning on page 11 of this prospectus.

Our Common Stock is listed on The Nasdaq Capital Market under the symbol “SLS.” The last reported sale price of our Common Stock on August 10, 2020 was $3.49 per share.

Investing in our Common Stock is highly speculative and involves a significant degree of risk.  Please consider carefully the specific factors set forth under "Risk Factors" beginning on page 5 of this prospectus and in our filings with the Securities and Exchange Commission.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of the disclosures in this prospectus.  Any representation to the contrary is a criminal offense.

The date of this prospectus is August _____________, 2020

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission (the “SEC”) pursuant to which the selling stockholders named herein may, from time to time, offer and sell or otherwise dispose of the shares of our Common Stock covered by this prospectus.  You should not assume that the information contained in this prospectus is accurate on any date subsequent to the date set forth on the front cover of this prospectus or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus is delivered or shares of Common Stock are sold or otherwise disposed of on a later date.  It is important for you to read and consider all information contained in this prospectus, including the documents incorporated by reference therein, in making your investment decision.  You should also read and consider the information in the documents to which we have referred you under “Where You Can Find Additional Information” and “Information Incorporated by Reference” in this prospectus.

We have not authorized anyone to give any information or to make any representation to you other than those contained or incorporated by reference in this prospectus.  You must not rely upon any information or representation not contained or incorporated by reference in this prospectus.  This prospectus does not constitute an offer to sell or the solicitation of an offer to buy any of our shares of Common Stock other than the shares of our Common Stock covered hereby, nor does this prospectus constitute an offer to sell or the solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction.  Persons who come into possession of this prospectus in jurisdictions outside the United States are required to inform themselves about, and to observe, any restrictions as to the offering and the distribution of this prospectus applicable to those jurisdictions.

Unless we have indicated otherwise, or the context otherwise requires, references in this prospectus to “SELLAS,” the “Company,” “we,” “us” and “our” refer to SELLAS Life Sciences Group, Inc.

PROSPECTUS SUMMARY

This summary description about us and our business highlights selected information contained elsewhere in this prospectus or incorporated by reference into this prospectus.  It does not contain all the information you should consider before investing in our securities.  Important information is incorporated by reference into this prospectus.  To understand this offering fully, you should read carefully the entire prospectus, including "Risk Factors" and "Cautionary Note Regarding Forward-Looking Statements," together with the additional information described under "Information Incorporated by Reference."

Overview

We are a late-stage clinical biopharmaceutical company focused on developing novel cancer immunotherapeutics for a broad range of cancer indications. Our product candidates currently include galinpepimut-S, or GPS, and nelipepimut-S, or NPS.

Pipeline

Galinpepimut-S, or GPS

Our lead product candidate, galinpepimut-S, or GPS, is a cancer immunotherapeutic agent licensed from Memorial Sloan Kettering Cancer Center, or MSK, that targets the Wilms tumor 1, or WT1, protein, which is present in 20 or more cancer types. Based on its mechanism of action as a directly immunizing agent, GPS has potential as a monotherapy or in combination with other immunotherapeutic agents to address a broad spectrum of hematologic, or blood, cancers and solid tumor indications.

In February 2020, we commenced an investigator-sponsored clinical trial, or IST, of GPS in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, Opdivo® (nivolumab), in patients with malignant pleural mesothelioma, or MPM, which is being conducted at MSK. This Phase 1 open-label clinical study will enroll patients with MPM who harbor relapsed or refractory disease after having received frontline standard of care multimodality therapy with the study drug provided by both us and Bristol-Myers Squibb. We expect initial data from this IST by the end of 2020.

In January 2020, we commenced a Phase 3 trial for GPS monotherapy in patients with acute myeloid leukemia, or AML, in the maintenance setting after achievement of their second complete remission, or CRem2, following successful completion of second-line antileukemic therapy. We expect this study, the REGAL study, will be used as the basis for a Biologics License Application, or BLA, submission, subject to a statistically significant and clinically meaningful data outcome and agreement with the U.S. Food & Drug Administration, or the FDA. The study is expected to enroll approximately 116 patients at approximately 50 clinical sites in the United States and Europe and is contemplated to have a planned interim safety and futility analysis after 80 events (deaths) which we expect to occur by the end of 2021.

In December 2018, we initiated a Phase 1/2 multi-arm (‘basket’ type) clinical study of GPS in combination with Merck & Co., Inc.’s anti-PD-1 therapy, Keytruda® (pembrolizumab). We plan to enroll up to approximately 90 patients at up to 20 centers in the United States. The indications being studied are ovarian cancer (second or third line), colorectal cancer (third or fourth line), AML (in patients having achieved partial response as their best hematological response after four cycles of therapy with hypomethylating agents), triple negative breast cancer, or TNBC, (second line), and small cell lung cancer, or SCLC. We expect initial data from this study in the first half of 2021.

GPS was granted Orphan Drug Product Designations from the FDA, as well as Orphan Medicinal Product Designations from the European Medicines Agency, or EMA, for GPS in AML, MPM, and multiple myeloma, or MM, as well as Fast Track Designation for AML, MPM, and MM from the FDA.

Nelipepimut-S or NPS

Nelipepimut-S, or NPS, is a cancer immunotherapy targeting the human epidermal growth factor receptor 2, or HER2, expressing cancers. Data presented in 2018 from a Phase 2b clinical trial of the combination of trastuzumab (Herceptin®) plus NPS in HER2 low expressing (1+ or 2+ per immunohistochemistry, or IHC) breast cancer patients in the adjuvant setting to prevent recurrences showed a clinically and statistically significant improvement in the disease-free survival, or DFS, rate for the TNBC cohort at 24 months for patients treated with NPS plus trastuzumab of 92.6% compared to 70.2% for those treated with trastuzumab alone. Following ongoing discussions with the FDA and based upon written feedback from the FDA and on the totality of clinical, safety and translational NPS data to date, we have finalized the design and plan for a Phase 3 registration-enabling study of NPS in combination with trastuzumab for the treatment of patients with TNBC in the adjuvant setting after standard treatment. If successful, we believe this study may be considered as the basis for a BLA submission to the FDA. We are seeking out-licensing opportunities to fund and conduct the future clinical development of NPS in order to maximize the potential of the program and we do not plan to conduct and fund a Phase 3 program for NPS on our own.

FBP-targeting bivalent vaccine (GALE-301/-302)

In order to prioritize development of our core assets, we have determined to cease development of GALE-301 and GALE-302, cancer immunotherapies that target the E39 peptide derived from the folate binding protein, or FBP, which were licensed in from The Henry M. Jackson Foundation, or HJF, and the MD Anderson Cancer Center, or MDACC. We are currently negotiating a termination of the license agreement with HJF and MDACC.

Impact of COVID-19

On March 11, 2020, the World Health Organization declared the outbreak of a new coronavirus to be a “pandemic”. First identified in 2019 and known now as COVID-19, the outbreak has resulted in various “stay-at-home” and “shutdown” orders through the various states in the United States as well as most countries worldwide. The pandemic has impacted millions of individuals and businesses worldwide. As we have functioned operationally as a semi-virtual company, the transition to “work-from home” for our employees has not materially altered our business operations. We are implementing a return-to-work policy in compliance with federal, state and local requirements and guidance and expect to operate on a semi-virtual basis for the remainder of 2020. Our Phase 3 REGAL study is progressing, with the necessary work to activate additional sites in the United States and Europe continuing without material interruption. During the second quarter, we initiated additional sites as planned; however, many of these sites are located in geographic regions, such as Florida, Texas and California, that are currently experiencing a surge of new COVID-19 cases. Accordingly, we are uncertain at this time the extent to which these newly initiated sites will be fully operational, which could have an impact on the projected timing of the REGAL study. Screening is ongoing at the majority of the sites in the GPS + pembrolizumab combination study although certain sites in this study also have limited operations to some extent. Due to the uncertainty of these limitations regarding the sites, we expect initial clinical data from the basket study in the first half of 2021. We believe that the COVID-19 pandemic has not materially impacted our efforts to out-license NPS. The extent to which the coronavirus impacts the Company's operations will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the duration of the outbreak, the emergence of new geographic hotspots where the coronavirus is spreading more rapidly, the re-emergence of a second outbreak in the fall or winter, new information which may emerge concerning the severity of the coronavirus and the actions to contain the coronavirus or treat its impact, among others. In particular, the continued spread of the coronavirus globally could adversely impact the Company's clinical trial operations and could have an adverse impact on the Company's business and the Company's financial results.

Risks Associated with Our Business

Our business and our ability to implement our business strategy are subject to numerous risks, as more fully described in the section entitled "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended December 31, 2019, incorporated herein by reference.  You should read these risks before you invest in our securities.  We may be unable, for many reasons, including those that are beyond our control, to implement our business strategy.

Corporate Information

We were incorporated on April 3, 2006 in Delaware as Argonaut Pharmaceuticals, Inc. On November 28, 2006, we changed our name to RXi Pharmaceuticals Corporation and began operations in January 2007. On September 26, 2011, we changed our name to Galena Biopharma, Inc. In December, 2017, we completed the business combination with the privately held Bermuda exempted company, Sellas Life Sciences Group Ltd., or Private SELLAS, which we refer to throughout the registration statement of which this prospectus forms a part as the “Merger.” As a result of the Merger, our business is now substantially comprised of the business of Private SELLAS. Upon completion of the Merger, we changed our name from “Galena Biopharma, Inc.” to “SELLAS Life Sciences Group, Inc.,” our Common Stock began trading on The Nasdaq Capital Market under a new ticker symbol “SLS” on January 2, 2018, and our financial statements became those of Private SELLAS.

 Our principal executive offices are located at 7 Times Square, Suite 2503, New York, NY 10036, and our phone number is (917) 438-4353. Our website address is www.sellaslife.com. The information contained on, or that can be accessed through, our website is not a part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

THE OFFERING

Throughout this prospectus, when we refer to the shares of our Common Stock being registered on behalf of the selling stockholders for offer and sale, we are referring to the shares of Common Stock sold to the selling stockholders, as well as the shares of Common Stock issuable upon exercise of the Warrants, each as described under “The Offering” and “Selling Stockholders.” When we refer to the selling stockholders in this prospectus, we are referring to the selling stockholders identified in this prospectus and, as applicable, their donees, pledgees, transferees or other successors-in-interest selling shares of Common Stock or interests in shares of Common Stock received after the date of this prospectus from a selling stockholder as a gift, pledge, partnership distribution or other transfer.

RISK FACTORS

Investing in our securities involves a high degree of risk.  You should carefully consider and evaluate all of the information contained in this prospectus, the accompanying prospectus and in the documents we incorporate by reference into this prospectus and accompanying prospectus before you decide to purchase our securities.  In particular, you should carefully consider and evaluate the risks and uncertainties described under the heading "Risk Factors" in our Annual Report on Form 10-K for the fiscal year ended December 31, 2019.  Any of the risks and uncertainties set forth in that report, as updated by annual, quarterly and other reports and documents that we file with the SEC and incorporate by reference into this prospectus or any prospectus, could materially and adversely affect our business, results of operations and financial condition, which in turn could materially and adversely affect the value of any securities offered by this prospectus.  As a result, you could lose all or part of your investment.

THE OFFERING

On July 31, 2020, we entered into the "Purchase Agreement" with certain investors (each an “Investor” and, collectively, the “Investors”), pursuant to which we issued and sold, in a private placement (the “Offering”), 2,744,078 shares of the Company's common stock, par value $0.0001 per share (the “Common Stock”), at a purchase price of $3.335 per share (the “Shares”) and warrants to purchase up to 2,744,078 shares of Common Stock at an exercise price of $3.30 per share (the “Warrants”). The Warrants were immediately exercisable upon issuance and expire five years from the date of issuance.

In connection with the Offering, we entered into a Registration Rights Agreement (the “Registration Rights Agreement”) with the Investors, pursuant to which we are obligated, among other things, to (i) file a registration statement with the U.S. Securities and Exchange Commission (the “SEC”) within 20 days following the entrance into the Registration Rights Agreement for purposes of registering the Shares and the shares of Common Stock issuable upon exercise of the Warrants for resale by the Investors, (ii) use our reasonable best efforts to have the registration statement declared effective as soon as practicable after filing, and in any event no later than sixty (60) days after the entrance into the Registration Rights Agreement (or ninety (90) days after the entrance into the Registration Rights Agreement if the registration statement is reviewed by the SEC), and (iii) maintain the registration until all registrable securities may be sold pursuant to Rule 144 under the Securities Act, without restriction as to volume.  The Registration Rights Agreement contains customary terms and conditions for a transaction of this type, including certain customary cash penalties on the Registrant for its failure to satisfy specified filing and effectiveness time periods.

The foregoing descriptions of the Purchase Agreement, the Registration Rights Agreement and the form of Warrant are not complete and are subject to and qualified in their entirety by reference to the Purchase Agreement, the Registration Rights Agreement and the form of Warrant, respectively, copies of which are attached as Exhibits 10.1, 10.2 and 4.1, respectively, to the Current Report on Form 8-K dated August 4, 2020, and are incorporated herein by reference.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS 

This prospectus and the documents incorporated by reference into this prospectus include forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, as amended, that relate to future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to differ materially from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements. Words such as, but not limited to, “anticipate,” “aim,” “believe,” “contemplate,” “continue,” “could,” “design,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “predict,” “poise,” “project,” “potential,” “suggest,” “should,” “strategy,” “target,” “will,” “would,” and similar expressions or phrases, or the negative of those expressions or phrases, are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Although we believe that we have a reasonable basis for each forward-looking statement contained in this prospectus and incorporated by reference into this prospectus, we caution you that these statements are based on our projections of the future that are subject to known and unknown risks and uncertainties and other factors that may cause our actual results, level of activity, performance or achievements expressed or implied by these forward-looking statements, to differ. The section in this prospectus entitled “Risk Factors” and the sections in our periodic reports, including the 2019 Form 10-K entitled “Business,” and in the 2019 Form 10-K and our most recent quarterly report on Form 10-Q entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as other sections in this prospectus and the documents or reports incorporated by reference into this prospectus, discuss some of the factors that could contribute to these differences. These forward-looking statements include, among other things, statements about:

Our current product candidates are undergoing clinical development and have not been approved by the FDA or the European Commission. These product candidates have not been, nor may they ever be, approved by any regulatory agency or competent authorities nor marketed anywhere in the world.

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Forward-looking statements should be regarded solely as our current plans, estimates and beliefs. We have included important factors in the cautionary statements included in this document, particularly in the section entitled “Risk Factors” beginning on page 5 of this prospectus that we believe could cause actual results or events to differ materially from the forward-looking statements that we make. Moreover, we operate in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. Given these risks and uncertainties, readers are cautioned not to place undue reliance on such forward-looking statements. All forward-looking statements are qualified in their entirety by this cautionary statement. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make. You should read this prospectus and the documents that we have filed as exhibits to this prospectus and incorporated by reference herein completely and with the understanding that our actual future results may be materially different from the plans, intentions and expectations disclosed in the forward-looking statements we make. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity or performance. The forward-looking statements contained in this prospectus are made as of the date of this prospectus and we do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by applicable law.

You should also consider carefully the statements set forth in the sections titled "Risk Factors" or elsewhere in this prospectus, in the accompanying prospectus and in the documents incorporated or deemed incorporated herein or therein by reference, which address various factors that could cause results or events to differ from those described in the forward-looking statements.  All subsequent written and oral forward-looking statements attributable to us or to persons acting on our behalf are expressly qualified in their entirety by the applicable cautionary statements.  We have no plans to update these forward-looking statements.

USE OF PROCEEDS

We will not receive any of the proceeds from the sale of Common Stock by the selling stockholders named in this prospectus, and the selling stockholders will receive all of the proceeds from this offering.

We may receive up to approximately $9.1 million in aggregate gross proceeds from cash exercises of the Warrants, based on the per share exercise price of the Warrants. Any proceeds we receive from the exercise of the Warrants will be used to advance our clinical programs and for general corporate purposes. The holders of the Warrants are not obligated to exercise their Warrants, and we cannot predict whether holders of the Warrants will choose to exercise all or any of their Warrants.

SELLING STOCKHOLDERS

This prospectus relates to the sale or other disposition of up to 5,488,156 shares of our Common Stock and shares of Common Stock issuable to the selling stockholders upon exercise of the Warrants by the selling stockholders named below, and their donees, pledgees, transferees or other successors-in-interest selling shares of Common Stock or interests in shares of Common Stock received after the date of this prospectus from a selling stockholder as a gift, pledge, partnership distribution or other transfer.  The shares of Common Stock covered hereby were issued by us in the Offering.  See “The Offering” beginning on page 5 of this prospectus.

The table below sets forth information as of August 13, 2020, to our knowledge, for the selling stockholders and other information regarding the beneficial ownership (as determined under Section 13(d) of the Exchange Act and the rules and regulations thereunder) of the shares of Common Stock held by the selling stockholders.  The second column lists the number of shares of Common Stock and percentage beneficially owned by the selling stockholders as of July 31, 2020.  The third column lists the maximum number of shares of Common Stock that may be sold or otherwise disposed of by the selling stockholders pursuant to the registration statement of which this prospectus forms a part.  The selling stockholders may sell or otherwise dispose of some, all or none of their shares.  Pursuant to Rules 13d-3 and 13d-5 of the Exchange Act, beneficial ownership includes any shares of our Common Stock as to which a stockholder has sole or shared voting power or investment power, and also any shares of our Common Stock which the stockholder has the right to acquire within 60 days of August 13, 2020.  The percentage of beneficial ownership for the selling stockholders is based on 9,461,978 shares of our Common Stock outstanding as of August 13, 2020 and the number of shares of our Common Stock issuable upon exercise or conversion of convertible securities that are currently exercisable or convertible or are exercisable or convertible within 60 days of August 13, 2020 beneficially owned by the applicable selling stockholder.  Except as described below, to our knowledge, none of the selling stockholders has been an officer or director of ours or of our affiliates within the past three years or has any material relationship with us or our affiliates within the past three years.  Our knowledge is based on information provided by the selling stockholders in connection with the filing of this prospectus, as well as information obtained from relevant Schedule 13D and 13G filings.

The shares of Common Stock being covered hereby may be sold or otherwise disposed of from time to time during the period the registration statement of which this prospectus is a part remains effective, by or for the account of the selling stockholders.  After the date of effectiveness of such registration statement, the selling stockholders may sell or transfer, in transactions covered by this prospectus or in transactions exempt from the registration requirements of the Securities Act, some or all of their Common Stock.

Information about the selling stockholders may change over time.  Any changed information will be set forth in an amendment to the registration statement or supplement to this prospectus, to the extent required by law.

PLAN OF DISTRIBUTION

Each selling stockholder of the securities and any of their pledgees, assignees and successors-in-interest may, from time to time, sell any or all of their securities covered hereby on The Nasdaq Capital Market or any other stock exchange, market or trading facility on which the securities are traded or in private transactions. These sales may be at fixed or negotiated prices. A selling stockholder may use any one or more of the following methods when selling securities:

The selling stockholders may also sell securities under Rule 144 or any other exemption from registration under the Securities Act of 1933, as amended (the “Securities Act”), if available, rather than under this prospectus.

Broker-dealers engaged by the selling stockholders may arrange for other brokers-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the selling stockholders (or, if any broker-dealer acts as agent for the purchaser of securities, from the purchaser) in amounts to be negotiated, but, except as set forth in a supplement to this Prospectus, in the case of an agency transaction not in excess of a customary brokerage commission in compliance with FINRA Rule 2121; and in the case of a principal transaction a markup or markdown in compliance with FINRA Rule 2121.

In connection with the sale of the securities or interests therein, the selling stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the securities in the course of hedging the positions they assume. The selling stockholders may also sell securities short and deliver these securities to close out their short positions, or loan or pledge the securities to broker-dealers that in turn may sell these securities. The selling stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or create one or more derivative securities which require the delivery to such broker-dealer or other financial institution of securities offered by this prospectus, which securities such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The selling stockholders and any broker-dealers or agents that are involved in selling the securities may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. In such event, any commissions received by such broker-dealers or agents and any profit on the resale of the securities purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Each selling stockholder has informed the Company that it does not have any written or oral agreement or understanding, directly or indirectly, with any person to distribute the securities.

The Company is required to pay certain fees and expenses incurred by the Company incident to the registration of the securities. The Company has agreed to indemnify the selling stockholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act.

We agreed to keep this prospectus effective until the earlier of (i) the date on which the securities may be resold by the selling stockholders without registration and without regard to any volume or manner-of-sale limitations by reason of Rule 144, without the requirement for the Company to be in compliance with the current public information under Rule 144 under the Securities Act or any other rule of similar effect or (ii) all of the securities have been sold pursuant to this prospectus or Rule 144 under the Securities Act or any other rule of similar effect. The resale securities will be sold only through registered or licensed brokers or dealers if required under applicable state securities laws. In addition, in certain states, the resale securities covered hereby may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

Under applicable rules and regulations under the Exchange Act, any person engaged in the distribution of the resale securities may not simultaneously engage in market making activities with respect to the Common Stock for the applicable restricted period, as defined in Regulation M, prior to the commencement of the distribution. In addition, the selling stockholders will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including Regulation M, which may limit the timing of purchases and sales of the Common Stock by the selling stockholders or any other person. We will make copies of this prospectus available to the selling stockholders and have informed them of the need to deliver a copy of this prospectus to each purchaser at or prior to the time of the sale (including by compliance with Rule 172 under the Securities Act).

LEGAL MATTERS

The validity of the shares of Common Stock offered in this prospectus has been passed upon for us by Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., New York, New York.

EXPERTS

Our consolidated financial statements appearing in our Annual Report on Form 10-K for the year ended December 31, 2019, have been audited by Moss Adams LLP, an independent registered public accounting firm, as stated in their report, which is incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the report of such firm (which report expresses an unqualified opinion and includes an explanatory paragraph regarding the Company’s going concern uncertainty) given upon their authority as experts in accounting and auditing. 

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We are subject to the information requirements of the Exchange Act and we therefore file periodic reports, proxy statements and other information with the SEC relating to our business, financial statements and other matters.  The reports, proxy statements and other information we file may be inspected and copied at prescribed rates at the SEC's Public Reference Room located at 100 F Street, N.E., Washington, D.C.  20549.  You may obtain information on the operation of the SEC's Public Reference Room by calling the SEC at 1-800-SEC-0330.  The SEC also maintains a website that contains reports, proxy and information statements and other information regarding issuers like us that file electronically with the SEC.  The address of the SEC's website is http://www.sec.gov.

This prospectus constitutes part of a registration statement filed under the Securities Act with respect to the shares of Common Stock covered hereby.  As permitted by the SEC's rules, this prospectus omits some of the information, exhibits and undertakings included in the registration statement.  You may read and copy the information omitted from this prospectus but contained in the registration statement, as well as the periodic reports and other information we file with the SEC, at the public reference room and website of the SEC referred to above.  You may also access our filings with the SEC on our website, which is located at http://www.sellaslifesciences.com/.  The information contained on our website is not part of this prospectus.

Statements contained in this prospectus as to the contents of any contract or other document are not necessarily complete, and in each instance we refer you to the copy of the contract or other document filed or incorporated by reference as an exhibit to the registration statement or as an exhibit to our Exchange Act filings, each such statement being qualified in all respects by such reference.

INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring you to another document that we have filed separately with the SEC. You should read the information incorporated by reference because it is an important part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this prospectus and the registration statement of which this prospectus is a part the information or documents listed below that we have filed with the SEC (Commission File No. 001-33958):

We also incorporate by reference any future filings (other than current reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items unless such Form 8-K expressly provides to the contrary) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including those made after the date of the initial filing of the registration statement of which this prospectus is a part and prior to effectiveness of such registration statement, until we file a post-effective amendment that indicates the termination of the offering of the Common Stock made by this prospectus and will become a part of this prospectus from the date that such documents are filed with the SEC. Information in such future filings updates and supplements the information provided in this prospectus. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later filed document modify or replace such earlier statements.

We will furnish without charge to each person, including any beneficial owner, to whom a prospectus is delivered, upon written or oral request, a copy of any or all of the documents incorporated by reference into this prospectus but not delivered with the prospectus, including exhibits that are specifically incorporated by reference into such documents. You should direct any requests for documents to SELLAS Life Sciences Group, Inc., Attention: Corporate Secretary, 7 Times Square, Suite 2503, New York, New York 10036. Our phone number is (917) 438-4353.

You should rely only on information contained in, or incorporated by reference into, this prospectus and any prospectus supplement. We have not authorized anyone to provide you with information different from that contained in this prospectus or incorporated by reference into this prospectus. We are not making offers to sell the securities in any jurisdiction in which such an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such offer or solicitation.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14.  Other Expenses of Issuance and Distribution.

The following table sets forth all costs and expenses payable by the Registrant, in connection with the sale of the securities being registered under this registration statement.  All amounts shown are estimates except for the Securities and Exchange Commission, or SEC, registration fee.

Item 15.  Indemnification of Directors and Officers.

As permitted by Section 102 of the Delaware General Corporation Law, we have adopted provisions in our amended and restated certificate of incorporation and amended and restated bylaws, each as amended, which limit or eliminate the personal liability of our directors for a breach of their fiduciary duty of care as a director. The duty of care generally requires that, when acting on behalf of the corporation, directors exercise an informed business judgment based on all material information reasonably available to them. Consequently, a director will not be personally liable to us or our stockholders for monetary damages for breach of fiduciary duty as a director, except for liability for:

These limitations of liability do not affect the availability of equitable remedies such as injunctive relief or rescission. Our amended and restated certificate of incorporation also authorizes us to indemnify our officers, directors and other agents to the fullest extent permitted under Delaware law.

As permitted by Section 145 of the Delaware General Corporation Law, our amended and restated bylaws, as amended, provide that:

Our amended and restated certificate of incorporation and bylaws, each as amended, which are filed as Exhibits 3.1 and 3.3, provide for the indemnification provisions described above and elsewhere herein. We have entered into separate indemnification agreements with our directors and officers that may be broader than the specific indemnification provisions contained in the Delaware General Corporation Law. These indemnification agreements generally require us, among other things, to indemnify our officers and directors against liabilities that may arise by reason of their status or service as directors or officers, other than liabilities arising from willful misconduct. These indemnification agreements also generally require us to advance any expenses incurred by the directors or officers as a result of any proceeding against them as to which they could be indemnified. In addition, we have purchased a policy of directors’ and officers’ liability insurance that insures our directors and officers against the cost of defense, settlement or payment of a judgment in some circumstances. These indemnification provisions and the indemnification agreements may be sufficiently broad to permit indemnification of our officers and directors for liabilities, including reimbursement of expenses incurred, arising under the Securities Act.

We have entered into indemnification agreements with our directors and executive officers, in addition to the indemnification provided for in our amended and restated certificate of incorporation and amended and restated bylaws, and intend to enter into indemnification agreements with any new directors and executive officers in the future.

We have purchased and currently intend to maintain insurance on behalf of each and every person who is or was a director or officer of our company against any loss arising from any claim asserted against him or her and incurred by him or her in any such capacity, subject to certain exclusions.

Item 16.  Exhibits.

See Exhibit Index following the signature page to this Registration Statement.

Item 17.  Undertakings.

The undersigned registrant hereby undertakes:

provided, however, that paragraphs (a)(1)(i), (ii), and (iii) of this section do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to section 13 or section 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m or 78o(d)) that are incorporated by reference in the registration statement.

The undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

The undersigned registrant hereby undertakes that, for purposes of determining any liability under the Securities Act, each filing of the registrant’s annual report pursuant to section 13(a) or section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers, and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

The undersigned registrant hereby undertakes that:

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized in the city of New York, New York, on this August 14, 2020.

POWER OF ATTORNEY

We, the undersigned officers and directors of SELLAS Life Sciences Group, Inc., hereby severally constitute and appoint Angelos M. Stergiou and John Burns, and each of them singly, as our true and lawful attorneys, with full power to them, and to each of them singly, to sign for us and in our names in the capacities indicated below, the registration statement on Form S-3 filed herewith, and any and all pre-effective and post-effective amendments to said registration statement, and any registration statement filed pursuant to Rule 462(b) under the Securities Act of 1933, as amended, in connection with the registration under the Securities Act of 1933, as amended, of equity securities of the Company, and to file or cause to be filed the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as each of us might or could do in person, and hereby ratifying and confirming all that said attorneys, and each of them, or their substitute or substitutes, shall do or cause to be done by virtue of this Power of Attorney.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement on Form S-3 has been signed below by the following persons in the capacities and on the dates indicated.

EXHIBIT LIST

Exhibit 5.1

August 14, 2020

SELLAS Life Sciences Group, Inc.

7 Times Square, Suite 2503

New York, NY 10036

Ladies and Gentlemen:

We have acted as legal counsel to SELLAS Life Sciences Group, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-3 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to the registration for resale by the selling stockholders named in the Registration Statement (the “Selling Stockholders”) of up to an aggregate of 5,488,156 shares of the Company’s common stock, $0.0001 par value per share (“Common Stock”), consisting of (i) 2,744,078 shares of Common Stock issued to the Selling Stockholders on July 31, 2020 (the “Shares”) and (ii) 2,744,078 shares of Common Stock issuable upon the exercise of certain outstanding warrants (the “Warrants”) issued by the Company to the Selling Stockholders on July 31, 2020 (the “Warrant Shares”). This opinion is being rendered in connection with the filing of the Registration Statement with the Commission.

In connection with this opinion, we have examined and relied upon the Articles of Incorporation and Bylaws of the Company, each as restated and/or amended to date, and such other documents as we have deemed necessary for purposes of rendering the opinions hereinafter set forth.

In our examination, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as certified or photostatic copies and the authenticity of the originals of such copies.

Our opinion is limited to the general corporate laws of the State of Delaware and we express no opinion with respect to the laws of any other jurisdiction. No opinion is expressed herein with respect to the qualification of the Shares or the Warrant Shares under the securities or blue sky laws of any state or any foreign jurisdiction.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters. This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

Based upon the foregoing, we are of the opinion that (i) the Shares are validly issued, fully paid and non-assessable and (ii) the Warrant Shares, when issued and delivered upon the exercise of the Warrants in accordance with their terms, will be validly issued, fully paid and non-assessable. We understand that you wish to file this opinion with the Commission as an exhibit to the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-K promulgated under the Securities Act and to reference the firm’s name under the caption “Legal Matters” in the prospectus which forms part of the Registration Statement, and we hereby consent thereto. In giving this consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in this Registration Statement on Form S-3 of SELLAS Life Sciences Group, Inc. (the “Company”) of our report dated March 13, 2020, relating to the consolidated financial statements of the Company, which report appears in the Annual Report on Form 10-K of the Company for the year ended December 31, 2019 (and expresses an unqualified opinion and includes an explanatory paragraph regarding the Company’s going concern emphasis), filed with the Securities and Exchange Commission, and to the reference to our firm under the heading “Experts” in the Prospectus, which is part of this Registration Statement.

/s/ Moss Adams LLP

San Francisco, California

August 14, 2020