SELLAS Life Sciences : Company Overview – January 2022

Company Overview

NASDAQ: SLS

January 2022

Forward Looking Statements

This presentation contains forward-looking statements. Such forward-looking statements can be identified

by the use of the words "expect," "believe," "will," "anticipate," "estimate," "plan," "project" and other

words of similar import. The forward-looking statements in this presentation include, but are not limited to, statements related to the potential of our clinical candidates as therapeutic options for various

cancers, the general development of the Company's product candidate pipeline and anticipated milestone dates, and the effects of the Company's approach to cancer treatment. These forward-looking statements

are based on current plans, objectives, estimates, expectations and intentions, and inherently involve significant risks and uncertainties. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks and uncertainties associated with the COVID-19 pandemic and its impact on the Company's clinical plans and business strategy, immune-oncology product development and clinical success thereof, the uncertainty of regulatory approval, and other risks and uncertainties affecting SELLAS and its

development programs. These risks and uncertainties are described more fully under the caption "Risk

Factors" in the in SELLAS' Annual Report on Form 10-K filed on March 23, 2021 and in its other filings with the Securities and Exchange Commission. Other risks and uncertainties of which SELLAS is not currently aware may also affect SELLAS' forward-looking statements. The forward-looking statements herein are made only as of the date hereof. SELLAS undertakes no obligation to update or supplement any forward- looking statements to reflect actual results, new information, future events, changes in its expectations or other circumstances that exist after the date as of which the forward-looking statements were made.

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Overview

SELLAS is a late-stage clinical biopharmaceutical company focused on the development of novel cancer immunotherapies for a broad range of cancer indications.

• Lead product - galinpepimut-S(GPS): highly novel and engineered immunotherapy targeting the Wilms Tumor 1 (WT1) antigen
• • Discovered and licensed from Memorial Sloan Kettering Cancer Center
• GPS: Ongoing Phase 3 pivotal trial (REGAL study) for acute myeloid leukemia (AML) in patients achieving second complete remission (CR2)
• GPS: Phase 1/2 combination studies with anti-PD1 drugs - collaboration agreement with Merck (KEYTRUDA®) in various tumor types and an IST study with Memorial Sloan Kettering Cancer Center and Bristol Myers Squibb (OPDIVO ®) in metastatic pleural mesothelioma
• Out-licensingopportunity with second product candidate, nelipepimut-S(NPS): HER2-directedcancer immunotherapy with potential for the treatment of patients in the maintenance setting with triple negative breast cancer

NASDAQ: SLS

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Galinpepimut-S (GPS): Changing the face of Immunotherapy

• Pivotal Phase 3 Trial Underway in CR2 AML Patients (REGAL study)
• • Monotherapy AML maintenance after Second Complete Remission (CR2)
  • Interim read-outexpected in second half of 2022 (as long as there are no COVID-related delays)
  • Potential launch first half of 2024
  • Orphan Drug Designation (US and EU) and Fast Track status
  • Phase 2 results:
  • • GPS reaching 21.0 months median Overall Survival vs. 5.4 months standard of care (p < 0.02).
• Validated Wilms Tumor 1 (WT1) Target
• • #1 ranked cancer antigen by the NCI
  • GPS targets tumors that overexpress the WT1 protein
• Innovative, First-in-Class Technology Licensed from Memorial Sloan Kettering
• • Highly engineered immunotherapy designed to boost immunogenicity and break tolerance
  • Applicable to the majority (90%) of human HLA types
  • Activation of both CD4+ (memory) and CD8+ (tumor killing) cells
  • Sustained remission
• Broad Applicability in I/O Treatment Setting and Strong IP Position
• • Potential to be used as monotherapy or in combination with other I/O agents in multiple solid and hematological tumor types; two studies of GPS in combination with PD1 inhibitors ongoing
  • Composition of matter patent to at least 2033

NASDAQ: SLS

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WT1: Nuclear Transcription Factor with Oncogenic Properties

			Top Ranked Cancer Antigen by the National Cancer Institute (NCI)1
			Potential to treat 20 or more cancer types creates a large potential
			market for WT1 targeting therapies
			Broadly detectable in AML, where it is densely and almost
	Wilms Tumor 1 Protein		universally expressed (97%). It is also expressed in multiple solid
			tumors and cancer stem cells
			Highly expressed and presented in cancer cells, enabling
			recognition and killing by specifically immunized T-cells
			Intracellular oncofetal antigen, WT1 not found appreciably in
			adult tissues, which lowers potential off-target toxicity
			Does not down-regulate or become mutated frequently

Sources: Gaiger, Leukemia. 1998; 2. Dao & Scheinberg, Best Pract Res Clin Haematol. 2008; 3. Nishida & Sugiyama, Methods Mol Biol. 2016; NED: no evidence of disease

Notes: 1. 'The Prioritization of Cancer Antigens: A National Cancer Institute Pilot Project for the Acceleration of Translational Research' Cheever et al; Clin Cancer Res., 2009.

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