CLINICAL STUDY PROTOCOL SLS17- 201/ MK3475 -770 IND # 18730 CLINICALTRIALS.GOV I DENTIFIER : NCT03761914 A PHASE 1/2 STUDY OF GALINPEPIMUT -S IN COMBINATION WITH PEMBROLIZUMAB (MK -3475) IN PATIENTS WITH SELECTED ADV ANCED CANCERS PROTOCOL NUMBER SLS17- 201/MK3475 -770 PROTOCOL v1.1 AMENDMENT 1.0 Sponsor: SELLAS Life Sciences Group, Inc. 15 West 38th Street; 10th Floor New York, NY 10018 United States of America Telephone: +1-917-438-4352 FAX: +1-917-634-3413 Medical Monitor: Nicholas J. Sarlis, MD, PhD Email: nsarlis@sellaslife.com Clinical Research Organization: Cancer Insight, LLC 1422 E Grayson; 3rd Floor San Antonio, TX 78208 United States of America Date of Original Protocol: 8 January 2018 (original protocol) Date of Protocol v1.1 (Amendment 1.0): 12 April 2019 CONFIDENTIAL All financial and nonfinancial support for this study will be provided by SELLAS Life Sciences Group. The concepts and information contained in this document or generated during the study are considered proprietary and may not be disclosed in whole or in part without the expressed, written consent of SELLAS Life Sciences Group. The study will be conducted according to the International Council on Harmonisation harmonised tripartite guideline E6(R 2): Good Clinical Practice (ICH GCP). SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 Protocol Approval – Sponsor Signatory Study Title A Phase 1/2 Study of Galinpepimut-S in Combination with Pembrolizumab (MK-3475) in Patients with Selected Advanced Cancers Protocol Number SLS17-201/MK3475-770 Protocol Date 08 January 2018 (original) Date of Protocol v1.1 (Amendment 1.0) 12 April 2019 Protocol v1.1 (Amendment 1.0) accepted and approved by: Chief Medical Officer and Study Medical Monitor SELLAS Life Sciences Group, Inc. Nicholas Sarlis, MD, PhD, FACP Chief Medical Officer SELLAS Life Sciences Group, Inc. 15 West 38th Street; 10th Floor New York, NY 10018 United States of America SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 12 April 2019 Signature Date SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 Protocol Approval –Study Master Principal/Coordinating Investigator s Study Title A Phase 1/2 Study of Galinpepimut-S in Combination with Pembrolizumab in Patients with Selected Advanced Cancers Protocol Number SLS17-201/ MK3475-770 Protocol Date 08 January 2018 (original) Date of Protocol v1.1 (Amendment 1.0) 12 April 2019 Protocol accepted and approved by: Co-Principal/Coordinating Investigators United States Co-PI #1 Richard T. Maziarz, MD Medical Director, Adult Blood and Marrow Stem Cell Transplant & Cellular Therapy Program Professor of Medicine Knight Cancer Institute Oregon Health and Science University (OHSU) 3181 SW. Sam Jackson Park Road Portland, OR 97239 USA <On file> 12 April 2019 Signature Date Co-PI #2 Roisin O’Cearbhaill, MB BCh, BAO Assistant Attending Physician Gynecologic Medical Oncology Service SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 Department of Medicine Memorial Sloan-Kettering Cancer Center 1275 York Avenue New York, NY 10065 USA <On file> 12 April 2019 Signature Date SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 Declaration of Investigator * I have read and understood all sections of the protocol entitled “A Phase 1/2 Study of Galinpepimut-S in Combination with Pembrolizumab (MK-3475) in Patients with Selected Cancers”, Protocol v1.1 (Amendment 1.0), and the accompanying investigator’s brochures, version 2.0, dated 08 June 2017 for galinpepimut-S and edition 16, dated 29 June 2018 for pembrolizumab. I agree to supervise all aspects of the protocol and to conduct the clinical investigation in accordance with the Final Protocol v1.1, Amendment 1.0, dated 12 April 2019, the International Council on Harmonisation harmonised tripartite guideline E6(R2): Good Clinical Practice (ICH GCP) and all applicable government regulations. I will not make changes to the protocol before consulting with SELLAS Life Sciences Group or implement protocol changes without independent ethics committee approval except to eliminate an immediate risk to patients. I agree to administer study treatment only to patients under my personal supervision or the supervision of a subinvestigator. I will not supply the investigational drug to any person not authorized to receive it. I will protect patient confidentiality and p atient identity will not be disclosed to third parties or appear in any study reports or publications. I will not disclose information regarding this clinical i nvestigation or publish results of the investigation without authorization from SELLAS Life Sciences Group. <Signature > <DD/MM/YYYY> Signature of Principal Investigator* Date <Name> Printed Name of Principal Investigator* *: Declaration Form for Individual Participating Clinical Site P.I.’s SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 SELLAS Life Sciences Group Galinpepimut -S Protocol : SLS17 -201/MK3475 -770 Protocol v1.1 (Amendment 1.0) 12 April 2019 Page 9 List of Tables ........................................................................................................................... 17 List of Figures ..........................................................................................................................