SLS SELLAS Life Sciences Group Inc

Interim and Updated Final Clinical Data to be Presented

SELLAS Life Sciences Group, Inc. (Nasdaq:SLS) (“SELLAS” or the “Company”), a clinical-stage biopharmaceutical company focused on the development of novel cancer immunotherapies for a broad range of cancer indications, today announced that it will host a conference call at 8:00 a.m. ET on October 22, 2018, following the oral presentation at the ESMO 2018 Annual Meeting of the interim (median follow-up of 18.8 months) and updated and final (median follow-up of 26.1 months) clinical data from its Phase 2b trial of the combination of trastuzumab (Herceptin®) +/- nelipepimut-S (NeuVax™) targeting HER2 low-expressing breast cancer patient cohorts.  Management and invited Key Opinion Leaders, including Dr. Elizabeth Mittendorf, MD, PhD and Dr. George Peoples, MD, FACS, will participate in the conference call.

Conference Call Details for Monday, October 22, 2018 at 8:00 a.m. ET:

To participate in the conference call, please dial (866) 416-7995 (domestic) or +1 (409) 217-8225 (international) and refer to conference ID 5571389. A live webcast of the call can be accessed under "Events & Presentations" in the Investors section of the Company's website at www.sellaslifesciences.com.

An archived webcast recording will be available on the SELLAS website beginning approximately two hours after the call.

Details for the ESMO presentation are as follows:

Title: Pre-specified interim analysis of a randomized phase 2b trial of trastuzumab + nelipepimut-S (NeuVax™) vs trastuzumab for the prevention of recurrence demonstrates benefit in triple negative (HER2 low-expressing) breast cancer patientsDate and Time: 22 October, 2018; 11:54 am Central European Time (5:54 am ET)Location: Hall A2 - Room 18; Messe Munich Congress Venue, Munich, Germany

Herceptin® is a registered trademark of Genentech, Inc. and is not a trademark of SELLAS. The manufacturer of this brand is not affiliated with and does not endorse SELLAS or its products.

About ESMO

The European Society for Medical Oncology (ESMO) is Europe’s leading non-profit medical oncology organization. ESMO is a membership-based society, comprising of 500 expert committee members and 18,000 oncology professionals. ESMO organizes a large number of meetings to provide its members and the community with the resources they need and also plays a major role in public policy and European affairs. The ESMO 2018 Annual Meeting represents a multi-professional platform for oncology education and exchange, and for immense international visibility for scientific research, and will be held under the tagline “Securing access to optimal cancer care.”

About SELLAS Life Sciences Group, Inc.

SELLAS is a clinical-stage biopharmaceutical company focused on novel cancer immunotherapeutics for a broad range of cancer indications. SELLAS’ lead product candidate, galinpepimut-S (GPS), is licensed from Memorial Sloan Kettering Cancer Center and targets the Wilms Tumor 1 (WT1) protein, which is present in an array of tumor types.  GPS has potential as a monotherapy or in combination to address a broad spectrum of hematologic malignancies and solid tumor indications.  SELLAS has Phase 3 clinical trials planned (pending funding availability) for GPS in two indications, acute myeloid leukemia (AML) and malignant pleural mesothelioma (MPM), and is also developing GPS as a potential treatment for multiple myeloma (MM) and ovarian cancer.  SELLAS plans to study GPS in up to four additional indications.  SELLAS has received Orphan Drug designations for GPS from both the U.S. Food & Drug Administration (FDA) and European Medicines Agency (EMA) for AML, MPM, and MM; GPS also received Fast Track designation for AML and MPM from the FDA. SELLAS’ second product candidate, NeuVax™ (nelipepimut-S), is a HER2-directed cancer immunotherapy being investigated for the prevention of the recurrence of breast cancer after standard of care treatment in the adjuvant setting. NeuVax™ has received Fast Track status designation by FDA for the treatment of patients with early stage breast cancer with low to intermediate HER2 expression, otherwise known as HER2 1+ or 2+, following standard of care.

For more information on SELLAS, please visit www.sellaslifesciences.com.

Investor Contacts:Will O’ConnorStern Investor Relations, Inc.212-362-1200ir@sellaslife.com

David Moser, JDSellas Life Sciences Group813-864-2571info@sellaslife.com