SELLAS Life Sciences Group Inc. announced that the sponsor-principal investigator, after taking into account that key clinical development objectives were met as well as other regulatory considerations, and in agreement with SELLAS, determined to terminate early the Phase 2b independent investigator-sponsored clinical trial (IST) of trastuzumab (Herceptin®) +/- nelipepimut-S (NeuVax™) in HER2 1+/2+ breast cancer patients. In this Phase 2b study, Herceptin® was provided under a Clinical Trial Supply Agreement by Genentech, Inc. The decision to early terminate this Phase 2b study was based in part on the previously announced recommendation of the independent Data Safety Monitoring Board (DSMB) to further advance the development of the NeuVax + Herceptin combination for the triple negative breast cancer (TNBC) patient population. Data from the Phase 2b has been submitted for presentation at a major medical conference that will take place during the second half of 2018. SELLAS conducted this week two advisory meetings with global experts in regulatory affairs and breast cancer clinical development in order to determine the optimal path for further development of the NeuVax + Herceptin combination in TNBC in a pivotal setting and engagement with the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA). As previously announced, a pre-specified interim analysis of safety and efficacy conducted by the DSMB, demonstrated a clinically meaningful and statistically significant difference between the TNBC cohort of patients and the control arm with a hazard ratio of 0.26, p-value = 0.023, in favor of the NeuVax + Herceptin combination compared to Herceptin alone. The analysis also showed an adverse event profile with no notable differences between treatment arms and no additional cardiotoxicity in the NeuVax + Herceptin arm. Based on these positive results, the DSMB recommended to expeditiously seek regulatory guidance from the FDA for further development of the combination of NeuVax + Herceptin in TNBC, a population with a large unmet medical need.

The company also announced that it has appointed Jeffrey S. Weber, MD, PhD, as Chairman of its SAB. In his new role, together with the other members of the Company's SAB, Dr. Weber will strengthen the company's capacities to drive, position and prioritize pipeline development with key focus on two assets, galinpepimut-S and nelipepimut-S (NeuVaxTM). Dr. Weber currently serves as Co-Director of the Melanoma Program at the New York University (NYU)-Langone Perlmutter Cancer Center and Deputy Director of the Center. Prior to this position, he was Head of the Melanoma Center of Excellence at H. Lee Moffitt Cancer Center.