SELLAS Life Sciences Group, Inc. provided a corporate update on the Company’s clinical development of galinpepimut-S (GPS) and nelipepimut-S (NPS), which are both in late-stage development. In November 2018, SELLAS aligned with the FDA on the clinical trial design and biostatistical plan for a Phase 3 registrational study for GPS in acute myeloid leukemia (AML). The planned Phase 3 registrational study will be a 1:1 randomized, open-label study comparing GPS in the maintenance setting to investigators’ choice of best available treatment (BAT) in adult AML patients who have achieved hematologic complete remission, with or without thrombocytopenia (CR2/CR2p), after second-line antileukemic therapy and who are deemed ineligible for or unable to undergo allogeneic stem-cell transplantation. This study will serve as the basis for a Biologics License Application (BLA) submission, subject to positive results, and SELLAS expects to start the Phase 3 trial in the second quarter of 2019. The Phase 3 study is expected to enroll approximately 116 patients at approximately 50 clinical sites in the United States and Europe. The primary endpoint is overall survival (OS) and secondary endpoints include leukemia-free survival, antigen-specific T-cell immune response dynamics over time and rates of achievement of measurable residual disease (MRD) negativity. The study will have a planned interim safety and futility analysis after 80 events, expected to occur in the third quarter of 2020. GPS was previously granted Fast Track and Orphan Drug designations by the FDA for the treatment of AML. In December 2018, SELLAS initiated enrollment of the Phase 1/2 open-label, non-comparative, multicenter, multi-arm study of GPS in combination with Merck’s anti-PD-1 therapy KEYTRUDA® in patients with selected WT1-positive advanced cancers, including both hematologic malignancies and solid tumors. This study, which is being conducted under a Clinical Trial Collaboration and Supply Agreement (CTSA) with Merck (known as MSD outside the United States and Canada), will assess the efficacy and safety of the combination, with exploratory long-term follow-up for overall survival and safety. The study will enroll approximately 90 patients at up to 20 centers in the United States. The initial tumor types to be treated will be acute myelogenous leukemia (AML) (patients unable to attain deeper morphological response than partial on hypomethylating agents and who are not eligible for allogeneic hematopoietic stem cell transplant) and ovarian cancer, to be followed by triple negative breast cancer (second line), small cell lung cancer, and colorectal cancer. Nelipepimut-S: Based on promising Phase 2b data presented in 2018, SELLAS is currently in continuing active discussions with the FDA regarding the optimal development path for NPS in triple negative breast cancer. In the Phase 2b study of trastuzumab +/- nelipepimut-S (NPS) in HER2 low-expressing breast cancer patient cohorts, trastuzumab + NPS demonstrated clinically and statistically significant efficacy in the TNBC cohort, with a p-value of 0.013 and a 75.2% reduction in risk of relapse or death. In October 2018, the Data Safety Monitoring Board (DSMB) unanimously concluded that the final analysis of the Phase 2b study data with a median follow-up of 26 months confirmed that TNBC patients should be the key target population for the development of trastuzumab + NPS in the adjuvant setting in early-stage HER2 1+/2+ breast cancer patients. A preplanned secondary efficacy analysis across human leukocyte antigen (HLA) allele subgroups from the Phase 2b study confirmed the therapeutic potential of NPS in patients with early-stage TNBC in the adjuvant setting across HLA types A-02, -03, -24 and -26, which cover approximately 80%-85% of the North American/European populations and 86%-90% of Asian/Pacific basin populations. Additional positive data from the Phase 2b study showed a clinically meaningful and statistically significant decrease in the number of clinically detectable relapses in the TNBC cohort with the combination of trastuzumab + NPS vs. trastuzumab alone. In addition, four pre-defined subgroups of TNBC patients in the trastuzumab + NPS arm demonstrated an average decrease of 84.2% in relative risk of relapse or death at 24 months. In a Type C meeting with the FDA, SELLAS discussed several key points of the clinical and regulatory strategy for NPS in combination with trastuzumab for TNBC, including potential for accelerated approval; a registration-enabling Phase 3 trial design and biostatistical plan; and the potential for breakthrough designation. SELLAS expects a further meeting with the FDA in early 2019 regarding the potential for breakthrough designation as well as an additional meeting in the first quarter of 2019 to reach agreement for a final development program for NPS in TNBC.