Salarius Pharmaceuticals, Inc. announced that the U.S. Food and Drug Administration (FDA) has removed its partial clinical hold on Salarius' Phase 1/2 Ewing sarcoma clinical trial evaluating seclidemstat, Salarius' novel oral, reversible, targeted LSD1 inhibitor. The FDA previously granted seclidemstat Fast Track Designation, Orphan Drug Designation and Rare Pediatric Disease Designation for Ewing sarcoma. Previously Reported Seclidemstat Clinical Data In December 2022 Salarius reported interim clinical results from its Phase 1/2 trial showing that treatment with seclidemstat in combination with topotecan and cyclophosphamide had 60% confirmed disease control and 7.4 months median time to tumor progression for Ewing sarcoma first-relapse patients.

The results also suggest that first- and second- relapse Ewing sarcoma patients treated with seclidemstat in combination with topotecan and cyclophosphamide who achieve disease control may have an increased time to tumor progression (TTP) compared with treatment of topotecan and cyclophosphamide alone, per published data from the Phase 3 rEECur (International Randomized Controlled Trial of Chemotherapy for the Treatment of Recurrent and Primary Refractory Ewing Sarcoma) study. At ASCO 2022 the Euro Ewing Consortium presented rEECur Phase 3 study results in relapsed/refractory Ewing sarcoma patients that showed median event-free survival of 3.5 months in the topotecan/cyclophosphamide arm (n=73) compared with 5.7 months in the high-dose ifosfamide arm (n=73). The rEECur data includes approximately 80% primary refractor or first-relapse.

Ewing sarcoma patients after relapse have 5-year overall survival of about 13% and 10-year overall survival of about 9%.(1) Single- agent activity has not been observed in the FET-rearranged sarcoma cohort of the trial. In December 2022 investigators in the Department of Leukemia at the University of Texas MD Anderson Cancer Center (MD Anderson) presented clinical data on seclidemstat in patients with MDS or CMML at the 64(th) American Society of Hematology Annual Meeting showing no serious adverse events were reported, and that all adverse events observed in the study were manageable. Of the eight evaluable patients, four (50%) had an objective response including one complete response patient who planned to receive potentially curative allogeneic stem cell transplantation, two marrow complete responses plus hematological improvement and one marrow complete response.

The Phase 1 dose-escalation portion of this trial is designed to evaluate up to six dose levels of seclidemstat. The maximum tolerated dose, which will inform the Phase 2 portion of the trial, had not yet been reached.