DIPG-84. PHASE 1 DOSE-ESCALATION STUDY OF ACT001 IN PEDIATRIC PATIENTS WITH ADVANCED BRAIN AND SOLID TUMORS SHOWS ACTIVITY IN DIFFUSE MIDLINE GLIOMA (DMG)

Abstract

Abstract BACKGROUND ACT001, an oral parthenolide derivative targeting STAT3 and NF-κB pathways, has shown activity in preclinical models of DMG. We evaluated safety, toxicity and activity of ACT001 in this recently completed, first-in-child study of DMG and other relapsed/refractory brain and solid tumors. METHODS Eligible patients ≥ 1 and ≤ 21 years old were enrolled with dose escalation following a rolling 6 design and tumor lesions evaluated every 8 weeks per RANO/ RECIST criteria. RESULTS A total of 29 patients were enrolled across 5 cohorts, including 19 with DMG (13 with Diffuse Intrinsic Pontine Glioma (DIPG)). Median age was 11 years for the whole cohort and 7 years (3-17) for DMG patients. Safety was evaluated in escalating doses in 188, 533, 700, 875 and 1100 mg/m2,BID cohorts. No DLT nor grade 3 and above TRAE was identified. One SUSAR was noted for a grade 1 pain in extremity event. Peak ACT001 concentration for each dose cohort were estimated based on limited PK sampling time (cycle 1 day 1 at pre-dose, 2 and 4 hours post dose; cycle 1 day 15 and cycle 2 day 1 both at pre-dose). ACT001 peak concentration plateaued at the highest dose levels, fluctuating in the range of 6360, 5430 and 5980 mg/m2 for 700, 875 and 1100 mg/m2 cohorts respectively. The half-life was approximately 3 hours. 8/14 DMG patients treated at ≥ 700 mg/m2 exhibited objective response or stable disease (SD), including one patient with SD for 14 months, another patient with confirmed Partial Response who remained on study for 11-months before disease progression and five other patients with different degrees of tumor burden reduction. CONCLUSION ACT001 was well tolerated and showed preliminary evidence of anti-tumor activity in DMG/DIPG patients dosed at the highest dose levels. A Phase 2 trial is planned using 875 mg/m2 as the RP2D.