ATRT-14. Novel Agent LP-184 and Spironolactone Extend Mouse Survival in Atypical Teratoid Rhabdoid Tumor

Abstract Atypical Teratoid Rhabdoid Tumor (AT/RT) is a pediatric brain cancer with survival rates below 40%. Illudins are a novel class of DNA-damaging alkylating agents that show efficacy against pediatric solid tumors. LP-184, a newly synthesized illudin, demonstrates an enhanced ability to penetrate the brain and damage DNA in tumor cells. We hypothesized that LP-184 would synergize with DNA damage repair inhibitors. Spironolactone, a diuretic with good brain penetration, inhibits nucleotide excision repair by facilitating the ubiquitin-mediated degradation of ERCC3, which is overexpressed in AT/RT tumors. The combination of spironolactone and LP-184 could offer a promising treatment for AT/RT. As a single agent, LP-184 suppressed AT/RT cell lines at nanomolar concentrations (CHLA06 IC50 = 17.52 nM, BT37 IC50 = 17.94 nM, CHLA05 IC50 = 11.57 nM, CHLA266 IC50 = 44.45 nM). Immunofluorescence and western blot assays confirmed that LP-184 reduced proliferation and induced apoptosis. LP-184 showed strong synergy with spironolactone, significantly reducing viable cell count in combination compared to DMSO control (BT37 = 0.0242, CHLA06 = 0.0007, CHLA05 = 0.0004). Survival studies of BT37 orthotopic xenografts in mice showed that LP-184 alone significantly reduced tumor growth (IVIS imaging) and extended survival (median survival: control = 66, spir = 53, LP = 98, combination = 113, p = 0.0007), though the combination did not markedly improve survival. However, CHLA06 xenografts showed a significant survival benefit with the combination treatment (control = 27 days, combination = 75 days, p = 0.0018). Our data suggest that LP-184 is effective as a monotherapy and is potentiated by spironolactone to reduce cell growth in vitro and extend survival in vivo. The combined treatments could provide a compelling clinical option for patients with this poor-prognosis brain tumor. Our work may inform the planned early phase clinical trials of LP-184 in children.