Atrt-13. Novel Acylfulvene Lp-184 Synergizes With Rucaparib to Kill at/Rt Cells

Abstract BACKGROUND Atypical Teratoid Rhabdoid Tumor (AT/RT) is a pediatric brain cancer with survival rates of less than 40%. Illudins are a novel class of DNA-damaging alkylating agents. LP-184, an investigational synthetic acylfulvene analog currently in a first-in-human Phase 1 trial, exhibits enhanced ability to penetrate the brain and damage DNA in tumor cells. We hypothesized that LP-184 would synergize with PARP inhibitors such as rucaparib which inhibit DNA repair. The combination of these therapies could be a promising treatment option for AT/RT. METHODS We tested LP-184 against the AT/RT cell lines BT37, CHLA06, CHLA05, and CHLA266. Cell viability assays were conducted by flow cytometry. Immunofluorescence was performed to visualize CC3 and BrdU. Western blots were performed to determine c-PARP and p-RB protein levels. Synergy experiments were performed using cell growth inhibition as the readout and quantified using the SynergyFinder online computational tool. RESULTS LP-184 suppressed AT/RT proliferation at nanomolar concentrations as measured by BrdU immunofluorescence and pRB western blots (BrdU BT37 p=0.0001, CHLA06 p=0.0001, CHLA05 p=0.033 50 nM concentration of LP-184 compared to DMSO control). Furthermore, LP-184 showed strong synergy with the PARP inhibitor rucaparib. Viable cell count was reduced by as much as 80% in combination compared to DMSO control (BT37 p=0.0001, CHLA06 p=0.0002, CHLA05 p=0.0077). Combination therapy decreased proliferation as measured by immunofluorescence and confirmed by pRB western blots (BrdU BT37 p=0.0004, CHLA06 p=0.0033, CHLA05 p=0.0154 compared to DMSO control). LP-184 and rucaparib induced apoptosis as measured by cleaved caspase 3 (CC3) and cPARP western blots (BT37 p=0.0002, CHLA06 p=0.0117, CHLA05 p=0.0001 %CC3+ compared to control). Survival studies in vivo are underway to test single agent and combination therapies of LP-184 and rucaparib in AT/RT. CONCLUSION LP-184 and rucaparib together could provide a compelling clinical option for patients with this poor-prognosis brain tumor.