Abstract 523: Minnelide as a potential treatment strategy for CIC::DUX4 sarcoma

Background: CIC::DUX4 Sarcoma (CDS) is driven by t(4;19) or t(10;19) chromosomal translocations and is associated with high rates of metastasis, chemoresistance, and poor outcomes. Previously classified as “Ewing-like sarcoma” due to overlapping morphological and immunobiological features, CDS differs from Ewing sarcoma in several key aspects: it rarely arises in bone, lacks the Ewing-defining ETS gene fusion, and has a more aggressive clinical course. Despite recent reclassification by the World Health Organization as its own entity, CDS patients are still treated with ineffective Ewing-based chemotherapies. This study evaluates the therapeutic potential of 160 compounds in human CDS cells, identifying Triptolide as a top candidate. Minnelide, the water-soluble prodrug of Triptolide, is currently undergoing Phase I/II trials for various cancers, including pancreatic and gastric cancer. Methods: We conducted a viability drug screen on human CDS cells using a Tocriscreen compound library. The top hit, Triptolide, was subsequently validated using its water-soluble prodrug, Minnelide, which replicated the screen results. To investigate the mechanism of action, cells were treated for 72 hours at the IC50 concentration and processed for RNA sequencing. Finally, we modeled CDS by generating subcutaneous xenograft tumors in immunodeficient NSG mice. Mice were transplanted with CDS tumor-derived cells and treated with Minnelide (or vehicle control) once daily for 21 days. The drug doses (0.21 mg/kg and 0.27 mg/kg) were selected based on bioavailability data and maximum tolerability observed in Phase I/II clinical trials. Results: Minnelide treatment decreased CDS cell viability and significantly reduced the growth of CIC::DUX4 sarcoma xenografts within 21 days. The Phase I clinical trial data indicates that the recommended starting dose for patients is 0.67 mg/m2, which corresponds to a dosage of 0.21 mg/kg in mice. The average tumor volume of the 0.21 mg/kg Minnelide treatment group was significantly (two-way ANOVA, P = 0.0001) lower than that of the control group at day 21 post-treatment initiation. Moreover, drug treatment was not associated with any adverse side effects. RNA sequencing and western blot analysis of CDS cells treated with Minnelide revealed downregulation of many CIC::DUX4 target genes, such as ETV1/4/5 and DUSP6. These results suggest that Minnelide alters the CDS transcriptional program and could represent an efficacious treatment alternative. Conclusion: Therapeutic advancements for CIC::DUX4 sarcoma have been limited to date, and there are currently no clinical trials available for CDS patients. Our findings demonstrate that Minnelide effectively reduces CDS cell viability and xenograft growth, while downregulating key CIC::DUX4 target genes. Given the role of CIC::DUX4 as a potent transcriptional activator, Minnelide's disruption of this activation may offer a promising therapeutic approach for CDS. Citation Format: MaKenna R. Browne, Peter G. Hendrickson, David G. Kirsch. Minnelide as a potential treatment strategy for CIC::DUX4 sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 523.