Chimerix (United States)

Dordaviprone (ONC201) is a novel, small-molecule imipridone with antitumor activity in patients with a glioma. Six healthy male participants received a single 625-mg (100-µCi) oral dose of [14C]-dordaviprone. Blood, plasma, urine, and feces were collected up to 288hours after dosing and analyzed by liquid scintillation counting. Metabolite profiles were evaluated using liquid chromatography-radiometric detection, and metabolite identification was accomplished by liquid chromatography with tandem mass spectrometry. Concentrations of drug-derived radioactivity in blood and plasma peaked at 1 hour after dosing and were below the limit of quantitation by 72hours (whole blood) to 96hours (plasma) after dosing. Seventy-one percent of the administered radioactivity was recovered in urine and 20% in feces. In plasma, the major circulating compounds were dordaviprone and the inactive metabolite ONC207, each contributing approximately one third of the total radioactivity area under the curve. Of the 19 metabolites identified in plasma, no other single metabolite contributed more than 10% to the total radioactivity area under the curve. Unchanged dordaviprone was a minor component in excreta (less than 0.3%), with multiple metabolites identified in urine and feces. Given the lack of dordaviprone in excreta and the metabolites formed, the primary route for dordaviprone elimination was through urinary excretion of oxidative metabolites.

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with limited therapeutic options. ONC212 is a second-generation imipridone with antitumor effects in human PDAC cell lines. ONC212 has been shown to bind to mitochondrial protease ClpP, suppress ClpX, and impair oxidative phosphorylation by decreasing ATP production. While ONC212 has been evaluated in immunocompromised mice xenografted with human pancreatic tumors, ONC212 has not been evaluated, either alone or in combination with MEK and/or immune checkpoint inhibition (ICI), in immunocompetent mice bearing notoriously aggressive KrasLSL.G12D/+; Tp53LSL.R172H/+; Pdx1Cretg/+ (KPC) murine PDAC tumors. We hypothesized that, like human PDAC cells, KPC cells would demonstrate sensitivity to ONC212 both in vitro and in vivo. Our group has previously shown that ONC212 synergizes with trametinib to induce tumor cell death in human PDAC cells. We therefore hypothesized that this combination, together with ICI, would enhance KPC tumor cell death in vivo. Methods: We determined in vitro sensitivity of the KPC cells to ONC212 alone and in combination with trametinib using CellTiter-Glo® luminescent cell viability assays. Results were analyzed after 72 hours of incubation using Compusyn and Combenefit. In vivo experiments involved C57BL/6 mice that were injected subcutaneously with 3 × 105 KPCy cells in 100 mL of PBS/matrigel. To determine the ideal ONC212 dose, we tested five different doses/dosing frequencies (50 mg/kg; 25 mg/kg; 12.5 mg/kg given by oral gavage weekly or twice weekly) in tumor-bearing (50-75 mm3) mice. Mouse weight and tumor size was measured every four days. Treatment was stopped once tumor volumes reached 3,000 mm3 or if ulceration occurred. Once the ideal dose of ONC212 was determined, a study treating KPC tumor-bearing C57BL/6 mice with ONC212, trametinib, and ICI (anti-PD-1 mAb) alone and all possible doublet/triplet combinations was performed using the same methods. Results: We found that the combination of ONC212 and trametinib exhibited synergy in the KPC cell line in vitro. Our in vivo experiments revealed that ONC212 controlled KPC tumor growth in a dose-dependent manner, however, toxicity was also noted at higher, more frequent doses. While both 25 mg/kg and 50 mg/kg twice weekly were equally effective, 25 mg/kg was better tolerated and determined to be the ideal dose. In the combination therapy study, all treatments resulted in tumor reduction, as compared to the vehicle control; however, the triple therapy group had the lowest average tumor size at day twenty. Toxicity was noted in mice receiving at least two treatments, reflected by reduced weights and mobility. Further analysis of the tumor immune microenvironment using multiplex cytokine and immunofluorescence are ongoing. Citation Format: Jasper Chan, Alexis J. Lannigan, Grace Sun, Varun V. Prabhu, Robert Edwards, Leiqing Zhang, Lanlan Zhou, Wafik S. El-Deiry, Alexander Grenander Raufi. The imipridone ONC212 cooperates with MEK and immune checkpoint inhibition to elicit in vivo regression of KPC mouse pancreatic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2078.

Abstract Medulloblastoma is the most common malignant pediatric brain tumor with a for certain molecular subgroups very low overall survival and therefore an urgent need for novel treatment approaches. Dordaviprone (ONC201) and its chemical derivative with nanomolar potency ONC206 are inhibitors of the dopamine receptor 2 (DRD2) and more importantly induce apoptosis of cancer cells by activation of the mitochondrial caseinolytic protease P (ClpP). ONC201 has shown objective responses in patients with diffuse midline gliomas and is currently being evaluated in the Phase 3 ACTION study. ONC206 is currently in Phase I clinical trials for pediatric and adult patients with primary brain tumors. In this study, we evaluated the preclinical therapeutic effects of ONC206 in medulloblastoma in vitro and in vivo and investigated the molecular mode of action for this imipridone. We found evidence for high expression of ClpP at both the RNA and protein level in medulloblastoma tumours, compared to very low expression in normal brain and normal cerebellum. In addition, we saw a pronounced reduction in cell viability of human Group 3 and Group 4 and murine medulloblastoma cells treated with ONC206 with extremely low IC-50s (range: 14nM - 2μM).After treatment with ONC206, we observed a significant downregulation of mitochondrial electron transport chain complexes I and III and mitochondrial hyperpolarization, as well as an induction of the ATF4 pathway, thereby implying that ONC206 induces an integrated stress response and mitochondrial damage. In order to test the efficacy of ONC206 in vivo, we used murine models of SHH-driven and Group 3 medulloblastoma as well as Group 3 patient-derived xenografts (PDXs). ONC206 led to a significant prolongation of survival in both murine models, with the SHH mice demonstrating a remarkable survival benefit. Mice from both Group 3 PDXs also responded to ONC206, with 25% of ONC206 treated animals exhibiting long-term tumor-free survival. Our results highlight ONC206 as a novel attractive therapeutic option for patients with relapsed medulloblastoma and importantly pave the way for a clinical trial testing the efficacy of ONC206 in the treatment of these patients. Citation Format: Theophilos Tzaridis, Jingbo Liu, Varun Prabhu, Robert Wechsler-Reya, Tobey MacDonald. ONC206 inhibits tumour growth and is a potential novel therapeutic strategy for refractory medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5470.

Histone 3 (H3) K27M-mutant diffuse midline glioma (DMG) has a dismal prognosis with no established effective therapy beyond radiation. This integrated analysis evaluated single-agent ONC201 (dordaviprone), a first-in-class imipridone, in recurrent H3 K27M-mutant DMG. Fifty patients (pediatric, n = 4; adult, n = 46) with recurrent H3 K27M-mutant DMG who received oral ONC201 monotherapy in four clinical trials or one expanded access protocol were included. Eligible patients had measurable disease by Response Assessment in Neuro-Oncology (RANO) high-grade glioma (HGG) criteria and performance score (PS) ≥60 and were ≥90 days from radiation; pontine and spinal tumors were ineligible. The primary end point was overall response rate (ORR) by RANO-HGG criteria. Secondary end points included duration of response (DOR), time to response (TTR), corticosteroid response, PS response, and ORR by RANO low-grade glioma (LGG) criteria. Radiographic end points were assessed by dual-reader, blinded independent central review. The ORR (RANO-HGG) was 20.0% (95% CI, 10.0 to 33.7). The median TTR was 8.3 months (range, 1.9-15.9); the median DOR was 11.2 months (95% CI, 3.8 to not reached). The ORR by combined RANO-HGG/LGG criteria was 30.0% (95% CI, 17.9 to 44.6). A ≥50% corticosteroid dose reduction occurred in 7 of 15 evaluable patients (46.7% [95% CI, 21.3 to 73.4]); PS improvement occurred in 6 of 34 evaluable patients (20.6% [95% CI, 8.7 to 37.9]). Grade 3 treatment-related treatment-emergent adverse events (TR-TEAEs) occurred in 20.0% of patients; the most common was fatigue (n = 5; 10%); no grade 4 TR-TEAEs, deaths, or discontinuations occurred. ONC201 monotherapy was well tolerated and exhibited durable and clinically meaningful efficacy in recurrent H3 K27M-mutant DMG.

High-grade glioma (HGG) is the most common cause of cancer death in children and the most common primary central nervous system tumor in adults. While pediatric HGG was once thought to be biologically similar to the adult form of disease, research has shown these malignancies to be significantly molecularly distinct, necessitating distinct approaches to their clinical management. However, emerging data have shown shared molecular events in pediatric and adult HGG including the histone H3K27M mutation. This somatic missense mutation occurs in genes encoding one of two isoforms of the Histone H3 protein, H3F3A (H3.3), or HIST1H3B (H3.1), and is detected in up to 80% of pediatric diffuse midline gliomas and in up to 60% of adult diffuse gliomas. Importantly, the H3K27M mutation is associated with poorer overall survival and response to therapy compared to patients with H3 wild-type tumors. Here, we review the clinical features and biological underpinnings of pediatric and adult H3K27M mutant glioma, offering a groundwork for understanding current research and clinical approaches for the care of patients suffering with this challenging disease.

There is a demonstrated need for new chemotherapy options in pediatric oncology, as pediatric solid tumors continue to plateau at 60% with event-free survival. Imipridones, a novel class of small molecules, represent a potential new therapeutic option, with promising pre-clinical data and emerging clinical trial data in adult malignancies. ONC201, ONC206, and ONC212 are imipridones showing pro-apoptotic anti-cancer response. Using cell viability assays, and protein immunoblotting, we were able to demonstrate single-agent efficacy of all 3 imipridones inducing cell death in pediatric solid tumor cell lines, including osteosarcoma, malignant peripheral nerve sheath tumors, Ewing sarcoma (EWS), and neuroblastoma. ONC201 displayed IC50 values for non-H3K27M-mutated EWS cell lines ranging from 0.86 µM (SK-N-MC) to 2.76 µM (RD-ES), which were comparable to the range of IC50 values for H3K27M-mutated DIPG cells lines (range 1.06 to 1.56 µM). ONC212 demonstrated the highest potency in single-agent cell killing, followed by ONC206, and ONC201. Additionally, pediatric solid tumor cells were treated with single-agent therapy with histone deacetylase inhibitors (HDACi) vorinostat, entinostat, and panobinostat, showing cell killing with all 3 HDACi drugs, with panobinostat showing the greatest potency. We demonstrate that dual-agent therapy with combinations of imipridones and HDACi lead to synergistic cell killing and apoptosis in all pediatric solid tumor cell lines tested, with ONC212 and panobinostat combinations demonstrating maximal potency. The imipridones induced the integrated stress response with ATF4 and TRAIL receptor upregulation, as well as reduced expression of ClpX. Hyperacetylation of H3K27 was associated with synergistic killing of tumor cells following exposure to imipridone plus HDAC inhibitor therapies. Our results introduce a novel class of small molecules to treat pediatric solid tumors in a precision medicine framework. Use of impridones in pediatric oncology is novel and shows promising pre-clinical efficacy in pediatric solid tumors, including in combination with HDAC inhibitors.

Abstract Purpose of the work: Pediatric High Grade Gliomas (pHGGs), including Diffuse Midline Gliomas (DMGs), are very aggressive solid tumors developed during childhood with a poor overall survival underscoring the need for effective treatments. The adenovirus Delta-24RGD and the imipridone ONC201 have demonstrated safety and effectiveness in preclinical models and clinical trials. Thus, we evaluated the therapeutic efficacy of the Delta-24-RGD/ONC201 combination and analyzed possible changes in the tumor microenvironment in preclinical models of pHGGs and DMGs. Experimental procedures: A battery of pHGGs (SF188 and CHLA-03-AA), human DMG (SU-DIPG IV), and murine DMG cell lines (XFM and NP-53) were used. We assessed the viral replication by hexon titration, the protein expression amount (E1A, fiber, and mTORC1 key proteins)by immunoblotting, and oxygen consumption by Seahorse Analyses. Viability was measured by MTS. CHLA-03-AA and XFM were engrafted orthotopically in athymic nude mice and Balb/c mice, respectively. To assess in vivo efficacy, the animals were treated with Delta-24-RGD (107 PFU/animal) or PBS, followed by ONC201administration (125 mg/kg/twice/weekly). The tumor immune microenvironment was evaluated by flow cytometry. Results: First, the potential adverse interactions between both agents were checked in vitro, showing that ONC201 cotreatment did not interfere with the Delta-24-RGD replication capacity. As expected, ONC201 treatment led to a reduction in oxygen consumption, which was also observed in the combination treatment. Evaluation of cytotoxicity in a panel of cell lines showed that the combination was significantly better than either agent alone. In vivo, CHLA-03-AA bearing mice treated with the combination showed a significant increase in the median overall survival (PBS: 48 days; ONC201: 54.5 days; Delta-24-RGD: 62 days; Delta-24-RGD/ONC201: 95 days (P=0.0008)), leading to 20%long-term survivors, free of disease. Evaluation of the combination in an immunocompetent orthotopic DMG model also revealed the superior efficacy of the Delta-24-RGD/ONC201 (PBS: 11 days; ONC201: 12 days; Delta-24-RGD: 12 days; ONC201+Delta-24-RGD: 15 days (P=0.02)). Of importance, the combination treatment resulted in the reshaping of the tumor microenvironment towards a proinflammatory phenotype (T cells, NK cells, macrophages, granulocytes, monocytes, dendritic cells, and microglia). Conclusions: Our data indicate that the combination Delta-24-RGD/ONC201 generates a pro-inflammatory microenvironment that ultimately leads to a superior therapeutic effect in preclinical pHGG and DMGs models. Citation Format: Daniel de la Nava, Javier Marco-Sanz, Virginia Laspidea, Sara Labiano, Iker Ausejo-Mauleon, Reyes Hernandez-Osuna, Sabine Mueller, Javad Nazarian, Joshua E. Allen, Oren Becher, Juan Fueyo, Candelaria Gomez-Manzano, Ana Patiño-Garcia, Marta M. Alonso. The adenovirus Delta-24-RGD in combination with ONC201 provides a therapeutic benefit and a proinflammatory recruitment in preclinical models of pHGGs and DMGs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2000.