ONC206

ONC201, ONC206, and ONC212 are imipridones showing pro-apoptotic anti-cancer response...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...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.

P1, N=256, Recruiting, Sabine Mueller, MD, PhD | Trial completion date: Dec 2025 --> Dec 2027 | Trial primary completion date: Jan 2024 --> Jan 2026

Importantly, these results were validated in a 3D culture system with the sphere-forming and PC cell-derived organoid assays.ConclusionImipridones represent a novel approach to therapeutically target DRD2 and/or ClpP in PC. ONC206 shows more potent anti-cancer effects on PC cells than ONC201, paving the way for new effective therapeutics and better management of PC.

In the transgenic model of endometrial cancer, the combination of olaparib and ONC206 resulted in a more significant reduction in tumor weight in obese and lean mice compared to ONC206 alone or olaparib alone, together with a considerably decreased Ki-67 and enhanced H2AX expression in obese and lean mice. These results suggest that this novel dual therapy may be worthy of further exploration in clinical trials.

We treated DMG, GBM and HCC cells with imipridones, EHZ2i tazemetostat or HDACi panobinostat alone or combination of imipridones plus tazemetostat or panobinostat or the triple combination of imipridone plus tazemetostat and panobinostat. Shared regulated pathways in U251 included cell cycle arrest, cell adhesion, nervous system development, cell proliferation, negative regulation of proliferation, PERK-mediated unfolded protein response, extracellular matrix organization, regulation of transcription from RNA polymerase II promoter, and cellular response to hypoxia pathways. We conclude that imipridones ONC201, ONC206, and ONC212 which reduce EZH1 and EZH2 proteins share similar cytokine alterations, gene expression targets and actions with EZH2 inhibitors.

The effective CI of ONC206 plus tazemetostat and panobinostat ranges 0.27-0.77 in U251 GBM and 0.11-0.71 in SU-DIPG-13 DMG cells...The effective CI of ONC212 plus valemetostat ranges 0.33-0.83 in 22Rv1...The synergies between ONC201 and EZH1/2 or HDAC inhibitors provide clues for developing novel therapy for the mentioned tumors. Overexpression of EZH2 is in process to elucidate the role of EZH2 in the mechanism of the anti-cancer effect of ONC201.

We showed that activation of the mitochondrial ClpP protease by mutant ClpP (Y118A) or through utilization of second-generation imipridone compounds (ONC206 and ONC212) in combination with genetic interference of HDAC1 and HDAC2 as well as with global (panobinostat) or selective (romidepsin) HDAC inhibitors caused synergistic reduction of viability in GBM model systems, which was mediated by interference with tricarboxylic acid cycle activity and GBM cell respiration. Finally, utilizing GBM PDX models, we demonstrated that the combination treatment of HDAC inhibitors and imipridones prolonged host survival more potently than single treatments or vehicle in vivo. Collectively, these observations suggest that the efficacy of HDAC inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.

Our findings demonstrate that ONC206 has anti-tumorigenic effects in ovarian cancer as previously demonstrated by ONC201 but appears to be as well tolerated and more potent. Thus, ONC206 deserves further evaluation in clinical trials.

We investigated the anti-tumor effect of three imipridones (ONC201, ONC206, and ONC212), a promising new class of small molecules, in the treatment of neuroblastoma...Cell viability assays with HDAC inhibitors Vorinostat and Panobinostat demonstrated single-agent efficacy in vitro...However, further investigation is needed to determine synergy and mechanisms of synergy when histone deacetylase (HDAC) inhibitors are used in novel combinations with imipridones. Overall, our data reveals promise in imipridone therapy for neuroblastoma, and future studies are proposed to explore potential novel therapeutic combinations in this difficult-to-treat pediatric cancer.

ONC201 is an imipridone that selectively antagonizes the G protein-coupled receptors dopamine receptor D2 and D3 (DRD2/3) and activates human mitochondrial caseinolytic protease P (ClpP). Treatment with ONC206 led to a decrease in expression of Ki67, BCL-XL and phosphorylation of S6, as well as an increase in ClpP in endometrial tumors under both obese and lean conditions. Overall, the pre-clinical efficacy of ONC206 is promising and worthy of further exploration in clinical trials for endometrioid EC.

By integration of a transcriptome, metabolite and U-13C-glucose tracing analyses, we showed that activation of the mitochondrial ClpP protease through constitutively active ClpP (Y118A) or utilization of second-generation imipridone compounds (ONC206 and ONC212) in combination with genetic interference of HDAC1 and HDAC2 as well as with global (Panobinostat) and selective (Romidepsin) HDAC inhibitors caused synergistic reduction of viability in established, neuro-sphere and patient-derived xenograft (PDX) cultures of human GBM, which was mediated by interference with tricarboxylic acid cycle activity and GBM cell respiration. Finally, utilizing GBM PDX models, we demonstrated that the combination treatment of HDAC-inhibitors and imipridones reduced tumor growth and prolonged host survival more potently than single treatments or vehicle in vivo. Collectively, these observations suggest that the efficacy of HDAC inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.

We demonstrate synergy between ONC201, ONC206 and ONC212, and targeted therapies with known preclinical activity against DIPG...Six patient-derived DIPG cell lines (SU-DIPG-IV, SU-DIPG-13, SU-DIPG-25, SU-DIPG-27, SU-DIPG-29, SU-DIPG-36) were exposed to imipridones alone or combinations with histone de-acetylase inhibitors [HDACi], marizomib, etoposide, and temozolomide...Our results suggest increased sensitivity of H3K27M-mutant DIPG cell lines to second generation imipridone therapies, as compared to ONC201. Additionally, there is synergistic cell death with combination of imipridones and panobinostat, romidepsin, or marizomib, which may be further tested in vivo and in clinical trials.

The protein expression of tumorigenic NMYC, Sox-2, Oct-4, FABP5, and HMGA1 significantly decreased 48 h post-drug treatment, whereas cleaved PARP1/caspase-3 and γH2AX increased 72 h post-drug treatment, compared with vehicle-treated cells in the MYCN-amplified IMR-32 cell line. We are the first to report this novel differential protein expression after ONC201 or ONC206 treatment in human neuroblastoma cells, demonstrating an important multitarget effect which may yield added therapeutic benefits in treating this devastating childhood cancer.

Liver cancer cell lines Hep3B and HepG2 were treated with ONC201, ONC206, and ONC212 to determine dose-response effect...Combination treatment effect was also tested between ONC201 and the HDACi vorinostat, PARPi nariparib, and the proteasome inhibitor marizomib...These results suggest that the imipridone family of small molecules is a novel therapy for liver cancer with efficacy as a single agent and in combination with existing targeted agents. Future studies will clarify the mechanisms of synergy and expand the findings into small animal models.

We performed combinatorial drug treatment on Ewing sarcoma cell lines SK-N-MC and RD-ES with 3 imipridones (ONC201, ONC206, and ONC212) and 3 HDAC inhibitors (vorinostat, entinostat, and panobinostat). Cell viability studies and analysis with Compusyn demonstrate potent synergistic effects causing tumor cell death when imipridones are combined with HDAC inhibitors. Our work presents a novel therapeutic combination for the treatment of Ewing sarcoma.

Thus, ONC206 is a distinct agent that may be uniquely poised to address tumors that are not addressed by or have developed acquired resistance to ONC201. Our results indicate that for accurate prediction of ONC201 and ONC206 clinical benefit, a curated combinatorial biomarker approach for each tumor type, using diverse detection approaches such as protein expression, genomics, and transcriptomics, may be used in ongoing clinical trials.

Specifically, ONC206 utilizes ISR activation as a significant pathway in the propagation of its anti-proliferative and anti-metastatic effects. Thus, ONC206 may be a promising agent in future SEC clinical trials as was its predecessor ONC201.

Here, we showed that pharmacological activation of the mitochondrial ClpP protease through utilization of the novel imipridone compounds (ONC206 and ONC212) in combination with global (Panobinostat) and selective (romidepsin) HDAC – inhibitors caused synergistic reduction of viability in established and patient-derived xenograft (PDX) cultures of human GBM. Finally, using a PDX model, we demonstrated that the combination treatment of romidepsin and ONC206 reduced tumor growth more potently than single treatments or vehicle by enhanced reduction of cellular proliferation and pronounced induction of cell death in vivo. Collectively, these observations suggest that the efficacy of HDAC-inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.

ONC206 is a DRD2 antagonist and ClpP agonist that is a chemical derivative of ONC201, which is in Phase II clinical trials for H3 K27M-mutant glioma. Ongoing studies are further investigating tumor type enrichment of biomarkers. Prediction of innate imipridone sensitivity using biomarkers identified in this study may guide patient and tumor type selection in clinical trials.

The imipridone ONC206, a chemical derivative of ONC201, is an orally bioavailable dopamine receptor D2 (DRD2) antagonist that has anti-tumorigenic effects in EC via induction of apoptosis and activation of the integrated stress response. Olaparib and ONC206 had synergistic anti-proliferative effects in human endometrioid EC cell lines, suggesting that this novel dual therapy may be worthy of further exploration in clinical trials in EC.

The imipridone ONC206, a chemical derivative of ONC201, is a bioavailable dopamine receptor D2 (DRD2) antagonist that has anti-tumorigenic effects via induction of apoptosis and activation of the integrated stress response. ONC206 in combination with olaparib resulted in synergistic anti-tumorigenic and anti-metastatic effects in OC cell lines, suggesting that this novel dual therapy may be worthy of further exploration in clinical trials in OC.

Our data show potent anti-stem cell maintenance as well as anti-proliferative, anti-migratory, anti-viability and pro-apoptotic activity of both ONC201 and ONC206 on cancer cell lines, with ONC206 showing greater potency than ONC201. Our future directions include utilizing a combinatorial multi-modality therapy to treat a panel of pediatric and adult neurological tumors with ONC 201/206 and other selective inhibitors of tumorigenic pathways to completely eliminate the highly resistant sub-population of cancer stem cells, and delay malignant recurrence.

Objectives: ONC206 (Oncoceutics) is a selective dopamine receptor D2 (DRD2) antagonist and an analogue of ONC201, an imipiridone currently being investigated in phase II clinical trials for serous endometrial cancer (EC). Our results suggest that ONC206 demonstrates nanomolar potency for the inhibition of proliferation in serous EC cell lines. Specifically, ONC206 utilizes ISR activation as a significant pathway in the propagation of its anti-proliferative and anti-metastatic effects. Thus, ONC206 may be a promising agent in serous EC which has limited treatment options.

Objective: The impridone ONC201 (Oncoceutics), a dopamine receptor D2 (DRD2) antagonist, has antitumorigenic effects in preclinical studies, including high-grade serous (HGS) ovarian cancer (OC). ONC206 exhibited nanomolar potency for inhibiting OC cell growth and was efficacious in reducing OC tumor growth in both obese and lean mice. Thus, ONC206 may be a promising therapeutic agent to be explored in future clinical trials in HGSOC.

Objective: The impridone ONC201 (Oncoceutics), a dopamine receptor D2 (DRD2) antagonist, has antitumorigenic effects in preclinical studies, including high-grade serous (HGS) ovarian cancer (OC). ONC206 exhibited nanomolar potency for inhibiting OC cell growth and was efficacious in reducing OC tumor growth in both obese and lean mice. Thus, ONC206 may be a promising therapeutic agent to be explored in future clinical trials in HGSOC.

Objective: The impridone ONC201 (Oncoceutics), a dopamine receptor D2 (DRD2) antagonist, has antitumorigenic effects in preclinical studies, including high-grade serous (HGS) ovarian cancer (OC). ONC206 exhibited nanomolar potency for inhibiting OC cell growth and was efficacious in reducing OC tumor growth in both obese and lean mice. Thus, ONC206 may be a promising therapeutic agent to be explored in future clinical trials in HGSOC.

Objective: The impridone ONC201 (Oncoceutics), a dopamine receptor D2 (DRD2) antagonist, has antitumorigenic effects in preclinical studies, including high-grade serous (HGS) ovarian cancer (OC). ONC206 exhibited nanomolar potency for inhibiting OC cell growth and was efficacious in reducing OC tumor growth in both obese and lean mice. Thus, ONC206 may be a promising therapeutic agent to be explored in future clinical trials in HGSOC.

ONC201, a first-generation imipridone that antagonizes DRD2, has demonstrated clinical activity in Diffuse Midline Gliomas, H3K27M-mutant (DMGs). Exploratory analysis of DRD2 and DRD5 expression, DRD2 dimerization, expression of MYC and N-MYC in tumor tissue in relation to clinical outcomes will also be performed. Research Funding: Oncoceutics