P2, N=324, Recruiting, University of California, San Francisco | Active, not recruiting --> Recruiting | N=143 --> 324

The continuous treatment of U937 cells with the benzene metabolite hydroquinone (HQ) generated U937/HQ cells, exhibiting enhanced responsiveness to the cytotoxic effects of ONC212...Collectively, our data suggested that ONC212 upregulated SLC35F2 expression and triggered NOXA-mediated MCL1 degradation in U937, U937/HQ, and HL-60 cells by activating the AKT/NOX4/HuR/ATF4 pathway. The ONC212-induced signaling pathway showed anti-AML activity and enhanced YM155 cytotoxicity.

H3K27M-mutant diffuse gliomas occasionally occur in nonmidline cerebrum. ONC201 exhibits activity in H3K27M-mutant gliomas irrespective of CNS location.

Despite advances in treatment, a significant proportion of patients with chronic lymphocytic leukemia (CLL) will relapse with drug-resistant disease.The imipridones, ONC-201 and ONC-212, are effective against a range of different cancers, including acute myeloid leukemia (AML) and tumors of the brain, breast, and prostate. These drugs induce cell death through activation of the mitochondrial protease, caseinolytic protease (CIpP), and the unfolded protein response (UPR).Here we demonstrate that the novel imipridone analog, TR-57, has efficacy as a single agent and synergises with venetoclax against CLL cells under in vitro conditions that mimic the tumor microenvironment. Changes in protein expression suggest TR-57 activates the UPR, inhibits the AKT and ERK1/2 pathways and induces pro-apoptotic changes in the expression of proteins of the BCL-2 family.The study suggests that TR-57, as a single agent and in combination with venetoclax, may represent an effective treatment option for CLL.

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

We previously developed ZG111, a potent ClpP agonist derived from ICG-001, inhibits the proliferation of pancreatic ductal adenocarcinoma cell lines in vitro and in vivo by degrading respiratory chain complex proteins...Finally, ZG36 treatment inhibited 3-D cell growth in vitro and suppressed the tumorigenesis of AML cells in xenografted mice models. Collectively, we developed a new class of human ClpP agonists that can be used as potential antileukemic therapies.

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.

In vitro results suggest that targeting the ClpP protein in CRC leads to mitochondrial dysregulation and CRC cell death.

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.

Our data provide evidence for synergy from the combination of ONC201 and ABT-263 against human solid tumor cell lines associated with alterations in cell death and pro-survival mediators. The combination of ONC201 and ABT-263 merits further exploration in vivo and in clinical trials against a variety of solid malignancies.

Venetoclax-resistant cells also exhibited an upregulation of the PI3K/Akt pathway, and pharmacological inhibition of Akt and ERK with TIC-10 led to cell death in all venetoclax-resistant cell lines. Overall, we highlight the importance of targeted therapies, such as TIC-10, against venetoclax resistance-related pathways, which might represent future therapeutic prospects.

Furthermore, ONC201 treatment significantly decreased MYCN protein expression and suppressed tumor formation with the reactivation of ATRX expression in MYCN-amplified NB-cell-derived xenograft tumors. Taken together, ONC201 could be the potential agent to provide diversified therapeutic application in NB, particularly in NB with MYCN amplification.

Together our data revealed that the effects of a single dose of ONC201 are dependent on the duration of exposure, specifically, while short-term exposure led to reversible changes; long-term exposure resulted in irreversible transformation of cells associated with the senescent phenotype. Our data further demonstrated that when used in combination with NK cells, ONC201 created a synergistic anti-cancer effect, thus suggesting its possible benefit in NK-cell based cellular immunotherapies for cancer treatment.

P1, N=24, Not yet recruiting, National Cancer Institute (NCI)

Key exclusion criteria include a history of acute graft-versus-host disease (GVHD) grade III/IV; initiation of any new systemic immunosuppressive agent for GVHD within 4 weeks of enrollment, current use of prednisone at a dose of ≥0.25 mg/kg/day; uncontrolled serious infection; active ischemic heart disease, heart failure or arrhythmia; severe chronic obstructive pulmonary disease; resting O2 saturation 2 times the upper limit of normal; and creatinine clearance <30 mL/min. Clinical studies in solid malignancies have indicated that ONC201 can expand and activate NK cells in peripheral blood, or recruit CD8+ T-cells to the tumor. Hence, the study will assess expansion and activation of NK and T cell populations in peripheral blood and utilize transcriptomic analyses of NK and T cells to explore the mechanisms behind the immunologic changes.

The adult 625 mg weekly RP2D of ONC201 scaled by body weight was well tolerated. Further investigation of ONC201 for DMG/DIPG is warranted.

We demonstrate that GPX4 inhibition with doxycycline-inducible shRNA or the specific inhibitor ML210 induces ferroptosis in leukemia cells, evidenced by iron-dependent lipid peroxidation and blockade of cell death by the iron chelator deferoxamine. Of note, the classical ferroptosis inducers (xCT inhibitors) sulfasalazine and sorafenib did not induce ferroptosis in AML cells, suggesting a specific relevance of GPX4 in AML ferroptosis...Consistently, degradation of the respiratory complex with hyperactivation of mito-protease ClpP by imipridone ONC212 sensitized cells to GPX4 inhibition in HL60 parental cells but not in rho0 cells, further supporting the role of mito-respiration in the protection of cells against ferroptosis. As venetoclax (Ven) is one of the most widely used mitochondria-targeting agents in AML that also inhibits mito-respiration, we tested the combination of GPX4 inhibitor ML210 and Ven...Unexpectedly, and as a novel mechanism of GPX4 inhibition-mediated ferroptosis, we found that ML210 induces BAX/BAK-independent cytochrome C release from mitochondria, which is blocked by MitoQ... Our data suggest therapeutic potential of ferroptosis induction in AML by targeting GPX4 with the mechanistic involvement of mito-respiration. The combination of GPX4 and BCL-2 inhibition is synergistic and capable of overcoming Ven resistance. Studies are in progress to elucidate the molecular link between mito-respiration/redox and cytochrome C release and to investigate ferroptosis induction in vivo.

P3, N=368, Recruiting, Gustave Roussy, Cancer Campus, Grand Paris | Not yet recruiting --> Recruiting

GPX4 inhibition induces ferroptosis involving mitochondrial redox machinery in AML. Combinatorial targeting of mitochondrial respiration with GPX4 inhibition exerts synergistic anti-leukemia effects. Further studies are in progress to assess the molecular mechanisms and the in-vivo efficacy of the combinatorial treatments.

In vivo, ONC201 promoted the expression of EMILIN-3, a TGF-β antagonist that is known to inhibit HLA-A/B2M expression, possibly explaining the increased MHC-I activity. This study uncovers a novel link between treatment of DMG with ONC201 and paxalisib and the role dopaminergic peripheral nerves signaling may play on the sequestration of T cells within lymphoid organs and lymphopenia.

TR-107 showed ClpP-dependent growth inhibition in the low nanomolar range that was equipotent to paclitaxel in triple-negative breast cancer (TNBC) cell models...The pharmacokinetic properties of TR-107 were compared with other known ClpP activators including ONC201 and ONC212...ClpP activation in vivo was validated by immunoblotting for TFAM and other mitochondrial proteins. In summary, we describe the identification of highly potent new ClpP agonists with improved efficacy against TNBC, through targeted inactivation of OXPHOS and disruption of mitochondrial metabolism.

P1, N=20, Recruiting, Vijaya Bhatt | Trial completion date: Jul 2024 --> Jul 2025 | Trial primary completion date: Jul 2022 --> Jul 2023

P3, N=368, Not yet recruiting, Gustave Roussy, Cancer Campus, Grand Paris

Serum analysis indicated a decrease in pro-inflammatory serum biomarkers, such as IL1β, IL6, TNFα, G-CSF, and GM-CSF, in the ONC201-treated mice compared with controls. Our data demonstrated excellent chemopreventive potential of orally administered ONC201 against intestinal tumorigenesis in the AOM-Apc mouse model.

The inhibitory activity of compound IIc (25 mg/kg) in the HCT-116 xenograft model was significantly greater than those of the positive control drugs (ONC201, chidamide). These findings suggested that development of highly TRAIL-sensitive HDAC inhibitors as colorectal tumor cancer drugs.

However, 2-day pre-treatment with epigenetic drugs (Vorinostat, Tazemetostat, Valemostat and Azacytidine) and 7-day pre-treatment with Tazemetostat + Azacytidine had no effect on Ven sensitivity...Inhibition of mTORC1 with Everolimus abrogated the toxic effect of Ven in the maternal cell lines (figure 1E), whereas TIC-10, an AKT/MEK inhibitor, partially restored Ven sensitivity in MAVER1-VR and MINO-VR cell lines (figure 1D)...The PI3K-AKT-mTOR pathway appears to be involved in Ven resistance development, since interestingly, mTOR inhibition leads to a decreased response to Ven treatment in maternal cell lines but AKT inhibition leads to an increased response in -VR cell lines. Ven resistance in MINO-VR appears to be driven primarily by decreased mitochondrial priming, whereas MAVER-VR appears to be driven by decreased mitochondrial priming combined with a switch from BCL2 to MCL1 dependence.

ONC201 is an oral selective antagonist of the dopamine D2 receptor and direct activator of caseinolytic protease P. In a phase II study, ONC021 was shown to be well tolerated with notable efficacy in patients with the rare neuroendocrine neoplasms pheochromocytomas-paragangliomas, although biomarkers for activity remain to be elucidated. See related article by Anderson et al., p. 1773.

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.

While these therapies showed potency against the cell lines derived from SCLC patients, it is noteworthy that the combination showed significantly less toxicity to healthy human lung epithelial cells. Future studies could explore the combination of ONC201 and lurbinectedin in SCLC cell lines, SCLC patient-derived organoids, other tumor types, including in vivo studies and clinical translation.

Since Sal003 is not yet available for clinical testing in humans, we will next investigate treatment with ONC201 and the well-tolerated ATF4 inducer fenretinide. The combination of ONC201 with another ISR activating agent has the potential to serve as a therapy for DIPG.

We are currently exploring the novel combination and potential underlying mechanisms behind the synergistic effects of the triple drug treatment. Future studies will evaluate this triple drug combination treatment in mouse models of SCLC.

These effects indicate effectiveness of the combinatorial treatment in causing DNA damage and instability, inducing double-stranded DNA breaks, as well as initiating the intrinsic apoptosis pathway through the integrated stress response, selectively in the malignant cells. Ongoing directions include testing similar concentrations of both ONC201 and lurbinectedin in additional SCLC cell lines, SCLC patient-derived organoids, and in vivo, as well as exploring immune correlates of the drug treatments.

Our data provide evidence for synergy from the combination of ONC201 and ABT-263 against human solid tumor cell lines associated with alterations in cell death and pro-survival mediators. The combination of ONC201 and ABT-263 merits further exploration in vivo in a variety of solid malignancies.