Based on a clinical staged small molecular hClpP activator ONC201, a class of novel hClpP agonists with a [1,8]naphthyridinone scaffold were designed, synthesized and evaluated in a series of biochemical and biological assays. Mechanism studies for the representative compound F20 indicated that it can potently bind to and activate hClpP, efficiently promote the degradation of hClpP substrates, robustly induce ATF4/CHOP regulated integrated stress responses, strongly inhibit cell growth and effectively induce apoptosis in a subset of cancer cell lines. F20 showed good PK profiles when dosed by intravenous injection and exhibited moderate oral bioavailability in mice.

We investigated cell viability, drug synergies, pERK suppression and cytokine, chemokine or growth factor alterations following treatment with 5-Fluorouracil (5-FU) or ONC212 plus MRTX1133 in 6 human CRC and 4 human pancreatic cancer cell lines. Our studies reveal preclinical activity of MRTX1133 alone or synergies when combined with 5-FU or ONC212 against mCRC and pancreatic cancer cells regardless of KRAS G12D mutation. The results suggest that KRAS G12V and KRAS G13D should be further considered in clinical trials including combination therapies involving MRTX1133 and 5-FU or ONC212.

Imipridones are a promising strategy for further testing and development in mUM.

P1, N=20, Active, not recruiting, University of Nebraska | Trial primary completion date: Aug 2024 --> Oct 2026

P1/2, N=120, Recruiting, M.D. Anderson Cancer Center | Trial completion date: Nov 2024 --> Nov 2026 | Trial primary completion date: Nov 2024 --> Nov 2026

Moreover, inhibition of caspase-9 activity unexpectedly augmented, rather than attenuated, caspase-3 activation and the subsequent cell death. Collectively, our research identifies ONC212 as an atypical mitochondrial-independent, yet Bcl-2/Bcl-xL-inhibitable, caspase-3-mediated apoptotic cell death inducer, highlighting its potential for combination therapies in tumors with defective mitochondrial apoptotic signaling.

The results support the idea that treatment of castrate-resistant prostate cancer by imipridones may not be significantly impacted by neuroendocrine differentiation as a therapy-resistance mechanism. The results support further testing of imipridones across subtypes of androgen-sensitive and castrate-resistant prostate cancer.

Our results have relevance to activity of ONC201 in PCa where most castrate-resistant androgen-independent cancers are not therapy resistant due to NET differentiation. Importantly, NET differentiation does not promote resistance to ONC201 supporting further clinical investigations across the spectrum of PCa.

Based on the founding member of imipridones, ONC201, a class of dehydrogenated imipridone derivatives was designed, synthesized, and evaluated in a series of biochemical and biological assays as human caseinolytic protease P (hClpP) activators...More importantly, XT6 exhibited a promising pharmacokinetic profile in rats and could penetrate the blood brain barrier. It showed highly potent in vivo antitumor activity in a MIAPACA2 cell line derived pancreatic cancer model in BALB/c nude mice.

P2, N=27, Not yet recruiting, University of Nebraska | Phase classification: P1 --> P2

P1, N=58, Recruiting, UNC Lineberger Comprehensive Cancer Center | Trial completion date: Jan 2025 --> Jul 2025

P1, N=27, Not yet recruiting, University of Nebraska | Initiation date: Apr 2024 --> Jul 2024

P1/2, N=17, Terminated, Chimerix | Active, not recruiting --> Terminated; This study was terminated due to a change in corporate priorities. The decision to terminate the study was not based on any safety concerns.

DNMG with H3K27M mutations share many similarities with their midline counterpart, suggesting that they correspond to a rare anatomical presentation of these tumors. This is of paramount importance, as they may benefit from new therapeutic approaches such as ONC201.

The imipridones ONC201 and ONC206 induce mitochondrial dysfunction and have emerged as promising therapies for DMG patients. Clinical translation of our studies has the potential to enable precision metabolic therapy and imaging for DMG patients. Imipridones induce GABA accumulation in diffuse midline gliomas, an effect that can be leveraged for therapy and non-invasive imaging.

Here, we applied the principles of computer-aided drug discovery to identify a novel low-molecular-weight compound, TLR inhibitory compound 10 (TIC10), and its potent derivative (TIC10g), which demonstrated dual inhibition of TLR7 and TLR9 signaling pathways...Western blot analysis revealed that TIC10g downregulated the phosphorylation of the p65 subunit of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPKs), including extracellular-signal-regulated kinase, p38-MAPK, and c-Jun N-terminal kinase. These findings indicate that the novel ligand, TIC10g, is a specific dual inhibitor of endosomal TLRs (TLR7 and TLR9), disrupting MAPK- and NF-κB-mediated proinflammatory gene expression.

P2, N=360, Recruiting, University of California, San Francisco | Phase classification: P1/2 --> P2

The mechanism of impairment of ONC201/206/212 effect caused by dopamine pre-treatment appears to involve upregulation of anti-apoptotic p-Bad, XIAP, FLIP and pAkt. Our results shed light on mechanisms of cancer cell protection by dopamine after imipridone treatment, heterogeneity among different tumor cell types, and suggest that effects of dopamine adaptation on tumor cells may impact on cell survival pathways in ways that may or may not depend on expression of dopamine receptors.

P1/2, N=360, Recruiting, University of California, San Francisco | Phase classification: P2 --> P1/2 | Trial completion date: Jun 2027 --> Jun 2029

The pharmacological activation of ClpP using TIC10, currently in phase III clinical trials for cancer, successfully replicates this phenotype both in vitro and in vivo and markedly reduces aneurysm development in a mouse model of elastase-induced aortic aneurysms. Our mechanistic exploration indicates that ClpP activation regulates the VSMC phenotype by modifying the cellular NAD+/NADH ratio and activating Sirtuin 1. Our findings reveal the crucial role of mitochondrial proteostasis in the regulation of the VSMC phenotype and propose the ClpP protease as a novel, actionable target for manipulating the VSMC phenotype.

The IHC of the excised tumor grafts further confirmed the higher apoptosis and lower metastasis and cell proliferation. Thus, our MUC1 targeting binary drug-releasing liposomal formulation showed higher drug payload, enhanced plasma stability, and accumulation of drugs in the pancreatic orthotopic tumor and thus is a promising therapeutic alternative for the treatment of PDAC.

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.