ONC201 and imipridones: Anti-cancer compounds with clinical efficacy

ONC201 exerts oncogenic effects beyond its mitochondria-disturbing role in neuroblastoma subsets

Neuroblastoma (NB) is a formidable challenge in pediatric oncology due to its intricate molecular landscape, necessitating multifaceted therapeutic approaches. ONC201 is an imipridone antibiotic compound with a promising drug candidate leveraging its potent anticancer properties against the mitochondrial proteases ClpP and ClpX. Despite demonstrating early clinical promise, particularly in MYCN-amplified NB, its efficacy in non-MYCN-amplified NB remains a subject worthy of investigation. In this study, we extended the coverage of ONC201 to treat non-MYCN-amplified NB, and our data implicated ONC201's inability to reduce tumor growth in animal models harboring SK-N-AS or SK-N-FI cell lines. Interestingly, ONC201 induced the expression of oncogenic markers c-Myc and LGR5 while downregulating the tumor suppressor ATRX. While it fails to attenuate tumor neovascularization in non-MYCN-amplified NB xenografts, its effectiveness differs from that of its MYCN-amplified counterpart. Rho zero (ρ0)-SK-N-AS cells treated with ONC201 showed comparable observed trends in parental SK-N-AS cells, including LGR5 upregulation and ATRX downregulation, suggesting that ONC201's multifaceted actions extend beyond mitochondrial targets. Our elucidation highlights the need to discern molecular signatures when deploying ONC201 monotherapy against NB, which lacks MYCN-amplification.

Imipridones ONC201/ONC206 + RT/TMZ triple (IRT) therapy reduces intracranial tumor burden, prolongs survival in orthotopic IDH-WT GBM mouse model, and suppresses MGMT

Glioblastoma remains a lethal brain tumor in adults with limited therapeutic options. TIC10/ONC201, a first-in-class imipridone we discovered, achieved meaningful therapeutic effects in phase I/II trials in patients with diffuse gliomas (DG's) harboring H3K27M mutations, and currently the drug is in randomized phase III testing (ACTION trial; NCT05580562). ONC201 targets mitochondrial protease ClpP to disrupt oxidative phosphorylation and trigger the integrated stress response (ISR), TRAIL/DR5, and tumor cell death. While ONC201 and its analog ONC206 are undergoing clinical trials as single agents, there is limited information on their interactions with stand-of-care therapy. We show that ONC201 and ONC206 synergize with temozolomide (TMZ) and Radiotherapy (RT). ONC201 enhances TMZ- or RT-induced apoptosis, ISR and cytotoxicity. ClpP-silencing suppresses ONC201-induced cytotoxicity but not TMZ. Both ONC201 and ONC206 reduce expression of TMZ-resistance mediator MGMT observed in H3K27M-mutated DG cells following treatment with imipridones+TMZ. Cytokine profiling indicates distinct effects of ONC201 relative to TMZ treatment. These results suggest mechanisms underlying ONC201's anti-tumoral activity are distinct from those associated with TMZ or RT with potential for synergy between these three treatments. Triple ONC201+RT+TMZ (IRT) therapy prolonged median survival to 123 days with tail on survival curve (3-of-7 mice alive beyond 200-days) in orthotopic U251 GBM model versus ONC201 (44-days; p = 0.000197), RT (63-days; p = 0.0012), TMZ (78-days; p = 0.0354), ONC201+RT (55-days; p = 0.0004), ONC201+TMZ (80-days; p = 0.0041) and RT+TMZ (103-days; p > 0.05). By 231-days, the only surviving mice were in IRT group. Our results support investigation of ONC201/ONC206 in combination with RT/TMZ (IRT) in GBM or H3K27M mutated DG therapy.

ONC201-Derived Tetrahydropyridopyrimidindiones as Powerful ClpP Protease Activators to Tackle Diffuse Midline Glioma

Pediatric diffuse intrinsic pontine glioma (DIPG), classified under diffuse midline glioma, is a deadly tumor, with no effective treatments. The human mitochondrial protease hClpP is a potential DIPG therapeutic target, and this study describes the synthesis of two new series of tetrahydropyridopyrimidindiones (THPPDs) as hClpP activators. Among the tested compounds, we have identified 36 (THX6) that shows a strong hClpP activation (EC50 = 1.18 μM) and good cytotoxicity in ONC201-resistant cells (IC50 = 0.13 μM). Studying the oxidation mechanisms on cell membranes, the treatment of DIPG cells with 36 (THX6) causes a change in levels of fatty acids (PUFAs, MUFAs, and SFAs) compared to untreated cells and dysregulates the level of proteins involved in oxidative phosphorylation, biogenesis, and mitophagy that lead to a global collapse of mitochondrial integrity and function suggesting this as the mechanism through which 36 (THX6) accomplishes its antitumor activity in DIPG cell lines.

The mitochondrial protease ClpP is a promising target for multiple myeloma treatment

Drug resistance and relapse are the major obstacles in multiple myeloma (MM) treatment, driving the search for novel therapeutics. The chemoactivation of mitochondrial caseinolytic protease P (ClpP) has shown to have anticancer effects on many tumors, but has seldom been elucidated in MM. Here we found that the CLPP expression was elevated in MM patients, and further increased in relapsed cases. After synthesizing and screening a panel of ClpP agonists, we identified a compound, 7b, as the most potent anti-MM agent in vitro. 7b activated ClpP protease activity, selectively degrading mitochondrial proteins, many of which are involved in oxidative phosphorylation (OXPHOS). As result, 7b treated MM had metabolic dysfunction, the mitochondrial membrane potential (MMP) collapse, reduced OXPHOS levels, and increased mitochondrial reactive oxygen species (ROS), leading to mitophagy-mediated MM cell death. Notably, 7b also showed efficacy against drug-resistant MM cell lines, including bortezomib- and lenalidomide-resistant cells. In vivo, 7b also exhibited remarkable anti-MM activity with tolerable side effects. In conclusion, targeting ClpP represents a promising therapeutic strategy for MM, with 7b serving as a potent anti-MM agent, especially for relapsed and refractory MM.

The Complexity of Malignant Glioma Treatment

Malignant glioma is a highly aggressive, therapeutically non-responsive, and deadly disease with a unique tumor microenvironment (TME). Of the 14 currently recognized and described cancer hallmarks, five are especially implicated in malignant glioma and targetable with repurposed drugs: cancer stem-like cells, in general, and glioma stem-like cells in particular (GSCs), vascularization and hypoxia, metabolic reprogramming, tumor-promoting inflammation and sustained proliferative signaling. Each hallmark drives malignant glioma development, both individually and through interactions with other hallmarks, in which the TME plays a critical role. To combat the aggressive malignant glioma spatio-temporal heterogeneity driven by TME interactions, and to overcome its therapeutic challenges, a combined treatment strategy including anticancer therapies, repurposed drugs and multimodal immunotherapy should be the aim for future treatment approaches.

Development of Small Molecular Hyper-activators of Human Caseinolytic Peptidase P (hClpP) with a [1,8]-naphthyridinone Scaffold as Novel Anti-cancer Agents

Based on a clinical staged small molecular hClpP activator ONC201, a class of novel hClpP agonists with a [1,8]naphthyridinone scaffold was 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.

Real life data of ONC201 (dordaviprone) in pediatric and adult H3K27-altered recurrent diffuse midline glioma: Results of an international academia-driven compassionate use program

INTRODUCTION

H3K27-altered diffuse midline gliomas (DMG) have limited therapeutic options and a very poor prognosis. Encouraging responses were observed in early clinical trials with ONC201. As ONC201 was unavailable in Europe, a compassionate use program supported by the French Authorities was launched for patients at progression after standard of care radiotherapy.

METHODS

This program was developed by the French Society of Pediatric Oncology (SFCE) and Association des Neuro-Oncologues d'Expression Française in collaboration with the French National Agency For Medicines and Health Products Safety and Parents Associations.

RESULTS

174 patients (102 children, 72 adults) from 14 countries were treated from November 2021 to August 2023 at Gustave Roussy Institut (Villejuif, France). 37 % received a second course of irradiation at the time of relapse. Median duration of treatment was 57 days or 1,9 months (mo) (range 1-456 days). Median OS since diagnosis for the whole cohort was 466 days or 15,5 mo (112-2612 days); 426 or 14,2 mo (112-2612 days) and 590 or 19,6 mo (range 160-1881) for children and adults, respectively (p = 0.001). Median OS after ONC201 start was 143 days or 4,7 mo (1-711 days) for the whole cohort. Univariate and multivariable analysis identified site (thalamus) and age (older) as favorable prognostic factors. Reirradiation was associated with significantly longer survival after ONC201 start only in children.

CONCLUSION

While the efficacy of ONC201 needs validation in a controlled randomized clinical trial, our real-life data support a better outcome for patients with thalamic tumors treated with ONC201. We demonstrated furthermore the feasibility of a successful academia-driven compassionate use program.

ONC206, an imipridone derivative, demonstrates anti-colorectal cancer activity against stem/progenitor cells in 3D cell cultures and in patient-derived organoids

BACKGROUND

Colorectal cancer (CRC) remains one of the most frequently diagnosed and life-threatening malignancies worldwide. CRC's high recurrence rates and drug resistance have been correlated with a subpopulation of dormant slowly dividing cells termed CRC stem cells (CCSCs). Consequently, there is a pressing need to identify novel therapeutics that can effectively and specifically target CCSCs. Imipridones are promising structurally related anticancer molecules that showed efficacy in several solid and hematological preclinical models and phase I/II/III clinical trials. This study mainly aimed to assess the potential anticancer effects of ONC206, an imipridone derivative, on CRC three-dimensional in vitro culture systems using HCT116 and HT29 cells. Importantly, the study aimed at using CRC patient-derived organoids (PDOs) to test the potential therapeutic effect of ONC206.

METHODS

Two-dimensional cell proliferation, viability, migration, and invasion assays were used to assess the effects of ONC206 on two colorectal cancer cell lines, HCT116 and HT29, in vitro. Immunofluorescence imaging, flow cytometry, and western blot analysis were also performed to investigate the mechanism of action of this drug. Sphere formation assay and CRC PDOs were employed to evaluate the effect of ONC206 on CRC cells in a 3D setting and specifically its potency in targeting the CRC stem/progenitor subpopulation of cells.

RESULTS

Our results showed that ONC206 was more potent than its parental molecule ONC201 in inhibiting the proliferation and viability of HCT116 and HT29 cells. Moreover, ONC206 significantly reduced the migration and invasion indices of CRC cells. These effects were accompanied by an increase in reactive oxygen species (ROS) production, sub-G1 phase accumulation, and apoptosis in HCT116 and HT29 cells. Furthermore, ONC206 significantly inhibited the 3D colonospheres growth and self-renewal ability of CCSCs more potently than ONC201, which was associated with a decrease in the expression of CSC-related markers. Lastly, ONC206 significantly reduced the growth of organoids derived from CRC patients.

CONCLUSION

Collectively, our findings demonstrate that ONC206 is an effective anticancer molecule capable of targeting CCSCs, which may represent a novel therapeutic strategy that can overcome CRC resistance and recurrence.

A Phase 1 Randomized Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of Single Escalating Oral Doses of Dordaviprone and the Effects of Food on the Bioavailability of Dordaviprone in Healthy Adult Subjects

Dordaviprone (ONC201) is a novel, small molecule imipridone with antitumor effects in glioma patients. This study evaluated the pharmacokinetics and safety of dordaviprone following single escalating doses (Part A), as a capsule content mixed with applesauce or Gatorade (sports drink) [Part B1]), and with or without food [Part B2]. The most common treatment-emergent adverse events pooled across study parts (Parts A, B1, and B2) were headache, dizziness, and headache, respectively; all were mild. Systemic dordaviprone exposure increased dose proportionally following administration of 125-625 mg of dordaviprone. Following dordaviprone capsule contents sprinkled on applesauce or dissolved in sports drink, the geometric mean ratios, and 90% confidence intervals (CIs) of the dordaviprone area under the concentration versus time curve (AUC) fell within the bioequivalence (BE) limits of 80.00%-125.00%; however, for Cmax the 90% CI lower limit (0.70) fell below BE limits when sprinkled on applesauce. The geometric mean ratios and 90% CIs of dordaviprone administered under fed versus fasted conditions fell within BE limits of 80.00%-125.00% for the AUC, indicating no food effect on total exposure; however, maximum concentration (Cmax) (90% CI 0.55, 0.67) fell below BE limits.

Small cell lung cancer and prostate cancer cells with varying neuroendocrine differentiation markers show sensitivity to imipridone ONC201/TIC10

OBJECTIVES

To investigate whether neuroendocrine differentiation (NED) markers, activation of the integrated stress response (ISR), and TRAIL pathway alter neuroendocrine tumor (NET) cell death and ONC201 sensitivity.

METHODS

We conducted cell viability assays to determine ONC201 sensitivity. Western blot analysis was performed to evaluate NED, ISR, and TRAIL pathway markers. Expression levels of NED markers were compared between cell lines with and without BRN2 overexpression.

RESULTS

Prostate cancer (PCa) and small cell lung cancer (SCLC) cell lines (N = 6) were sensitive to ONC201. Endogenous NET marker levels varied across PCa and SCLC cells. Transient BRN2 overexpression slightly reduced some NET markers while maintaining the sensitivity of PCa cells to ONC201.

CONCLUSIONS

PCa cell lines exhibit sensitivity to ONC201, with variability of NED features. These findings are relevant to the design of future studies evaluating imipridone efficacy in PCa and suggest that non-NET patients could be included in such studies.

TRAIL agonists rescue mice from radiation-induced lung, skin, or esophageal injury

Radiotherapy can be limited by pneumonitis, which is impacted by innate immunity, including pathways regulated by TRAIL death receptor DR5. We investigated whether DR5 agonists could rescue mice from toxic effects of radiation and found that 2 different agonists, parenteral PEGylated trimeric TRAIL (TLY012) and oral TRAIL-inducing compound (TIC10/ONC201), could reduce pneumonitis, alveolar wall thickness, and oxygen desaturation. Lung protection extended to late effects of radiation including less fibrosis at 22 weeks in TLY012-rescued survivors versus unrescued surviving irradiated mice. Wild-type orthotopic breast tumor-bearing mice receiving 20 Gy thoracic radiation were protected from pneumonitis with disappearance of tumors. At the molecular level, radioprotection appeared to be due to inhibition of CCL22, a macrophage-derived chemokine previously associated with radiation pneumonitis and pulmonary fibrosis. Treatment with anti-CCL22 reduced lung injury in vivo but less so than TLY012. Pneumonitis severity was worse in female versus male mice, and this was associated with increased expression of X-linked TLR7. Irradiated mice had reduced esophagitis characterized by reduced epithelial disruption and muscularis externa thickness following treatment with the ONC201 analog ONC212. The discovery that short-term treatment with TRAIL pathway agonists effectively rescues animals from pneumonitis, dermatitis, and esophagitis following high doses of thoracic radiation exposure has important translational implications.

Neuroendocrine prostate cancer drivers SOX2 and BRN2 confer differential responses to imipridones ONC201, ONC206, and ONC212 in prostate cancer cell lines

OBJECTIVES

Prostate cancer (PCa) is a leading cause of cancer death in men worldwide. Approximately 30% of castrate-resistant PCa becomes refractory to therapy due to neuroendocrine differentiation (NED) that is present in <1% of de-novo tumors. First-in-class imipridone ONC201/TIC10 therapy has shown clinical activity against midline gliomas, neuroendocrine tumors, and PCa. We explored whether NED promotes sensitivity to imipridones ONC201 and ONC206 by inducibly overexpressing SOX2 and BRN2, well-known neuroendocrine drivers.

METHODS

Inducible SOX2 or BRN2 systems were cloned into human PCa cell lines LNCaP and DU145. Inducible cell lines were characterized based on protein expression, morphology, and migration. The sensitivity of the inducible cell lines to imipridone therapy was determined by viability, cell growth, or clonogenic assays.

RESULTS

Slight protection from ONC201 or ONC206 with SOX2 and BRN2 overexpression was observed in the inducible LNCaP cells but not in the DU145 cells. At 2 months, there was an apparent increase in CLpP expression in LNCaP SOX2-overexpressing cells, though this did not confer enhanced sensitivity to ONC201. DU145 SOX2-overexpressing cells had a significantly reduced ONC201 sensitivity than DU145 control cells.

CONCLUSIONS

The results suggest that treatment of castrate-resistant prostate cancer by imipridones may not be substantially affected 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.

Development of Novel Imipridones with Alkyne- and Triazole-Linked Warheads on the Tricyclic Skeleton, Showing Superior Ability to Eradicate PANC-1 and Fadu Cells Compared to ONC201

Our ongoing research focuses on the development of new imipridone derivatives. We aim to design compounds that can completely and selectively eradicate cancer cells after relatively short treatment. We have synthetized systematically designed novel hybrids and evaluated their antiproliferative activity against PANC-1 and Fadu cell lines. We have also conducted preliminary studies on the mechanism, including colony formation as well as dose-response tests in HEK293T wild-type (WT) and HEK293T CLPP-/- cells. Following gradual structural fine-tuning based on high throughput screening, we identified two imipridone hybrids as the most potent derivatives. Their unique substitution pattern includes N-methylated propargylamine and ferrocenyl/phenyltriazole moieties on the benzyl groups attached to opposite sides of the imipridone core. We found that the compounds with IC50 values similar to those of ONC201 completely eradicated cancer cells at about 4 μM, while ONC201 treatment at even higher concentrations left 30-50% of viable cells behind. Both compounds exerted equal activity in WT and CLPP-/- HEK293T cells, indicating a ClpP-independent mechanism. Further development is needed to improve the tumor selectivity of the two potent imipridone derivatives. By preserving tumor cytotoxicity, we aim to generate new drug candidates that evade resistance and can be applied in a sufficiently broad therapeutic window.

Development of novel imipridone derivatives with potent anti-cancer activities as human caseinolytic peptidase P (hClpP) activators

Based on a clinically staged small molecular hClpP activator ONC201, a class of imipridone derivatives was designed and synthesized. These compounds were evaluated in a protease hydrolytic assay, as well as cell growth inhibition assays in three cancer cell lines, MIA PACA-2, HCT116, and MV4-11. A number of compounds that can more potently activate hClpP and more effectively inhibit cell growth in the three cancer cell lines than ONC201 were identified. The most potent compound, ZYZ-17, activated hClpP with an EC50 value of 0.24 µM and inhibited the growth of the three cancer cell lines with IC50 values of less than 10 nM. Mechanism studies for ZYZ-17 revealed that it potently activates cellular hClpP, efficiently induces the degradation of hClpP substrates, and robustly induces apoptosis in the three cancer cell lines. Furthermore, ZYZ-17 demonstrated a promising pharmacokinetic (PK) profile and exhibited highly potent in vivo antitumor activity in a pancreatic cancer MIA PACA-2 xenograft model in BALB/c nude mice.

Imipridones inhibit tumor growth and improve survival in an orthotopic liver metastasis mouse model of human uveal melanoma

BACKGROUND

Uveal melanoma (UM) is a highly aggressive disease with very few treatment options. We previously demonstrated that mUM is characterized by high oxidative phosphorylation (OXPHOS). Here we tested the anti-tumor, signaling and metabolic effects of imipridones, which are CLPP activators, which inhibit OXPHOS indirectly and have demonstrated safety in patients.

METHODS

We assessed CLPP expression in UM patient samples. We tested the effects of imipridones (ONC201 and ONC212) on the growth, survival, signaling and metabolism of UM cell lines in vitro, and for therapeutic efficacy in vivo in UM liver metastasis models.

RESULTS

CLPP expression was detected in primary and mUM patient samples. ONC201 and 212 decreased OXPHOS effectors, inhibited cell growth and migration, and induced apoptosis in human UM cell lines in vitro. ONC212 inhibited OXPHOS, increased metabolic stress and apoptotic pathways, inhibited amino acid metabolism, and induced cell death-related lipids. ONC212 also decreased tumor burden and increased survival in vivo in two UM liver metastasis models.

CONCLUSIONS

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

Targeting Mitochondria in Glioma: New Hopes for a Cure

Drugs targeting mitochondrial energy metabolism are emerging as promising antitumor therapeutics. Glioma treatment is extremely challenging due to the high complexity of the tumor and the high cellular heterogeneity. From a metabolic perspective, glioma cancer cells can be classified into the oxidative metabolic phenotype (mainly depending on mitochondrial respiration for energy production) and glycolytic phenotype or "Warburg effect" (mainly depending on glycolysis). Herein, we reviewed the function of novel bio-active molecules targeting oxidative phosphorylation (OXPHOS), mitochondrial membrane potential and mitochondrial dynamics. These molecules exhibit intriguing preclinical and clinical results and have been proven to be promising candidates to be further developed for glioma therapy. However, despite these initial encouraging results, it is imperative to rigorously assess the side effects of these metabolic drugs, which have a non-negligible toxicity profile.

Nitrogen-Nitrogen Radical Coupling-Enabled Precise Difunctionalization of Carbon-Nitrogen Double Bonds

In this study, we have developed a metal-free, photoinduced energy transfer strategy for the efficient difunctionalization of carbon-nitrogen double bonds (C═N). Utilizing oxime ester-based bifunctional reagents, we have achieved direct radical difunctionalization of C═N bonds through nitrogen-nitrogen radical coupling, with over 35 examples and yields up to 96%. This method exhibits broad substrate scope, being compatible with a variety of carboxylic acids and biologically active molecules, thus offering a novel approach for the difunctionalization of heteroatom-containing unsaturated bonds in synthetic chemistry.

Discovery of Dehydrogenated Imipridone Derivatives as Activators of Human Caseinolytic Protease P

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. Mechanism studies for one of the most potent compounds, XT6, indicated that it can potently bind to both recombinant and cellular hClpP, effectively promote the formation of hClpP tetradecamer, efficiently induce the degradation of hClpP substrates, robustly upregulate the expression of ATF4, and strongly inhibit the phosphorylations of AKT and ERK. 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.

ONC206 targeting ClpP induces mitochondrial dysfunction and protective autophagy in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common form of liver cancer, accounting for approximately 90 % of all cases. ONC201, a member of the imipridone drug family, has shown promising therapeutic potential and a good safety profile in both malignant pediatric central nervous system tumors (diffuse midline glioma [DMG]) and hematologic malignancies. ONC206 is a more potent analog of ONC201. However, the ONC206 potential and mechanism of action in HCC remain to be elucidated. We found that ONC206 hindered HCC growth by suppressing cell proliferation and inducing apoptosis. Moreover, ONC206 induced cytoprotective autophagy, and blocking autophagy enhanced the proapoptotic effect of ONC206. Additionally, ONC206 induced mitochondrial swelling, reduced the mitochondrial membrane potential (MMP), and led to the accumulation of mitochondrial ROS in HCC cells, ultimately resulting in mitochondrial dysfunction. The HCC patient samples exhibited notably elevated levels of caseinolytic protease proteolytic subunit (ClpP), which serves as a mediator of ONC206-induced mitochondrial dysfunction and the activation of protective autophagy. knockdown of ClpP reversed the cytotoxic effects of ONC206 on HCC cells. In summary, our results provide the first insight into the mechanism by which ONC206 exerts its anti-HCC effects and induces protective autophagy in HCC cells through ClpP.

Overview of BH3 mimetics in ovarian cancer

Ovarian carcinoma is the leading cause of gynecological cancer-related death, still with a dismal five-year prognosis, mainly due to late diagnosis and the emergence of resistance to cytotoxic and targeted agents. Bcl-2 family proteins have a key role in apoptosis and are associated with tumor development/progression and response to therapy in different cancer types, including ovarian carcinoma. In tumors, evasion of apoptosis is a possible mechanism of resistance to therapy. BH3 mimetics are small molecules that occupy the hydrophobic pocket on pro-survival proteins, allowing the induction of apoptosis, and are currently under study as single agents and/or in combination with cytotoxic and targeted agents in solid tumors. Here, we discuss recent advances in targeting anti-apoptotic proteins of the Bcl-2 family for the treatment of ovarian cancer, focusing on BH3 mimetics, and how these approaches could potentially offer an alternative/complementary way to treat patients and overcome or delay resistance to current treatments.

Neuroendocrine differentiation (ND) in sensitivity of neuroendocrine tumor (NET) cells to ONC201/TIC10 cancer therapeutic

Prostate cancer (PCa) neuroendocrine tumor (NET)-like cells with low or absent androgen receptor (AR) signaling cause hormone therapy resistance and poor prognosis. Small cell lung carcinoma (SCLC), a high-grade NET, presents with metastasis early and has poor survival. ONC201/TIC10 is a first-in-class cancer therapeutic with clinical activity in diffuse gliomas and neuroendocrine tumors. We hypothesized that markers of neuroendocrine differentiation, activation of the integrated stress response (ISR) and the TRAIL pathway, as well as the expression of ClpP, contribute to neuroendocrine tumor cell death and sensitivity to ONC201. We show that PCa and SCLC cell lines (N=6) are sensitive to ONC201, regardless of the extent of neuroendocrine differentiation. Endogenous levels of some NET markers (CgA, FoxO1, ENO2, PGP9.5, SOX2) are present in a spectrum in PCa and SCLC cell lines. Overexpression of neural transcription factor BRN2 in DU145 PCa cells does not increase expression of NET differentiation markers FoxO1, ENO2, PGP9.5, and CgA at 48 hours. However, the transient BRN2 overexpression showed slight decreases in some NET markers on the spectrum while maintaining sensitivity of PCa cells to ONC201 before any phenotypic change related to NET differentiation. Our results show that ONC201 has preclinical activity against PCa including those without NET markers or in PCa cells with transient overexpression of neural transcription factor BRN2. 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.

Neuroendocrine Prostate Cancer Drivers SOX2 and BRN2 Confer Differential Responses to Imipridones ONC201, ONC206, and ONC212 in Prostate Cancer Cell Lines

Prostate cancer (PCa) is the leading cause death from cancer in men worldwide. Approximately 30% of castrate-resistant PCa's become refractory to therapy due to neuroendocrine differentiation (NED) that is present in <1% of androgen-sensitive tumors. First-in-class imipridone ONC201/TIC10 has shown clinical activity against midline gliomas, neuroendocrine tumors and PCa. We explored the question of whether NED promotes sensitivity to imipridones ONC201 and ONC206 by inducible overexpression of SOX2 and BRN2, well-known neuroendocrine drivers, in human PCa cell lines DU145 or LNCaP. Slight protection from ONC201 or ONC206 with SOX2 and BRN2 overexpression was observed in the inducible LNCaP cells but not in the DU145 cells. At 2 months, there was an apparent increase in CLpP expression in LNCaP SOX2-overexpressing cells but this did not confer enhanced sensitivity to ONC201. DU145 SOX2-overexpressing cells had a significantly reduced ONC201 sensitivity than DU145 control cells. 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.

Chemical synthetic approaches to mimic the TRAIL: promising cancer therapeutics

Apoptosis is programmed cell death that eliminates undesired cells to maintain homeostasis in metazoan. Aberration of this process may lead to cancer genesis. The tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces apoptosis in cancer cells after ligation with death receptors (DR4/DR5) while sparing most normal cells. Therefore, strategies to induce apoptosis in cancer cells by mimicking the TRAIL emerge as a promising therapeutic tool. Hence, approaches are taken to develop TRAIL/DR-based cancer therapeutics. The recombinant soluble TRAIL (rhTRAIL) and death receptor agonistic antibodies were produced and tested pre-clinically and clinically. Pre-clinical and clinical trial data demonstrate that these therapeutics are safe and relatively well tolerated. But some of these therapeutics failed to exert adequate efficacy in clinical settings. Besides these biotechnologically derived therapeutics, a few chemically synthesized therapeutics are reported. Some of these therapeutics exert considerable efficacy in vitro and in vivo. In this review, we will discuss chemically synthesized TRAIL/DR-based therapeutics, their chemical and biological behaviour, design concepts and strategies that may contribute to further improvement of TRAIL/DR-based therapeutics.

Targeting apoptotic pathways for cancer therapy

Apoptosis is a form of programmed cell death that is mediated by intrinsic and extrinsic pathways. Dysregulation of and resistance to cell death are hallmarks of cancer. For over three decades, the development of therapies to promote treatment of cancer by inducing various cell death modalities, including apoptosis, has been a main goal of clinical oncology. Apoptosis pathways also interact with other signaling mechanisms, such as the p53 signaling pathway and the integrated stress response (ISR) pathway. In addition to agents directly targeting the intrinsic and extrinsic pathway components, anticancer drugs that target the p53 and ISR signaling pathways are actively being developed. In this Review, we discuss selected and promising anticancer therapies in various stages of development, including drug targets, mechanisms, and resistance to related treatments, focusing especially on B cell lymphoma 2 (BCL-2) inhibitors, TRAIL analogues, DR5 antibodies, and strategies that target p53, mutant p53, and the ISR.

GABA production induced by imipridones is a targetable and imageable metabolic alteration in diffuse midline gliomas

Diffuse midline gliomas (DMGs) are lethal primary brain tumors in children. The imipridones ONC201 and ONC206 induce mitochondrial dysfunction and have emerged as promising therapies for DMG patients. However, efficacy as monotherapy is limited, identifying a need for strategies that enhance response. Another hurdle is the lack of biomarkers that report on drug-target engagement at an early timepoint after treatment onset. Here, using 1 H-magnetic resonance spectroscopy, which is a non-invasive method of quantifying metabolite pool sizes, we show that accumulation of ψ-aminobutyric acid (GABA) is an early metabolic biomarker that can be detected within a week of ONC206 treatment, when anatomical alterations are absent, in mice bearing orthotopic xenografts. Mechanistically, imipridones activate the mitochondrial protease ClpP and upregulate the stress-responsive transcription factor ATF4. ATF4, in turn, upregulates glutamate decarboxylase, which synthesizes GABA, and downregulates ABAT , which degrades GABA, leading to GABA accumulation in DMG cells and tumors. Functionally, GABA secreted by imipridone-treated cells acts in an autocrine manner via the GABAB receptor to induce expression of superoxide dismutase (SOD1), which mitigates imipridone-induced oxidative stress and, thereby, curbs apoptosis. Importantly, blocking autocrine GABA signaling using the clinical stage GABAB receptor antagonist SGS-742 exacerbates oxidative stress and synergistically induces apoptosis in combination with imipridones in DMG cells and orthotopic tumor xenografts. Collectively, we identify GABA as a unique metabolic adaptation to imipridones that can be leveraged for non-invasive assessment of drug-target engagement and therapy. Clinical translation of our studies has the potential to enable precision metabolic therapy and imaging for DMG patients.

One Sentence Summary

Imipridones induce GABA accumulation in diffuse midline gliomas, an effect that can be leveraged for therapy and non-invasive imaging.

Advances in synthetic lethality modalities for glioblastoma multiforme

Glioblastoma multiforme (GBM) is characterized by a high mortality rate, high resistance to cytotoxic chemotherapy, and radiotherapy due to its highly aggressive nature. The pathophysiology of GBM is characterized by multifarious genetic abrasions that deactivate tumor suppressor genes, induce transforming genes, and over-secretion of pro-survival genes, resulting in oncogene sustainability. Synthetic lethality is a destructive process in which the episode of a single genetic consequence is tolerable for cell survival, while co-episodes of multiple genetic consequences lead to cell death. This targeted drug approach, centered on the genetic concept of synthetic lethality, is often selective for DNA repair-deficient GBM cells with restricted toxicity to normal tissues. DNA repair pathways are key modalities in the generation, treatment, and drug resistance of cancers, as DNA damage plays a dual role as a creator of oncogenic mutations and a facilitator of cytotoxic genomic instability. Although several research advances have been made in synthetic lethality modalities for GBM therapy, no review article has summarized these therapeutic modalities. Thus, this review focuses on the innovative advances in synthetic lethality modalities for GBM therapy.

ONC212 enhances YM155 cytotoxicity by triggering SLC35F2 expression and NOXA-dependent MCL1 degradation in acute myeloid leukemia cells

Although the anticancer activity of ONC212 has been reported, the precise mechanism underlying its apoptotic effects remains unclear. In this study, we investigated the apoptotic mechanism of ONC212 in acute myeloid leukemia (AML) cells. ONC212 induces apoptosis, MCL1 downregulation, and mitochondrial depolarization in AML U937 cells. Ectopic MCL1 expression alleviates mitochondria-mediated apoptosis in ONC212-treated U937 cells. ONC212 triggers AKT phosphorylation, inducing NOX4-dependent ROS production and promoting HuR transcription. HuR-mediated ATF4 mRNA stabilization stimulates NOXA and SLC35F2 expression; ONC212-induced upregulation of NOXA leads to MCL1 degradation. The synergistic effect of ONC212 on YM155 cytotoxicity was dependent on increased SLC35F2 expression. In addition, YM155 feedback facilitated the activation of the ONC212-induced signaling pathway. A similar mechanism explains ONC212- and ONC212/YM155-induced AML HL-60 cell death. 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. In U937/HQ cells, ONC212 triggered apoptosis through NOXA-mediated MCL1 downregulation, enhancing YM155 cytotoxicity. 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.

Mammalian integrated stress responses in stressed organelles and their functions

The integrated stress response (ISR) triggered in response to various cellular stress enables mammalian cells to effectively cope with diverse stressful conditions while maintaining their normal functions. Four kinases (PERK, PKR, GCN2, and HRI) of ISR regulate ISR signaling and intracellular protein translation via mediating the phosphorylation of eukaryotic translation initiation factor 2 α (eIF2α) at Ser51. Early ISR creates an opportunity for cells to repair themselves and restore homeostasis. This effect, however, is reversed in the late stages of ISR. Currently, some studies have shown the non-negligible impact of ISR on diseases such as ischemic diseases, cognitive impairment, metabolic syndrome, cancer, vanishing white matter, etc. Hence, artificial regulation of ISR and its signaling with ISR modulators becomes a promising therapeutic strategy for relieving disease symptoms and improving clinical outcomes. Here, we provide an overview of the essential mechanisms of ISR and describe the ISR-related pathways in organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Meanwhile, the regulatory effects of ISR modulators and their potential application in various diseases are also enumerated.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

Knockout Mouse Studies Show That Mitochondrial CLPP Peptidase and CLPX Unfoldase Act in Matrix Condensates near IMM, as Fast Stress Response in Protein Assemblies for Transcript Processing, Translation, and Heme Production

LONP1 is the principal AAA+ unfoldase and bulk protease in the mitochondrial matrix, so its deletion causes embryonic lethality. The AAA+ unfoldase CLPX and the peptidase CLPP also act in the matrix, especially during stress periods, but their substrates are poorly defined. Mammalian CLPP deletion triggers infertility, deafness, growth retardation, and cGAS-STING-activated cytosolic innate immunity. CLPX mutations impair heme biosynthesis and heavy metal homeostasis. CLPP and CLPX are conserved from bacteria to humans, despite their secondary role in proteolysis. Based on recent proteomic-metabolomic evidence from knockout mice and patient cells, we propose that CLPP acts on phase-separated ribonucleoprotein granules and CLPX on multi-enzyme condensates as first-aid systems near the inner mitochondrial membrane. Trimming within assemblies, CLPP rescues stalled processes in mitoribosomes, mitochondrial RNA granules and nucleoids, and the D-foci-mediated degradation of toxic double-stranded mtRNA/mtDNA. Unfolding multi-enzyme condensates, CLPX maximizes PLP-dependent delta-transamination and rescues malformed nascent peptides. Overall, their actions occur in granules with multivalent or hydrophobic interactions, separated from the aqueous phase. Thus, the role of CLPXP in the matrix is compartment-selective, as other mitochondrial peptidases: MPPs at precursor import pores, m-AAA and i-AAA at either IMM face, PARL within the IMM, and OMA1/HTRA2 in the intermembrane space.

ACTION: a randomized phase 3 study of ONC201 (dordaviprone) in patients with newly diagnosed H3 K27M-mutant diffuse glioma

BACKGROUND

H3 K27M-mutant diffuse glioma primarily affects children and young adults, is associated with a poor prognosis, and no effective systemic therapy is currently available. ONC201 (dordaviprone) has previously demonstrated efficacy in patients with recurrent disease. This phase 3 trial evaluates ONC201 in patients with newly diagnosed H3 K27M-mutant glioma.

METHODS

ACTION (NCT05580562) is a randomized, double-blind, placebo-controlled, parallel-group, international phase 3 study of ONC201 in newly diagnosed H3 K27M-mutant diffuse glioma. Patients who have completed standard frontline radiotherapy are randomized 1:1:1 to receive placebo, once-weekly dordaviprone, or twice-weekly dordaviprone on 2 consecutive days. Primary efficacy endpoints are overall survival (OS) and progression-free survival (PFS); PFS is assessed by response assessment in neuro-oncology high-grade glioma criteria (RANO-HGG) by blind independent central review. Secondary objectives include safety, additional efficacy endpoints, clinical benefit, and quality of life. Eligible patients have histologically confirmed H3 K27M-mutant diffuse glioma, a Karnofsky/Lansky performance status ≥70, and completed first-line radiotherapy. Eligibility is not restricted by age; however, patients must be ≥10 kg at time of randomization. Patients with a primary spinal tumor, diffuse intrinsic pontine glioma, leptomeningeal disease, or cerebrospinal fluid dissemination are not eligible. ACTION is currently enrolling in multiple international sites.

A review of current therapeutics targeting the mitochondrial protease ClpP in diffuse midline glioma, H3 K27-altered

Diffuse midline gliomas (DMGs) are devastating pediatric brain tumors recognized as the leading cause of cancer-related death in children. DMGs are high-grade gliomas (HGGs) diagnosed along the brain's midline. Euchromatin is the hallmark feature of DMG, caused by global hypomethylation of H3K27 either through point mutations in histone H3 genes (H3K27M), or by overexpression of the enhancer of zeste homolog inhibitory protein. In a clinical trial for adults with progressive HGGs, a 22-year-old patient with a thalamic DMG, H3 K27-altered, showed a remarkable clinical and radiological response to dordaviprone (ONC201). This response in an H3 K27-altered HGG patient, coupled with the lack of response of patients harboring wildtype-H3 tumors, has increased the clinical interest in dordaviprone for the treatment of DMG. Additional reports of clinical benefit have emerged, but research defining mechanisms of action (MOA) fall behind dordaviprone's clinical use, with biomarkers of response unresolved. Here, we summarize dordaviprone's safety, interrogate its preclinical MOA identifying the mitochondrial protease "ClpP" as a biomarker of response, and discuss other ClpP agonists, expanding the arsenal of potential weapons in the fight against DMG. Finally, we discuss combination strategies including ClpP agonists, and their immunomodulatory effects suggestive of a role for the tumor microenvironment in DMG patient response.

Rational combination platform trial design for children and young adults with diffuse midline glioma: A report from PNOC

Background Diffuse midline glioma (DMG) is a devastating pediatric brain tumor unresponsive to hundreds of clinical trials. Approximately 80% of DMGs harbor H3K27M oncohistones, which reprogram the epigenome to increase the metabolic profile of the tumor cells. Methods We have previously shown preclinical efficacy of targeting both oxidative phosphorylation and glycolysis through treatment with ONC201, which activates the mitochondrial protease ClpP, and paxalisib, which inhibits PI3K/mTOR, respectively. Results ONC201 and paxalisib combination treatment aimed at inducing metabolic distress led to the design of the first DMG-specific platform trial PNOC022 (NCT05009992). Conclusions Here, we expand on the PNOC022 rationale and discuss various considerations, including liquid biome, microbiome, and genomic biomarkers, quality-of-life endpoints, and novel imaging modalities, such that we offer direction on future clinical trials in DMG.

Comprehensive review of Bcl-2 family proteins in cancer apoptosis: Therapeutic strategies and promising updates of natural bioactive compounds and small molecules

Cancer has a considerably higher fatality rate than other diseases globally and is one of the most lethal and profoundly disruptive ailments. The increasing incidence of cancer among humans is one of the greatest challenges in the field of healthcare. A significant factor in the initiation and progression of tumorigenesis is the dysregulation of physiological processes governing cell death, which results in the survival of cancerous cells. B-cell lymphoma 2 (Bcl-2) family members play important roles in several cancer-related processes. Drug research and development have identified various promising natural compounds that demonstrate potent anticancer effects by specifically targeting Bcl-2 family proteins and their associated signaling pathways. This comprehensive review highlights the substantial roles of Bcl-2 family proteins in regulating apoptosis, including the intricate signaling pathways governing the activity of these proteins, the impact of reactive oxygen species, and the crucial involvement of proteasome degradation and the stress response. Furthermore, this review discusses advances in the exploration and potential therapeutic applications of natural compounds and small molecules targeting Bcl-2 family proteins and thus provides substantial scientific information and therapeutic strategies for cancer management.

ONC201 (Dordaviprone) in Recurrent H3 K27M-Mutant Diffuse Midline Glioma

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

ONC201 monotherapy was well tolerated and exhibited durable and clinically meaningful efficacy in recurrent H3 K27M-mutant DMG.

The Imipridone ONC213 Targets α-Ketoglutarate Dehydrogenase to Induce Mitochondrial Stress and Suppress Oxidative Phosphorylation in Acute Myeloid Leukemia

Eradication of acute myeloid leukemia (AML) is therapeutically challenging; many patients succumb to AML despite initially responding to conventional treatments. Here, we showed that the imipridone ONC213 elicits potent antileukemia activity in a subset of AML cell lines and primary patient samples, particularly in leukemia stem cells, while producing negligible toxicity in normal hematopoietic cells. ONC213 suppressed mitochondrial respiration and elevated α-ketoglutarate by suppressing α-ketoglutarate dehydrogenase (αKGDH) activity. Deletion of OGDH, which encodes αKGDH, suppressed AML fitness and impaired oxidative phosphorylation, highlighting the key role for αKGDH inhibition in ONC213-induced death. ONC213 treatment induced a unique mitochondrial stress response and suppressed de novo protein synthesis in AML cells. Additionally, ONC213 reduced the translation of MCL1, which contributed to ONC213-induced apoptosis. Importantly, a patient-derived xenograft from a relapsed AML patient was sensitive to ONC213 in vivo. Collectively, these findings support further development of ONC213 for treating AML.

SIGNIFICANCE

In AML cells, ONC213 suppresses αKGDH, which induces a unique mitochondrial stress response, and reduces MCL1 to decrease oxidative phosphorylation and elicit potent antileukemia activity. See related commentary by Boët and Sarry, p. 950.

Discovery of a Novel Series of Homo sapiens Caseinolytic Protease P Agonists for Colorectal Adenocarcinoma Treatment via ATF3-Dependent Integrated Stress Response

Homo sapiens caseinolytic protease P (HsClpP) activation is a promising strategy for colon cancer treatment. In this study, CCG1423 was identified as a selective activator of HsClpP. After optimization, NCA029 emerged as the most potent compound, with an EC50 of 0.2 μM against HsClpP. Molecular dynamics revealed that the affinity of NCA029 for the YYW aromatic network is crucial for its selectivity toward HsClpP. Furthermore, NCA029 displayed favorable pharmacokinetics and safety profiles and significantly inhibited tumor growth in HCT116 xenografts, resulting in 83.6% tumor inhibition. Mechanistically, NCA029 targeted HsClpP, inducing mitochondrial dysfunction and activating the ATF3-dependent integrated stress response, ultimately causing cell death in colorectal adenocarcinoma. These findings highlight NCA029 as an effective HsClpP activator with potential for colon cancer therapy.

CLPP-Null Eukaryotes with Excess Heme Biosynthesis Show Reduced L-arginine Levels, Probably via CLPX-Mediated OAT Activation

The serine peptidase CLPP is conserved among bacteria, chloroplasts, and mitochondria. In humans and mice, its loss causes Perrault syndrome, which presents with growth deficits, infertility, deafness, and ataxia. In the filamentous fungus Podospora anserina, CLPP loss leads to longevity. CLPP substrates are selected by CLPX, an AAA+ unfoldase. CLPX is known to target delta-aminolevulinic acid synthase (ALAS) to promote pyridoxal phosphate (PLP) binding. CLPX may also influence cofactor association with other enzymes. Here, the evaluation of P. anserina metabolomics highlighted a reduction in arginine/histidine levels. In Mus musculus cerebellum, reductions in arginine/histidine and citrulline occurred with a concomitant accumulation of the heme precursor protoporphyrin IX. This suggests that the increased biosynthesis of 5-carbon (C5) chain deltaALA consumes not only C4 succinyl-CoA and C1 glycine but also specific C5 delta amino acids. As enzymes responsible for these effects, the elevated abundance of CLPX and ALAS is paralleled by increased OAT (PLP-dependent, ornithine delta-aminotransferase) levels. Possibly as a consequence of altered C1 metabolism, the proteome profiles of P. anserina CLPP-null cells showed strong accumulation of a methyltransferase and two mitoribosomal large subunit factors. The reduced histidine levels may explain the previously observed metal interaction problems. As the main nitrogen-storing metabolite, a deficiency in arginine would affect the urea cycle and polyamine synthesis. Supplementation of arginine and histidine might rescue the growth deficits of CLPP-mutant patients.

New progress in the treatment of diffuse midline glioma with H3K27M alteration

Diffuse midline glioma with H3K27 M alteration is a primary malignant tumor located along the linear structure of the brain, predominantly manifesting in children and adolescents. The mortality rate is exceptionally high, with a mere 1 % 5-year survival rate for newly diagnosed patients. Beyond conventional surgery, radiotherapy, and chemotherapy, novel approaches are imperative to enhance patient prognosis. This article comprehensively reviews current innovative treatment modalities and provides updates on the latest research advancements in preclinical studies and clinical trials focusing on H3K27M-altered diffuse midline glioma. The goal is to contribute positively to clinical treatment strategies.

TR-57 Treatment of SUM159 Cells Induces Mitochondrial Dysfunction without Affecting Membrane Potential

Recent works identified ClpXP, mitochondrial caseinolytic protease, as the only target of imipridones, a new class of antitumor agents. Our study of the mechanism of imipridone derivative TR-57 action in SUM159 human breast cancer cells demonstrated mitochondrial fragmentation, degradation of mitochondrial mtDNA and mitochondrial dysfunction due to inhibition of Complex I and Complex II activity. Complete inhibition of oxidative phosphorylation accompanied 90, 94, 88 and 87% decreases in the content of Complex I, II, III and IV proteins, respectively. The content of the FOF1-ATPase subunits decreased sharply by approximately 35% after 24 h and remained unchanged up to 72 h of incubation with TR-57. At the same time, a disappearance of the ATPIF1, the natural inhibitor of mitochondrial FOF1-ATPase, was observed after 24 h exposure to TR-57. ATPase inhibitor oligomycin did not affect the mitochondrial membrane potential in intact SUM159, whereas it caused a 65% decrease in TR-57-treated cells. SUM159 cells incubated with TR57 up to 72 h retained the level of proteins facilitating the ATP transfer across the mitochondrial membranes: VDAC1 expression was not affected, while expression of ANT-1/2 and APC2 increased by 20% and 40%, respectively. Thus, our results suggest that although TR-57 treatment leads to complete inhibition of respiratory chain activity of SUM159 cells, hydrolysis of cytoplasmic ATP by reversal activity of FOF1-ATPase supports mitochondrial polarization.

Imipridones inhibit tumor growth and improve survival in an orthotopic liver metastasis mouse model of human uveal melanoma

Purpose

Uveal melanoma (UM) is a highly aggressive disease with very few treatment options. We previously demonstrated that mUM is characterized by high oxidative phosphorylation (OXPHOS). Here we tested the anti-tumor, signaling and metabolic effects of imipridones, CLPP activators which reduce OXPHOS indirectly and have demonstrated safety in patients.

Experimental Design

We assessed CLPP expression in UM patient samples. We tested the effects of imipridones (ONC201, ONC212) on the growth, survival, signaling and metabolism of UM cell lines in vitro, and for therapeutic effects in vivo in UM liver metastasis models.

Results

CLPP expression was confirmed in primary and mUM patient samples. ONC201/212 treatment of UM cell lines in vitro decreased OXPHOS effectors, inhibited cell growth and migration, and induced apoptosis. ONC212 increased metabolic stress and apoptotic pathways, inhibited amino acid metabolism, and induced cell death-related lipids. ONC212 also decreased tumor burden and increased survival in vivo in two UM liver metastasis models.

Conclusion

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

A novel dopamine receptor D2 antagonist (ONC206) potentiates the effects of olaparib in endometrial cancer

Poly ADP-ribose polymerase (PARP) inhibitors are effective therapies for cancer patients with homologous recombination (HR) deficient tumors. The imipridone ONC206 is an orally bioavailable dopamine receptor D2 antagonist and mitochondrial protease ClpP agonist that has anti-tumorigenic effects in endometrial cancer via induction of apoptosis, activation of the integrated stress response and modulation of PI3K/AKT signaling. Both PARP inhibitors and imipridones are being evaluated in endometrial cancer clinical trials but have yet to be explored in combination. In this manuscript, we evaluated the effects of the PARP inhibitor olaparib in combination with ONC206 in human endometrioid endometrial cancer cell lines and in a genetically engineered mouse model of endometrial cancer. Our results showed that simultaneous exposure of endometrial cancer cells to olaparib and ONC206 resulted in synergistic anti-proliferative effects and increased cellular stress and apoptosis in both cell lines, compared to either drug alone. The combination treatment also decreased expression of the anti-apoptotic protein Bcl-2 and reduced phosphorylation of AKT and S6, with greater effects compared to either drug alone. 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.

Novel combination of imipridones and histone deacetylase inhibitors demonstrate cytotoxic effect through integrated stress response in pediatric solid tumors

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.

ONC201/TIC10 plus TLY012 anti-cancer effects via apoptosis inhibitor downregulation, stimulation of integrated stress response and death receptor DR5 in gastric adenocarcinoma

Gastric adenocarcinoma typically presents with advanced stage when inoperable. Chemotherapy options include non-targeted and toxic agents, leading to poor 5-year patient survival outcomes. Small molecule ONC201/TIC10 (TRAIL-Inducing Compound #10) induces cancer cell death via ClpP-dependent activation of the integrated stress response (ISR) and up-regulation of the TRAIL pathway. We previously found in breast cancer, pancreatic cancer and endometrial cancer that ONC201 primes tumor cells for TRAIL-mediated cell death through ISR-dependent upregulation of ATF4, CHOP and TRAIL death receptor DR5. We investigated the ability of ONC201 to induce apoptosis in gastric adenocarcinoma cells in combination with recombinant human TRAIL (rhTRAIL) or PEGylated trimeric TRAIL (TLY012). AGS (caspase 8-, KRAS-, PIK3CA-mutant, HER2-amplified), SNU-1 (KRAS-, MLH1-mutant, microsatellite unstable), SNU-5 (p53-mutant) and SNU-16 (p53-mutant) gastric adenocarcinoma cells were treated with ONC201 and TRAIL both in cell culture and in vivo. Gastric cancer cells showed synergy following dual therapy with ONC201 and rhTRAIL/TLY012 (combination indices < 0.6 at doses that were non-toxic towards normal fibroblasts). Synergy was observed with increased cells in the sub-G1 phase of the cell cycle with dual ONC201 plus TRAIL therapy. Increased PARP, caspase 8 and caspase 3 cleavage after ONC201 plus TRAIL further documented apoptosis. Increased cell surface expression of DR5 with ONC201 therapy was observed by flow cytometry, and immunoblotting revealed ONC201 upregulation of the ISR, ATF4, and CHOP. We observed downregulation of anti-apoptotic cIAP-1 and XIAP in all cells except AGS, and cFLIP in all cells except SNU-16. We tested the regimen in an organoid model of human gastric cancer, and in murine sub-cutaneous xenografts using AGS and SNU-1 cells. Our results suggest that ONC201 in combination with TRAIL may be an effective and non-toxic option for the treatment of gastric adenocarcinoma by inducing apoptosis via activation of the ISR, increased cell surface expression of DR5 and down-regulation of inhibitors of apoptosis. Our results demonstrate in vivo anti-tumor effects of ONC201 plus TLY012 against gastric cancer that could be further investigated in clinical trials.

The adaptor protein 14-3-3zeta modulates intestinal immunity and aging in Drosophila

The proteins that coordinate the complex transcriptional networks of aging have not been completely documented. Protein 14-3-3zeta is an adaptor protein that coordinates signaling and transcription factor networks, but its function in aging is not fully understood. Here, we showed that the protein expression of 14-3-3zeta gradually increased during aging. High levels of 14-3-3zeta led to shortened lifespan and imbalance of intestinal immune homeostasis in Drosophila, but the decrease in 14-3-3zeta protein levels by RNAi was able to significantly promote the longevity and intestinal immune homeostasis of fruit flies. Importantly, we demonstrate that adult-onset administration of TIC10, a compound that reduces the aging-related AKT and extracellular signal-regulated kinase (ERK) signaling pathways, rescues the shortened lifespan of 14-3-3zeta-overexpressing flies. This finding suggests that 14-3-3zeta plays a critical role in regulating the aging process. Our study elucidates the role of 14-3-3zeta in natural aging and provides the rationale for subsequent 14-3-3zeta-based antiaging research.

Selective activator of human ClpP triggers cell cycle arrest to inhibit lung squamous cell carcinoma

Chemo-activation of mitochondrial ClpP exhibits promising anticancer properties. However, we are currently unaware of any studies using selective and potent ClpP activators in lung squamous cell carcinoma. In this work, we report on such an activator, ZK53, which exhibits therapeutic effects on lung squamous cell carcinoma in vivo. The crystal structure of ZK53/ClpP complex reveals a π-π stacking effect that is essential for ligand binding selectively to the mitochondrial ClpP. ZK53 features on a simple scaffold, which is distinct from the activators with rigid scaffolds, such as acyldepsipeptides and imipridones. ZK53 treatment causes a decrease of the electron transport chain in a ClpP-dependent manner, which results in declined oxidative phosphorylation and ATP production in lung tumor cells. Mechanistically, ZK53 inhibits the adenoviral early region 2 binding factor targets and activates the ataxia-telangiectasia mutated-mediated DNA damage response, eventually triggering cell cycle arrest. Lastly, ZK53 exhibits therapeutic effects on lung squamous cell carcinoma cells in xenograft and autochthonous mouse models.

Apoptosis mechanisms induced by 15d-PMJ2 in HCT116 colon cancer cells: insights into CHOP10/TRB3/Akt signaling

Agents that stimulate the endoplasmic reticulum (ER) stress pathway are being exploited pharmacologically to induce cancer cell death. Cytotoxic ER stress is typically regulated by the transcription factor, C/EBP homologous protein 10 (CHOP10). Products of CHOP10 transcription include the pro-apoptotic proteins: ER oxidoreductase 1α (ERO1α), death receptor-5 (DR5), and tribbles-related protein 3 (TRB3). Our previous findings showed cell death induced by 15-deoxy- Δ12,14 prostamide J2 (15d-PMJ2) occurred in an ER stress-dependent manner. However, the pathway by which 15d-PMJ2 regulates ER stress-mediated death downstream of CHOP10 has not been identified. Our results demonstrate 5 µM 15d-PMJ2 increased CHOP10 expression and apoptosis in HCT116 colon cancer cells. In cells treated with pharmacological inhibitors of ER stress, 15d-PMJ2-induced apoptosis was reliant upon the ER stress pathway. To investigate the role of CHOP10 and its transcriptional products in apoptosis, genetic deletion of CHOP10 (CHOP10-KO) was performed using the CRISPR/Cas9 system. The apoptotic action of 15d-PMJ2 was blunted in cells lacking CHOP10 expression. The deletion of CHOP10 reduced the expression of DR5, ERO1α, and TRB3 although only the expression of TRB3 was significantly reduced. Therefore, we overexpressed TRB3 in CHOP10-KO cells and observed that the activation of Akt was inhibited and 15d-PMJ2-induced apoptosis was restored. Thus, a mechanism of apoptosis elicited by 15d-PMJ2 includes the stimulation of CHOP10/TRB3/Akt inhibition. Given the important role these signaling molecules play in cancer cell fate, 15d-PMJ2 may be an effective inducer of apoptosis in cancer cells.

Decoding Diffuse Midline Gliomas: A Comprehensive Review of Pathogenesis, Diagnosis and Treatment

Diffuse midline gliomas (DMGs) are a group of aggressive CNS tumors, primarily affecting children and young adults, which have historically been associated with dismal outcomes. As the name implies, they arise in midline structures in the CNS, primarily in the thalamus, brainstem, and spinal cord. In more recent years, significant advances have been made in our understanding of DMGs, including molecular features, with the identification of potential therapeutic targets. We aim to provide an overview of the most recent updates in the field of DMGs, including classification, molecular subtypes, diagnostic techniques, and emerging therapeutic strategies including a review of the ongoing clinical trials, thus providing the treating multidisciplinary team with a comprehensive understanding of the current landscape and potential therapeutic strategies for this devastating group of tumors.

Combating relapsed and refractory Mantle cell lymphoma with novel therapeutic armamentarium: Recent advances and clinical prospects

Mantle cell lymphoma (MCL) is a rare, aggressive subtype of non-Hodgkin's lymphoma (NHL), accounting for 5% of all cases. Due to its virulence factor, it is an incurable disease and keeps relapsing despite an intensive treatment regimen. Advancements in research and drug discovery have shifted the treatment strategy from conventional chemotherapy to targeted agents and immunotherapies. The establishment of the role of Bruton tyrosine kinase led to the development of ibrutinib, a first-generation BTK inhibitor, and its successors. A conditioning regimen based immunotherapeutic agent like ibritumumob, has also demonstrated a viable response with a favorable toxicity profile. Brexucabtagene Autoleucel, the only approved CAR T-cell therapy, has proven advantageous for relapsed/refractory MCL in both children and adults. This article reviews certain therapies that could help update the current approach and summarizes a few miscellaneous agents, which, seldom studied in trials, could alleviate the regression observed in traditional therapies. DATA AVAILABILITY: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

ONC201/TIC10 enhances durability of mTOR inhibitor everolimus in metastatic ER+ breast cancer

The mTOR inhibitor, everolimus, is an important clinical management component of metastatic ER+ breast cancer (BC). However, most patients develop resistance and progress on therapy, highlighting the need to discover strategies that increase mTOR inhibitor effectiveness. We developed ER+ BC cell lines, sensitive or resistant to everolimus, and discovered that combination treatment of ONC201/TIC10 with everolimus inhibited cell growth in 2D/3D in vitro studies. We confirmed increased therapeutic response in primary patient cells progressing on everolimus, supporting clinical relevance. We show that ONC201/TIC10 mechanism in metastatic ER+ BC cells involves oxidative phosphorylation inhibition and stress response activation. Transcriptomic analysis in everolimus resistant breast patient tumors and mitochondrial functional assays in resistant cell lines demonstrated increased mitochondrial respiration dependency, contributing to ONC201/TIC10 sensitivity. We propose that ONC201/TIC10 and modulation of mitochondrial function may provide an effective add-on therapy strategy for patients with metastatic ER+ BCs resistant to mTOR inhibitors.