ONC201 in combination with paxalisib for the treatment of H3K27-altered diffuse midline glioma

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.

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.

Management of patients with diffuse intrinsic pontine glioma in Australia and New Zealand: Australian and New Zealand Children's Haematology/Oncology Group position statement

INTRODUCTION

The main mission of the Australian and New Zealand Children's Haematology and Oncology Group (ANZCHOG) is to develop and facilitate local access to the world's leading evidence-based clinical trials for all paediatric cancers, including brain tumours, as soon as practically possible. Diffuse intrinsic pontine gliomas (DIPGs) - a subset of a larger group of tumours now termed diffuse midline glioma, H3K27-altered (DMG) - are paediatric brain cancers with less than 10% survival at two years. In the absence of any proven curative therapies, significant recent advancements have been made in pre-clinical and clinical research, leading many to seek integration of novel therapies early into standard practice. Despite these innovative therapeutic approaches, DIPG remains an incurable disease for which novel surgical, imaging, diagnostic, radiation and systemic therapy approaches are needed.

MAIN RECOMMENDATIONS

All patients with DIPG should be discussed in multidisciplinary neuro-oncology meetings (including pathologists, neuroradiologists, radiation oncologists, neurosurgeons, medical oncologists) at diagnosis and at relapse or progression. Radiation therapy to the involved field remains the local and international standard of care treatment. Proton therapy does not yield a superior survival outcome compared with photon therapy and patients should undergo radiation therapy with the available modality (photon or proton) at their treatment centre. Patients may receive concurrent chemotherapy or radiation-sensitising agents as part of a clinical trial. Biopsy should be offered to facilitate consideration of experimental therapies and eligibility for clinical trial participation. After radiation therapy, each patient should be managed individually with either observation or considered for enrolment on a clinical trial, if eligible, after full discussion with the family. Re-irradiation can be considered for progressive disease.

CHANGES IN MANAGEMENT AS A RESULT OF THE GUIDELINE

Every child diagnosed with DIPG should be offered enrolment on a clinical trial where available. Access to investigational drugs without biological rationale outside the clinical trial setting is not supported. In case of potentially actionable target identification with molecular profiling and absence of a suitable clinical trial, rational targeted therapies can be considered through compassionate access programs.

Current status and advances to improving drug delivery in diffuse intrinsic pontine glioma

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma - DIPG), is the primary cause of brain tumor-related death in pediatric patients. DIPG is characterized by a median survival of <12 months from diagnosis, harboring the worst 5-year survival rate of any cancer. Corticosteroids and radiation are the mainstay of therapy; however, they only provide transient relief from the devastating neurological symptoms. Numerous therapies have been investigated for DIPG, but the majority have been unsuccessful in demonstrating a survival benefit beyond radiation alone. Although many barriers hinder brain drug delivery in DIPG, one of the most significant challenges is the blood-brain barrier (BBB). Therapeutic compounds must possess specific properties to enable efficient passage across the BBB. In brain cancer, the BBB is referred to as the blood-brain tumor barrier (BBTB), where tumors disrupt the structure and function of the BBB, which may provide opportunities for drug delivery. However, the biological characteristics of the brainstem's BBB/BBTB, both under normal physiological conditions and in response to DIPG, are poorly understood, which further complicates treatment. Better characterization of the changes that occur in the BBB/BBTB of DIPG patients is essential, as this informs future treatment strategies. Many novel drug delivery technologies have been investigated to bypass or disrupt the BBB/BBTB, including convection enhanced delivery, focused ultrasound, nanoparticle-mediated delivery, and intranasal delivery, all of which are yet to be clinically established for the treatment of DIPG. Herein, we review what is known about the BBB/BBTB and discuss the current status, limitations, and advances of conventional and novel treatments to improving brain drug delivery in DIPG.

Selective DRD2 antagonist and ClpP agonist ONC201 in a recurrent non-midline H3 K27M-mutant glioma cohort

BACKGROUND

Diffuse midline glioma, H3 K27-altered (H3 K27M-altered DMG) are invariably lethal, disproportionately affecting the young and without effective treatment besides radiotherapy. The 2016 World Health Organization (WHO) Central Nervous System (CNS) Tumors Classification defined H3 K27M mutations as pathognomonic but restricted diagnosis to diffuse gliomas involving midline structures by 2018. Dordaviprone (ONC201) is an oral investigational small molecule, DRD2 antagonist, and ClpP agonist associated with durable responses in recurrent H3 K27M-mutant DMG. Activity of ONC201 in non-midline H3 K27M-mutant diffuse gliomas has not been reported.

METHODS

Patients with recurrent non-midline H3 K27M-mutant diffuse gliomas treated with ONC201 were enrolled in 5 trials. Eligibility included measurable disease by Response Assessment in Neuro-Oncology (RANO) high-grade glioma, Karnofsky/Lansky performance score ≥60, and ≥90 days from radiation. The primary endpoint was overall response rate (ORR).

RESULTS

Five patients with cerebral gliomas (3 frontal, 1 temporal, and 1 parietal) met inclusion. One complete and one partial response were reported by investigators. Blinded independent central review confirmed ORR by RANO criteria for 2, however, 1 deemed nonmeasurable and another stable. A responding patient also noted improved mobility and alertness.

CONCLUSIONS

H3 K27M-mutant diffuse gliomas occasionally occur in non-midline cerebrum. ONC201 exhibits activity in H3 K27M-mutant gliomas irrespective of CNS location.

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.

Just a spoonful of metformin helps the medicine go down

Diffuse intrinsic pontine glioma (DIPG) is a devastating brain tumor with a need for novel therapies. So far, monotherapies have failed to prolong survival for these patients, and combinatorial strategies have often shown severe, dose-limiting toxicities. In this issue of the JCI, Duchatel, Jackson, and colleagues address this challenge by introducing a drug combination that mitigates side effects and overcomes resistance. After identifying the PI3K/mTOR pathway as a therapeutic vulnerability, they treated DIPG-bearing mice with paxalisib and saw responses but also observed hyperglycemia as a severe side effect. Combining paxalisib with metformin mitigated this toxicity, but also upregulated protein kinase C (PKC) signaling. To tackle this mechanism of resistance, the authors added the PKC inhibitor enzastaurin to their drug combination and showed that this triple therapy led to improved survival. This approach paves the way for improved outcomes for patients with DIPG and other brain tumors.

The role of adjuvant chemotherapy in patients with H3K27 altered diffuse midline gliomas: a multicentric retrospective study

PURPOSE

Adult Diffuse midline glioma (DMG) is a very rare disease. DMGs are currently treated with radiotherapy and chemotherapy even if only a few retrospective studies assessed the impact on overall survival (OS) of these approaches.

METHODS

We carried out an Italian multicentric retrospective study of adult patients with H3K27-altered DMG to assess the effective role of systemic therapy in the treatment landscape of this rare tumor type.

RESULTS

We evaluated 49 patients from 6 Institutions. The median age was 37.3 years (range 20.1-68.3). Most patients received biopsy as primary approach (n = 30, 61.2%) and radiation therapy after surgery (n = 39, 79.6%). 25 (51.0%) of patients received concurrent chemotherapy and 26 (53.1%) patients received adjuvant temozolomide. In univariate analysis, concurrent chemotherapy did not result in OS improvement while adjuvant temozolomide was associated with longer OS (21.2 vs. 9.0 months, HR 0.14, 0.05-0.41, p < 0.001). Multivariate analysis confirmed the role of adjuvant chemotherapy (HR 0.1, 95%CI: 0.03-0.34, p = 0.003). In patients who progressed after radiation and/or chemotherapy the administration of a second-line systemic treatment had a significantly favorable impact on survival (8.0 vs. 3.2 months, HR 0.2, 95%CI 0.1-0.65, p = 0.004).

CONCLUSION

In our series, adjuvant treatment after radiotherapy can be useful in improving OS of patients with H3K27-altered DMG. When feasible another systemic treatment after treatment progression could be proposed.

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.

From signalling pathways to targeted therapies: unravelling glioblastoma's secrets and harnessing two decades of progress

Glioblastoma, a rare, and highly lethal form of brain cancer, poses significant challenges in terms of therapeutic resistance, and poor survival rates for both adult and paediatric patients alike. Despite advancements in brain cancer research driven by a technological revolution, translating our understanding of glioblastoma pathogenesis into improved clinical outcomes remains a critical unmet need. This review emphasises the intricate role of receptor tyrosine kinase signalling pathways, epigenetic mechanisms, and metabolic functions in glioblastoma tumourigenesis and therapeutic resistance. We also discuss the extensive efforts over the past two decades that have explored targeted therapies against these pathways. Emerging therapeutic approaches, such as antibody-toxin conjugates or CAR T cell therapies, offer potential by specifically targeting proteins on the glioblastoma cell surface. Combination strategies incorporating protein-targeted therapy and immune-based therapies demonstrate great promise for future clinical research. Moreover, gaining insights into the role of cell-of-origin in glioblastoma treatment response holds the potential to advance precision medicine approaches. Addressing these challenges is crucial to improving outcomes for glioblastoma patients and moving towards more effective precision therapies.

Multifaceted role of mTOR (mammalian target of rapamycin) signaling pathway in human health and disease

The mammalian target of rapamycin (mTOR) is a protein kinase that controls cellular metabolism, catabolism, immune responses, autophagy, survival, proliferation, and migration, to maintain cellular homeostasis. The mTOR signaling cascade consists of two distinct multi-subunit complexes named mTOR complex 1/2 (mTORC1/2). mTOR catalyzes the phosphorylation of several critical proteins like AKT, protein kinase C, insulin growth factor receptor (IGF-1R), 4E binding protein 1 (4E-BP1), ribosomal protein S6 kinase (S6K), transcription factor EB (TFEB), sterol-responsive element-binding proteins (SREBPs), Lipin-1, and Unc-51-like autophagy-activating kinases. mTOR signaling plays a central role in regulating translation, lipid synthesis, nucleotide synthesis, biogenesis of lysosomes, nutrient sensing, and growth factor signaling. The emerging pieces of evidence have revealed that the constitutive activation of the mTOR pathway due to mutations/amplification/deletion in either mTOR and its complexes (mTORC1 and mTORC2) or upstream targets is responsible for aging, neurological diseases, and human malignancies. Here, we provide the detailed structure of mTOR, its complexes, and the comprehensive role of upstream regulators, as well as downstream effectors of mTOR signaling cascades in the metabolism, biogenesis of biomolecules, immune responses, and autophagy. Additionally, we summarize the potential of long noncoding RNAs (lncRNAs) as an important modulator of mTOR signaling. Importantly, we have highlighted the potential of mTOR signaling in aging, neurological disorders, human cancers, cancer stem cells, and drug resistance. Here, we discuss the developments for the therapeutic targeting of mTOR signaling with improved anticancer efficacy for the benefit of cancer patients in clinics.

CAR T cell therapies for diffuse midline glioma

Diffuse midline glioma (DMG) is a fatal pediatric cancer of the central nervous system (CNS). The location and infiltrative nature of DMG prevents surgical resection and the benefits of palliative radiotherapy are temporary; median overall survival (OS) is 9-11 months. The tumor immune microenvironment (TIME) is 'cold', and has a dominant immunosuppressive myeloid compartment with low levels of infiltrating lymphocytes and proinflammatory molecules. Because survival statistics have been stagnant for many decades, and therapies targeting the unique biology of DMG are urgently needed, this has prompted the clinical assessment of chimeric antigen receptor (CAR) T cell therapies in this setting. We highlight the current landscape of CAR T cell therapy for DMG, the role the TIME may play in the response, and strategies to overcome treatment obstacles.

Bridging the age gap: a review of molecularly informed treatments for glioma in adolescents and young adults

Gliomas are the most common primary central nervous system (CNS) tumors and a major cause of cancer-related mortality in children (age <15 years), adolescents and young adults (AYA, ages 15-39 years), and adults (age >39 years). Molecular pathology has helped enhance the characterization of these tumors, revealing a heterogeneous and ever more complex group of malignancies. Recent molecular analyses have led to an increased appreciation of common genomic alterations prevalent across all ages. The 2021 World Health Organization (WHO) CNS tumor classification, 5th edition (WHO CNS5) brings forward a nomenclature distinguishing "pediatric-type" and "adult-type" gliomas. The spectrum of gliomas in AYA comprises both "pediatric-like" and "adult-like" tumor entities but remains ill-defined. With fragmentation of clinical management between pediatric and adult centers, AYAs face challenges related to gaps in medical care, lower rates of enrollment in clinical trials and additional psychosocial and economic challenges. This calls for a rethinking of diagnostic and therapeutic approaches, to improve access to appropriate testing and potentially beneficial treatments to patients of all ages.