Convection-enhanced Delivery Research Articles

A Spatial Interpolation Approach to Assign MRI-Derived Material Properties for Finite Element Models of Aav Infusion Into a Recurrent Brain Tumor.

Adeno-associated virus (AAV) has been demonstrated to be a clinically useful gene delivery vehicle for treating neurological diseases. To deliver AAV to focal targets, direct infusion into brain tissue by convection-enhanced delivery (CED) is often needed due to AAV's limited penetration across the blood-brain-barrier and its low tissue diffusivity. In this study, computational models that predict the spatial distribution of AAV in brain tissue during CED were developed to guide surgical placement of infusion catheters in recurrent brain tumors following primary tumor resection. The brain was modeled as a porous medium, and material properties were interpolated and directly assigned to the model from MRI images. This novel approach facilitates volume segmentation and mesh preparation. The infusion model predicted preferential fluid diversion into open fluid regions such as the ventricles and subarachnoid space. Additionally, a sensitivity analysis of AAV delivery demonstrated that improved AAV distribution in the tumor was achieved at higher tumor hydraulic conductivity or lower tumor porosity. Depending on the tumor infusion site, the AAV distribution covered 3.67% to 70.25% of the tumor volume (using a 10% AAV concentration threshold), demonstrating the model's potential to assist in the selection of infusion sites for maximal tumor coverage.

266 Combination Drug Therapy in H3 K27-Altered Diffuse Midline Glioma Enhances Tumor Retention and Treatment Efficacy

INTRODUCTION: Diffuse midline gliomas (DMG) with H3 K27 alterations are uniformly lethal tumors for which no therapy has been found to be effective. One reason for our therapy failure is the blood-brain barrier (BBB), which severely restricts uptake and accumulation of systemically administered drugs in the brain. Convection-enhanced delivery (CED) has emerged as a technique that circumvents the BBB by directly infusing therapeutics into the tumor parenchyma through generation of a mechanical pressure gradient, allowing for homogenous drug distribution at high local concentrations with minimal systemic toxicity. However, efflux transport proteins expressed by the BBB and the tumor, including P-gp and BCRP, rapidly clear the majority of drugs given by CED, severely limiting its therapeutic potential. METHODS: A panel of FDA-approved drugs (ponatinib, topotecan, tretinoin) were evaluated alone and in combination with the known efflux transporter inhibitor everolimus. RESULTS: A high degree of formal synergy was observed in multiple DMG cell lines in vitro, which was attributed to everolimus’ ability to inhibit mTOR signaling and P-gp/BCRP. In vivo, drugs that were expected to penetrate the BBB and be less likely to undergo active efflux persisted at the site of infusion the longest following CED. Concurrent dosing with everolimus further enhanced this effect, which was particularly apparent with the dual P-gp/BCRP substrate ponatinib. CONCLUSIONS: The proclivity of many drugs to be rapidly cleared from the brain by efflux transporters generates a vulnerability that can be exploited for the development of novel therapeutic regimens in DMG, such as with concomitant dosing of P-gp/BCRP-inhibiting drugs when using CED.

129 Neuroimaging Analysis of Bilateral Thalamic Delivery for Gene Therapy

INTRODUCTION: Axonal transport from the thalamus (an integrative hub for the entire cortex) has been shown to facilitate widespread gene/protein delivery. Here, we report our neuroimaging experience with bilateral thalamic convection-enhanced delivery of adeno-associated virus (AAV) vectors for GM2 gangliosidoses. METHODS: Magnetic resonance imaging (MRI) of eight pediatric patients who underwent bilateral thalamic HEXA/HEXB delivery were retrospectively reviewed. Quantitative three-dimensional volumetric analyses of MRI thalamic signals were used to establish volume of distribution (Vd) versus volume of infusion (Vi). The distance of cannula placement within the thalamus was calculated and validated using the numbers used in the intraoperative ROSA robotic software. Backflow and leakage into surrounding structures were also analyzed. RESULTS: Fourteen thalamic injection volumes were considered in the final analysis. Calculated volume of thalamic infusate signal was up to 43.8% (mean = 21.3±13.3) of the thalamic volume. The Vd/Vi ratio ranged from 0.4-2.7 (mean = 1.9±0.7), depending on infusate volume. Diffusate shape was round to slightly ellipsoid in all patients. Backflow and leakage were encountered in 14.3% and 12.5%, respectively, of thalamic injections. CONCLUSIONS: This study provides the first in-human quantitative MRI data for intrathalamic infusion. The ideal location for the cannula tip was determined to be between the mediodorsal and lateral dorsal nuclei and the ideal trajectory keeps all of the cannula steps within the thalamic boundaries. We also compare these data to published NHP and our own NHP and sheep data. Overall, the Vd/Vi ratios are lower in human subjects (∼2) than in animal subjects (∼3). We hypothesize that this may be due in part to species specific differences in displacement of extracellular fluid versus infusion volume.

Abstract 7117: Convection enhanced delivery of a novel ATR inhibitor synergizes with systemic lomustine for improved treatment of glioblastoma

Abstract Developing effective strategies for treating glioblastoma (GBM), the most common and aggressive form of brain cancer, has been a long-standing challenge. Despite rigorous treatment regimens including surgical resection with concomitant radiotherapy and chemotherapy, the prognosis for this disease remains poor, largely due to tumor recurrence, resistance to conventional therapeutics, pharmacokinetic and brain delivery challenges, and dose-limiting toxicities of existing therapies. The DNA damage response and DNA repair mechanisms such as the ataxia telangiectasia and Rad3-related (ATR) pathway are key mediators of therapeutic responses, and recent studies have shown that targeting DNA repair proteins alongside standard-of-care options is a promising anti-tumor strategy. Here, we employ a combination approach using a next-generation macrocyclic ATR inhibitor, ATRIN-333, to sensitize GBM tumors to alkylators. We establish the potency of ATRIN-333 and report a robust synergistic interaction between it and the alkylator lomustine in GBM cell-based assays and in a murine flank tumor model. This combinatorial treatment was then applied to a mouse intracranial tumor model, where we utilized a convection enhanced delivery (CED) system combined with nanoparticle technology for direct intracranial administration of ATRIN-333. ATRIN-333 was successfully encapsulated into a novel polymeric nanoparticle formulation using poly(ethylene glycol)-co-poly(ethylene brassylate-co-dioxanone) (PEG-EB-co-DO). CED of both free and encapsulated ATRIN-333 potently sensitized intracranial GBM tumors to low-dose (5 mg/kg) systemically-delivered lomustine, reducing tumor size and conferring a substantial survival benefit compared to cohorts treated with lomustine or the ATR inhibitor alone. The combination approach was well tolerated by the mice, with no hematological toxicity observed as assessed by bone marrow analysis and blood cell counts. Our results demonstrate that ATR inhibitor/lomustine combination therapy, used in conjunction with a CED platform, is a powerful avenue for GBM treatment and a viable option for potential clinical implementation. Note: AJ and TL contributed equally to this work. Citation Format: Alexander Josowitz, Teresa Lee, Ranjini K. Sundaram, Jinal Pothupitiya, Eric J. Brown, Amrita Sule, Jason Beckta, Yongheng Wang, Joseph Vacca, Oren Gilad, Ranjit S. Bindra, W Mark Saltzman. Convection enhanced delivery of a novel ATR inhibitor synergizes with systemic lomustine for improved treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7117.

Convection-Enhanced Drug Delivery: Experimental and Analytical Studies of Infusion Behavior in an In Vitro Brain Surrogate.

Convection-enhanced drug delivery (CED) directly infuses drugs with a large molecular weight toward target cells as a therapeutic strategy for neurodegenerative diseases and brain cancers. Despite the success of many previous in vitro experiments on CED, challenges still remain. In particular, a theoretical predictive model is needed to form a basis for treatment planning, and developing such a model requires well-controlled injection tests that can rigorously capture the convective (advective) and diffusive transport of an infusate. For this purpose, we investigated the advection-diffusion transport of an infusate (bromophenol blue solution) in the brain surrogate (0.2% w/w agarose gel) at different injection rates, ranging from 0.25 to 4 μL/min, by closely monitoring changes in the color intensity, propagation distance, and injection pressures. One dimensional closed-form solution was examined with two variable sets, such as the mathematically calculated coefficient of molecular diffusion and average velocity, and the hydraulic dispersion coefficient and seepage velocity by the least squared method. As a result, the seepage velocity was greater than the average velocity to some extent, particularly for the later infusion times. The poroelastic deformation in the brain surrogate might lead to changes in porosity, and consequently, slight increases in the actual flow velocity as infusion continues. The limitation of efficiency of the single catheter was analyzed by dimensionless analysis. Lastly, this study suggests a simple but robust approach that can properly capture the convective (advective) and diffusive transport of an infusate in an in vitro brain surrogate via well-controlled injection tests.

Abstract A033: Murine CNS and bone marrow distribution of the aurora A kinase inhibitor alisertib: Pharmacokinetics and exposure at the sites of efficacy and toxicity

Abstract A033: Murine CNS and bone marrow distribution of the aurora A kinase inhibitor alisertib: Pharmacokinetics and exposure at the sites of efficacy and toxicity

Abstract B023: CNS and systemic pharmacokinetics of antibody-drug conjugate payloads through convection-enhanced delivery

Abstract B023: CNS and systemic pharmacokinetics of antibody-drug conjugate payloads through convection-enhanced delivery

Implantable theranostic device for in vivo real-time NMR evaluation of drug impact in brain tumors.

The evaluation of the efficacy of a drug is a fundamental step in the development of new treatments or in personalized therapeutic strategies and patient management. Ideally, this evaluation should be rapid, possibly in real time, easy to perform and reliable. In addition, it should be associated with as few adverse effects as possible for the patient. In this study, we present a device designed to meet these goals for assessing therapeutic response. This theranostic device is based on the use of magnetic resonance imaging and spectroscopy for the diagnostic aspect and on the application of the convection-enhanced delivery technique for the therapeutic aspect. The miniaturized device is implantable and can be used in vivo in a target tissue. In this study, the device was applied to rodent glioma models with local administration of choline kinase inhibitor and acquisition of magnetic resonance images and spectra at 7 Tesla. The variations in the concentration of key metabolites measured by the device during the administration of the molecules demonstrate the relevance of the approach and the potential of the device.

Epidermal Growth Factor Receptor Inhibitors in Glioblastoma: Current Status and Future Possibilities.

Glioblastoma, a grade 4 glioma as per the World Health Organization, poses a challenge in adult primary brain tumor management despite advanced surgical techniques and multimodal therapies. This review delves into the potential of targeting epidermal growth factor receptor (EGFR) with small-molecule inhibitors and antibodies as a treatment strategy. EGFR, a mutationally active receptor tyrosine kinase in over 50% of glioblastoma cases, features variants like EGFRvIII, EGFRvII and missense mutations, necessitating a deep understanding of their structures and signaling pathways. Although EGFR inhibitors have demonstrated efficacy in other cancers, their application in glioblastoma is hindered by blood-brain barrier penetration and intrinsic resistance. The evolving realm of nanodrugs and convection-enhanced delivery offers promise in ensuring precise drug delivery to the brain. Critical to success is the identification of glioblastoma patient populations that benefit from EGFR inhibitors. Tools like radiolabeled anti-EGFR antibody 806i facilitate the visualization of EGFR conformations, aiding in tailored treatment selection. Recognizing the synergistic potential of combination therapies with downstream targets like mTOR, PI3k, and HDACs is pivotal for enhancing EGFR inhibitor efficacy. In conclusion, the era of precision oncology holds promise for targeting EGFR in glioblastoma, contingent on tailored treatments, effective blood-brain barrier navigation, and the exploration of synergistic therapies.

Blood-Brain Barrier Disruption for the Treatment of Primary Brain Tumors: Advances in the Past Half-Decade.

To review relevant advances in the past half-decade in the treatment of primary brain tumors via modification of blood-brain barrier (BBB) permeability. BBB disruption is becoming increasingly common in the treatment of primary brain tumors. Use of mannitol in BBB disruption for targeted delivery of chemotherapeutics via superselective intra-arterial cerebral infusion (SIACI) is the most utilized strategy to modify the BBB. Mannitol is used in conjunction with chemotherapeutics, oligonucleotides, and other active agents. Convection-enhanced delivery has become an attractive option for therapeutic delivery while bypassing the BBB. Other technologic innovations include laser interstitial thermal therapy (LITT) and focused ultrasound (FUS) which have emerged as prime modalities to directly target tumors and cause significant local BBB disruption. In the past 5years, interest has significantly increased in studying modalities to disrupt the BBB in primary brain tumors to enhance treatment responses and improve clinical outcomes.

Convection-enhanced Diffusion: A Novel Tactics to Crack the BBB.

Although the brain is very accessible to nutrition and oxygen, it can be difficult to deliver medications to malignant brain tumours. To get around some of these issues and enable the use of therapeutic pharmacological substances that wouldn't typically cross the blood-brain barrier (BBB), convection-enhanced delivery (CED) has been developed. It is a cutting-edge strategy that gets beyond the blood-brain barrier and enables targeted drug administration to treat different neurological conditions such as brain tumours, Parkinson's disease, and epilepsy. Utilizing pressure gradients to spread the medicine across the target area is the main idea behind this diffusion mechanism. Through one to several catheters positioned stereotactically directly within the tumour mass, around the tumour, or in the cavity created by the resection, drugs are given. This method can be used in a variety of drug classes, including traditional chemotherapeutics and cutting-edge investigational targeted medications by using positive-pressure techniques. The drug delivery volume must be optimized for an effective infusion while minimizing backflow, which causes side effects and lowers therapeutic efficacy. Therefore, this technique provides a promising approach for treating disorders of the central nervous system (CNS).

Breaking Barriers in Neuro-Oncology: A Scoping Literature Review on Invasive and Non-Invasive Techniques for Blood-Brain Barrier Disruption.

The blood-brain barrier (BBB) poses a significant challenge to drug delivery for brain tumors, with most chemotherapeutics having limited permeability into non-malignant brain tissue and only restricted access to primary and metastatic brain cancers. Consequently, due to the drug's inability to effectively penetrate the BBB, outcomes following brain chemotherapy continue to be suboptimal. Several methods to open the BBB and obtain higher drug concentrations in tumors have been proposed, with the selection of the optimal method depending on the size of the targeted tumor volume, the chosen therapeutic agent, and individual patient characteristics. Herein, we aim to comprehensively describe osmotic disruption with intra-arterial drug administration, intrathecal/intraventricular administration, laser interstitial thermal therapy, convection-enhanced delivery, and ultrasound methods, including high-intensity focused and low-intensity ultrasound as well as tumor-treating fields. We explain the scientific concept behind each method, preclinical/clinical research, advantages and disadvantages, indications, and potential avenues for improvement. Given that each method has its limitations, it is unlikely that the future of BBB disruption will rely on a single method but rather on a synergistic effect of a combined approach. Disruption of the BBB with osmotic infusion or high-intensity focused ultrasound, followed by the intra-arterial delivery of drugs, is a promising approach. Real-time monitoring of drug delivery will be necessary for optimal results.

Chronic intermittent convection-enhanced delivery of vigabatrin to the bilateral subthalamic nucleus in an acute rat seizure model

Targeted intracerebral drug delivery is an attractive experimental approach for the treatment of drug-resistant epilepsies. In this regard, the subthalamic nucleus (STN) represents a focus-independent target involved in the remote modulation and propagation of seizure activity. Indeed, acute and chronic pharmacological inhibition of the STN with vigabatrin (VGB), an irreversible inhibitor of GABA transaminase, has been shown to produce antiseizure effects. This effect, however, is lost over time as tolerance develops with chronic, continuous intracerebral pharmacotherapy. Here we investigated the antiseizure effects of chronic intermittent intra-STN convection-enhanced delivery of VGB in an acute rat seizure model focusing on circumventing tolerance development and preventing adverse effects. Timed intravenous pentylenetetrazol (PTZ) seizure threshold testing was conducted before and after implantation of subcutaneous drug pumps and bilateral intra-STN cannulas. Drug pumps infused vehicle or VGB twice daily (0.4 µg) or once weekly (2.5 µg, 5 µg) over three weeks. Putative adverse effects were evaluated and found to be prevented by intermittent compared to previous continuous VGB delivery. Clonic seizure thresholds were more clearly raised by intra-STN VGB compared to myoclonic twitch. Both twice daily and once weekly intra-STN VGB significantly elevated clonic seizure thresholds depending on dose and time point, with responder rates of up to 100% observed at tolerable doses. However, tolerance could not be completely avoided, as tolerance rates of 40–75% were observed with chronic VGB treatment. Results indicate that the extent of tolerance development after intermittent intra-STN VGB delivery varies depending on infusion dose and regimen.

DDEL-05. PHARMACOKINETIC ASSESSMENT OF CONVECTION-ENHANCED DELIVERY OF SMALL MOLECULE DRUGS FOR H3 K27-ALTERED DIFFUSE MIDLINE GLIOMA

Abstract H3 K27-altered diffuse midline gliomas (DMG) are uniformly lethal tumors for which no therapy has been found to be effective. The blood-brain barrier (BBB) restricts uptake and accumulation of systemically administered drugs in the brain. Convection-enhanced delivery (CED) circumvents the BBB by directly infusing therapeutics into the tumor, facilitating homogenous distribution of drugs at high local concentrations with minimal systemic toxicity. However, most drugs given by CED are rapidly cleared from the brain, severely limiting its therapeutic potential. Here, we determine the impact of drug characteristics rather than mechanism of action on compatibility with CED. Various medicinal chemistry prediction models were interrogated to define drug categories predicated on inherent physicochemical properties of the drugs. A panel of FDA-approved drugs with biologically validated activity in DMG were selected for each group: panobinostat/ponatinib, everolimus/topotecan, tolnaftate/tretinoin, and carmofur/eltrombopag. In vivo pharmacokinetic studies of these drugs delivered by CED into the pons of tumor-naïve mice showed that drugs expected to be less likely to undergo active efflux persisted at the site of infusion over prolonged periods of time. Conversely, efflux transporter (ET) substrate drugs were quickly excreted from the brain and readily detectable in the plasma following CED. Based on the observed brain and plasma concentration-time profiles, the brain exit rate constant and clearance out of the brain were much higher for ET substrate drugs compared with ET non-substrates, resulting in a significant increase in the residence time (the time spent by drugs in the brain) in the absence of ET-mediated clearance. These properties were further validated in efficacy studies in DMG animal models. The proclivity of many drugs to be rapidly effluxed from the brain after CED generates a vulnerability that can be exploited for the development of novel therapeutic regimens, such as with pharmacokinetics-informed drug selection or concomitant dosing of ET-inhibiting drugs.

BIOS-01. EFFICACY AMONG THERAPEUTICALLY EFFECTIVE ABSORBED DOSE PATIENTS IN RESPECT-GBM PHASE I OF RHENIUM-186 NANOLIPOSOME (186RNL) IN RECURRENT GLIOBLASTOMA (RGBM) COMPARED TO AN EXTERNAL CONTROL ARM (ECA)

Abstract BACKGROUND ReSPECT-GBM is a Phase 1/2 study of 186RNL administered by convection enhanced delivery (CED) in patients with rGBM. In Phase I, 15 of 24 patients have achieved a therapeutic absorbed dose defined as > 100 Gy. Based on prior work establishing the comparability of a bevacizumab (Bev) comparator to inform early-phase CED study results, OS of the 15 TAD patients were compared to a Bev ECA. METHODS Recent Bev-treated rGBM clinical trial patients meeting the same eligibility criteria as patients in the ReSPECT-GBM study were identified from the Medidata Enterprise Data Store of aggregated and deidentified patient-level historical clinical trial data. Propensity score (PS) methods were used to select the ECA and align the baseline characteristics of the Bev patients to the ReSPECT TAD cohort. OS estimates were generated using the weighted Kaplan-Meier method and compared with a weighted 2-sample 2-sided log-rank test at α = 0.05 based on a data cut-off of December 2022. RESULTS Baseline characteristics of the ReSPECT TAD and ECA patients were well-aligned after PS modeling. Although not achieving statistical significance due to small sample sizes (median OS 12.2 vs 10.1 months, hazard ratio 0.63, 95% CI: 0.26, 1.52), comparison of OS between the ReSPECT TAD and ECA patients demonstrate consistently longer OS at each 6-month interval: 6 months: 85.1% vs 73.3%, 12 mos: 51.1% vs 30.3%, 18 months: 30.6% vs 25.4%, 24 months: 30.6% vs 3.5%. CONCLUSIONS Single-arm studies can be challenging to interpret. By comparing the ReSPECT-GBM outcomes to an ECA of similar patients with balanced baseline characteristics, we can better appreciate the treatment effect of 186RNL administered via CED. The current results are encouraging, and updated results reflecting current follow-up will be presented at the meeting.

EXTH-68. SYSTEMIC NEUTRALIZATION OF IL6 SENSITIZES IDH-WILDTYPE GLIOBLASTOMA PRECLINICAL MODELS TO IMMUNE CHECKPOINT INHIBITION

Abstract IDH-wildtype glioblastomas are resistant to immune checkpoint inhibition (ICI). Here we integrate spatial and single-cell approaches across paired human glioblastomas before or after ICI with functional studies in immunocompetent intracranial mouse glioblastoma models to reveal mechanisms and therapeutic vulnerabilities underlying glioblastoma resistance to ICI. Spatial proteomic and transcriptomic approaches were used to identify biochemical and gene expression programs underlying ICI response or resistance in paired human glioblastoma samples (n = 7). Intracranial SB28 glioblastoma allografts were implanted in C57BL/6J mice and treated with (1) convection enhanced delivery (CED) of AAV9 gene therapy vectors encoding cytokines that reprogram the tumor immune microenvironment (TIME) in other cancers (Il1b, Ccl4, Apoa1), (2) systemic anti-PD1, (3) local anti-IL6, (4) systemic anti-IL6, or (5) combination systemic treatment with anti-PD1 and anti-IL6. Histological, mass cytometry (CyTOF), and multiplexed cytokine assays were used to assess the glioblastoma TIME in response to treatment over time. Mice were monitored for survival and tumor growth was measured using intracranial bioluminescence. Human glioblastomas with radiographic responses to ICI had lower pre-treatment IL6 levels on spatial profiling than glioblastomas resistant to ICI. Intratumor IL6 was suppressed by all AAV9 cytokine conditions compared to AAV9-GFP in mice. Mouse survival was improved by combination systemic treatment with anti-PD1 and anti-IL6, but was not improved by either antibody alone, or by anti-IL6 CED. CyTOF revealed combination systemic therapy reprogrammed the glioblastoma TIME by increasing activated immune cell types such as MHCII+ monocytes, CD103+ migratory dendritic cells (DCs), CD11b+ conventional DCs, and effector CD8+ T cells, and by decreasing immunosuppressive Tregs. In summary, systemic anti-IL6 in combination with systemic anti-PD1 reprograms the glioblastoma TIME to sensitize preclinical models to ICI. These results provide mechanistic validation of findings from human glioblastomas that respond to ICI and shed light on a therapeutic vulnerability underlying the glioblastoma TIME.

EXTH-49. A NOVEL MULTIVALENT DRUG CONJUGATE FOR HIGH-GRADE GLIOMA TREATMENT

Abstract Interleukin 13 receptor alpha 2 (IL-13RA2), EphA2, EphA3 and EphB2 receptors are over-expressed collectively in almost all patients with glioblastoma (GBM), and also in spontaneous canine gliomas, the most faithful model of human disease. The four receptors are widely present in various compartments of GBM tumors, including tumor core, infiltrating cells, tumor neovasculature and tumor-associated macrophages. Thus, the four receptors are expressed in several GBM compartments involved in tumor progression and/or resistance to therapies, covering almost 100% of the tumor microenvironment. In first-of-a-kind approach, we performed Phase I clinical trial in dogs with gliomas using a cocktail of cytotoxins targeting IL-13RA2 and EphA2 receptor. The cocktail was administered loco-regionally through convection-enhanced delivery, using anti-reflux catheters and real-time MRI monitoring of drugs distribution. We observed prominent anti-tumor responses, including several near complete regressions, prolongation of survival and excellent quality of life, although we did not achieve dose-limiting toxicity (Neuro-Oncol 2021;23(3):422-434). Encouraged by these exceptional results, we pursued the novel idea of targeting the four GBM-associated receptors with one pharmaceutical compound. To this end, we designed, produced, and tested a multivalent ligand binding to all four receptors of our interest, termed QUAD, including murine and canine receptors. However, we found that a conjugate of QUAD with DM1, a microtubule-disrupting agent, demonstrated an extremely high (in low picomolar range) and specific killing potency on GBM cells. The IC50s of QUAD-DM1 are ~50 times higher than that for all other QUAD-based drug conjugates tested thus far, having a favorable toxicity profile in rodents when injected either intracranially or intravenously. QUAD-DM1 has already produced up to 95% tumor reduction in dogs with spontaneous brain tumors. QUAD-DM1 is a highly promising agent for the treatment of human and canine high-grade gliomas.

EXTH-20. A MOUSE MODEL REVEALS VULNERABILITY OF IDH1-MUTATED GLIOMA TO FERROPTOSIS

Abstract The molecular classification of gliomas is currently based on the presence of IDH1 mutation, which is associated with better prognosis and longer survival. The hallmark of the IDH1 mutation is the production of D-2-Hydroxyglutarate with subsequent effects that are not fully understood. Ferroptosis, an iron-dependent mechanism of non-apoptotic cell death, is mostly triggered through blocking system Xc- or suppressing the antioxidant enzyme glutathione peroxidase 4 (GPX-4). In this study, we generated a mouse model of glioma harboring the IDH1(R132H) mutation in heterozygous condition, in combination with p53-deletion induced by the expression of PDGFA. We show that IDH1(R132H)-expressing mice survive longer compared to their wild-type counterparts, while histological analysis reveals characteristics of low-grade diffuse gliomas. We generated cell lines from primary tumors and analyzed their metabolic profile and response to mitochondrial stress and Ferroptosis. We treated them in vitro with RSL3, a GPX-4 inhibitor, alone or in combination with Cysteine and Methionine restriction. We show that IDH1(R132H)-expressing cells are far more sensitive to Ferroptosis in vitro. Finally, we show that convection-enhanced delivery of RSL3 in combination with dietary Cysteine and Methionine restriction in vivo, significantly prolongs survival of the IDH1(R132H)-expressing mice. Our findings suggest that Ferroptosis provides promising therapeutic potential worth exploring further and our mouse model could be used to test the efficacy of different treatments for IDH1(R132H) gliomas.

CTNI-52. SURVIVAL OUTCOMES IN RECURRENT GLIOBLASTOMA (RGBM) PATIENTS TREATED WITH A SINGLE INTRA-TUMORAL ADMINISTRATION OF BIZAXOFUSP, AN IL-4R-TARGETING TOXIN, IN A PHASE IIB TRIAL

Abstract BACKGROUND Bizaxofusp (MDNA55) is an IL4R-targeting toxin in development for recurrent (r)GBM, a universally fatal disease with mOS of 6-9 months. IL-4R is overexpressed in GBM and surrounding tumor microenvironment, with high expression associated with poor clinical outcome. Method: Efficacy and safety were evaluated in a single-arm, open-label, multi-center Ph2 study using convection-enhanced delivery of Bizaxofusp. The primary endpoint of mOS was compared to results from a blinded eligibility-matched external control arm (ECA). OS was defined as time from relapse to death/censor. IL-4R expression was determined by immunohistochemistry of available archival tumor tissues from both arms. RESULTS Bizaxofusp showed an acceptable safety profile at doses of up to 240 μg. Forty-four subjects were treated with Bizaxofusp per protocol; 81 ECA subjects met the eligibility criteria of the study. The Bizaxofusp group had a significantly longer mOS (12.85 months compared to 7.7 months for ECA; HR, 0.62; 95% CI, 0.42-0.89). Amongst the unmethylated MGMT and high IL-4R sub-groups, subjects treated with Bizaxofusp had significantly longer mOS when compared to the ECA. Eleven patients (25%) treated with Bizaxofusp survived >24 months; 3 patients were still alive (29.9, 32.8 and 40.1 months) at last follow-up. High IL-4R expression was associated with improved survival (mOS, 15.8 versus 9.8 months; HR, 0.7; 95% CI, 0.39-1.46) at all doses. However at high doses (180 μg) subjects with low IL-4R expression had significantly longer survival versus low dose Bizaxofusp (mOS, 15.4 versus 9.1 months; HR, 0.28; 95% CI, 0.09-0.91). CONCLUSION In patients with rGBM, a single treatment of Bizaxofusp resulted in significantly improved OS compared to eligibility-matched ECA. High-dose Bizaxofusp was equally effective irrespective of IL4R expression. A Phase 3 registration trial will use a novel hybrid design with a propensity-matched ECA comprising two-thirds of the control arm, setting a new precedent for GBM clinical trials.

Magnetic Resonance Imaging–Aided SmartFlow Convection Delivery of DNX-2401: A Pilot, Prospective Case Series

The Combination Adenovirus+ Pembrolizumab to Trigger Immune Virus Effects (CAPTIVE) study is a phase II clinical trial testing the efficacy of a recombinant adenovirus DNX-2401 combined with the immune checkpoint inhibitor pembrolizumab. Here, we report the first patients in this study who underwent viral delivery through real-time magnetic resonance imaging (MRI) stereotaxis-guided SmartFlow convection delivery of DNX-2401. Patients who underwent real-time MRI-guided DNX-2401 delivery through the SmartFlow convection catheter were prospectively followed. Precise catheter placement was achieved in all patients treated, and no adverse events were noted. Average radial error from target was 0.9 mm. Average procedural time was 3 hours 16 minutes and was comparable to other convection-enhanced delivery techniques. In 2 patients, delivery of DNX-2401 was visualized as >1 cm maximal diameter of T1 hypointensity infusate on MRI obtained immediately after completion of viral infusion. These patients exhibited partial response based on Response Assessment in Neuro-Oncology assessment. The remaining patient showed <1 cm maximal diameter of infusate on immediate postinfusion MRI and showed disease progression on subsequent MRI. Our pilot case series supports compatibility of the SmartFlow system with oncolytic adenovirus delivery and provides the basis for future validation studies.