Treatment of Recurrent Glioblastoma by Chronic Convection-Enhanced Delivery of Topotecan

ABSTRACTGlioblastoma, the most common primary brain malignancy, is invariably fatal. Systemic chemotherapy is ineffective mostly because of drug delivery limitations. To overcome this, we devised an internalized pump-catheter system for direct chronic convection-enhanced delivery (CED) into peritumoral brain tissue. Topotecan (TPT) by chronic CED in 5 patients with refractory glioblastoma selectively eliminated tumor cells without toxicity to normal brain. Large, stable drug distribution volumes were non-invasively monitored with MRI of co-infused gadolinium. Analysis of multiple radiographically localized biopsies taken before and after treatment showed a decreased proliferative tumor signature resulting in a shift to a slow-cycling mesenchymal/astrocytic-like population. Tumor microenvironment analysis showed an inflammatory response and preservation of neurons. This novel drug delivery strategy and innovative clinical trial paradigm overcomes current limitations in delivery and treatment response assessment as shown here for glioblastoma and is potentially applicable for other anti-glioma agents as well as other CNS diseases.

Blood–Brain Barrier in Brain Tumors: Biology and Clinical Relevance

The presence of barriers, such as the blood–brain barrier (BBB) and brain–tumor barrier (BTB), limits the penetration of antineoplastic drugs into the brain, resulting in poor response to treatments. Many techniques have been developed to overcome the presence of these barriers, including direct injections of substances by intranasal or intrathecal routes, chemical modification of drugs or constituents of BBB, inhibition of efflux pumps, physical disruption of BBB by radiofrequency electromagnetic radiation (EMP), laser-induced thermal therapy (LITT), focused ultrasounds (FUS) combined with microbubbles and convection enhanced delivery (CED). However, most of these strategies have been tested only in preclinical models or in phase 1–2 trials, and none of them have been approved for treatment of brain tumors yet. Concerning the treatment of brain metastases, many molecules have been developed in the last years with a better penetration across BBB (new generation tyrosine kinase inhibitors like osimertinib for non-small-cell lung carcinoma and neratinib/tucatinib for breast cancer), resulting in better progression-free survival and overall survival compared to older molecules. Promising studies concerning neural stem cells, CAR-T (chimeric antigen receptors) strategies and immunotherapy with checkpoint inhibitors are ongoing.

Convection-enhanced delivery for high-grade glioma

Glioblastoma (GBM) is the most common adult primary malignant brain tumor and is associated with a dire prognosis. Despite multi-modality therapies of surgery, radiation, and chemotherapy, its 5-year survival rate is 6.8%. The presence of the blood-brain barrier (BBB) is one factor that has made GBM difficult to treat. Convection-enhanced delivery (CED) is a modality that bypasses the BBB, which allows the intracranial delivery of therapies that would not otherwise cross the BBB and avoids systemic toxicities. This review will summarize prior and ongoing studies and highlights practical considerations related to clinical care to aid providers caring for a high-grade glioma patient being treated with CED. Although not the main scope of this paper, this review also touches upon relevant technical considerations of using CED, an area still under much development.

CTIM-28. MDNA55, AN INTERLEUKIN-4 RECEPTOR TARGETED IMMUNOTHERAPY, FOR RECURRENT GBM DELIVERED BY CONVECTION ENHANCED DELIVERY (CED)

BACKGROUND MDNA55 is an IL4R-targeted toxin in development for treatment of recurrent glioblastoma (rGBM). MDNA55 binds to IL4R expressed by tumor cells and non-malignant cells of the tumor microenvironment. METHOD MDNA55-05 was an open-label, single-arm study of MDNA55 delivered by CED as a single treatment in patients with 1st or 2nd recurrence following de novo GBM, IDH wild type status and not indicated for resection at relapse. Dose volumes (up to 60mL) and concentration of MDNA55 (1.5 to 9.0 μg/mL) were studied. RESULTS MDNA55 showed an acceptable safety profile at all doses tested. Median OS (mOS) amongst all subjects was 11.9 months, OS-24 was 20%, and PFS-12 was 27%. Among subjects expressing high levels of IL4R (irrespective of MDNA55 dose) and low levels of IL4R expression administered high dose (≥ 180μg) of MDNA55 (IL4Rhi + IL4Rlo/hd), mOS further improved to 14.0 months with OS-24 of 20%. Unmethylated MGMT promoter status did not affect MDNA55 treatment outcomes. In the IL4Rhi + IL4Rlo/hd population (N=17), mOS was 14.9 months with OS-24 of 22%. Following treatment with high concentrations of MDNA55 (6.0 or 9.0 μg/mL), transient (median of 3 cycles) low dose Avastin (5mg/kg q2w or 7.5mg/kg q3w) was used for symptom control and steroid sparring. Among these subjects, mOS amongst all comers (N=9) and the IL4Rhi + IL4Rlo/hd group (N=8) increased to 21.8 and 18.6 months with OS-24 of 44% and 38%, respectively. CONCLUSIONS MDNA55 shows potential to benefit all rGBM patients treated at high dose irrespective of IL4R expression. In the 1:1 randomized Phase 3 trial, the study will enrol two-thirds of subjects in the SOC arm from a matched external control arm. Unlike conventional RCTs, the hybrid design sets a new precedent for GBM trials, allowing robust OS analysis while significantly reducing the number of subjects randomized to SOC arm.

EXTH-31. BRAIN DISTRIBUTION, CLEARANCE AND TOXICITY EVALUATION OF SMALL-MOLECULE INHIBITORS FOLLOWING CONVECTION-ENHANCED DELIVERY TO THE BRAINSTEM

BACKGROUND Diffuse midline gliomas (DMGs) harboring the H3K27M mutation are highly aggressive, fatal brainstem tumors that primarily occur in children. The blood-brain barrier (BBB) prevents numerous drugs from reaching CNS tumors, like DMG, at cytotoxic concentrations. Convection-enhanced delivery (CED) has emerged as a drug delivery technique that bypasses the BBB through a direct interstitial infusion under a pressure gradient. However, drug distribution and clearance from the brain following CED is poorly understood and has been cited as a potential reason for the lack of efficacy observed in prior clinical trials. OBJECTIVE The objective of this study was to understand how two small molecule inhibitors (alisertib, ponatinib) that inhibit cell growth and proliferation in DMG cells in vitro distribute and clear from the brain following CED to the brainstem. METHODS Sprague-dawley rats underwent a single 60mL CED infusion of drug to the brainstem (200mM alisertib, 10mM ponatinib) and were sacrificed 0.083, 1, 2, 4, 8 and 24 hours following the completion of the infusion. Brains were dissected and drug concentration was determined via HPLC analysis. RESULTS No rats showed any clinical or neurological signs of toxicity post-infusion. Both drugs showed significant differences in drug concentration based on anatomical brain region where higher concentrations were observed in the pons and cerebellum compared to the cortex. Drug half-life in the brain was ~0.5 hours for alisertib and ~1 hour for ponatinib, but this was not significantly increased following co-administration of elacridar, a BBB efflux pump inhibitor. CONCLUSIONS These results suggest that elimination of drugs from the brain in a complex, multifactorial mechanism that warrants further preclinical investigation prior to the initiation of a clinical trial.

CTNI-41. INITIAL RESULTS OF A PHASE I WINDOW OF OPPORTUNITY TRIAL EVALUATING A FIRST-IN-CLASS CD29 INHIBITOR, OS2966, IN RECURRENT HIGH-GRADE GLIOMA

BACKGROUND OS2966 is a first-in-class, humanized and deimmunized monoclonal antibody which antagonizes CD29/β1integrin, a mechanosignaling receptor prominently upregulated in glioblastoma. Preclinical studies in mice and non-human primates have demonstrated safety and encouraging efficacy. A two-part, ascending concentration, phase I clinical trial was therefore initiated to evaluate the safety and feasibility of delivering OS2966 directly to the site of disease via convection-enhanced delivery (CED) in recurrent high-grade glioma patients. METHODS This study has a 2-part design: In part 1, patients undergo stereotactic tumor biopsy followed by placement of a multiport CED catheter for delivery of OS2966 to the bulk contrast enhancing tumor. Subsequently, patients undergo a clinically-indicated tumor resection followed by placement of two CED catheters and delivery of OS2966 to the surrounding tumor-infiltrated brain. A unique concentration-based accelerated titration design is utilized for dose escalation. Given availability of pre and post infusion samples, pharmacodynamic data will be analyzed to explore mechanism of action of OS2966. RESULTS Two subjects have been treated at two corresponding dose levels (0.2mg/mL and 0.4 mg/mL). No dose-limiting toxicity or unexpected safety issues have been identified. To date, reported adverse events were mild (i.e., grade 1) and consistent with underlying disease and surgical procedures. No adverse events were attributed to OS2966 or CED catheter placement. Further, no clinically significant changes from baseline neurological exam have been noted for either patient through initial follow-up. Maximal tumor coverage and concomitant gross total resection were achieved for both patients. Tumor volume measured 1.63 cm3 and 16 cm3 for Patient 1 and 2 respectively with an intratumoral Vd/Vi ratio of 1.3. and 0.94. Pharmacodynamic analysis via tissue-level biomarkers is ongoing and will be presented. CONCLUSION Initial data demonstrates the safety and feasibility of direct intracranial delivery of OS2966.

RADT-14. TOWARDS IMAGE-GUIDED MODELING OF PATIENT-SPECIFIC RHENIUM-186 NANOLIPOSOME DISTRIBUTION VIA CONVECTION-ENHANCED DELIVERY FOR GLIOBLASTOMA MULTIFORME

Convection-enhanced delivery (CED) of Rhenium-186 nanoliposomes (RNL) is a promising approach to provide precise delivery of large, localized doses of radiation with the goal of extending overall survival for patients with recurrent GBM. A central component of successful CED, is achieving optimal catheter placement for delivery of the therapy. While surgical planning software exists for this purpose, current approaches are designed for small molecules and therefore are not appropriate for larger particles like RNL. To address this concern, we have developed a mathematical model to predict the distribution of RNL via CED on a patient-specific basis. The model is defined on the 3D brain domain which consists of 1) pressure and flow fields generated by accounting for catheter infusion, flow through brain, and fluid loss into capillaries, and 2) the transport of RNL governed by an advection-diffusion equation. We utilize pre-operative MRI to assign patient-specific tissue geometry and properties (e.g., diffusivity, conductivity), and calibrate the model with SPECT measurements within 24 h post the RNL delivery. This model is implemented on one patient enrolled in NCT01906385. The accuracy of model calibration and prediction is evaluated by the Dice score and concordance correlation coefficient (CCC) between modeled and measured distributions of RNL. Our model calibration achieves Dice scores of 0.80, 0.81, 0.69 and CCC of 0.92, 0.93, 0.73 for RNL distributions at the mid-delivery, end of delivery, and 24 h after the delivery, respectively. Long-term model prediction achieves Dice scores of 0.69 and 0.52 at 144 h and 196 h after the delivery, respectively, and CCC of 0.57 and 0.31. Preliminary results demonstrate a proof-of-concept for a patient-specific model to predict the spatiotemporally-resolved distribution of nanoparticles. Ongoing efforts focus on improving our model by accounting backflow and angle of catheter placement, and applying to more patients. Funding: NIH R01CA235800, CPRIT RR160005.

DDRE-48. COMPARTMENT LOCKED IL-12 - INCREASED TISSUE RETENTION AND MINIMAL PERIPHERAL EXPOSURE ALLOW HIGHER TREATMENT EFFICACY AND TOLERABILITY IN LOCAL GLIOBLASTOMA THERAPY

Recent clinical studies in glioblastoma (GBM) highlight the potential of local IL-12 therapy, but they also bring back tolerability concerns due to leakage into the periphery. This leakage might thus hamper exploiting the full potential of local IL-12 therapy. Fusion with an IgG4 Fc portion increases the tissue retention of IL-12; but could also confer export into the blood and subsequent systemic recycling through the neonatal Fc receptor (FcRn), ultimately leading to potentially toxic IL-12 serum levels. We assessed the expression of FcRn in human and murine GBM and its role in IL-12Fc tissue retention and systemic exposure upon local delivery. Human or murine IL-12Fc was injected in GBM-bearing or naïve wt or FcRn-humanized mice continuously or as bolus via convection-enhanced delivery (CED). We screened combinations of amino-acid substitutions at the (IL-12)Fc:FcRn binding interface to abolish this interaction. Brain and blood concentrations were assessed via ELISA or cytokine bead arrays. FcRn affinity was measured by SPR/ELISA and bioactivity tested on PBMCs and human GBM explant cultures. Treatment efficacy and immunological correlates were assessed in GBM bearing mice. FcRn is upregulated in human and mouse GBM and contributes to brain export and subsequent peripheral recycling of IL-12Fc in the blood. IL-12Fc with abrogated FcRn binding due to a unique set of substitutions is fully functional and appears brain compartment locked (CL IL-12) as it exhibits enhanced tissue retention and reduced serum levels upon local injection, reaching up 100x higher brain to serum concentration ratios than regular IL-12. Compared to its non-modified counterpart, murine CL IL-12 shows significantly higher treatment efficacy at negligible systemic footprint in late stage murine GBM. In patient explant cultures, human CL IL-12 leads to successful inflammatory conditioning. Compartment locked IL-12 should thus allow a wide dosing window to fully harness its therapeutic potential for local GBM therapy.

CTIM-18. LUMINOS-101: INITIAL SAFETY AND TOLERABILITY OF PVSRIPO AND PEMBROLIZUMAB COMBINATION THERAPY IN RECURRENT GLIOBLASTOMA

BACKGROUND Recurrent glioblastoma (rGBM) is rapidly fatal with current therapies. PVSRIPO is an intratumoral immunotherapy targeting CD155 on antigen-presenting and malignant cells of solid tumors. Preclinically, PVSRIPO treatment leads to systemic, tumor antigen-specific, polyfunctional T-cell–mediated anti-tumor response, predominately driven by type I/III interferons. This inflammatory signature generates anti-tumor immunity and upregulates the programmed death (PD)-1 immune checkpoint in the tumor microenvironment. Preclinical models (including GBM) have shown that PVSRIPO+anti-PD-1/L1 therapy was more efficacious than either agent alone, warranting further investigation. METHODS Adults with histologically confirmed rGBM (1-2 prior progressions), Karnofsky performance status (KPS) ≥70, and an active, supratentorial, contrast-enhancing lesion (1-5.5 cm), received PVSRIPO (5x107 TCID50) intratumorally via convection-enhanced delivery (Day 1), followed by 200 mg pembrolizumab IV at week 2, given every 3 weeks for up to 24 months, to evaluate the safety/efficacy of the combination. A safety lead-in period (n=3-6) with a minimum 21–28-day delay before treatment of subsequent patients was planned, with a data safety monitoring board (DSMB) evaluating safety/tolerability prior to expansion (up to N=30). RESULTS The first 3 patients enrolled (ages 55-60, KPS 90-100) all received PVSRIPO followed by pembrolizumab (1-5 cycles), as planned. At cutoff (26-106 days of follow-up), there were no dose-limiting toxicities, treatment-emergent (TE) serious adverse events (SAE), or TEAEs necessitating a delay in initial/subsequent pembrolizumab treatments. All patients experienced a related TEAE, all grade 1 or 2 in severity. One patient experienced an AE of special interest (peritumoral edema, resulting in headache and hemiparesis), successfully managed with low-dose bevacizumab and corticosteroids. The DSMB unanimously recommended the study proceed without modification. CONCLUSIONS Intratumoral PVSRIPO+pembrolizumab was reasonably well tolerated, warranting continued investigation of the safety and efficacy of this combination in patients with rGBM.

TAMI-09. INTRAOPERATIVE MICRODIALYSIS AS A FEASIBLE PLATFORM FOR METABOLIC AND PHARMACODYNAMIC BIOMARKER DISCOVERY

BACKGROUND Progress for gliomas is slowed in part by the paucity of mechanistic feedback during treatment with experimental therapies. Access to extracellular tumor pharmacodynamic biomarkers could provide an avenue to accelerate progress. We have initiated a program of intra-operative microdialysis to accelerate biomarker discovery and to identify candidate outcome measures for translational therapies. METHODS Intraoperative microdialysis was performed with M-dialysis 100kDA catheters and 107 variable rate pumps under an IDE. Four IDH-mutant and two IDH-WT lesions were studied intraoperatively with 3 divergently placed catheters. Microperfusate (artifical CSF+ 3% dextran) was perfused at 2uL/min and collected in 20 min increments. Paired CSF was also obtained when accessible. A parallel cohort of nude mice bearing human IDH-mutant, IDH-WT, or sham intracranial xenografts (n=6-12) underwent intratumoral microdialysis. A pilot murine study of intracranial drug delivery was performed via concurrent microdialysis during convection-enhanced delivery (CED) of saline or the IDH-inhibitor AG120. RESULTS Microdialysate from IDH-mutant intracranial xenografts revealed >100 differentially abundant metabolites compared to sham or IDH-WT tumors, including D2-HG (21x) and MTA(18x), p< 10^-5. The most significantly abundant metabolite was DMA (4x, p< 10^-10). 15-1000uM D2HG was recovered from intra-operative human IDH-mutant tumors and 1-2uM from normal brain adjacent to IDH-WT gliomas and < 1uM in all IDH-WT samples. Forty metabolites differentiated enhancing tumor from adjacent brain in 3/3 paired human samples including upregulated Aminoacyl-tRNA biosynthesis and downregulated purine metabolism. Serial aliquots of microdialysate during saline CED yielded steady D2-HG levels whereas CED with AG120 yielded undetectable D2-HG within 6 hours. CONCLUSION The extracellular metabolic landscape of glioma is diverse, dynamic and reflects tumor biology and response to therapy. Collectively, these studies suggest that intra-tumoral drug testing should be feasible with realistic expectation of gaining metabolic feedback within a short timeframe. Leveraging this paradigm can provide opportunities to accelerate therapeutic translation for gliomas.