Childhood Brain Tumors: A Review of Strategies to Translate CNS Drug Delivery to Clinical Trials.

Brain and spinal tumors affect 1 in 1000 people by 25 years of age, and have diverse histological, biological, anatomical and dissemination characteristics. A mortality of 30-40% means the majority are cured, although two-thirds have life-long disability, linked to accumulated brain injury that is acquired prior to diagnosis, and after surgery or chemo-radiotherapy. Only four drugs have been licensed globally for brain tumors in 40 years and only one for children. Most new cancer drugs in clinical trials do not cross the blood-brain barrier (BBB). Techniques to enhance brain tumor drug delivery are explored in this review, and cover those that augment penetration of the BBB, and those that bypass the BBB. Developing appropriate delivery techniques could improve patient outcomes by ensuring efficacious drug exposure to tumors (including those that are drug-resistant), reducing systemic toxicities and targeting leptomeningeal metastases. Together, this drug delivery strategy seeks to enhance the efficacy of new drugs and enable re-evaluation of existing drugs that might have previously failed because of inadequate delivery. A literature review of repurposed drugs is reported, and a range of preclinical brain tumor models available for translational development are explored.

Chemosensitization of Temozolomide-Resistant Pediatric Diffuse Midline Glioma Using Potent Nanoencapsulated Forms of a N(3)-Propargyl Analogue.

The lack of clinical response to the alkylating agent temozolomide (TMZ) in pediatric diffuse midline/intrinsic pontine glioma (DIPG) has been associated with O6-methylguanine-DNA-methyltransferase (MGMT) expression and mismatch repair deficiency. Hence, a potent N(3)-propargyl analogue (N3P) was derived, which not only evades MGMT but also remains effective in mismatch repair deficient cells. Due to the poor pharmacokinetic profile of N3P (t1/2 < 1 h) and to bypass the blood-brain barrier, we proposed convection enhanced delivery (CED) as a method of administration to decrease dose and systemic toxicity. Moreover, to enhance N3P solubility, stability, and sustained distribution in vivo, either it was incorporated into an apoferritin (AFt) nanocage or its sulfobutyl ether ß-cyclodextrin complex was loaded into nanoliposomes (Lip). The resultant AFt-N3P and Lip-N3P nanoparticles (NPs) had hydrodynamic diameters of 14 vs 93 nm, icosahedral vs spherical morphology, negative surface charge (-17 vs -34 mV), and encapsulating ∼630 vs ∼21000 N3P molecules per NP, respectively. Both NPs showed a sustained release profile and instant uptake within 1 h incubation in vitro. In comparison to the naked drug, N3P NPs demonstrated stronger anticancer efficacy against 2D TMZ-resistant DIPG cell cultures [IC50 = 14.6 (Lip-N3P) vs 32.8 µM (N3P); DIPG-IV) and (IC50 = 101.8 (AFt-N3P) vs 111.9 µM (N3P); DIPG-VI)]. Likewise, both N3P-NPs significantly (P < 0.01) inhibited 3D spheroid growth compared to the native N3P in MGMT+ DIPG-VI (100 µM) and mismatch repair deficient DIPG-XIX (50 µM) cultures. Interestingly, the potency of TMZ was remarkably enhanced when encapsulated in AFt NPs against DIPG-IV, -VI, and -XIX spheroid cultures. Dynamic PET scans of CED-administered zirconium-89 (89Zr)-labeled AFt-NPs in rats also demonstrated substantial enhancement over free 89Zr radionuclide in terms of localized distribution kinetics and retention within the brain parenchyma. Overall, both NP formulations of N3P represent promising approaches for treatment of TMZ-resistant DIPG and merit the next phase of preclinical evaluation.

Extended lumbar drainage in idiopathic normal pressure hydrocephalus: a systematic review and meta-analysis of diagnostic test accuracy.

BACKGROUND: When appropriately selected, a high proportion of patients with suspected idiopathic normal pressure hydrocephalus (iNPH) will respond to cerebrospinal fluid diversion with a shunt. Extended lumbar drainage (ELD) is regarded as the most accurate test for this condition, however, varying estimates of its accuracy are found in the current literature. Here, we review the literature in order to provide summary estimates of sensitivity, specificity, positive- and negative predictive value for this test through meta-analysis of suitably rigorous studies. METHODS: Studies involving a population of NPH patients with predominantly idiopathic aetiology (>80%) in which the intention of the study was to shunt patients regardless of the outcome of ELD were included in the review. Various literature databases were searched to identify diagnostic test accuracy studies addressing ELD in the diagnosis of iNPH. Those studies passing screening and eligibility were assessed using the QUADAS-2 tool and data extracted for bivariate random effects meta-analysis. RESULTS: Four small studies were identified. They showed disparate results concerning diagnostic test accuracy. The summary estimates for sensitivity and specificity were 94% (CI 41-100%) and 85% (CI 33-100%), respectively. The summary estimates of positive and negative predictive value were both 90% (CIs 65-100% and 48-100%, respectively). CONCLUSION: Large, rigorous studies addressing the diagnostic accuracy of ELD are lacking, and little robust evidence exists to support the use of ELD in diagnostic algorithms for iNPH. Therefore, a large cohort study, or ideally an RCT, is needed to determine best practice in selecting patients for shunt surgery.

Deep Brain Stimulation for Facial Pain.

Electro-modulation of subcortical deep brain structures by surgically implanted electrodes is now standard evidence-based treatment for movement disorders such as Parkinson's disease and essential tremor and is approved for dystonia and obsessive-compulsive disorder under a humanitarian exemption. Historically, deep brain stimulation (DBS) for multiple indications has demonstrated acceptable complication rates, rare mortality, and reducing morbidity as the technology and the techniques of its application have advanced. DBS for the amelioration of pain has been performed since the early 1950s, and became widely used in the 1970s, when targeting the somatosensory thalamus was shown to be efficacious for intractable pain syndromes including facial pain. The technique fell out of favour in the late 1990s after 2 multicentre trials failed to meet end-point criteria. Since these trials, DBS for pain has remained for investigational or "off-label" use. Criticisms from previous literature have involved unsuitability of patient selection, as well as inconsistencies in neurosurgical technique. Clinical success with DBS for facial pain has been for the treatment of a variety of chronic neuropathic and nociceptive pain syndromes; including trigeminal neuropathy, post-herpetic neuralgia, deafferentation facial pain, "atypical" facial pain, cluster headaches and other trigeminal autonomic cephalalgias, as well as head and neck pathologies, most often which have been resistant to all other 1st- and 2nd-line medical and surgical treatments, when DBS has become a "last treatment option." An enhanced understanding of the mechanisms of action of DBS for pain will enhance outcome, and appropriately prescribe evolving novel nuclear brain targets.

An external ventricular drainage catheter impregnated with rifampicin, trimethoprim and triclosan, with extended activity against MDR Gram-negative bacteria: an in vitro and in vivo study.

BACKGROUND: External ventricular drainage (EVD) carries a high risk of ventriculitis, increasingly caused by MDR Gram-negative bacteria such as Escherichia coli and Acinetobacter baumannii. Existing antimicrobial EVD catheters are not effective against these, and we have developed a catheter with activity against MDR bacteria and demonstrated the safety of the new formulation for use in the brain. OBJECTIVES: Our aim was to determine the ability of a newly formulated impregnated EVD catheters to withstand challenge with MDR Gram-negative bacteria and to obtain information about its safety for use in the CNS. METHODS: Catheters impregnated with three antimicrobials (rifampicin, trimethoprim and triclosan) were challenged in flow conditions at four weekly timepoints with high doses of MDR bacteria, including MRSA and Acinetobacter, and monitored for bacterial colonization. Catheter segments were also inserted intracerebrally into Wistar rats, which were monitored for clinical and behavioural change, and weight loss. Brains were removed after either 1 week or 4 weeks, and examined for evidence of inflammation and toxicity. RESULTS: Control catheters colonized quickly after the first challenge, while no colonization occurred in the impregnated catheters even after the 4 week challenge. Animals receiving the antimicrobial segments behaved normally and gained weight as expected. Neurohistochemistry revealed only surgical trauma and no evidence of neurotoxicity. CONCLUSIONS: The antimicrobial catheter appears to withstand bacterial challenge for at least 4 weeks, suggesting that it might offer protection against infection with MDR Gram-negative bacteria in patients undergoing EVD. It also appears to be safe for use in the CNS.

The distribution, clearance, and brainstem toxicity of panobinostat administered by convection-enhanced delivery.

OBJECTIVE The pan-histone deacetylase inhibitor panobinostat has preclinical efficacy against diffuse intrinsic pontine glioma (DIPG), and the oral formulation has entered a Phase I clinical trial. However, panobinostat does not cross the blood-brain barrier in humans. Convection-enhanced delivery (CED) is a novel neurosurgical drug delivery technique that bypasses the blood-brain barrier and is of considerable clinical interest in the treatment of DIPG. METHODS The authors investigated the toxicity, distribution, and clearance of a water-soluble formulation of panobinostat (MTX110) in a small- and large-animal model of CED. Juvenile male Wistar rats (n = 24) received panobinostat administered to the pons by CED at increasing concentrations and findings were compared to those in animals that received vehicle alone (n = 12). Clinical observation continued for 2 weeks. Animals were sacrificed at 72 hours or 2 weeks following treatment, and the brains were subjected to neuropathological analysis. A further 8 animals received panobinostat by CED to the striatum and were sacrificed 0, 2, 6, or 24 hours after infusion, and their brains explanted and snap-frozen. Tissue-drug concentration was determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). Large-animal toxicity was investigated using a clinically relevant MRI-guided translational porcine model of CED in which a drug delivery system designed for humans was used. Panobinostat was administered at 30 µM to the ventral pons of 2 juvenile Large White-Landrace cross pigs. The animals were subjected to clinical and neuropathological analysis, and findings were compared to those obtained in controls after either 1 or 2 weeks. Drug distribution was determined by LC-MS/MS in porcine white and gray matter immediately after CED. RESULTS There were no clinical or neuropathological signs of toxicity up to an infused concentration of 30 µM in both small- and large-animal models. The half-life of panobinostat in rat brain after CED was 2.9 hours, and the drug was observed to be distributed in porcine white and gray matter with a volume infusion/distribution ratio of 2 and 3, respectively. CONCLUSIONS CED of water-soluble panobinostat, up to a concentration of 30 µM, was not toxic and was distributed effectively in normal brain. CED of panobinostat warrants clinical investigation in patients with DIPG.

Repurposing the anti-epileptic drug sodium valproate as an adjuvant treatment for diffuse intrinsic pontine glioma.

Targeting epigenetic changes in diffuse intrinsic pontine glioma (DIPG) may provide a novel treatment option for patients. This report demonstrates that sodium valproate, a histone deacetylase inhibitor (HDACi), can increase the cytotoxicity of carboplatin in an additive and synergistic manner in DIPG cells in vitro. Sodium valproate causes a dose-dependent decrease in DIPG cell viability in three independent ex vivo cell lines. Furthermore, sodium valproate caused an increase in acetylation of histone H3. Changes in cell viability were consistent with an induction of apoptosis in DIPG cells in vitro, determined by flow cytometric analysis of Annexin V staining and assessment of apoptotic markers by western blotting. Subsequently, immunofluorescent staining of neuronal and glial markers was used to determine toxicity in normal rat hippocampal cells. Pre-treatment of cells with sodium valproate enhanced the cytotoxic effects of carboplatin, in three DIPG cell lines tested. These results demonstrate that sodium valproate causes increased histone H3 acetylation indicative of HDAC inhibition, which is inversely correlated with a reduction in cell viability. Cell viability is reduced through an induction of apoptosis in DIPG cells. Sodium valproate potentiates carboplatin cytotoxicity and prompts further work to define the mechanism responsible for the synergy between these two drugs and determine in vivo efficacy. These findings support the use of sodium valproate as an adjuvant treatment for DIPG.

The transcription factor PPARα is overexpressed and is associated with a favourable prognosis in IDH-wildtype primary glioblastoma.

AIMS: PPARα agonists are in current clinical use as hypolipidaemic agents and show significant antineoplastic effects in human glioblastoma models. To date however, the expression of PPARα in large-scale glioblastoma datasets has not been examined. We aimed to investigate the expression of the transcription factor PPARα in primary glioblastoma, the relationship between PPARα expression and patients' clinicopathological features and other molecular markers associated with gliomagenesis. METHODS AND RESULTS: With protein immunoblotting techniques and reverse transcription quantitative real-time PCR, PPARα was found to be significantly overexpressed in glioblastoma compared with control brain tissue (P = 0.032 and P = 0.005). PPARA gene expression was found to be enriched in the classical glioblastoma subtype within The Cancer Genome Atlas (TCGA) dataset. Although not associated with overall survival when assessed by immunohistochemistry, cross-validation with the TCGA dataset and multivariate analyses identified PPARA gene expression as an independent prognostic marker for overall survival (P = 0.042). Finally, hierarchical clustering revealed novel, significant associations between high PPARA expression and a putative set of glioblastoma molecular mediators including EMX2, AQP4, and NTRK2. CONCLUSIONS: PPARα is overexpressed in primary glioblastoma and high PPARA expression functions as an independent prognostic marker in the glioblastoma TCGA dataset. Further studies are required to explore genetic associations with high PPARA expression and to analyse the predictive role of PPARα expression in glioblastoma models in response to PPARα agonists.

Post-operative spinal subdural extra-arachnoid hygroma causing cauda equina compression: a report of two cases.

We present two cases of symptomatic, post-lumbar surgery cauda equina compression due to formation of a dissecting subdural extra-arachnoid cerebrospinal fluid (CSF) collection (hygroma) under tension. In both cases, a small inadvertent durotomy was sustained during the initial surgery. Surgical re-exploration confirmed a tension subdural extra-arachnoid hygroma due to one-way flow of CSF through a pinhole puncture in the arachnoid. The mechanism and clinico-radiological features of this rare post-operative complication are discussed.

Cerebellopontine angle arachnoid cyst containing ectopic choroid plexus--case report.

We present a rare and interesting case of a cerebellopontine angle cyst containing ectopic choroid plexus tissue in a 26 year-old female. Surgical resection was performed, and histological examination confirmed the presence of choroid plexus in the cyst wall. This is the first reported case of ectopic choroid plexus at the cerebellopontine angle in an adult. We present the case and review the literature.