Daniel J. Asby

Convection enhanced delivery of panobinostat (LBH589)-loaded pluronic nano-micelles prolongs survival in the F98 rat glioma model

Background The pan-histone deacetylase inhibitor panobinostat is a potential therapy for malignant glioma, but it is water insoluble and does not cross the blood–brain barrier when administered systemically. In this article, we describe the in vitro and in vivo efficacy of a novel water-soluble nano-micellar formulation of panobinostat designed for administration by convection enhanced delivery (CED). Materials and methods The in vitro efficacy of panobinostat-loaded nano-micelles against rat F98, human U87-MG and M059K glioma cells and against patient-derived glioma stem cells was measured using a cell viability assay. Nano-micelle distribution in rat brain was analyzed following acute CED using rhodamine-labeled nano-micelles, and toxicity was assayed using immunofluorescent microscopy and synaptophysin enzyme-linked immunosorbent assay. We compared the survival of the bioluminescent syngenic F98/Fischer344 rat glioblastoma model treated by acute CED of panobinostat-loaded nano-micelles with that of untreated and vehicle-only-treated controls. Results Nano-micellar panobinostat is cytotoxic to rat and human glioma cells in vitro in a dose-dependent manner following short-time exposure to drug. Fluorescent rhodamine-labelled nano-micelles distribute with a volume of infusion/volume of distribution (Vi/Vd) ratio of four and five respectively after administration by CED. Administration was not associated with any toxicity when compared to controls. CED of panobinostat-loaded nano-micelles was associated with significantly improved survival when compared to controls (n=8 per group; log-rank test, P<0.001). One hundred percent of treated animals survived the 60-day experimental period and had tumour response on post-mortem histological examination. Conclusion CED of nano-micellar panobinostat represents a potential novel therapeutic option for malignant glioma and warrants translation into the clinic.

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 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.

PDTM-14. THE DISTRIBUTION, CLEARANCE AND TOXICITY OF PANOBINOSTAT ADMINISTERED TO JUVENILE RAT AND PIG BRAINSTEM BY CONVECTION ENHANCED DELIVERY

AbstractThe pan-histone deacetylase inhibitor panobinostat has preclinical efficacy against DIPG and the oral formulation has entered a phase one 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 DIPG. We investigated the toxicity, distribution and clearance of a water-soluble formulation of panobinostat in small and large animal models of CED. 30 juvenile male Wistar rats received panobinostat administered to the pons by CED at increasing concentration and were compared to animals that received vehicle alone. Clinical observation continued for two weeks. Animals were sacrificed at 72 hours or two weeks following treatment and the brains were subjected to neuropathological analysis. Axa0further 6 animals received panobinostat by CED to the striatum and were sacrificed zero, two or six hours after infusion, their brains explanted and snap-frozen. Brainstem drug concentration was determined by LC-MS/MS. Large animal toxicity was investigated using a clinically relevant MRI guided translational porcine model of CED using a drug delivery system designed for human use. 30xa0μM panobinostat was administered to the ventral pons of two juvenile Large White/Landrace-cross pigs and subject to clinical and neuropathological analysis compared to control after one or two weeks. Drug distribution was determined by LC-MS/MS in porcine white and gray matter immediately after CED. There were no clinical or neuropathological signs of toxicity up to an infused concentration of 30xa0μM in both small and large animal models. The half-life of panobinostat in rat brain after CED was 3 hours and the drug was observed to distribute in porcine white and gray matter with a volume infusion/distribution ratio of two and three respectively. CED of water-soluble panobinostat warrants investigation in children with DIPG.