Pathways for Drug Delivery to the Central Nervous System

Spermidine/Spermine N1-Acetyltransferase 1 (SAT1)-A Potential Gene Target for Selective Sensitization of Glioblastoma Cells Using an Ionizable Lipid Nanoparticle to Deliver siRNA

Spermidine/spermine N1-acetyltransferase 1 (SAT1) responsible for cell polyamine catabolism is overexpressed in glioblastoma multiforme (GB). Its role in tumor survival and promoting resistance towards radiation therapy has made it an interesting target for therapy. In this study, we prepared a lipid nanoparticle-based siRNA delivery system (LNP-siSAT1) to selectively knockdown (KD) SAT1 enzyme in a human glioblastoma cell line. The LNP-siSAT1 containing ionizable DODAP lipid was prepared following a microfluidics mixing method and the resulting nanoparticles had a hydrodynamic size of around 80 nm and a neutral surface charge. The LNP-siSAT1 effectively knocked down the SAT1 expression in U251, LN229, and 42MGBA GB cells, and other brain-relevant endothelial (hCMEC/D3), astrocyte (HA) and macrophage (ANA-1) cells at the mRNA and protein levels. SAT1 KD in U251 cells resulted in a 40% loss in cell viability. Furthermore, SAT1 KD in U251, LN229 and 42MGBA cells sensitized them towards radiation and chemotherapy treatments. In contrast, despite similar SAT1 KD in other brain-relevant cells no significant effect on cytotoxic response, either alone or in combination, was observed. A major roadblock for brain therapeutics is their ability to cross the highly restrictive blood-brain barrier (BBB) presented by the brain microcapillary endothelial cells. Here, we used the BBB circumventing approach to enhance the delivery of LNP-siSAT1 across a BBB cell culture model. A cadherin binding peptide (ADTC5) was used to transiently open the BBB tight junctions to promote paracellular diffusion of LNP-siSAT1. These results suggest LNP-siSAT1 may provide a safe and effective method for reducing SAT1 and sensitizing GB cells to radiation and chemotherapeutic agents.

Response to Selpercatinib in a Patient With Recurrent Glioblastoma and RET Amplification

Glioblastoma (GBM) is a malignant central nervous system neoplasm that remains largely incurable. Limited treatment options currently exist after disease progression on standard-of-care first-line therapy. However, repurposing the use of approved therapies in patients with potentially targetable genomic alterations continues to be an emerging area of interest. This report presents the first description of a patient with isocitrate dehydrogenase wild-type GBM with an underlying RET amplification who demonstrated a near-complete response while receiving therapy with the RET inhibitor selpercatinib. The case highlights the excellent blood-brain barrier penetration of selpercatinib, as well as its potential role in the management of RET-amplified GBM. Larger biomarker-enriched studies are needed to confirm the results of this case report. Given the rare incidence of RET alterations in GBM, findings from this report can help guide and support optimal treatment strategies for patients with RET-altered GBM.

Targeting Systems to the Brain Obtained by Merging Prodrugs, Nanoparticles, and Nasal Administration

About 40 years ago the lipidization of hydrophilic drugs was proposed to induce their brain targeting by transforming them into lipophilic prodrugs. Unfortunately, lipidization often transforms a hydrophilic neuroactive agent into an active efflux transporter (AET) substrate, with consequent rejection from the brain after permeation across the blood brain barrier (BBB). Currently, the prodrug approach has greatly evolved in comparison to lipidization. This review describes the evolution of the prodrug approach for brain targeting considering the design of prodrugs as active influx substrates or molecules able to inhibit or elude AETs. Moreover, the prodrug approach appears strategic in optimization of the encapsulation of neuroactive drugs in nanoparticulate systems that can be designed to induce their receptor-mediated transport (RMT) across the BBB by appropriate decorations on their surface. Nasal administration is described as a valuable alternative to obtain the brain targeting of drugs, evidencing that the prodrug approach can allow the optimization of micro or nanoparticulate nasal formulations of neuroactive agents in order to obtain this goal. Furthermore, nasal administration is also proposed for prodrugs characterized by peripheral instability but potentially able to induce their targeting inside cells of the brain.

Development of the "Hamburg Best Practice Guidelines for ICV-Enzyme Replacement therapy (ERT) in CLN2 Disease" Based on 6 Years Treatment Experience in 48 Patients

Intracerebroventricular enzyme replacement therapy (ICV-ERT) for CLN2 disease represents the first approved treatment for neuronal ceroid lipofuscinosis (NCL) diseases. It is the first treatment where a recombinant lysosomal enzyme, cerliponase alfa, is administered into the lateral cerebral ventricles to reach the central nervous system, the organ affected in CLN2 disease. If untreated, CLN2 children show first symptoms such as epilepsy and language developmental delay at 2-4 years followed by rapid loss of motor and language function, vision loss, and early death. Treatment with cerliponase alfa has shown to slow the rapid neurologic decline. However, the mode of administration by 4 hour-long intracerebroventricular infusions every 14 days represents a potentially greater risk of infection compared to intravenous enzyme replacement therapies. The Hamburg NCL Specialty Clinic was the first site worldwide to perform intracerebroventricular enzyme replacement therapy in children with CLN2 disease. In order to ensure maximum patient safety, we analysed data from our center from more than 3000 intracerebroventricular enzyme replacement therapies in 48 patients over 6 years with regard to the occurrence of device-related adverse events and device infections. Since starting intracerebroventricular enzyme replacement therapy, we have also developed and continuously improved the "Hamburg Best Practice Guidelines for ICV-Enzyme Replacement Therapy (ERT) in CLN2 Disease." Results from this study showed low rates for device-related adverse events and infections with 0.27% and 0.33%, respectively. Therefore, following our internal procedural guidelines has shown to improve standardization and patient safety of intracerebroventricular enzyme replacement therapy for CLN2 disease.