[Show abstract][Hide abstract] ABSTRACT: One treatment approach for lysosomal storage diseases (LSDs) is the systemic infusion of recombinant enzyme. Although this enzyme replacement is therapeutic for the viscera, many LSDs have central nervous system (CNS) components that are not adequately treated by systemic enzyme infusion. Direct intracerebroventricular (ICV) infusion of a high concentration of recombinant human acid sphingomyelinase (rhASM) into the CNS over a prolonged time frame (hours) has shown therapeutic efficacy in a mouse model of Niemann-Pick A (NP/A) disease. To evaluate whether such an approach would translate to a larger brain, rhASM was infused into the lateral ventricles of both rats and Rhesus macaques, and the resulting distribution of enzyme characterized qualitatively and quantitatively. In both species, ICV infusion of rhASM resulted in parenchymal distribution of enzyme at levels that were therapeutic in the NP/A mouse model. Enzyme distribution was global in nature and exhibited a relatively steep gradient from the cerebrospinal fluid compartment to the inner parenchyma. Additional optimization of an ICV delivery approach may provide a therapeutic option for LSDs with neurologic involvement.
[Show abstract][Hide abstract] ABSTRACT: The authors have shown that convection-enhanced delivery (CED) of gadoteridol-loaded liposomes (GDLs) into different regions of normal monkey brain results in predictable, widespread distribution of this tracking agent as detected by real-time MR imaging. They also have found that this tracking technique allows monitoring of the distribution of similar nanosized agents such as therapeutic liposomes and viral vectors. A limitation of this procedure is the unexpected leakage of liposomes out of targeted parenchyma or malignancies into sulci and ventricles. The aim of the present study was to evaluate the efficacy of CED after the onset of these types of leakage.
The authors documented this phenomenon in a study of 5 nonhuman primates and 7 canines, comprising 54 CED infusion sessions. Approximately 20% of these infusions resulted in leakage into cerebral ventricles or sulci. All of the infusions and leakage events were monitored with real-time MR imaging. The authors created volume-distributed versus volume-infused graphs for each infusion session. These graphs revealed the rate of distribution of GDL over the course of each infusion and allowed the authors to evaluate the progress of CED before and after leakage.
The distribution of therapeutics within the target structure ceased to increase or resulted in significant attenuation after the onset of leakage.
An analysis of the cases in this study revealed that leakage undermines the efficacy of CED. These findings reiterate the importance of real-time MR imaging visualization during CED to ensure an accurate, robust distribution of therapeutic agents.
Journal of Neurosurgery 11/2008; 109(5):874-880. DOI:10.3171/JNS/2008/109/11/0874 · 3.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The incidence of Parkinson's disease (PD) increases greatly with age, and the baby-boomer population can expect to generate a large number of individuals with the disease, all of whom will have significantly increased medical care needs over periods of 20 years or more. This emerging healthcare burden to our society calls for accelerated efforts to understand this disease better and treat it more effectively. The growing interest in gene therapy grew out of a recognition that new medicines may be needed to combat the relentless progression of the disease in the face of conventional pharmaco-therapies and surgical interventions that have so far failed to offer more than palliative relief. The potential of gene therapy to alter dramatically the course of the disease lies very much with the challenge of converting a research tool into a medical option, a process that clearly requires a unique combination of rigor and flexibility. In this review, we examine the unique aspects of gene therapy that make its use in PD attractive, but also analyze the difficulties of employing a medicine that acts for the rest of the patient's life.