Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Reexamination Certificate
2000-07-19
2004-01-27
Chen, Shin-Lin (Department: 1632)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
C435S320100, C435S455000, C424S093200, C424S093210, C536S023500
Reexamination Certificate
active
06683058
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to methods for treatment of neurodegenerative disease and methods for delivery of therapeutic neurotrophins into the mammalian brain.
HISTORY OF THE RELATED ART
Neurotrophins play a physiological role in the development and regulation of neurons in mammals. In adults, basal forebrain cholinergic neurons, motor neurons and sensory neurons of the CNS retain responsiveness to neurotrophic factors and can regenerate after loss or damage in their presence. For this reason, neurotrophins are considered to have great promise as drugs for the treatment of neurodegenerative conditions such as Alzheimer's Disease (AD), Parkinson's Disease (PD), amyotrophic lateral sclerosis (ALS), peripheral sensory neuropathies and spinal cord injuries.
Clinical trials for the use of neurotrophins in the treatment of AD, ALS and sensory neuropathies are underway. However, the search for a protocol for delivery of neurotrophins to target tissues with minimal side effects (e.g., from diffusion to non-targeted cells or immune reaction to the delivery vehicle) and sufficient penetration of the CNS (e.g., bypassing the blood-brain barrier and achieving chronic delivery of neurotrophin to target cells) has not yet revealed a clear path for clinical administration of neurotrophins. In particular, effective delivery methods and dosing parameters have not yet been identified, although several methods have been proposed. Therefore, although the prospects for therapy of neurodegenerative disease of the brain and CNS are believed to be bright, a successful clinical protocol remains elusive.
SUMMARY OF THE INVENTION
The invention provides a clinically useful protocol for delivery of neurotrophins into the mammalian brain. The invention is particularly useful in treating neurodegenerative conditions in primates, in whom neurotrophins delivered according to the invention stimulate growth of neurons and recovery of neurological function.
More specifically, the invention consists of methods for intraparenchymal delivery of neurotrophins to defective, diseased or damaged cells in the mammalian brain. In one aspect, the invention provides a specific protocol for use in genetically modifying target cholinergic neurons (“target cells”) to produce a therapeutic neurotrophin. The genetic modification of target cells is achieved by in vivo transfection of neurons targeted for treatment, or by transfection of cells neighboring these target neurons (neurons or glia), with a recombinant expression vector for expression of the desired neurotrophin in situ.
The location for delivery of individual unit dosages of neurotrophin into the brain is selected for proximity to previously identified defective, diseased or damaged target cells in the brain. To intensify exposure of such target cells to the endogenous growth factors, each delivery site is situated no more than about 500 &mgr;m from a targeted cell and no more than about 10 mm from another delivery site. The total number of sites chosen for delivery of each unit dosage of neurotrophin will vary with the size of the region to be treated.
Optimally, for delivery of neurotrophin using a viral expression vector, each unit dosage of neurotrophin will comprise 2.5 to 25 &mgr;l of an expression vector composition, wherein the composition includes a viral expression vector in a pharmaceutically acceptable fluid (“neurotrophic composition”) and provides from 10
10
up to 10
15
NGF expressing viral particles per ml of neurotrophic composition. According to the method, neurotrophic composition is delivered to each delivery site in the brain by injection through a surgical incision, with delivery to be completed within about 5-10 minutes, depending on the volume of neurotrophic composition to be provided.
This targeted, regionally specific protocol for nervous system growth factor delivery avoids limitations imposed by diffusion of substances across the blood-brain barrier and through central nervous system (CNS) parenchyma, while avoiding potential adverse effects of neurotrophic factors delivered intact in a non-directed manner to the CNS.
DETAILED DESCRIPTION OF THE INVENTION
I. Target Tissues for Treatment of Neurodegenerative Disorders According to the Invention
The invention identifies and defines the required parameters of a method for successful regeneration of neurons in the brain with neurotrophins, especially the neurons whose loss is associated with neurodegenerative conditions with impairment of cognition such as AD.
The first method parameter defined by the invention is selection of a suitable target tissue. A region of the brain is selected for its retained responsiveness to neurotrophic factors. In humans, CNS neurons which retain responsiveness to neurotrophic factors into adulthood include the cholinergic basal forebrain neurons, the entorhinal cortical neurons, the thalamic neurons, the locus coeruleus neurons, the spinal sensory neurons and the spinal motor neurons. Abnormalities within the cholinergic compartment of this complex network of neurons have been implicated in a number of neurodegenerative disorders, including AD, Parkinson's disease, and amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease). The cholinergic basal forebrain (particularly, the Ch4 region of the basal forebrain) is a particularly suitable target tissue.
Within the primate forebrain, magnocellular neurons Ch1-Ch4 provide cholinergic innervation to the cerebral cortex, thalamus and basolateral nucleus of the amygdala. In subjects with neurodegenerative diseases such as AD, neurons in the Ch4 region (nucleus basalis of Meynert) which have nerve growth factor (NGF) receptors undergo marked atrophy as compared to normal controls (see, e.g., Kobayashi, et al., Mol. Chem. Neuropathol., 15:193-206 (1991)).
In normal subjects, neurotrophins prevent sympathetic and sensory neuronal death during development and prevents cholinergic neuronal degeneration in adult rats and primates (Tuszynski, et al., Gene Therapy, 3:305-314 (1996)). The resulting loss of functioning neurons in this region of the basal forebrain is believed to be causatively linked to the cognitive decline experienced by subjects suffering from neurodegenerative conditions such as AD (Tuszynski, et al., supra and, Lehericy, et al., J. Comp. Neurol., 330:15-31 (1993)).
In human AD, basal forebrain neuronal loss occurs over an intraparenchymal area of approximately 1 cm in diameter. To treat affected neurons over such a large region, treatment with vector composition at upwards of 10 separate in vivo gene vector delivery sites is desirable. However, in treating localized injuries to the basal forebrain, the affected areas of the brain will likely be smaller such that selection of fewer delivery sites (e.g., 5 or fewer) will be sufficient for restoration of a clinically significant number of cholinergic neurons.
Importantly, specific in vivo gene delivery sites are selected so as to cluster in an area of neuronal loss. Such areas may be identified clinically using a number of known techniques, including magnetic resonance imaging (MRI) and biopsy. In humans, non-invasive, in vivo imaging methods such as MRI will be preferred. Once areas of neuronal loss are identified, delivery sites are selected for stereotaxic distribution so each unit dosage of NGF is delivered into the brain at, or within 500 &mgr;m from, a targeted cell, and no more than about 10 mm from another delivery site.
II. Dosing Requirements and Delivery Protocol for Treatment of Neurodegenerative Disorders According to the Invention
A further parameter defined by the invention is the dosage of neurotrophin to be delivered into the target tissue. In this regard, “unit dosage” refers generally to the concentration of neurotrophin/ml of neurotrophic composition. For viral vectors, the neurotrophin concentration is defined by the number of viral particles/ml of neurotrophic composition. Optimally, for delivery of neurotrophin using a viral expression vector, each unit dosage of neurotrophin will c
Chen Shin-Lin
Regents of the University of California
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