Patent Publication Number: US-2018036386-A1

Title: Methods and compositions for intrathecally administered treatment of mucupolysaccharidosis type iiia

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application Ser. No. 61/734,950 filed Dec. 7, 2012 and U.S. Provisional Application Ser. No. 61/788,818 filed on Mar. 15, 2013, the disclosures of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Glycosaminoglycans, with the exception of hyaluronic acid, are the degradation products of proteoglycans that exist in the extracellular matrix. Proteoglycans enter lysosomes for intracellular digestion, thereby generating glycosaminoglycans (GAGs). 
     The mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders caused by deficiency of enzymes catalyzing the stepwise degradation of GAGs (previously called mucopolysaccharides). An inability or decreased ability to degrade GAGs results in characteristic intralysosomal accumulation in all cells and increased excretion in urine of partially degraded GAGs. As substrates accumulate, the lysosomes swell and occupy more and more of the cytoplasm, affecting cellular organelles. The accumulation of GAGs ultimately results in cell, tissue, and organ dysfunction. 
     There are at least four different pathways of lysosomal degradation of GAGs, depending on the molecule to be degraded (e.g., dermatan sulfate, heparan sulfate, keratan sulfate, or chondroitin sulfate). The stepwise degradation of GAGs requires at least 10 different enzymes: four glycosidases, five sulfatases, and one nonhydrolytic transferase. Deficiencies of each one of these enzymes have been reported and result in seven different MPSs of various subtypes, all of which share several clinical features in variable degrees. Typical symptoms include organomegaly, dysostosis multiplex, and coarse facial features. Central nervous system function, including cognitive status, hearing, and vision, as well as cardiovascular function may also be affected. Many lysosomal storage disorders affect the nervous system and thus demonstrate unique challenges in treating these diseases with traditional therapies. There is often a large build-up of glycosaminoglycans (GAGs) in neurons and meninges of affected individuals, leading to various forms of CNS symptoms. To date, no CNS symptoms resulting from a lysosomal disorder has successfully been treated by any means available. 
     One such MPS disease is Mucopolysaccharidoses IIIA (MPSIIIA), which is also known as Sanfilippo Syndrome Type A. It is an autosomal recessive disease caused by a mutation in the SGSH gene, which encodes heparan N-sulfatase. Over 70 different mutations in SGSH have been described, all of which cause enzyme defects resulting in the accumulation of heparan sulfate. MPSIIIA occurs once in about every 100,000 live births, with no ethinic predisposition noted. 
     The primary accumulation of the GAG heparan sulfate triggers a poorly understood pathological cascade, primarily affecting the central nervous system (CNS). Mechanisms of pathology include secondary accumulation of toxic metabolites, neuroinflammation, disrupted growth factor signaling and dysregulated cell death. The clinical features of MPSIIIA are overwhelmingly neurological, with developmental delays in mid- to late-infancy often being the first manifestation of disease. Severe behavior disturbances are a frequent feature of middle childhood, with progressive dementia, emotional withdrawal and developmental regression. Afflicted individuals typically do not survive past their early twenties. 
     Enzyme replacement therapy (ERT) involves the systemic administration of natural or recombinantly-derived proteins and/or enzymes to a subject. Approved therapies are typically administered to subjects intravenously and are generally effective in treating the somatic symptoms of the underlying enzyme deficiency. As a result of the limited distribution of the intravenously administered protein and/or enzyme into the cells and tissues of the central nervous system (CNS), the treatment of diseases having a CNS etiology has been especially challenging because the intravenously administered proteins and/or enzymes do not adequately cross the blood-brain barrier (BBB). 
     The blood-brain barrier (BBB) is a structural system comprised of endothelial cells that functions to protect the central nervous system (CNS) from deleterious substances in the blood stream, such as bacteria, macromolecules (e.g., proteins) and other hydrophilic molecules, by limiting the diffusion of such substances across the BBB and into the underlying cerebrospinal fluid (CSF) and CNS. 
     There are several ways of circumventing the BBB to enhance brain delivery of a therapeutic agent including direct intra-cranial injection, transient permeabilization of the BBB, and modification of the active agent to alter tissue distribution. Direct injection of a therapeutic agent into brain tissue bypasses the vasculature completely, but suffers primarily from the risk of complications (infection, tissue damage, immune responsive) incurred by intra-cranial injections and poor diffusion of the active agent from the site of administration. To date, direct administration of proteins into the brain substance has not achieved significant therapeutic effect due to diffusion barriers and the limited volume of therapeutic that can be administered. Convection-assisted diffusion has been studied via catheters placed in the brain parenchyma using slow, long-term infusions (Bobo, et al., Proc. Natl. Acad. Sci. U.S.A 91, 2076-2080 (1994); Nguyen, et al. J. Neurosurg. 98, 584-590 (2003)), but no approved therapies currently use this approach for long-term therapy. In addition, the placement of intracerebral catheters is very invasive and less desirable as a clinical alternative. 
     Intrathecal (IT) injection, or the administration of proteins to the cerebrospinal fluid (CSF), has also been attempted but has not yet yielded therapeutic success. A major challenge in this treatment has been quantifying clinical efficacy. Currently, there are no approved products for the treatment of brain genetic disease by administration directly to the CSF. 
     Thus, there remains a great need for effective and clinically quantifiable treatment of lysosomal storage diseases. More particularly, there is a great need for optimized therapeutic regimens of enzyme replace therapies capable of achieving measurable clinical efficacy. 
     SUMMARY OF THE INVENTION 
     The present invention provides improved methods for safe and effective treatment of Mucopolysaccharidoses IIIA (MPSIIIA), which is also known as Sanfilippo Syndrome Type A. The present invention is, in part, based on the phase I/II human clinical study demonstrating the safety, tolerability and efficacy in human MPSIIIA patients. 
     Thus, among other things, the present invention provides methods of treating Mucopolysaccharidosis IIIA (MPSIIIA), comprising a step of administering intrathecally to a subject in need of treatment a recombinant replacement heparan N-sulfatase (HNS) enzyme at a therapeutically effective dose and an administration interval. In some embodiments, the replacement enzyme is administered for a period sufficient to decrease glycosaminoglycan (GAG) heparan sulfate level in the cerebrospinal fluid (CSF) and/or urine relative to a control. Thus, some embodiments of the invention further comprise measuring levels of one or more glycosaminoglycans (GAGs) (e.g., heparan sulfate) in CSF, urine tissues and/or serum one or more times during the period, thereby determining a surrogate marker indicative of safety and/or therapeutic efficacy. 
     In some embodiments, levels of GAG in the CSF are measured one or more times during the treatment period. In some embodiments, levels of GAG in urine are measured one or more times during the treatment period. In some embodiments, levels of GAG in the serum are measured one or more times during treatment. In some embodiments, levels of GAG in neurons and/or meninges are measured one or more times during treatment. In some embodiments, the levels of GAG in two or more of the CSF, urine serum and neurons or meninges is measured one or more times during the treatment period. 
     In some embodiments, a method according to the present invention further includes a step of adjusting the dose and/or administration interval of the replacement enzyme based on GAG levels in CSF and/or urine, which function as surrogate markers indicative of safety and therapeutic efficacy. In some embodiments, dosages are adjusted if the GAG level in the CSF or urine fails to decrease relative to the control after 3, 4, 5, or 6 doses. 
     In some embodiments, the therapeutically effective total enzyme dose ranges from about 10 mg to about 100 mg, e.g., from about 10 mg to about 90 mg, from about 10 mg to about 75 mg, from about 10 mg to about 50 mg, from about 10 mg to about 40 mg, from about 10 mg to about 30 mg, and from about 10 mg to about 20 mg. In some embodiments, the total enzyme dose is from about 40 mg to about 50 mg. In some embodiments, the therapeutically effective dose is greater than about 10 mg per dose. In some embodiments, the therapeutically effective dose is greater than about 45 mg per dose. In some embodiments, the therapeutically effective dose is greater than about 90 mg per dose. In particular embodiments, the total enzyme dose is about 90 mg, about 45 mg or about 10 mg. In some embodiments, the total enzyme dose is administered as part of a treatment regimen. In some embodiments, the treatment regimen comprises intrathecal administration. 
     In some embodiments, a therapeutically effective total enzyme dose of a human recombinant sulfatase enzyme is administered intrathecally to a subject in need of treatment at an administration interval for a period sufficient to decrease glycosaminoglycan (GAG) heparan sulfate level in the cerebrospinal fluid (CSF) and/or urine relative to a control. In particular embodiments, a therapeutically effective total enzyme dose of human recombinant heparin N-Sulfatase (HNS) enzyme is administered intrathecally to a subject in need of treatment at an administration interval for a period sufficient to decrease glycosaminoglycan (GAG) heparan sulfate level in the cerebrospinal fluid (CSF) and/or urine relative to a control. In particular embodiments, intrathecal administration takes place at an administration interval of once every week. In particular embodiments, the intrathecal administration takes place at an administration interval of once every two weeks. In some embodiments, the intrathecal administration takes place once every month; i.e., a monthly administration interval. In some embodiments, the intrathecal administration takes place once every two months; i.e, a bimonthly administration interval. 
     In various embodiments, the present invention includes a stable formulation of any of the embodiments described herein, wherein the HNS protein comprises an amino acid sequence of SEQ ID NO:1. In some embodiments, the HNS protein comprises an amino acid sequence at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 98% identical to SEQ ID NO:1. In some embodiments, the stable formulation of any of the embodiments described herein includes a salt. In some embodiments, the salt is NaCl. In some embodiments, the NaCl is present as a concentration ranging from approximately 0-300 mM (e.g., 0-250 mM, 0-200 mM, 0-150 mM, 0-100 mM, 0-75 mM, 0-50 mM, or 0-30 mM). In some embodiments, the NaC1 is present at a concentration ranging from approximately 135-155 mM. In some embodiments, the NaCl is present at a concentration of approximately 145 mM. 
     In some embodiments, the therapeutic efficacy of the dosing regimens described herein is determined by reductions in CSF or urine GAG levels. In particular embodiments, intrathecal administration of recombinant sulfatases (e.g., the human recombinant HNS enzyme) results in the GAG level in the CSF lower than 6000 pmol/ml. In certain embodiments, the GAG level in the CSF is lower than 5000 pmol/ml. In certain embodiments, the GAG level in the CSF lower than 4000 pmol/ml. In some embodiments, intrathecal administration of recombinant sulfatases (e.g., the human recombinant HNS enzyme) results in a GAG level in urine lower than 40 μg GAG/mmol creatinine. In some embodiments, the GAG level in the urine is lower than 30 μg GAG/mmol creatinine. In certain embodiments, the GAG level in the urine is lower than 20 μg GAG/mmol creatinine. 
     In some embodiments, intrathecal administration of recombinant HNS enzyme according to the invention last for a period of at least 1 month. In some embodiments, the period is at least two months, at least three months, at least six months, at least twelve months, at least twenty-four months or more. 
     In some embodiments, intrathecal administration of recombinant HNS enzyme according to the invention results in maintain cognitive status, arrest cognitive decline or improve cognitive performance. Without wishing to be bound by any particular theory, it is thought that starting treatment before the onset of significant cognitive decline is important for measurable improvements, stabilizations or reduced declines in cognitive functions relative to controls (e.g., baseline pre-treatment assessment or measurement). For example, in patients with MPSIIIA, intrathecal enzyme replacement therapy may have to be initiated before one or more cognitive parameters has decline by more than 50%. 
     Thus, embodiments of the present invention prove, in part, methods of treating lysosomal storage diseases by intrathecal administration of human recombinant sulfatases at a therapeutically effective dose and an administration interval for a period sufficient to improve, stabilize or reduce declining of one or more cognitive functions relative to a control. In particular embodiments, the sulfatase is heparin N-Sulfatase (HNS) enzyme. In some embodiments, methods of treating lysosomal storage diseases by intrathecal administration of human recombinant sulfatases comprise administering the therapeutically effective total enzyme dosages disclosed herein (e.g., greater than 10 mg per dose, greater than 45 mg per dose, or greater than 90 mg per dose) at the administration intervals disclosed herein (e.g., monthly, once every two weeks, once every week for a period sufficient to improve, stabilize or reduce declining of one or more cognitive functions relative to a control. 
     Cognitive functions may be assessed by a variety of methods. In some embodiments, one or more cognitive functions are assessed by the Bayley Scales of Infant Development (Third Edition). In some embodiments, the one or more cognitive functions are assessed by the Kaufman Assessment Battery for Children (Second Edition). 
     In certain embodiments of the invention, the subject being treated is less than 5, 4, 3, 2 or 1 years of age. In certain embodiments of the invention, the subject is approximately 1 year to 4 years of age. In some embodiments, the subject is at least 3 years old. In certain embodiments, the subject is younger than 4 years old. In some embodiments, the subject is at least 1 year old; i.e., at least 12 months old. 
     In some embodiments, the intrathecal administration results in no substantial adverse effects (e.g., severe immune response) in the subject. In some embodiments, the intrathecal administration results in no substantial adaptive T cell-mediated immune response in the subject. In some embodiments, intrathecal administration does not require an immunosuppressant; e.g., intrathecal administration is used in absence of concurrent immunosuppressive therapy. 
     In some embodiments, the intrathecal administration is used in conjunction with intravenous administration. In some embodiments, the intravenous administration is no more frequent than once every week. In some embodiments, the intravenous administration is no more frequent than once every two weeks. In some embodiments, the intravenous administration is no more frequent than once every month. In some embodiments, the intravenous administration is no more frequent than once every two months. In certain embodiments, the intravenous administration is more frequent than monthly administration, such as twice weekly, weekly, every other week, or twice monthly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings are for illustration purposes only, not for limitation. 
         FIG. 1  illustrates the trajectories in cognitive status, expressed as developmental quotient (DQ) for individual patents with MPS IIIA over a 1 year period, without treatment. 
         FIG. 2  illustrates the trajectories in total gray matter volume among individual patents with MPS IIIA over a 1 year period, without treatment. 
         FIG. 3  illustrates the trajectories in cognitive status, expressed as developmental quotient (DQ) for individual patents with MPS IIIA over a 6 month period, during which they received one of three different enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
         FIG. 4  illustrates the trajectories in in total gray matter volume for individual patents with MPS IIIA over a 6 month period, during which they received one of three different enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
         FIG. 5  illustrates the trajectories in cognitive status, expressed as developmental quotient (DQ) for individual patents with MPS IIIA over a 1 year period with no treatment (Natural History); or for a 6 month period in which they received one of three different enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
         FIG. 6  illustrates the trajectories in total gray matter volume for individual patents with MPS IIIA over a 1 year period with no treatment (Natural History); or for a 6 month period in which they received one of three different enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
         FIG. 7  illustrates a semilogarithmic plot of serum anti-HNS antibody titer over time in 6 MPS IIIA clinical study patients exhibiting seropositivity. 
         FIG. 8  A&amp;B illustrates urine levels of glycosaminoglycan (GAG) heparan sulfate as a pharmacodynamic endpoint of enzyme replacement therapy clinical effectiveness. Mean urine heparan sulfate levels over time are shown as measured at week 2 (A) and week 22 (B) of a clinical trial determining the therapeutic efficacy of three different total enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
         FIG. 9  illustrates CSF levels of glycosaminoglycan (GAG) heparan sulfate as a pharmacodynamic endpoint of enzyme replacement therapy clinical effectiveness. Mean CSF total heparan sulfate levels over time are shown as measured at the conclusion of week 2, week 6, week 10, week 14 and week 22 of a clinical trial determining the therapeutic efficacy of three different total enzyme dosages (10 mg, 45 mg, and 90 mg) of human recombinant HNS administered intrathecally. 
     
    
    
     DEFINITIONS 
     In order for the present invention to be more readily understood, certain terms are first defined below. Additional definitions for the following terms and other terms are set forth through out the specification. 
     Approximately or about: As used herein, the term “approximately” or “about,” as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain embodiments, the term “approximately” or “about” refers to a range of values that fall within 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value). 
     Amelioration: As used herein, the term “amelioration” is meant the prevention, reduction or palliation of a state, or improvement of the state of a subject. Amelioration includes, but does not require complete recovery or complete prevention of a disease condition. In some embodiments, amelioration includes increasing levels of relevant protein or its activity that is deficient in relevant disease tissues. 
     Biologically active: As used herein, the phrase “biologically active” refers to a characteristic of any agent that has activity in a biological system, and particularly in an organism. For instance, an agent that, when administered to an organism, has a biological effect on that organism, is considered to be biologically active. In particular embodiments, where a protein or polypeptide is biologically active, a portion of that protein or polypeptide that shares at least one biological activity of the protein or polypeptide is typically referred to as a “biologically active” portion. 
     Bulking agent: As used herein, the term “bulking agent” refers to a compound which adds mass to the lyophilized mixture and contributes to the physical structure of the lyophilized cake (e.g., facilitates the production of an essentially uniform lyophilized cake which maintains an open pore structure). Exemplary bulking agents include mannitol, glycine, sodium chloride, hydroxyethyl starch, lactose, sucrose, trehalose, polyethylene glycol and dextran. 
     Cerebroanatomical Marker: The term “Cerebroanatomical Marker” as used herein refers to any anatomical feature of a brain. In some embodiments, a cerebroanatomical marker comprises, but is not limited to, any portion of the central nervous system that is enclosed within the cranium, continuous with the spinal cord and composed of gray matter and white matter. 
     Cation-independent mannose-6-phosphate receptor (CI-MPR): As used herein, the term “cation-independent mannose-6-phosphate receptor (CI-MPR)” refers to a cellular receptor that binds mannose-6-phosphate (M6P) tags on acid hydrolase precursors in the Golgi apparatus that are destined for transport to the lysosome. In addition to mannose-6-phosphates, the CI-MPR also binds other proteins including IGF-II. The CI-MPR is also known as “M6P/IGF-11 receptor,” “Cl-MPR/IGF-11 receptor,” “IGF-11 receptor” or “IGF2 Receptor.” These terms and abbreviations thereof are used interchangeably herein. 
     Concurrent immunosuppressant therapy: As used herein, the term “concurrent immunosuppressant therapy” includes any immunosuppressant therapy used as pre-treatment, preconditioning or in parallel to a treatment method. 
     Control: As used herein, the term “control” has its art-understood meaning of being a standard against which results are compared. Typically, controls are used to augment integrity in experiments by isolating variables in order to make a conclusion about such variables. In some embodiments, a control is a reaction or assay that is performed simultaneously with a test reaction or assay to provide a comparator. In one experiment, the “test” (i.e., the variable being tested) is applied. In the second experiment, the “control,” the variable being tested is not applied. In some embodiments, a control is a historical control (i.e., of a test or assay performed previously, or an amount or result that is previously known). In some embodiments, a control is or comprises a printed or otherwise saved record. A control may be a positive control or a negative control. 
     Diagnosis: As used herein, the term “diagnosis” refers to a process aimed at determining if an individual is afflicted with a disease or ailment. In the context of the present invention, “diagnosis of Sanfilippo syndrome” refers to a process aimed at one or more of: determining if an individual is afflicted with Sanfilippo syndrome, identifying a Sanfilippo syndrome subtype subtype A, B, C or D), and determining the stage of the disease (e.g., early Sanfillipo syndrome or late Sanfillipo syndrome). 
     Diluent: As used herein, the term “diluent” refers to a pharmaceutically acceptable (e.g., safe and non-toxic for administration to a human) diluting substance useful for the preparation of a reconstituted formulation. Exemplary diluents include sterile water, bacteriostatic water for injection (BWFT), a pH buffered solution (e.g. phosphate-buffered saline), sterile saline solution, Ringer&#39;s solution or dextrose solution. 
     Dosage form: As used herein, the terms “dosage form” and “unit dosage form” refer to a physically discrete unit of a therapeutic protein for the patient to be treated. Each unit contains a predetermined quantity of active material calculated to produce the desired therapeutic effect. It will be understood, however, that the total dosage of the composition will be decided by the attending physician within the scope of sound medical judgment. 
     Enzyme replacement therapy (ERT): As used herein, the term “enzyme replacement therapy (ERT)” refers to any therapeutic strategy that corrects an enzyme deficiency by providing the missing enzyme. In some embodiments, the missing enzyme is provided by intrathecal administration. In some embodiments, the missing enzyme is provided by infusing into bloodstream. Once administered, enzyme is taken up by cells and transported to the lysosome, where the enzyme acts to eliminate material that has accumulated in the lysosomes due to the enzyme deficiency. Typically, for lysosomal enzyme replacement therapy to be effective, the therapeutic enzyme is delivered to lysosomes in the appropriate cells in target tissues where the storage defect is manifest. 
     Effective amount: As used herein, the term “effective amount” refers to an amount of a compound or agent that is sufficient to fulfill its intended purpose(s). In the context of the present invention, the purpose(s) may be, for example: to modulate the expression of at least one inventive biomarker; and/or to delay or prevent the onset of Sanfilippo syndrome; and/or to slow down or stop the progression, aggravation, or deterioration of the symptoms of Sanfilippo syndrome; and/or to alleviate one or more symptoms associated with Sanfilippo syndrome; —  and/or to bring about amelioration of the symptoms of Sanfilippo syndrome, and/or to cure Sanfilippo syndrome. 
     Improve, increase, or reduce: As used herein, the terms “improve,” “increase” or “reduce,” or grammatical equivalents, indicate values that are relative to a baseline measurement, such as a measurement in the same individual prior to initiation of the treatment described herein, or a measurement in a control individual (or multiple control individuals) in the absence of the treatment described herein. A “control individual” is an individual afflicted with the same form of lysosomal storage disease as the individual being treated, who is about the same age as the individual being treated (to ensure that the stages of the disease in the treated individual and the control individual(s) are comparable). 
     Individual, subject, patient: As used herein, the terms “subject,” “individual” or “patient” refer to a human or a non-human mammalian subject. The individual (also referred to as “patient” or “subject”) being treated is an individual (fetus, infant, child, adolescent, or adult human) suffering from a disease. 
     Intrathecal administration: As used herein, the term “intrathecal administration” or “intrathecal injection” refers to an injection into the spinal canal (intrathecal space surrounding the spinal cord). Various techniques may be used including, without limitation, lateral cerebroventricular injection through a burrhole or cisternal or lumbar puncture or the like. In some embodiments, “intrathecal administration” or “intrathecal delivery” according to the present invention refers to IT administration or delivery via the lumbar area or region, i.e., lumbar IT administration or delivery. As used herein, the term “lumbar region” or “lumbar area” refers to the area between the third and fourth lumbar (lower back) vertebrae and, more inclusively, the L2-S1 region of the spine. 
     Linker: As used herein, the term “linker” refers to, in a fusion protein, an amino acid sequence other than that appearing at a particular position in the natural protein and is generally designed to be flexible or to interpose a structure, such as an a-helix, between two protein moieties. A linker is also referred to as a spacer. 
     Lyoprotectant: As used herein, the term “lyoprotectant” refers to a molecule that prevents or reduces chemical and/or physical instability of a protein or other substance upon lyophilization and subsequent storage. Exemplary lyoprotectants include sugars such as sucrose or trehalose; an amino acid such as monosodium glutamate or histidine; a methylamine such as betaine; a lyotropic salt such as magnesium sulfate: a polyol such as trihydric or higher sugar alcohols, e.g. glycerin, erythritol, glycerol, arabitol, xylitol, sorbitol, and mannitol; propylene glycol; polyethylene glycol; Pluronics; and combinations thereof. In some embodiments, a lyoprotectant is a non-reducing sugar, such as trehalose or sucrose. 
     Polypeptide: As used herein, a “polypeptide”, generally speaking, is a string of at least two amino acids attached to one another by a peptide bond. In some embodiments, a polypeptide may include at least 3-5 amino acids, each of which is attached to others by way of at least one peptide bond. Those of ordinary skill in the art will appreciate that polypeptides sometimes include “non-natural” amino acids or other entities that nonetheless are capable of integrating into a polypeptide chain, optionally. 
     Replacement enzyme: As used herein, the term “replacement enzyme” refers to any enzyme that can act to replace at least in part the deficient or missing enzyme in a disease to be treated. In some embodiments, the term “replacement enzyme” refers to any enzyme that can act to replace at least in part the deficient or missing lysosomal enzyme in a lysosomal storage disease to be treated. In some embodiments, a replacement enzyme is capable of reducing accumulated materials in mammalian lysosomes or that can rescue or ameliorate one or more lysosomal storage disease symptoms. Replacement enzymes suitable for the invention include both wild-type or modified lysosomal enzymes and can be produced using recombinant and synthetic methods or purified from nature sources. A replacement enzyme can be a recombinant, synthetic, gene-activated or natural enzyme. 
     Sample: As used herein, the term “Sample” encompasses any sample obtained from a biological source. The terms “biological sample” and “sample” arc used interchangeably. A biological sample can, by way of non-limiting example, include cerebrospinal fluid (CSF), blood, amniotic fluid, sera, urine, feces, epidermal sample, skin sample, cheek swab, sperm, amniotic fluid, cultured cells, bone marrow sample and/or chorionic villi. Convenient biological samples may be obtained by, for example, scraping cells from the surface of the buccal cavity. Cell cultures of any biological samples can also be used as biological samples, e.g., cultures of chorionic villus samples and/or amniotic fluid cultures such as amniocyte cultures. A biological sample can also be, e.g., a sample obtained from any organ or tissue (including a biopsy or autopsy specimen), can comprise cells (whether primary cells or cultured cells), medium conditioned by any cell, tissue or organ, tissue culture. In some embodiments, biological samples suitable for the invention are samples which have been processed to release or otherwise make available a nucleic acid for detection as described herein. Suitable biological samples may be obtained from a stage of life such as a fetus, young adult, adult (e.g., pregnant women), and the like. Fixed or frozen tissues also may be used. 
     Soluble: As used herein, the term “soluble” refers to the ability of a therapeutic agent to form a homogenous solution. In some embodiments, the solubility of the therapeutic agent in the solution into which it is administered and by which it is transported to the target site of action (e.g., the cells and tissues of the brain) is sufficient to permit the delivery of a therapeutically effective amount of the therapeutic agent to the targeted site of action. Several factors can impact the solubility of the therapeutic agents. For example, relevant factors which may impact protein solubility include ionic strength, amino acid sequence and the presence of other co-solubilizing agents or salts (e.g., calcium salts). In some embodiments, the pharmaceutical compositions are formulated such that calcium salts are excluded from such compositions. In some embodiments, therapeutic agents in accordance with the present invention are soluble in its corresponding pharmaceutical composition. It will be appreciated that, while isotonic solutions are generally preferred for parenterally administered drugs, the use of isotonic solutions may limit adequate solubility for some therapeutic agents and, in particular some proteins and/or enzymes. Slightly hypertonic solutions (e.g., up to 175 mM sodium chloride in 5 mM sodium phosphate at pH 7.0) and sugar-containing solutions (e.g., up to 2% sucrose in 5 mM sodium phosphate at pH 7.0) have been demonstrated to be well tolerated in monkeys. For example, the most common approved CNS bolus formulation composition is saline (150 mM NaCl in water). 
     Stability: As used herein, the term “stable” refers to the ability of the therapeutic agent (e.g., a recombinant enzyme) to maintain its therapeutic efficacy (e.g., all or the majority of its intended biological activity and/or physiochemical integrity) over extended periods of time. The stability of a therapeutic agent, and the capability of the pharmaceutical composition to maintain stability of such therapeutic agent, may be assessed over extended periods of time (e.g., for at least 1, 3, 6, 12, 18, 24, 30, 36 months or more). In general, pharmaceutical compositions described herein have been formulated such that they are capable of stabilizing, or alternatively slowing or preventing the degradation, of one or more therapeutic agents formulated therewith (e.g., recombinant proteins). In the context of a formulation a stable formulation is one in which the therapeutic agent therein essentially retains its physical and/or chemical integrity and biological activity upon storage and during processes (such as freeze/thaw, mechanical mixing and lyophilization). For protein stability, it can be measure by formation of high molecular weight (HMW) aggregates, loss of enzyme activity, generation of peptide fragments and shift of charge profiles. 
     Subject: As used herein, the term “subject” means any mammal, including humans. In certain embodiments of the present invention the subject is an adult, an adolescent or an infant. In certain embodiments of the present invention the subject is approximately 3 years to 22 years in age. In certain embodiments of the present invention the subject is less than about 10 years in age. In certain embodiments of the present invention the subject is approximately 3 years to 10 years in age. In certain embodiments of the present invention the subject approximately 10 years in age. In certain embodiments of the invention, the subject is less than 3 years of age. In certain embodiments of the invention, the subject is approximately 1 year to 3 years of age. Also contemplated by the present invention are the administration of the pharmaceutical compositions and/or performance of the methods of treatment in-utero. 
     Substantial homology: The phrase “substantial homology” is used herein to refer to a comparison between amino acid or nucleic acid sequences. As will be appreciated by those of ordinary skill in the art, two sequences are generally considered to be “substantially homologous” if they contain homologous residues in corresponding positions. Homologous residues may be identical residues. Alternatively, homologous residues may be non-identical residues will appropriately similar structural and/or functional characteristics. For example, as is well known by those of ordinary skill in the art, certain amino acids are typically classified as “hydrophobic” or “hydrophilic” amino acids., and/or as having “polar” or “non-polar” side chains Substitution of one amino acid for another of the same type may often be considered a “homologous” substitution. 
     As is well known in this art, amino acid or nucleic acid sequences may be compared using any of a variety of algorithms, including those available in commercial computer programs such as BLASTN for nucleotide sequences and BLASTP, gapped BLAST, and PSI-BLAST for amino acid sequences. Exemplary such programs are described in Altschul, et al., Basic local alignment search tool,  J. Mol. Biol.,  215(3): 403-410, 1990; Altschul, et al.,  Methods in Enzymology;  Altschul, et al., “Gapped BLAST and PSI-BLAST: a new generation of protein database search programs”,  Nucleic Acids Res.  25:3389-3402, 1997; Baxevanis, et al.,  Bioinformatics: A Practical Guide to the Analysis of Genes and Proteins,  Wiley, 1998; and Misener, et al., (eds.),  Bioinformatics Methods and Protocols  (Methods in Molecular Biology, Vol. 132), Humana Press, 1999. In addition to identifying homologous sequences, the programs mentioned above typically provide an indication of the degree of homology. In some embodiments, two sequences are considered to be substantially homologous if at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more of their corresponding residues are homologous over a relevant stretch of residues. In some embodiments, the relevant stretch is a complete sequence. In some embodiments, the relevant stretch is at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500 or more residues. 
     Substantial identity: The phrase “substantial identity” is used herein to refer to a comparison between amino acid or nucleic acid sequences. As will be appreciated by those of ordinary skill in the art, two sequences are generally considered to be “substantially identical” if they contain identical residues in corresponding positions. As is well known in this art, amino acid or nucleic acid sequences may be compared using any of a variety of algorithms, including those available in commercial computer programs such as BLASTN for nucleotide sequences and BLASTP, gapped BLAST, and PSI-BLAST for amino acid sequences. Exemplary such programs are described in Altschul, et al., Basic local alignment search tool,  J. Mol. Biol.,  215(3): 403-410, 1990; Altschul, et al.,  Methods in Enzymology;  Altschul et al.,  Nucleic Acids Res.  25:3389-3402, 1997; Baxevanis et al.,  Bioinformatics: A Practical Guide to the Analysis of Genes and Proteins,  Wiley, 1998; and Misener, et al., (eds.),  Bioinformatics Methods and Protocols  (Methods in Molecular Biology, Vol. 132), Humana Press, 1999. In addition to identifying identical sequences, the programs mentioned above typically provide an indication of the degree of identity. In some embodiments, two sequences are considered to be substantially identical if at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more of their corresponding residues are identical over a relevant stretch of residues. In some embodiments, the relevant stretch is a complete sequence. In some embodiments, the relevant stretch is at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500 or more residues. 
     Suffering from: An individual who is “suffering from” a disease, disorder, and/or condition has been diagnosed with or displays one or more symptoms of the disease, disorder, and/or condition. 
     Target tissues: As used herein , the term “target tissues” refers to any tissue that is affected by the lysosomal storage disease to be treated or any tissue in which the deficient lysosomal enzyme is normally expressed. In some embodiments, target tissues include those tissues in which there is a detectable or abnormally high amount of enzyme substrate, for example stored in the cellular lysosomes of the tissue, in patients suffering from or susceptible to the lysosomal storage disease. In some embodiments, target tissues include those tissues that display disease-associated pathology, symptom, or feature. In some embodiments, target tissues include those tissues in which the deficient lysosomal enzyme is normally expressed at an elevated level. As used herein, a target tissue may be a brain target tissue, a spinal cord target tissue and/or a peripheral target tissue. Exemplary target tissues are described in detail below. 
     Therapeutic moiety: As used herein, the term “therapeutic moiety” refers to a portion of a molecule that renders the therapeutic effect of the molecule. In some embodiments, a therapeutic moiety is a polypeptide having therapeutic activity. 
     Therapeutically effective amount: As used herein, the term “therapeutically effective amount” refers to an amount of a therapeutic protein (e.g., replacement enzyme) which confers a therapeutic effect on the treated subject, at a reasonable benefit/risk ratio applicable to any medical treatment. The therapeutic effect may be objective (i.e., measurable by some test or marker) or subjective (i.e., subject gives an indication of or feels an effect). In particular, the “therapeutically effective amount” refers to an amount of a therapeutic protein or composition effective to treat, ameliorate, or prevent a desired disease or condition, or to exhibit a detectable therapeutic or preventative effect, such as by ameliorating symptoms associated with the disease, preventing or delaying the onset or progression of the disease, and/or also lessening the severity or frequency of symptoms of the disease. A therapeutically effective amount is commonly administered in a dosing regimen that may comprise multiple unit doses. For any particular therapeutic protein, a therapeutically effective amount (and/or an appropriate unit dose within an effective dosing regimen) may vary, for example, depending on route of administration, on combination with other pharmaceutical agents. Also, the specific therapeutically effective amount (and/or unit dose) for any particular patient may depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific pharmaceutical agent employed; the specific composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and/or rate of excretion or metabolism of the specific fusion protein employed; the duration of the treatment; and like factors as is well known in the medical arts. 
     Tolerable: As used herein, the terms “tolerable” and “tolerability” refer to the ability of the pharmaceutical compositions of the present invention to not elicit an adverse reaction in the subject to whom such composition is administered, or alternatively not to elicit a serious adverse reaction in the subject to whom such composition is administered. In some embodiments, the pharmaceutical compositions of the present invention are well tolerated by the subject to whom such compositions is administered. 
     Treatment: As used herein, the term “treatment” (also “treat” or “treating”) refers to any administration of a therapeutic protein (e.g., lysosomal enzyme) that partially or completely alleviates, ameliorates, relieves, inhibits, delays onset of, reduces severity of and/or reduces incidence of one or more symptoms or features of a particular disease, disorder, and/or condition (e.g., Hunters syndrome, Sanfilippo A syndrome, Sanfilippo B syndrome). Such treatment may be of a subject who does not exhibit signs of the relevant disease, disorder and/or condition and/or of a subject who exhibits only early signs of the disease, disorder, and/or condition. Alternatively or additionally, such treatment may be of a subject who exhibits one or more established signs of the relevant disease, disorder and/or condition. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Among other things, the present invention provides methods for treating Mucopolysaccharidosis IIIA (MPSIIIA) based on intrathecal administration of recombinant replacement heparan N-sulfatase (HNS) enzyme at a therapeutically effective dose and an administration interval. In some embodiments, the replacement enzyme is administered for a period sufficient to decrease glycosaminoglycan (GAG) heparan sulfate level in the cerebrospinal fluid (CSF) and/or urine relative to a control. 
     Various aspects of the invention are described in detail in the following sections. The use of sections is not meant to limit the invention. Each section can apply to any aspect of the invention. In this application, the use of “or” means “and/or” unless stated otherwise. 
     Recombinant Heparan-N-Sulfatase (HNS) Enzymes 
     A suitable HNS protein for the present invention can be any molecule or a portion of a molecule that can substitute for naturally-occurring Heparan-N-Sulfatase (HNS) protein activity or rescue one or more phenotypes or symptoms associated with HNS-deficiency. In some embodiments, a replacement enzyme suitable for the invention is a polypeptide having an N-terminus and a C-terminus and an amino acid sequence substantially similar or identical to mature human HNS protein. 
     Typically, human HNS is produced as a precursor molecule that is processed to a mature form. This process generally occurs by removing the 20 amino acid signal peptide. Typically, the precursor form is also referred to as full-length precursor or full-length HNS protein, which contains 502 amino acids. The N-terminal 20 amino acids are cleaved, resulting in a mature form that is 482 amino acids in length. Thus, it is contemplated that the N-terminal 20 amino acids is generally not required for the HNS protein activity. The amino acid sequences of the mature form (SEQ ID NO:1) and full-length precursor (SEQ ID NO:2) of a typical wild-type or naturally-occurring human HNS protein are shown in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Human 
                 Iduronate-2-sulfatase 
               
               
                   
               
             
            
               
                 Mature Form 
                 RPRNALLLLADDGGFESGAYNNSAIATPHLDALARRSLLFRNAFTSVSSCSPSR 
               
               
                   
                 ASLLTGLPQHQNGMYGLHQDVHHFNSFDKVRSLPLLLSQAGVRTGIIGKKHVGP 
               
               
                   
                 ETVYPFDFAYTEENGSVLQVGRNITRIKLLVRKFLQTQDDRPFFLYVAFHDPHR 
               
               
                   
                 CGHSQPQYGTFCEKFGNGESGMGRIPDWTPQAYDPLDVLVPYFVPNTPAARADL 
               
               
                   
                 AAQYTTVGRMDQGVGLVLQELRDAGVLNDTLVIFTSDNGIPFPSGRTNLYWPGT 
               
               
                   
                 AEPLLVSSPEHPKRWGQVSEAYVSLLDLTPTILDWFSIPYPSYAIFGSKTIHLT 
               
               
                   
                 GRSLLPALEAEPLWATVFGSQSHHEVTMSYPMRSVQHRHFRLVHNLNFKMPFPI 
               
               
                   
                 DQDFYVSPTFQDLLNRTTAGQPTGWYKDLRHYYYRARWELYDRSRDPHETQNLA 
               
               
                   
                 TDPRFAQLLEMLRDQLAKWQWETHDPWVCAPDGVLEEKLSP000PLHNEL 
               
               
                   
                 (SEQ ID NO: 1) 
               
               
                   
               
               
                 Full-Length 
                 MSCPVPACCALLLVLGLCRARPRNALLLLADDGGFESGAYNNSAIATPHLDA 
               
               
                 Precursor 
                 LARRSLLFRNAFTSVSSCSPSRASLLTGLPQHQNGMYGLHQDVHHFNSFDKVRS 
               
               
                   
                 LPLLLSQAGVRTGIIGKKHVGPETVYPFDFAYTEENGSVLQVGRNITRIKLLVR 
               
               
                   
                 KFLQTQDDRPFFLYVAFHDPHRCGHSQPQYGTFCEKFGNGESGMGRIPDWTPQA 
               
               
                   
                 YDPLDVLVPYFVPNTPAARADLAAQYTTVGRMDQGVGLVLQELRDAGVLNDTLV 
               
               
                   
                 IFTSDNGIPFPSGRTNLYWPGTAEPLLVSSPEHPKRWGQVSEAYVSLLDLTPTI 
               
               
                   
                 LDWFSIPYPSYAIFGSKTIHLTGRSLLPALEAEPLWATVFGSQSHHEVTMSYPM 
               
               
                   
                 RSVQHRHFRLVHNLNFKMPFPIDQDFYVSPTFQDLLNRTTAGQPTGWYKDLRHY 
               
               
                   
                 YYRARWELYDRSRDPHETQNLATDPRFAQLLEMLRDQLAKWQWETHDPWVCAPD 
               
               
                   
                 GVLEEKLSPQCQPLHNEL (SEQ ID NO: 2) 
               
               
                   
               
            
           
         
       
     
     Thus, in some embodiments, a therapeutic moiety suitable for the present invention is mature human HNS protein (SEQ ID NO:1). In some embodiments, a suitable therapeutic moiety may be a homologue or an analogue of mature human HNS protein. For example, a homologue or an analogue of mature human HNS protein may be a modified mature human HNS protein containing one or more amino acid substitutions, deletions, and/or insertions as compared to a wild-type or naturally-occurring HNS protein (e.g., SEQ TD NO:1), while retaining substantial HNS protein activity. Thus, in some embodiments, a therapeutic moiety suitable for the present invention is substantially homologous to mature human HNS protein (SEQ ID NO:1). In some embodiments, a therapeutic moiety suitable for the present invention has an amino acid sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more homologous to SEQ ID NO:1. In some embodiments, a therapeutic moiety suitable for the present invention is substantially identical to mature human HNS protein (SEQ ID NO:1). In some embodiments, a therapeutic moiety suitable for the present invention has an amino acid sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more identical to SEQ ID NO:1. In some embodiments, a therapeutic moiety suitable for the present invention contains a fragment or a portion of mature human HNS protein. 
     Alternatively, a therapeutic moiety suitable for the present invention is full-length HNS protein. In some embodiments, a suitable therapeutic moiety may be a homologue or an analogue of full-length human HNS protein. For example, a homologue or an analogue of full-length human HNS protein may be a modified full-length human HNS protein containing one or more amino acid substitutions, deletions, and/or insertions as compared to a wild-type or naturally-occurring full-length HNS protein (e.g., SEQ ID NO:2), while retaining substantial HNS protein activity. Thus, In some embodiments, a therapeutic moiety suitable for the present invention is substantially homologous to full-length human HNS protein (SEQ ID NO:2). In some embodiments, a therapeutic moiety suitable for the present invention has an amino acid sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more homologous to SEQ ID NO:2. In some embodiments, a therapeutic moiety suitable for the present invention is substantially identical to SEQ ID NO:2. In some embodiments, a therapeutic moiety suitable for the present invention has an amino acid sequence at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more identical to SEQ ID NO:2. In some embodiments, a therapeutic moiety suitable for the present invention contains a fragment or a portion of full-length human HNS protein. As used herein, a full-length HNS protein typically contains signal peptide sequence. 
     A replacement enzyme suitable for the present invention may be produced by any available means. For example, replacement enzymes may be recombinantly produced by utilizing a host cell system engineered to express a replacement enzyme-encoding nucleic acid. Alternatively or additionally, replacement enzymes may be produced by activating endogenous genes. Alternatively or additionally, replacement enzymes may be partially or fully prepared by chemical synthesis. Alternatively or additionally, replacements enzymes may also be purified from natural sources. 
     Where enzymes are recombinantly produced, any expression system can be used. To give but a few examples, known expression systems include, for example, egg, baculovirus, plant, yeast, or mammalian cells. 
     In some embodiments, enzymes suitable for the present invention are produced in mammalian cells. Non-limiting examples of mammalian cells that may be used in accordance with the present invention include BALB/c mouse myeloma line (NSO/I, ECACC No: 85110503); human retinoblasts (PER.C6, CruCell, Leiden, The Netherlands); monkey kidney CV1 line transformed by SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line (293 or 293 cells subcloned for growth in suspension culture, Graham et al., J. Gen Virol., 36:59,1977); human fibrosarcoma cell line (e.g., HT1080); baby hamster kidney cells (BHK, ATCC CCL 10); Chinese hamster ovary cells +/−DHFR (CHO, Urlaub and Chasin, Proc. Natl. Acad. Sci. USA, 77:4216, 1980); mouse sertoli cells (TM4, Mather, Biol. Reprod., 23:243-251, 1980); monkey kidney cells (CV1 ATCC CCL 70); African green monkey kidney cells (VERO-76, ATCC CRL-1 587); human cervical carcinoma cells (HeLa, ATCC CCL 2); canine kidney cells (MDCK, ATCC CCL 34); buffalo rat liver cells (BRL 3A, ATCC CRL 1442); human lung cells (W138, ATCC CCL 75); human liver cells (Hep G2, HB 8065); mouse mammary tumor (MMT 060562, ATCC CCL51); TRI cells (Mather et al., Annals N.Y. Acad. Sci., 383:44-68, 1982); MRC 5 cells; FS4 cells; and a human hepatoma line (Hep G2). 
     In some embodiments, inventive methods according to the present invention are used to deliver replacement enzymes produced from human cells. In some embodiments, inventive methods according to the present invention are used to deliver replacement enzymes produced from CHO cells. 
     In some embodiments, replacement enzymes delivered using a method of the invention contain a moiety that binds to a receptor on the surface of brain cells to facilitate cellular uptake and/or lysosomal targeting. For example, such a receptor may be the cation-independent mannose-6-phosphate receptor (CI-MPR) which binds the mannose-6-phosphate (M6P) residues. In addition, the CI-MPR also binds other proteins including IGF-II. In some embodiments, a replacement enzyme suitable for the present invention contains M6P residues on the surface of the protein. In some embodiments, a replacement enzyme suitable for the present invention may contain bis-phosphorylated oligosaccharides which have higher binding affinity to the CI-MPR. In some embodiments, a suitable enzyme contains up to about an average of about at least 20% bis-phosphorylated oligosaccharides per enzyme. In other embodiments, a suitable enzyme may contain about 10%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% bis-phosphorylated oligosaccharides per enzyme. While such bis-phosphorylated oligosaccharides may be naturally present on the enzyme, it should be noted that the enzymes may be modified to possess such oligosaccharides. For example, suitable replacement enzymes may be modified by certain enzymes which are capable of catalyzing the transfer of N-acetylglucosamine-L-phosphate from UDP-GlcNAc to the 6′ position of α-1,2-linked mannoses on lysosomal enzymes. Methods and compositions for producing and using such enzymes are described by, for example, Canfield et al. in U.S. Pat. No. 6,537,785, and U.S. Pat. No. 6,534,300, each incorporated herein by reference. 
     In some embodiments, replacement enzymes for use in the present invention may be conjugated or fused to a lysosomal targeting moiety that is capable of binding to a receptor on the surface of brain cells. A suitable lysosomal targeting moiety can be IGF-I, IGF-II, RAP, p97, and variants, homologues or fragments thereof (e.g., including those peptide having a sequence at least 70%, 75%, 80%, 85%, 90%, or 95% identical to a wild-type mature human IGF-I, IGF-II, RAP, p97 peptide sequence). 
     In some embodiments, replacement enzymes suitable for the present invention have not been modified to enhance delivery or transport of such agents across the BBB and into the CNS. 
     In some embodiments, a therapeutic protein includes a targeting moiety (e.g., a lysosome targeting sequence) and/or a membrane-penetrating peptide. In some embodiments, a targeting sequence and/or a membrane-penetrating peptide is an intrinsic part of the therapeutic moiety (e.g., via a chemical linkage, via a fusion protein). In some embodiments, a targeting sequence contains a mannose-6-phosphate moiety. In some embodiments, a targeting sequence contains an IGF-I moiety. In some embodiments, a targeting sequence contains an IGF-II moiety. 
     Formulations 
     In some embodiments, desired enzymes are delivered in stable formulations for intrathecal delivery. Certain embodiments of the invention are based, at least in part, on the discovery that various formulations disclosed herein facilitate the effective delivery and distribution of one or more therapeutic agents (e.g., an HNS enzyme) to targeted tissues, cells and/or organelles of the CNS. Among other things, formulations described herein are capable of solubilizing high concentrations of therapeutic agents (e.g., an HNS enzyme) and are suitable for the delivery of such therapeutic agents to the CNS of subjects for the treatment of diseases having a CNS component and/or etiology (e.g., Sanfilippo A Syndrome). The compositions described herein are further characterized by improved stability and improved tolerability when administered to the CNS of a subject (e.g., intrathecally) in need thereof. 
     In some embodiments, formulations for CNS delivery have been formulated such that they are capable of stabilizing, or alternatively slowing or preventing the degradation, of a therapeutic agent formulated therewith (e.g., an HNS enzyme). As used herein, the term “stable” refers to the ability of the therapeutic agent (e.g., an HNS enzyme) to maintain its therapeutic efficacy (e.g., all or the majority of its intended biological activity and/or physiochemical integrity) over extended periods of time. The stability of a therapeutic agent, and the capability of the pharmaceutical composition to maintain stability of such therapeutic agent, may be assessed over extended periods of time (e.g., preferably for at least 1, 3, 6, 12, 18, 24, 30, 36 months or more). In the context of a formulation a stable formulation is one in which the therapeutic agent therein essentially retains its physical and/or chemical integrity and biological activity upon storage and during processes (such as freeze/thaw, mechanical mixing and lyophilization). For protein stability, it can be measure by formation of high molecular weight (HMW) aggregates, loss of enzyme activity, generation of peptide fragments and shift of charge profiles. 
     Stability of the therapeutic agent is of particular importance. Stability of the therapeutic agent may be further assessed relative to the biological activity or physiochemical integrity of the therapeutic agent over extended periods of time. For example, stability at a given time point may be compared against stability at an earlier time point (e.g., upon formulation day 0) or against unformulated therapeutic agent and the results of this comparison expressed as a percentage. Preferably, the pharmaceutical compositions of the present invention maintain at least 100%, at least 99%, at least 98%, at least 97% at least 95%, at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, at least 55% or at least 50% of the therapeutic agent&#39;s biological activity or physiochemical integrity over an extended period of time (e.g., as measured over at least about 6-12 months, at room temperature or under accelerated storage conditions). 
     In some embodiments, therapeutic agents (e.g., desired enzymes) are soluble in formulations of the present invention. The term “soluble” as it relates to the therapeutic agents of the present invention refer to the ability of such therapeutic agents to form a homogenous solution. Preferably the solubility of the therapeutic agent in the solution into which it is administered and by which it is transported to the target site of action (e.g., the cells and tissues of the brain) is sufficient to permit the delivery of a therapeutically effective amount of the therapeutic agent to the targeted site of action. Several factors can impact the solubility of the therapeutic agents. For example, relevant factors which may impact protein solubility include ionic strength, amino acid sequence and the presence of other co-solubilizing agents or salts (e.g., calcium salts.) In some embodiments, the pharmaceutical compositions are formulated such that calcium salts are excluded from such compositions. 
     Suitable formulations, in either aqueous, pre-lyophilized, lyophilized or reconstituted form, may contain a therapeutic agent of interest at various concentrations. In some embodiments, formulations may contain a protein or therapeutic agent of interest at a concentration in the range of about 0.1 mg/ml to 100 mg/ml (e.g., about 0.1 mg/ml to 80 mg/ml, about 0.1 mg/ml to 60 mg/ml, about 0.1 mg/ml to 50 mg/ml, about 0.1 mg/ml to 40 mg/ml, about 0.1 mg/ml to 30 mg/ml, about 0.1 mg/ml to 25 mg/ml, about 0.1 mg/ml to 20 mg/ml, about 0.1 mg/ml to 60 mg/ml, about 0.1 mg/ml to 50 mg/ml, about 0.1 mg/ml to 40 mg/ml, about 0.1 mg/ml to 30 mg/ml, about 0.1 mg/ml to 25 mg/ml, about 0.1 mg/ml to 20 mg/ml, about 0.1 mg/ml to 15 mg/ml, about 0.1 mg/ml to 10 mg/ml, about 0.1 mg/ml to 5 mg/ml, about 1 mg/ml to 10 mg/ml, about 1 mg/ml to 20 mg/ml, about 1 mg/ml to 40 mg/ml, about 5 mg/ml to 100 mg/ml, about 5 mg/ml to 50 mg/ml, or about 5 mg/ml to 25 mg/ml). In some embodiments, formulations according to the invention may contain a therapeutic agent at a concentration of approximately 1 mg/ml, 5 mg/ml, 10 mg/ml, 11 mg/ml, 12 mg/ml, 13 mg/ml, 14 mg/ml, 15 mg/ml, 16 mg/ml, 17 mg/ml, 18 mg/ml, 19 mg/ml, 20 mg/ml, 25 mg/ml, 30 mg/ml, 40 mg/ml, 50 mg/ml, 60 mg/ml, 70 mg/ml, 80 mg/ml, 90 mg/ml, or 100 mg/ml. 
     The formulations of the present invention are characterized by their tolerability either as aqueous solutions or as reconstituted lyophilized solutions. As used herein, the terms “tolerable” and “tolerability” refer to the ability of the pharmaceutical compositions of the present invention to not elicit an adverse reaction in the subject to whom such composition is administered, or alternatively not to elicit a serious adverse reaction in the subject to whom such composition is administered. In some embodiments, the pharmaceutical compositions of the present invention are well tolerated by the subject to whom such compositions is administered. 
     Many therapeutic agents, and in particular the proteins and enzymes of the present invention, require controlled pH and specific excipients to maintain their solubility and stability in the pharmaceutical compositions of the present invention. Table 2 below identifies typical exemplary aspects of protein formulations considered to maintain the solubility and stability of the protein therapeutic agents of the present invention. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Exemplary pH and excipients 
               
            
           
           
               
               
               
            
               
                 Parameter 
                 Typical Range/Type 
                 Rationale 
               
               
                   
               
               
                 pH 
                 4 to 8.0 
                 For stability 
               
               
                   
                   
                 Sometimes also for solubility 
               
               
                 Buffer type 
                 acetate, succinate, citrate, 
                 To maintain optimal pH 
               
               
                   
                 histidine, phosphate or 
                 May also affect stability 
               
               
                   
                 Tris 
               
               
                 Buffer 
                 5-50 mM 
                 To maintain pH 
               
               
                 concentration 
                   
                 May also stabilize or 
               
               
                   
                   
                 add ionic strength 
               
               
                 Tonicifier 
                 NaCl, sugars, mannitol 
                 To render iso- 
               
               
                   
                   
                 osmotic or 
               
               
                   
                   
                 isotonic solutions 
               
               
                 Surfactant 
                 Polysorbate 20, 
                 To stabilize against 
               
               
                   
                 polysorbate 80 
                 interfaces and shear 
               
               
                 Other 
                 Amino acids (e.g. 
                 For enhanced solubility 
               
               
                   
                 arginine) at tens to 
                 or stability 
               
               
                   
                 hundreds of mM 
               
               
                   
               
            
           
         
       
     
     Buffers 
     The pH of the formulation is an additional factor which is capable of altering the solubility of a therapeutic agent (e.g., an enzyme or protein) in an aqueous formulation or for a pre-lyophilization formulation. Accordingly the formulations of the present invention preferably comprise one or more buffers. In some embodiments the aqueous formulations comprise an amount of buffer sufficient to maintain the optimal pH of said composition between about 4.0-8.0 (e.g., about 4.0, 4.5, 5.0, 5.5, 6.0, 6.2, 6.4, 6.5, 6.6, 6.8, 7.0, 7.5, or 8.0). In some embodiments, the pH of the formulation is between about 5.0-7.5, between about 5.5-7.0, between about 6.0-7.0, between about 5.5-6.0, between about 5.5-6.5, between about 5.0-6.0, between about 5.0-6.5 and between about 6.0-7.5. Suitable buffers include, for example acetate, citrate, histidine, phosphate, succinate, tris(hydroxymethyl)aminomethane (“Tris”) and other organic acids. The buffer concentration and pH range of the pharmaceutical compositions of the present invention are factors in controlling or adjusting the tolerability of the formulation. In some embodiments, a buffering agent is present at a concentration ranging between about 1 mM to about 150 mM, or between about 10 mM to about 50 mM, or between about 15 mM to about 50 mM, or between about 20 mM to about 50 mM, or between about 25 mM to about 50 mM. In some embodiments, a suitable buffering agent is present at a concentration of approximately 1 mM, 5 mM, 10 mM, 15 mM, 20 mM, 25 mM, 30 mM, 35 mM, 40 mM, 45 mM 50 mM, 75 mM, 100 mM, 125 mM or 150 mM. 
     Tonicity 
     In some embodiments, formulations, in either aqueous, pre-lyophilized, lyophilized or reconstituted form, contain an isotonicity agent to keep the formulations isotonic. Typically, by “isotonic” is meant that the formulation of interest has essentially the same osmotic pressure as human blood. Isotonic formulations will generally have an osmotic pressure from about 240 mOsm/kg to about 350 mOsm/kg. Isotonicity can be measured using, for example, a vapor pressure or freezing point type osmometers. Exemplary isotonicity agents include, but are not limited to, glycine, sorbitol, mannitol, sodium chloride and arginine. In some embodiments, suitable isotonic agents may be present in aqueous and/or pre-lyophilized formulations at a concentration from about 0.01-5% (e.g., 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1.0, 1.25, 1.5, 2.0, 2.5, 3.0, 4.0 or 5.0%) by weight. In some embodiments, formulations for lyophilization contain an isotonicity agent to keep the pre-lyophilization formulations or the reconstituted formulations isotonic. 
     While generally isotonic solutions are preferred for parenterally administered drugs, the use of isotonic solutions may change solubility for some therapeutic agents and in particular some proteins and/or enzymes. Slightly hypertonic solutions (e.g., up to 175 mM sodium chloride in 5 mM sodium phosphate at pH 7.0) and sugar-containing solutions (e.g., up to 2% sucrose in 5 mM sodium phosphate at pH 7.0) have been demonstrated to be well tolerated. The most common approved CNS bolus formulation composition is saline (about 150 mM NaCl in water). 
     Stabilizing Agents 
     In some embodiments, formulations may contain a stabilizing agent, or lyoprotectant, to protect the protein. Typically, a suitable stabilizing agent is a sugar, a non-reducing sugar and/or an amino acid. Exemplary sugars include, but are not limited to, dextran, lactose, mannitol, mannose, sorbitol, raffinose, sucrose and trehalose. Exemplary amino acids include, but are not limited to, arginine, glycine and methionine. Additional stabilizing agents may include sodium chloride, hydroxyethyl starch and polyvinylpyrolidone. The amount of stabilizing agent in the lyophilized formulation is generally such that the formulation will be isotonic. However, hypertonic reconstituted formulations may also be suitable. In addition, the amount of stabilizing agent must not be too low such that an unacceptable amount of degradation/aggregation of the therapeutic agent occurs. Exemplary stabilizing agent concentrations in the formulation may range from about 1 mM to about 400 mM (e.g., from about 30 mM to about 300 mM, and from about 50 mM to about 100 mM), or alternatively, from 0.1% to 15% (e.g., from 1% to 10%, from 5% to 15%, from 5% to 10%) by weight. In some embodiments, the ratio of the mass amount of the stabilizing agent and the therapeutic agent is about 1:1. In other embodiments, the ratio of the mass amount of the stabilizing agent and the therapeutic agent can be about 0.1:1, 0.2:1, 0.25:1, 0.4:1, 0.5:1, 1:1, 2:1, 2.6:1, 3:1, 4:1, 5:1, 10;1, or 20:1. In some embodiments, suitable for lyophilization, the stabilizing agent is also a lyoprotectant. 
     In some embodiments, liquid formulations suitable for the present invention contain amorphous materials. In some embodiments, liquid formulations suitable for the present invention contain a substantial amount of amorphous materials (e.g., sucrose-based formulations). In some embodiments, liquid formulations suitable for the present invention contain partly crystalline/partly amorphous materials. 
     Bulking Agents 
     In some embodiments, suitable formulations for lyophilization may further include one or more bulking agents. A “bulking agent” is a compound which adds mass to the lyophilized mixture and contributes to the physical structure of the lyophilized cake. For example, a bulking agent may improve the appearance of lyophilized cake (e.g., essentially uniform lyophilized cake). Suitable bulking agents include, but are not limited to, sodium chloride, lactose, mannitol, glycine, sucrose, trehalose, hydroxyethyl starch. Exemplary concentrations of bulking agents are from about 1% to about 10% (e.g., 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, and 10.0%). 
     Surfactants 
     In some embodiments, it is desirable to add a surfactant to formulations. Exemplary surfactants include nonionic surfactants such as Polysorbates (e.g., Polysorbates 20 or 80); poloxamcrs (e.g., poloxamer 188); Triton; sodium dodecyl sulfate (SDS); sodium laurel sulfate; sodium octyl glycoside; lauryl-, myristyl-, linoleyl-, or stearyl-sulfobetaine; lauryl-, myristyl-, linoleyl- or stearyl-sarcosine; linoleyl-, myristyl-, or cetyl-betaine; lauroamidopropyl-, cocamidopropyl-, linoleamidopropyl-, myristamidopropyl-, palmidopropyl-, or isostearamidopropyl-betaine (e.g., lauroamidopropyl); myristarnidopropyl-, palmidopropyl-, or isostearamidopropyl-dimethylamine; sodium methyl cocoyl-, or disodium methyl ofeyl-taurate; and the MONAQUAT™ series (Mona Industries, Inc., Paterson, N.J.), polyethyl glycol, polypropyl glycol, and copolymers of ethylene and propylene glycol (e.g., Pluronics, PF68, etc). Typically, the amount of surfactant added is such that it reduces aggregation of the protein and minimizes the formation of particulates or effervescences. For example, a surfactant may be present in a formulation at a concentration from about 0.001-0.5% (e.g., about 0.001-0.4%, 0.001-0.3%, 0.001-0.2%, 0.001-0.1%, 0.001-0.05%, 0.001-0.04%, 0.001-0.03%, 0.001-0.02%, 0.001-0.01%, 0.002-0.05%, 0.003-0.05%, 0.004-0.05%, 0.005-0.05%, or 0.005-0.01%). In particular, a surfactant may be present in a formulation at a concentration of approximately 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or 0.5%, etc. Alternatively, or in addition, the surfactant may be added to the lyophilized formulation, pre-lyophilized formulation and/or the reconstituted formulation. 
     Other pharmaceutically acceptable carriers, excipients or stabilizers such as those described in Remington&#39;s Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980) may be included in the formulation (and/or the lyophilized formulation and/or the reconstituted formulation) provided that they do not adversely affect the desired characteristics of the formulation. Acceptable carriers, excipients or stabilizers are nontoxic to recipients at the dosages and concentrations employed and include, but are not limited to, additional buffering agents; preservatives; co-solvents; antioxidants including ascorbic acid and methionine; chelating agents such as EDTA; metal complexes (e.g., Zn-protein complexes); biodegradable polymers such as polyesters; and/or salt-forming counterions such as sodium. 
     Formulations, in either aqueous, pre-lyophilized, lyophilized or reconstituted form, in accordance with the present invention can be assessed based on product quality analysis, reconstitution time (if lyophilized), quality of reconstitution (if lyophilized), high molecular weight, moisture, and glass transition temperature. Typically, protein quality and product analysis include product degradation rate analysis using methods including, but not limited to, size exclusion HPLC (SE-HPLC), cation exchange-HPLC (CEX-HPLC), X-ray diffraction (XRD), modulated differential scanning calorimetry (mDSC), reversed phase HPLC (RP-HPLC), multi-angle light scattering (MALS), fluorescence, ultraviolet absorption, nephelometry, capillary electrophoresis (CE), SDS-PAGE, and combinations thereof. In some embodiments, evaluation of product in accordance with the present invention may include a step of evaluating appearance (either liquid or cake appearance). 
     Generally, formulations (lyophilized or aqueous) can be stored for extended periods of time at room temperature. Storage temperature may typically range from 0° C. to 45° C. (e.g., 4° C., 20° C., 25° C., 45° C. etc.). Formulations may be stored for a period of months to a period of years. Storage time generally will be 24 months, 12 months, 6 months, 4.5 months, 3 months, 2 months or 1 month. Formulations can be stored directly in the container used for administration, eliminating transfer steps. 
     Formulations can be stored directly in the lyophilization container (if lyophilized), which may also function as the reconstitution vessel, eliminating transfer steps. Alternatively, lyophilized product formulations may be measured into smaller increments for storage. Storage should generally avoid circumstances that lead to degradation of the proteins, including but not limited to exposure to sunlight, UV radiation, other forms of electromagnetic radiation, excessive heat or cold, rapid thermal shock, and mechanical shock. 
     Lyophilization 
     Inventive methods in accordance with the present invention can be utilized to lyophilize any materials, in particular, therapeutic agents. Typically, a pre-lyophilization formulation further contains an appropriate choice of excipients or other components such as stabilizers, buffering agents, bulking agents, and surfactants to prevent compound of interest from degradation (e.g., protein aggregation, deamidation, and/or oxidation) during freeze-drying and storage. The formulation for lyophilization can include one or more additional ingredients including lyoprotectants or stabilizing agents, buffers, bulking agents, isotonicity agents and surfactants. 
     After the substance of interest and any additional components are mixed together, the formulation is lyophilized. Lyophilization generally includes three main stages: freezing, primary drying and secondary drying. Freezing is necessary to convert water to ice or some amorphous formulation components to the crystalline form. Primary drying is the process step when ice is removed from the frozen product by direct sublimation at low pressure and temperature. Secondary drying is the process step when bounded water is removed from the product matrix utilizing the diffusion of residual water to the evaporation surface. Product temperature during secondary drying is normally higher than during primary drying. See, Tang X. et al. (2004) “Design of freeze-drying processes for pharmaceuticals: Practical advice,”  Pharm. Res.,  21:191-200; Nail S. L. et al. (2002) “Fundamentals of freeze-drying,” in Development and manufacture of protein pharmaceuticals. Nail S. L. editor New York: Kluwer Academic/Plenum Publishers, pp 281-353; Wang et al. (2000) “Lyophilization and development of solid protein pharmaceuticals,”  Int. J Pharm.,  203:1-60; Williams N. A. et al. (1984) “The lyophilization of pharmaceuticals; A literature review.”  J Parenteral Sci. Technol.,  38:48-59. Generally, any lyophilization process can be used in connection with the present invention. 
     In some embodiments, an annealing step may be introduced during the initial freezing of the product. The annealing step may reduce the overall cycle time. Without wishing to be bound by any theories, it is contemplated that the annealing step can help promote excipient crystallization and formation of larger ice crystals due to re-crystallization of small crystals formed during supercooling, which, in turn, improves reconstitution. Typically, an annealing step includes an interval or oscillation in the temperature during freezing. For example, the freeze temperature may be −40° C., and the annealing step will increase the temperature to, for example, −10° C. and maintain this temperature for a set period of time. The annealing step time may range from 0.5 hours to 8 hours (e.g., 0.5, 1.0 1.5, 2.0, 2.5, 3, 4, 6, and 8 hours). The annealing temperature may be between the freezing temperature and 0° C. 
     Lyophilization may be performed in a container, such as a tube, a bag, a bottle, a tray, a vial (e.g., a glass vial), syringe or any other suitable containers. The containers may be disposable. Lyophilization may also be performed in a large scale or small scale. In some instances, it may be desirable to lyophilize the protein formulation in the container in which reconstitution of the protein is to be carried out in order to avoid a transfer step. The container in this instance may, for example, be a 3, 4, 5, 10, 20, 50 or 100 cc vial. 
     Many different freeze-dryers are available for this purpose such as Hull pilot scale dryer (SP Industries, USA), Genesis (SP Industries) laboratory freeze-dryers, or any freeze-dryers capable of controlling the given lyophilization process parameters. Freeze-drying is accomplished by freezing the formulation and subsequently subliming ice from the frozen content at a temperature suitable for primary drying. Initial freezing brings the formulation to a temperature below about −20° C. (e.g., −50° C., −45° C., −40° C., −35° C., −30° C., −25° C., etc.) in typically not more than about 4 hours (e.g., not more than about 3 hours, not more than about 2.5 hours, not more than about 2 hours). Under this condition, the product temperature is typically below the eutectic point or the collapse temperature of the formulation. Typically, the shelf temperature for the primary drying will range from about −30 to 25° C. (provided the product remains below the melting point during primary drying) at a suitable pressure, ranging typically from about 20 to 250 mTorr. The formulation, size and type of the container holding the sample (e.g., glass vial) and the volume of liquid will mainly dictate the time required for drying, which can range from a few hours to several days. A secondary drying stage is carried out at about 0-60° C., depending primarily on the type and size of container and the type of therapeutic agent employed. Again, volume of liquid will mainly dictate the time required for drying, which can range from a few hours to several days. 
     As a general proposition, lyophilization will result in a lyophilized formulation in which the moisture content thereof is less than about 5%, less than about 4%, less than about 3%, less than about 2%, less than about 1%, and less than about 0.5%. 
     Reconstitution according to the present invention may be performed in any container. Exemplary containers suitable for the invention include, but are not limited to, such as tubes, vials, syringes (e.g., single-chamber or dual-chamber), bags, bottles, and trays. Suitable containers may be made of any materials such as glass, plastics, metal. The containers may be disposable or reusable. Reconstitution may also be performed in a large scale or small scale. 
     In some instances, it may be desirable to lyophilize the protein formulation in the container in which reconstitution of the protein is to be carried out in order to avoid a transfer step. The container in this instance may, for example, be a 3, 4, 5, 10, 20, 50 or 100 cc vial. In some embodiments, a suitable container for lyophilization and reconstitution is a dual chamber syringe (e.g., Lyo-Ject,® (Vetter) syringes). For example, a dual chamber syringe may contain both the lyophilized substance and the diluent, each in a separate chamber, separated by a stopper (see Example 5). To reconstitute, a plunger can be attached to the stopper at the diluent side and pressed to move diluent into the product chamber so that the diluent can contact the lyophilized substance and reconstitution may take place as described herein (see Example 5). 
     The pharmaceutical compositions, formulations and related methods of the invention are useful for delivering a variety of therapeutic agents to the CNS of a subject (e.g., intrathecally, intraventricularly or intracisternally) and for the treatment of the associated diseases. The pharmaceutical compositions of the present invention are particularly useful for delivering proteins and enzymes (e.g., enzyme replacement therapy) to subjects suffering from lysosomal storage disorders. The lysosomal storage diseases represent a group of relatively rare inherited metabolic disorders that result from defects in lysosomal function. The lysosomal diseases are characterized by the accumulation of undigested macromolecules within the lysosomes, which results in an increase in the size and number of such lysosomes and ultimately in cellular dysfunction and clinical abnormalities. 
     Intrathecal Delivery 
     In some embodiments, intrathecal administration is used to deliver a desired replacement enzyme (e.g., an HNS protein) into the CSF. As used herein, intrathecal administration (also referred to as intrathecal injection) refers to an injection into the spinal canal (intrathecal space surrounding the spinal cord). Various techniques may be used including, without limitation, lateral cerebroventricular injection through a burrhole or cistemal or lumbar puncture or the like. Exemplary methods are described in Lazorthes et al. Advances in Drug Delivery Systems and Applications in Neurosurgery, 143-192 and Omaya et al., Cancer Drug Delivery, 1: 169-179, the contents of which are incorporated herein by reference. 
     According to the present invention, an enzyme may be injected at any region surrounding the spinal canal. In some embodiments, an enzyme is injected into the lumbar area or the cisterna magna or intraventricularly into a cerebral ventricle space. As used herein, the term “lumbar region” or “lumbar area” refers to the area between the third and fourth lumbar (lower back) vertebrae and, more inclusively, the L2-S1 region of the spine. Typically, intrathecal injection via the lumbar region or lumber area is also referred to as “lumbar IT delivery” or “lumbar IT administration.” The term “cisterna magna” refers to the space around and below the cerebellum via the opening between the skull and the top of the spine. Typically, intrathecal injection via cisterna magna is also referred to as “cisterna magna delivery.” The term “cerebral ventricle” refers to the cavities in the brain that are continuous with the central canal of the spinal cord. Typically, injections via the cerebral ventricle cavities are referred to as intravetricular Cerebral (ICV) delivery. 
     In some embodiments, “intrathecal administration” or “intrathecal delivery” according to the present invention refers to lumbar IT administration or delivery, for example, delivered between the third and fourth lumbar (lower back) vertebrae and, more inclusively, the L2-S1 region of the spine. It is contemplated that lumbar IT administration or delivery distinguishes over cisterna magna delivery in that lumbar IT administration or delivery according to our invention provides better and more effective delivery to the distal spinal canal, while cisterna magna delivery, among other things, typically does not deliver well to the distal spinal canal. 
     Device for Intrathecal Delivery 
     Various devices may be used for intrathecal delivery according to the present invention. In some embodiments, a device for intrathecal administration contains a fluid access port (e.g., injectable port); a hollow body (e.g., catheter) having a first flow orifice in fluid communication with the fluid access port and a second flow orifice configured for insertion into spinal cord; and a securing mechanism for securing the insertion of the hollow body in the spinal cord. As a non-limiting example shown in  FIG. 36 , a suitable securing mechanism contains one or more nobs mounted on the surface of the hollow body and a sutured ring adjustable over the one or more nobs to prevent the hollow body (e.g., catheter) from slipping out of the spinal cord. In various embodiments, the fluid access port comprises a reservoir. In some embodiments, the fluid access port comprises a mechanical pump (e.g., an infusion pump). In some embodiments, an implanted catheter is connected to either a reservoir (e.g., for bolus delivery), or an infusion pump. The fluid access port may be implanted or external 
     In some embodiments, intrathecal administration may be performed by either lumbar puncture (i.e., slow bolus) or via a port-catheter delivery system (i.e., infusion or bolus). In some embodiments, the catheter is inserted between the laminae of the lumbar vertebrae and the tip is threaded up the thecal space to the desired level (generally L3-L4). 
     Relative to intravenous administration, a single dose volume suitable for intrathecal administration is typically small. Typically, intrathecal delivery according to the present invention maintains the balance of the composition of the CSF as well as the intracranial pressure of the subject. In some embodiments, intrathecal delivery is performed absent the corresponding removal of CSF from a subject. In some embodiments, a suitable single dose volume may be e.g., less than about 10 ml, 8 ml, 6 ml, 5 ml, 4 ml, 3 ml, 2 ml, 1.5 ml, 1 ml, or 0.5 ml. In some embodiments, a suitable single dose volume may be about 0.5-5 ml, 0.5-4 ml, 0.5-3 ml, 0.5-2 ml, 0.5-1 ml, 1-3 ml, 1-5 ml, 1.5-3 ml, 1-4 ml, or 0.5-1.5 ml. In some embodiments, intrathecal delivery according to the present invention involves a step of removing a desired amount of CSF first. In some embodiments, less than about 10 ml (e.g., less than about 9 ml, 8 ml, 7 ml, 6 ml, 5 ml, 4 ml, 3 ml, 2 ml, 1 ml) of CSF is first removed before IT administration. In those cases, a suitable single dose volume may be e.g., more than about 3 ml, 4 ml, 5 ml, 6 ml, 7 ml, 8 ml, 9 ml, 10 ml, 15 ml, or 20 ml. 
     Various other devices may be used to effect intrathecal administration of a therapeutic composition. For example, formulations containing desired enzymes may be given using an Ommaya reservoir which is in common use for intrathecally administering drugs for meningeal carcinomatosis (Lancet 2: 983-84, 1963). More specifically, in this method, a ventricular tube is inserted through a hole formed in the anterior horn and is connected to an Ommaya reservoir installed under the scalp, and the reservoir is subcutaneously punctured to intrathecally deliver the particular enzyme being replaced, which is injected into the reservoir. Other devices for intrathecal administration of therapeutic compositions or formulations to an individual are described in U.S. Pat. No. 6,217,552, incorporated herein by reference. Alternatively, the drug may be intrathecally given, for example, by a single injection, or continuous infusion. It should be understood that the dosage treatment may be in the form of a single dose administration or multiple doses. 
     For injection, formulations of the invention can be formulated in liquid solutions. In addition, the enzyme may be formulated in solid form and re-dissolved or suspended immediately prior to use. Lyophilized forms are also included. The injection can be, for example, in the form of a bolus injection or continuous infusion (e.g., using infusion pumps) of the enzyme. 
     In one embodiment of the invention, the enzyme is administered by lateral cerebro ventricular injection into the brain of a subject. The injection can be made, for example, through a burr hole made in the subject&#39;s skull. In another embodiment, the enzyme and/or other pharmaceutical formulation is administered through a surgically inserted shunt into the cerebral ventricle of a subject. For example, the injection can be made into the lateral ventricles, which are larger. In some embodiments, injection into the third and fourth smaller ventricles can also be made. 
     In yet another embodiment, the pharmaceutical compositions used in the present invention are administered by injection into the cisterna magna, or lumbar area of a subject. 
     In another embodiment of the method of the invention, the pharmaceutically acceptable formulation provides sustained delivery, e.g., “slow release” of the enzyme or other pharmaceutical composition used in the present invention, to a subject for at least one, two, three, four weeks or longer periods of time after the pharmaceutically acceptable formulation is administered to the subject. 
     As used herein, the term “sustained delivery” refers to continual delivery of a pharmaceutical formulation of the invention in vivo over a period of time following administration, preferably at least several days, a week or several weeks. Sustained delivery of the composition can be demonstrated by, for example, the continued therapeutic effect of the enzyme over time (e.g., sustained delivery of the enzyme can be demonstrated by continued reduced amount of storage granules in the subject). Alternatively, sustained delivery of the enzyme may be demonstrated by detecting the presence of the enzyme in vivo over time. 
     Kits 
     The present invention further provides kits or other articles of manufacture which contains the formulation of the present invention and provides instructions for its reconstitution (if lyophilized) and/or use. Kits or other articles of manufacture may include a container, an IDDD, a catheter and any other articles, devices or equipment useful in interthecal administration and associated surgery. Suitable containers include, for example, bottles, vials, syringes (e.g., pre-filled syringes), ampules, cartridges, reservoirs, or lyo-jects. The container may be formed from a variety of materials such as glass or plastic. In some embodiments, a container is a pre-filled syringe. Suitable pre-filled syringes include, but are not limited to, borosilicate glass syringes with baked silicone coating, borosilicate glass syringes with sprayed silicone, or plastic resin syringes without silicone. 
     Typically, the container may holds formulations and a label on, or associated with, the container that may indicate directions for reconstitution and/or use. For example, the label may indicate that the formulation is reconstituted to total enzyme dose or protein concentrations as described above. The label may further indicate that the formulation is useful or intended for, for example, IT administration. The label may further indicate, as described above, the administration interval, the administration period and/or the appropriate age of an intended recipient. In some embodiments, a container may contain a single dose of a stable formulation containing a therapeutic agent (e.g., a replacement enzyme). In various embodiments, a single dose comprises greater than 10 mg, greater than 45 mg or greater than 90 mg of total replacement enzyme (e.g., H2S). 
     In various embodiments, a single dose is present in a volume of less than about 15 ml, 10 ml, 5.0 ml, 4.0 ml, 3.5 ml, 3.0 ml, 2.5 ml, 2.0 ml, 1.5 ml, 1.0 ml, or 0.5 ml. Alternatively, a container holding the dose may be a multi-use vial, which allows for repeat administrations (e.g., from 2-6 administrations) of one or more dosages. Kits or other articles of manufacture may further include a second container comprising a suitable diluent (e.g., BWFI, saline, buffered saline). Upon mixing of the diluent and the formulation, the final protein concentration in the reconstituted formulation will generally be at least 1 mg/ml (e.g., at least 5 mg/ml, at least 10 mg/ml, at least 25 mg/ml, at least 50 mg/ml, at least 75 mg/ml, at least 100 mg/ml). Kits or other articles of manufacture may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, IDDDs, catheters, syringes, and package inserts with instructions for use. 
     Treatment of Sanfilippo A Syndrome 
     Inventive methods described herein can advantageously facilitate the delivery of recombinant HNS enzyme to targeted organelles and effectively treat Sanfilippo syndrome Type A. In particular, inventive methods described herein can be used to reduce accumulation of glycosaminoglycans (GAG) in the lysosomes of affected cells and tissues and/or to improve cognitive function. 
     Sanfilippo syndrome, or mucopolysaccharidosis III (MPS III), is a rare genetic disorder characterized by the deficiency of enzymes involved in the degradation of glycosaminoglycans (GAG). In the absence of enzyme, partially degraded GAG molecules cannot be cleared from the body and accumulate in lysosomes of various tissues, resulting in progressive widespread somatic dysfunction (Neufeld and Muenzer, 2001). 
     Four distinct forms of MPS III, designated MPS IIIA, B, C, and D, have been identified. Each represents a deficiency in one of four enzymes involved in the degradation of the GAG heparan sulfate. All forms include varying degrees of the same clinical symptoms, including coarse facial features, hepatosplenomegaly, corneal clouding and skeletal deformities. Most notably, however, is the severe and progressive loss of cognitive ability, which is tied not only to the accumulation of heparan sulfate in neurons, but also the subsequent elevation of the gangliosides GM2, GM3 and GD2 caused by primary GAG accumulation (Walkley 1998). 
     Mucopolysaccharidosis type IIIA (MPS IIIA; Sanfilippo Syndrome Type A) is the most severe form of Sanfilippo syndrome and affects approximately 1 in 100,000 people worldwide. Sanfilippo Syndrome Type A (SanA) is characterized by a deficiency of the enzyme heparan N-sulfatase (HNS), an exosulfatase involved in the lysosomal catabolism of glycosaminoglycan (GAG) heparan sulfate (Neufeld E F, et al. The Metabolic and Molecular Bases of Inherited Disease (2001) pp. 3421-3452). In the absence of this enzyme, GAG heparan sulfate (HS) accumulates in lysosomes of neurons and glial cells, with lesser accumulation outside the brain. As a result, HS accumulates significantly in the CSF of afflicted individuals. Thus, elevated levels of GAG in CSF indicate a subject in need of treatment, and reduction in HS levels following intrathecal administration of human recombinant HNS serves as a marker of therapeutic efficacy. In some embodiments, the subject in need of treatment has a GAG level in the CSF greater than about 100 pmol/ml (e.g., about 200 pmol/ml, 300 pmol/ml, 400 pmol/ml, 500 pmol/ml, 600 pmol/ml, 700 pmol/ml, 800 pmol/ml, 900 pmol/ml, 1000 pmol/ml, 1500 pmol/ml, 2000 pmol/ml, 2500 pmol/ml, 3000 pmol/ml, or greater) before the treatment. In some embodiments, the subject in need of treatment has a GAG level in the CSF greater than 1000 pmol/ml before the treatment. 
     Another clinical feature indicating a need for treatment is the accumulation of GAG in the urine of afflicted subjects. In some embodiments, a subject in need of treatment has a GAG level in the urine greater than about 10 μg GAG/mmol creatinine (e.g., about 15, 20, 25, 30, 35, 40, 45, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 μg GAG/mmol creatinine) before the treatment. In some embodiments, a subject in need of treatment has a GAG level in the CSF greater than 20 μg GAG/mmol creatinine before the treatment. 
     A defining clinical feature of this disorder is central nervous system (CNS) degeneration, which results in loss of, or failure to attain, major developmental milestones. The progressive cognitive decline culminates in dementia and premature mortality. The disease typically manifests itself in young children, and the lifespan of an affected individual generally does not extend beyond late teens to early twenties. 
     Compositions and methods of the present invention may be used to effectively treat individuals suffering from or susceptible to Sanfilippo Syndrome Type A. The terms, “treat” or “treatment,” as used herein, refers to amelioration of one or more symptoms associated with the disease, prevention or delay of the onset or progression of one or more symptoms of the disease, and/or lessening of the severity or frequency of one or more symptoms of the disease. 
     In some embodiments, treatment refers to partially or complete alleviation, amelioration, relief, inhibition, delaying onset, reducing severity and/or incidence of neurological impairment in a San A patient. As used herein, the term “neurological impairment” includes various symptoms associated with impairment of the central nervous system (e.g., the brain and spinal cord). Symptoms of neurological impairment may include, for example, developmental delay, progressive cognitive impairment, hearing loss, impaired speech development, deficits in motor skills, hyperactivity, aggressiveness and/or sleep disturbances, among others. 
     In some embodiments, treatment refers to improved or stabilized cognitive functions (i.e. cognitive status or performance) as compared to untreated subjects or pretreatment levels. In some embodiments, treatment refers to a reduced or lessened decline in cognitive functions (i.e. cognitive status or performance) as compared to untreated subjects or pre-treatment levels. In some embodiments, cognitive functions (i.e. cognitive status or performance) are assessed by standardized tests and expressed as a developmental quotient (DQ). In some embodiments, cognitive functions (i.e. cognitive status or performance) are assessed by one or more scales. Any cognitive scale known to those of skill in the art may be used in embodiments of the invention as appropriate for the age and/or developmental status of the subject (As discussed in greater detail below). Exemplary cognitive scales include, but are not limited to, the Bayley Scales of Infant Development and the Kaufman Assessment Battery for Children. Data obtained from scales used in embodiments of the invention may be used to ascertain the mental age equivalence of the subject in months, and a DQ score may be calculated by dividing this by the calendar age in months (multiplied by 100 to give percentage points). Additional measurements of cognitive ability that may be used in embodiments of the invention include the Woodcock-Johnson Psycho Educational Battery (WJPEB), which is an individual test of educational achievement in reading, writing, spelling and math. Standard scores are derived that compare the test-taker against US norms and can be expressed as an age or grade-level equivalency. The Scales of Independent Behavior-Revised (SIB-R), a subtest of WJPEB, which measures a subject&#39;s adaptive behavior and is expressed as a raw score similar to subjects IQ, may also be used. Some embodiment of the invention may utilize the general conceptual ability (GCA) score, which is an indicator of general cognitive ability. In some embodiments, DAS-II (Differential Ability Scales-Second Edition) IQ test may be used. DAS-II is a comprehensive, individually administered, clinical instrument for assessing the cognitive abilities that are important to learning. 
     In some embodiments, treatment refers to decreased lysosomal storage (e.g., of GAG) in various tissues. In some embodiments, treatment refers to decreased lysosomal storage in brain target tissues, spinal cord neurons, and/or peripheral target tissues. In certain embodiments, lysosomal storage is decreased by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more as compared to a control. In some embodiments, lysosomal storage is decreased by at least 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold as compared to a control. In some embodiments, lysosomal storage is measured by the presence of lysosomal storage granules (e.g., zebra-striped morphology). 
     In some embodiments, treatment refers to decreased GAG levels in cerebrospinal fluid (CSF). In some embodiments, CSF GAG levels are decreased by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more as compared to pretreatment or control levels. In some embodiments, CSF GAG levels are decreased by at least 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold as compared to pretreatment or control levels. 
     In particular embodiments, the intrathecal administration of the recombinant HNS enzyme at a therapeutically effective dose and an administration interval results in the GAG level in the CSF lower than 6000 pmol/ml (e.g., lower than about 5000, 4000, 3000, 2000, 1000 pmol/m1). In some embodiments, CSF GAG levels are decreased to lower than about 1000 pmol/ml (e.g., lower than about 900 pmol/ml, 800 pmol/ml, 700 pmol/ml, 600 pmol/ml, 500 pmol/ml, 400 pmol/ml, 300 pmol/ml, 200 pmol/ml, 100 pmol/ml, 50 pmol/ml, 10 pmol/ml, or less). In particular embodiments, the GAG is heparan sulfate (HS). In some embodiments, GAG levels are measured by methods known to those of skill in the art, including but not limited to, electro-spray ionization-tandem mass spectrometry (with and without liquid chromatography), HPLC or LC-MS based assays as described in Lawrence R. et al. Nat. Chem. Biol.; 8(2):197-204. 
     GAG fragments generated by alternative pathways are excreted in urine, providing the basis for diagnostic screening for the MPS. Urine values are expressed as a GAG/creatinine ratio. Thus, in some embodiments, treatment refers to decreased GAG levels in urine. In some embodiments, urine GAG levels are decreased by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more as compared to pretreatment or control levels. In some embodiments, urine GAG levels are decreased by at least 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold as compared to pretreatment or control levels. In some embodiments, lysosomal storage is correspondingly decreased by at least 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold or 10-fold as compared to pretreatment levels. In particular embodiments, the GAG is heparan sulfate (HS). In some embodiments, urine GAG levels are measured by methods known to those of skill in the art, including spectrophotometric assays (i.e., dye binding assays such as dimethylmethylene blue). In various embodiments, the GAG is heparan sulfate (HS). 
     In particular embodiments, the intrathecal administration of the recombinant HNS enzyme at a therapeutically effective dose and an administration interval results in the GAG level in urine lower than lower than 40 μg GAG/mmol creatinine (e.g., lower than about 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1μg GAG/mmol creatinine). In some embodiments, intrathecal administration of the recombinant HNS enzyme results in the GAG level in the urine lower than 10 μg GAG/mmol creatinine. In some embodiments, intrathecal administration of the recombinant HNS enzyme results in the GAG level in the urine lower than 1 μg GAG/mmol creatinine. In various embodiments, the GAG is heparan sulfate (HS). 
     In some embodiments, treatment refers to decreased progression of loss of cognitive ability. In certain embodiments, progression of loss of cognitive ability is decreased by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more as compared to a control. In some embodiments, treatment refers to decreased developmental delay. In certain embodiments, developmental delay is decreased by about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or more as compared to a control. 
     The terms, “improve,” “increase” or “reduce,” as used herein, indicate values that are relative to a control. In some embodiments, a suitable control is a baseline measurement, such as a measurement in the same individual prior to initiation of the treatment described herein, or a measurement in a control individual (or multiple control individuals) in the absence of the treatment described herein. A “control individual” is an individual afflicted with Sanfilippo Syndrome Type A, who is about the same age and/or gender as the individual being treated (to ensure that the stages of the disease in the treated individual and the control individual(s) are comparable). 
     The individual (also referred to as “patient” or “subject”) being treated is an individual (fetus, infant, child, adolescent, or adult human) having Sanfilippo Syndrome Type A or having the potential to develop Sanfilippo Syndrome Type A. The individual can have residual endogenous HNS expression and/or activity, or no measurable activity. For example, the individual having Sanfilippo Syndrome Type A may have HNS expression levels that are less than about 30-50%, less than about 25-30%, less than about 20-25%, less than about 15-20%, less than about 10-15%, less than about 5-10%, less than about 0.1-5% of normal HNS expression levels. 
     Compositions and methods of the present invention may be used to effectively treat subjects of a variety of ages. In certain embodiments of the present invention the subject is approximately 3 years to 22 years in age. In certain embodiments of the present invention, the subject is less than about 10 years in age. In certain embodiments of the present invention, the subject is approximately 3 years to 10 years in age. In certain embodiments, the subject approximately 10 years in age. In certain embodiments of the invention, the subject is less than 3 years of age. In certain embodiments of the invention, the subject is approximately 1 year to 3 years of age. In some embodiments, the median age of a subject is about 3 years. In some embodiments, the median age of a subject is about 1 year of age. In some embodiments, the subject is at least 3 years old. In certain embodiments, the subject is younger than 4 years old. In some embodiments, the subject is at least 1 year old; i.e., at least 12 months old. It is contemplated that early treatment is important to maximize the benefits of treatment. 
     Immune Tolerance 
     Generally, intrathecal administration of a therapeutic agent (e.g., a replacement enzyme) according to the present invention does not result in severe adverse effects in the subject. As used herein, severe adverse effects induce, but are not limited to, substantial immune response, toxicity, or death. As used herein, the term “substantial immune response” refers to severe or serious immune responses, such as adaptive T-cell immune responses. 
     Thus, in many embodiments, inventive methods according to the present invention do not involve concurrent immunosuppressant therapy (i.e., any immunosuppressant therapy used as pre-treatment/pre-conditioning or in parallel to the method). For example, intrathecal administration according to embodiments disclosed herein may not require an immunosuppressant. In some embodiments, inventive methods according to the present invention do not involve an immune tolerance induction in the subject being treated. In some embodiments, inventive methods according to the present invention do not involve a pre-treatment or preconditioning of the subject using T-cell immunosuppressive agent. 
     In some embodiments, intrathecal administration of therapeutic agents can mount an immune response against these agents. Thus, in some embodiments, it may be useful to render the subject receiving the replacement enzyme tolerant to the enzyme replacement therapy Immune tolerance may be induced using various methods known in the art. For example, an initial 30-60 day regimen of a T-cell immunosuppressive agent such as cyclosporin A (CsA) and an antiproliferative agent, such as, azathioprine (Aza), combined with weekly intrathecal infusions of low doses of a desired replacement enzyme may be used. 
     Any immunosuppressant agent known to the skilled artisan may be employed together with a combination therapy of the invention. Such immunosuppressant agents include but are not limited to cyclosporine, FK506, rapamycin, CTLA4-Ig, and anti-TNF agents such as etanercept (see e.g. Moder, 2000, Ann. Allergy Asthma Immunol. 84, 280-284; Nevins, 2000, Curr. Opin. Pediatr. 12, 146-150; Kurlberg et al., 2000, Scand. J. Immunol. 51, 224-230; Ideguchi et al., 2000, Neuroscience 95, 217-226; Potteret al., 1999, Ann. N.Y. Acad. Sci. 875, 159-174; Slavik et al., 1999, Immunol. Res. 19, 1-24; Gaziev et al., 1999, Bone Marrow Transplant. 25, 689-696; Henry, 1999, Clin. Transplant. 13, 209-220; Gummert et al., 1999, J. Am. Soc. Nephrol. 10, 1366-1380; Qi et al., 2000, Transplantation 69, 1275-1283). The anti-IL2 receptor (.alpha.-subunit) antibody daclizumab (e.g. Zenapax™), which has been demonstrated effective in transplant patients, can also be used as an immunosuppressant agent (see e.g. Wiseman et al., 1999, Drugs 58, 1029-1042; Beniaminovitz et al., 2000, N. Engl J. Med. 342, 613-619; Ponticelli et al., 1999, Drugs R. D. 1, 55-60; Berard et al., 1999, Pharmacotherapy 19, 1127-1137; Eckhoff et al., 2000, Transplantation 69, 1867-1872; Ekberg et al., 2000, Transpl. Int. 13, 151-159). Additionalimmunosuppressant agents include but are not limited to anti-CD2 (Branco et al., 1999, Transplantation 68, 1588-1596; Przepiorka et al., 1998, Blood 92, 4066-4071), anti-CD4 (Marinova-Mutafchieva et al., 2000, Arthritis Rheum. 43, 638-644; Fishwild et al., 1999, Clin. Immunol. 92, 138-152), and anti-CD40 ligand (Hong et al., 2000, Semin. Nephrol. 20, 108-125; Chirmule et al., 2000, J. Virol. 74, 3345-3352; Ito et al., 2000, J. Immunol. 164, 1230-1235). 
     Administration 
     Inventive methods of the present invention contemplate single as well as multiple administrations of a therapeutically effective amount of the therapeutic agents (e.g., replacement enzymes) described herein. Therapeutic agents (e.g., replacement enzymes) can be administered at regular intervals, depending on the nature, severity and extent of the subject&#39;s condition (e.g., a lysosomal storage disease). In some embodiments, a therapeutically effective amount of the therapeutic agents (e.g., replacement enzymes) of the present invention may be administered intrathecally periodically at regular intervals (e.g., once every year, once every six months, once every five months, once every three months, bimonthly (once every two months), monthly (once every month), biweekly (once every two weeks), weekly). 
     In some embodiments, intrathecal administration may be used in conjunction with other routes of administration (e.g., intravenous, subcutaneously, intramuscularly, parenterally, transdermally, or transmucosally (e.g., orally or nasally)). In some embodiments, those other routes of administration (e.g., intravenous administration) may be performed no more frequent than biweekly, monthly, once every two months, once every three months, once every four months, once every five months, once every six months, annually administration. 
     As used herein, the term “therapeutically effective amount” is largely determined based on the total amount of the therapeutic agent contained in the pharmaceutical compositions of the present invention. Generally, a therapeutically effective amount is sufficient to achieve a meaningful benefit to the subject (e.g., treating, modulating, curing, preventing and/or ameliorating the underlying disease or condition). For example, a therapeutically effective amount may be an amount sufficient to achieve a desired therapeutic and/or prophylactic effect, such as an amount sufficient to modulate lysosomal enzyme receptors or their activity to thereby treat such lysosomal storage disease or the symptoms thereof (e.g., a reduction in or elimination of the presence or incidence of “zebra bodies” or cellular vacuolization following the administration of the compositions of the present invention to a subject). Generally, the amount of a therapeutic agent (e.g., a recombinant lysosomal enzyme) administered to a subject in need thereof will depend upon the characteristics of the subject. Such characteristics include the condition, disease severity, general health, age, sex and body weight of the subject. One of ordinary skill in the art will be readily able to determine appropriate dosages depending on these and other related factors. In addition, both objective and subjective assays may optionally be employed to identify optimal dosage ranges. 
     A therapeutically effective amount is commonly administered in a dosing regimen that may comprise multiple unit doses. For any particular therapeutic protein, a therapeutically effective amount (and/or an appropriate unit dose within an effective dosing regimen) may vary, for example, depending on route of administration, on combination with other pharmaceutical agents. Also, the specific therapeutically effective amount (and/or unit dose) for any particular patient may depend upon a variety of factors including the disorder being treated and the severity of the disorder; the activity of the specific pharmaceutical agent employed; the specific composition employed; the age, body weight, general health, sex and diet of the patient; the time of administration, route of administration, and/or rate of excretion or metabolism of the specific fusion protein employed; the duration of the treatment; and like factors as is well known in the medical arts. 
     In some embodiments, the therapeutically effective dose is defined by total enzyme administered per dose. In some embodiments, the therapeutically effective total enzyme dose ranges from about 10 mg to about 100 mg, e.g., from about 10 mg to about 90 mg, from about 10 mg to about 80 mg, from about 10 mg to about 50 mg, from about 10 mg to about 40 mg, from about 10 mg to about 30 mg, and from about 10 mg to about 20 mg. In some embodiments, the total enzyme dose is from about 40 mg to about 50 mg. In some embodiments, the therapeutically effective dose is or greater than about 10 mg, 15 mg, 20 mg, 25 mg, 30 mg, 35 mg, 40 mg, 45 mg, 50 mg, 55 mg, 60 mg, 65 mg, 70 mg, 75 mg, 80 mg, 85 mg, 90 mg, 95 mg, 100 mg per dose. In some embodiments, the therapeutically effective dose is or greater than about 45 mg per dose. In some embodiments, the therapeutically effective dose is or greater than about 90 mg per dose. 
     In some embodiments, the therapeutically effective dose ranges from about 0.005 mg/kg brain weight to 500 mg/kg brain weight, e.g., from about 0.005 mg/kg brain weight to 400 mg/kg brain weight, from about 0.005 mg/kg brain weight to 300 mg/kg brain weight, from about 0.005 mg/kg brain weight to 200 mg/kg brain weight, from about 0.005 mg/kg brain weight to 100 mg/kg brain weight, from about 0.005 mg/kg brain weight to 90 mg/kg brain weight, from about 0.005 mg/kg brain weight to 80 mg/kg brain weight, from about 0.005 mg/kg brain weight to 70 mg/kg brain weight, from about 0.005 mg/kg brain weight to 60 mg/kg brain weight, from about 0.005 mg/kg brain weight to 50 mg/kg brain weight, from about 0.005 mg/kg brain weight to 40 mg/kg brain weight, from about 0.005 mg/kg brain weight to 30 mg/kg brain weight, from about 0.005 mg/kg brain weight to 25 mg/kg brain weight, from about 0.005 mg/kg brain weight to 20 mg/kg brain weight, from about 0.005 mg/kg brain weight to 15 mg/kg brain weight, from about 0.005 mg/kg brain weight to 10 mg/kg brain weight. 
     In some embodiments, the therapeutically effective dose is or greater than about 5 mg/kg brain weight, about 10 mg/kg brain weight, about 15 mg/kg brain weight, about 20 mg/kg brain weight, about 25 mg/kg brain weight, about 30 mg/kg brain weight, about 35 mg/kg brain weight, about 40 mg/kg brain weight, about 45 mg/kg brain weight, about 50 mg/kg brain weight, about 55 mg/kg brain weight, about 60 mg/kg brain weight, about 65 mg/kg brain weight, about 70 mg/kg brain weight, about 75 mg/kg brain weight, about 80 mg/kg brain weight, about 85 mg/kg brain weight, about 90 mg/kg brain weight, about 95 mg/kg brain weight, about 100 mg/kg brain weight, about 200 mg/kg brain weight, about 300 mg/kg brain weight, about 400 mg/kg brain weight, or about 500 mg/kg brain weight. 
     In some embodiments, the therapeutically effective dose may also be defined by mg/kg body weight. As one skilled in the art would appreciate, the brain weights and body weights can be correlated. Dekaban A S. “Changes in brain weights during the span of human life: relation of brain weights to body heights and body weights,” Ann Neurol 1978; 4:345-56. Thus, in some embodiments, the dosages can be converted as shown in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Change in Brain Wight During Early Human Development 
               
            
           
           
               
               
            
               
                   
                 Body Weight (kg) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Age 
                   
                 No. of 
                 Brain Weight (kg) 
                 Body Height (m) 
                   
                 % 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Group 
                 Age (  ) 
                 Brains 
                 Mean 
                 SD 
                 SEM 
                 % Change a   
                 Mean 
                 SD 
                 SEM 
                 % Change b   
                 Mean 
                 SD 
                 SEM 
                 Change c   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 1 
                 NB (0-10 d) 
                 241 
                 0.38 
                 0.09 
                 0.00 
                 — 
                 0.50 
                 0.05 
                 0.00 
                 — 
                 2.95 
                 0.42 
                 0.03 
                 — 
               
               
                 2 
                 0.5 (4-8 mo) 
                 87 
                 0.64 
                 0.16 
                 0.01 
                 66.8 
                 0.59 
                 0.09 
                 0.01 
                 18.6 
                 5.88 
                 3.06 
                 0.32 
                 99.4 
               
               
                 3 
                 1 (9-18 mo) 
                 33 
                 0.97 
                 0.18 
                 0.02 
                 50.6 
                 0.76 
                 0.11 
                 0.02 
                 28.5 
                 9.47 
                 2.37 
                 0.41 
                 61.2 
               
               
                 4 
                 2 (19-30 mo) 
                 53 
                 1.12 
                 0.20 
                 0.02 
                 16.2 
                 0.85 
                 0.12 
                 0.01 
                 11.7 
                 13.20 
                 3.57 
                 0.49 
                 39.3 
               
               
                 5 
                 3 (31-45 mo) 
                 19 
                 1.27 
                 0.21 
                 0.04 
                 12.8 
                 0.94 
                 0.09 
                 0.02 
                 11.0 
                 15.55 
                 3.43 
                 0.78 
                 17.9 
               
               
                 6 
                 4-5 
                 29 
                 1.30 
                 0.02 
                 0.00 
                 2.3 
                 1.06 
                 0.03 
                 0.00 
                 12.8 
                 19.46 
                 1.21 
                 0.22 
                 25.1 
               
               
                 
                   
                 
               
               
                   
               
               
                     indicates data missing or illegible when filed 
               
            
           
         
       
     
     In some embodiments, the therapeutically effective dose may also be defined by mg/15 cc of CSF. As one skilled in the art would appreciate, therapeutically effective doses based on brain weights and body weights can be converted to mg/15 cc of CSF. For example, the volume of CSF in adult humans is approximately 150 mL (Johanson CE, et al. “Multiplicity of cerebrospinal fluid functions: New challenges in health and disease,” Cerebrospinal Fluid Res. 2008 May 14; 5:10). Therefore, single dose injections of 0.1 mg to 50 mg protein to adults would be approximately 0.01 mg/15 cc of CSF (0.1 mg) to 5.0 mg/15 cc of CSF (50 mg) doses in adults. 
     In accordance with embodiments described herein, the present invention provides, in part, therapeutically effective and appropriately timed dosing regimens (i.e., administration schedules) for enzyme replacement therapies to treat lysosomal storage diseases with maximum efficacy. For example, a replacement enzyme (e.g., heparan N-sulfatase (HNS)) for a lysosomal storage disease (e.g., Sanfilippo A Syndrome) can be directly introduced into the cerebrospinal fluid (CSF) of a subject in need of treatment at a total enzyme dose (e.g., about 10-100 mg per dose) such that the enzyme effectively and extensively reduces GAG levels in CSF and/or urine. Stated another way, embodiments of the present invention are based on the discovery, disclosed for the first time herein, that a therapeutically effective dose is optimally determined by total enzyme content rather than by concentration or mg/kg brain weight. Although these measurements may be utilized in some embodiments, the present inventors have discovered that total enzyme per dose is one of the most important determinants of therapeutic efficacy 
     In some embodiments, the intrathecal administration is used in conjunction with intravenous administration. In some embodiments, the intravenous administration is no more frequent than once every week. In some embodiments, the intravenous administration is no more frequent than once every two weeks. In some embodiments, the intravenous administration is no more frequent than once every month. In some embodiments, the intravenous administration is no more frequent than once every two months. In certain embodiments, the intravenous administration is more frequent than monthly administration, such as twice weekly, weekly, every other week, or twice monthly. 
     In some embodiments, the treatment regimen is continued until results indicative of therapeutic efficacy (e.g., reduction in CSF HNS levels) are observed. The present inventors have discovered the period over which the therapeutically effective dosages and accompanying administration levels described herein should be continued in order to observe optimal effect on CSF and uring GAG levels. For example, treatment may be administered at a therapeutically effective dose and at an administration interval for a period sufficient to decrease glycosaminoglycan (GAG) heparan sulfate level in the cerebrospinal fluid (CSF) and/or urine relative to a control. In some embodiments, the period is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, 24, 30, 36 months or more. In some embodiments, therapeutically effective doses (e.g., total enzyme dose) may be administered according to any one of the above intervals for at least six weeks; e.g., at least ten weeks, at least fourteen weeks, at least twenty weeks, at least twenty-four weeks, at least thirty weeks or more (e.g., indefinitely). In some embodiments, a recombinant heparin N-Sulfatase (HNS) enzyme is administered at a therapeutically effective dose and an administration interval for a period sufficient to improve, stabilize or reduce declining of one or more cognitive functions relative to a control. 
     It is contemplated that starting treatment before the onset of significant cognitive decline is important for measurable improvements, stabilizations or reduced declines in cognitive functions relative to controls. For example, in patients with MPSIIIA, intrathecal enzyme replacement therapy may have to be initiated before one or more cognitive parameters has decline by more than 50%. 
     In some embodiments, a treatment regimen of enzyme replacement therapy (e.g., HNS) is initiated before cognitive status has substantially declined. For example, treatment may be particularly beneficial if initiated before cognitive status has declined by no more than 60% relative to baseline or control levels, e.g. by no more than 50%, by no more than 40%, by no more than 30%, by no more than 20% or by no more than 10%. Cognitive status may be qualitatively or quantitatively assessed by the tests disclosed herein. For example, in a particular embodiment, treatment is most effective if administered before a subject&#39;s developmental quotient (DQ) has declined by about 50% relative to baseline levels. In particular embodiments, treatment is particularly effective if begun before a subject&#39;s DQ score has declined to less than about 30; e.g., the subject&#39;s DQ score is about 30 or higher, about 40 or higher, about 50 or higher, about 60 or higher, about 70 or higher, etc. 
     It is to be further understood that for any particular subject, specific dosage regimens should be adjusted over time according to the individual need and the professional judgment of the person administering or supervising the administration of the enzyme replacement therapy and that dosage ranges set forth herein are exemplary only and are not intended to limit the scope or practice of the claimed invention. Thus, some embodiments of the invention further comprise a step of adjusting the dose and/or administration interval for intrathecal administration based on the GAG level in the CSF and/or the urine. For example, the therapeutic effective dose for intrathecal administration may be adjusted if the GAG level in the CSF or urine fails to decrease relative to the control after 4 doses. 
     In some embodiments, optimal ages at which intrathecal administration of human recombinant sulfatases (e.g., H2S) should be initiated to maintain cognitive status, stabilize cognitive decline or improve cognitive performance is or younger than 5, 4, 3, 2, 1 years old. 
     Cognitive Performance 
     Among other things, the present invention may be used to effectively treat various cognitive and physical impairments associated with, or resulting from, Sanfilippo Type A. In some embodiments, treatment according to the present invention results in improved cognitive performance of a patient suffering from Sanfilippo Type A. As used herein, cognitive performance includes, but is not limited to, cognitive, adaptive, motor, and/or executive functions. Thus, in some embodiments, a treatment marker may be used to monitor improvement, stabilization, reduction or enhancement of one or more cognitive, adaptive, motor, and/or executive functions relative to a control. 
     Assessment of Cognitive Performance 
     Typically, cognitive performance may be assessed using a cognitive performance test, such as a cognitive performance instrument. As used herein, the term “cognitive performance instrument” includes a cognitive performance test that can be used to evaluate, classify and/or quantify one or more cognitive, adaptive motor and/or executive functions in a subject. As will be understood by those skilled in the art, such a test may be questionnaire or survey filled out by a patient, caregiver, parent, teacher, therapist or psychologist. Exemplary cognitive performance instruments suitable for assessing cognitive, adaptive motor and/or executive functions are described below. 
     Differential Abilities Scale (DAS-II) 
     In some specific embodiments, the cognitive performance instrument is the Differential Ability Scale. The Differential Ability Scale, as the name implies, was developed specifically to be suitable for patients with various types of impairment. The DAS-II is a cognitive test that is designed primarily as a profile test which yields scores for a wide range of abilities, measured either by subtests or composites. However, it has been used as a general test of cognitive ability, including in severely affected populations. The DAS-II comprises 2 overlapping batteries. The Early Years battery is designed for children ages 2 years 6 months through 6 years 11 months. The School-Age Battery is designed for children ages 7 years 0 months through 17 years 11 months. A key feature of these batteries is that they were fully co-normed for ages 5 years 0 months through 8 years 11 months. In consequence, children ages 7 years 0 months through 8 years 11 months can be given the Early Years battery if that is considered more developmentally appropriate for an individual than the School-Age Battery. Similarly, more able children ages 5 years 0 months through 6 years 11 months can be given the School-Age Battery. As a result, the test accommodates all 5 to 8 year old children (i.e., 5 years 0 months through 8 years 11 months) at the extremes of the ability range. 
     The DAS-II has been validated and normed in the US population and in the British population (as the BAS, or British Abilities Scales). A Spanish version, intended for use in Spain and Spanish-speaking Latin America, is expected to become available in the fall of 2012. The DAS-II incorporates “tailored testing” to enable examiners to select the most appropriate items for a child. This has two major advantages. First, it enables the measure to be both accurate and very time-efficient, which is a major advantage for the examiner. Second, it makes testing shorter and less tiring for the child and often enables the child to discontinue a subtest before having experienced a string of consecutive failures—an advantage for the child, as the tests are more enjoyable and motivating. Without being a limiting example, Table 4 discloses a plurality of subtest capable of measuring different cognitive abilities, for a subject undergoing enzyme replacement therapy.  FIG. 19  shows the same subtests and the age ranges at which they are normed. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 List of Cognitive Performance Instruments 
               
            
           
           
               
               
               
            
               
                 Subtest 
                 Abbreviation 
                 Abilities Measured 
               
               
                   
               
               
                 Copying 
                 Copy 
                 Visual-perceptual matching and fine-motor coordination in copying 
               
               
                   
                   
                 line drawings 
               
               
                 Early number 
                 ENC 
                 Knowledge of pre-numerical and numerical concepts 
               
               
                 concepts 
               
               
                 Matching letter-like 
                 MLLF 
                 Visual discrimination among similar shapes 
               
               
                 forms 
               
               
                 Matrices 
                 Mat 
                 Nonverbal reasoning: perception and application of relationships 
               
               
                   
                   
                 among abstract figures 
               
               
                 Naming vocabulary 
                 NVoc 
                 Expressive language; knowledge of names 
               
               
                 Pattern construction 
                 PCon 
                 Visual-perceptual matching, especially of spatial orientation, in 
               
               
                   
                   
                 copying block patterns. Nonverbal reasoning and spatial 
               
               
                   
                   
                 visualization in reproducing designs with colored blocks 
               
               
                 Pattern Construction 
                 PCon(A) 
                 The same abilities for Pattern construction without a time 
               
               
                 (alt) 
                   
                 constraint 
               
               
                 Phonological 
                 PhP 
                 Knowledge of sound structure of the English language and the 
               
               
                 processing 
                   
                 ability to manipulate sound 
               
               
                 Picture similarities 
                 PSim 
                 Nonverbal reasoning shown by matching pictures that have a 
               
               
                   
                   
                 common element or concept 
               
               
                 Rapid naming 
                 RNam 
                 Automaticity of integration of visual symbols with phonologically 
               
               
                   
                   
                 referenced naming 
               
               
                 Recall of designs 
                 RDes 
                 Short-term recall of visual and spatial relationships through 
               
               
                   
                   
                 reproduction of abstract figures 
               
               
                 Recall of digits 
                 DigF 
                 Short-term auditory memory and oral recall of sequences of 
               
               
                 forward 
                   
                 numbers 
               
               
                 Recall of digits 
                 DigB 
                 Short-term auditory memory and oral recall of sequences of 
               
               
                 backward 
                   
                 numbers 
               
               
                 Recall of objects - 
                 RObI 
                 Short-term recall of verbal and pictorial information 
               
               
                 Immediate 
               
               
                 Recall of objects - 
                 RObD 
                 Intermediate-term recall of verbal and pictorial information 
               
               
                 Delayed 
               
               
                 Recall of sequential 
                 SeqO 
                 Short-term recall of verbal and pictorial information 
               
               
                 order 
               
               
                 Recognition of 
                 RPic 
                 Short-term, nonverbal visual memory measure through recognition 
               
               
                 pictures 
                   
                 of familiar objects 
               
               
                 Sequential and 
                 SQR 
                 Detection of sequential patterns in figures or numbers 
               
               
                 quantitative reasoning 
               
               
                 Speed of information 
                 SIP 
                 Quickness in performing simple mental operations 
               
               
                 processing 
               
               
                 Verbal 
                 VCom 
                 Receptive language: understanding of oral instructions involving 
               
               
                 comprehension 
                   
                 basic language concepts 
               
               
                 Verbal similarities 
                 VSim 
                 Verbal reasoning and verbal knowledge 
               
               
                 Word definitions 
                 WDef 
                 Knowledge of word meanings as demonstrated through spoken 
               
               
                   
                   
                 language 
               
               
                   
               
            
           
         
       
     
     Scales of Independent Behavior-Revised (SIB-R) 
     In some specific embodiments, the cognitive performance instrument is the scales of independent behavior-revised. The Scales of Independent Behavior-Revised (SIB-R) is a measure of adaptive behavior comprising 14 subscales organized into 4 adaptive behavior clusters: (1) Motor skills, (2) Social Interaction/Communication, (3) Personal Living skills and (4) Community and Living skills. For each item, the rater is presented with statements that ask them to evaluate the ability and frequency with which the individual being rated can or does perform, in its entirety, a particular task without help or supervision. The individual&#39;s performance is rated on a 4-point Likert scale, with responses including (0): Never or Rarely—even if asked; (1) Does, but not Well—or about one quarter of the time—may need to be asked; (2) does fairly well—or about three quarters of the time—may need to be asked; (3) does very well—always or almost always without being asked. 
     It also measures 8 areas of problem behavior. The SIB-R provides norms from infancy through to the age of 80 and above. It has been used in children with autism and intellectual disability. Some experts consider that one of the strengths of the SIB-R is that has application for basic adaptive skills and problem behaviors of children with significant cognitive or autistic spectrum disorders and can map to American Association of Mental Retardation levels of support. The STB-R is considered to be much less vulnerable to exaggeration than some other measures of adaptive behaviors. 
     Bayley Scales of Infant Development 
     In some embodiments, the evaluation of developmental function may be performed using one or more developmental performance instruments. In some embodiments, the developmental performance instrument is the Bayley Scales of Infant Development (BSID-III). The Bayley Scales of Infant Development is a standard series of measurements used primarily to assess the motor (fine and gross), language (receptive and expressive), and cognitive development of infants and toddlers, ages 0-3. This measure consists of a series of developmental play tasks and takes between 45-60 minutes to administer. Raw scores of successfully completed items are converted to scale scores and to composite scores. These scores are used to determine the child&#39;s performance compared with norms taken from typically developing children of their age (in months). The assessment is often used in conjunction with the Social-Emotional Adaptive Behavior Questionnaire. Completed by the parent or caregiver, this questionnaire establishes the range of adaptive behaviors that the child can currently achieve and enables comparison with age norms. 
     Wechsler Intelligence Scale for Children (WISC) 
     In some embodiments, the Wechsler Intelligence Scale for Children (WISC) may be performed. Typically, the WISC test is an individually administered intelligence test for children, in particular, children between the ages of 6 and 16 inclusive. In some embodiments, the WISC test can be completed without reading or writing. An WISC score generally represents a child&#39;s general cognitive ability. 
     Vineland Adaptive Behavior Scales 
     In some embodiments, Vineland Adaptive Behavior Scales are performed. Typically, Vineland Adaptive Behavior Scales measure a person&#39;s adaptive level of functioning. Typically, the content and scales of Vineland Adaptive Behavior Scales are organized within a three domain structure: Communication, Daily Living, and Socialization. This structure corresponds to the three broad Domains of adaptive functioning recognized by the American Association of Mental Retardation (AAMR, 2002): Conceptual, Practical, and Social. In addition, Vineland Adaptive Behavior Scales offer a Motor Skills Domain and an optional Maladaptive Behavior Index to provide more in-depth information 
     Biomarkers 
     Alternatively, biomarkers of Sanfilipo Type A may also be used. Suitable biomarkers for the present invention may include any substances (e.g., proteins or nucleic acids) that can be used as an indicator of a disease state of Sanfilipo Type A, the severity of the syndrome, or responses to a therapeutic intervention. Typically, a suitable biomarkers has a characteristic that can be objectively measured and evaluated as an indicator. Typically, a suitable biomarker for Sanfilipo Type A syndrome is differentially expressed between Sanfilipo Type A syndrome patients and normal healthy individuals. Such biomarkers may be used alone or in combination as an indicator to evaluate risk for Sanfilipo Type A, detect the presence of Sanfilipo Type A, monitor progression or abatement of Sanfilipo Type A, and/or monitor treatment response or optimization. In some embodiments, individual biomarkers described herein may be used. In some embodiments, at least two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, or nineteen biomarkers may be used in combination as a panel. Thus, in some embodiments, one or more biomarkers described herein (e.g., those provided in Table 5), may be used in conjunction with additional markers, such as, for example, glycosaminoglycan (GAG) heparan sulfate (HS), beta-hexosaminidase, LAMP1, LAMP2, to name but a few. Additional exemplary molecular treatment markers suitable for using in diagnosing, evaluating severity, monitoring treatment or adjusting ERT treatment of Sanfilipo Type A are described in International Application PCT/US12/63935, entitled “BIOMARKERS FOR ANFILIPPO SYNDROME AND USES THEREOF,” the contents of which are hereby incorporated by reference. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Exemplary Treatment Markers for Sanfilipo Type A 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Linear 
                 Quadratic 
                 Nearest- 
               
               
                 Biomarker 
                 Abbreviation 
                 Analysis 
                 Analysis 
                 Neighbor 
               
               
                   
               
               
                 Alpha-1-Antitrypsin 
                 AAT 
                 — 
                 — 
                 0.0750 
               
               
                 Alpha-2-Macroglobulin 
                 Alpha-2-M 
                 0.0667 
                 0.0000 
                 0.0500 
               
               
                 Apolipoprotein B 
                 Apo B 
                 — 
                 — 
                 0.1000 
               
               
                 Calbindin 
                   
                 0.1000 
                 0.0333 
                 0.0500 
               
               
                 Complement C3 
                 C3 
                 — 
                 0.0583 
                 0.0583 
               
               
                 Fatty Acid-Binding Protein, heart 
                 H-FABP 
                 — 
                 0.0583 
                 0.0333 
               
               
                 Heparin-Binding EGF-Like Growth 
                 HB-EGF 
                 0.1000 
                 — 
                 — 
               
               
                 Factor 
               
               
                 Hepatocyte Growth Factor 
                 HGF 
                 — 
                 0.0417 
                 0.0167 
               
               
                 Kallikrein-7 
                 KLK-7 
                 — 
                 0.0500 
                 0.1000 
               
               
                 Lysosomal-Associated Membrane 
                 LAMP2 
                 0.1000 
                 0.1000 
                 0.0750 
               
               
                 Protein 2 
               
               
                 Macrophage Colony-Stimulating 
                 M-CSF 
                 — 
                 0.1000 
                 0.0667 
               
               
                 Factor 1 
               
               
                 Monocyte Chemotactic Protein 1 
                 MCP-1 
                 — 
                 0.0750 
                 0.0500 
               
               
                 Sex Hormone-Binding Globulin 
                 SHBG 
                 0.0667 
                 0.0250 
                 0.0000 
               
               
                 Tau 
                   
                 — 
                 0.0333 
                 0.0667 
               
               
                 Thyroxine-Binding Globulin 
                 TBG 
                 — 
                 0.0917 
                 0.0667 
               
               
                 Tumor Necrosis Factor Receptor-Like 2 
                 TNFR2 
                 0.0500 
                 0.0833 
                 0.0333 
               
               
                 Vascular Endothelial Growth Factor 
                 VEGFR-1 
                 — 
                 0.0750 
                 0.0583 
               
               
                 Receptor 1 
               
               
                 Vitronectin 
                   
                 — 
                 — 
                 0.0500 
               
               
                 pTau(181) 
                   
                 — 
                 0.0917 
                 0.0667 
               
               
                   
               
            
           
         
       
     
     Neuoranatomical Markers 
     In some embodiments, a suitable biomarker is associated with neuroanatomical structures and/or their function and is thus classified as a neuroanatomical marker. In some embodiments, neuroanatomical markers include, but are not limited to, total brain volume, total brain size, brain tissue composition, grey matter volume, white matter volume, cortical volume, cortical thickness, ventricular and CSF volume, cerebella volume, basal ganglia size, basal ganglia volume, frontal lobe volume, parietal lobe volume, occipital lobe volume, and/or temporal lobe volume. In some embodiments, neuroanatomical markers include, but are not limited to, electrical impulse, synaptic firing, neuro-kinetics and/or cerebral blood flow. One skilled in the art will appreciate that a large number of analytical tests may be used to assay any of the structural or functional biomarkers described above. For example, in some embodiments, neuroanatomical biomarkers may be assayed using X-rays, Positron Emission Tomography (PET), PIB-PET, F18 PET, Single Photon Emission Computed Tomography (SPECT), Magnetic Resonance Imaging (MRI), Functional Magnetic Resonance Imaging (fMRI), Difusion-tensor MRI (DTMRI), Diffusion-weighted MRI (DWMRI), Perfusion-weighted MRI (PWMRI), Diffusion-Perfusion-weighted MRI (DPWMRI), Magnetic Resonance Spectroscopy (MRS), electroencephalography (EEG), magnetoencephalography (MEG), Transcranial magnetic stimulation (TMS), Deep brain stimulation (DBS), Laser Doppler Ultrasound, Optical tomographic imaging, Computer Assisted Tomography (CT) and/or Structural MRT (sMRT). The assay methods described above may be used with or without a contrast reagent, such as a fluorescent or radio labeled compound, antibody, oligonucleotide, protein or metabolite. 
     EXAMPLES 
     Example 1 
     Clinical Trial and Natural History Study of MPSIII A Patients 
     As discussed above, mucopolysaccharidosis III (MPS-III), also known as Sanfilippo Syndrome Type A, is a rare autosomal recessive lysosomal storage disease, caused by a deficiency in one of the enzymes needed to break down the glycosaminoglycan, heparan sulfate (HS). Heparan sulfate is an important cell surface glycoprotein and a critical component in forming and maintaining the extra-cellular matrix. Four different types of MPS-III (Sanfilippo Syndrome) have been identified: MPS-III A, B, C and D (i.e., Sanfilippo syndrome A, B, C and D). While each of the four MPS-III types display substantially similar clinical symptoms, they are each distinguished by a different enzyme deficiency. MPS-III A (Sanfilippo Syndrome A) has been shown to occur as a result of 70 different possible mutations in the heparan N-sulfatase gene, which reduce enzyme function. As a result, each of the enzyme defects causes accumulation of heparan sulfate in Sanfilippo Syndrome patients. 
     Although the pathological cascade for the disease is poorly understood, it has been shown that primary accumulation of heparan sulfate triggers secondary accumulation of toxic metabolites, neuroinflammation, disrupts growth factor signaling and leads to dysregulated cell death. Clinical features in Sanfilippo Syndrome patients are overwhelmingly neurological. Typically, a Sanfilippo Syndrome patient has a normal early infancy. Developmental delays often are first manifestations of the disease. Several behavioral disturbances are a prominent feature of mild childhood, such as progressive dementia which can lead to a “quiet phase” of withdrawal and developmental regression. Typically, a Sanfilippo Syndrome patient survives to late teens or early 20s. To better understand the pathology underlining Sanfilippo Syndrome, and evaluate a treatment approach, the inventors conducted both a clinical trial and a natural history study for MPS-III A. 
     Natural History Study 
     The natural history study was an observational based study with no investigational treatment, with the primary goal designed to gain insight and develop an understanding of the MPS-IIIA clinical disease spectrum. The second goal of the study was to define a series of clinically definable parameters that could be used to monitor progression of the disease over a 12 month period. This data would be used to establish a baseline for the normal progression of the disease, and to identify candidate clinical endpoints for use with the clinical trial to monitor enzyme replacement therapy. In addition, the subjects within the natural history study were used for comparison with subjects enrolled in the clinical trial, to serves as a control group. 
     For the study, a total of 25 geographically diverse disease subjects (16 males and 9 females), with a confirmed diagnosis of MPS-IIIA were recruited. Each MPS-IIIA subject was required to have a calendar and developmental age, each greater than 1 year. The control group for the study was comprised of 20 young healthy adult subjects, from a wide geographical distribution from across North America. The evaluations were conducted every 6 months over the course of a year. Each MPS-IIIA and control patient, was subjected to a comprehensive neurodevelopmental assessment and brain imaging. As demonstrated in  FIG. 1 , each of the subjects enrolled in the Natural History study demonstrated a progressive decrease in developmental quotient, over the 1 year study period ( FIG. 1 ). 
     Developmental assessment was performed using either the Bayley Scales of Infant Development III (BSID) or Kaufman Assessment Battery for Children (KABC) approach. For both the BSID and KABC methods, a total mental age equivalent (MA) was calculated in months, for every participant. A subject&#39;s developmental quotient (DQ), was determined by dividing a subject&#39;s mental age equivalent by their chronological age in months: DQ(%)=(MA/CA)×100. For the study, developmental analysis were carried out on a total of 23 subjects. The first group consisted of 17 subjects, each diagnosed with MPS-IIIA before age 6, with an average DQ of 26+18. The second group consisted of 6 subjects, each diagnosed with MPS-IIIA after age 6, with an average DQ of 52±27. As demonstrated in  FIG. 1 , each of the subjects enrolled in the Natural History study demonstrated a progressive decrease total grey matter volume, over the 1 year study period ( FIG. 2 ). 
     Brain imaging was performed for each subject using non-contrast MRT. For the study, brain scans were carried out on a total of 23 subjects. The first group consisted of 17 subjects, each diagnosed with MPS-IIIA before age 6, with an average age of 4.3±1.7 years. The second group consisted of 6 subjects, each diagnosed with MPS-IIIA after age 6, with an average age of 10.7±3.7 years. Brain volume for the study, was assessed by evaluating several different anatomic criteria such as: Gray matter volume, White matter volume, Cortical volume, Ventricular+CSF volume, Cerebella volume and Total Brain volume). The data was analyzed to evaluate a possible correlation between changes in brain volume over time, when compared to a MPS-IIIA subjects calendar age and development stage. 
     Observations 
     Based on the findings from the study, several key trends were observed. First, a comparison between a subject&#39;s baseline developmental stage and age, revealed a possible age-related decline. The majority of patients exhibited a general decline in developmental quotient over the 1 year period without therapeutic intervention ( FIG. 1 ). Since children diagnosed before and after the age of 6 years exhibit different patterns of disease progression, it suggest that late diagnosis may be a surrogate for a phenotypic and prognostic difference. This is potentially further supported by the analysis of brain volume. The data demonstrates a dramatic reduction in cortical gray matter volume over the one year period, without therapeutic intervention ( FIG. 2 ) 
     Second, a comparison between brain volume and developmental state, suggests that for those subjects diagnosed with MPSIIIA, there is a decrease in DQ consistent with a reduction in total cortical gray mater volume. This reduction was observed in both subjects diagnosed before and after 6 years of age, suggesting the relationship may be independent of disease onset. 
     Clinical Trial—Therapeutic Treatment Via IT Delivery of Recombinant Heparan-N-Sulfatase 
     Clinical trial conducted using, a recombinant heparan-N-sulfatase produced in a human cell line, administered intrathecally (IT) to directly target the CNS. The primary objective was an assessment of safety and tolerability; secondary objectives included assessment of the impact of therapy on cerebrospinal fluid (CSF) heparan sulfate levels, as an indicator of in vivo biological activity. 
     For the study, a total of 12 geographically diverse disease subjects (8 males and 4 females), with a confirmed diagnosis of MPS-IIIA were recruited. Of the 12 patients included, 7 had the classic severe form of MPS IIIA, with a baseline or follow-up developmental quotient less than 50. Each MPS-IIIA subject was required to have a calendar age≧3 years and a developmental age≧1 year (Table 6). 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Patient Demographics and Baseline Characteristics 
               
            
           
           
               
               
               
               
            
               
                   
                 10 mg IT 
                 45 mg IT 
                 90 mg IT 
               
               
                 Characteristics 
                 (N = 4) 
                 (N = 4) 
                 (N = 4) 
               
               
                   
               
               
                 Age. y, median (range) 
                   9.30 
                   4.78 
                   8.09 
               
               
                   
                  (4.76-13.22) 
                  (3.10-23.63) 
                  (3.98-22.39) 
               
               
                 Male/female 
                 3/1 
                 2/2 
                 3/1 
               
               
                 Weight, kg, median 
                  37.15 
                  22.15 
                  31.35 
               
               
                 (range) 
                 (23.9-53.7) 
                 (19.9-76.0) 
                 (18.9-76.7) 
               
               
                 MPS IIIA genotype 
               
               
                 (allele 1/allele 2) 
               
               
                 Missense/ 
                 1 (25.0) 
                 2 (50.0) 
                 0 
               
               
                 unclassifiable 
               
               
                 Missense/frameshift 
                 2 (50.0) 
                 0 
                 0 
               
               
                 Nonsense/nonsense 
                 0 
                 1 (25.0) 
                 0 
               
               
                 Unclassifiable/ 
                 0 
                 0 
                 1 (25.0) 
               
               
                 missense 
               
               
                 Frameshift/frameshift 
                 0 
                 0 
                 1 (25.0) 
               
               
                 Missense/missense 
                 1 (25.0) 
                 1 (25.0) 
                 2 (50.0) 
               
               
                   
               
            
           
         
       
     
     Developmental age was determined by developmental tests administered at the time of screening. The median age for the subjects was 5.5 years (range, 3.0-23). The patient cohort was heterogeneous with respect to age, stage of disease, and disease phenotype, and included 2 pairs of siblings with relatively attenuated disease. All patients were required to have a documented deficiency in sulfamidase activity and; either 2 documented mutations or a normal enzyme activity level of a least 1 other sulfatase (to rule out multiple sulfatase efficiency). The study was designed as an open-label, dose-escalation trial of 3 dose levels (10, 45 and 90 mg) of recombinant Human-N-Sulfatase, administered via an indwelling intrathecal drug delivery device (IDDD) every 28±7 days, for a total of 6 doses. Enrollment was staggered to monitor safety before moving to a higher-dosage group. Accordingly, the first cohort received 10 mg does, the second received 45 mg doses and the third received 90 mg doses. 
     Similar to the Natural History Study, cognitive status was assessed using either the Bayley Scales of Infant Development III (BSID) or Kaufman Assessment Battery for Children (KABC) approach. For both the BSID and KABC methods, a total mental age equivalent (MA) was calculated in months, for every participant. A subject&#39;s developmental quotient (DQ), was determined by dividing a subject&#39;s mental age equivalent by their chronological age in months: DQ(%)=(MA/CA)×100. Developmental analysis were carried out on all 12 subjects. As demonstrated in  FIG. 3 , all 12 subjects with in the three treatment groups (10, 45 and 90 mg) demonstrated a reduction in developmental quotient at the end of the 6 month treatment period, as compared to their respective baseline value. The finds were also evaluated to examine a possible correlation between changes in developmental quotent over time, when compared to a MPS-IIIA subjects calendar age and development stage for non-treatment subjects (Natural History Subjects). The findings suggests that the majority of patients exhibited a decline in developmental quotent, with overall trends among those with classic, severe MPS IIIA resembling those in patients with severe disease participating in the Natural History study ( FIG. 5 ). 
     Brain imaging was performed for each subject using non-contrast MRI. Brain volume for the study, was assessed by evaluating several different anatomic criteria such as: Gray matter volume, White matter volume, Cortical volume, Ventricular+CSF volume, Cerebella volume and Total Brain volume). Brain imaging studies were performed under general anesthesis upon initial enrollment (baseline) and on week 22. Additional studies may be performed on month 12 and month 24 dates. The MRI data was analyzed to evaluate total grey matter volume over the 6 month period of therapeutic intervention. As demonstrated in  FIG. 4 , a reduction in total gray matter volume was observed for each dosage group, over the 6 month treatment period, as compared to their respective baseline value. The finds were also evaluated to examine a possible correlation between changes in brain volume over time, when compared to a MPS-IIIA subjects calendar age and development stage for non-treatment subjects (Natural History Subjects). The findings suggests that the majority of patients exhibited a decline in total grey volume, with overall trends among those with classic, severe MPS IIIA resembling those in patients with severe disease participating in the Natural History study ( FIG. 6 ). 
     Safety and Tolerability 
     Safety and tolerability were assessed by the rate of adverse events (by type and severity), changes in clinical laboratory testing (serum chemistry including liver function tests, hematology, and urinalysis), electrocardiograms, clinical laboratory CSF analysis, and anti-heparan-N-sulfatase antibodies (in CSF and serum). 
     Intrathecal administration of recombinant heparan-N-sulfatase was generally safe and well tolerated. There was no evidence of meningeal inflammation, nor any serious adverse event attributable to recombinant heparan-N-sulfatase. The majority of serious adverse events were brief hospitalizations for revisions of the intrathecal catheter, occurring in 6/12 patients. Increased titers or de novo formation of anti-heparan-N-sulfatase antibodies occurred in 6/12 patients, without associated clinical events. 
     Immunogenicity 
     Immunogenicity was evaluated for all 12 clinical trial subjects using a human Heparan-N-Sulfatase monoclonal antibody in a standard ELISA assay. ELISA analysis was performed on serum collected on weeks 2, 6, 10, 14, 18, 22 and 26 over the 6 month study period. Serum immunoglobulin G (IgG) antibodies against recombinant heparan-N-sulfatase were detected in 6 out of 12 patients ( FIG. 7 ). 
     Pharmacokinetic Analysis 
     Pharmacokinetic analysis of serum rhHNS was performed following the 1st or 6th IT-bolus administration. At week 2 of IT administration, recombinant human HNS (rhHNS) demonstrated biphasic serum concentration-time profiles across the 10, 45, and 90 mg IT dose groups ( FIG. 8A ). The T Max  results indicate a gradual transfer of rhHNS from the CNS to systemic compartment following IT administration. Systemic exposure of rhHNS was dose proportional following the first dose of rhHNS (Week 2) ( FIG. 8A ) but not following the sixth dose (Week 22) ( FIG. 8B ). 
     Efficacy Results: Impact in CSF and Urine GAG HS Levels 
     Heparan sulfate (HS) is the primary accumulating metabolite in Sanfilippo Syndrome Type A. The level of the glycosaminoglycan (GAG) heparan sulfate in CSF over the duration of the study was selected as an important pharmacodynamic endpoint of this study to indicate in vivo activity of rhHNS in the central nervous system. Age-matched non-MPS afflicted individuals were used as controls. CSF levels of GAG HS in patients were elevated at baseline relative to age-matched non-MPS controls, and exhibited marked and persistent declines following the first dose of IT rhHNS. 
     As shown in  FIG. 9 , mean CSF total heparan sulfate levels were reduced at each of the three dose levels, with declines evident following the first dose of IT rhHNS (i.e., observed at week 6, immediately preceding the 2nd dose). The 45 mg and 90 mg doses appeared to be similar in effect on this parameter, and more effective than the 10 mg dose. 
     As shown in  FIG. 2 , urine GAG levels were also reduced at each of the three dose levels, with declines evident following the first dose of IT rhHNS (i.e., observed at week 6, immediately preceding the 2nd dose). The 10 mg and 45 mg doses appeared to be similar in effect on this parameter. The 90 mg dose was initially more effective (e.g., at week 6), although its impact over time was comparable or only slightly better than the 10 mg and 45 mg doses. 
     These results demonstrate that intrathecally administered recombinant HNS enzyme is safe, well tolerated and biologically active. Pharmacokinetics showed dose proportional patterns in peripheral blood. The primarily pharmacodynamic parameter, CSF total heparan sulfate, exhibited declines in response to therapy at all dose levels, with a greater impact observed at the higher dose levels. Most of the reduction occurred after the first dose (Week 6) and then levels remained relatively stable during the remainder of doses. An effect on GAG heparan sulfate levels, in particular, in CSF has central importance in mediating the potential therapeutic benefit of intrathecal administration of recombinant HNS enzyme. Thus, intrathecal enzyme replacement therapy holds promise as an effective therapy for MPSIIIA. 
     Example 2 
     Preliminary Observations of Long-Term Intrathecal Enzyme Replacement Therapy in Patients with Mucopolysaccharidosis Type IIIA (MPSIIIA) 
     As discussed above, MPSIIIA is a rare lysosomal storage disease caused by deficiency of heparan-N-sulfatase, which in turn causes accumulation of heparan sulfate and progressive neurodegeneration. There is no proven therapy for this disease, from which patients usually succumb in their late teens or early twenties. In this example, we present the results of an interim analysis of patients participating in the initial clinical trial and its extension protocol, where patients continued to receive the originally assigned open-label treatment regimen. Measures of disease progression included cognitive status, assessed by standardized tests and expressed as a developmental quotient (DQ), and total cortical gray matter volume, derived from automated analysis of serial brain MRIs. Four patients were enrolled at each of 3 dose levels, of whom 11 had entered the extension trial at the time of analysis. One patient withdrew from the extension trial after 3 months. The patient population was heterogeneous in terms of age (median 5.5 years, range 3.0 to 23), disease stage and disease phenotype. Baseline DQ data could not be obtained in 2 patients due to lack of cooperation with testing. Seven patients suffered from the classical severe form of MPSIIIA, and all of these had baseline or follow up DQs less than 50%. Five patients (including 2 sibling pairs) exhibiting relatively attenuated disease. Owing to the staggered enrollment in the initial dose escalation study, the duration of patient follow-up was variable, ranging from 6 months to 24 months. The majority of patients exhibited declines in DQ, with the overall trends indistinguishable from those observed in a parallel natural history study. Similarly, declines in cortical grey matter volume were observed in all but two patients, the exceptions having markedly attenuated disease. These preliminary observations must be interpreted with caution, owing to the small and heterogeneous study population, variable duration of follow-up and lack of concurrent controls. These results also suggest that in patients with the classical severe form of MPSIIIA, IT ERT may have to be initiated before DQ has declined to 50% to be effective. 
     Equivalents 
     Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to embodiments of the inventions described herein. The scope of the present invention is not intended to be limited to the above Description, but rather is as set forth in the following claims. 
     The articles “a” and “an” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to include the plural referents. Claims or descriptions that include “or” between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The invention includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The invention also includes embodiments in which more than one, or the entire group members are present in, employed in, or otherwise relevant to a given product or process. Furthermore, it is to be understood that the invention encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, descriptive terms, etc., from one or more of the listed claims is introduced into another claim dependent on the same base claim (or, as relevant, any other claim) unless otherwise indicated or unless it would be evident to one of ordinary skill in the art that a contradiction or inconsistency would arise. Where elements are presented as lists, (e.g., in Markush group or similar format) it is to be understood that each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should be understood that, in general, where the invention, or aspects of the invention, is/are referred to as comprising particular elements, features, etc., certain embodiments of the invention or aspects of the invention consist, or consist essentially of, such elements, features, etc. For purposes of simplicity those embodiments have not in every case been specifically set forth in so many words herein. It should also be understood that any embodiment or aspect of the invention can be explicitly excluded from the claims, regardless of whether the specific exclusion is recited in the specification. The publications, websites and other reference materials referenced herein to describe the background of the invention and to provide additional detail regarding its practice are hereby incorporated by reference.