The present invention provides methods to determine whether a patient with Pompe disease will benefit from treatment with a specific pharmacological chaperone. The present invention exemplifies several cell-based in vitro, ex vivo and in vivo methods for determining the responsiveness of acid α-glucosidase (GAA) variants to a pharmacological chaperone such as 1-deoxynojirimycin (DNJ). An in situ application of the method also provides a way to identify Pompe patients and obtain useful information on dosing these pharmacological chaperones. A novel method to accurately measure GAA activity in tissue homogenate samples is also a subject of the present invention.
Pompe disease is an inherited metabolic disorder that is one of approximately forty lysosomal storage disorders (LSDs). These LSDs are a group of autosomal recessive diseases caused by the accumulation of cellular glycosphingolipids, glycogen, or mucopolysaccharides, due to defective hydrolytic enzymes. Examples of lysosomal disorders include but are not limited to Gaucher disease (Beutler et al., The Metabolic and Molecular Bases of Inherited Disease. 8th ed. 2001 Scriver et al., ed. pp. 3635-3668, McGraw-Hill, New York), GM1-gangliosidosis (id. at pp 3775-3810), fucosidosis (The Metabolic and Molecular Bases of Inherited Disease 1995. Scriver, C. R., Beaudet, A. L., Sly, W. S. and Valle, D., ed pp. 2529-2561, McGraw-Hill, New York), mucopolysaccharidoses (id. at pp 3421-3452), Pompe disease (id. at pp. 3389-3420), Hurler-Scheie disease (Weismann et al., Science. 1970; 169, 72-74), Niemann-Pick A and B diseases, (The Metabolic and Molecular Bases of Inherited Disease 8th ed. 2001. Scriver et al. Ed. pp 3589-3610, McGraw-Hill, New York), and Fabry disease (Id. at pp. 3733-3774).
The specific pharmacological chaperone (“SPC”) strategy has been demonstrated for numerous enzymes involved in lysosomal storage disorders as in U.S. Pat. Nos. 6,274,597, 6,583,158, 6,589,964, 6,599,919, and 6,916,829 to Fan et al., which are incorporated herein by reference in their entirety. For example, a small molecule derivative of galactose, 1-deoxygalactonojirimycin (DGJ), a potent competitive inhibitor of the mutant Fabry enzyme α-galactosidase A (α-Gal A: GLA), effectively increased in vitro stability of the human mutant α-Gal A (R301Q) at neutral pH, and it enhanced the mutant enzyme activity in lymphoblasts established from Fabry patients with R301Q or Q279E mutations. Furthermore, oral administration of DGJ to transgenic mice overexpressing mutant (R301Q) α-Gal A substantially elevated the enzyme activity in major organs (Fan et al. Nature Med. 1999; 5: 112-115). Similar rescue of glucocerebrosidase (acid β-glucosidase, GBA) from Gaucher patient cells has been described using another iminosugar, isofagomine (IFG), and its derivatives, described in U.S. Pat. No. 6,916,829, and using other compounds specific for glucocerebrosidase (described in pending U.S. patent application Ser. Nos. 10/988,428, and 10/988,427, both filed Nov. 12, 2004). U.S. Pat. No. 6,583,158, described above, discloses several small molecule compounds that would be expected to stabilize mutant GAAs and increase cellular levels of the enzyme for the treatment of Pompe disease, including 1-deoxynojirimycin (DNJ), α-homonojirimycin, and castanospermine.
However, as indicated above, successful candidates for SPC therapy must have a mutation which results in the production of an enzyme that has the potential to be stabilized and folded into a conformation that permits trafficking out of the ER. Mutations which severely truncate the enzyme, such as nonsense mutations, or mutations within the catalytic domain which prevent binding of the chaperone, will not likely be “rescuable” or “enhanceable” using SPC therapy. However, it is often difficult to predict responsiveness of specific mutations even if they are outside the catalytic site and requires empirical experimentation. Moreover, since WBCs only survive for a short period of time in culture (ex vivo), screening for SPC enhancement of GAA is difficult.
In order to apply SPC therapy effectively, a broadly applicable, fast and efficient method for screening patients for responsiveness to SPC therapy needs to be adopted prior to initiation of treatment. Thus, there remains in the art a need for relatively non-invasive methods to rapidly assess the potential for enzyme enhancement via SPCs prior to making treatment decisions, for both cost and emotional benefits to the patient.
The present invention provides in vitro and ex vivo assays to evaluate GAA activity in a model mammalian expression system and freshly-isolated lymphocytes derived from patients with Pompe disease in the presence or absence of a SPC, in order to determine whether a patient is a candidate for SPC therapy and, optionally, to evaluate the extent of successful treatment. The present invention also includes the basis for evaluation of SPC as a treatment option for other protein abnormalities and/or enzyme deficiencies (e.g. protein deficiencies resulting from cystic fibrosis. α-1-antitrypsin deficiency, familial hypercholesterolemia. Fabry disease, and Alzheimer's disease. For additional protein deficiencies, see U.S. patent application publication 20060153829, herein incorporated by reference in its entirety.).
One aspect of the present application, relates to an improved method of diagnosing Pompe disease by determining, GAA activity in isolated leukocytes (e.g. T cells) from patients suspected of having Pompe disease.
A second aspect of the present application provides an improved method of diagnosing Pompe disease by determining GAA activity in lymphoblast and/or fibroblast cell lines derived from patients suspected of having Pompe disease.
The present invention also provides methods of measuring GAA enzyme activity in situ in freshly isolated leukocytes to evaluate the response of GAA to SPC therapy and information about the effectiveness of various dosing regimens. For example, the present application further provides methods for evaluating, an in vivo GAA response to SPC therapy after a treatment period.
The present invention also provides diagnostic kits containing the components required to perform assays of the present application.
The present invention further provides a method to accurately measure GAA activity in Tissue homogenate samples.
The present invention provides several assays to allow the accurate determination of whether an SPC enhances enzyme activity from cells derived from patients with Pompe disease. These assays permit a determination of whether the patient will be a candidate for SPC therapy.
The new ex vivo assay is sufficiently sensitive and can be performed on freshly isolated leukocytes to obtain pertinent information on the whether a patient is amenable to SPCs. This assay utilizes various substrates (e.g., fluorogenic substrates known in the art, natural glycogen substrate, or novel fluorogenic substrates) and is more sensitive than the current white blood cell (WBC) assay.
The isolated leukocytes, specifically B-lymphocytes, can be immortalized via infection with Epstein-Barr virus (EBV) to generate a replenishable lymphoblast cell lines for additional characterization. The lymphoblast cell lines provide for a new in vitro assay that is non-invasive, and also provides for a very reliable method for rapidly evaluating all known disease-causing mutations and for determining whether a SPC therapy will be effective in a patient with specific mutations.
In conjunction with genotyping, both assays provide a method for determining whether newly discovered GAA mutations (such as spontaneous mutations) cause the GAA to misfold and, are “rescuable” using SPCs.
According to the present invention. GAA enzyme activity can be measured in lysosomes in freshly isolated leukocytes or lymphoblast or fibroblast cell lines in situ to provide data on whether a patient would be responsive to SPCs. This assay can also be used to used to develop and optimize an appropriate dosing regimen for an individual patient by determining an effective dose or dosing regimens for increasing the activity of mutant GAA enzyme levels and activity in lysosomes.
The in vivo assay of the invention is a minimally-invasive method that measures GAA activity in freshly-isolated leukocytes to determine whether a patient responds to SPCs while on the test drug to qualify or dis-qualify a potential patient for SPC therapy.
The present invention further provides a method to accurately measure GAA activity in Tissue homogenate samples.
Measuring GAA activity in 1-deoxynojirimycin (DNJ) treated samples can be difficult since residual levels of this compound can inhibit GAA and lead to reduced enzyme activity measurements. The instant invention provides a new method to overcome this inhibition problem and enable accurate measurements of GAA activity in tissue homogenate samples. This method utilizes concanavalin A (Con A), a lectin protein from jack bean that binds glycoproteins via their terminal glucose and/or mannose carbohydrates. GAA, like the vast majority of other proteins that are synthesized in the endoplasmic reticulum (ER)_, contain core (also called N-linked) carbohydrates and therefore also binds this lectin. One embodiment of the invention is a method that utilizes Con A, which is covalently coupled to an insoluble matrix (e.g., agarose or sepharose) which can be sedimented by centrifugation and enable efficient washout of 1-deoxynojirimycin (DNJ) prior to GAA activity measurements. Moreover, since Con A only binds a glycoprotein via the carbohydrates, there is sufficient distance between the Con A-bound N-glycans and the enzyme active site and therefore still allows for substrate binding and catalysis. This method can be used to measure GAA activity in a number of different cell types (including wild-type and patient derived primary peripheral leukocytes, lymphoblasts, fibroblasts, myoblasts, and in transiently transfected COS-7 cells) as well as tissues homogenates (including multiple skeletal and cardiac muscles, brain, skin, etc.). Hence, this method is useful for measuring GAA activity in a broad range of cells and tissues.
Furthermore, the use of Con A can actually improve the sensitivity and accuracy of the assay by concentrating glycoproteins on a small volume. More specifically, conventional assays are performed at relatively small volumes (e.g. 100 microliters) and the amount of sample that can be added is typically only a portion of this total volume (e.g. less than half) because substrate and other reagents are added into the assay. This becomes problematic with patient-derived samples that have low residual activity because one cannot add enough sample (volume) into the assay and the signals can be only slightly above (or at or below) background which makes the data less accurate. By using Con A, essentially all of the glycoproteins can be captured, including the enzyme of interest such as the lysosomal enzymes, onto the small volume of the beads. Hence, instead of assaying only 50 microliters worth of sample due to limited volume constraints using the conventional methodology, this new method enables the capture of 1000 microliters worth of sample onto a small volume (e.g. 25 microliters) of the Con A beads (due to the beads high binding capacity) and assay these beads directly. The net result is the effective “concentration” of sample for better signals which in turn yields much more accurate enzyme activity measurements. This improved assay is particularly useful when working with patient lymphoblasts which often have 10-fold lower enzyme activity than fibroblasts and other cell types.
The terms used in this specification generally have their ordinary meanings in the art, within the context of this invention and in the specific context where each term is used. Certain terms are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner in describing the compositions and methods of the invention and how to make and use them.
The term “Pompe disease” also referred to as acid maltase deficiency, glycogen storage disease type II (GSDII), and glycogenosis type II, is a genetic lysosomal storage disorder characterized by mutations in the GAA gene which metabolizes glycogen. As used herein, this term includes infantile, juvenile and adult-onset types of the disease.
“Acid α-glucosidase or α-glucosidase or GAA” is a lysosomal enzyme which hydrolyzes alpha-1,4- and alpha-1,6-linked-D-glucose polymers present in glycogen, maltose, and isomaltose. Alternative names are as follows: glucoamylase: 1,4-α-D-glucan glucohydrolase; amyloglucosidase; gamma-amylase: and exo-1,4-α-glucosidase, and gamma-amylase. The human GAA gene has been mapped to chromosome 17q25.2-25.3 and has nucleotide and amino acid sequences depicted in GenBank Accession No. Y00839. Mutations resulting in misfolding or misprocessing of the GAA enzyme include T1064C (which changes Leu in position 355 into Pro) and C2104T (which substitutes Arg 702 into Cys) (Montalvo et at. Mol Genet Metab. 2004: 81(3): 203-8). In addition, Hermans et al. (Human Mutation 2004; 23: 47-56) describe a list of GAA mutations which affect maturation and processing of the enzyme. Such mutations include Leu405Pro and Met519Thr. In one non-limiting embodiment, the method of the present invention is expected to be useful for mutations that cause unstable folding of α-glucosidase in the ER.
The term “wild-type activity” refers to the normal physiological function of a GAA in a cell. For example. GAA activity includes folding and trafficking from the ER to the lysosome, with the concomitant ability to hydrolyze α-1,4- and α-1.6-linked-D-glucose polymers present in glycogen, maltose, and isomaltose.
The term “wild-type GAA” refers to the nucleotide sequences encoding GAA, and polypeptide sequences encoded by the aforementioned nucleotide sequences (human GAA GenBank Accession No. Y00839, and any other nucleotide sequence that encodes GAA polypeptide (having the same functional properties and binding affinities as the aforementioned polypeptide sequences), such as allelic variants in normal individuals, that have the ability to achieve a functional conformation in the ER, achieve proper localization within the cell, and exhibit wild-type activity (e.g., hydrolysis of glycogen).
A “patient” refers to a subject who has been diagnosed with a particular disease. The patient may be human or animal. A “Pompe disease patient” refers to an individual who has been diagnosed with Pompe disease and has a mutated GAA as defined further below.
As used herein the term “mutant α-glucosidase” or “mutant GAA” refers to an α-glucosidase polypeptide translated from a gene containing a genetic mutation that results in an altered α-glucosidase amino acid sequence. In one embodiment, the mutation results in an α-glucosidase protein that does not achieve a native conformation under the conditions normally present in the ER, when compared with wild-type α-glucosidase or exhibits decreased stability or activity as compared with wild-type α-glucosidase. This type of mutation is referred to herein as a “conformational mutation,” and the protein hearing such a mutation is referred as a “conformational mutant.” The failure to achieve this conformation results in the α-glucosidase protein being degraded or aggregated, rather than being transported through a normal pathway in the protein transport system to its native location in the cell or into the extracellular environment. In some embodiments, a mutation may occur in a non-coding part of the gene encoding α-glucosidase that results in less efficient expression of the protein, e.g., a mutation that affects transcription efficiency, splicing efficiency. mRNA stability, and the like. By enhancing the level of expression of wild-type as well as conformational mutant variants of α-glucosidase, administration of an α-glucosidase pharmacological chaperone can ameliorate a deficit resulting from such inefficient protein expression. Alternatively, for splicing mutants or nonsense mutants which may accumulate in the ER, the ability of the chaperone to bind to and assist the mutants in exiting the ER, without restoring lysosomal hydrolase activity, may be sufficient to ameliorate some cellular pathologies in Pompe patients, thereby improving symptoms.
Exemplary mutations of GAA include the following: D645E (Lin et al., Zhonghua Min Guo Xiao Er Ke Yi Xue Hui Za Zhi. 1996; 37(2): 115-21); D645H (Lin et al., Biochem Biophys Res Commun. 1995 17; 208(2): 886-93); R224W, S619R, and R660H (New et al. Pediatr Neurol. 2003; 29(4): 284-7); T1064C and C2104T (Montalvo et al., Mol Genet Metab. 2004:81(3): 203-8); D645N and L901Q (Kroos et al., Neuromuscul Disord. 2004; 14(6): 371-4); G219R, E262K, M408V (Fernandez-Hojas et al., Neuromuscul Disord. 2002; 12(2): 159-66); G309R (Kroos et al., Clin Genet. 1998; 53(5): 379-82); D645N, G448S, R672W, and R672Q (Huie et al., Biochem Biophys Res Commun. 1998; 27:244(3): 921-7); P545L (Hermans et al. Hum Mol. Genet. 1994; 3(12): 2213-8); C647W (Huie et al. Huie et al., Hum Mol. Genet. 1994; 3(7): 1081-7); G643R (Hermans et al. Hum Mutat. 1993; 2(4): 268-73); M318T (Zhong et al., Am J Hum Genet. 1991; 49(3): 635-45); E521K (Hermans et al., Biochem Biophys Res Commun. 1991; 179(2): 919-26); W481R (Raben et al. Hum Mutat. 1999:13(1): 83-4); and L552P and G549R (unpublished data).
Splicing mutants include IVS1AS. T>G, −13 and IVS8+1G>A).
Additional GAA mutants have been identified and are known in the art. Conformational mutants are readily identifiable by one of ordinary skill in the art.
Mutations which impair folding, and hence, trafficking of GAA, can be determined by routine assays well known in the art, such as pulse-chase metabolic labeling with and without glycosidase treatment to determine whether the protein enters the Golgi apparatus, or fluorescent immunostaining for GAA localization within the cell. Wild-type GAA is secreted as a 110 kD precursor which then converts to the mature GAA of 76 kD via and intermediate of 95 kD.
Such functionality can be tested by any means known to establish functionality of such a protein. For example, assays using fluorescent substrates such as 4-methyl umbeliferryl-α-D-glueopyranoside can be used to determine GAA activity. Such assays are well known in the art (see e.g., Hermans et al., above).
As used herein, the term “specific pharmacological chaperone” (“SPC”) or “pharmacological chaperone” refers to any molecule including a small molecule, protein, peptide, nucleic acid, carbohydrate, etc. that specifically binds to a protein and has one or more of the following effects: (i) enhances the formation of a stable molecular conformation of the protein; (ii) induces trafficking of the protein from the ER to another cellular location, preferably a native cellular location, i.e., prevents ER-associated degradation of the protein; (iii) prevents aggregation of misfolded proteins: and/or (iv) restores or enhances at least partial wild-type function and/or activity to the protein. A compound that specifically binds to e.g. GAA, means that it binds to and exerts a chaperone effect on GAA and not a generic group of related or unrelated enzymes. More specifically, this term does not refer to endogenous chaperones, such as BiP, or to non-specific agents which have demonstrated non-specific chaperone activity against various proteins, such as glycerol. DMSO or deuterated water, i.e., chemical chaperones (see Welch et al., Cell Stress and Chaperones 1996; 1(2): 109-115; Welch et al., Journal of Bioenergetics and Biomembranes 1997; 29(5): 491-502: U.S. Pat. No. 5,900,360; U.S. Pat. No. 6,270,954; and U.S. Pat. No. 6,541,195). In the present invention, the SPC may be a reversible competitive inhibitor.
A “competitive inhibitor” of an enzyme can refer to a compound which structurally resembles the chemical structure and molecular geometry of the enzyme substrate to bind the enzyme in approximately the same location as the substrate. Thus, the inhibitor competes for the same active site as the substrate molecule, thus increasing the Km. Competitive inhibition is usually reversible if sufficient substrate molecules are available to displace the inhibitor, i.e., competitive inhibitors can bind reversibly. Therefore, the amount of enzyme inhibition depends upon the inhibitor concentration, substrate concentration, and the relative affinities of the inhibitor and substrate for the active site.
Following is a description of some (SPC) specific pharmacological chaperones contemplated by this invention:
1-deoxynojirimycin (DNJ) refers to a compound having the following structures:
This term includes both the free base and any salt forms.
Still other SPCs for GAA are described in U.S. Pat. No. 6,599,919 to Fan et al., and U.S. Patent Application Publication US 20060264467 to Mugrage et al. and include N-methyl-DNJ, N-propyl-DNJ, N-butyl-DNJ, N-pentyl-DNJ, N-hexyl-DNJ, N-heptyl-DNJ, N-octyl-DNJ, N-nonyl-DNJ. N-methylcyclopropyl-DNJ, N-methylcyclopentyl-DNJ, N-2-hydroxyethyl-DNJ, and 5-N-carboxypentyl DNJ.
In one embodiment, the SPC is selected from N-methylcyclopropyl-DNJ and N-methylcyclopentyl-DNJ.
As used herein, the term “specifically binds” refers to the interaction of a pharmacological chaperone with a protein such as GAA, specifically, an interaction with amino acid residues of the protein that directly participate in contacting the pharmacological chaperone. A pharmacological chaperone specifically binds a target protein, e.g., GAA, to exert a chaperone effect on GAA and not a generic group of related or unrelated proteins. The amino acid residues of a protein that interact with any given pharmacological chaperone may or may not be within the protein's “active site.” Specific binding can be evaluated through routine binding assays or through structural studies, e.g. co-crystallization. NMR, and the like. The active site for GAA is the substrate binding site.
“Deficient GAA activity” refers to GAA activity in cells from a patient which is below the normal range as compared (using the same methods) to the activity in normal individuals not having or suspected of having Pompe or any other disease (especially a blood disease).
As used herein, the terms “enhance GAA activity” or “increase GAA activity” refer to increasing the amount of GAA that adopts a stable conformation in a cell contacted with a pharmacological chaperone specific for the GAA, relative to the amount in a cell (preferably of the same cell-type or the same cell. e.g. at an earlier time) not contacted with the pharmacological chaperone specific for the GAA. This term also refers to increasing the trafficking of GAA to the lysosome in a cell contacted with a pharmacological chaperone specific for the GAA, relative to the trafficking of GAA not contacted with the pharmacological chaperone specific for the protein. These terms refer to both wild-type and mutant GAA. In one embodiment, the increase in the amount of GAA in the cell is measured by measuring the hydrolysis of an artificial substrate in lysates from cells that have been treated with the SPC. An increase in hydrolysis is indicative of increased GAA activity.
The term “GAA activity” refers to the normal physiological function of a wild-type GAA in a cell. For example, GAA activity includes hydrolysis of alpha-1,4- and alpha-1.6-linked-D-glucose polymers present in glycogen, maltose, and isomaltose.
A “responder” is an individual diagnosed with Pompe disease and treated according to the presently claimed method who exhibits an improvement in, amelioration, or prevention of one or more clinical symptoms, or improvement or reversal of one or more surrogate clinical markers that are indicators of disease pathology. Symptoms or markers of Pompe disease include but are not limited to decreased GAA tissue activity: cardiomyopathy; cardiomegaly; progressive muscle weakness, especially in the trunk or lower limbs; profound hypotonia; macroglossia (and in some cases, protrusion of the tongue); difficulty swallowing, sucking, and/or feeding; respiratory insufficiency; hepatomegaly (moderate): laxity of facial muscles; areflexia; exercise intolerance; exertional dyspnea; orthopnea; sleep apnea; morning headaches; somnolence; lordosis and/or scoliosis: decreased deep tendon reflexes; lower hack pain; and failure to meet developmental motor milestones.
The dose that achieves one or more of the aforementioned responses is a “therapeutically effective dose.”
The phrase “pharmaceutically acceptable” refers to molecular entities and compositions that are physiologically tolerable and do not typically produce untoward reactions when administered to a human. Preferably, as used herein, the term “pharmaceutically acceptable” means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopoeia or other generally recognized pharmacopoeia for use in animals, and more particularly in humans. The term “carrier” refers to a diluent, adjuvant, excipient, or vehicle with which the compound is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils. Water or aqueous solution saline solutions and aqueous dextrose and glycerol solutions are preferably employed as carriers, particularly for injectable solutions. Suitable pharmaceutical carriers are described in “Remington's Pharmaceutical Sciences” by E. W. Martin. 18th Edition, or other editions.
As used herein, the term “isolated” means that the referenced material is removed from the environment in which it is normally found. Thus, an isolated biological material can be free of cellular components, i.e., components of the cells in which the material is found or produced. In the case of nucleic acid molecules, an isolated nucleic acid includes a PCR product, an mRNA band on a gel, a cDNA, or a restriction fragment. In another embodiment, an isolated nucleic acid is preferably excised from the chromosome in which it may be found, and more preferably is no longer joined to non-regulatory, non-coding regions, or to other genes, located upstream or downstream of the gene contained by the isolated nucleic acid molecule when found in the chromosome. In yet another embodiment, the isolated nucleic acid lacks one or more introns. Isolated nucleic acids include sequences inserted into plasmids, cosmids, artificial chromosomes, and the like. Thus, in a specific embodiment, a recombinant nucleic acid is an isolated nucleic acid. An isolated protein may be associated with other proteins or nucleic acids, or both, with which it associates in the cell, or with cellular membranes if it is a membrane-associated protein. An isolated organelle, cell, or tissue is removed from the anatomical site in which it is found in an organism. An isolated material may be, but need not be, purified.
The terms “about” and “approximately” shall generally mean an acceptable degree of error for the quantity measured given the nature or precision of the measurements. Typical, exemplary degrees of error are within 20 percent (%), preferably within 10%, and more preferably within 5% of a given value or range of values. Alternatively, and particularly in biological systems, the terms “about” and “approximately” may mean values that are within an order of magnitude, preferably within 10- or 5-fold, and more preferably within 2-fold of a given value. Numerical quantities given herein are approximate unless stated otherwise, meaning that the term “about” or “approximately” can be inferred when not expressly stated.
To easily determine whether SPC therapy will be a viable treatment for Pompe patients, non-invasive DNJ rescue assay of GAA activity in lymphobasts. WBCs, or subsets of WBCs, from Pompe patients was developed.
In one embodiment, the diagnostic method of the present invention involves isolating leukocytes (mostly B- and T-lymphocytes) from blood specimens from Pompe patients (or patients suspected of having Pompe disease). In another embodiment, the diagnostic method of the present invention involves establishing lymphoblast cell cultures from freshly-isolated B-lymphocytes for longer-term studies. Both cell model systems are then treated with or without an SPC, e.g. DNJ, lysed and assayed for the enhancement (i.e. increase) of endogenous GAA activity to determine if a patient will likely respond to SPC therapy (i.e. the patient will be a “responder”).
This embodiment can be carried out as follows.
The WBCs are prepared using standard techniques, e.g. collection, centrifugation, separation, and washing. More specifically, they can be prepared according to the following steps:
In one embodiment, lymphocyte cell cultures are established and expanded by stimulation with a mitogenic as follows:
It is noted that one of ordinary skill in the art will be able to ascertain appropriate amounts of T cell stimulatory cytokines or mitogens, although typically such agents are added at amounts from between about 1 ng/ml and about 25 ng/ml (or about 100 U/ml) for cytokines. For mitogens, concentrations range from about 10 ng/ml to about 10 μg/ml for mitogens with most being effective in the low μg/ml range.
Lymphoblastoid cell lines (LCLs) are leukocyte cultures (primarily B cells) that have been transformed with the Epstein-Barr Virus (EBV) to produce proliferative suspension cultures. Because well established LCLs can be very fast-growing (even those with genetic and metabolic disorders), their density must be carefully controlled to prevent overcrowding over an extended period. In one non-limiting embodiment, the following protocol details cell seeding density, treatment with a test compound, treatment compound washout, lysing, and assaying of LCLs for the measurement of acid α-glucoside (GAA) with the test compound.
In one embodiment, T cells or lymphoblasts isolated above (e.g. approximately 2.5×106) are grown in culture medium (preceded by thawing if they are frozen), in an appropriate culture vessel in the absence or presence of the SPC, e.g., DNJ, for enough time to evaluate the change in GAA activity. e.g., 2 or 3 days for T-cells and 5 days for lymphoblasts. Doses of DNJ expected to enhance GAA in T cells are in a range from about 2 nM to about 150 μM, preferably about 1 μM to 100 μM, and more preferably about 5 μM to 50 μM. In one specific embodiment, DNJ is added at about 20 μM. Doses of DNJ expected to enhance GAA in lymphoblasts are in a range from about 2 nM to about 300 μM, preferably about 1 μM to 100 μM, and more preferably about 5 μM to 50 μM. In one specific embodiment. DNJ is added at about 30 μM. Cells can be harvested by centrifugation and washed twice with PBS. Pellets can be stored frozen at −80° C. until assayed for enzyme activity.
Cells are then lysed by the addition of lysis buffer, which contains 150 mM NaCl, 25 mM Bis-Tris and 0.1% Triton-X100 (or deionized water) and physical disruption (pipetting, vortexing and/or agitation, and/or sonication) at room temperature or on ice, followed by pooling of the lysates on ice, then splitting the pooled lysate into small aliquots and freezing.
The lysates can be thawed immediately prior to the assay and should be suspended by use of a vortex mixer and sonicated prior to addition to appropriate wells e.g., in a microplate. 4-methyl umbeliferryl-α-D-glucopyranoside (4MU-alphaGlc), or other appropriate labeled DNJ substrate, is then added and the plate is gently mixed for a brief period of time, covered, and incubated at 37° C. for a sufficient time for substrate hydrolysis, usually about 1 hour. To stop the reaction. NaOH-glycine buffer (alternatively sodium carbonate), pH 10.7, is added to each well and the plate is read on a fluorescent plate reader (e.g. Wallac 1420 Victor™ or similar instrument). Excitation and emission wavelengths were customarily set at 355 nm and 460 nm, respectively. One unit of enzyme activity is defined as the amount of enzyme that catalyzes the hydrolysis of 1 nmole of 4-methylumbelliferone per hour. For each patient sample at least three normal samples should be tested concurrently.
Various modifications of this assay will be readily ascertainable to one of ordinary skill in the art. Examples of artificial substrates that can be used to detect GAA activity include but are not limited to 4MU-alphaGlc. Obviously, only substrates that can be cleaved by human GAA are suitable for use. It is noted that while use of a fluorogenic substrate is preferred, other methods of determining GAA activity are contemplated for use in the method, including using chromogenic substrates or immunoquantification techniques.
In an alternative embodiment, the ability of a SPC to enhance the activity of GAA in a lymphoblast cell line (LCL) can be determined as described in the following, non-limiting example:
Seeding
Treatment with Test Compound
Overnight Compound Washout
Cell Lysis
Assay
Protein Assay (micro-BCA)
GAA Activity Assay
Diagnosis and Prognosis. The T cell or lymphoblast assay can be easily modified for use as a diagnostic assay to diagnose Pompe disease by simply eliminating the step of culturing the T cells or lymphoblasts in the presence of DM prior to performing the enhancement assay. The activity of GAA in T cells or lymphoblast established from an individual suspected of having Pompe disease can instead be quantitated using T cells or lymphoblast from a normal individual as a control. Moreover, both GAA activity and SPC enhancement assays can be performed almost simultaneously using the same T cells or lymphoblasts derived from one patient sample. While not being bound thereby, it is believed that since T cells may express more GAA (GAA in normal T cells as compared with WBCs is much higher), it will be easier to confirm with more certainty whether a patient has GAA activity below the normal range because the margin of error will be smaller. Accordingly, use of the cell assay could potentially prevent misdiagnoses.
In addition, the modified assay also can be used to periodically monitor the progress of patients in whom SPC therapy was initiated to confirm that GAA activity remains increased relative to prior to treatment initiation.
In a second embodiment. WBCs are evaluated for GAA enhancement by an SPC in vivo. In this embodiment, GAA activity in WBCs derived from patients is assessed prior to SPC administration, in order to obtain a baseline value. Patients are then administered DNJ daily 2500 mg/day) for a sufficient time period, e.g., about 10 days to about 2 weeks, followed by extraction of blood and determination of changes in GAA activity from the baseline value. Culturing the cells either prior to, or following administration, is not required.
The dose and dosing regimen of DNJ administration during the in vivo evaluation period may vary depending on the patient since there is so much heterogeneity among mutations, and depending on the patient's residual GAA activity. As a non-limiting example, the doses and regimens expected to be sufficient to increase GAA in most “rescuable” individuals is as described in U.S. Provisional Application 61/028,105, filed Feb. 12, 2008, herein incorporated by reference in its entirety.
Administration of DNJ according to the present invention may be in a formulation suitable for any route of administration, but is preferably administered per os in an oral dosage form such as a tablet, capsule or solution. For this assay, in the case of oral administration, it is preferred that the patient be administered the DNJ without food (e.g., no food 2 hours before and for 2 hours after dosing) since bioavailability may be lower if taken with food, thereby risking inaccurate results.
Patients who are on other therapies, such as ERT, may wish to cease treatment for at least about 28 days prior to the in vivo assay to ensure the most accurate results.
WBCs are isolated and separated as described above for the T cell in vitro assay. However, no RPMI media or DMSO is to be added to the pellets prior to freezing (as per step 5 in the section entitled “White Blood Cell Separation” above).
Pellets are thawed on ice and cells are then lysed by the addition of lysis buffer and physical disruption (such as by use of a vortex mixer and agitation, and/or sonication at room temperature) for a sufficient time, followed by pooling of the lysates in a polypropylene tube on ice, then splitting of the pooled lysate into aliquots for freezing.
The WBC lysates are then thawed on ice and mixed (again, by sonication and/or vortexing). Samples of each lysate, as well as standards and negative controls, are then added to appropriate wells in e.g. a 24 or 96 well microplate. A labeled substrate, such as, for example, 4MU-alphaGlc in citrate/phosphate buffer, pH 4.6, is then added to all wells, and incubation for a short time at ambient temperature. The plate is then mixed briefly and incubated at 37° C. for a sufficient time period to permit substrate hydrolysis, e.g., about 1 hour. After the sufficient time period, the reaction is stopped by the addition of stop buffer and the plate is read on a fluorescent plate reader (e.g. Wallac 1420 Victor3™) to determine enzyme activity per well.
Various modifications of this assay will be readily ascertainable to one of ordinary skill in the art. Examples of artificial substrates that can be used to detect GAA activity include but are not limited to 4MU-alphaGlc. Obviously, only substrates that can be cleaved by human GAA are suitable for use. It is noted that while use of a fluorogenic substrate is preferred, other methods of determining GAA activity are contemplated for use in the method, including using chromogenic substrates or immunoquantification techniques.
The criteria for determining eligibility for SPC therapy depends on the patient's residual enzyme activity at baseline. i.e., the activity determined in the untreated T cells or lymphoblast in the in vitro assay, or the activity in the WBCs prior to SPC administration in the in vivo assay. The lower the residual activity, the greater enhancement necessary in order for a patient to be considered a likely responder to treatment.
In one embodiment, the criteria for determining eligibility for the in vitro assay are as follows:
In one embodiment, for the in vivo assay, the following criteria are used to determine eligibility criteria:
In an alternative embodiment, an increase in activity of at least about 20% in the cells cultured with SPC over the activity in the cells not cultured with SPC, in either the in vitro or in vivo assay, may be indicative that the patient will have a clinically relevant (therapeutically effective) response to SPC therapy.
This discovery provides a method for improving the diagnosis of and facilitating clinical treatment decisions for Pompe disease in particular, and lysosomal storage disease in general. Moreover, this method can be extended to a wide range of genetically defined diseases in appropriate cell types. This class of disease includes the other lysosomal storage disorders. Cystic Fibrosis (CFTR) (respiratory or sweat gland epithelial cells), familial hypercholesterolemia (LDL receptor; LPL-adipocytes or vascular endothelial cells), cancer (p53: PTEN-tumor cells), and amyloidoses (transthyretin) among others.
The present invention also provides for a commercial diagnostic test kit in order to make therapeutic treatment decisions. The kit provides all materials discussed above and in the Example below, for preparing and running each assay in one convenient package, with the obvious exception of patient blood, optionally including instructions and an analytic guide.
As one non-limiting example, a kit for evaluating GAA activity may contain, at a minimum:
In one embodiment, the SPC is supplied in dry form, and will be re-constituted prior to addition.
In another embodiment, the invention provides a it for the diagnosis of Pompe disease. In this embodiment, the SPC is not included in the kit and the instructions are tailored specifically to diagnosis.
Patients that test positive for enzyme enhancement with an SPC can then be treated with that agent, whereas patients who do not display enzyme enhancement with a specific agent can avoid treatment which will save money and prevent the emotional toll of not responding to a treatment modality.
The present invention is further described by means of the examples, presented below. The use of such examples is illustrative only and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to any particular preferred embodiments described herein. Indeed, many modifications and variations of the invention will be apparent to those skilled in the art upon reading this specification. The invention is therefore to be limited only by the terms of the appended claims along with the full scope of equivalents to which the claims are entitled.
The present Example provides an in vitro diagnostic assay to determine a Pompe patient's responsiveness to a specific pharmacological chaperone, wherein the response of patient derived lymphoblasts to DNJ was determined ex vivo. This assay may also be performed using patient derived fibroblasts.
The ex vivo study included 14 males and 12 females with late-onset GSD-II. 3 male juveniles with GSD-II (5, 11, and 12 yrs), and 1 female infant (1 yr) with GSD-II. Patients ranged in age from 1 to 72 years; 19 of 30 patients were receiving enzyme replacement therapy (ERT status for 3 patients is unkown) and blood was drawn immediately prior to enzyme infusion. All adult and juvenile patients had at least 1 copy of the common splicing mutation (IVS1 13T>G) or a missense mutation. 23/23 adults and 2/3 juveniles had one copy of the IVS1 13T>G mutation. 8/23 adults and 2/3 juveniles had at least 1 copy of a missense mutation.
B. Preparation of Patient Derived Lymphoblast Cells, and Treatment with DNJ
Lymphoblast cell lines were derived from 26 patients and treated with DNJ (0, 30, 100 and 300 μM) for five days. Lymphoblastoid cell lines (LCLs) are leukocyte cultures (primarily B cells) that have been transformed with the Epstein-Barr Virus (EBV) to produce proliferative suspension cultures. Leukocyte cultures were prepared as described in Example 2, and transformed with the EBV to establish the lymphoblast cells. Because well established LCLs can be very fast-growing (even those with genetic and metabolic disorders), their density must be carefully controlled to prevent overcrowding over an extended period. The following protocol details cell seeding density, treatment with a test compound (i.e. DNJ) treatment compound washout, lysing, and assaying of LCLs for the measurement of acid α-glucoside (GAA) with the test compound.
9. Protein (micro-BCA)
10. GAA Activity
7. The plates were read on a multi-well plate reader using 355 nm emission and 460 nm excitation filters. The data was converted using pre-made templates in Excel to calculate nmol 4-MU released per mg total protein per hour using the protein concentration determined via the BCA protein assay.
Patient-derived lymphoblasts demonstrated a dose-dependent increase in GAA levels for 24/26 patient cell lines (mean=93%: range=7-620%) and 4/24 reached significance as determined by 1 way ANOVA and Dunnett's Multiple Comparison Test (p value <0.05) (
The present invention provides a method for establishing Lymphoblast cultures from fresh blood of normal control individuals and patients with Pompe disease. These cultures can be grown for use in an enhancement assay for GAA. These data also show that the effectiveness of GAA enhancement was evident after about 5 days in the lymphoblast growth media. The data generated are a reproducible measure of the degree of enhanced enzyme activity by a SPC for a specific genotype.
As mentioned above, this assay can also be performed using patient derived fibroblasts. In a specific embodiment, the assay using patient derived fibroblasts will be seeded in 6-well plates and be harvested using trypsin.
This method can be used for other SPC-based enhancement assays of other genetic diseases including glycosphingolipidoses and mucopolysaccharidoses, and can be extended as a research and clinical protocol in a wide range of genetically defined diseases, such as Cystic Fibrosis (CFTR) and cancer (p53, PTEN), among others.
The present Example provides an in vitro diagnostic assay to determine a Pompe patient's responsiveness to a specific pharmacological chaperone.
1. Materials:
2. WBC Separation:
3. Washing of WBC's
4. Optional Wash
5. Optional: Freezing, WBC Pellet
When establishing T-cell cultures, the following should be noted.
When analyzed by fluorescent activated cell sorting, the regimen of IL-2 and PHA stimulation results in 99% CD3-positive cells (which stains all T cell subsets), with equal numbers of CD4-positive and CD4-negative cells (data not shown).
The density of the T cells will be adjusted to 1×106 per 3 ml of culture medium (RPMI-1640, 10% FBS, 25 ng/ml IL-2). 3 ml (˜1×106 cells) will then be pipetted into each of 6 wells of a labeled 6-well culture plate and incubated overnight at 37° C. 5% CO2. 3 ml of additional medium will then be added to 3 wells to give a final volume of 6 ml/well. To the three remaining wells, 3 ml of medium containing DNJ (Cambridge Major Laboratories. Inc., Germantown. WI) will be added at a concentration of about 40 μM (2×; final concentration is 20 μM), for 4-5 days. Cells will be harvested by centrifugation (400×g for about 10 minutes) and washed 1× in 10 ml PBS. The resulting pellets will be resuspended in 1 ml PBS and transferred to a 1.7 ml microfuge tube and centrifuged in a refrigerated microfuge at 3000 rpm for 5 minutes. The supernatant was aspirated and the pellets were stored frozen at −80° C. until assayed for enzyme activity.
Note that prior to conducting the enhancement assay, the optimum concentration of DNJ will be determined using a range from 2 nM-200 μM. For example, it may be determined that 20 μM is optimal.
Prior to assay, the T cells will be thawed on ice and sonicated for 2 minutes, and all other assay reagents will be thawed at room temperature. Fluorometric assay of GAA activity will be performed as follows. The cells will be lysed in 0.2 ml deionized water combined with vigorous pipetting and vortexing. The supernatant obtained after centrifugation at 13000 rpm for 2 min at 4° C. will be put into a fresh tube and used as the source of GAA. GAA activity will be determined by incubating 50 μl aliquots of the supernatant (containing comparable quantities of protein as determined using 20 μl in a standard protein quantitation assay) in a 24-well microplate at 37° C. with 3.75 mM 4-methyl umbeliferryl-α-D-glucopyranoside (4MU-alphaGlc) (Research Products International. Mount Prospect. Ill.) in the citric acid/phosphate buffer (27 mM citrate/46 mM phosphate buffer pH 4.6) without taurocholate and with BSA (3 mg/ml). A Wallac 1420 Victor3™ Fluorescence detection reader (Perkin Elmer, Calif.) will be used to measure the released 4-MU at excitation and emission wavelengths of 355 nm and 460 μm, respectively. Appropriate wells for fluorescent standards, and negative (no substrate or no lysate) will also be employed. For each patient sample at least three normal samples will be tested concurrently.
Incubations will typically be 30 minutes in duration but longer or shorter periods may be employed with similar results.
Enzyme activity (nmol/hr/mg of protein) will be calculated according to the following:
One unit of enzyme activity is defined as the amount of enzyme that catalyzes the hydrolysis of 1 nmole of 4-methyl umbeliferryl-α-D-glucopyranoside per hour. The baseline “noise” in the fluorescence output will be obtained by evaluating the average of blank six times. If the activity following SPC treatment is at least 2 standard deviations above the baseline, it will be considered responsive and not noise.
The use of T cells in a test system for enhancement of enzymes by SPCs offers significant advantages in the speed of assay and convenience over other culture systems. A critical step in determining which patients may benefit from SPC therapy is the development of a rapid and reliable method for screening of patient-derived cells for enhancement of GAA activity by DNJ. The results will demonstrate a method for quickly generating a short-lived cell culture that permits the testing of the enhancement and also provides a useful system for future studies on the mechanism of action or for screening of additional chaperone molecules. Leukocytes traditionally used for the diagnosis of affected status do not survive long enough to permit repeat assays if necessary.
Although Epstein-Barr virus transformed B lymphoblasts (Fan et al. Nat. Med. 1999: 5(1), 112-115) and primary fibroblast cultures (Fan, supra; Mayes et al. Clin Chim Acta. 1981; 112(2), 247-251) have been tested (see Example 1), a leukocyte test system provides for an additional, quick assay that may be easily used on a large scale for screening of patients for clinical studies.
The present invention provides a method for establishing T cell cultures from fresh blood of normal control individuals and patients with Pompe disease. These cultures can be grown for use in an enhancement assay for GAA in 7 to 10 days. It is expected that the effectiveness of DNJ enhancement will be evident after about 3 days in the T cell growth media. The data generated will be a reproducible measure of the degree of enhanced enzyme activity by a SPC for a specific genotype.
As with the lymphoblast test system, this method will be used for other SPC-based enhancement assays of other genetic diseases including glycosphingolipidoses and mucopolysaccharidoses, and can be extended as a research and clinical protocol in a wide range of genetically defined diseases, such as Cystic Fibrosis (CFTR) and cancer (p53, PTEN), among others.
This example describes an open label Phase II study of DNJ in Pompe patients with different GAA mutations and will support the use of the in vivo assay. The patients will be selected for the Phase II study based on the increase in GAA activity in the lymphoblasr or T-cell assays described above.
Patients will be administered DNJ according to the dosing schedule described in U.S. Provisional Application 61/028,105, filed Feb. 12, 2008, herein incorporated by reference in its entirety. Blood will be draw into an 8 mL Vacutainer CPT tube at the end of each dosing period and treated as described below.
WBCs will be prepared substantially as described in Example 2, with the exception that no FBS/DMSO is added to the pellet prior to freezing.
This Example describes how to measure acid α-glucosidase (GAA) enzyme activity in muscle biopsies. More specifically, during clinical trials, this method can be used to obtain necessary information on the pharmacodynamic effects of the investigational compound I-deoxynojirimycin (DNJ) on GAA in the target muscle tissues. The method was developed to reliably measure GAA activity in muscles that overcomes the potential problems of enzyme inhibition due to residual DNJ. This method relies on a lectin (concanavalin A)-bound matrix to capture GAA and other glycoproteins which enables efficient washing of the DNJ inhibitor prior to measuring GAA enzyme activity. This method can be used to better understand and develop effective dosing regimes for DNJ to increase GAA levels in Pompe patients.
1. Weigh muscle biopsy sample in a clean 1.5 mL microcentrifuge tube
2. Add 200 μl of Pompe Lysis buffer per 50 mg muscle tissue (human biopsy samples)
1. Aliquot 5 μL of each homogenate to a new microcentrifuge tube and dilute sample 1:10 (v/v) with Lysis Buffer
2. Use 10 μL of each diluted sample (in triplicate) to determine the total protein concentration using a BCA assay or similar method according to the manufacturer's instructions
3. If desired, adjust all samples to a common protein concentration (e.g. 5 mg/mL) with Lysis Buffer
1. Prepare samples in 1.5 mL, microcentrifuge tubes by adding 50 μL pre-equilibrated ConA-Sepharose resin (50% slurry)
2. Add 100 μg of total protein from each tissue homogenate
3. Add Bis-TRIS Buffer to tubes such that the final volume is 500 μL for all samples
4. Incubate samples at room temp for 30 minutes with rocking
5. Spin down ConA-Sepharose at 5000×g for 10-15 seconds and carefully remove the supernatant without disturbing the resin
6. Wash ConA resin by adding 500 μL of Bis-TRIS Buffer, inverting tubes 5 times, spin down at 5000×g for 10-15 seconds and discard supernatant
7. Repeat steps 5 and 6 two additional times and remove supernatant from final wash
8. Add 100 μL of GAA Activity Assay Buffer to each microcentrifuge tube
9. Mix Con A resin by repeated pippetting (˜10 times) using large-bore tips and transfer 20 μL of slurry of each sample to a black 96-well assay plate (perform triplicate for each sample)
10. Add 50 μL of 6 mM 4-MU-α-D-glucopyranoside substrate solution to all wells EXCEPT free 4-MU standards wells
11. Add 4-MU standards in designated wells
12. Incubate plate at 37° C. for 2 hours
13. Stop reaction by adding 70 μL of 400 mM Sodium Carbonate Buffer to all wells
14. Read in a fluorescence plate reader (370 nm excitation/460 nm emission)
15. Extrapolate GAA activity from 4-MU standard curve and report activity as nmol 4-MU released/mg total protein/hr
The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims.
Patents, patent applications, publications, product descriptions, GenBank Accession Numbers, and protocols are cited throughout this application, the disclosures of which are incorporated herein by reference in their entireties for all purpose.
This application claims priority to U.S. Provisional Application No. 61/035,866 filed Mar. 12, 2008; the contents of which are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US09/36989 | 3/12/2009 | WO | 00 | 2/25/2011 |
Number | Date | Country | |
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61035866 | Mar 2008 | US |