Patent Application
20080076708
The present invention is based on the finding that variants of IL-18BP could be identified during recombinant production of human recombinant IL-18BP isoform a. These variants were characterized and it was found that they represent defined N-and C-terminally truncated fragments of full-length IL-18BP isoform a. Definition of the N-glycosylation pattern of recombinant IL-18BP could be achieved in the frame of the present invention, leading to a new variant of full-length IL-18BP.
Surprisingly, all variants of IL-18BP displayed a biological activity comparable to full-length IL-18BP in an in vitro bioassay.
Therefore, in a first aspect, the invention relates to a new IL-18 binding protein (IL-18BP) comprising an amino acid sequence selected from SEQ ID NO: 2, 3, 4, 5, 6 or 7, but not SEQ ID NO: 1, or functional derivatives, fusion proteins or salts thereof. The invention thus relates to active fragments of the IL-18BP containing defined portions of full-length IL-18BP, but not the full-length sequence of IL-18BP isoform a, which is depicted in SEQ ID NO: 1.
In a preferred embodiment, the IL-18BP consists of an amino acid sequence selected from SEQ ID NO: 2, 3, 4, 5, 6 or 7.
In the frame of the present invention, it has further been found that there is a C-terminal heterogeneity of the IL-18BP variants in that species lacking the very C-terminal residue can be detected to some extent.
Therefore, in a preferred embodiment, the invention relates to an IL-18 binding protein (IL-18BP) comprising or consisting of an amino acid sequence selected from SEQ ID NO: 2, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, or SEQ ID NO: 7, but not comprising or consisting of SEQ ID NO: 1, less the C-terminal glycine residue, or a functional derivative, fusion protein or salt thereof.
In the frame of the present invention, variants of IL-18BP have been identified, in which an internal clipping of IL-18BP has occurred.
In a second aspect, the invention relates to an IL-18BP comprising a first polypeptide consisting of amino acids 1 to 30 of SEQ ID NO: 1 and a second polypeptide consisting of amino acids 31 to 164 or of amino acids 31 to 163, wherein the first and second polypeptide are linked by a disulfide bond.
In a third aspect, the IL-18BP comprises a first polypeptide consisting of amino acids 15 to 30 of SEQ ID NO: 1 and a second polypeptide consisting of amino acids 31 to 164 or of amino acids 31 to 163, wherein the first and second polypeptide are linked by a disulfide bond.
The IL-18BPs may be unglycosylated or glycosylated. Preferably, the IL-18BPs of the invention are N-glycosylated at asparagine residues Asn 49, Asn 73 and Asn 117 (numbering according to
During the experiments leading to the present invention, it has been found for the first time that recombinantly produced full-length IL-18 binding protein isoform a is not glycosylated at all putative N-glycosylation sites, but only at three defined Asparagine residues, which are Asn 49, 73 and 117. Therefore, the invention further relates to an IL-18BP having the amino acid sequence of SEQ ID NO: 1, wherein the protein is N-glycosylated at Asn 49, Asn 73 and Asn 117, as well as to functional derivatives, fusion proteins or salts thereof.
In a preferred embodiment, the IL-18BP has the amino acid sequence of SEQ ID NO: 1 less the C-terminal glycine residue.
The sequence of full length human IL-18BP and its splice variants/isoform are disclosed e.g. from WO 99/09063, or from Novick et al., 1999, as well as in Kim et al., 2000. SEQ ID NO: 1 represents the amino acid sequence of mature full-length IL-18BP isoform a.
In the following, the proteins of the invention may be generally designated “IL-18BP”, “IL-18BPs” or “IL-18BP(s) of the invention”. These terms, as used therein, encompass all IL-18BP variants described in the frame of the present invention.
The proteins according to the present invention may be derived from natural sources, such as urine, or they may preferably be produced recombinantly. Recombinant expression may be carried out in prokaryotic expression systems like E. coli, or in eukaryotic, and preferably in mammalian, expression systems. They may also preferably be produced in human expression systems. Established cell lines such as the Chinese hamster ovary cell line (CHO) or the human embryonic kidney cell line 293 may be especially useful for production of the IL-18BP variants of the present invention.
Further variants within the scope of the present invention may be proteins having conservative amino acid substitutions of the sequences depicted in
Conservative amino acid substitutions of IL-18BP polypeptides, may include synonymous amino acids within a group which have sufficiently similar physicochemical properties that substitution between members of the group will preserve the biological function of the molecule (Grantham, 1974). It is clear that insertions and deletions of amino acids may also be made in the above-defined sequences without altering their function, particularly if the insertions or deletions only involve a few amino acids, e.g., under thirty, and preferably under ten, and do not remove or displace amino acids which are critical to a functional conformation, e.g., cysteine residues. Proteins and muteins produced by such deletions and/or insertions come within the purview of the present invention.
Preferably, the synonymous amino acid groups are those defined in Table 1. More preferably, the synonymous amino acid groups are those defined in Table 2; and most preferably the synonymous amino acid groups are those defined in Table 3.
It is understood that minor changes in the amino acid sequence of the IL-18BP variants are within the scope of the invention, having a sequence of amino acids sufficiently duplicative of that of an IL-18BP variant described herein, such as to have a comparable activity to IL-18BP. One activity of IL-18BP is its capability of binding IL-18. Thus, it can be determined whether any given variant has substantially the same activity as IL-18BP by means of routine experimentation comprising subjecting such a mutein, e.g., to a simple sandwich competition assay to determine whether or not it binds to an appropriately labeled IL-18, such as radio-immunoassay or ELISA assay. A further meaningful assay describing IL-18BP activity is the bioassay described in the example below.
Examples of production of amino acid substitutions in proteins which can be used for obtaining variants of IL-18BP polypeptides or proteins for use in the present invention include any known method steps, such as presented in U.S. Pat. Nos. 4,959,314, 4,588,585 and 4,737,462, to Mark et al. 5,116,943 to Koths et al., 4,965,195 to Namen et al. 4,879,111 to Chong et al. and 5,017,691 to Lee et al. and lysine substituted proteins presented in U.S. Pat. No. 4,904,584 (Shaw et al).
In an embodiment of the invention, the IL-18BP variants are fused proteins.
The term “fused protein” refers to a polypeptide comprising an IL-18BP of the invention, fused with another protein, which, e.g., has an extended residence time in body fluids. An IL-18BP may thus be fused to another protein, polypeptide or the like, e.g., an immunoglobulin or a fragment thereof.
In a preferred embodiment of the invention, the IL-18BP of the invention comprises an immunoglobulin fusion, i.e. it is a fused protein comprising all or part of an IL-18BP of the invention, which is fused to all or a portion of an immunoglobulin. Methods for making immunoglobulin fusion proteins are well known in the art, such as the ones described in WO 01/03737, for example. The person skilled in the art will understand that the resulting fusion protein of the invention retains the biological activity of IL-18BP, in particular the binding to IL-18. The fusion may be direct, or via a short linker peptide which can be as short as 1 to 3 amino acid residues in length or longer, for example, 13 amino acid residues in length. Said linker may be a tripeptide of the sequence E-F-M (Glu-Phe-Met), for example, or a 13-amino acid linker sequence comprising Glu-Phe-Gly-Ala-Gly-Leu-Val-Leu-Gly-Gly-Gln-Phe-Met introduced between the IL-18BP sequence and the immunoglobulin sequence. The resulting fusion protein has improved properties, such as an extended residence time in body fluids (half-life), increased specific activity, increased expression level, or the purification of the fusion protein may be facilitated.
In a preferred embodiment, IL-18BP is fused to the constant region of an Ig molecule. Preferably, it is fused to heavy chain regions, like the CH2 and CH3 domains of human IgG1 or IgG3, for example. The generation of specific fusion proteins comprising IL-18BP and a portion of an immunoglobulin are described in example II of WO 99/09063, for example. Other isoforms of Ig molecules are also suitable for the generation of fusion proteins according to the present invention, such as isoforms IgG2 or IgG4, or other Ig classes, like IgM or IgA, for example. Fusion proteins may be monomeric or multimeric, hetero- or homomultimeric.
The invention further relates to a process for production of an IL-18BP fused protein comprising preparing a DNA construct that encodes an IL-18BP of the invention ligated to a nucleic acid encoding a second polypeptide, wherein upon expression, said DNA construct encodes a fusion protein comprising the IL-18BP of the invention fused to the second polypeptide.
Preferably, the second polypeptide is a portion of an immunoglobulin, more preferably the Fc portion of an immunoglobulin.
In a further embodiment, the IL-18BP variants are functional derivatives. “Functional derivatives” as used herein cover derivatives of IL-18BP variants or their fused proteins, which may be prepared from the functional groups which occur as side chains on the residues or the N- or C-terminal groups, by means known in the art, and are included in the invention as long as they remain pharmaceutically acceptable, i.e. they do not destroy the activity of the protein which is substantially similar to the activity of IL-18BP, or viral IL-18BPs, and do not confer toxic properties on compositions containing it. Functional derivatives of IL-18BP may be conjugated to polymers in order to improve the properties of the protein, such as the stability, half-life, bioavailability, tolerance by the human body, or immunogenicity. To achieve this goal, IL-18-BP may be linked e.g. to Polyethlyenglycol (PEG). PEGylation may be carried out by known methods, described in WO 92/13095, for example.
Derivatives may also, for example, include aliphatic esters of the carboxyl groups, amides of the carboxyl groups by reaction with ammonia or with primary or secondary amines, N-acyl derivatives of free amino groups of the amino acid residues formed with acyl moieties (e.g. alkanoyl or carbocyclic aroyl groups) or O-acyl derivatives of free hydroxyl groups (for example that of seryl or threonyl residues) formed with acyl moieties.
The invention further relates to a process for production of an IL-18BP derivative of the invention comprising chemically modifying an IL-18BP of the invention to include at least one derivative moiety. Preferably, the moiety is a polyethylene glycol moiety.
Yet a further embodiment of the invention relates to salts of the IL-18BP variants.
The term “salts” herein refers to both salts of carboxyl groups and to acid addition salts of amino groups of IL-18BP variant molecule, or analogs thereof. Salts of a carboxyl group may be formed by means known in the art and include inorganic salts, for example, sodium, calcium, ammonium, ferric or zinc salts, and the like, and salts with organic bases as those formed, for example, with amines, such as triethanolamine, arginine or lysine, piperidine, procaine and the like. Acid addition salts include, for example, salts with mineral acids, such as, for example, hydrochloric acid or sulfuric acid, and salts with organic acids, such as, for example, acetic acid or oxalic acid. Of course, any such salts must retain the biological activity of the IL-18BP relevant to the present invention, such as inhibition of IFN-gamma induction in the bioassay described in the examples below.
In a further aspect, the invention relates to a nucleic acid coding for an IL-18BP of the invention. Such coding sequence may easily be deduced from the amino acid sequences depicted in
In yet a further aspect, the invention relates to a host cell comprising the nucleic acid of the invention. Such a host cell may be either prokaryotic or eukaryotic, preferably mammalian, more preferably a host cell suitable for recombinant expression of therapeutic proteins such as Chinese hamster ovary cells (CHO) or human cells.
The invention further relates to a process for production of an IL-18BP of the invention comprising the step of culturing a host cell according to the invention under conditions suitable for expression of said IL-18BP.
The process for production of an IL-18BP may also comprise the step of isolating the IL-18BP from the cell culture supernatant of a host cell of the invention.
In another aspect, the invention relates to a composition comprising an IL-18BP in accordance with the present invention. Preferably, it is a pharmaceutical composition. Optionally, the pharmaceutical composition further comprises pharmaceutically acceptable surfactants, excipients, carriers, diluents and vehicles.
The definition of “pharmaceutically acceptable” is meant to encompass any carrier, which does not interfere with effectiveness of the biological activity of the active ingredient and that is not toxic to the host to which H is administered. For example, for parenteral administration, the active protein(s) may be formulated in a unit dosage form for injection in vehicles such as saline, dextrose solution, serum albumin and Ringer's solution.
The active ingredients of the pharmaceutical composition according to the invention can be administered to an individual in a variety of ways. The routes of administration include intradermal, transdermal (e.g. in slow release formulations), intramuscular, intraperitoneal, intravenous, subcutaneous, oral, intracranial, epidural, topical, rectal, and intranasal routes.
Preferred administration routes of the invention are the subcutaneous and the intramuscular route.
Any other therapeutically efficacious route of administration can be used, for example absorption through epithelial or endothelial tissues, or by gene therapy wherein a DNA molecule encoding the active agent is administered to the patient (e.g. via a vector), which causes the active agent to be expressed and secreted in vivo. If an expression vector comprising the coding sequence of IL-18BP(s) of the invention is to be administered, it may e.g. be injected intramuscularly as naked DNA.
For parenteral (e.g., intravenous, subcutaneous, intramuscular) administration, the active protein(s) can be formulated as a solution, suspension, emulsion or lyophilized powder in association with a pharmaceutically acceptable parenteral vehicle (e.g. water, saline, dextrose solution) and additives that maintain isotonicity (e.g. mannitol) or chemical stability (e.g. preservatives and buffers). The formulation is sterilized by commonly used techniques.
The bioavailability of the active protein(s) according to the invention can also be ameliorated by using conjugation procedures which increase the half-life of the molecule in the human body, for example linking the molecule to polyethylene glycol, as described in the PCT Patent Application WO 92/13095.
The therapeutically effective amounts of the active protein(s) will be a function of many variables, including the type of IL-18BP use, their affinity for IL-18, any residual cytotoxic activity exhibited by the IL-18BP(s), the route of administration, the clinical condition of the patient (including the desirability of maintaining a non-toxic level of endogenous IL-18 activity).
A “therapeutically effective amount” is such that when administered, the IL-18BP variant results in inhibition of the biological activity of IL-18. The dosage administered, as single or multiple doses, to an individual will vary depending upon a variety of factors, including IL-18BP variant pharmacokinetic properties, the route of administration, patient conditions and characteristics (sex, age, body weight, health, size), extent of symptoms, concurrent treatments, frequency of treatment and the effect desired. Adjustment and manipulation of established dosage ranges are well within the ability of those skilled in the art, as well as in vitro and in vivo methods of determining the inhibition of IL-18 in an individual.
In a preferred embodiment of the present invention, the IL-18BP variant is used in an amount of about 0.001 to 1000 mg/kg of body weight, or about 0.001 to 100 mg/kg of body weight or about 0.01 to 10 mg/kg of body weight or about 0.1 to 5 mg/kg or about 1 to 3 mg/kg of body weight.
The frequency of administration may be daily or every other day. It may also be three times per week or once per week.
The doses administered may always be the same or vary, depending on the patient's needs. The doses are usually given in divided doses or in sustained release form effective to obtain the desired results. Second or subsequent administrations can be performed at a dosage which is the same, less than or greater than the initial or previous dose administered to the individual. A second or subsequent administration can be administered during or prior to onset of the disease.
According to the invention, the IL-18BP variant can be administered prophylactically or therapeutically to an individual prior to, simultaneously or sequentially with other therapeutic regimens or agents (e.g. multiple drug regimens), in a therapeutically effective amount, in particular with an interferon and/or a TNF inhibitor. Active agents that are administered simultaneously with other therapeutic agents can be administered in the same or different compositions.
In a further aspect, the invention relates to the use of an IL-18BP of the invention for the preparation of a medicament for treatment and/or prevention of an IL-18 mediated disease or disorder. IL-18 mediated diseases are known in the art (reviewed e.g. by Gracie et al., 2003).
In a preferred embodiment, the disease to be treated or prevented by the IL-18P variant of the invention is selected from psoriasis, arthritis, in particular rheumatoid arthritis, inflammatory bowel disease, in particular Crohn's disease, liver injury, atherosclerosis, sepsis, myocardial infarction, traumatic brain injury, allergy, peripheral vascular disease, multiple sclerosis, tumor metastasis.
For detailed description and definition of these diseases, it is particularly referred to the following published patent applications which are fully incorporated by reference herein: WO 99/09063, WO 01/07480, WO 01/62285, WO 02/060479, WO 02/096456, WO 02/092008, WO 03/013577.
Interferons are predominantly known for inhibitory effects on viral replication and cellular proliferation. Interferon-γ, for example, plays an important role in promoting immune and inflammatory responses. Interferon β (IFN-β, an interferon type I), is said to play an anti-inflammatory role.
The invention therefore also relates to the use of a combination of an IL-18BP of the invention and an interferon in the manufacture of a medicament for the treatment of an IL-18 mediated disease.
Interferons may also be conjugated to polymers in order to improve the stability of the proteins. A conjugate between Interferon β and the polyol Polyethlyenglycol (PEG) has been described in WO 99/55377, for instance.
In another preferred embodiment of the invention, the interferon is lnterferon-β (IFN-β, and more preferably IFN-β1a.
The IL-18BP of the invention is preferably used simultaneously, sequentially, or separately with the interferon.
In yet a further embodiment of the invention, an IL-18BP of the invention is used in combination with a TNF antagonist. TNF antagonists exert their activity in several ways. First, antagonists can bind to or sequester the TNF molecule itself with sufficient affinity and specificity to partially or substantially neutralize the TNF epitope or epitopes responsible for TNF receptor binding (hereinafter termed “sequestering antagonists”). A sequestering antagonist may be, for example, an antibody directed against TNF.
Alternatively, TNF antagonists can inhibit the TNF signaling pathway activated by the cell surface receptor after TNF binding (hereinafter termed “signaling antagonists”). Both groups of antagonists are useful, either alone or together, in combination with an IL-18BP variant, in the therapy of hypersensitivity disorders.
TNF antagonists are easily identified and evaluated by routine screening of candidates for their effect on the activity of native TNF on susceptible cell lines in vitro, for example human B cells, in which TNF causes proliferation and immunoglobulin secretion. The assay contains TNF formulation at varying dilutions of candidate antagonist, e.g. from 0.1 to 100 times the molar amount of TNF used in the assay, and controls with no TNF or only antagonist (Tucci et al., 1992).
Sequestering antagonists are the preferred TNF antagonists to be used according to the present invention. Amongst sequestering antagonists, those polypeptides that bind TNF with high affinity and possess low Immunogenicity are preferred. Soluble TNF receptor molecules and neutralizing antibodies to TNF are particularly preferred. For example, soluble TNF-RI (also called p55) and TNF-RII (also called p75) are useful in the present invention. Truncated forms of these receptors, comprising the extracellular domains of the receptors or functional portions thereof, are more particularly preferred antagonists according to the present invention. Soluble TNF type-I and type-II receptors are described in European Patents EP 308 378, EP 398 327 and EP 433 900, for example.
These truncated, soluble TNF receptors are soluble and have been detected in urine and serum as TNF inhibitory binding proteins, called TBPI and TBPII, respectively (Engelmann et al., 1990). The simultaneous, sequential, or separate use of the IL-18BP variant with the TNF antagonist and /or an Interferon is preferred, according to the invention.
According to the invention, TBP I and TBPII are preferred TNF antagonists to be used in combination with an IL-18BP variant of the invention. Derivatives, fragments, regions and biologically active portions of the receptor molecules functionally resemble the receptor molecules that can also be used in the present invention. Such biologically active equivalent or derivative of the receptor molecule refers to the portion of the polypeptide, or of the sequence encoding the receptor molecule, that is of sufficient size and able to bind TNF with such an affinity that the interaction with the membrane-bound TNF receptor is inhibited or blocked.
The invention further relates to the use of an expression vector comprising the coding sequence of an IL-18BP of the invention in the preparation of a medicament for the prevention and/or treatment of IL-18 meditated disorders. Thus, a gene therapy approach is considered in order to deliver the IL-18BP variant to the site where it is required. In order to treat and/or prevent a hypersensitivity disorder, the gene therapy vector comprising the sequence of an IL-18BP variant production and/or action may be injected directly into the diseased tissue, for example, thus avoiding problems involved in systemic administration of gene therapy vectors, like dilution of the vectors, reaching and targeting of the target cells or tissues, and of side effects.
The invention further relates to the use of a cell that has been genetically modified to produce an IL-18BP of the invention in the manufacture of a medicament for the treatment and/or prevention of an IL-18 mediated disease.
The invention further relates to a method for the preparation of a pharmaceutical composition comprising admixing an effective amount of an IL-18BP variant and/or an Interferon and/or a TNF antagonist with a pharmaceutically acceptable carrier.
The invention further relates to a method of treatment of IL-18 mediated disease, comprising administering a pharmaceutically effective amount of an IL-18BP variant to a patient in need thereof.
Having now fully described this invention, it will be appreciated by those skilled in the art that the same can be performed within a wide range of equivalent parameters, concentrations and conditions without departing from the spirit and scope of the invention and without undue experimentation.
While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications. This application is intended to cover any variations, uses or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth as follows in the scope of the appended claims.
All references cited herein, including journal articles or abstracts, published or unpublished U.S. or foreign patent application, issued U.S. or foreign patents or any other references, are entirely incorporated by reference herein, including all data, tables, figures and text presented in the cited references. Additionally, the entire contents of the references cited within the references cited herein are also entirely incorporated by reference.
Reference to known method steps, conventional methods steps, known methods or conventional methods is not any way an admission that any aspect, description or embodiment of the present invention is disclosed, taught or suggested in the relevant art.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art (including the contents of the references cited herein), readily modify and/or adapt for various application such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning an range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance presented herein, in combination with the knowledge of one of ordinary skill in the art.
The mapping was carried out according to standard protocols, outlined below.
About 150 μg of dried r-hIL-18BP was dissolved with 200 μL of 0.2M Ammonium Acetate 16 mM Calcium Chloride pH 5.5 buffer and 100 mlU of Sialidase. The reaction was performed at 37°±1°C. for 1 hour. Then the protein was dried in Speed-Vacuum. After desiccation the protein was reduced and alkylated as described below.
Dissolved with 200 μL of 0.5M Tris-Cl 2 mM EDTA pH 8,5±0.05 6M Guanidine 11 mg/mL dithiotreitol under nitrogen atmosphere. The reaction was performed at room temperature for 1 hour. Then has been added 25 μL of 250 mg/mL iodioacetic acid under nitrogen atmosphere. The mixture was incubated in the dark at 37±1° C. for 45 minutes and then stopped by adding 200 μL of 0.1% aqueous TFA and 20 μL β-mercaptoethanol under nitrogen atmosphere .The reaction was incubated at room temperature for 15 minutes.
After reduction and alkylation, the protein was purified in RP-HPLC as described below:
The purified material was dried in speed-vac, dissolved in 250 μL of 0.1M ammonium bicarbonate pH 9,0±0.05 and incubated with 5 μL of modified bovine trypsin at 37±1° C. for 4 hours with intermittent shaking. The reaction was stopped by adding 60 μL of 5% aqueous TFA.
Half volume of the r-hIL-18BP peptide mixture was purified in RP-HPLC as described below:
Automated Edman sequencing was carried out on a Procise protein sequencer, according to the manufacturer's instructions.
MALDI-ToF spectra were carried out on a Voyager PE-Pro, according to manufacturer instructions.
The r-hIL-18BP was submitted to the peptide mapping procedure following the procedure mentioned above. After the digestion an aliquot of the peptide mixture of each sample was analysed as described below:
After UV detector the flow was split in order to introduce in the spectrometer source at 50 μL/min.
The mass spectrometer has been set with the following parameters:
The SE-HPLC analysis was carried out as reported below:
Two micrograms of r-hIL18BP were loaded onto the recast gel Excel Gel® SDS Homogeneous 12.5% (by Habersham Biosciences) in non reducing conditions and run under constant voltage (600 V) at 15° C. Molecular weight markers and the Interim Reference Materials ST1P01/r-hIL-18BP were also loaded onto the gel.
After the electrophoresis run the gel was stained with the Silver Staining Kit-Protein (Plus One) as described in the instructions contained in the kit leaflet. Briefly, the gel was fixed for 30 minutes in a solution composed of acetic acid and ethanol. After a washing step, the sensitizing solution was added and removed after 30 minutes. The gel was washed again and then reacted with the silver solution for 20 minutes. After a washing cycle, the staining was developed in developing solution and subsequently stopped. The gel was then thoroughly washed in water and kept in preserving solution before final storage in Cellophane Sheets.
Gels were scanned and data elaborated using the Phoenix 1D full software.
Two hundred monograms of r-hIL-18BP were loaded onto the recast gel Excel Gel® SDS Homogeneous 12.5% (by Habersham Biosciences) in non reducing conditions and run under constant voltage (600 V) at 15° C. Molecular weight markers and the Interim Reference Materials ST1P01/r-hIL-18BP were also loaded onto the gel.
After the electrophoresis run, proteins were transferred from the gel onto a nitro-cellulose membrane by passive contact for 60 minutes at room temperature and probed with 0.1 μg/mL of the monoclonal antibody to r-hIL-18BP clone 582.10 (IL). The reaction was revealed by a chemiluminescent substrate (ECL kit from Habersham Biosciences) after reaction with 1:2000 diluted goat anti-mouse IgG HRP conjugate. The light emission was detected by 10 seconds or 1 minute of exposure to a sensitive autoradiography film.
Coomassie blue or silver staining methods were adopted to detect the MW markers.
After the immunodetection, the film was scanned and the molecular weight (MW) values of the bands were automatically derived from the MW calibration curve using the Phoenix 1-D Full software.
The biological activity of samples was quantified by using an in vitro bioassay. This bioassay was based on the ability of the human acute myelogenous leukemia cell line KG-1 to produce IFN-γ in response to human IL-18 plus human TNF-α in a dose-dependent manner. The r-hIL-18BP specifically binds r-hIL-18 neutralizing its biological activity thereby suppressing the production of IFN-γ.
Briefly, KG-1 cells at 1×105 cells/well were added to a 96 well plate already containing different concentrations of r-hIL-18BP in the presence of a fixed concentration of r-hIL18 (40 ng/ml in the well) plus a fixed concentration of r-hTNF-α (10 ng/ml in the well). The concentration of each of these two substances combined together was able to give the sub-maximal induction of production of IFN-γ on KG-1 cells. After 24 hr at 37° C., 5% CO2, the plate was put at −20° C. in order to submit the treated cells to a freeze/thaw cycle before performing the immunoassay to determine the quantity of IFN-γ present in the cell supernatant. The cell supernatants was collected and human IFN-γ measured by means of a specific immunoassay (ELISA h-IFN-γ, Duo Set R&D Systems kit). The amount of IFN-γ produced by the treated cells (either with standard curve or IL-18BP sample) was calculated by interpolating the y values (O.D.) on the IFN-γ Standard curve, provided with the kit, fitted by a Sigmoidal dose-response (4PL) Log/Log transformed, thus obtaining the x values (IFN-γ concentrations) (GraphPad Prism).
The biological activity of IL-18BP sample was determined vs the reference preparation by testing the sample at two concentrations falling in the linear part of the reference dose-response curve. At least two independent experiments were carried out. In each independent assay, each concentration was tested in dependent duplicates in a plate.
The titer of IL-18BP sample for each concentration tested, was calculated by interpolating the averaged (two replicates) y values (O.D.) of the amount of IFN-γ produced on the linear part of the reference dose-response curve (Log/Log transformed) thus obtaining the x values (IL-18BP activity).
The value obtained from each concentration was averaged and the final activity of IL-18BP drug substance sample was given by the arithmetic mean of the potencies obtained from each of the independent assay performed.
The titer of the different IL-18BP drug substances was calculated versus the Interim Reference Material ST1P01/r-hIL-18BP.
Two independent experiments were carried out.
The primary structure of full length r-hIL-18BP is shown in
The molecule contains four potential N-glycosylation sites, at Asn 49, Asn 64, Asn 73 and Asn 117. Only three of the four sites have been found glycosylated, i.e. Asn 49, Asn 73 and Asn 117, whereas Asn 64 has been found glycosylated only in trace amounts.
The average molecular weight of the whole molecule as determined by SDS-PAGE and SE-HPLC is approximately 50 kDa.
The amino acid composition may be taken from table 4.
The routine QC tests of batches from serum-free production revealed that:
Since r-hIL-18BP is a highly glycosylated molecule, presenting a high heterogeneity in terms of glycosylation, the protein was submitted to Neuraminidase treatment in order to reduce oligosaccharide heterogeneity due to sialic acid. The protein was then submitted to reduction, carboxymethylation and purification in order to render the trypsin cleavage sites well accessible to the enzyme.
The peptide procedure was carried out with the following steps:
A chromatographic profile different to the one of r-hIL-18BP produced in serum-containing medium, was already detected during the purification of the reduced and alkylated r-hIL-18BP batches from serum-free production (not shown).
Furthermore, the peptide mapping profile of a truncated form of r-hIL-18BP, compared to the current reference standard r-hIL-18BP, showed both an extra peak and a different relative Intensity of glycosylated peptides (not shown).
The sequence analysis of the intact molecule showed different fragments corresponding to molecule starting from residues 1, 16, 31, and in lower amounts from residues 69, 70, 107 and 125. The N-terminal analysis is depicted in
The spectra obtained by MALDI-TOF showed an additional peak at lower molecular weight (not shown).
The r-hIL-18BP has a relative molecular weight of about 50 kDa as assigned by 12.5% SDS-PAGE. Serum-free produced r-hIL-18BP showed an additional band of about 40 kDa detected by silver staining. Both bands reacted with an IL-18BP-specific antibody (clone 582.10) in Western Blotting analysis. The silver stained SDS-PAGE gel is depicted in
The lanes were occupied as follows:
CT20 is a batch of truncated IL-18BP, while ST1P01 is the standard full-length IL-18BP without truncated forms.
It was assessed whether The results of specific activity of the different IL-18 BP drug substance batches are reported in table 5 where the untruncated (ILNCT16-18 and ST1P01)and truncated form (highlighted, ILNCT 19-22) are shown.
ILNCT19
949,440
61.6
15,413
ILNCT20
1,225,693
57.2
21,428
ILNCT21
1,278,583
62.8
20,360
ILNCT22
1,347,902
59.8
22,540
This experiment shows that truncated IL-18BP has a biological activity comparable to untruncated IL-18BP-.
In order to characterize the extra peak detected by different techniques, the SE-HPLC analysis was employed to separate the peaks of interest so as to submit them to further characterization steps. For the intended purpose the two peaks were collected separately.
In order to unequivocally identify the collected peaks, peak 1 and peak 2 were re-injected onto the HPLC column.
The two peaks were submitted to peptide mapping according to the protocol described above.
The chromatographic profiles of reduced and alkylated samples are reported in
Only the main peaks of each fraction were submitted to peptide mapping and analysed by LC-ES/MS:
The extra peak (peptide 31-61) appearing in the peptide mapping profiles is due to internal cleavages of the molecule, as confirmed by the sequence analysis of the peaks and of the intact molecule.
Moreover the different intensities of glycosylated peptides (Pep. 1-15, Pep. 1-32 and Pep. 16-32) show a different glycosylation pattern.
The N-terminal analysis carried out onto peak 1 and peak 2 collected directly from SE-HPLC analysis, gave the following results:
The apparent molecular weight assigned by SDS-PAGE (
The results obtained employing different analytical tools showed that the following major cleavage sites can be identified:
When a truncated form of r-hIL18BP is present, the above results show the following:
| Number | Date | Country | Kind |
|---|---|---|---|
| 03101326.1 | May 2003 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP04/05073 | 5/11/2004 | WO | 00 | 8/31/2006 |
