Patent Application
20180112202
A Sequence Listing submitted as an ASCII text file via EFS-Web is hereby incorporated by reference in accordance with 35 U.S.C. § 1.52(e). The name of the ASCII text file for the Sequence Listing is SeqList-PLOUG212_002P1.txt, the date of creation of the ASCII text file is Nov. 22, 2017, and the size of the ASCII text file is 11 KB.
The present invention relates to a purification protocol of recombinant human galactocerebroside β-galactosidase and products obtainable by such process.
Galactocerebroside β-galactosidase is an enzyme that catalyzes the hydrolytic cleavage of galactose from galactocerebroside. Deficiency results in accumulation of galactocerebroside in tissues. Previous reported methods describe partial purification of human GALC from natural specimen, such as liver (Ben-Yoseph, Archives of Biochemistry and Biophysics, 1979), lymphocytes (Sakai et al, J. Biochem., 1994) and urine (Chen et al, Biochimica et Biophysica acta, 1993). The methods are complicated due to GALC's extreme hydrophobicity and low abundance. The recoveries are extremely low and the obtained products are described as mixtures of full length GALC (80 kDa) and processed forms (mainly 50 and 30 kDa). Furthermore, the aim with these previous reports on purifications was characterization of the enzyme and not production in large scale for enzyme replace therapy (ERT) in humans.
Hence, an improved purification protocol of rhGALC resulting in a homogenous product (80 kDa rhGALC) of high purity in a physiological solution suitable for human use would be advantageous.
A process for purification of recombinant human Galactocerebroside β-Galactosidase (rhGALC) resulting in a final product fulfilling quality and purity requirements for animal/human studies has been developed. The process comprises three main chromatographic steps and optionally one UFDF formulation step. In this study fresh and clarified harvest from a 20 L fed batch bioreactor was purified with the optimized process to produce rhGALC for animal/human studies.
The purification protocol is based on the three-phase strategy consisting of capture, intermediate and polishing chromatographic steps with different modes of action. Preferably, all steps are performed in binding mode and include wash steps before elution. In an embodiment the capture step is Capto™ Blue, the intermediate step is Capto™ Adhere and the polishing step is Toyopearl Ether. Two dedicated virus inactivation/removal steps are included in embodiments of the process. The product pool may be formulated by UFDF prior to sterile filtration into the final product.
The final aim is to produce rhGALC as enzyme replacement therapy for treatment of the lysosomal enzyme storage disease Globoid Cell Leukodystrophy (Krabbe disease). Krabbe disease is caused by the genetic deficiency of the enzyme GALC. Deficiency of GALC results in the progressive accumulation of the sphingolipid metabolite galactosylsphingosine (psychosine), demyelination, and early death.
Thus, an object of the present invention relates to the provision of a purification protocol for rhGALC. In particular, it is an object of the present invention to provide a purification protocol for rhGALC that solves the above mentioned problems with usability in animals and humans.
Thus, one aspect of the invention relates to a process for purifying recombinant human Galactocerebroside β-Galactosidase (rhGALC) from a cell culture, wherein a fraction of said cell culture comprising rhGALC is subjected to chromatography on resins, the process comprising
In particular embodiments, the invention also provides a process for purifying recombinant human Galactocerebroside β-Galactosidase (rhGALC) from a cell culture, wherein a fraction of said cell culture comprising rhGALC is subjected to chromatography on resins, the process comprising
Another aspect of the present invention relates to a composition comprising rhGALC. The composition may be one that is obtainable by the purification process according to the present invention.
Yet another aspect of the present invention is to provide the composition according to the present invention for use as a medicament.
Still another aspect of the present invention is to provide a composition according to the present invention for use in the treatment of Globoid Cell Leukodystrophy (Krabbe disease).
In yet a further aspect the invention relates to a method of treating Globoid Cell Leukodystrophy (Krabbe disease) and/or reducing or alleviating the symptoms associated with Globoid Cell Leukodystrophy (Krabbe disease), said method comprising a step of administering a composition comprising a purified rhGALC according to the present invention to a subject in need thereof.
The present invention will now be described in more detail in the following.
Process
An aspect of the present invention provides a process for purifying recombinant human Galactocerebroside β-Galactosidase (rhGALC) from a cell culture, wherein a fraction of said cell culture comprising rhGALC is subjected to chromatography on resins, the process comprising
Preferably, the rhGALC obtained by said process is characterized by at least one of the following i) to iv):
In particular by the provision of purified rhGALC wherein the molar ratio between full length rhGALC (80 kDa) and the main processed products (50+30 kDa) in said composition is at least 50:2.5, the present inventions makes rhGALC suitable for administration to a subject in need thereof, such as in particular by enzyme replacement therapy, available. Thereby, the present invention addresses a previously unmet medical need.
Preferably, the rhGALC obtained by said process is characterized by at least two, more preferably at least three, most preferably all of the above i) to iv)). The examples reported herein demonstrate that rhGALC with respective properties is indeed obtainable by the process according to the present invention.
According to some embodiments of the invention, the said intermediate step comprises purification of said rhGALC on said second multimodal chromatographic resin, followed by purification of said rhGALC on a chromatography resin selected from the group consisting of:
According to further embodiments of the invention, the said first and second multimodal chromatography resins are different resins.
The said first multimodal chromatographic resin may in particular comprise electrostatic ligands.
According to other embodiments of the invention, the said second multimodal chromatographic resin comprises an anionic and hydrophobic ligand.
In still further embodiments, the chromatographic resin in said polishing step is a resin having hydrophobic ligands.
The said first multimodal chromatographic resin may in particular comprises as ligand a compound of the formula (VI) as set forth hereinbelow.
The said second multimodal chromatographic resin may in particular comprise as ligand a compound of the formula (VIII) as set forth hereinbelow.
According to further embodiments the said first multimodal chromatographic resin comprises as ligand a compound of the formula (VI) as set forth hereinbelow and the said second multimodal chromatographic resin comprises as ligand a compound of the formula (VIII) as set forth hereinbelow. According to these embodiments it is preferred that said rhGALC is subsequently purified on a chromatographic resin, which is an ether resin. Examples of suitable ether resins are given below.
According to some embodiments of the invention, the said rhGALC is eluted from said first multimodal chromatographic resin in first elution buffer comprising at least 30% propylene glycol and/or ethylene glycol (v/v).
In other embodiments of the invention, the said rhGALC is eluted from said second multimodal chromatographic resin in a second elution buffer comprising at least 30% propylene glycol and/or ethylene glycol (v/v) and having a pH below 5.5.
The process for purifying recombinant human Galactocerebroside β-Galactosidase (rhGALC) according to the invention may in particular comprise
Several synonyms for Human Galactocerebroside β-Galactosidase (rhGALC) exist. The ones most commonly used are Galactocerebrosidase, Galactosylceramidase, Galcerase, Galactosylceramide beta-galactosidase (EC3.2.1.46). Protein accession number(s) are NP_000144.2 and P45803. It is to be understood that the rhGALC according to the present invention may comprise tags.
In the aspects and embodiments according to the invention the term Human Galactocerebroside β-Galactosidase (rhGALC) also includes functionally equivalent parts or analogues of the full length amino acid sequence.
Certain characteristics of rhGALC are important to know when setting up a purification protocol of rhGALC or functionally equivalent parts or analogues thereof.
In the aspects and embodiments of the present invention as described herein, the rhGALC or said functionally equivalent part or analogue thereof comprises an amino acid sequence selected from the group consisting of:
In the context of the present invention the term “functionally equivalent” implies that the said part or analogue of rhGALC is able to hydrolyze the galactose ester bonds of galactocerebroside, galactosylsphingosine, lactosylceramide, monogalactosyldiglyceride, and the chromogenic substrate 2-hexadecanoylamino-4-nitrophenyl-b-D-galactopyranoside (HNG). In particular embodiments the said part or analogue of rhGALC retains at least 50%, such as at least 60%, at least 70%, at least 80%, at least 90% or at least 95% of the ability of the native enzyme (having the amino acid sequence set forth in SEQ ID NO: 2) to hydrolyse the galactose ester bonds of said compounds.
The catalytic properties of said part or analogue of rhGALC may be determined by measuring the hydrolysis of 2-hexadecanoylamino-4-nitrophenyl-b-D-galactopyranoside (HNG) into 2-hexadecanoylamino-4-nitrophenol (HN) at pH 4.5. At pH 10.5, HN is a yellow colored product, which may be determined spectrophotometrically at 410 nm. An illustrative example of such measurements is provided in Example 12 in the present application.
In particular embodiments the analogue in iii) is at least 80% identical to a sequence as defined in i) or ii), such as at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or such as at least 99.5% identical to a sequence as defined in i) or ii).
Further, said rhGALC or said functionally equivalent part or analogue thereof may in particular be obtained by recombinant expression using a nucleic acid sequence comprising a sequence selected from the group consisting of:
It may further be preferred that the acid sequence in ii) is at least 80% identical to a sequence as defined in i), such as at least 85%, at least 90%, at least 95%, at least 98%, at least 99%, or such as at least 99.5% identical to a sequence as defined in i).
The term “sequence identity” indicates a quantitative measure of the degree of homology between two amino acid sequences or between two nucleic acid sequences of equal or unequal length. If the two sequences to be compared are not of equal length, they must be aligned to give the best possible fit, allowing the insertion of gaps or, alternatively, truncation at the ends of the polypeptide sequences or nucleotide sequences. The sequence identity can be calculated as
wherein Ndif is the total number of non-identical residues in the two sequences when aligned and wherein Nref is the number of residues in one of the sequences. Hence, the DNA sequence AGTCAGTC will have a sequence identity of 75% with the sequence AATCAATC (Ndif=2 and Nref=8). A gap is counted as non-identity of the specific residue(s), i.e. the DNA sequence AGTGTC will have a sequence identity of 75% with the DNA sequence AGTCAGTC (Ndif=2 and Nref=8).
Pre-Resin Steps
The cell culture which provides the unpurfied rhGALC may come from different sources. In an embodiment the cell culture is provided from a bioreactor expressing rhGALC.
It may be an advantage to modify the fraction of the cell culture before applying to the first chromatographic resin. Thus, in an embodiment the pH of the fraction is adjusted to below 7 before loading onto the first chromatographic resin such as in the range 3-7, such as in the range 4-7, such as in the range 5-7 such as in the range 6-7, such as in the range 3-6, such as in the range 3-5, or such as in the range 3-4. It may also be advantageous to filter (e.g. depth, dead end or tangential flow filter) or centrifuge the cell culture to remove the cells before loading. Thus, in another embodiment the fraction of said cell culture is a filtered fraction. In yet an embodiment said fraction of the cell culture comprising rhGALC is a clarified undiluted harvest.
First Resin Steps/Capture Steps
The first resin stabilizes the enzyme and removes the media color. Different types of multimodalities may be suitable for the first multimodal chromatographic resin. Thus, in an embodiment the first multimodal chromatographic resin binds through at least hydrophobic and electrostatic interactions. In another embodiment the first multimodal chromatographic resin binds through at least aromatic and electrostatic interactions.
The term “binds through”, when used to describe the binding capacity of a chromatographic resin, is not particularly limited, but typically refers to non-covalent binding. The material that binds to the chromatographic resin, as specified herein, typically comprises one or more proteins, such as in particular rhGALC and/or host cell proteins (HCP).
The first multimodal resin comprises a base matrix. The base matrix is a water-insoluble material, usually in particle from or gel form. One example of a suitable base matrix is agarose, for example highly rigid agarose.
The first multimodal chromatographic resin comprises a ligand which is capable of binding through the above described types of interaction. Thus, in an embodiment the first multimodal chromatographic resin comprises a ligand which is capable of at least hydrophobic and electrostatic interactions. Preferred ligands of that embodiment comprise at least one hydrophobic group and at least one positively and/or negatively charged group. In another embodiment the first multimodal chromatographic resin comprises a ligand which is capable of at least aromatic and electrostatic interactions. Preferred ligands of that embodiment comprise at least one aromatic group and at least one positively and/or negatively charged group.
The ligand is part of the the resin, preferably by virtue of covalent binding, directly or indirectly, to the base matrix. Although not strictly required, it is preferable that the ligand is indirectly bound to the base matrix through a linker. Thus, in preferred embodiments, which are exemplified herein, the first multimodal chromatographic resin comprises (a) a linker and (b) one or more a functional groups. In that embodiment, the ligand preferably consists of (a) linker and (b) one or more a functional groups. All linkers and all functional groups described herein are combinable with each other, unless the context clearly dictates otherwise. A linker may alternatively be referred to as “spacer”. By covalently binding to the linker (as more preferred), or to the resin directly (as less preferred), the one or more functional groups are immobilized.
Thus, in typical embodiments the first multimodal chromatographic resin comprises a linker. The type of linker is not particularly limited, but preferred linkers are suitably selected from the group comprising the compounds of the formula (II), (III) or (X) below. Linkers with hydrophilic groups, such as for example OH groups, are preferred in many embodiments; examples thereof are given in formulas (II) and (X).
Formula (I) is one example of a suitable ligand. As can be taken from formula (I), the respective ligand comprises an aromatic group, a charged group and a hydrophilic linker. Further suitable ligands will be described in the following, by reference to (a) linkers and (b) functional groups. The said first multi modal chromatographic resin may comprise as ligand (a) a linker compound selected from the formulas (II), (III) and (X), and (b) a functional group selected from the formulas (IV), (V) or (VI) below.
In a preferred embodiment, the first multi modal chromatographic resin comprises formula (IV) as a functional group. The functional group represented by formula (IV) is also known as Cibracon Blue, and may be attached to the base matrix of the resin by different types of spacers/linkers. Formulas (II) and (X) are examples of hydrophilic spacers to which the ligand of Formula (IV) may be immobilized to the base matrix. Immobilization may be via an amine bond.
Therefore, in another embodiment, the functional group represented by formula (IV) is attached to the base matrix of the resin by a hydrophilic spacer.
In preferred embodiments, the the functional group represented by formula (IV) is immobilized via an amide bond.
In particular, the said first multi modal chromatographic resin may comprise as ligand a compound of the formula (V) or (VI).
wherein R of the substances of formula (II), (III) and (X) is preferably a functional group of formula (IV):
Preferred ligands of the first multimodal chromatography resin may also suitably be selected among the following formulas (V) and (VI):
wherein R1 of the substances of formula (V) and (VI) is preferably a functional group of formula (XI):
and wherein R2 of the substances of formula (V) and (VI) is preferably a functional group of formula (XII):
Thus, in preferred embodiments the first chromatographic resin comprises a ligand selected from formula IV, formula V and formula VI. Specific resins of these embodiments are commercially available and thus, they can be suitably used as the first resin. Thus, in yet an embodiment the first resin is selected from the group consisting of “Capto™ MMC”, “Capto™ Blue” (Capto™ Blue (high sub) and Capto™ Blue (low)), Capto™ Adhere, and “Blue sepharose™ fast flow”; all available from GE Healthcare.
In the present context, the term “Capto™ Blue”, unless expressly specified otherwise, is to be understood as encompassing all resins available under the name “Capto™ Blue”, in particular both “Capto™ Blue (low sub)” and “Capto™ Blue (high sub)”. Capto™ Blue (low sub) is defined by formulas (II) and (IV), or alternatively by formulas (V), (XI) and (XII). Capto™ Blue (high sub) is defined by formulas (X) and (IV), or alternatively formulas (VI), (XI) and (XII).
Capto MMC is a multimodal cation exchanger. It contains a carboxylic group and thus its features partly resemble those of a weak cation exchanger. However, in addition to the ionic interactions several other types of interactions are involved, including hydrogen bonding and hydrophobic interaction. Capto™ Blue is an affinity bioprocess media that binds through aromatic and electrostatic interactions. The Capto adhere ligand, N-Benzyl-N-methyl ethanolamine, exhibits many functionalities for interaction. The most pronounced are ionic interaction, hydrogen bonding and hydrophobic interaction.
In other embodiments the first resin is selected from the group consisting of MEP HyperCel™ Mixed-Mode Chromatography Sorbent, which is commercially available form Pall Corporation. MEP HyperCel sorbent operates by a mixed-mode or multi-mode mechanism also described as Hydrophobic Charge Induction Chromatography (HCIC). HCIC is based on the pH-dependent behavior of ionizable, dual-mode ligands.
In particular embodiments the first resin has a ligand of formula (VI). “Capto™ Blue” (Capto™ Blue (high sub) for instance, in particular) is an example of such a resin.
It is of course to be understood that the process according to the invention may also include some standard steps known to the skilled person. Thus, in an embodiment the first chromatographic resin is preconditioned before loading. In another embodiment after step b) the first chromatographic resin is washed in a wash buffer. In a further embodiment the first chromatographic resin is washed in a wash buffer comprising at the most 20% of propylene glycol and/or ethylene glycol (v/v), such as at the most 15%, such as at the most 10%, such as at the most 5%, such as in the range 5-20%, such as 5-15%, or such as around 10% propylene glycol and/or ethylene glycol. In an embodiment the wash buffer at the most 20% propylene glycol. In another embodiment the wash buffer at the most 20% ethylene glycol. Since rhGALC is extremely hydrophobic propylene glycol and/or ethylene glycol are preferred eluants.
The first elution buffer may have different components. In an embodiment wherein the first resin is “Capto™ Blue”, the first elution buffer comprises a total concentration of propylene glycol and/or ethylene glycol (v/v) of 40-60%, such as 45-60%, such as 50-60%, such as 40-55% such as 40-50%, or such as around 50%. A high concentration of propylene glycol and/or ethylene glycol (v/v) is important for proper elution of the enzyme.
Following elution the buffer conditions may be changed. Thus, in an embodiment after step c) the total concentration of propylene glycol and/or ethylene glycol (v/v) in the first eluate is lowered to below 30% before step d), such as below 20%, such as below 15%, or such as below 10%. By lowering the concentration of propylene glycol and/or ethylene glycol the enzymatic stability of rhGALC is maintained. In a further embodiment after step c) the pH of the first eluate is adjusted to a pH in the range 5 to 6.5, such as 5.5 to 6.5 such as 5.7 to 6.3 or to around 6.1. Due to the pH sensitivity of rhGALC a pH in the range 6.0-6.6 is preferred. In yet a further embodiment, after step c) the level of detergent in the first eluate is adjusted to 0.01% to 5%, such as 0.5% to 5%, such as 0.5 to 4%, such as 0.5% to 3%, such as 0.5% to 2%, such as 0.5 to 1.5%. In another embodiment the detergent is a tween detergent such as tween 20, tween 40, tween 60 or tween 80. Tweens are also known as polysorbates The detergents should preferably be approved for human use, thus the detergent may e.g. also be Cremophor (Polyoxyl 35 castor oil) and Pluronic F-127.
In a further embodiment the first eluate is stored in the detergent for 5 hours to 48 hours, such as 10 hours to 3 hours, or such as 16 to 24 hours, e.g. at room temperature. By storing the first eluate for a longer period of time this step functions as a virus inactivation step, especially if the concentration of detergent is high such as 1%.
Before loading onto the second chromatographic resin, the first eluate may be preconditioned. Thus, in an embodiment, before step d) the first eluate is mixed with a preconditioning buffer for the second chromatographic resin. In yet an embodiment the mixture takes place by letting the first eluate enter directly into the preconditioning buffer for the second resin.
Second Resin Steps/Intermediate Steps
Different types of multimodalities may be suitable for the second multimodal chromatographic resin. Thus, in an embodiment the second chromatographic resin binds through ionic interactions, hydrogen binding and hydrophobic interactions. In another embodiment the second chromatographic resin comprises N-Benzyl-N-methyl ethanol amine as ligand. In a further embodiment the second chromatographic resin comprises a ligand of the formula:
or a ligand of the formula:
In a more specific embodiment the second chromatographic resin is selected from the group consisting of Capto™ Adhere, CHT Ceramic Hydroxyapatite Type I (CHT I) which is commercially available from Biorad, and MEP HyperCel™ Mixed-Mode Chromatography Sorbent, which is commercially available form Pall Corporation. Capto™ Adhere is a strong anion exchange bioprocess media with multimodal functionalities. It binds through ionic interactions, hydrogen binding and hydrophobic interaction. Ceramic Hydroxyapatite interacts with biomolecules by multiple modes: Cation exchange occurs when negatively charged phosphate groups interact with protein amino groups. Stronger coordination complexes can form between carboxyl clustes, phosphoryl moieties, or both, on biomolecules and the calcium sites on CHT ceramic hydroxyapatite via the mechanism of metal affinity. MEP HyperCel sorbent operates by a mixed-mode or multi-mode mechanism also described as Hydrophobic Charge Induction Chromatography (HCIC). HCIC is based on the pH-dependent behavior of ionizable, dual-mode ligands.
In particular embodiments the second resin comprises a ligand of the formula (VIII). Capto™ Adhere is an example of such a resin.
It is of course to be understood that the process according to the invention may also include some standard steps known to the skilled person. Thus, in an embodiment the second chromatographic resin is preconditioned before loading. In another embodiment, after step d), the second chromatographic resin is washed in a wash buffer. In a further embodiment, after step d) the second chromatographic resin is washed with a wash buffer with a pH in the range 3-5, such as 4-5, or such as 4.5-5. In yet a further embodiment the wash buffer further comprises an alcohol, such as isopropanol.
Different eluent buffers may be used for the second chromatographic resin. In an embodiment wherein the second chromatographic resin is Capto™ Adhere the second elution buffer comprises in the range 30-50% propylene glycol (v/v), such as 30-45%, such as 30-40%, such as 35-50%, such as 40-50%, or such as around 40%. As previously mentioned, since rhGALC is extremely hydrophobic propylene glycol and/or ethylene glycol are preferred eluents. Again rhGALC is also pH sensitive. Thus, in an embodiment the second elution buffer has a pH below 6 such as below 5, such as in the range 3-6, 4-6, or 4-5. In a further embodiment, before step f), the second eluate is mixed with a pre-conditioning buffer for the third chromatographic resin.
Possible Intermediate 2-Step Procedure
In some embodiments according to the invention, the intermediate step is performed as a 2-step procedure as described in the following:
Intermediate Step a)
Intermediate step a) in the 2-step procedure is performed essentially as described above; i.e. using a multi-modal resin and buffers as defined in connection with the second resin steps/intermediate steps.
Intermediate Step b)
Different types of modalities may be suitable in intermediate step b), including multimodal resins, hydrophobic resins and chromatographic resins comprises a ligand with an ether group.
In a more particular embodiment the chromatographic resin used in intermediate step b) is selected from the group consisting of “PPG-600M”, and “Toyopearl Phenyl-650M”, which are commercially available from Tosoh Bioscience, “Capto™ Blue” (Capto™ Blue (high sub) and Capto™ Blue (low)), “Capto™ Butyl”, Butyl-S Sepharose 6 (operated in bind-and-elute mode or in flow-through mode), and Macro-Prep Methyl HIC (operated in bind-and-elute mode or in flow-through mode) which is available from Biorad.
Toyopearl Phenyl-650M is a Hydrophobic Interaction Chromatography (HIC) medium. Capto™ Blue is an affinity bioprocess media that binds through aromatic and electrostatic interactions. “Capto™ Butyl” and Butyl-S Sepharose 6 are hydrophobic interaction chromatography (HIC) media. Macro-Prep methyl HIC support operates on a mechanism of interaction that is based on hydrophobicity and charge. The methyl groups are mildly hydrophobic. Depending on the pH of loading and elution buffers, the carboxyl groups can be exploited to ionically repel target molecules while the hydrophobic groups retain contaminants.
As the skilled person will realize, different eluent buffers may be used for the second chromatographic resin.
Third Resin Steps/Polishing Steps
Different types of modalities may be suitable for the third chromatographic resin. Thus, in an embodiment the third chromatographic resin comprises a ligand comprising an ether group. In another embodiment the third resin is hydrophobic. In yet an embodiment the third chromatographic resin comprises [resin]-(OCH2CH2)nOH as a ligand, wherein n is an integer in the range 1-20 such as 1-10, such as 1-5, such as 1-3, or such as 1-2.
In a more specific embodiment the third chromatographic resin is selected from the group consisting of ether resins, including Toyopearl Ether resins, such as 650M, 650S 5PW, “PPG-600M” and Toyopearl GigaCap Q-650, which are commercially available from Tosoh Bioscience, CHT Ceramic Hydroxyapatite Type I (CHT I) which is commercially available from Biorad, Q Sepharose Fast Flow (Q FF), which is commercially available from GE Healthcare, MEP HyperCel™ Mixed-Mode Chromatography Sorbent, which is commercially available form Pall Corporation, Macro-Prep Methyl HIC (operated in bind-and-elute mode or in flow-through mode), which is commercially available from BioRad, and Butyl-S Sepharose 6 (operated in bind-and-elute mode or in flow-through mode) and Capto DEAE, which are both commercially available from GE Healthcare.
Ceramic Hydroxyapatite interacts with biomolecules by multiple modes: Cation exchange occurs when negatively charged phosphate groups interact with protein amino groups. Much stronger coordination complexes can form between carboxyl clustes, phosphoryl moieties, or both, on biomolecules and the calcium sites on CHT ceramic hydroxyapatite via the mechanism of metal affinity Q Sepharose Fast Flow is an ion exchange (IEX) chromatography medium (resin). MEP HyperCel sorbent operates by a mixed-mode or multi-mode mechanism also described as Hydrophobic Charge Induction Chromatography (HCIC). HCIC is based on the pH-dependent behavior of ionizable, dual-mode ligands. Toyopearl GigaCap Q-650 media is a high capacity, high resolution anion exchange resin, Macro-Prep methyl HIC support operates on a mechanism of interaction that is based on hydrophobicity and charge. Butyl-S Sepharose 6 is a hydrophobic interaction chromatography (HIC) medium.
In particular embodiments the third chromatographic resin is an ether resin, such as an ether resin selected from the group consisting of the said Toyopearl Ether resins, including 650M, 650S and 5PW. An advantage of this type of resin is that it does not require propylene/ethyleneglycol as eluent, but can use an aqueous eluent.
It is of course to be understood that the process according to the invention may also include some standard steps known to the skilled person. Thus, in an embodiment the third chromatographic resin is preconditioned before loading. Thus in an embodiment the preconditioning results in a buffer comprising 1-2 M NH4Ac and 1-2 M NH4Cl. In another embodiment, after step f) the third chromatographic resin is washed in a wash buffer. In yet an embodiment, after step f), the third chromatographic resin is washed with a wash buffer with a pH in the range 3-5, such as 4-5, such as 4.5-5, such as 5.5-7 or such as around 6.5. This is an advantage since rhGALC is pH sensitive.
Different wash buffers may be employed for the third resin. In an embodiment, after step f) the third chromatographic resin is washed with a first wash buffer comprising at least 1M NH4Ac, such as at least 2M or such as at least 3 M, or such as in the range 1-4M. In yet an embodiment the first wash buffer comprises at least 1M NH4Cl, such as at least 2M or such as at least 3 M, or such as in the range 1-3M and at least 0.1% detergent such as 0.1-2% detergent.
In an embodiment a second wash buffer contains lower salt and detergent concentrations than the first wash buffer. In yet an embodiment a third wash buffer contains lower salt concentrations than the second wash buffer. In a further embodiment the elution buffer is a sodium phosphate buffer.
For the purified rhGALC to be suitable for e.g. infusions into human the level of detergent should be low. Thus, in an embodiment the third elution buffer comprises below 1% detergent, such as below 0.01%, such as below 0.001%, such as below 0.001% detergent. In yet an embodiment the detergent is a tween detergent, such as tween 80 or tween 20. In another embodiment the third elution buffer has a pH in the range 5-7, such as 6-7, or such as 6.2-6.8.
To improve the elution step the elution buffer may comprise salt. Thus, in a further embodiment the third elution buffer comprises at least 100 mM salt, such as NaCl and/or KCl. NaCl and KCl may be excluded, but the product may then be somewhat less pure.
In yet an embodiment the content of the final product is adjusted to comprise at least 150mM mannitol, such as at least 200 mM mannitol, such as at least 250, or such as in the range 200-400 mM mannitol, The presence of mannitol allows the product to be freeze-dried.
Post Resin Steps
To further minimize the levels of e.g. virus and other unwanted cell impurities further purification may be used. Thus, in an embodiment, after step g), the third eluate is passed to through a filter with a maximum filter size of 0.1 μm. In a further embodiment, after step g), the third eluate is passed to through a size exclusion filter with a filter size of at the most 20 nanometer, such as at the most 15 nanometer, such as a Planova 15N filter.
In yet an embodiment, the third eluate is further passed through a ultrafiltration/diafiltration step with tangential flow filtration (TFF) using a membrane with molecular weight cut off (MWCO) of below 50 kDa, such as below 30 kDa, such as below 15 kDa or such as below 10 kDa. In a further embodiment the membrane is a polyether sulfone membrane, such as a Pellicon polyether sulfone membrane. In yet an embodiment the membrane is a regenerated cellulose membrane.
Additional Steps
In order to further improve product quality of the product according to the present invention it may be subjected to ionic separation. Optionally, the ionic separation may be applied between the capture step and the intermediate step, between the intermediate step and the polishing step or on the eluate from the polishing step
When performing ionic separation between the capture step and the intermediate step or after the polishing step, an anion filter or resin may be used, such as a Mustang® Q membrane, which is available from Pall Corporation. Mustang Q membranes are strong anion exchangers, which effectively bind plasmid DNA, negatively-charged proteins, and viral particles.
When performing ionic separation between intermediate step and the polishing step or after the plishing step it may be performed on a strong anion exchange (AIEX) resin, such as Capto Q, Giga Cap Q, Q FF. According to such embodiments, the resins are used in binding mode. It is also possible to include a weak anion exchange resin, such as Capto DEAE and DEAE FF, in particular when the polishing step uses hydrophobic interaction (HIC) chromatography.
In other embodiments the ionic separation may be applied immediately after the polishing step, such as immediately after elution from said ether resin.
In alternative embodiments the ionic separation may be applied after the ultrafiltration/diafiltration (UFDF) step.
Various different buffers may be used during the ionic separation. In particular embodiments, when applying ionic separation e.g. on a Mustang Q membrane immediately after the polishing step on ether resins, the anion filter or resin may be equilibrated with 3.7 mM sodium phosphate, 5 mM glycine, 10 mM mannitol, 0.075 M NaCl 0.0005% tween 80, pH 6.2. The product may be diluted 1:1 (v:v) with 3.7 mM sodium phosphate, 5 mM glycine, 10 mM mannitol, 0.0005% tween 80, pH 6.2 optionally with addition of 0.15 M NaCl, before it is run through the anion filter or resin.
In alternative embodiments, when applying ionic separation e.g. on a Mustang Q membrane after the UFDF step, the anion filter or resin may be equilibrated with 3.7 mM sodium phosphate, 0.2 M NaCl, 5 mM glycine, 10 mM mannitol, 0.0005% tween 80, pH 6.2 The product may be diluted with 1M NaCl until conductivity is 20 mS/cm (approximately 1 volume product: 0.2 volume 1 M NaCl) before running it through the anion filter or resin.
Before sterile filtration the product may according to these embodiments be diluted with formulation buffer, such as a formulation buffer without NaCl to bring conductivity back to 15 mS/cm (0.15 M NaCl).
Compositions
The purified rhGALC according to the present invention differs from other purified rhGALC's, e.g. by purity, specific enzymatic activity, and the presence of processed products. Thus, in an aspect the invention relates to a composition comprising rhGALC.
In particular the rhGALC is one that is obtainable by the purification process according to the present invention.
Other purified products may comprise processed products of rhGALC. In an embodiment the molar ratio between full length rhGALC (80 kDa) and the main processed products (50+30 kDa) in the composition is at least 50:2.5, such as at least 50:1, such as at least 100:1, such as at least 200:1, or such as 500:1. In another embodiment the ratio between full length rhGALC (80 kDa) and the two main processed products (30 kDa+50 kDa) in the composition is at least 50:2.5, such as at least 100:1, such as at least 200:1, such as 500:1. The processed 30 and 50 kDa forms of rhGALC could be seen as minor bands and were estimated to <0.5% (see example section and
In further embodiments, the composition according to the present invention contains very few host cell proteins. The skilled person will be aware of suitable methods for determining the content of host cell proteins and other contaminants. In particular, the level of host cell proteins may be determined by ELISA.
Generally, the content of host cell proteins is satisfactory if it is 500 ng/mg or less. In some embodiments of the invention, the content of host cell proteins is 450 ng/mg or less, such as 300 ng/mg or less, or such as 250 ng/mg or less. In yet an embodiment the amount of host cell proteins is below 200 ng/mg in the composition, such as below 100 ng/mg rhGALC, such as below 40 ng/mg rhGALC or such as below 30 ng/mg rhGALC. As can be seen from the example section impurities were estimated to around 30 ng HCP per mg rhGALC by ELISA.
In some embodiments of the invention, the content of host cell proteins is 20 ng/mg or less.
In yet an embodiment the enzymatic activity in the composition is at least 15 kU/mL or such as at least 30 kU/mL. As can be seen from the example section the enzymatic activity in the final product was estimated to 42.5 kU/mL. The composition according to the present invention has, as one of its characteristics, a very high content of monomeric (80 kDa) rhGALC and a very low content of aggregates (dimers and multimers of rhGALC). Preferably, the amounts of aggregates are below the minimum level of detection, such as when detected by visual inspection. If the visual inspection, i.e. inspection by eye, does not detect any aggregates, the rhAGA is to be considered as free of aggregates. The composition according to the invention which is free of aggregates will then appear clear and not cloudy.
Alternatively, formation of aggregates and levels of aggregates may be measured by transmittance at 580 nm (T580). Using this methods a transmittance of >95% such as >96%, >96.5%, >97%, >98% or more than >99%, indicates satisfactory levels of aggregates. Another commonly used method is SEC (size exclusion chromatography).
The skilled person will be aware of other suitable methods for measuring/assessing the level of protein aggregates, including dynamic light scattering and subvisual particles method (subvisual particle count).
In a preferred embodiment, less than 1.5% (w/w) of the rhGALC in said composition according to the invention is in the form of aggregates, such as less than 1% (w/w), e.g. less than 0.5% (w/w), less than 0.25%(w/w), less than 0.2% (w/w), less than 0.1% (w/w), less than 0.05% (w/w) or less than 0.01% (w/w). The content of monomeric (80 kDa) rhGALC s at least 95% (w/w), such as at least 96%(w/w), or at least 97% (w/w), e.g. at least 98% (w/w), preferably at least 98.5% ((w/w), at least 99.5% ((w/w), or 99% (w/w).
The compositions according to the present invention may find use as a medicament. Thus, an aspect of the present invention relates to the composition according to the present invention for use as a medicament.
In yet an aspect the invention relates to the composition according to the present invention for use in the treatment of Globoid Cell Leukodystrophy (Krabbe disease).
In a further aspect the invention relates to the use if the composition according to the present invention for the preparation of medicament for the treatment of Globoid Cell Leukodystrophy (Krabbe disease).
In yet a further aspect the invention relates to a method of treating Globoid Cell Leukodystrophy (Krabbe disease) and/or reducing or alleviating the symptoms associated with Globoid Cell Leukodystrophy (Krabbe disease), said method comprising a step of administering rhGALC or a composition comprising the same according to the present invention to a subject in need thereof. In said method, an effective amount of the rhGALC or a composition comprising the same is administered to a subject in need thereof. A subject in need thereof is typically a human subject which suffers from Krabbe disease, is at risk to suffer from Krabbe disease and/or does not express functional human GALC, or does not express the same in sufficient quantities. The rhGALC may be made available to the subject by enzyme replacement therapy (ERT).
It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.
All patent and non-patent references cited in the present application, are hereby incorporated by reference in their entirety.
The invention will now be described in further details in the following non-limiting examples.
A downstream process (DSP) for purification of recombinant human Galactocerebroside β-Galactosidase (rhGALC) resulting in a final product fulfilling quality and purity requirements for animal studies was developed and tested in pilot scale. The process consists of three chromatographic steps and one UFDF formulation step. In this study fresh and clarified harvest from a 20 L fed batch bioreactor was purified with an optimized process in pilot scale to produce rhGALC for animal studies and e.g. human treatment protocols. The protocol is summarized in
Equipment, Materials, Buffers and Methods
Equipment
Resins, Filters and Containers
Buffers
In Process Analysis
Enzymatic activity was measured by procedure 65; HNG assay for analyzing galactocerebrosidase (GALC). The in-house rhGALC standard StG01 is used for preparation of a standard curve.
Protein concentration: Protein concentration was measured by procedure 75; Protein determination of rhGALC using Pierce 660 nm Protein Assay. Dilutions of the in-house standard StG02 as standard curve. Protein concentration of StG02 was determined externally by amino acid analysis (AAA) (Amino acid Analysis Center, Uppsala University, Sweden).
For information A280 was measured dividing the observed absorbance with the theoretical extinction coefficient 2.5 of human GALC.
Specific activity was calculated by dividing enzymatic activity with rhGALC protein concentration.
Identity was analyzed by procedure 70, Western Blot analysis of recombinant human galactocerebrosidase (rhGALC). A polyclonal antibody, purified on Protein A sepharose, generated against the in-house standard StG02 was used for detection.
Isoelectric focusing (IEF) was analyzed by procedure 74 on Novex IEF gel pH 3-10 to evaluate the isoelectric point of rhGALC. The final product was compared to the in-house rhGALC standard StG03 as an additional measure of identity.
Purity was analyzed by procedure 69 with SDS-PAGE (4-12% Bis-Tris NuPAGE, MOPS buffer) stained with Colloidal Blue.
Impurities were analyzed by procedure 43; ELISA method for determination of CHO host cell proteins.
Tween concentration was quantified by procedure 73 with a RP-HPLC method.
Native PAGE was performed as a measure of rhGALC formations for information. The analysis was performed according to instructions from the manufacturer (Invitrogen).
Osmolality (Vapro osmometer) and pH (Metrohm) were measured in the final product TG1106.
Carbohydrate composition was measured mainly by instruction 25 (other dilutions of the standard) by HPLC with fluorescence detection of 2-AA labeled released monosaccharides.
Harvest:
After closing the bioreactor, sodium acetate, pH 5 is added to the harvest in the bioreactor to keep pH <7, which is optimal for the enzyme. The pH stabilized harvest is pumped out from the bioreactor through depth filters buffer, to remove the cells. The filters are rinsed with conditioning buffer after the filtration. The final mix of harvest to conditioning buffer should be ˜2:1 (w:w).
General Information About the Process Conditions:
The equilibration, loading and equilibration wash of the chromatographic steps are performed with a peristaltic pump with maximum flow rate 100 mL/min, corresponding to 150 cm/hr. The remaining parts of the runs are performed with the Biological Duo-Flow system upgraded with Maximizer 80, with maximum flow rate 80 mL/min, corresponding to 125 cm/hr. The flow rates can be adjusted if a more appropriate chromatographic system is used. However, buffers with propylene glycol (PG) should be run with the indicated flow rate.
All chromatographic steps are run in binding mode and contain several wash steps. High concentration of PG is needed for elution of the hydrophobic rhGALC from the first two steps in the process. To remain enzymatic activity the product needs to be collected into prefilled containers from these steps. No organic solvent is needed for elution from the polishing step.
All buffers, except Capto Blue conditioning buffer, contain detergent (tween 80), which appear necessary to keep the enzymatic activity of rhGALC. Harvest media contain pluronic, which replaces tween in the Capto Blue conditioning. Another motive for omitting tween in the conditioning is that it could cause opalescence of the harvest after ˜>6 hours of storage at room temperature.
Capto Blue
Capto™ Blue is an affinity bioprocess media that binds through aromatic and electrostatic interactions.
The term “Capto™ Blue”, unless expressly specified otherwise, is to be understood as encompassing all resins available under the name “Capto™ Blue”, in particular both “Capto™ Blue (low sub)” and “Capto™ Blue (high sub)”. Capto™ Blue (low sub) is defined by formulas (II) and (IV), or alternatively by formulas (V), (XI) and (XII). Capto™ Blue (high sub) is defined by formulas (X) and (IV), or alternatively formulas (VI), (XI) and (XII).
The conditioned harvest is loaded onto the Capto Blue column within 24 hours from clarification. From a 20 L bioreactor three cycles of Capto Blue in pilot scale (740 mL) is needed. The column is washed with equilibration buffer and a wash buffer containing 10% propylene glycol (PG) and 5% isopropanol (IPA). Elution is performed with a buffer containing 50% PG into a prefilled container. Collection into a container filled with elution mix buffer has three purposes:
As described above the Blue product may be collected into an elution mix buffer. The final tween concentration is 1% and the pool is stored for 16-24 hours at room temperature as a dedicated virus inactivation step.
Capto Adhere
Capto™ Adhere is a strong anion exchange bioprocess media with multimodal functionalities. It binds through ionic interactions, hydrogen binding and hydrophobic interaction.
The product from Capto Blue is loaded in three sequential cycles after maximum 4 days hold time onto the Capto Adhere column. The hold time period starts with 18-20 hours at room temperature as a virus inactivation step. In case of longer hold time the product pool is moved to 5±3° C. for the remaining time. It is moved back to room temperature 8-15 hours before the run to accumulate to room temperature. The product pool is loaded at pH 6.1. The pH is decreased fast to 4.7 by a wash at high ionic strength and IPA followed by a wash at low ionic strength. Elution is performed with buffer at pH 4.55 containing 40% PG into a prefilled container to increase pH and decrease PG concentration to keep the enzymatic activity of rhGALC.
Toyopearl Ether
Toyopearl Ether-650M is a methacrylic polymer (65 μm particle size) with high mechanical and chemical stability. Ether has the highest hydrophilicity in the Tosoh serie of hydrophobic interaction ligands and is designed for purification of very hydrophobic proteins.
The product from Capto Adhere is stored for maximum 24 hours at room temperature or 4 days at 5±3° C. If stored cold it is moved back to room temperature 8-15 hours before the run to accumulate to room temperature.
It is mixed 1:2.5 (w:w) with the Ether conditioning buffer (three cycles) containing high ammonium acetate, ammonium chloride and tween concentrations. The Ether column is equilibrated with a buffer with 200× lower tween concentration compared to the conditioned start. After loading the column is washed with equilibration buffer. The next wash step increases tween and salt. It is followed by a long wash with the equilibration buffer to decrease the tween concentrations again and a wash with a mix of equilibration and elution buffer to decrease ammonium salts. Elution is performed with a sodium phosphate buffer containing low tween (0.0005%) and sodium chloride, at pH 6.4.
Planova 15N Virus Filtration
In production scale the polishing step will be followed with nanofiltration through Planova 15N as a dedicated virus removal step.
UFDF
The three polishing product pools are pooled and formulated in one cycle of ultrafiltration/diafiltration (UFDF) with tangential flow filtration (TFF) using a Pellicon polyether sulfone membrane with molecular weight cut off (MWCO) 30 kDa. The feed channels are type V with open channels and the cassette area is 0.1 m2.
The pump is set to 230 rpm and transmembrane pressure (TMP) is 0.5 bar (0.6in/0.4out). The membrane is equilibrated with formulation buffer and the first volume of buffer is exchanged by dilution followed by concentration (UF) and 7 times diafiltration (DF). Totally eight volumes of buffer are exchanged.
Filtration and Filling
The UFDF product (retentate) is filtered through a 0.22 μm PES filter under aseptic condition in a LAF bench. The final product is filled into sterile containers of various volumes (0.25-20 mL per vial/bottle). The final product is named TG1106 and is stored frozen at −80±10° C.
Summary of Results
The total yield for the downstream process from clarified harvest from the 20 L bioreactor to final product was 74% based on activity.
The total activity in ˜19.5 L clarified harvest was 23 million Units. The total yield in the final product, TG1106, was 17 million Units or 1.0 g pure rhGALC.
Activity Yield and Conditions
The total yield (74%) and was calculated from clarified harvest to final product. The reason was that the clarification process was still not decided and not part of this study.
The chromatographic steps were run in three cycles. The three polishing step products were pooled and formulated in one UFDF. The UFDF product was sterile filtered and divided into containers. The yield, based on % activity for each step and cycle is shown in
The average yield for the capture step, Capto Blue, was 84±8.1%.
The average yield for the intermediate step, Capto Adhere, was 87±3.5%.
The average yield for the polishing step, Toyopearl Ether, was 76±0.6%*
The yield for the UFDF step was 117%.
The yield for the final sterile filtration was 102%.
Analyses Results
In process samples and final product were analyzed by a set of analytical methods as described above. The table below summarizes the analytical results for final product TG1106.
Identity—Western blot
The purified product was identified as human GALC by western blot analysis.
The proteins in the polishing products, the UFDF product and final product were separated by SDS-PAGE and electrophoretically transferred to a polyvinylidene difluoride (PVDF) membrane. rhGALC was detected with a polyclonal rabbit anti GALC antibody generated against the in-house rhGALC standard StG02. The antibodies had been purified on a Protein A sepharose column (GE Healthcare). They detect 80 kDa GALC as well as the 50 kDa and the 30 kDa processed forms of GALC. A prestained protein ladder was used to verify the transfer and to estimate apparent molecular weight (MW).
Isoelectric Focusing
The isoelectric point of final product TG1106 was calculated to 6.35.
TG1106 and standard StG03 were separated according to charge on a pH 3-10 isoelectric (IEF) focusing gel. Electrophoresis was performed cold (on ice) at 100V for 1 hour, then 200V for 1 hour and finally 500V for 2 hours. The gel, shown in
Purity-SDS-PAGE
The purity in final product TG1106 was estimated to >99%. Processed rhGALC was estimated to <0.5%.
The in process samples were separated, mainly according to size, by electrophoresis (SDS-PAGE), on a NuPAGE 4-12% Bis-Tris gel with MOPS buffer. rhGALC and potential impurities were visualized by Colloidal Blue. Colloidal Blue has a dynamic linear response that is independent on type of protein, meaning that as long as the protein concentrations are sufficient it is preferable for estimation of degree of purity compared to silver staining. The apparent molecular weight (MW) of rhGALC is 80 kDa, while processed forms have apparent molecular weights of 50 and 30 kDa.
The 160 kDa band might be an artifact. It could be that at high rhGALC concentration the SDS in the sample buffer is not sufficient for forming monomers of the rhGALC multimers (see Native PAGE, 7.2.5). But if not, estimation could be that the intensity of the “dimer” for TG1106 16 μg load is similar as the 80 kDa band for StG03 0.36 μg load, meaning ˜2% of this form in the final product.
Native PAGE
Native PAGE shows that the major formation of rhGALC is the dimer, but multimers with up to 10 rhGALC molecules exists.
Native PAGE was run for information of rhGALC formations at neutral pH. As seen in
Impurities-HCP ELISA
Residual CHO cell host cell proteins (HCP) were quantified to 30 ng/mg rhGALC in final product TG1106.
Chinese hamster ovary (CHO) host cell proteins (HCP) were analyzed as a measure of impurities. Generic antibodies purchased from Cygnus Technologies were used in the ELISA. The antibodies were generated from cell proteins typically secreted (3G 0016-AF) as well as from intracellular proteins (C0016-PA) from CHO cells. The standard was prepared from 10% lysed and 90% secreted HCP from parental CHO (DG44 strain) cells.
HCP were measured after the Ether steps, the UFDF step and in the final product. The rhGALC in-house standard StG02 and Tox ASA were analyzed as references. As seen in table 23 the process reduced the HCP levels to 30 ng/mg rhGALC in final product TG1106. Residual HCP levels were similar in the Ether product and in the final product indicating that the UFDF step did not remove any additional HCP.
HCP levels after Ether, UFDF and in final product TG1106. StG02, StG03 and Tox ASA are references.
Monosaccharide Composition
The preliminary degree of glyscosylation was estimated to 7% and each mol rhGALC contained 2-3 mol mannose-6-phoshate residues.
Only one preliminary analysis was performed of final product TG1106. It indicates that rhGALC has ˜7% carbohydrates (w:w). The glycosylation is most likely of high mannose type.
The preliminary data indicate the following mol of each monosaccharide per mol rhGALC:
Discussion
The optimized three chromatographic step process described in here produced a pure rhGALC product that fulfills quality requirements for animal studies and most likely also clinical studies. DNA remains to be analyzed.
The yield from bioreactor B5:19, based on enzymatic activity from clarified harvest to final product was 74%. Having in mind that GALC is a very hydrophobic protein this was especially satisfactory.
The clarification of harvest was the only step without acceptable yield. Since there are possible improvements to be evaluated the DSP yield was calculated from clarified and conditioned harvest. Around 20% activity was lost by the depth filtration. An earlier study indicated that TFF could improve the clarification yield. The total yield, including the clarification, was 58%.
The theoretical pI of GALC is 5.9, while the found pI was 6.3. Since rhGALC contains acid M6P and sialic acid this was surprising. Experiments, prior to this study, have shown rhGALC to be very pH sensitive; for long storage periods it is only stable around its pI; pH 6.0-6.6. Theoretically, pH around the pI should be avoided in a DSP to avoid precipitation, but for the rhGALC DSP it is the only possibility. The product has been clear throughout the DSP and no tendency of opalescence has been seen. An explanation for the high pI could be that tween/rhGALC micelle formations alter the exposed amino acids from the predicted. Tween was included in all DSP buffers (except Blue conditioning, where it is replaced by pluronic) to maintain enzymatic activity. The minimum tween concentration for keeping the stability remains to be evaluated.
Elution from both the capture and intermediate steps were complicated. Propylene glycol (PG) was a prerequisite for both elution buffers. In addition, other additives and careful optimization of the buffers were required for optimal yield. A drawback could be that highly hydrophobic contaminants may co-elute with rhGALC. Prosaposin, a 70 kDa hydrophobic protein, was identified (western blot with a saposin A antibody) as contaminant after the capture and the intermediate step. High concentration of PG is not optimal for rhGALC enzymatic activity and thus collection was in prefilled containers.
Some additional stepwise comments to the process:
The capture step, Capto™ Blue, stabilized the enzyme and removed the media color, which was its major goal. Of major importance for the yield was to prepare the elution buffer correctly. It must contain 50% (v:v) propylene glycol, which corresponds to 521 g/L buffer.
The intermediate step, Capto™ Adhere, removed the bulk of contaminants. Acidic conditions were needed for elution. To avoid precipitation of protein it was of importance to change to acidic conditions fast, by a buffer with high ionic strength. The buffer was then changed to an acidic buffer with low ionic strength. The reasons were that additional impurities were removed and to assure that the eluted product was acidic, but with low ionic strength to be able to fast change pH back >6 by collection into a prefilled container with pH 6.5 buffer.
Toyopearl Ether combined a sufficient yield using aqueous buffers, without any organic solvents such as PG and IPA, with the possibility to remove the final HCP with hydrophobic characteristics. An advantage was that elution with acceptable yield was possible with a phosphate buffer with sodium chloride. A drawback was that extreme salt concentrations were needed for binding of rhGALC. A large volume of conditioning buffer was needed, making the loading time long. This step was powerful in separating rhGALC from contaminants with similar characteristics as rhGALC. Of importance for a robust clearance of contaminants was the repeated alteration, both in tween and salt concentrations, which could be described as wash and rinse cycles. No prosaposine could be identified after the Ether step.
Two dedicated virus inactivation/removal steps are part of the process in productions scale. No virus spiking experiments have been performed, but regarding yield and flux the steps look promising.
A detergent inactivation step was combined with the elution from the capture step. The high tween concentration had no negative influence on the binding to the intermediate column and the enzymatic activity remained after storage at room temperature for 24 hours (also if combined with 3 days storage at +5° C.). The plan is to have a virus filtration step, Planova 15N, after the Ether step. This was found feasible in an earlier study and it was not repeated. Preliminary large scale estimation approximates that 80 L product can be filtered through 1 m2 Planova 15N in ˜5 hours.
UFDF, with a V-screen 30 kDa MWCO filter, was used for formulation and concentration after the polishing step. The V screen filter, with open channels, is only available in pilot scale (0.1 m2) that requires large amounts of product for optimization studies. The conditions have been modified in small steps based on the three UFDF runs in the previous study. A drawback with UFDF could be that tween accumulates. The Ether products were washed and eluted with buffer containing only 0.0005% tween. It was difficult to quantify the tween in the Ether product, but an estimate was ˜0.003%. The UFDF/formulation buffer contained 0.0005% tween. After 8 volumes of buffer exchange and ˜7 times concentration the tween concentration was ˜0.025%. The UFDF product was easily 0.22 μm filtered with no loss of product into the final product.
Preliminary data indicate that this tween concentration in combination with the other components of the formulation buffer is optimal for keeping rhGALC stability for long term storage at +5, −20, −80° C. It is possible to freeze dry the product, if mannitol is increased to 250 mM.
SDS-PAGE followed by Colloidal Blue staining showed a pure final product; >99%. The processed 30 and 50 kDa forms of rhGALC could be seen as minor bands and were estimated to <0.5%. The most pronounced (˜2%) visualized protein apart from the 80 kDa rhGALC form was a 160 kDa rhGALC form seen only if high concentration of rhGALC was mixed with SDS-PAGE sample buffer. Western blot analysis verified that the protein contained rhGALC, maybe as dimer that was not sufficiently dissolved by SDS under reduced conditions. Maybe this “dimer” was only an artifact. Native PAGE, at neutral pH, indicated that rhGALC has several formations, from monomers to formations of rhGALC multimers of ˜10 molecules. The most common formation seemed to be the dimer
Conclusion and Summary
Recombinant human GALC, expressed in CHO cells, were cultured in one 20 L bioreactors at the Royal Institute of Technology, Stockholm, Sweden. 19.5 L harvest was purified to 17 million Units or 1.0 g pure rhGALC with a downstream process consisting of three chromatographic steps; Capto Blue, Capto Adhere and Toyopearl Ether, all run in binding mode. A virus inactivation step consisting of 16-24 hours incubation at room temperature with 1% tween 80 was performed after Capto Blue. The product was formulated by tangential flow filtration and sterile filtered to the final product TG1106.
The harvest was stabilized by addition of sodium acetate to the bioreactor before clarification by depth filtration and conditioning for binding to the capture column, Capto Blue. The conditioned harvest was loaded onto the 730 mL Capto Blue column in three cycles performed within 24 hours. The product was eluted with a 50% propylene glycol buffer into a “three-purpose” buffer to reduce propylene glycol, increase tween as a dedicated virus inactivation step and condition the start for the next step. The conditioned start was loaded onto the 730 mL Capto Adhere column in three sequential cycles. The product was eluted with acidic pH and propylene glycol into a buffer that reduced propylene glycol and increased pH to keep the activity. After additional mixing with a buffer with ammonium acetate and ammonium chloride the conditioned start was loaded onto the 540 mL Toyopearl Ether column in three sequential runs. The product was eluted in a phosphate buffer containing sodium chloride and a low tween concentration. The plan is to include a virus filtration step after the polishing step, but it was excluded in this study. The polishing products were pooled, buffer changed and concentrated by UFDF to a formulation buffer optimal for long term storage of pure rhGALC. The UFDF product was sterile filtered into the final product. The final product was analyzed by a set of analytical methods. The protein concentration is 2.5 mg/mL and the enzymatic activity 42.5 kU/mL, resulting in a specific activity of 16.9 kU/mg. The estimated purity is >99%. Residual HCP are 30 ng/mg rhGALC. The final product is clear and colorless.
In conclusion, the new optimized DSP has been scaled up successfully to pilot scale resulting in a yield of 74%, based on activity. The final product TG1106 fulfills quality requirements for animal studies.
Examples with Ionic Separation:
Ionic separation was tested as described below with satisfactory results.
1) Mustang Q (MQ) is a disposable membrane with anionic support. It was tested in combination with the current process in flow through mode (impurities such as DNA and host cell proteins bind to the membrane and GALC flows through). It was tested either before the Ether step or after the UFDF (formulation step. It was also tested in line with Capto Blue, also in flow through mode.
2) A strong anion exchange (AIEX) resin, such as Capto Q, Giga Cap Q, Q FF, can be included in the downstream process in binding mode. It is also possible to include a weak anion exchange resin such as Capto DEAE and DEAE FF but the remaining impurities were found higher. It may be used before or after the polishing step (hydrophobic interaction (HIC)).
Procedure 1:
Procedure 2:
The following multimodal resins were tested with satisfactory results:
1) MMC Capture (very early experiments)
Results: Presence of enzyme was analyzed using Dot-Blot method. Enzyme was detected in Start (+++) and in Elution—fraction 1 (++). No enzyme detected in flow through. SDS-PAGE and HPLC analyses were performed on fractions
2) Butyl-S as 2nd intermediate step or as polishing step:
3) PPG as 2nd intermediate step (ex test 44-47)
The following combinations of resins were tested with satisfactory results:
Preliminary test: average approximately 350 ng HCP/mg GALC
Test 1: 240 ng HCP/mg GALC
Test 2: 430 ng HCP/mg GALC
Test 3: 78 ng HCP/mg GALC
Test 4: 50 ng HCP/mg GALC (but opalescence due to virus inactivation with IPA+tween)
Test 5: 193 ngHCP/mg GALC
Test 6: 79 ngHCP/mg GALC
HNG assay for analyzing galactocerebrosidase (GALC) activity
Principle
Galactocerebrosidase (GALC) is responsible for the lysosomal catabolism of galactocerebroside (=galactosylceramide), a major lipid in myelin, kidney and epithelial cells. GALC hydrolyzes the galactose ester bonds of galactocerebroside, galactosylsphingosine, lactosylceramide, and monogalactosyldiglyceride. GALC is also able to hydrolyze the synthetic analogue of galactocerebroside, a chromogenic substrate, 2-hexadecanoylamino-4-nitrophenyl-b-D-galactopyranoside (HNG). The sodium salt of the product of the reaction, 2-hexadecanoylamino-4-nitrophenol (HN), absorbs light at 410 nm. This principle is utilized in the method described herein.
Analysis principle for GALC. HNG is hydrolyzed by GALC into HN (at pH 4.5), a yellow colored product (at pH 10.5), which is determined spectrophotometrically at 410 nm.
Hydrolytic cleavage of 2-hexadecanoylamino-4-nitrophenyl-b-D-galactopyranoside
Sample Preparation
Harvest or Purified GALC
Desired dilutions of samples were prepared using 0.5% Triton X-100. At least a dilution 1:10 was required for analysis.
Cell-Lysate
Cell-pellets were washed in PBS, pelleted by centrifugation (400×g for 5 min at RT) and lysed in 0.5% Triton X-100. Protein determination of cell-lysate was performed using the BCA Protein Assay Kit Microtiter Plate Protocol (Pierce). A typical experiment was performed using 1-5 mg cell-lysate proteins.
Preparation of a Standard Curve and Assay Control
The first in-house rhGALC standard StG01 was used for preparation of a standard curve. True replicas of five dilutions (1/400, 1/600, 1/800, 1/1200 and 1/1600) were prepared.
The second rhGALC standard StG02 was used for preparation of an assay control:
Incubation Procedure
Measurements of A410 nm
Measurements were performed using Spectra Max Plus plate reader or a BioTek plate reader.
Calculations
Definition: One unit (1 U) of enzyme activity was defined as the hydrolysis of 1 nmol HN per minute at 37° C., pH 4.5.
The mean HNG-activity of the first in-house rhGALC standard StG01 was set to 1884 U/ml. The activities used for the standard curve were calculated from dilutions of the mean StG01 HNG-activity:
Calculation of Specific Activity
The concentration of GALC in mixed samples was determined using GALC ELISA. Protein concentration in purified preparations of GALC was determined using A280 (the theoretical specific absorption coefficient for rhGALC is 2.5) or the 660 nm Protein Assay.
To calculate the specific activity (Units/mg) or the enzymatic activity per mg protein (Units/mg protein), the HNG activity was divided with the concentration of GALC or protein.
Originally, the GALC activity of cell-lysate has been defined as nmol hydrolyzed product per mg per hour (nmol/mg/h). To convert Units/mg to nmol/mg/h multiply by 60 (i.e. convert minutes to hour).
Preferred Items of the Present Invention
1. A process for purifying recombinant human Galactocerebroside β-Galactosidase (rhGALC) from a cell culture, wherein a fraction of said cell culture comprising rhGALC is subjected to chromatography on resins, the process comprising
2. The process according to item 1, wherein said intermediate step comprises purification of said rhGALC on a said second multimodal chromatographic resin, followed by purification of said rhGALC on a chromatography resin selected from the group consisting of:
3. The process according to item 2, wherein said first and second multimodal chromatography resins are, different resins.
4. The process according to any of the preceding items, wherein said first multimodal chromatographic resin comprises electrostatic ligands.
5. The process according to any of the preceding items, wherein said second multimodal chromatographic resin comprises an anionic and hydrophobic ligand.
6. The process according to any of the preceding items, wherein the chromatographic resin in said polishing step is a resin having hydrophobic ligands.
7. The process according to any of the preceding items, wherein said rhGALC is eluted from said first multimodal chromatographic resin in first elution buffer comprising at least 30% propylene glycol and/or ethylene glycol (v/v).
8. The process according to any of the preceding items, wherein said rhGALC is eluted from said second multimodal chromatographic resin in a second elution buffer comprising at least 30% propylene glycol and/or ethylene glycol (v/v)) and having a pH below 5.5.
9. The process according to any of the preceding items, said process comprising
10. The process according to any of the preceding items, wherein the first first multimodal chromatographic resin binds through at least hydrophobic and electrostatic interactions.
11. The process according to any of the preceding items, wherein the first multimodal chromatographic resin comprises as ligand a compound of the formula (I), (II), (III) (V), (VI) or (X):
wherein R of the substances of formula (II), (III) and (X) is a functional group of formula (IV):
wherein R1 of the substances of formula (V) and (VI) is a functional group of formula (XI):
and wherein R2 of the substances of formula (V) and (VI) is a functional group of formula (XII):
12. The process according to any of the preceding items, wherein said first multimodal chromatographic resin comprises as ligand a compound of the formula (VI).
13. The process according to any of the preceding items, wherein said second multimodal chromatographic resin comprises as ligand a compound of the formula (VIII).
14. The process according to any of the preceding items, wherein the first chromatographic resin is washed in a wash buffer comprising at the most 20% of propylene glycol and/or ethylene glycol (v/v).
15. The process according to any of the preceding items, wherein the first elution buffer comprises a total concentration of propylene glycol and/or ethylene glycol (v/v) of 40-60%.
16. The process according to any of items 9-15, wherein after step c) the total concentration of propylene glycol and/or ethylene glycol (v/v) in the first eluate is lowered to below 30% before step d).
17. The process according to any of items 9-16, wherein after step c) the level of detergent in the first eluate is adjusted to 0.01% to 5%.
18. The process according to any of the preceding items, wherein the second multimodal chromatographic resin binds through ionic interactions, hydrogen binding and hydrophobic interactions.
19. The process according to any of the preceding items, wherein the second multimodal chromatographic resin comprises a ligand of the formula:
or a ligand of the formula
20. The process according to any of items 9-19, wherein the second elution buffer comprises in the range 30-50% propylene glycol and/or ethylene glycol (v/v).
21. The process according to any of the preceding items, wherein the third chromatographic resin comprises a ligand comprising an ether group.
22. The process according to any of items 9-21, wherein the third chromatographic resin comprises [resin]-(OCH2CH2)nOH as a ligand, wherein n is an integer in the range 1-20 such as 1-10, such as 1-5, such as 1-3, or such as 1-2.
23. A composition comprising rhGALC, wherein the molar ratio between full length rhGALC (80 kDa) and the main processed products (50+30 kDa) in said composition is at least 50:2.5.
24. The composition according to item 23, wherein the amount of host cell proteins is below 200 ng/mg rhGALC.
25. The composition according to item 21 or 22, wherein the enzymatic activity is at least 15 kU/mL.
26. The composition according to any of items 23-25 wherein there are no aggregates as determined by visual inspection.
27. The composition according to any of items 23-26, which is obtainable by the purification process according to any of the items 1-22.
28. The composition according to any of items 23-27 for use as a medicament.
29. The composition according to any of items 23-27 for use in the treatment of Globoid Cell Leukodystrophy (Krabbe disease).
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2012 70699 | Nov 2012 | DK | national |
This application is a continuation-in-part application of U.S. application Ser. No. 14/437,463, filed Apr. 21, 2015, which is a U.S. National Phase Application of PCT International Application Number PCT/DK2013/050378, filed on Nov. 13, 2013, designating the United States of America and published in the English language, which is an International Application of and claims the benefit of priority to Danish Patent Application No. PA 2012 70699, filed on Nov. 13, 2012. The disclosures of the above-referenced applications are hereby expressly incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14437463 | Apr 2015 | US |
| Child | 15821223 | US |
