Patent Application
20210189359
This application contains a sequence listing submitted in accordance with 37 C.F.R. 1.821, named 13177N 2396US ZHAN sequence listing.txt, created on Dec. 21, 2020, having a size of 67,608 bytes, which is incorporated herein by this reference.
The presently-disclosed subject matter relates to fusion proteins comprising butyrylcholinesterase (BChE) and having an improved production yield and biological half-life.
Human plasma butyrylcholinesterase (BChE) has a long history of clinical application, without any adverse events reported [1]. Two clinical trials (NCT00333515 and NCT00333528) of BChE protein were performed by Baxter Healthcare Corporation, showing that recombinant human BChE is also safe for use in humans.
It has been well known that BChE can intercept and destroy the organophosphorus (OP) nerve poisons before they reach their target—acetylcholinesterase (AChE) [1-3]. Thus, administration of BChE is recognized as an effective and safe medication for the prevention of organophosphorus (OP) nerve agent toxicity [3-6].
Because of the stoichiometric binding of BChE with OP nerve agent, a large amount of BChE protein is required to achieve its nerve protective effects in vivo. Thus, without an efficient BChE expression method, the clinical application of BChE is severely impeded by its actual availability, since the quantity of BChE protein purified from human plasma is very limited. Hence, it is highly desired to develop methods that can be used to efficiently produce BChE in a large-scale for further preclinical and clinical development.
Another driving force to solve this protein production problem comes from the potential application of mutant BChE for treatment of cocaine abuse. BChE is a major metabolic enzyme that catalyzes the hydrolysis of cocaine to produce biologically inactive metabolites. Unfortunately, the catalytic efficiency (kcat/KM) of wild-type BChE against naturally occurring (−)-cocaine is too low (kcat=4.1 min−1 and KM=4.5 μM) [7] to be effective for accelerating cocaine metabolism. Through structure and mechanism based computational design and wet experimental tests, a series of human BChE mutants with significantly improved catalytic efficiency against cocaine have been designed and discovered [7-12]. These BChE mutants have been recognized as true cocaine hydrolases (CocHs) in literature [8] when they have at least 1,000-fold improved catalytic efficiency against (−)-cocaine compared to wild-type human BChE [9-12].
The CocH-based approach has been recognized as a truly promising strategy for treatment of cocaine overdose and addiction [8, 13-15]. Thus, it is critical for further preclinical and clinical development towards the actual use of a BChE mutant in clinical practice to improve the protein production efficiency of the BChE and its mutants.
In fact, extensive efforts have been made to improve the protein production, with the goal to economically produce recombinant human BChE or BChE mutants. Expression in bacteria is recognized as the most economical method for producing recombinant proteins, but wild-type BChE expressed in bacteria cannot fold appropriately to become an active enzyme [16]. BChE proteins expressed in silkworm and insect cells were proven to be active [17, 18], but their pharmacokinetic profiles have not been characterized. Transgenic plants and animals were also generated to produce BChE or CocHs with a significantly improved efficiency, but the proteins produced usually have significantly shorter biological half-lives [19-22]. The short biological half-life is mainly explained by possibly incomplete post-translational modification causing the BChE or CocH to be taken up by asialo receptors in the liver [1].
Compared to all the expression systems above, CHO (Chinese-hamster ovary) cells provide more consistently proper protein post-translational modification [23].Considering that the improper post-translational modification would not only shorten the protein's biological half-life, but also increase the risk of immunogenicity as an improper glycan structure might cause the protein to be recognized as an immunogen [1], CHO cells might be the most propriate system to produce the desirably safe and effective BChE (or BChE mutant) with a relatively long biological half-life. However, the biological half-life of the recombinant BChE or mutant produced in CHO [19-22, 24, 25] is still much shorter than that of native BChE. For example, CocH3 produced in CHO cells has a biological half-life of 7.3 hr in rats, which is considerably longer than that (˜13 min) of CocH3 expressed in plants [19, 24], but it is still much shorter than that (43 hr) of native BChE [26]. In addition, the low expression yield of BChE or its mutant in CHO cells is another major problem.
Thus, there remains a need in the art to efficiently produce active recombinant BChE and CocHs with a sufficiently long biological half-life
The presently disclosed subject matter identifies fusion proteins comprising BChE polypeptides that not only have a long biological half-life, but also a significantly-improved yield of protein production. Such polypeptides have utility in therapeutic treatment, for example, treatment of cocaine overdose and addiction, and treatment of OP detoxication.
The presently-disclosed subject matter meets some or all of the above-identified needs, as will become evident to those of ordinary skill in the art after a study of information provided in this document.
This Summary describes several embodiments of the presently-disclosed subject matter, and in many cases lists variations and permutations of these embodiments. This Summary is merely exemplary of the numerous and varied embodiments. Mention of one or more representative features of a given embodiment is likewise exemplary. Such an embodiment can typically exist with or without the feature(s) mentioned; likewise, those features can be applied to other embodiments of the presently-disclosed subject matter, whether listed in this Summary or not. To avoid excessive repetition, this Summary does not list or suggest all possible combinations of such features.
The presently-disclosed subject matter includes fusion proteins comprising butyrylcholinesterase (BChE) and having an improved production yield and biological half-life, and methods for production of such fusion proteins.
One embodiment of the present invention is a polypeptide molecule, comprising: an Fc polypeptide joined to an N-terminal end of a butyrylcholinesterase (BChE) polypeptide. In other embodiments of the present invention, an Fc polypeptide is joined to a C-terminal end of a butyrylcholinesterase (BChE) polypeptide. In some embodiments of the present invention, the Fc polypeptide is optionally joined to the BChE polypeptide via a linker, the linker comprising a sequence selected from the sequences of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 19, SEQ ID NO: 36, and SEQ ID NO: 37. In certain embodiments of the present invention, the Fc polypeptide has the sequence of SEQ ID NO: 8, or a fragment thereof, wherein the Fc polypeptide or fragment thereof includes 3 to 8 amino acid substitutions at 3 to 8 of residues selected from 1, 6, 12, 15, 24, 38, 40, 42, 58, 69, 80, 98, 101, 142, and 144. In further embodiments of the present invention, the Fc polypeptide is a fragment wherein 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 amino acids are removed from the N-terminus of SEQ ID NO: 8. In some embodimetns, the Fc polypeptide includes mutations as set forth in Table A, relative to SEQ ID NO: 8.
In some embodiments, the BChE polypeptide is an BChE polypeptide fragment that further includes amino acid substitutions as set forth in Table B, relative to SEQ ID NO: 10.
In some embodiments of the present invention, the Fc polypeptide is selected from SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 31, SEQ ID NO: 32, SEQ ID NO: 33, and SEQ ID NO: 34. In furether embodiments, the BChE polypeptide has the sequence of SEQ ID NO: 10 or a fragment thereof, wherein the BChE polypeptide or fragment thereof includes 3 to 8 amino acid substitutions at 3 to 8 of residues chosen from 199, 227, 285, 286, 287, 328, 332, and 441. In other embodiments, the BChE polypeptide has a group of amino acid substitutions selected from A199S, F227A, F227S, F227Q, F227I, F227G, F227V, F227L, F227L, F227S, F227T, F227M, F227C, P285A, P285S, P285Q, P285I, P285G, P285M, P285N, P285E, S287G, A328W, Y332G, E441D, and combinations thereof. In other embodiments of the presently disclosed matter, the BChE polypeptide is a fragment wherein from 1 to 116 amino acids are removed from the N-terminus of SEQ ID NO: 10. In some embodiments of the invention, the BChE polypeptide is a fragment wherein from 1 to 432 amino acids are removed from the C-terminus of SEQ ID NO: 10. In some embodiments, the BChE polypeptide has a group of amino acid substitutions selected from A199S, F227A, F227S, F227Q, F227I, F227G, F227V, F227I, F227L, F227S, F227T, F227M, F227C, P285A, P285S, P285Q, P285I, P285G, P285M, P285N, P285E, S287G, A328W, Y332G, E441D, and combinations thereof. In other embodiments of the present invention, the transient expression level of the polypeptide is at least about 9 times higher than a reference BChE polypeptide that does not include the Fc polypeptide and linker. In some embodiments of the present invention, the polypeptide molecule is the polypeptide of SEQ ID NO: 35. In other embodiments, the BChE polypeptide is selected from: SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, and SEQ ID NO: 15. In further embodiments, Fc polypeptide is selected from SEQ ID NO: 16, SEQ ID NO: 17, and SEQ ID NO: 18.
The presently-disclosed subject matter also relates to a nucleotide molecule, comprising: a nucleotide encoding an Fc polypeptide joined by a nucleotide encoding a linker to a 5′ end of a nucleotide encoding a butyrylcholinesterase (BChE) polypeptide. In some embodiments, the nucleotide encoding the linker comprises a sequence chosen from the sequences of SEQ ID NO: 1, SEQ ID NO: 3, and SEQ ID NO: 5. In some embodiments,) the nucleotide encoding the Fc polypeptide has the sequence of SEQ ID NO: 7 or a fragment thereof, wherein the Fc polypeptide or fragment thereof includes 3 to 8 amino acid substitutions at 3 to 8 of residues chosen from 1, 6, 12, 15, 24, 38, 40, 42, 58, 69, 80, 98, 101, 142, and 144 relative to SEQ ID NO: 8. In further embodiments, the nucleotide encoding the BChE polypeptide has the sequence of SEQ ID NO: 9 or a fragment thereof, wherein the BChE polypeptide or fragment thereof includes 3 to 8 amino acid substitutions at 3 to 8 of residues chosen from 199, 227, 285, 286, 287, 328, 332, and 441 relative to SEQ ID NO: 10. In some embodiments of the present invention, the nucleotide molecule is within an expression vector.
The present invention also relates to a method of producing a polypeptide molecule including a BChE polypeptide, comprising: (a) providing in a vector a nucleotide sequence chosen from (i) a nucleotide sequence encoding the polypeptide molecule of claim 1, or (ii) a nucleotide sequence of claim 14; and (b) transfecting cells with the vector and allowing the cells to express the polypeptide molecule; and (c) isolating the polypeptide molecule. In further embodiments, there is at least about a 9-fold improvement in the yield of expression of the polypeptide molecule as compared to expression of a reference BChE polypeptide.
The presently-disclosed subject matter will be better understood, and features, aspects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such detailed description makes reference to the following drawings, wherein:
FIG.1 includes a schematic illustrating four Fc-fused protein with various linkers, as well as a non-linked Fc-BChE. The small grey box represents an IL-2 secretion signal peptide; the black box represents the sequence of a Fc polypeptide, as disclosed herein; and the white box represents the sequence of a BChE polypeptide, as disclosed herein.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described below in detail. It should be understood, however, that the description of specific embodiments is not intended to limit the disclosure to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.
The details of one or more embodiments of the presently-disclosed subject matter are set forth in this document. Modifications to embodiments described in this document, and other embodiments, will be evident to those of ordinary skill in the art after a study of the information provided in this document. The information provided in this document, and particularly the specific details of the described exemplary embodiments, is provided primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom. In case of conflict, the specification of this document, including definitions, will control.
While the terms used herein are believed to be well understood by those of ordinary skill in the art, certain definitions are set forth to facilitate explanation of the presently-disclosed subject matter.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which the invention(s) belong.
All patents, patent applications, published applications and publications, GenBank sequences, databases, websites and other published materials referred to throughout the entire disclosure herein, unless noted otherwise, are incorporated by reference in their entirety.
Where reference is made to a URL or other such identifier or address, it understood that such identifiers can change and particular information on the internet can come and go, but equivalent information can be found by searching the internet. Reference thereto evidences the availability and public dissemination of such information.
As used herein, the abbreviations for any protective groups, amino acids and other compounds, are, unless indicated otherwise, in accord with their common usage, recognized abbreviations, or the IUPAC-IUB Commission on Biochemical Nomenclature (see, Biochem. (1972) 11(9):1726-1732).
Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently-disclosed subject matter, representative methods, devices, and materials are described herein.
Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used in this application, including the claims. Thus, for example, reference to “a biomarker” includes a plurality of such biomarkers, and so forth.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification and claims are approximations that can vary depending upon the desired properties sought to be obtained by the presently-disclosed subject matter.
As used herein, the term “about,” when referring to a value or to an amount of mass, weight, time, volume, width, length, height, concentration or percentage is meant to encompass variations of in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, as such variations are appropriate to perform the disclosed method.
As used herein, ranges can be expressed as from “about” one particular value, and/or to “about” another particular value. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.
As used herein, “optional” or “optionally” means that the subsequently described event or circumstance does or does not occur and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, an optionally variant portion means that the portion is variant or non-variant.
As used herein, the term “subject” refers to a target of administration. The subject of the herein disclosed methods can be a mammal. Thus, the subject of the herein disclosed methods can be a human, non-human primate, horse, pig, rabbit, dog, sheep, goat, cow, cat, guinea pig or rodent. The term does not denote a particular age or sex. Thus, adult and newborn subjects, as well as fetuses, whether male or female, are intended to be covered. A “patient” refers to a subject afflicted with a disease or disorder. The term “patient” includes human and veterinary subjects.
As used herein, the term “BChE polypeptide” can refer to various mutations and truncations of the BChE protein including the mutations that are characterized by cocaine hydrolase (CoCH). BChE polypeptide for example includes, but it not limited to, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, and SEQ ID NO: 15.
The fusion proteins as disclosed herein were designed in view of a number of considerations. For example, they make use of a protein that is normally expressed in a high level as the N-terminal fusion partner to improve the expression of protein of interest [27, 28]. It was contemplated that the N-terminal fusion partner could “fool” the cellular process into expressing the fusion protein at a high level [28]. For another example, human IgG has a very long biological half-life (t1/2). The fragment crystallizable (Fc) region of IgG binds to the neonatal Fc receptor (FcRn) in the acidic environment of the endosome and later is transported to the cell surface where, upon exposure to a neutral pH, IgG is released back into the main bloodstream [29 ]. In addition, IgG is the most common type of antibody found in the circulation, and can be expressed in CHO cells with a yield of more than 1 g/L [30].
The present inventors sought to design a long-acting CocH form which has not only a prolonged biological half-life without affecting the catalytic activity, but also an improved expression level in CHO cells. For this purpose, exemplary embodiments were prepared for testing, starting from CocH3 (the A199S/F227A/S287G/A328W/Y332G mutant [9] of human BChE) (SEQ ID NO: 12), a IL-2 signal peptide followed by Fc(M3) (the A1V/D142E/L144M mutant [−] of Fc)(SEQ ID NO: 16), which was fused with the N-terminal of CocH3(SEQ ID NO: 12). Then the tetramerization domain (amino-acid residues 530 to 574) of CocH3 was deleted to minimize the possibility of affecting the correct folding of Fc(M3) or CocH3. On the other hand, it was contemplated that the presence of Fc(M3) might break the tetramer structure, resulting in a long and flexible peptide, which could be proteolyzed easily. In addition, according to computational modeling (data not shown), directly fusing Fc(M3) with the N-terminal of CocH3 could affect the entrance of substrate to the active site of CocH3, thus affecting the catalytic activity of CocH3. Hence, several types of linkers were selected and inserted between Fc(M3) and CocH3. In this way, various Fc(M3)-linker-CocH3 entities were prepared and tested for their catalytic activity against cocaine, protein expression yields in CHO cells, and pharmacokinetic profile (for the most promising entity), leading to identification of a promising Fc(M3)-linker-CocH3 entity, as discussed below.
MATERIALS AND METHODS
Materials
Q5® Site-Directed Mutagenesis Kit was ordered from New England Biolabs (Ipswich, Mass.). All oligonucleotides were synthesized by Eurofins MWG Operon (Huntsville, Ala). Chinese Hamster Ovary-suspension (CHO-S) cells, FreeStyle™ CHO Expression Medium, Fetal Bovine Serum (FBS), 4-12% Tris-Glycine Mini Protein Gel, and SimpleBlue SafeStain were obtained from Invitrogen (Grand Island, N.Y.). TransIT-PRO® Transfection Kit was purchased from Minis (Madison, Wis). The rmp Protein A Sepharose Fast Flow was from GE Healthcare Life Sciences (Pittsburgh, Pa.). (−)-Cocaine was provided by the National Institute on Drug Abuse (NIDA) Drug Supply Program (Bethesda, Md.); and [3H](−)-Cocaine (50 Ci/mmol) was obtained from PerkinElmer (Waltham, Mass.). All other materials were from Sigma-Aldrich (St Louis, Mo.) or Thermo Fisher Scientific (Waltham, Mass.).
Preparation of gene fusion constructs in pCMV-MCS
Q5® Site-Directed Mutagenesis Kit was used to introduce each linker between Fc(M3) and CocH3. The pCMV-Fc(M3)-CocH3, constructed in a previous study [32] to encode N-terminal Fc-fused CocH3 without a linker, was used as the template. PCR reactions with Q5 hot start high-fidelity DNA polymerase along with primers listed in Table 1 were utilized to create insertions. Then 1 μl of each PCR product was incubated with Kinase-Ligase-Dpnl enzyme mix for 15 minutes at room temperature. These steps allowed for rapid circulation of the PCR product and removal of the template DNA. 5 μl of final product was added to 50 μl of chemically-competent E. coli cells for transformation. All obtained plasmid encoding different Fc-fused CocH3 were confirmed by DNA sequencing.
Expression and Purification
CHO-S cells were grown under the condition of 37° C. and 8% CO2 in a humidified atmosphere. Once cells grown to a density of ˜1.0×106 cells/ml, cells were transfected with plasmids encoding various proteins using TransITPRO® transfection kit. The culture medium was harvested 7 days after transfection. Enzyme secreted in the culture medium was purified by protein A affinity chromatography described previously [3 ]. Briefly, pre-equilibrated rmp Protein A Sepharose Fast Flow was mixed with cell-free medium, and incubated overnight at 6° C. with occasional stirring. Then the suspension was packed in a column, washed with 20 mM Tris·HCl (pH 7.4), and eluted by adjustment of salt concentration and pH. The eluate was concentrated and dialyzed in storage buffer (50 mM HEPES, 20% sorbitol, 1 M glycine, pH 7.4). Purified proteins were analyzed by native PAGE electrophoresis.
In vitro activity assay against (−)-cocaine.
A radiometric assay based on toluene extraction of [3H](−)-cocaine labeled on its benzene ring was used to determine the catalytic activity of proteins [9, 11, 33]. Reactions were initiated by adding 150 μl enzyme solution (100 mM phosphate buffer, pH 7.4) to 50 μl [3H](−)-cocaine solution with varying concentration. Then 200 μl of 0.1 M HCl was added to stop each reaction and neutralize the liberated benzoic acid while ensuring a positive charge on the residual (−)-cocaine. [3H] Benzoic acid was extracted by 1 ml of toluene and measured by scintillation counting. Catalytic rate constant (kcat) and Michaelis-Menten constant (Km) were determined by fitting the substrate concentration-dependent data using Michaelis-Menten kinetics.
Determination of Relative Expression Level of Proteins
Cells were grown in 12-well plates to a density of ˜1.0×106 cells/ml. Then cells were transfected with plasmids encoding different proteins using the same method described above. The test was tripled for each protein, occupying 3 out of 12 wells in a plate. Medium was collected from each well 3 days post the transfection. Cells were removed by centrifuge at 4000 rpm for 15 min, and the catalytic activity of each sample against cocaine was determined using radiometric assay described above. Protein concentration was calculated by dividing the catalytic activity by the kcat (determined by using the aforementioned purified protein) for each specific protein.
Determination of Biological half-life in Rats
Male Sprague-Darley rats (220-250 g) were ordered from Harlan (Harlan, Indianapolis, Ind.), and housed initially as one or two rats per cage. All rats were allowed ad libitum access to food and water and maintained on a 12 h light/12 h dark cycle, with the lights on at 8:00 a.m. at a room temperature of 21-22° C. Experiments were performed in a same colony room in accordance with the Guide for the Care and Use of Laboratory Animals as adopted and promulgated by the National Institutes of Health. The animal procedure was approved by the IACUC (Institutional Animal Care and Use Committee) as part of the animal protocol 2010-0722 on Jun. 21, 2016 at the University of Kentucky. Rats were injected with the purified Fc(M3)-(PAPAP)2-CocH3 protein via tail vein (0.075 mg/kg). Blood samples were collected from saphenous vein puncture. Approximately 100 μl blood was collected by using heparin-treated capillary tube at various time points after enzyme administration. Collected samples were centrifuged for 15 min at a speed of 5000 g to separate the plasma, which was kept at 4° C. before analysis. Radiometric assay using 100 μM (−)-cocaine was carried out to measure the active enzyme concentration in plasma.
Results and Discussion
Optimization of Fc-fused CocH3 entity with a linker
Four different linkers, including flexible linkers (GGGSGGGS) (SEQ ID NO: 6) (GGGGSGGGGS)(SEQ ID NO: 36), (GGGGGGSGGGGGGS)(SEQ ID NO: 37) and three rigid linkers (EAAAK-SEQ ID NO: 19), (PAPAP-SEQ ID NO: 4), and (PAPAPPAPAP-SEQ ID NO: 2), were utilized in this study. Previous studies reported in literature indicated that a linker similar to these could separate carrier protein and functional protein effectively and lead to improved biological activity of the fusion proteins with a linker. The four fusion proteins (see
To optimize the construct of Fc(M3)-CocH3, the above mentioned four linkers were used to eliminate the negative effects of N-terminal Fc portion on the catalytic activity of C-terminal CocH3. As seen in Table 2 and
Effects of the linker on the expression of Fc(M3)-fused CocH3 protein
Fc(M3)-EAAAK-CocH3, Fc(M3)-PAPAP-CocH3, and Fc(M3)-(PAPAP)2-CocH3 were further expressed together with Fc(M3)-CocH3 and the unfused CocH3 for comparison of relevant protein expression levels. All five proteins were expressed in the same plate under the same conditions at the same time. Cells in each well transfected using the same method and cultured under the same conditions after the transfection. All media were collected 3 days after the transfection. Protein expression level in each well was determined using the radiometric assay using 100 μM [3H](−)-cocaine. As seen in Table 3, the expression of the unfused CocH3 was 0.5 mg/L 3 days after the transient transfection. Usually, inserting the Fc portion at the N-terminal of the target protein could significantly improve the protein expression level. In this study, directly fusing Fc to the N-terminal of CocH3 increased the protein expression level by ˜2-fold. However, as Fc(M3)-CocH3 protein had only −30% catalytic activity against cocaine as compared to the unfused CocH3 [32]. As Fc(M3) domain sterically interferes with the CocH3 domain activity and lowers its catalytic activity against cocaine, it is also possible that this steric interference affects the efficiency of the protein folding. Therefore, an appropriate linker capable of avoiding such steric interference may not only improve the catalytic activity against cocaine, but also increase the protein expression level. As shown in Table 3, the protein expression yields of Fc(M3)-EAAAK-CocH3 and Fc(M3)-PAPAP-CocH3 was 4.8, and 5.2 mg/L, respectively. Linkers EAAAK, and PAPAP improved the yield of Fc(M3)-CocH3 protein expression by ˜9 and ˜10 folds, respectively. Among all fusion proteins constructed in this study, Fc(M3)-(PAPAP)2-CocH3 has the highest protein expression yield. The linker (PAPAPPAPAP) increased the yield of protein expression by ˜10 fold compared to the corresponding fusion protein without a linker. Further, compared to the corresponding unfused protein (CocH3), Fc(M3)-(PAPAP)2-CocH3 had a ˜21-fold improved yield of protein expression.
It should be pointed out that the transient expression method (with the protein expression within only three days) in this study was used only for the purpose of comparing the relative expression levels of various fusion proteins and unfused protein under the same conditions. So, the key results of this study are the relative protein expression levels, rather than the absolute protein expression levels. The absolute protein expression levels are expected tko significantly increase when the stable CHO cell lines are developed and used to express the same proteins; of course, development of a stable cell line is a very time-consuming process. For example, using a lentivirus-based repeated-transduction method which was established in a previous study [24], the protein expression yield of the unfused CocH3 reached ˜10 mg/L in a flask-based culture. Thus, one would reasonably expect that an appropriately developed stable CHO cell line might be able to express ˜200 mg/L Fc(M3)-(PAPAP)2-CocH3 protein by using the same lentivirus-based repeated-transduction method. The protein expression yield could be improved further by optimizing of the culture conditions, such as cell density, medium, and culture temperature.
Biological half-life of Fc(M3)-(PAPAP)2-CocH3 in Rats
Pharmacokinetic testing was carried out to determine biological half-life of Fc(M3)-(PAPAP)2-CocH3. Rats (n=3) were administered IV with 0.075 mg/kg of the purified protein. The blood was collected at 1 hr, 4 hr, 8 hr, 12 hr, 1 day and once each day within 14 days after the enzyme injection. Depicted in
aBiological half-life of enzyme was reported in ref. [26].
bBiological half-life of enzyme was reported in ref. [21].
cBiological half-life of enzyme was reported in ref. [19].
dData from ref. [24].
eData from ref. [31].
A previously reported study [31] demonstrated that a single injection of CocH-Fc(M3) was able to accelerate cocaine metabolism in rats after 20 days and, thus, block cocaine-induced physiological and toxic effects for a long period [31]. The CocH3-Fc(M3) protein was expected to allow dosing once every 2-4 wk, or longer, for treating cocaine addiction in humans. Given the facts that Fc(M3)-(PAPAP)2-CocH3 has the similarly long biological half-life in rats and same catalytic activity against cocaine, it is reasonable to expect that Fc(M3)-(PAPAP)2-CocH3 may also be able to provide the similar efficacy and duration for the cocaine addiction treatment.
It has been a significant challenge to efficiently express BChE polypeptides with both a long biological half-life comparable to the native BChE purified from human plasma and a high yield of protein expression. In this study, it has been demonstrated that an exemplary polypeptides including a BChE polypeptide molecule have not only a long biological half-life, but also an improved yield of protein expression compared to CocH3 (e.g., ˜105 ±7 hr in rats and ˜21-fold improved yield for Fc(M3)-(PAPAP)2-CocH3).
In a further example of the present invention:
BChE or BChE(574) refers to the wild-type human butyrylcholinesterase (full-length protein, with 574 amino acids) (SEQ ID NO:10). BChE(xxx) refers to a trucated fragment (with only the first xxx amino acids) of human butyrylcholinesterase (SEQ ID NO:10).
BChE-Fc refers to a fusion protein in which the C-terminus of human BChE (SEQ ID No: 10) is fused to the N-terminus of the Fc portion of human IgG-1 (SEQ ID NO: 8) or (SEQ ID NO 10-SEQ ID NO: 8). BChE(xxx)-Fc refers to a fusion protein in which the C-terminus of BChE(xxx) fragment fused to the N-terminus of the Fc portion of human IgG-1. CocH is a BChE polypeptide with specific mutations. CocH-LAF generally represents a cocaine hydrolase (CocH) in a long-acting form (LAF).
According to the data in Table 5, BChE(529)-Fc can be expressed with a significantly improved yield (about ˜7 fold), compared BChE-Fc. Both the Fc fusion and BChE fragmentation did not significantly change the catalytic activity of BChE.
In light of the production data in Table 5, a further designed mutants of BChE(529)-Fc with an improved binding affinity with neonatal Fc receptor (FcRn) at pH 6 in order to further prolong the biological half-life (t1/2) in addition to the protein expression yield (see Table S2).
aThe protein expression level is also affected by the culture conditions. Listed here is the lower end of the protein expression level.
To illustrate the approach to the rational design and discovery of BChE(529)-Fc mutants with improved binding affinity with FcRn and prolonged biological half-lives, depicted in
CocH3 represents the A199S/F227A/S287G/A328W/Y332G mutant of human butyrylcholinesterase (BChE). The full-length BChE or CocH3 has 574 amino-acid residues. CocH3(xxx) refers to the fragment (with only the first xxx amino acids) of the A199S/F227A/S287G/A328W/Y332G mutant of human butyrylcholinesterase.
It will be understood that various details of the presently disclosed subject matter can be changed without departing from the scope of the subject matter disclosed herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference, including the references set forth in the following list:
This application claims priority from U.S. Provisional Patent Application No. 62/950,765 filed on Dec. 19, 2019 the entire disclosure of which is incorporated herein by this reference.
This invention was made with government support under Grant Numbers DA041115, DA035552, DA032910, DA013930, and DA025100 awarded by the National Institutes of Health (NIH) and grant number CHE-1111761 awarded by the National Science Foundation (NSF). The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62950765 | Dec 2019 | US |
