METHODS OF MANUFACTURING THERAPEUTIC PROTEINS

Abstract

Disclosed herein are methods of manufacturing therapeutic proteins.

Description

CROSS-REFERENCE

[0001] This application is a continuation of U.S. application Ser. No. 15/570,178, filed on Oct. 27, 2017, which is a U.S. National Stage Entry of PCT/US2016/029472, filed Apr. 27, 2016, which claims benefit of U.S. Provisional Patent Application No. 62/153,178 filed on Apr. 27, 2015.

SEQUENCE LISTING

[0002] The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jul. 1, 2020, is named 53744_701_301_SEQUENCE LISTING and is 26,682 bytes in size.

BACKGROUND OF THE INVENTION

[0003] The production of therapeutic proteins using mammalian cell expression systems is of growing importance within the biotechnology industry. Various culture and transfection systems have been described, but each has significant limitations.

SUMMARY OF THE INVENTION

[0004] The invention described herein is based, in part, on the discovery that the combination of cholesterol-auxotrophic cells with one or more additional selection markers can be exploited in methods of manufacturing therapeutic proteins, to avoid unexpected manufacturing complications associated with cholesterol-auxotrophic cells (e.g., low productivity). In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic and glutamine-auxotrophic cell; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a protein which is capable of restoring glutamine biosynthesis in the cell; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0005] In one embodiment, the cell is an NS0 cell.

[0006] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0007] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes a glutamine synthetase.

[0008] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0009] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (ii)) in the absence of exogenously introduced glutamine. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of a glutamine synthetase inhibitor (e.g., methionine sulfoximine). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0010] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the absence of exogenously introduced glutamine. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol, in the absence of exogenously introduced glutamine, and in the presence of a glutamine synthetase inhibitor (e.g., methionine sulfoximine). In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol and the cell is cultured (e.g., after transfection of nucleic acid (ii)) in the absence of exogenously introduced glutamine.

[0011] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a protein expressing one or more selectable marker; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0012] In one embodiment, the cell is an NS0 cell.

[0013] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0014] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain.

[0015] In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase.

[0016] In some embodiments, the nucleic acid (ii) encodes a glutamine synthetase, a dihydrofolate reductase (DHFR), or one or more antibiotic resistance gene (e.g., neomycin, blasticidin, hygromyocin, puromycin, zeocin, mycophenolic acid).

[0017] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0018] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol.

[0019] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that does not express a functional dihydrofolate reductase (DHFR); transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a DHFR; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0020] In one embodiment, the cell is an NS0 cell.

[0021] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0022] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase.

[0023] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0024] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of a DHFR inhibitor (e.g., methionine sulphoximine (MSX)). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0025] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of a DHFR inhibitor (e.g., methionine sulphoximine (MSX)).

[0026] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to neomycin; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a neomycin resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0027] In one embodiment, the cell is an NS0 cell.

[0028] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0029] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes the neomycin resistance gene from Tn5 encoding an aminoglycoside 3'-phosphotransferase (APH 3' II).

[0030] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0031] In some embodiments, both the first and second expression vector contains HC and LC one vector contains KSR and the other vector contains GS or another antibiotic resistant gene. In some embodiments, there are three separate vectors (e.g., for triple selection), wherein all three vectors contains HC and LC; a first vector contains KSR, a second vector contains GS, and a third vector contains any antibiotic resistant gene, e.g. NEO.

[0032] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of an aminoglycoside antibiotic (e.g., G418). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0033] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of an aminoglycoside antibiotic (e.g., G418).

[0034] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to blasticidin; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a blasticidin resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0035] In one embodiment, the cell is an NS0 cell.

[0036] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0037] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes the blasticidin resistance gene from Bacillus cereus (which codes for blasticidin-S deaminase).

[0038] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0039] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of a peptidyl nucleoside antibiotic (e.g., blasticidin). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0040] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of a peptidyl nucleoside antibiotic an aminoglycoside antibiotic (e.g., blasticidin).

[0041] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to hygromycin B; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a hygromycin B resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0042] In one embodiment, the cell is an NS0 cell.

[0043] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0044] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes a hygromycin B phosphotransferase.

[0045] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0046] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of an aminoglycoside antibiotic (e.g., hygromycin B). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0047] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of a peptidyl nucleoside antibiotic an aminoglycoside antibiotic (e.g., hygromycin B).

[0048] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to puromycin; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a puromycin resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0049] In one embodiment, the cell is an NS0 cell.

[0050] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0051] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes a puromycin N-acetyl-transferase.

[0052] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0053] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of an aminonucleoside antibiotic (e.g., puromycin). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0054] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of a peptidyl nucleoside antibiotic an aminonucleoside antibiotic (e.g., puromycin).

[0055] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to zeocin; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a zeocin resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0056] In one embodiment, the cell is an NS0 cell.

[0057] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0058] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes a Sh ble gene product.

[0059] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0060] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of a copper-chelated glycopeptide antibiotic (e.g., zeocin). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of a copper-chelated glycopeptide antibiotic (e.g., zeocin).

[0061] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to mycophenolic Acid (MPA); transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a MPA resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0062] In one embodiment, the cell is an NS0 cell.

[0063] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0064] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes the xanthine-guanine phosphoribosyltransferase (Ecogpt) gene.

[0065] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0066] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of MPA. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0067] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of MPA.

[0068] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic cell that is sensitive to mycophenolic acid (MPA); transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell; (ii) a nucleic acid encoding a MPA resistance gene; and (iii) a nucleic acid encoding the therapeutic protein; culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0069] In one embodiment, the cell is an NS0 cell.

[0070] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0071] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iii) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes the xanthine-guanine phosphoribosyltransferase (Ecogpt) gene.

[0072] In some embodiments, a first expression vector comprises nucleic acid (i) and (iii), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iii). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0073] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of MPA. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0074] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the presence of MPA.

[0075] In one aspect, the disclosure features methods of manufacturing a therapeutic protein, the method comprising: culturing a cholesterol-auxotrophic and glutamine-auxotrophic cell; transfecting the cell with (i) a nucleic acid encoding a protein which is capable of restoring cholesterol biosynthesis in the cell (e.g., KSR); (ii) a nucleic acid encoding a protein which is capable of restoring glutamine biosynthesis in the cell (e.g., glutathione synthetase); (iii) a nucleic acid encoding a protein which is capable of providing resistance to G418 (e.g., neomycin resistance gene); and (iv) a nucleic acid encoding the therapeutic protein (e.g., an antibody, e.g., a heavy chain and light chain); culturing the cell under conditions suitable for expression of the therapeutic protein; and isolating and/or purifying the therapeutic protein.

[0076] In some embodiments, nucleic acid (iii) is transfected first and during and/post transfection G418 is added to the cell culture media. In some embodiments, nucleic acid (iii) is transfected first and during and/or post transfection G418 is added to the cell culture media; and nucleic acid (ii) is transfected second and during and/or post transfection cholesterol is absent from the cell culture media. In some embodiments, nucleic acid (iii) is transfected first and during and/or post transfection G418 is added to the cell culture media; and nucleic acid (ii) is transfected second and during and/or post transfection cholesterol is absent from the cell culture media (e.g., exogenously added cholesterol); and nucleic acid (i) is transfected third and during/post transfection glutamine is absent from the cell culture medium (e.g., exogenously added glutamine) (optionally methionine sulphoximine (MSX) is added to the cell culture media).

[0077] In some embodiments, nucleic acid (ii) and (i) are transfected simultaneously, wherein G418 is added to the cell culture media and the cell culture media does not contain cholesterol (e.g., exogenously added cholesterol). In some embodiments, nucleic acids (i), (ii), (iii), and (iv) are transfected simultaneously, wherein the G418 is added to the cell culture media and the cell culture media does not contain cholesterol (e.g., exogenously added cholesterol) and does not contain glutamine (e.g., exogenously added glutamine) (optionally methionine sulphoximine (MSX) is added to the cell culture media). In some embodiments, nucleic acid (iv) is incorporated in the same nucleic acid sequence (e.g., vector) as each of (i), (ii), and (iii). In some embodiments, nucleic acid (iv) is incorporated in the same nucleic acid sequence (e.g., vector) as each of (i) and (ii); (i) and (iii); or (ii) and (iii). In some embodiments, nucleic acid (iv) encodes the heavy and light chain of a therapeutic antibody. In some embodiments, the light chain is incorporated in the same nucleic acid sequence (e.g., vector) as each of (i) and (ii); (i) and (iii); (ii) and (iii); or (i), (ii), and (iii). In some embodiments, the heavy chain is incorporated in the same nucleic acid sequence (e.g., vector) as each of (i) and (ii); (i) and (iii); (ii) and (iii); or (i), (ii), and (iii). In some embodiments, the light chain and heavy chain is incorporated in the same nucleic acid sequence (e.g., vector) as each of (i) and (ii); (i) and (iii); (ii) and (iii); or (i), (ii), and (iii).

[0078] In some embodiments, any of nucleic acids (i), (ii), (iii), and (iv) are incorporated into a single nucleic acid (e.g., single vector). For example, in some embodiments, nucleic acids (i) and (ii); (i) and (iii); (i) and (iv); (i), (ii), and (iii); (i), (ii), (iii), and (iv); (ii) and (iii); or (ii) and (iv); (iii) and (iv); are incorporated on a single nucleic acid. In some embodiments, nucleic acid (iv) comprises two separate nucleic acids, one encoding a heavy chain and one encoding a light chain of a therapeutic antibody. In some embodiments the heavy chain is incorporated onto another nucleic acid, e.g., (i), (ii), or (iii). In some embodiments the light chain is incorporated onto another nucleic acid, e.g., (i), (ii), or (iii).

[0079] In one embodiment, the cell is an NS0 cell.

[0080] In some embodiments, the therapeutic protein is an antibody. In some embodiments, the therapeutic protein is a fusion protein. In some embodiments, the therapeutic protein is an Fc-containing fusion protein.

[0081] In some embodiments, in the transfecting step the cell is transfected with nucleic acids (iv) encoding an antibody light chain and an antibody heavy chain. In some embodiments, nucleic acid (i) encodes a 3-ketosteroid reductase. In some embodiments, the nucleic acid (ii) encodes a glutamine synthetase. In some embodiments, the nucleic acid (iii) encodes neomycin resistance gene.

[0082] In some embodiments, a first expression vector comprises nucleic acid (i) and (iv), and a second expression vector comprises nucleic acids (ii). In some embodiments, a first expression vector comprises nucleic acid (i), and a second expression vector comprises nucleic acids (ii) and (iv). In some embodiments, transfection of the first expression vector is performed prior to transfection of the second expression vector. In some embodiments, transfection of the first expression vector is performed simultaneously with transfection of the second expression vector.

[0083] In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol. In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (ii)) in the absence of exogenously introduced glutamine. In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (ii)) in the presence of a glutamine synthetase inhibitor (e.g., methionine sulfoximine). In some embodiments, the cell is cultured (e.g., during and/or after transfection of nucleic acid (i)) in the presence of a 3-ketosteriod reductase inhibitor.

[0084] In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol and in the absence of exogenously introduced glutamine. In some embodiments, the cell is cultured in absence of exogenously introduced cholesterol, in the absence of exogenously introduced glutamine, and in the presence of a glutamine synthetase inhibitor (e.g., methionine sulfoximine). In some embodiments, the cell is cultured (e.g., after transfection of nucleic acid (i)) in the absence of exogenously introduced cholesterol and the cell is cultured (e.g., after transfection of nucleic acid (ii)) in the absence of exogenously introduced glutamine.

BRIEF DESCRIPTION OF THE FIGURES

[0085] FIG. 1 depicts an exemplary protocol of the methods described herein.

[0086] FIG. 2 depicts the NCBI reference amino acid sequence of 3-ketosteroid reductase (NP_057455) (SEQ ID No. 1).

[0087] FIG. 3 depicts the NCBI reference mRNA sequence of HSD17.beta.7 (NM_016371.3) (SEQ ID No. 2).

[0088] FIG. 4 depicts the NCBI reference amino acid sequence of glutamine synthetase (NP_002056.2) (SEQ ID No. 3).

[0089] FIG. 5A-E depicts the NCBI reference mRNA sequence of glutamine synthetase (NM_002065.6) (SEQ ID No. 4).

[0090] FIG. 6 depicts the NCBI reference amino acid sequence of dihydrofolate reductase (DHFR) (NP_000782.1) (SEQ ID No. 5).

[0091] FIG. 7A-B depicts the NCBI reference mRNA sequence of DHFR (NM_000791.3) (SEQ ID No. 6).

[0092] FIG. 8 depicts the stability of proteins produced using the 3-KSR cell culture system. FIG. 8 lists the final protein titer in the supernatant of 3-KSR cells for 10 different 3-KSR cell clones. Four clones (3-261, 3-330, 3-351, 3-497) demonstrated high protein titer. However, as further shown in FIG. 8 3-KSR clone 3-351, demonstrated a decline in cell specific productivity.

[0093] FIG. 9 is a line graph depicting cell selection using Neo (100 .mu.g/ml or 200 .mu.g/ml G418). The graph depicts the cell viability versus days post recovery.

[0094] FIG. 10 is a line graph depicting cell selection using glutathione synthetase (GS) (reduce glutamine concentration from 2 mM to 0 mM or from 0.5 mM to 0 mM respectively). The graph depicts the cell viability versus days post recovery.

[0095] FIG. 11 is a line graph depicting cell selection using 3-KSR, neo, and GS as a triple selection. The graph depicts the cell viability versus days post recovery. Resistance to G418 can be conferred by neo gene. The concentration of G418 in NS0 is 100 ug/ml and 200 ug/ml; reduce glutamine concentration from 2 mM to 0 mM, or from 0.5 mM to 0 mM. An MSX inhibitor may also be used to inhibit the GS activity.

DETAILED DESCRIPTION OF THE INVENTION

[0096] In certain recombinant protein production systems, such as NS0 host cell systems, cholesterol-auxotrophy is exploited by incorporating a 3-ketosteroid reductase (3-KSR) gene into the vector encoding the therapeutic protein, and recombinant cells selected for by removing cholesterol from the culture media (US20100028940). However, the inventors of the present disclosure unexpectedly found that this system can suffer from low productivity (e.g., protein product per cell per day) and low protein titers due to the difficulty of amplification in this cell line (see e.g., FIG. 8). In other NS0 host cell systems, glutamine-auxotrophy is exploited by incorporating a glutamine synthetase (GS) gene into the vector encoding the therapeutic protein, and transfected cells are selected for by removing glutamine from the culture media. In addition, a GS inhibitor can be added to the culture media to drive selection towards the incorporation multiple copies of the GS gene and therefore the gene encoding the protein of interest (Barnes et al. Cytotechnology. 2000. Advances in animal cell recombinant protein production: GS-NS0 expression system February; 32(2):109-23). Each system has different limitations. Described herein are alternate methods of manufacturing therapeutic products in, e.g., an NS0 host cell system.

[0097] A "glutamine-auxotrophic" cell as used herein is defined as a cell which does not synthesize any glutamine or does not synthesize enough glutamine to be capable of survival and growth in glutamine-free cell culture medium.

[0098] A "cholesterol-auxotrophic" cell as used herein is defined as a cell which does not synthesize any cholesterol or does not synthesize enough cholesterol to be capable of survival and growth in cholesterol-free cell culture medium.

[0099] "Restoring glutamine biosynthesis" as used herein means increasing the level of glutamine biosynthesis in a cell (from the level in a glutamine-auxotrophic cell), to at least a level which enables the cell to survive and grow in glutamine-free cell culture medium.

[0100] "Restoring cholesterol biosynthesis" as used herein means increasing the level of cholesterol biosynthesis in a cell (from the level in a cholesterol-auxotrophic cell), to at least a level which enables the cell to survive and grow in cholesterol-free cell culture medium.

[0101] "Survive and grow" or "survival and growth" as used herein refers to the ability of a cell or culture of cells to maintain greater than 60% cell viability during log phase growth as measured by trypan blue exclusion.

3-Ketosteroid Reductase (KSR)

[0102] The enzyme 3-ketosteroid reductase is encoded by the HSD17.beta.7 gene, and functions as a 3-ketosteroid reductase in the biosynthesis of cholesterol (Marijanovic et al., Mol Endocrinol. 2003 September; 17(9):1715-25). See FIG. 2 (SEQ ID No. 1) and FIG. 3 (SEQ ID No. 2) respectively, for NCBI reference amino acid (NP_057455) and mRNA sequence (NM_016371.3).

Glutamine Synthetase (GS)

[0103] The enzyme glutamine synthetase encoded by the glutamine synthetase gene catalyzes the synthesis of glutamine from glutamate and ammonia (Eisenberg et al., Biochimica et Biophysica Acta, 2000, Vol 1477, 122-145). Several alternatively spliced transcript variants have been found for this gene. See FIG. 4 (SEQ ID No. 3) and FIG. 5 (SEQ ID No. 4) respectively, for NCBI reference amino acid NP_002056.2 and mRNA sequence NM_002065.6.

Dihydrofolate Reductase (DHFR)

[0104] The enzyme DHFR is encoded by the DHFR gene, and converts dihydrofolate into tetrahydrofolate, a methyl group shuttle required for the de novo synthesis of purines, thymidylic acid, and certain amino acids. Several alternatively spliced transcript variants have been found for this gene. See FIG. 6 (SEQ ID No. 5) and FIG. 7 (SEQ ID No. 6) respectively, for NCBI reference amino acid (NP_000782.1) and mRNA sequence (NM_000791.3).

Antibiotic Resistance Gene Selection Markers

[0105] Antibiotic resistance genes are commonly used positive selection markers used in mammalian cell culture (see e.g., Antibody Expression and Production, Editor Mohamed Al-Rubeai, Springer Netherlands, Springer Science Business Media B.V., ISBN 978-94-007-1256-0; Cell Line Development, Mohamed Al-Rubeai Aug. 11, 2009 Springer Science & Business Media). Exemplary antibiotic resistance genes include but are not limited to genes conferring resistance to neomycin resistance gene, blasticidin, hygromyocin, puromycin, zeocin, mycophenolic acid. Suitable antibiotic resistance genes and corresponding inhibitors for use in cell selection would be known to one of skill in the art.

TABLE-US-00001 TABLE 1 Exemplary Antibiotic Selection Markers Antibiotic Mechanism of Action Resistance Gene Hygromycin Hygromycin B is an The hph gene. B aminoglycoside antibiotic produced by Streptomyces hygroscopicus. Hygromycin B inhibits protein synthesis. It has been reported to interfere with translocation and to cause mistranslation at the 70S ribosome. Zeocin .RTM. Zeocin .RTM. is a copper-chelated The Sh ble gene. glycopeptide antibiotic produced by Streptomyces CL990. Zeocin .TM. causes cell death by intercalating into DNA and cleaving it. Blasticidin Blasticidin is a peptidyl nucleoside The blasticidin antibiotic isolated from resistance gene Streptomyces griseochromogenes from Bacillus that inhibits protein synthesis by cereus (bsr), which interfering with the peptide-bond codes for blasticidin- formation in the ribosomal S deaminase. machinery. Puromycin Puromycin is an aminonucleoside The Pac gene encoding antibiotic produced by a puromycin N-acetyl- Streptomyces alboniger. It transferase (PAC) that specifically inhibits peptidyl was found in a transfer on both prokaryotic and Streptomyces producer eukaryotic ribosomes. strain. Geneticin G418 (Geneticin) is an The Neomycin aminoglycoside antibiotic similar resistance gene in structure to gentamicin B1, (neo) from Tn5 produced by Micromonospora encoding an rhodorangea. G418 blocks aminoglycoside 3'- polypeptide synthesis by inhibiting phosphotransferase, the elongation step in both APH 3' II. prokaryotic and eukaryotic cells. Phleomycin Phleomycin is a glycopeptide The Sh ble gene from antibiotic of the bleomycin family, Streptoalloteichus isolated from a mutant strain of hindustanus which Streptomyces verticillus. It binds encodes a protein that and intercalates DNA thus binds to phleomycin, destroying the integrity of the inhibiting its DNA double helix. cleavage activity.

Vectors, Host Cells, and Therapeutic Protein Production

[0106] The therapeutic proteins of the invention can be produced from a host cell. A host cell refers to a vehicle that includes the necessary cellular components, e.g., organelles, needed to express the polypeptides and constructs described herein from their corresponding nucleic acids. The nucleic acids may be included in nucleic acid vectors that can be introduced into the host cell by conventional techniques known in the art (e.g., transformation, transfection, electroporation, calcium phosphate precipitation, direct microinjection, infection, etc). The choice of nucleic acid vectors depends in part on the host cells to be used. Generally, preferred host cells are of either prokaryotic (e.g., bacterial) or eukaryotic (e.g., mammalian) origin.

[0107] Nucleic Acid Vector Construction and Host Cells

[0108] A nucleic acid sequence encoding the amino acid sequence of a therapeutic protein of the invention may be prepared by a variety of methods known in the art. These methods include, but are not limited to, oligonucleotide-mediated (or site-directed) mutagenesis and PCR mutagenesis. A nucleic acid molecule encoding a therapeutic protein of the invention may be obtained using standard techniques, e.g., gene synthesis. Alternatively, a nucleic acid molecule encoding a wild-type therapeutic protein may be mutated to contain specific amino acid substitutions using standard techniques in the art, e.g., QuikChange.TM. mutagenesis. Nucleic acid molecules can be synthesized using a nucleotide synthesizer or PCR techniques.

[0109] Nucleic acid sequences encoding a therapeutic protein of the invention may be inserted into a vector capable of replicating and expressing the nucleic acid molecules in prokaryotic or eukaryotic host cells. Many vectors are available in the art and can be used for the purpose of the invention. Each vector may contain various components that may be adjusted and optimized for compatibility with the particular host cell. For example, the vector components may include, but are not limited to, an origin of replication, a selection marker gene, a promoter, a ribosome binding site, a signal sequence, the nucleic acid sequence encoding protein of interest, and a transcription termination sequence.

[0110] In one example, vectors of the invention include: a vector comprising a weak promoter for a selection gene (e.g., 3-ketosteroid reductase and glutamine synthetase) and a strong promoter for the gene encoding the protein of interest (e.g., an antibody, e.g., heavy and light chain of an antibody). Vectors can be linearized or supercoiled exhibiting improved transfection efficiency. In some embodiments, codon optimization of the vector is employed to minimize the use of rare codons in the coding sequence and improve protein production yields. Exemplary vectors of the invention are described in Wurm (2004) Nature Biotechnology, Vol 22; Issue 11: 1393-1398).

[0111] In some embodiments, mammalian cells are used as host cells for the invention. The glutamine-auxotrophic and cholesterol-auxotrophic phenotype can be induced by genetic manipulation of a non-glutamine-auxotrophic and non-cholesterol-auxotrophic cell, including for example mutation or deletion of a gene necessary for endogenous glutamine biosynthesis, such as glutamine synthetase. Common methods of genetic engineering are well known to those of skill in the art, e.g., site directed mutagenesis, zinc finger nucleases, shRNA, transposons, See e.g., Cytotechnology. 2007 April; 53(1-3): 65-73. The murine myeloma cells termed NS0 are known glutamine-auxotrophic and cholesterol-auxotrophic cells (See e.g., Barnes et al. Cytotechnology. 2000. Advances in animal cell recombinant protein production: GS-NS0 expression system February; 32(2):109-23; and US 20100028940).

[0112] Additional examples of mammalian cell types which may be manipulated to be used as host cells include, but are not limited to, human embryonic kidney (HEK) (e.g., HEK293, HEK 293F), Chinese hamster ovary (CHO), HeLa, COS, PC3, Vero, MC3T3, NS0, VERY, BHK, MDCK, W138, BT483, Hs578T, HTB2, BT20, T47D), CRL7030, and HsS78Bst cells. In other embodiments, E. coli cells are used as host cells for the invention. Examples of E. coli strains include, but are not limited to, E. coli 294 (ATCC.RTM. 31,446), E. coli .lamda., 1776 (ATCC.RTM. 31,537, E. coli BL21 (DE3) (ATCC.RTM. BAA-1025), and E. coli RV308 (ATCC.RTM. 31,608). Different host cells have characteristic and specific mechanisms for the posttranslational processing and modification of protein products. Appropriate cell lines or host systems may be chosen to ensure the correct modification and processing of the therapeutic protein expressed. The above-described expression vectors may be introduced into appropriate host cells using conventional techniques in the art, e.g., transformation, transfection, electroporation, calcium phosphate precipitation, and direct microinjection. Once the vectors are introduced into host cells for protein production, host cells are cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences. Methods for expression of therapeutic proteins are known in the art, see, for example, Paulina Balbas, Argelia Lorence (eds.) Recombinant Gene Expression: Reviews and Protocols (Methods in Molecular Biology), Humana Press; 2nd ed. 2004 (Jul. 20, 2004) and Vladimir Voynov and Justin A. Caravella (eds.) Therapeutic Proteins: Methods and Protocols (Methods in Molecular Biology) Humana Press; 2nd ed. 2012 (Jun. 28, 2012).

[0113] Protein Production, Recovery, and Purification

[0114] Host cells used to produce a therapeutic protein of the invention may be grown in media known in the art and suitable for culturing of the selected host cells. Examples of suitable media for mammalian host cells include Minimal Essential Medium (MEM), Dulbecco's Modified Eagle's Medium (DMEM), Expi293.TM. Expression Medium, DMEM with supplemented fetal bovine serum (FBS), and RPMI-1640. Examples of suitable media for bacterial host cells include Luria broth (LB) plus necessary supplements, such as a selection agent, e.g., ampicillin. Host cells are cultured at suitable temperatures, such as from about 20.degree. C. to about 39.degree. C., e.g., from 25.degree. C. to about 37.degree. C., preferably 37.degree. C., and CO.sub.2 levels, such as 5 to 10% (preferably 8%). The pH of the medium is generally from about 6.8 to 7.4, e.g., 7.0, depending mainly on the host organism. If an inducible promoter is used in the expression vector of the invention, protein expression is induced under conditions suitable for the activation of the promoter. Conventional cell culture conditions for production of a therapeutic protein are known in the art, e.g., see Butler, Cell Culture and Upstream Processing, Taylor & Francis; 1st edition (May 25, 2007).

[0115] Protein recovery typically involves disrupting the host cell, generally by such means as osmotic shock, sonication, or lysis. Once the cells are disrupted, cell debris may be removed by centrifugation or filtration. The proteins may be further purified. An antibody of the invention may be purified by any method known in the art of protein purification, for example, by protein A affinity, other chromatography (e.g., ion exchange, affinity, and size-exclusion column chromatography), centrifugation, differential solubility, or by any other standard technique for the purification of proteins. (see Process Scale Purification of Antibodies, Uwe Gottschalk (ed.) John Wiley & Sons, Inc., 2009). In some instances, a therapeutic protein can be conjugated to marker sequences, such as a peptide to facilitate purification. An example of a marker amino acid sequence is a hexa-histidine peptide (His-tag), which binds to nickel-functionalized agarose affinity column with micromolar affinity. Other peptide tags useful for purification include, but are not limited to, the hemagglutinin "HA" tag, which corresponds to an epitope derived from the influenza hemagglutinin protein.

Pharmaceutical Compositions and Preparations

[0116] The invention features pharmaceutical compositions that include one or more therapeutic protein described herein. In addition to a therapeutically effective amount of the therapeutic protein, the pharmaceutical compositions may contain one or more pharmaceutically acceptable carriers or excipients, which can be formulated by methods known to those skilled in the art.

[0117] Acceptable carriers and excipients in the pharmaceutical compositions are nontoxic to recipients at the dosages and concentrations employed. Acceptable carriers and excipients may include buffers, antioxidants, preservatives, polymers, amino acids, and carbohydrates. Pharmaceutical compositions of the invention can be administered parenterally in the form of an injectable formulation. Pharmaceutical compositions for injection (i.e., intravenous injection) can be formulated using a sterile solution or any pharmaceutically acceptable liquid as a vehicle. Pharmaceutically acceptable vehicles include, but are not limited to, sterile water, physiological saline, and cell culture media (e.g., Dulbecco's Modified Eagle Medium (DMEM), .alpha.-Modified Eagles Medium (.alpha.-MEM), F-12 medium). Formulation methods are known in the art, see e.g., Banga (ed.) Therapeutic Peptides and Proteins: Formulation, Processing and Delivery Systems (2nd ed.) Taylor & Francis Group, CRC Press (2006).

[0118] The pharmaceutical composition may be formed in a unit dose form as needed. The amount of active component, e.g., one or more therapeutic protein of the invention included in the pharmaceutical preparations is such that a suitable dose within the designated range is provided (e.g., a dose within the range of 0.01-500 mg/kg of body weight).

Therapeutic Proteins

[0119] Therapeutic proteins which may be made by the methods described herein include any recombinant therapeutic protein of interest or biosimilar thereof, including but limited to, antibodies (e.g., monoclonal antibodies, bispecific antibodies, multispecific antibodies), fusion proteins (e.g., Fc fusion), anticoagulants, blood factors, bone morphogenetic proteins, engineered protein scaffolds, enzymes, growth factors, hormones, hormone releasing factors, interferons, interleukins, and thrombolytics. Therapeutic proteins include both glycosylated (e.g., proteins having at least one oligosaccharide chain) and non-glycosylated proteins.

[0120] Exemplary monoclonal antibodies include, but are not limited to adalimumab, infiliximab, palivizumab, cetuximab, natalizumab, eculizumab, ustekinumab, golimumab, ofatumab, canakinumab, belimumab, alirocumab, mepolizumab, necitumumab, nivolumab, dinutuximab, secukinumab, evolocumab, blinatumomab, pembrolizumab, ramucirumab, vedolizumab, siltuximab, obinutuzumab, trastuzumab, raxibacumab, pertuzumab, brentuximab, ipilimumab, denosumab, tocilizumab, ofatumumab, canakinumab, certolizumab, catumaxomab, ranibizumab, panitumumab, bevacizumab, cetuximab, efalizumab, omalizumab, tositumomab, ibritumomab, alemtuzumab, gemtuzumab, basiliximab, daclizumab, rituximab, and abciximab.

[0121] Exemplary fusion proteins include, but are not limited to alefacept, entanercept, abatacept, belatacept, aflibercept, ziv-aflibercept, rilonacept, romiplostim, apocept, trebananib, blisibimod, and dulaglutide.

OTHER EMBODIMENTS

[0122] This invention is further illustrated by the following examples that should not be construed as limiting. The contents of all references, patents and published patent applications cited throughout this application are incorporated herein by reference.

EXAMPLES

Example 1. Manufacture of Therapeutic Antibodies Utilizing a Double Auxotrophic Cell

[0123] The following Example describes methods of manufacturing therapeutic proteins, such as antibodies, comprising expression of the therapeutic protein of interest in a cholesterol-auxotrophic and glutamine-auxotrophic cell. The method desirably allows for increased amplification and copy number of the gene of interest, and production in the absence of cholesterol, which is highly insoluble in aqueous solutions and very challenging to work with. The exemplary method is further outlined in FIG. 1.

[0124] Glutamine-auxotrophic and cholesterol-auxotrophic cells, such as NS0 cells, are transfected with a first vector comprising a nucleic acid encoding a 3-ketosteroid reductase (3-KSR). During and post this first transfection, the cells are maintained in cholesterol-free culture media to select for cells which express the first vector, thereby producing a 3-KSR expressing glutamine-auxotrophic culture of cells. These cells are simultaneously or subsequently transfected with a second vector comprising a nucleic acid encoding a glutamine synthetase (GS) and the protein of interest, e.g., the heavy and light chain of a therapeutic antibody. During and post this second transfection, the cells are maintained in glutamine-free cell culture media to select for cells which express the second vector. To further select for cells which have incorporated multiple copies of the second vector, the cell culture media during and/or after the second transfection is supplemented with a glutamine synthetase inhibitor such as methionine sulfoximine (MSX). The final 3-KSR-GS antibody producing cells can be maintained in a cholesterol-free medium, avoiding cholesterol associated manufacturing problems, and display a high level of productivity derived from the MSX selection.

Example 2: Cell Viability Assay

[0125] The following example describes a trypan blue assay to determine cell viability as a proxy for cells that exhibit adequate survival and growth.

[0126] Prepare a 0.4% solution of trypan blue in buffered isotonic salt solution, pH 7.2 to 7.3 (i.e., phosphate-buffered saline). Add 0.1 mL of trypan blue stock solution to 1 mL of cells. Load a hemocytometer and examine immediately under a microscope at low magnification. Count the number of blue staining cells and the number of total cells. Cell viability is calculated as the number of viable cells divided by the total number of cells within the grids on the hemocytometer. If cells take up trypan blue, they are considered non-viable. Cell viability is at least 90% for healthy log-phase cultures.

% viable cells=[1.00-(Number of blue cells/Number of total cells)].times.100

The cell density of the cell line suspension can be determined using a hemocytometer. To calculate the number of viable cells per mL of culture, the following formula is used, correcting for the dilution factor: Number of viable cells.times.10E4.times.1.1=cells/mL culture.

Example 3. Manufacture of Therapeutic Antibodies Utilizing a Triple Selection Method

[0127] The following Example describes methods of manufacturing therapeutic proteins, such as antibodies, comprising expression of the therapeutic protein of interest in a cholesterol- and glutamine-auxotrophic cell with an additional third selection mechanism, e.g., neomycin resistance gene (e.g., using G418 for selection). The method desirably allows for increased amplification and copy number of the gene of interest, and production in the absence of cholesterol, which is highly insoluble in aqueous solutions and very challenging to work with, while overcoming the unexpected manufacturing challenges associated with the 3-KSR cell culture selection system, including for example low productivity.

[0128] NS0 cell selection was first optimized using both a single neomycin selection (FIG. 9) and a single GS selection (FIG. 10). For neomycin optimization, cells were transfected according to standard practice with a nucleic acid vector encoding a neomycin resistance gene. Neomycin was then added to the cell culture media at either (100 .mu.g/ml or 200 .mu.g/ml) for selection. Cell viability was measured at the denoted days post recovery. For GS based selection, cells were transfected with a nucleic acid vector encoding GS and maintained in glutamine-fee cell culture media. Cell viability was measured at the denoted days post recovery. A 3-KSR based triple selection method was optimized using neomycin, 3-KSR, and GS selection to overcome the unexpectedly low productivity associated with 3-KSR selection (FIG. 8). Cells were transfected according to standard practice with one or more nucleic acid vector encoding 3-KSR, GS, and neomycin resistance gene. For selection, cells were maintained in the absence of glutamine and cholesterol and in the presence of neomycin. As shown in FIG. 11, the triple selection maintained ample cell viability post recovery.

Sequence CWU 1

1

71341PRTHomo sapiens 1Met Arg Lys Val Val Leu Ile Thr Gly Ala Ser Ser Gly Ile Gly Leu1 5 10 15Ala Leu Cys Lys Arg Leu Leu Ala Glu Asp Asp Glu Leu His Leu Cys 20 25 30Leu Ala Cys Arg Asn Met Ser Lys Ala Glu Ala Val Cys Ala Ala Leu 35 40 45Leu Ala Ser His Pro Thr Ala Glu Val Thr Ile Val Gln Val Asp Val 50 55 60Ser Asn Leu Gln Ser Val Phe Arg Ala Ser Lys Glu Leu Lys Gln Arg65 70 75 80Phe Gln Arg Leu Asp Cys Ile Tyr Leu Asn Ala Gly Ile Met Pro Asn 85 90 95Pro Gln Leu Asn Ile Lys Ala Leu Phe Phe Gly Leu Phe Ser Arg Lys 100 105 110Val Ile His Met Phe Ser Thr Ala Glu Gly Leu Leu Thr Gln Gly Asp 115 120 125Lys Ile Thr Ala Asp Gly Leu Gln Glu Val Phe Glu Thr Asn Val Phe 130 135 140Gly His Phe Ile Leu Ile Arg Glu Leu Glu Pro Leu Leu Cys His Ser145 150 155 160Asp Asn Pro Ser Gln Leu Ile Trp Thr Ser Ser Arg Ser Ala Arg Lys 165 170 175Ser Asn Phe Ser Leu Glu Asp Phe Gln His Ser Lys Gly Lys Glu Pro 180 185 190Tyr Ser Ser Ser Lys Tyr Ala Thr Asp Leu Leu Ser Val Ala Leu Asn 195 200 205Arg Asn Phe Asn Gln Gln Gly Leu Tyr Ser Asn Val Ala Cys Pro Gly 210 215 220Thr Ala Leu Thr Asn Leu Thr Tyr Gly Ile Leu Pro Pro Phe Ile Trp225 230 235 240Thr Leu Leu Met Pro Ala Ile Leu Leu Leu Arg Phe Phe Ala Asn Ala 245 250 255Phe Thr Leu Thr Pro Tyr Asn Gly Thr Glu Ala Leu Val Trp Leu Phe 260 265 270His Gln Lys Pro Glu Ser Leu Asn Pro Leu Ile Lys Tyr Leu Ser Ala 275 280 285Thr Thr Gly Phe Gly Arg Asn Tyr Ile Met Thr Gln Lys Met Asp Leu 290 295 300Asp Glu Asp Thr Ala Glu Lys Phe Tyr Gln Lys Leu Leu Glu Leu Glu305 310 315 320Lys His Ile Arg Val Thr Ile Gln Lys Thr Asp Asn Gln Ala Arg Leu 325 330 335Ser Gly Ser Cys Leu 34021537DNAHomo sapiens 2gtactctgat tggtgacggg tgaggcggcc cgaaatcgta ggacttccga aagcagcggc 60ggcgtttgct tcactgcttg gaagtgtgag tgcgcgaaga tgcgaaaggt ggttttgatc 120accggggcta gcagtggcat tggcctggcc ctctgcaagc ggctgctggc ggaagatgat 180gagcttcatc tgtgtttggc gtgcaggaac atgagcaagg cagaagctgt ctgtgctgct 240ctgctggcct ctcaccccac tgctgaggtc accattgtcc aggtggatgt cagcaacctg 300cagtcggtct tccgggcctc caaggaactt aagcaaaggt ttcagagatt agactgtata 360tatctaaatg ctgggatcat gcctaatcca caactaaata tcaaagcact tttctttggc 420ctcttttcaa gaaaagtgat tcatatgttc tccacagctg aaggcctgct gacccagggt 480gataagatca ctgctgatgg acttcaggag gtgtttgaga ccaatgtctt tggccatttt 540atcctgattc gggaactgga gcctctcctc tgtcacagtg acaatccatc tcagctcatc 600tggacatcat ctcgcagtgc aaggaaatct aatttcagcc tcgaggactt ccagcacagc 660aaaggcaagg aaccctacag ctcttccaaa tatgccactg accttttgag tgtggctttg 720aacaggaact tcaaccagca gggtctctat tccaatgtgg cctgtccagg tacagcattg 780accaatttga catatggaat tctgcctccg tttatatgga cgctgttgat gccggcaata 840ttgctacttc gcttttttgc aaatgcattc actttgacac catataatgg aacagaagct 900ctggtatggc ttttccacca aaagcctgaa tctctcaatc ctctgatcaa atatctgagt 960gccaccactg gctttggaag aaattacatt atgacccaga agatggacct agatgaagac 1020actgctgaaa aattttatca aaagttactg gaactggaaa agcacattag ggtcactatt 1080caaaaaacag ataatcaggc caggctcagt ggctcatgcc tataattcca gcactttggg 1140aggccaaggc agaaggatca cttgagacca ggagttcaag accagcctga gaaacatagt 1200gagcccttgt ctctacaaaa agaaataaaa ataatagctg ggtgtggtgg catgcgcatg 1260tagtcccagc tactcagaag gatgaggtgg gaggatctct tgaggctggg aggcagaggt 1320tgcagtgagc tgagattgtg ccactgcact ccagcctggg tgacagcgag accctgtctc 1380aaaatatgta tatatttaat atatatataa aaccagagct gacaatgaca ctctggaaca 1440ttgcatacct tctgtacatt ctggggtaca tggatttcta ctgagttgga taatatgcat 1500ttgtaataaa ctatgaacta tgaaaaaaaa aaaaaaa 15373373PRTHomo sapiens 3Met Thr Thr Ser Ala Ser Ser His Leu Asn Lys Gly Ile Lys Gln Val1 5 10 15Tyr Met Ser Leu Pro Gln Gly Glu Lys Val Gln Ala Met Tyr Ile Trp 20 25 30Ile Asp Gly Thr Gly Glu Gly Leu Arg Cys Lys Thr Arg Thr Leu Asp 35 40 45Ser Glu Pro Lys Cys Val Glu Glu Leu Pro Glu Trp Asn Phe Asp Gly 50 55 60Ser Ser Thr Leu Gln Ser Glu Gly Ser Asn Ser Asp Met Tyr Leu Val65 70 75 80Pro Ala Ala Met Phe Arg Asp Pro Phe Arg Lys Asp Pro Asn Lys Leu 85 90 95Val Leu Cys Glu Val Phe Lys Tyr Asn Arg Arg Pro Ala Glu Thr Asn 100 105 110Leu Arg His Thr Cys Lys Arg Ile Met Asp Met Val Ser Asn Gln His 115 120 125Pro Trp Phe Gly Met Glu Gln Glu Tyr Thr Leu Met Gly Thr Asp Gly 130 135 140His Pro Phe Gly Trp Pro Ser Asn Gly Phe Pro Gly Pro Gln Gly Pro145 150 155 160Tyr Tyr Cys Gly Val Gly Ala Asp Arg Ala Tyr Gly Arg Asp Ile Val 165 170 175Glu Ala His Tyr Arg Ala Cys Leu Tyr Ala Gly Val Lys Ile Ala Gly 180 185 190Thr Asn Ala Glu Val Met Pro Ala Gln Trp Glu Phe Gln Ile Gly Pro 195 200 205Cys Glu Gly Ile Ser Met Gly Asp His Leu Trp Val Ala Arg Phe Ile 210 215 220Leu His Arg Val Cys Glu Asp Phe Gly Val Ile Ala Thr Phe Asp Pro225 230 235 240Lys Pro Ile Pro Gly Asn Trp Asn Gly Ala Gly Cys His Thr Asn Phe 245 250 255Ser Thr Lys Ala Met Arg Glu Glu Asn Gly Leu Lys Tyr Ile Glu Glu 260 265 270Ala Ile Glu Lys Leu Ser Lys Arg His Gln Tyr His Ile Arg Ala Tyr 275 280 285Asp Pro Lys Gly Gly Leu Asp Asn Ala Arg Arg Leu Thr Gly Phe His 290 295 300Glu Thr Ser Asn Ile Asn Asp Phe Ser Ala Gly Val Ala Asn Arg Ser305 310 315 320Ala Ser Ile Arg Ile Pro Arg Thr Val Gly Gln Glu Lys Lys Gly Tyr 325 330 335Phe Glu Asp Arg Arg Pro Ser Ala Asn Cys Asp Pro Phe Ser Val Thr 340 345 350Glu Ala Leu Ile Arg Thr Cys Leu Leu Asn Glu Thr Gly Asp Glu Pro 355 360 365Phe Gln Tyr Lys Asn 37048337DNAHomo sapiens 4gtaaaactat tccccgtgaa ggcggcaggg cagaggtcca gggcgggctt tgctgggagc 60ctcgggaccc cgggttgggg gccgtggggc ggcacctggc gagctggcgg gtgggcggcg 120agccgaggct tcccggcctg gcggcaactc gcccctctgc cctcagccct cccggctccg 180ctcccttccc ccacgccgcc ctgcccctcc cccacgcccc tttctctttc tttctttctt 240tcccagttcg cttgccccca ccccagcggc gcccgccggg ctcctcgccc aatggccgcg 300gggcccggga ccgcatcagc tgatcggccc gggctcctgg ccgctgggag ccaatcaggg 360caccgggggc ggccccgggc cgcggataaa gggtgcgggg ctgctggcgg ctctgcagag 420tcgagagtgg gagaagagcg gagcgtgtga gcagtactgc ggcctcctct cctctcctaa 480cctcgctctc gcggcctagc tttacccgcc cgcctgctcg gcgaccagcg gggatcctcc 540cccagccgca agtccacgaa gaaagcaacg aatgaaaatt atgaagacaa cgagaagtca 600gactcctccg ggtcgcgctc cagctgcttc ggcttcgtcg cctactctgt gaactccggg 660gagagatctc gagtcaagat taagacctta acccaccaac ctgcctgttc ggacaccccc 720cgggccggcc gctgtctgtc cccttctcca tcgccctctc ccagaaagct ccggtgcttg 780gaccagctag agtctgagaa agaggagagg cgcgaacgcc actccaaaaa gagaagggtt 840aaagagggca accctaacga tacgcttgac tttctgtggc tgggaacacc ttccaccatg 900accacctcag caagttccca cttaaataaa ggcatcaagc aggtgtacat gtccctgcct 960cagggtgaga aagtccaggc catgtatatc tggatcgatg gtactggaga aggactgcgc 1020tgcaagaccc ggaccctgga cagtgagccc aagtgtgtgg aagagttgcc tgagtggaat 1080ttcgatggct ctagtacttt acagtctgag ggttccaaca gtgacatgta tctcgtgcct 1140gctgccatgt ttcgggaccc cttccgtaag gaccctaaca agctggtgtt atgtgaagtt 1200ttcaagtaca atcgaaggcc tgcagagacc aatttgaggc acacctgtaa acggataatg 1260gacatggtga gcaaccagca cccctggttt ggcatggagc aggagtatac cctcatgggg 1320acagatgggc acccctttgg ttggccttcc aacggcttcc cagggcccca gggtccatat 1380tactgtggtg tgggagcaga cagagcctat ggcagggaca tcgtggaggc ccattaccgg 1440gcctgcttgt atgctggagt caagattgcg gggactaatg ccgaggtcat gcctgcccag 1500tgggaatttc agattggacc ttgtgaagga atcagcatgg gagatcatct ctgggtggcc 1560cgtttcatct tgcatcgtgt gtgtgaagac tttggagtga tagcaacctt tgatcctaag 1620cccattcctg ggaactggaa tggtgcaggc tgccatacca acttcagcac caaggccatg 1680cgggaggaga atggtctgaa gtacatcgag gaggccattg agaaactaag caagcggcac 1740cagtaccaca tccgtgccta tgatcccaag ggaggcctgg acaatgcccg acgtctaact 1800ggattccatg aaacctccaa catcaacgac ttttctgctg gtgtagccaa tcgtagcgcc 1860agcatacgca ttccccggac tgttggccag gagaagaagg gttactttga agatcgtcgc 1920ccctctgcca actgcgaccc cttttcggtg acagaagccc tcatccgcac gtgtcttctc 1980aatgaaaccg gcgatgagcc cttccagtac aaaaattaag tggactagac ctccagctgt 2040tgagcccctc ctagttcttc atcccactcc aactcttccc cctctcccag ttgtcccgat 2100tgtaactcaa agggtggaat atcaaggtcg tttttttcat tccatgtgcc cagttaatct 2160tgctttcttt gtttggctgg gatagagggg tcaagttatt aatttcttca cacctaccct 2220cctttttttc cctatcactg aagcttttta gtgcattagt ggggaggagg gtggggagac 2280ataaccactg cttccattta atggggtgca cctgtccaat aggcgtagct atccggacag 2340agcacgtttg cagaaggggg tctcttcttc caggtagctg aaaggggaag acctgacgta 2400ctctggttag gttaggactt gccctcgtgg tggaaacttt tcttaaaaag ttataaccaa 2460cttttctatt aaaagtggga attaggagag aaggtagggg ttgggaatca gagagaatgg 2520ctttggtctc ttgcttgtgg gactagcctg gcttgggact aaatgccctg ctctgaacac 2580gaagcttagt ataaactgat ggatatccct accttgaaag aagaaaaggt tcttactgct 2640tggtccttga tttatcacac aaagcagaat agtattttta tatttaaatg taaagacaaa 2700aaactatatg tatggttttg tggattatgt gtgttttgct aaaggaaaaa accatccagg 2760tcacggggca ccaaatttga gacaaatagt cggattagaa ataaagcatc tcattttgag 2820tagagagcaa gggaagtggt tcttagatgg tgatctggga ttaggccctc aagacccttt 2880tgggtttctg ccctgcccac cctctggaga aggtgggcac tggattagtt aacagacaac 2940acgttactag cagtcacttg atctccgtgg ctttggttta aaagacacac ttgtccacat 3000aggtttagag ataagagttg gctggtcaac ttgagcatgt tactgacaga gggggtattg 3060gggttatttt ctggtaggaa tagcatgtca ctaaagcagg ccttttgata ttaaattttt 3120taaaaagcaa aattatagaa gtttagattt taatcaaatt tgtagggttt ctaggtaatt 3180tttacagaat tgcttgtttg cttcaactgt ctcctacctc tgctcttgga ggagatgggg 3240acagggctgg agtcaaaaca cttgtaattt tgtatcttga tgtctttgtt aagactgctg 3300aagaattatt ttttttcttt tataataagg aataaacccc acctttattc cttcatttca 3360tctaccattt tctggttctt gtgttggctg tggcaggcca gctgtggttt tcttttgcca 3420tgacaacttc taattgccat gtacagtatg ttcaaagtca aataactcct cattgtaaac 3480aaactgtgta actgcccaaa gcagcactta taaatcagcc taacataaga tctctctgat 3540gtgtttgtga ttctttcaaa tccctatgtg ccattatatt tctttatttc ctaaaacagg 3600caaaataagc tcaagtttat gtactctgag tttttaaaac actggagtga tgttgctgac 3660cagccgtttc ctgtacctct ctaagttggg tatttgggac ttaagggatt aagtttttca 3720cctagactta gttacacaca atcttggcat ttcctagcct agaggtttgt agcagggtac 3780aagccccact cctccccctt cctttgctcc cctgagtttg gttttggctt accataacat 3840tgttttgacc attcctagcc taatacaata gcctaacata atgtaagatt aactggcttt 3900acgatttcta ttctctgctc tcagtgataa gaaacaaata ttagctaccc tgctaccctg 3960gttgaagcct tccaaggctg gctatgccct aggcatgggc tcatccttgg gtgtatcttg 4020ccttgcagga agaccagtgg accgattgtg attctcaaaa gctctgtgtt gtcacctgtg 4080cccttgcccc ttgctcttat cttggtccgt gtatctggga gttcttccac cttatcttgg 4140ccaattccta ccttcgttca ttcctcatga ggttgggtaa aagctccctc cggctcccat 4200gatgctgtgc atatacctag caaaaagcaa ttattggaca cattggagtg caatattatt 4260aatagcatta atactactaa taatgtgggc aatagtgatt gtttttaaaa ggcagtatac 4320tcttaccagt gcgaggtagc tggggcctgt gatagttttt agagataagt tcttcaggca 4380actgtgtatt ttacactagt caagtaatcc tagatatccg tggtttttct taagaaagtt 4440ggctcgtaat atgatttaat attcaaagta gagtcatcta cctattagct tgctggcgtg 4500gtcctagttt atgcctgttt cagcatgatt gttgagtacc ctgtttcatc cttagcattt 4560tcttgatttt gttgttaaat gatgtatacc cttatttcca ttgaatctgt gcttccaccc 4620ccccaactga agttgtcttc cctttgcttg gccaccctta cagcctcttg gatggtgtat 4680cctacagtgt aagcactaaa ctgaagaggc agtgacctga gcactttgga ttttgttcat 4740tgtaatcaat tccatgacaa aatgattgca tgagaaggaa ttttaaattc ataggatcag 4800aatttaggtg aaaacaacca gcatatttgt ttcttcaccc tctcacctag aattagcttt 4860gacctacagg tcacagtgca atccccttgt atttctaagg tgttttttat agttcatttg 4920cagacaatgg gttatgtgat aacttttatc agtgatagat taaacagaat aatgaccaag 4980ctttcaacct taaggagtca ggccagtatt tacaaaagga ggtctccatg aactccttaa 5040atatgagttc ccctaatatc atcttgccag gtactaaata acaactgata gcacaagcta 5100tagggaattt gaaagaattc catggatggg tgttgtctag ggccttttgt tgtttttgag 5160acggggtctg actctcaccc aggctggagt atagtgtggc gcaatcttgg ctcactgcaa 5220cttctgcctc ccagattcaa gcgattctcc tgcctcagcc tcccaagtag ctgagactac 5280aggtgtgcac caccatgctc agctaatttt tgtattttta gtacagatgg ggtttcacca 5340tgttggccag gctggtcttg aactcctgat ctcccaaagt gaggtcttga actggtcttg 5400aactcctcca cctcccaaag tgctgggatt acaggcgtga gccactgcac ccggcctagg 5460gccatgtaaa aagccagatc tgtgctgctg tctgtgtaga agggtagaca agtggatgag 5520aagttcctga actattcttg gcccttttac cactaagtga aagtaacttg ctgccccaaa 5580gaaagatgtc tcatcattcg acaggacttt ctagttgaac ttcatgaaag caagagatcc 5640tgtttttctt gctcaccact gtatcttgag acctgttgta gtgcctgcaa tacttattta 5700ataagttatt tttaagtatc agttttgtga gctttaactc tatgaggtct ttgttgtttg 5760actgtatttt aactctggcc atgacagcaa gacaaagttc catttttatt gagcttaaaa 5820agaatcaagg ccaggtgaag tggcttacgc ctgtgatccc aacactttgt gaggctgcag 5880caggaggatc tcttgagccc aggagtttga gaccgttcta ggcaatgtag tgaggtccag 5940actccacaaa ataatttttt tttaaattgc acgcctgtag tctcagctat caggaggctg 6000agatgggagg atgacttgag cccaggaaat tgaagctgca gtgaattgtg attgcaccac 6060tgcactccag cctgggtgac agatcaagac cttgcctaaa caaaacaaaa caaacaaaac 6120cccaaaaaac aaattgaaaa tgttgattct ttttactaca aacattatgg cagcactaaa 6180aacttcgtgg gagtgtactg tggaaaatag tgtacttaat taattctcat tgtaatcagg 6240ctaccaagag ccttgtgttg ctttaagagt tataactgcc aggcacagtg gctcatgcct 6300ataatcccag caccttgaga ggccgaggca ggtggatcac ctgagatcgg gagtttgaga 6360ccagccgggc caatatggtg aaacaagctg tgtctctact aaatacaaaa aattagccgg 6420gcgtggtggc acatgcctgt aatcccagct gcttgggaga ctgagacagg agaattgctt 6480gaacctggaa ggcggaggtt gcagtgagct gagattgcaa cattgtactc cagcctgggc 6540aacaagaggg aaactccatc tcaaaaaaaa aaaaaaagtt gtaactgagg ctgggcatgg 6600tggctcatac ctgtaatccc agcactttga aaagccgagg caggtagatc acttgagctc 6660agaagttcga gactagcctg ggcaacatga caaaacccca tctctacaaa aaatacgaaa 6720aattagctgg gcgtggtggc atgcacctgt agtcctagct acctgggagg ctgaggtggg 6780aagattactt gaagctgcag tgagccatgg ttgtgccact gccctccagt ctgggcaaca 6840aagtgagacc ctgtctcaaa aaaacaaaaa aaaattataa ctgatgtaaa ctggcagttt 6900aggctgggtg tggtggctca agcctgtaat cctagcactt tgggaggcca aggcaggtgg 6960atcacctgag ttcaggagtt cgagaccagc gtggccaaca tggtgaaacc ttgtctctat 7020taaaaatacc aaaattagca agatgtggtg gtgggtgcct ataattccag ctactcagga 7080ggctgaggca ggaggatcgc tggagccagg gaggcagagg ttacagtaag caaagatcac 7140tccacttcac tccagcctgg gcaaaagagt gagacatatc aaaaaataaa caaataaata 7200aataaataag tggcagttca tcatttaact ccaaagactt tgcgtacatt tctactgaaa 7260acaatctgag ctgattagaa ccctgccatt ttatagcctt tagctcgatc tccgaccgtt 7320catttaaaaa aattctactt caggccgggc atggtggctc aagcctgtaa tcccatcact 7380gtaggaggcc aaagtgggca gatcacttaa ggtcaggagt ttgagaccag cctggccacc 7440atggtgaaac cccatctcta ctaaaaatac aaaaattagc cgggcttggt ggtgagcacc 7500tgtaatccca ccctgccgag tggcaggctg aggcaggaga atcgcttgag cccaagagcc 7560ggaggttgca gtgagccaag cttgcaccat tgcactccag cctaggcaac agagtgtgac 7620tccatctcaa gaaaaaaaaa attctatttc attttacaat atgcagatat atgtccatac 7680acatgcataa tataaatgta taccatattt gtgagaatat gcatatatgt acacattaga 7740tacacaatac aagcacaata catatgtctt ttgcccaaga tacagcattt tgtaaaggag 7800acaggaattt agtaatatat gttccagaaa cagtacacaa gagaattcgc cgagatgaga 7860aagttgtcac taggaatggg gagtggtaag atgtagaagg tataattgtt cttaaagttc 7920tactgccaac tctttccaat taattaccca ctctgccatg ctttatggac aggaggttgt 7980cggacactgt caattaataa atatttgagc atgatacact gcttggagct cctctaatat 8040aggagagtga tatcctagtg catgttacag agggagtgtc cacacagttc ctattgtcat 8100ttgatgagtt acttttcagg ggccttgtac ctgagcaagt tgtcctcttt ttgatggatt 8160tcagattgag ttacctgcat tgtcttgaga ttgcagcgtg tttcctccac tgtacggcgt 8220agtcagcaga tctattagtt aaactccagt gggccctcag tcactaaatc tatcctctgt 8280gttgaaggct ttctgcattt gcctttcaat aaaggtttag aataactcct taaaaaa 83375187PRTHomo sapiens 5Met Val Gly Ser Leu Asn Cys Ile Val Ala Val Ser Gln Asn Met Gly1 5 10 15Ile Gly Lys Asn Gly Asp Leu Pro Trp Pro Pro Leu Arg Asn Glu Phe 20 25 30Arg Tyr Phe Gln Arg Met Thr Thr Thr Ser Ser Val Glu Gly Lys Gln 35 40 45Asn Leu Val Ile Met Gly Lys Lys Thr Trp Phe Ser Ile Pro Glu Lys 50 55 60Asn Arg Pro Leu Lys Gly Arg Ile Asn Leu Val Leu Ser Arg Glu Leu65 70 75 80Lys Glu Pro Pro Gln Gly Ala His Phe Leu Ser Arg Ser Leu Asp Asp 85 90 95Ala Leu Lys Leu Thr Glu Gln Pro Glu Leu Ala Asn Lys Val Asp Met 100 105 110Val Trp Ile Val Gly Gly Ser Ser Val Tyr Lys Glu Ala Met Asn His

115 120 125Pro Gly His Leu Lys Leu Phe Val Thr Arg Ile Met Gln Asp Phe Glu 130 135 140Ser Asp Thr Phe Phe Pro Glu Ile Asp Leu Glu Lys Tyr Lys Leu Leu145 150 155 160Pro Glu Tyr Pro Gly Val Leu Ser Asp Val Gln Glu Glu Lys Gly Ile 165 170 175Lys Tyr Lys Phe Glu Val Tyr Glu Lys Asn Asp 180 18563932DNAHomo sapiens 6tcccagacag aacctactat gtgcggcggc agctggggcg ggaaggcggg agctgggggc 60gctgggggcg ctgcggccgc tgcggccgct gcagccgctg cagcgccagg gtccacctgg 120tcggctgcac ctgtggagga ggaggtggat ttcaggcttc ccgtagactg gaagaatcgg 180ctcaaaaccg cttgcctcgc aggggctgag ctggaggcag cgaggccgcc cgacgcaggc 240ttccggcgag acatggcagg gcaaggatgg cagcccggcg gcagggcctg gcgaggagcg 300cgagcccgcg gccgcagttc ccaggcgtct gcgggcgcga gcacgccgcg accctgcgtg 360cgccggggcg ggggggcggg gcctcgcctg cacaaatggg gacgaggggg gcggggcggc 420cacaatttcg cgccaaactt gaccgcgcgt tctgctgtaa cgagcgggct cggaggtcct 480cccgctgctg tcatggttgg ttcgctaaac tgcatcgtcg ctgtgtccca gaacatgggc 540atcggcaaga acggggacct gccctggcca ccgctcagga atgaattcag atatttccag 600agaatgacca caacctcttc agtagaaggt aaacagaatc tggtgattat gggtaagaag 660acctggttct ccattcctga gaagaatcga cctttaaagg gtagaattaa tttagttctc 720agcagagaac tcaaggaacc tccacaagga gctcattttc tttccagaag tctagatgat 780gccttaaaac ttactgaaca accagaatta gcaaataaag tagacatggt ctggatagtt 840ggtggcagtt ctgtttataa ggaagccatg aatcacccag gccatcttaa actatttgtg 900acaaggatca tgcaagactt tgaaagtgac acgttttttc cagaaattga tttggagaaa 960tataaacttc tgccagaata cccaggtgtt ctctctgatg tccaggagga gaaaggcatt 1020aagtacaaat ttgaagtata tgagaagaat gattaatatg aaggtgtttt ctagtttaag 1080ttgttccccc tccctctgaa aaaagtatgt atttttacat tagaaaaggt tttttgttga 1140ctttagatct ataattattt ctaagcaact agtttttatt ccccactact cttgtctcta 1200tcagatacca tttatgagac attcttgcta taactaagtg cttctccaag accccaactg 1260agtccccagc acctgctaca gtgagctgcc attccacacc catcacatgt ggcactcttg 1320ccagtccttg acattgtcgg gcttttcaca tgttggtaat atttattaaa gatgaagatc 1380cacataccct tcaactgagc agtttcacta gtggaaatac caaaagcttc ctacgtgtat 1440atccagaggt ttgtagataa atgttgccac cttgtttgta acagtgaaaa attgaaaaca 1500acctggaagt ccagtgatgg gaaaatgagt atgtttctgt cttagattgg ggaacccaaa 1560gcagattgca agactgaaat ttcagtgaaa gcagtgtatt tgctaggtca taccagaaat 1620catcaattga ggtacggaga aactgaactg agaaggtaag aaaagcaatt taaagtcagc 1680gagcaggttc tcattgataa caagctccat actgctgaga tacagggaaa tggagggggg 1740aaagctggag tattgatccc gcccccctcc ttggttgtca gctccctgtc ctgtgtgtgg 1800gcggaacata gtccagctgc tctatagcaa gtctcaggtg tttgcagtaa gaagctgctg 1860gcatgcacgg gaacagtgaa tgccaaacac ttaaagcaat tcgatgttta agtatgtaag 1920ttcttttttt tttagacagc gtttcgctct tgttgcccag gctagcatgc aatggtgtga 1980cctcggctta ctgcaacctc cgccttccca gattcaagcg attctcctgc ctcaggctcc 2040caagtagcta ggaccaggtg cgcgccacca cgcccggcta atttttgtat tttgtatttt 2100tagtagagat ggggtttcac catgttggtc aggctagtct cgaactcgtg accgcaagcg 2160attcacccac ctcagcctcc caaagtgctg ggattaccgg cttgagccac cacacccggc 2220acatcttcat tctttttatg tagtaaaaag tataaggcca cacatggttt atttgaagta 2280ttttataatt taaaaaaata cagaagcagg aaaaccaatt ataagttcaa gtgagggatg 2340atggttgctt gaaccaaagg gttgcatgta gtaagaaatt gtgatttaag atatatttta 2400aagttataag tagcaggata ttctgatgga gtttgacttt ggttttgggc ccagggagtt 2460tcagatgcct ttgagaaatg aatgaagtag agagaaaata aaagaaaaac cagccaggca 2520cagtggctca cacctgtaat cccagcgctt tgggaggcta aggcaggcag atcacttgag 2580accagcttgg gcaacatggc aaagccccat ctctacaaaa aacacaaaaa ttagctgggc 2640attgtggcgc acacctgtat tcccatctag tcaggaagct gagatggaag aattaattga 2700gcccacgagt tcaaggctgc agtgagtcgt gattgtgcca ctgcactcca gccggggtga 2760cagaagagac cttgtctcga aaaggaatct gaaaacaatg gaaccatgcc ttcataattc 2820tagaaagtta ttttcaactg ataaatctat attcacccaa ataatcaagg gtgaaggtaa 2880aataatacat ttttagacaa gcaaagactc aggggttacc tccatgtgcc ctttttaggg 2940aagctgttgg agaaaatact ccagcaaaat gaaggagtac acaaaccaga gaatgacatg 3000aatccagcaa ataggatcca acacaggcaa tattccagct atggagctag ctttaaaaag 3060gaacagtaaa aatattaatc ggttagctgg gtggaatggc ccatgcctgt agtcccagct 3120actcaggagg ctcagcagca ggacgacttg agcccaagag ttccagacca gcctggccac 3180cttagtgaga tcccttctct taaaaataat aacttattgc cagatttggg gcatttggaa 3240agaagttcat tgaagataaa gcaaaagtaa aaaaaaaaaa aaaaaaaaca aggggaaagg 3300gttggttagg caatcattct agggcagaaa gaagtacagg ataggaagag cataatacac 3360tgtttttctc aacaaggagc agtatgtaca cagtcataat gatgtgactg cttagcccct 3420aaatatggta actactctgg gacaatatgg gaggaaaagt gaagattgtg atggtgtaag 3480agctaaatcc tcatctgtca tatccagaaa tcactatata atatataata atgaaatgac 3540taagttatgt gaggaaaaaa acagaagaca ttgctaaaag agttaaaagt cattgctctg 3600gagaattagg agggatgggg caggggactg ttaggatgca ttataaactg aaaagccttt 3660ttaaaatttt atgtattaat atatgcattc acttgaaaaa ctaaaaaaaa acaataattt 3720ggaaaaaccc atgaaggtaa ctaacggaag gaaaaactaa gagaatgaaa agtatttgcc 3780tctggaaaga acaactggca ggactgttgt tttcattgta agacttttgg agccatttaa 3840ttgtacttaa ccattttcat ctatttcttt aataagaaca attccatctt aataaagagt 3900tacacttgtt aataagtaaa aaaaaaaaaa aa 393276PRTArtificial SequenceDescription of Artificial Sequence Synthetic 6xHis tag 7His His His His His His1 5

Claims

1.-42. (canceled)

43. A method of manufacturing a therapeutic protein, comprising: transfecting a cholesterol-auxotrophic cell with (i) a nucleic acid encoding a protein that restores cholesterol biosynthesis in the cell; (ii) an aminoglycosidic antibiotic resistance gene; and (iii) a nucleic acid encoding the therapeutic protein.

44. The method of claim 43, wherein the protein that restores cholesterol biosynthesis in the cell is a 3-ketosteroid reductase (3-KSR).

45. The method of claim 43, wherein the aminoglycosidic antibiotic resistance gene is selected from the group consisting of: a neomycin resistance gene, a blasticidin resistance gene, a hygromycin resistance gene, a puromycin resistance gene, a zeocin resistance gene, and a mycophenolic acid resistance gene.

46. The method of claim 43, comprising transfecting the cell with a first vector and a second vector, wherein the first vector comprises the nucleic acid encoding the protein that restores cholesterol biosynthesis in the cell and the nucleic acid encoding the therapeutic protein; and the second vector comprises the aminoglycosidic antibiotic resistance gene.

47. The method of claim 43, comprising transfecting the cell with a first vector and a second vector, wherein the first vector comprises the nucleic acid encoding the protein that restores cholesterol biosynthesis in the cell; and the second vector comprises the antibiotic resistance gene and the nucleic acid encoding the therapeutic protein.

48. The method of claim 43, comprising transfecting the cell with a first vector and a second vector, wherein the first vector comprises the nucleic acid encoding the protein that restores cholesterol biosynthesis in the cell and the nucleic acid encoding the therapeutic protein; and the second vector comprises the antibiotic resistance gene and the nucleic acid encoding the therapeutic protein

49. The method of claim 46, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out prior to the transfecting with the second vector, or the transfecting the cell with the first vector is carried out after the transfecting with the second vector.

50. The method of claim 47, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out prior to the transfecting with the second vector, or the transfecting the cell with the first vector is carried out after the transfecting with the second vector.

51. The method of claim 48, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out prior to the transfecting with the second vector, or the transfecting the cell with the first vector is carried out after the transfecting with the second vector.

52. The method of claim 46, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out simultaneously with the transfecting the cell with the second vector.

53. The method of claim 47, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out simultaneously with the transfecting the cell with the second vector.

54. The method of claim 48, wherein the method comprises transfecting the cell with the first vector and the second vector, and wherein the transfecting the cell with the first vector is carried out simultaneously with the transfecting the cell with the second vector.

55. The method of claim 43, further comprising culturing the cell in the presence of a 3-KSR inhibitor after transfecting the cell with (i).

56. The method of claim 43, further comprising culturing the cell in the absence of at exogenously introduced cholesterol after transfecting with (i).

57. The method of claim 43, further comprising culturing the cell n the presence of an aminoglycosidic antibiotic after transfecting the cell with (ii).

58. The method of claim 52, comprising culturing the cell in the absence of an exogenously introduced cholesterol and in the presence of an aminoglycosidic antibiotic after simultaneously transfecting the cell with the first vector and the second vector.

59. The method of claim 53, comprising culturing the cell in the absence of an exogenously introduced cholesterol and in the presence of an aminoglycosidic antibiotic after simultaneously transfecting the cell with the first vector and the second vector.

60. The method of claim 54, comprising culturing the cell in the absence of an exogenously introduced cholesterol and in the presence of an aminoglycosidic antibiotic after simultaneously transfecting the cell with the first vector and the second vector.

61. The method of claim 43, wherein the nucleic acid encoding the therapeutic protein comprises a nucleic acid encoding a heavy chain and a light chain of an antibody.

62. The method of claim 61, wherein the antibody is selected from the group consisting of: adalimumab, infiliximab, palivizumab, cetuximab, natalizumab, eculizumab, ustekinumab, golimumab, ofatumab, canakinumab, belimumab, alirocumab, mepolizumab, necitumumab, nivolumab, dinutuximab, secukinumab, evolocumab, blinatumomab, pembrolizumab, ramucirumab, vedolizumab, siltuximab, obinutuzumab, trastuzumab, raxibacumab, pertuzumab, brentuximab, ipilimumab, denosumab, tocilizumab, ofatumumab, canakinumab, certolizumab, catumaxomab, ranibizumab, panitumumab, bevacizumab, cetuximab, efalizumab, omalizumab, tositumomab, ibritumomab, alemtuzumab, gemtuzumab, basiliximab, daclizumab, rituximab, abciximab, alefacept, entanercept, abatacept, belatacept, aflibercept, ziv-aflibercept, rilonacept, romiplostim, apocept, trebananib, blisibimod, and dulaglutide.

63. The method of claim 43, wherein the therapeutic protein is selected from the group consisting of: an antibody, a fusion protein, an anticoagulant, a blood factor, a bone morphogenic protein, an engineered protein scaffold, an enzyme, a growth factor, a hormone, a hormone releasing factor, an interleukin, or a thrombolytic protein and the method comprises transfecting the cell with a nucleic acid encoding an antibody, a fusion protein, an anticoagulant, a blood factor, a bone morphogenic protein, an engineered protein scaffold, an enzyme, a growth factor, a hormone, a hormone releasing factor, an interferon, an interleukin, and a thrombolytic protein.

64. The method of claim 43, wherein the cell is an NS0 cell.

65. A transformed mammalian host cell, transfected with an aminoglycosidic antibiotic resistance gene, and a nucleic acid encoding a therapeutic protein, wherein the transformed mammalian host cell is derived from a parental mammalian host cell that is cholesterol-auxotrophic.

66. A therapeutic protein produced by a method comprising culturing the transformed mammalian host cell of claim 65, in the presence of an aminoglycosidic antibiotic.