CN115322255B

CN115322255B - An optimized Fc variant and its application

Info

Publication number: CN115322255B
Application number: CN202210442675.6A
Authority: CN
Inventors: 袁越; 顾继杰; 王卓智; 梁忠爽; 梁若冰; 陈智胜
Original assignee: Shanghai Yaoming Biomedical Co ltd; Wuxi Biologics Shanghai Co Ltd
Current assignee: Shanghai Yaoming Biomedical Co ltd; Wuxi Biologics Shanghai Co Ltd
Priority date: 2022-04-25
Filing date: 2022-04-25
Publication date: 2025-03-07
Anticipated expiration: 2042-04-25
Also published as: CN115322255A

Abstract

The present invention discloses an optimized Fc variant and its application, wherein the Fc region variant comprises amino acid mutations at multiple sites compared with the parent Fc, the positions of the mutations are 239th, 330th, 252nd, 254th and 256th, and the amino acid sequence of the Fc region variant is shown in SEQ ID NO: 1. Compared with the parent Fc, the Fc region variant provided by the present invention has enhanced binding to human FcRn and human FcγRⅢa, has stronger ADCC activity and longer in vivo half-life, and has better thermal stability.

Description

Optimized Fc variant and application thereof

Technical Field

The invention relates to the technical field of biological medicine, in particular to an optimized Fc variant and application thereof.

Background

Antibodies are a class of immunoglobulins that specifically bind to an antigen and in most mammals, including humans, consist of two heavy chains and two light chains. Each polypeptide chain contains two distinct regions, the variable and constant regions, respectively. The variable regions have significant sequence diversity between different antibodies and are responsible for binding to specific antigens. The constant region has a low degree of sequence diversity, is responsible for binding some native proteins and inducing some important biochemical events. Humans have five different types of antibodies, including IgA, igD, igE, igG (divided into IgG1, igG2, igG3, and IgG4 subtypes) and IgM. An IgG heavy chain consists of four immunoglobulin (Ig) domains in the order VH-CH1-CH2-CH3 from the N-terminus to the C-terminus, and an IgG light chain consists of two immunoglobulin domains in the order VL-CL from the N-terminus to the C-terminus.

In IgG, the Fc region comprises CH2 and CH3 and an N-terminal hinge region to CH 2. The Fc region interacts with many Fc receptors and ligands, inducing a range of effector functions. The Fc gamma receptor (fcγr) is an important family of Fc receptors that mediate communication between antibodies and immune cells. In humans, the receptor family includes FcgammaRI (CD 64), fcgammaRIa, fcgammaRIb, fcgammaRIc including isoforms, fcgammaRII (CD 32), fcgammaRIIa including isoforms H131 and R131, fcgammaRIIB including FcgammaRIIB-1 and FcgammaRIIB-2, and FcgammaRIIB, and FcgammaRIII (CD 16) including isoforms FcgammaRIIIa including isoforms V158 and F158, and FcgammaRIIIb including isoforms FcgammaRIIIb-NA 1 and FcgammaRIIIb-NA 2.

The formation of Fc/fcγr complexes can recruit immune cells to sites of binding antigen, mediating cytotoxicity and effector functions of phagocytes. Wherein the non-specific cytotoxic cells expressing fcγr recognize antibodies bound on target cells and the cell-mediated response that subsequently causes lysis of the target cells is referred to as antibody-dependent cell-mediated cytotoxicity, i.e. ADCC effect, and wherein the non-specific cytotoxic cells expressing fcγr recognize antibodies bound on target cells and the cell-mediated response that subsequently causes phagocytosis of target cells is referred to as antibody-dependent cell-mediated phagocytosis, i.e. ADCP effect.

The overlapping but separate sites on Fc are the interfaces with complement protein C1 q. The formation of the Fc/C1q complex may mediate Complement Dependent Cytotoxicity (CDC), similar to the Fc/fcγr complex mediating ADCC. The site on Fc between CH2 and CH3 mediates interactions with the neonatal receptor FcRn.

Monoclonal antibodies are used therapeutically in a variety of conditions including cancer, inflammation, and cardiovascular disease, among others. Any subtle improvement in mortality is currently considered successful for anti-cancer therapies, while the anti-tumor efficacy of antibodies is related to ADCC effects, and thus there is a significant need to enhance ADCC effects. Because of the great need to enhance the ability of antibodies to destroy target cells, mutations in Fc have historically resulted in some proteins that can enhance ADCC, ADCP, CDC effects, where DLE mutations (S239D/a 330L/I332E, numbering according to the EU index of Kabat et al) enhance binding to fcγriiia and enhance ADCC effects, but DLE mutations diminish thermostability.

The half-life of an antibody is one of the important parameters describing pharmacokinetic PK, simply the time required for the blood concentration of the antibody drug to drop to half in vivo. IgG binding to FcRn can recycle endocytosed (endocytosed) antibodies from the endosome (endosome) to the blood, a process that results in a serum half-life of the antibodies between 1 and 3 weeks. The frequency of injection of antibodies is related to the half-life, and longer in vivo half-lives may be used with lower injection frequencies or doses. The frequency of injection of antibodies with Fc fusion proteins as a drug is related to the half-life, and longer in vivo half-lives may be used with lower injection frequency or dose. Mutations in Fc have now resulted in some proteins that enhance FcRn binding affinity and half-life in vivo, where YTE mutations (M252Y/S254T/T256E, numbering according to the EU index of Kabat et al) enhance binding to FcRn and increase half-life in vivo, with improved pharmacokinetic properties, but YTE mutations attenuate ADCC effects.

Thus, there is a need in the art for antibodies with enhanced therapeutic properties, including longer in vivo half-life and stronger effector function, while having better thermal stability.

Disclosure of Invention

In order to solve the technical problems, the invention provides an immunoglobulin Fc region variant, which comprises amino acid mutations at a plurality of positions, namely 239, 330, 252, 254 and 256, compared with a parent Fc, wherein the amino acid sequence of the Fc region variant is shown as SEQ ID NO. 1.

Specifically, the amino acid at position 239 is mutated from serine S to glutamic acid E.

Specifically, amino acid 252 is mutated from methionine M to tyrosine Y.

Specifically, amino acid 254 is mutated from serine S to threonine T.

Specifically, amino acid 256 is mutated from threonine T to glutamate E.

Specifically, amino acid 330 is mutated from alanine a to phenylalanine F.

In particular, the immunoglobulin is a human IgG antibody or a monoclonal antibody.

Specifically, the numbering of the positions of the amino acids is according to the EU index of Kabat et al.

Specifically, the ratio of the relative binding activity of the Fc variant to human fcyri receptor and the wild-type immunoglobulin Fc region to human fcyri receptor is 1, the ratio of the relative binding activity of the Fc variant to human fcyriia receptor and the wild-type immunoglobulin Fc region to human fcyriia receptor is 0.2 to 0.3, and the ratio of the relative binding activity of the Fc variant to human fcyriiia receptor and the wild-type immunoglobulin Fc region to human fcyriiia receptor is 10.

Specifically, the ratio of the relative binding activity of the Fc variant to human FcRn receptor binding to the wild-type immunoglobulin Fc region to human FcRn receptor binding in an acidic environment is 10.

The invention also provides a polypeptide comprising an immunoglobulin Fc region variant according to claims 1-10.

In particular, the polypeptide is an IgG antibody or Fc fusion protein.

The invention also provides application of the polypeptide in preparing a medicament for killing abnormal proliferative cells.

In particular, the abnormal proliferative cell is a tumor cell or a tumor tissue-associated cell, which is contained in the patient.

Specifically, the tumor cell is a cancer cell, which is a metastatic cancer cell.

Compared with the prior art, the invention has the beneficial effects that:

1. compared with the prior art, the Fc region variant has longer in vivo half-life, obviously improved pharmacokinetic properties, lower injection frequency or dosage, no need of frequent administration for maintaining blood concentration, solving the technical problem that the half-life of the existing antibody drug is short and the dosage is required to be continuously complemented, saving the drug cost and having practical significance for clinical study and implementation of the drug;

2. The Fc region variant provided by the invention not only has longer half life than the prior art, but also can enhance the ADCC effect, and experimental verification shows that the ADCC effect of the Fc region variant provided by the invention is enhanced by 3-7 times compared with the prior art, so that the anti-tumor effect of the antibody can be obviously improved;

3. Compared with the prior art, the Fc region variant provided by the invention has the advantages that the thermal stability is obviously improved, and the therapeutic property of the antibody is obviously improved, so that the therapeutic efficiency of the medicine is improved, and the Fc region variant has practical significance for clinical treatment of tumors.

Drawings

FIG. 1 is a graph of fit of binding data from SPR assays for Trastuzumab and Trastuzumab Fc variants to human FcγRI (CD 64);

FIG. 2 is a graph of fit of binding data from SPR assays for Trastuzumab and Trastuzumab Fc variants to human FcgammaRIIa (H167);

FIG. 3 is a graph of fit of binding data from SPR assays for Trastuzumab and Trastuzumab Fc variants to human FcgammaRIIIa (F176);

FIG. 4 is a graph of the results of fitting the binding data of Trastuzumab and Trastuzumab Fc variants to human FcRn by SPR determination at pH 6.0;

FIG. 5 is a graph of fit of binding data to human FcRn by SPR assay for Trastuzumab and Trastuzumab Fc variants at pH 7.4;

FIG. 6 is a graph of data for reporter gene assays for antibody dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants;

FIG. 7 is a graph of data for antibody dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants detected by Lactate Dehydrogenase (LDH) release;

FIG. 8 is a graph of data for reporter gene assays for antibody dependent cell-mediated phagocytosis (ADCP) of Trastuzumab and Trastuzumab Fc variants;

FIG. 9 is a dose response curve obtained from ELISA assays for Trastuzumab and Trastuzumab Fc variants binding to C1 q;

Fig. 10 is a graph of the results of Trastuzumab and Trastuzumab Fc variants using DSF testing for thermostability.

In FIG. 9, the X-axis represents the concentration of C1q protein, and the Y-axis represents the absorbance at OD450 nm.

Detailed Description

The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Materials, instruments, reagents and the like used in the following examples are commercially available unless otherwise specified. The technical means used in the examples, unless otherwise specified, are conventional means well known to those skilled in the art.

For all positions discussed herein, numbering is in accordance with the EU index, and those skilled in the antibody arts will appreciate that these conventions include non-contiguous numbering of specific regions of immunoglobulin sequences, thereby enabling standardized references to conserved positions in immunoglobulin families. Thus, the position of any given immunoglobulin defined according to the EU index will not necessarily correspond to its contiguous sequence. The Fc variant experiments performed in the present invention were performed in the context of Trastuzumab, trastuzumab (registered trademark of Herceptin, genentech), an anti-HER 2 antibody for the treatment of metastatic breast cancer, and are not meant to limit the invention to any particular antibody.

Example one Fc receptor binding assay for variants of the Fc region provided by the present invention

As shown in the amino acid sequence table SEQ ID NO. 1, the Fc region variant provided by the invention has the sequence of 216 to 447 mutated and replaced based on EU index, and the mutation sites comprise:

the amino acid at position 239 is mutated from serine S to glutamic acid E;

mutation of amino acid 252 from methionine M to tyrosine Y;

mutation of amino acid 254 from serine S to threonine T;

mutation of amino acid 256 from threonine T to glutamic acid E;

The 330 th amino acid is mutated from alanine A to phenylalanine F.

This example measures Trastuzumab and designated Trastuzumab Fc variants binding to human Fc receptors FcyRI, fcyRIIa, fcyRIIIa and FcRn by surface plasmon resonance SPR.

Surface plasmon resonance is an optical phenomenon that can be used to track interactions between biomolecules in real time in the natural state, and has the characteristics of high sensitivity and high quantification. The method comprises the steps of coupling a biological molecule (target molecule) on the surface of a biological sensor, and injecting a solution containing another biological molecule (analyte) capable of interacting with the target molecule into and flowing through the surface of the biological sensor.

In this example, his-tagged FcyRI (CD 64) or FcgammaRIIa (H167) or FcgammaRIIIa (F176) was immobilized on a CM5 chip and then Trastuzumab WT and Fc variants were flowed through the chip in a range of concentrations when antibody binding to human FcRn was measured, trastuzumab WT and Fc variants were coupled to the CM5 chip surface and then human FcRn was flowed through the chip in a range of concentrations when antibody binding to human FcRn was measured.

Finally, data fitting was performed by 1:1 model and Langmiur analysis (for FcyRI) or by steady state model (for FcyRIIa, fcyRIIIa and FcRn).

Binding data for Trastuzumab and EFYTE variants of Trastuzumab Fc to human FcyRI are shown in the following table:

Binding data for Trastuzumab and EFYTE variants of Trastuzumab Fc to human fcγriia are shown in the following table:

binding data for Trastuzumab and EFYTE variants of Trastuzumab Fc to human fcγriiia are shown in the following table:

binding data for Trastuzumab and EFYTE variants of Trastuzumab Fc in acidic environments to human FcRn are shown in the following table:

Binding data for Trastuzumab and EFYTE variants of Trastuzumab Fc in neutral environments to human FcRn are shown in the following table:

As shown in fig. 1, the EFYTE variants of Trastuzumab and Trastuzumab Fc substantially agree with human FcyRI in affinity, as shown in fig. 2, the EFYTE variant of Trastuzumab Fc has about 3.7-fold lower affinity for human fcyriia than Trastuzumab, as shown in fig. 3, the EFYTE variant of Trastuzumab Fc has about 10-fold higher affinity for human fcyriiia than Trastuzumab, as shown in fig. 4, the EFYTE variant of Trastuzumab Fc has about 10-fold higher affinity for human FcRn than Trastuzumab in acidic environment ph6.0, as shown in fig. 5, and at neutral environment ph7.4, both the EFYTE variants of Trastuzumab and Trastuzumab Fc have little binding to human FcRn.

In conclusion, compared with the parent Fc, the Fc region variant provided by the invention has better affinity to FcRn in an acidic environment and better binding capacity to FcRγRIIIa.

Example two Fc effector function assays

This example performed an antibody-dependent cell-mediated cytotoxicity (ADCC) assay, an antibody-dependent cell-mediated phagocytosis (ADCP), and a complement-dependent cytotoxicity (CDC) assay on Fc variants.

ADCC effector functions of Trastuzumab and its Fc engineered antibodies were detected by the reporter method and EC50 was calculated using GRAPHPAD PRISM software, specifically by stably integrating the CD16-V158 dependent luciferase reporter system in Jurkat cells (ATCC) and acting as effector cells. The target HER2 of the breast cancer cell SK-BR-3 (ATCC) which highly expresses Trastuzumab is used as a target cell, effector cells and target cells are paved into a 96-hole cell culture plate according to a certain proportion, antibodies to be detected are added into the cell plate after being subjected to gradient dilution, and a human IgG1 isotype control is used as a negative control. Luciferase activity was detected using a luciferase reporter assay kit (Promega) after incubation at 37 ℃ for 4-5h and EC50 was calculated using GRAPHPAD PRISM software. The specific data are shown in the following table:

As shown in fig. 6, the graph shows that ADCC effect of EFYTE variants of Trastuzumab Fc was about 7.2-fold enhanced over Trastuzumab and about 1.7-fold reduced over Trastuzumab as calculated from EC 50.

ADCC effects of Trastuzumab and Trastuzumab Fc variants were detected by Lactate Dehydrogenase (LDH) release and EC50 was calculated using GRAPHPAD PRISM software, in this example, by assessing the ADCC effect function of Trastuzumab and its Fc-engineered antibodies by detecting the level of lactate dehydrogenase released after tumor cells were killed by human Peripheral Blood Mononuclear Cells (PBMC) cells. Specifically, commercially available PBMC are used as effector cells, and breast cancer cells SK-BR-3 (ATCC) highly express Trastuzumab as target HER2 cells. Spreading effector cells and target cells into a 96-well cell culture plate according to a certain proportion, carrying out gradient dilution on an antibody to be detected, adding the antibody to be detected into the cell plate, and taking a human IgG1 isotype control as a negative control. Detection was performed with kit Cytotoxicity Detection Kit Plus (LDH) (Roche) after incubation for 4-5h at 37 ℃ and EC50 was calculated using GRAPHPAD PRISM7 software. The data are shown in the following table:

As shown in fig. 7, for the detection of antibody-dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants by Lactate Dehydrogenase (LDH) release, the curve of fig. 7 shows that ADCC effect of EFYTE variants of Trastuzumab Fc was enhanced by about 3.8-fold over Trastuzumab and ADCC effect of YTE variants of Trastuzumab Fc was attenuated by about 5.2-fold over Trastuzumab, calculated as EC 50.

Another important FcyR-mediated effector function is antibody-dependent cell-mediated phagocytosis (ADCP). Phagocytosis of target cells not only can lead to destruction of target cells, but ADCP is associated with an adaptive immune response because phagocytosis is a potential mechanism by which antigen-presenting cells take up and process antigens. Thus, this example also demonstrates the ability of the Fc variants provided by the present invention to mediate ADCP.

As shown in FIG. 8, the ADCP effects of Trastuzumab and Trastuzumab Fc variants were detected by the reporter gene method. In this example, the ADCP effector functions of Trastuzumab and its Fc engineered antibodies were detected by the reporter gene method. The CD 32-dependent luciferase reporter system was stably integrated in Jurkat cells (ATCC) and served as effector cells. The target HER2 of the breast cancer cell SK-BR-3 (ATCC) which highly expresses Trastuzumab is used as a target cell, effector cells and target cells are paved into a 96-hole cell culture plate according to a certain proportion, antibodies to be detected are added into the cell plate after being subjected to gradient dilution, and a human IgG1 isotype control is used as a negative control. After incubation for 4-5h at 37 ℃, luciferase activity was detected using the luciferase reporter assay kit (Promega) and EC50 was calculated using GRAPHPAD PRISM software. The data are shown in the following table:

FIG. 8 shows that dose dependence of ADCP effect on antibody concentration was almost undetectable for the EFYTE variant of Trastuzumab Fc, whereas both YTE variant and DLE variant of Trastuzumab Fc (S239D/I332E/A330L) exhibited weaker ADCP effect than Trastuzumab.

The binding site of complement protein C1q on Fc is close to the FcyR binding site, so careful determination is needed as to whether the Fc variant retains its ability to recruit and activate complement. The specific data are shown in the following table:

Comment	Abs	C1q ELISA EC50(nM)
			Trastuzumab	TAD2001-BMK1-IgG1K	34
Trastuzumab+YTE	WT2001-cAb21	80
			Trastuzumab+DLE	TAD2001-BMK1-v9-IgG1K	No or weak binding
Trastuzumab+EFYTE	WT2001-cAb51	Weak binding
			Negative control	W332-1.80.12.xAb.hIgG1	32

As shown in fig. 9, a dose response curve was obtained for Trastuzumab and Trastuzumab Fc variants binding ELISA assays of C1 q. According to EC50 calculations, the YTE variant of Trastuzumab Fc binds to C1q approximately 2.4 fold less than Trastuzumab, while the DLE variant of Trastuzumab Fc binds to little C1q, and the EFYTE variant of Trastuzumab Fc binds to C1q with weaker binding capacity, which is intermediate between the YTE variant and DLE variant of Trastuzumab Fc. Examples thermal stability analysis of tri-Fc variants

The melting temperature Tm was measured using Differential Scanning Fluorescence (DSF) to measure the thermal stability of Fc variants. The higher the thermal stability of the antibody, the less spontaneous unfolding and immunogenicity, and better drug formation.

The present example mixes an antibody with a dye that fluoresces when bound to a hydrophobic region. The mixture is subjected to a temperature change of 36 ℃ gradually rising to 86 ℃ and as the protein unfolds, the hydrophobic residues buried inside start to be exposed and the fluorescence intensity will increase dramatically. The Tm value was measured and calculated using QuantStudio Flex Real-Time PCR system, and the higher the Tm1 value, the better the thermal stability, and the specific data are shown in the following table:

As shown in the table above, tm1 of the YTE variant of Trastuzumab Fc was reduced by 5.3 ℃ compared to Trastuzumab, tm1 of the DLE variant of Trastuzumab Fc was reduced by 18 ℃ and Tm1 of the EFYTE variant of Trastuzumab Fc was reduced by 9.4 ℃. Since the Tm1 of a monoclonal antibody is generally in an acceptable normal range above 55 ℃, the EFYTE variant Tm1 of the invention has normal thermostability at 58.5 ℃.

In summary, the above embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, but any modifications, equivalent substitutions, improvements, etc. within the spirit and principle of the present invention should be included in the scope of the present invention.

Sequence listing

<110> Shanghai pharmaceutical biomedical Co., ltd

Shanghai Ming Biotechnology Co., ltd

<120> An optimized Fc variant and its use

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<170> SIPOSequenceListing 1.0

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<213> Artificial sequence (2 Ambystoma laterale x Ambystoma jeffersonianum)

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Glu Pro Lys Ser Cys Asp Lys Thr His Thr Cys Pro Pro Cys Pro Ala

1 5 10 15

Pro Glu Leu Leu Gly Gly Pro Glu Val Phe Leu Phe Pro Pro Lys Pro

20 25 30

Lys Asp Thr Leu Tyr Ile Thr Arg Glu Pro Glu Val Thr Cys Val Val

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Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe Asn Trp Tyr Val

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Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln

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Tyr Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu His Gln

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Asp Trp Leu Asn Gly Lys Glu Tyr Lys Cys Lys Val Ser Asn Lys Ala

100 105 110

Leu Pro Phe Pro Ile Glu Lys Thr Ile Ser Lys Ala Lys Gly Gln Pro

115 120 125

Arg Glu Pro Gln Val Tyr Thr Leu Pro Pro Ser Arg Asp Glu Leu Thr

130 135 140

Lys Asn Gln Val Ser Leu Thr Cys Leu Val Lys Gly Phe Tyr Pro Ser

145 150 155 160

Asp Ile Ala Val Glu Trp Glu Ser Asn Gly Gln Pro Glu Asn Asn Tyr

165 170 175

Lys Thr Thr Pro Pro Val Leu Asp Ser Asp Gly Ser Phe Phe Leu Tyr

180 185 190

Ser Lys Leu Thr Val Asp Lys Ser Arg Trp Gln Gln Gly Asn Val Phe

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Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gln Lys

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Ser Leu Ser Leu Ser Pro Gly Lys

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Claims

1. An immunoglobulin Fc region variant, characterized in that the Fc region variant comprises amino acid mutations at multiple sites compared to the parent Fc, the positions of the mutations are 239th, 330th, 252nd, 254th and 256th, and the amino acid sequence of the Fc region variant is shown in SEQ ID NO: 1.

2. The immunoglobulin Fc region variant according to claim 1, characterized in that the amino acid at position 239 is mutated from serine S to glutamic acid E.

3. The immunoglobulin Fc region variant according to claim 1, characterized in that the amino acid at position 252 is mutated from methionine M to tyrosine Y.

4 . The immunoglobulin Fc region variant according to claim 1 , wherein the amino acid at position 254 is mutated from serine S to threonine T.

5 . The immunoglobulin Fc region variant according to claim 1 , wherein the amino acid at position 256 is mutated from threonine T to glutamic acid E.

6. The immunoglobulin Fc region variant according to claim 1, characterized in that the amino acid at position 330 is mutated from alanine A to phenylalanine F.

7. The immunoglobulin Fc region variant according to claim 1, characterized in that the immunoglobulin is a human IgG antibody or a monoclonal antibody.

8. The immunoglobulin Fc region variant according to claim 1, wherein the amino acid positions are numbered according to the EU index of Kabat et al.

9. The immunoglobulin Fc region variant according to claim 1, characterized in that the ratio of the relative binding activity of the Fc variant binding to the human FcγRI receptor to that of the wild-type immunoglobulin Fc region to the human FcγRI receptor is 1, the ratio of the relative binding activity of the Fc variant binding to the human FcγRⅡa receptor to that of the wild-type immunoglobulin Fc region to the human FcγRⅡa receptor is 0.2-0.3, and the ratio of the relative binding activity of the Fc variant binding to the human FcγRⅢa receptor to that of the wild-type immunoglobulin Fc region to the human FcγRⅢa receptor is 10.

10. The immunoglobulin Fc region variant according to claim 1, characterized in that, in an acidic environment, the ratio of the relative binding activity of the Fc variant binding to the human FcRn receptor to that of the wild-type immunoglobulin Fc region binding to the human FcRn receptor is 10.

11. A polypeptide, characterized in that the polypeptide comprises the immunoglobulin Fc region variant according to claims 1-10.

12. The polypeptide according to claim 11, characterized in that the polypeptide is an IgG antibody.

13. Use of the polypeptide according to claim 12 in the preparation of a medicament for killing abnormal proliferative cells.

14. Use of the polypeptide according to claim 13 in the preparation of a drug for killing abnormal proliferative cells, characterized in that the abnormal proliferative cells are tumor cells, and the abnormal proliferative cells are contained in a patient's body.

15. Use of the polypeptide according to claim 14 in the preparation of a drug for killing abnormally proliferative cells, characterized in that the tumor cells are cancer cells, and the cancer cells are metastatic cancer cells.