An optimized Fc variant and its application

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

Technical Field

[0001] The present invention relates to the field of biomedicine technology, and in particular to an optimized Fc variant and application thereof. Background Art

[0002] Antibodies are a class of immunoglobulins that can specifically bind to antigens. In most mammals, including humans, antibodies are composed of two heavy chains and two light chains. Each polypeptide chain contains two different regions, namely the variable region and the constant region. The variable region has significant sequence diversity between different antibodies and is responsible for binding to specific antigens. The constant region has a lower degree of sequence diversity and is responsible for binding to some natural 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. The IgG heavy chain consists of four immunoglobulin (Ig) domains from the N-terminus to the C-terminus in the order of VH-CH1-CH2-CH3, and the IgG light chain consists of two immunoglobulin domains from the N-terminus to the C-terminus in the order of VL-CL.

[0003] In IgG, the Fc region contains CH2 and CH3 as well as the N-terminal hinge region leading to CH2. The Fc region interacts with many Fc receptors and ligands, inducing a range of effector functions. Fc gamma receptors (FcγRs) are an important class of Fc receptors that mediate communication between antibodies and immune cells. In humans, the receptor family includes FcγRI (CD64), including isoforms FcγRIa, FcγRIb, and FcγRIc; FcγRII (CD32), including isoforms FcγRIIa (including allotypes H131 and R131), FcγRIIb (including FcγRIIb-1 and FcγRIIb-2), and FcγRIIc; and FcγRIII (CD16), including isoforms FcγRIIIa (including allotypes V158 and F158) and FcγRIIIb (including allotypes FcγRIIIb-NA1 and FcγRIIIb-NA2).

[0004] The formation of Fc / FcγR complexes can recruit immune cells to the site of antigen binding, mediating the effector functions of cytotoxicity and phagocytes. Among them, the cell-mediated reaction in which non-specific cytotoxic cells expressing FcγR recognize antibodies bound to target cells and subsequently cause target cell lysis is called antibody-dependent cell-mediated cytotoxicity, or ADCC effect; the cell-mediated reaction in which non-specific cytotoxic cells expressing FcγR recognize antibodies bound to target cells and subsequently cause phagocytosis of target cells is called antibody-dependent cell-mediated phagocytosis, or ADCP effect.

[0005] The overlapping but separate sites on Fc are the contact surfaces with the complement protein C1q. The formation of the Fc / C1q complex can mediate complement-dependent cytotoxicity (CDC), similar to the ADCC mediated by the Fc / FcγR complex. The site between CH2 and CH3 on Fc mediates the interaction with the neonatal receptor FcRn.

[0006] Monoclonal antibodies are used in the treatment of a variety of diseases including cancer, inflammation and cardiovascular disease. Currently, for anticancer therapy, any slight improvement in mortality is considered successful, and the anti-tumor efficacy of antibodies is related to the ADCC effect, so there is a major need to enhance the ADCC effect. Due to the significant need to enhance the ability of antibodies to destroy target cells, mutations in Fc have been used in the past to obtain some proteins that can enhance ADCC, ADCP, and CDC effects, among which the DLE mutation (S239D / A330L / I332E, numbering according to the EU index of Kabat et al.) enhances binding to FcγRIIIa and enhances the ADCC effect, but the DLE mutation weakens thermal stability.

[0007] The half-life of an antibody is one of the important parameters for describing pharmacokinetic PK. In simple terms, it refers to the time required for the blood concentration of an antibody drug in vivo to drop to half. IgG binding to FcRn can recycle endocytosed antibodies from endosomes into the blood, a process that results in a serum half-life of the antibody between 1 and 3 weeks. The injection frequency of an antibody is related to the half-life, and a longer in vivo half-life can use a lower injection frequency or dose. The injection frequency of an antibody and an Fc fusion protein used as a drug is related to the half-life, and a longer in vivo half-life can use a lower injection frequency or dose. In the current prior art, mutations in Fc have been obtained that can enhance FcRn binding affinity and in vivo half-life of some proteins, among which the YTE mutation (M252Y / S254T / T256E, numbering according to the EU index of Kabat et al.) enhances binding to FcRn and increases in vivo half-life, with improved pharmacokinetic properties, but the YTE mutation weakens the ADCC effect.

[0008] Therefore, there is a need in the art for antibodies with enhanced therapeutic properties, including longer in vivo half-life and enhanced effector function, while having better thermal stability. Summary of the invention

[0009] To solve the above technical problems, the present invention provides an immunoglobulin Fc region variant, which comprises amino acid mutations at multiple sites compared to the parent Fc, wherein 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.

[0010] Specifically, the amino acid at position 239 was mutated from serine S to glutamic acid E.

[0011] Specifically, the amino acid at position 252 was mutated from methionine M to tyrosine Y.

[0012] Specifically, the 254th amino acid was mutated from serine S to threonine T.

[0013] Specifically, the amino acid at position 256 was mutated from threonine T to glutamic acid E.

[0014] Specifically, the amino acid at position 330 was mutated from alanine A to phenylalanine F.

[0015] Specifically, the immunoglobulin is a human IgG antibody or a monoclonal antibody.

[0016] Specifically, the amino acid position numbering is according to the EU index of Kabat et al.

[0017] Specifically, the ratio of the relative binding activity of the Fc variant binding to the human FcγRI receptor and the binding activity 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 and the binding activity 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 and the binding activity of the wild-type immunoglobulin Fc region to the human FcγRⅢa receptor is 10.

[0018] Specifically, in an acidic environment, the ratio of the relative binding activity of the Fc variant binding to the human FcRn receptor to the binding of the wild-type immunoglobulin Fc region to the human FcRn receptor is 10.

[0019] The present invention also provides a polypeptide comprising the immunoglobulin Fc region variant according to claims 1-10.

[0020] Specifically, the polypeptide is an IgG antibody or an Fc fusion protein.

[0021] The present invention also provides the use of the aforementioned polypeptide in preparing a drug for killing abnormally proliferative cells.

[0022] Specifically, the abnormally proliferative cells are tumor cells or tumor tissue-associated cells, and the abnormally proliferative cells are contained in the patient's body.

[0023] Specifically, the tumor cell is a cancer cell, and the cancer cell is a metastatic cancer cell.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The Fc region variant provided by the present invention has more optimized therapeutic properties through specific amino acid mutations. Compared with the prior art, it has a longer in vivo half-life, significantly improved pharmacokinetic properties, and can use a lower injection frequency or dose. There is no need to frequently administer the drug to maintain blood drug concentration, which solves the current technical problem that antibody drugs have a short half-life and need to continuously replenish the dose, saves drug costs, and has practical significance for the clinical research and implementation of drugs;

[0026] 2. The Fc region variant provided by the present invention not only has a longer half-life than the prior art, but also can enhance the ADCC effect. Experimental verification shows that the ADCC effect of the Fc variant provided by the present invention is enhanced by 3-7 times compared with the prior art, so that the anti-tumor effect of the antibody can be significantly improved;

[0027] 3. The Fc region variant provided by the present invention has significantly improved thermal stability compared with the prior art. The improvement in thermal stability significantly improves the therapeutic properties of the antibody, thereby improving the therapeutic efficiency of the drug, which has practical significance for the clinical treatment of tumors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a fitting result diagram of the binding data of Trastuzumab and Trastuzumab Fc variants to human FcγRI (CD64) determined by SPR;

[0029] Figure 2 This is a fitting result diagram of the binding data of Trastuzumab and Trastuzumab Fc variants to human FcγRⅡa (H167) determined by SPR;

[0030] Figure 3 This is a fitting result diagram of the binding data of Trastuzumab and Trastuzumab Fc variants to human FcγRⅢa (F176) determined by SPR;

[0031] Figure 4 This is a fitting result diagram of the binding data of Trastuzumab and Trastuzumab Fc variants to human FcRn at pH 6.0 determined by SPR;

[0032] Figure 5 This is a fitting result diagram of the binding data of Trastuzumab and Trastuzumab Fc variants to human FcRn at pH 7.4 determined by SPR;

[0033] Figure 6 The data graph is a graph of the antibody-dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants detected by the reporter gene method;

[0034] Figure 7 The data graph is a lactate dehydrogenase (LDH) release assay to detect antibody-dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants;

[0035] Figure 8 The data graph is a graph of antibody-dependent cell-mediated phagocytosis (ADCP) of Trastuzumab and Trastuzumab Fc variants detected by reporter gene method;

[0036] Fig. 9 Dose-effect curves obtained for ELISA testing of trastuzumab and trastuzumab Fc variants binding to C1q;

[0037] FIG10 is a graph showing the thermal stability test results of Trastuzumab and Trastuzumab Fc variants using DSF.

[0038] Fig. 9 In the figure, the X coordinate represents the C1q protein concentration, and the Y coordinate represents the OD450nm absorbance value. DETAILED DESCRIPTION

[0039] The technical scheme of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention. The materials, instruments and reagents used in the following examples, unless otherwise specified, can be obtained from commercial sources. The technical means used in the embodiments, unless otherwise specified, are conventional means well known to those skilled in the art.

[0040] For all positions discussed in the present invention, numbering is according to the EU index, and those skilled in the art of antibodies will appreciate that these conventions include non-continuous numbering of specific regions of immunoglobulin sequences, thereby enabling standardized references to conservative positions in the immunoglobulin family. Therefore, the position of any given immunoglobulin defined according to the EU index will not necessarily correspond to its continuous sequence. The Fc variant experiments performed in the present invention are performed in the context of the anti-HER2 antibody Trastuzumab, i.e., trastuzumab (Herceptin, a registered trademark of Genentech), used to treat metastatic breast cancer, and do not mean that the present invention is limited to any specific antibody.

[0041] Example 1 Fc receptor binding analysis of the Fc region variants provided by the present invention

[0042] As shown in the amino acid sequence table SEQ ID NO: 1, it is an Fc region variant provided by the present invention. This sequence is derived by mutation substitution at positions 216 to 447 based on the EU index, and the mutation sites include:

[0043] The amino acid at position 239 mutated from serine S to glutamic acid E;

[0044] The amino acid at position 252 mutated from methionine M to tyrosine Y;

[0045] The amino acid at position 254 mutated from serine S to threonine T;

[0046] The amino acid at position 256 mutated from threonine T to glutamic acid E;

[0047] The amino acid at position 330 mutated from alanine A to phenylalanine F.

[0048] In this example, surface plasmon resonance (SPR) was used to determine the binding of Trastuzumab and specified Trastuzumab Fc variants to human Fc receptors FcyRI, FcyRⅡa, FcyRⅢa and FcRn.

[0049] Surface plasmon resonance is an optical phenomenon that can be used to track the interactions between biomolecules in their native state in real time, with high sensitivity and high quantification. The operation method is to first couple a biomolecule (target molecule) to the biosensor surface, and then inject and flow a solution containing another biomolecule (analyte) that can interact with the target molecule over the biosensor surface.

[0050] In this example, when determining the binding of the antibody to human FcγR, FcyRI (CD64) or FcγRⅡa (H167) or FcγRⅢa (F176) with a His tag is first fixed on the CM5 chip, and then the WT and Fc variants of Trastuzumab are passed through the chip at a certain concentration range; when determining the binding of the antibody to human FcRn, the WT and Fc variants of Trastuzumab are first coupled to the surface of the CM5 chip, and then human FcRn is passed through the chip in a buffer at a certain concentration range.

[0051] Finally, the data were fitted by a 1:1 model and Langmiur analysis (applicable to FcyRI), or by a steady-state model (applicable to FcyRⅡa, FcyRⅢa and FcRn).

[0052] The binding data of trastuzumab and EFYTE variants of trastuzumab Fc to human FcγRI are shown in the following table:

[0053]

[0054] The binding data of trastuzumab and EFYTE variants of trastuzumab Fc to human FcγRⅡa are shown in the following table:

[0055]

[0056] The binding data of trastuzumab and EFYTE variants of trastuzumab Fc to human FcγRⅢa are shown in the following table:

[0057]

[0058] The binding data of trastuzumab and EFYTE variants of trastuzumab Fc to human FcRn in an acidic environment are shown in the following table:

[0059]

[0060] The binding data of trastuzumab and EFYTE variants of trastuzumab Fc to human FcRn under neutral conditions are shown in the following table:

[0061]

[0062] like Figure 1 As shown in FIG. 4 , the affinity of trastuzumab and the EFYTE variant of trastuzumab Fc to human FcγRI is basically the same, as shown in FIG. Figure 2As shown in Figure 2, the affinity of the EFYTE variant of Trastuzumab Fc to human FcγRⅡa is about 3.7 times lower than that of Trastuzumab. Figure 3 As shown in Figure 2, the affinity of the EFYTE variant of Trastuzumab Fc to human FcγRⅢa is about 10 times stronger than that of Trastuzumab. Figure 4 As shown in Figure 2, in an acidic environment of pH 6.0, the affinity of the EFYTE variant of Trastuzumab Fc to human FcRn is enhanced by about 10 times compared with Trastuzumab. Figure 5 As shown, in a neutral environment of pH 7.4, both Trastuzumab and the EFYTE variant of Trastuzumab Fc barely bind to human FcRn.

[0063] In summary, it can be seen that, compared with the parent Fc, the Fc region variant provided by the present invention has better affinity to FcγRⅢa and FcRn in an acidic environment, and the binding ability is significantly improved.

[0064] Example 2 Analysis of Fc effector function

[0065] In this example, antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and complement-dependent cytotoxicity (CDC) assays were performed on the Fc variants.

[0066] The ADCC effector function of Trastuzumab and its Fc-modified antibody was detected by the reporter gene method, and the EC50 was calculated using Graphpad Prism7 software. The specific operation was as follows: the CD16-V158-dependent luciferase reporter gene system was stably integrated into Jurkat cells (ATCC) and used as effector cells. Breast cancer cells SK-BR-3 (ATCC) highly expressed HER2, the target of Trastuzumab, and were used as target cells; effector cells and target cells were plated in a 96-well cell culture plate in a certain ratio, and the antibody to be tested was gradiently diluted and added to the cell plate, and the human IgG1 isotype control was used as a negative control. After incubation at 37°C for 4-5h, the luciferase activity was detected using a luciferase reporter gene assay kit (Promega), and the EC50 was calculated using Graphpad Prism7 software. The specific data are shown in the following table:

[0067]

[0068] like Figure 6As shown, the curve in the figure shows the dose dependence of ADCC on antibody concentration. According to EC50 calculation, the ADCC effect of the EFYTE variant of Trastuzumab Fc is about 7.2 times stronger than that of Trastuzumab, while the ADCC effect of the YTE variant of Trastuzumab Fc is about 1.7 times weaker than that of Trastuzumab.

[0069] The ADCC effect of Trastuzumab and Trastuzumab Fc variants was detected by lactate dehydrogenase (LDH) release method, and EC50 was calculated using Graphpad Prism7 software. In this embodiment, the ADCC effector function of Trastuzumab and its Fc modified antibody was evaluated by detecting the lactate dehydrogenase content released after tumor cells were killed by human peripheral blood mononuclear cells (PBMC). The specific operation is as follows: PBMC purchased from commercial channels are used as effector cells, and breast cancer cells SK-BR-3 (ATCC) highly express the target HER2 of Trastuzumab as target cells. The effector cells and target cells are spread into 96-well cell culture plates in a certain ratio, and the antibody to be tested is gradiently diluted and added to the cell plate, and the human IgG1 isotype control is used as a negative control. After incubation at 37°C for 4-5h, the test kit Cytotoxicity Detection Kit Plus (LDH) (Roche) is used for detection, and the EC50 is calculated using Graphpad Prism7 software. The data are shown in the following table:

[0070]

[0071] like Figure 7 As shown, the antibody-dependent cell-mediated cytotoxicity (ADCC) of Trastuzumab and Trastuzumab Fc variants was detected by lactate dehydrogenase (LDH) release assay. Figure 7 The curve shows the dose dependence of ADCC on antibody concentration. According to EC50 calculation, the ADCC effect of the EFYTE variant of Trastuzumab Fc is approximately 3.8 times stronger than that of Trastuzumab, while the ADCC effect of the YTE variant of Trastuzumab Fc is approximately 5.2 times weaker than that of Trastuzumab.

[0072] Another important FcγR-mediated effector function is antibody-dependent cell-mediated phagocytosis (ADCP). The engulfment of target cells can not only lead to the destruction of target cells, but also because engulfment is a potential mechanism for antigen-presenting cells to take up and process antigens, ADCP is related to the adaptive immune response. Therefore, this example also verifies the ability of the Fc variants provided by the present invention to mediate ADCP.

[0073] like Figure 8 As shown, the ADCP effect of Trastuzumab and Trastuzumab Fc variants was detected by the reporter gene method. In this example, the ADCP effector function of Trastuzumab and its Fc modified antibody was detected by the reporter gene method. The CD32-dependent luciferase reporter gene system was stably integrated in Jurkat cells (ATCC) and used as effector cells. Breast cancer cells SK-BR-3 (ATCC) highly expressed HER2, the target of Trastuzumab, and were used as target cells; effector cells and target cells were plated in a 96-well cell culture plate in a certain ratio, and the antibody to be tested was gradiently diluted and added to the cell plate, and the human IgG1 isotype control was used as a negative control. After incubation at 37°C for 4-5h, the luciferase activity was detected using a luciferase reporter gene assay kit (Promega), and the EC50 was calculated using Graphpad Prism7 software. The data are shown in the following table:

[0074]

[0075]

[0076] Figure 8 The ADCP effect was dose-dependent on antibody concentration. The EFYTE variant of Trastuzumab Fc had almost undetectable ADCP effect, while the YTE variant and DLE variant (S239D / I332E / A330L) of Trastuzumab Fc both exhibited weaker ADCP effect than Trastuzumab.

[0077] The binding site of complement protein C1q on Fc is close to the binding site of FcyR, so it is necessary to carefully determine whether the Fc variant maintains its ability to recruit and activate complement. The specific data are shown in the following table:

[0078] 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

[0079] like Fig. 9The figure shows the dose-effect curves obtained by the ELISA test of Trastuzumab and Trastuzumab Fc variants binding to C1q. According to the EC50 calculation, the binding of the YTE variant of Trastuzumab Fc to C1q is about 2.4 times weaker than that of Trastuzumab, while the DLE variant of Trastuzumab Fc hardly binds to C1q, and the EFYTE variant of Trastuzumab Fc has a weaker binding to C1q, and its binding ability is between the YTE variant and the DLE variant of Trastuzumab Fc. Example 3 Analysis of the thermal stability of Fc variants

[0080] Differential scanning fluorimetry (DSF) was used to measure the melting temperature (Tm) to measure the thermal stability of Fc variants. The higher the thermal stability of the antibody, the less spontaneous unfolding and immunogenicity it will produce, and the better the drugability.

[0081] In this example, the antibody is mixed with a dye, which will fluoresce when it binds to the hydrophobic region. The mixture is placed in a temperature change from 36°C to 86°C. As the protein unfolds, the buried hydrophobic residues begin to be exposed, and the fluorescence intensity will increase sharply. The Tm value is measured and calculated using the QuantStudio7 Flex Real-Time PCR system. The higher the Tm1 value, the better the thermal stability. The specific data is shown in the following table:

[0082]

[0083] As shown in the table above, compared with Trastuzumab, the Tm1 of the YTE variant of Trastuzumab Fc is reduced by 5.3° C., the Tm1 of the DLE variant of Trastuzumab Fc is reduced by 18° C., and the Tm1 of the EFYTE variant of Trastuzumab Fc is reduced by 9.4° C. Since the Tm1 of a monoclonal antibody is usually above 55° C., it is an acceptable normal range, and the Tm1 of the EFYTE variant of the present invention is 58.5° C., which has normal thermal stability.

[0084] In summary, the above embodiments are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Sequence Listing <110> Shanghai WuXi Biologics Co., Ltd. Shanghai WuXi Biologics Co., Ltd. <120> An optimized Fc variant and its application <130> CPC-NP-22-103255 <160> 1 <170> SIPO Sequence Listing 1.0 <210> 1 <211> 232 <212> PRT <213> Artificial sequence (2 Ambystoma laterale x Ambystoma jeffersonianum) <400> 1 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 35 40 45 Val Asp Val Ser His Glu Asp Pro Glu Val Lys Phe Asn Trp Tyr Val 50 55 60 Asp Gly Val Glu Val His Asn Ala Lys Thr Lys Pro Arg Glu Glu Gln 65 70 75 80 Tyr Asn Ser Thr Tyr Arg Val Val Ser Val Leu Thr Val Leu His Gln 85 90 95 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 195 200 205 Ser Cys Ser Val Met His Glu Ala Leu His Asn His Tyr Thr Gln Lys 210 215 220 Ser Leu Ser Leu Ser Pro Gly Lys 225 230

Claims

1. An immunoglobulin Fc region variant, characterized in that Compared with the parent Fc, the Fc region variant comprises amino acid mutations at multiple sites, wherein the positions of the mutations are 239th, 330th, 252nd, 254th and 256th. 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 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 was mutated from methionine M to tyrosine Y.

4. The immunoglobulin Fc region variant according to claim 1, characterized in that The amino acid at position 254 was mutated from serine S to threonine T.

5. The immunoglobulin Fc region variant according to claim 1, characterized in that The amino acid at position 256 was 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 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, characterized in that The amino acid position numbering is 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 and the binding activity 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 and the binding activity 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 and the binding activity 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 to the human FcRn receptor and the binding activity of the wild-type immunoglobulin Fc region 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 abnormally proliferative cells are tumor cells, and the abnormally proliferative cells are contained within a patient's body.

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

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