阅读说明：本技术 人白细胞介素2-聚乙二醇偶联物及其应用 (Human interleukin 2-polyethylene glycol conjugate and application thereof ) 是由 梁学军 叶诚浩 夏钢 陈龙飞 霍鹏超 杨金纬 应跃斌 宫丽颖 林欣 巩尊洋 衡新 于 2021-09-01 设计创作，主要内容包括：本发明提供了一种人白细胞介素2-聚乙二醇偶联物及其应用。本发明提供的人白细胞介素2-聚乙二醇偶联物包含含有至少一个非天然氨基酸的重组人白细胞介素2和偶联在所述至少一个非天然氨基酸上的PEG,所述非天然氨基酸为具有如式(Ⅰ)所示结构的含有羰基端基的化合物或其对映异构体,通过所述羰基端基与含有羟胺基端基的PEG形成肟键而使PEG偶联在所述至少一个非天然氨基酸上。本发明提供的人白细胞介素2-聚乙二醇偶联物可以单药或者与其他抗肿瘤药物联用,用于实体瘤、血液肿瘤等疾病的治疗,(The invention provides a human interleukin 2-polyethylene glycol conjugate and application thereof. The invention provides a human interleukin 2-polyethylene glycol conjugate, which comprises recombinant human interleukin2 containing at least one unnatural amino acid and PEG coupled on the at least one unnatural amino acid, wherein the unnatural amino acid is a compound containing a carbonyl end group and having a structure shown in formula (I) or an enantiomer thereof, and the carbonyl end group and the PEG containing a hydroxylamino end group are in a shape ofForming an oxime bond to couple the PEG to the at least one unnatural amino acid. The human interleukin 2-polyethylene glycol conjugate provided by the invention can be used for treating diseases such as solid tumors, blood tumors and the like by single medicine or combined use with other anti-tumor medicines,)

1. A human interleukin 2-polyethylene glycol conjugate comprising recombinant human interleukin2 comprising at least one unnatural amino acid and PEG conjugated to the at least one unnatural amino acid;

the unnatural amino acid is a compound containing a carbonyl end group and having a structure shown in a formula (I) or an enantiomer thereof, PEG is coupled on at least one unnatural amino acid through an oxime bond formed by the carbonyl end group and PEG containing a hydroxylamine end group,

wherein X and Z each independently represent a substituted or unsubstituted C0-C20 straight or branched alkylene group, one or more-CH groups therein₂Optionally substituted by one or more of-O-, -S-, -NH-, -C (O) -, -S (O) -, Y represents-C (O) -, -S (O) -, or-CH₂-, and A represents a substituted or unsubstituted C6-C20 aryl group;

when X, Z and A each independently represent a substituted group, the substituent is selected from one or more of hydroxyl, mercapto, halogen, nitro, cyano, alkyl, alkenyl, alkynyl, alkoxy, acyl, amido, carboxyl, ester, amino, sulfonyl, sulfinyl, cycloalkyl, heterocyclyl, aryl, heteroaryl.

2. The human interleukin 2-polyethylene glycol conjugate of claim 1, wherein the recombinant human interleukin2 is a protein represented by SEQ ID No. 3 or a functional active fragment thereof;

preferably, in the recombinant human interleukin2 comprising at least one unnatural amino acid, the position of the at least one unnatural amino acid is selected from one or more positions corresponding to positions P34, K35, T37, R38, L40, T41, F42, K43, F44, Y45, E61, E62, K64, P65, E67, E68, N71, L72 and Y107 of SEQ ID No. 2.

3. Human interleukin 2-polyethylene glycol conjugate according to claim 1 or 2, wherein the substituents are selected from one or more of hydroxy, mercapto, halogen, nitro, cyano, C1-C6 alkyl, C1-C6 alkoxy, acyl, amide, carboxy, ester, amino, sulfonyl, sulfinyl, C3-C8 cycloalkyl, C3-C8 heterocyclyl, C6-C20 aryl, C4-C10 heteroaryl;

preferably, X and Z each independently represent a C0-C10 linear or branched alkylene group, preferably a C0-C6 linear alkylene group, of which one or more-CH groups₂-may optionally be replaced by one or more of-O-, -S-, -NH-; more preferably, X and Z are not both C0 alkylene; and/or

The A represents a substituted or unsubstituted C6-C10 aryl group, and more preferably, the A represents a substituted or unsubstituted phenyl or naphthyl group.

4. The human interleukin 2-polyethylene glycol conjugate according to any one of claims 1 to 3, wherein the unnatural amino acid is a compound having a structure represented by formula (I-1),

wherein X, Z and A are each independently as defined in any one of claims 1 to 3;

preferably, the unnatural amino acid is a compound having a structure as shown in formula (I-2),

wherein X is as defined in any one of claims 1 to 3;

R₁and R₂Each independently represents hydrogen, hydroxy, mercapto, or a salt thereof,Halogen, nitro, cyano, C1-C6 alkyl, C1-C6 alkoxy, acyl, amido, carboxyl, ester group, amino, sulfonyl, sulfinyl, C3-C8 naphthenic base, C3-C8 heterocyclic group, C6-C20 aryl or C4-C10 heteroaryl.

5. The human interleukin 2-polyethylene glycol conjugate according to claim 4, wherein the unnatural amino acid is a compound having a structure represented by formula (I-3), formula (I-4), formula (I-5) or formula (I-6),

wherein X' represents a linear alkylene group having 0 to 6 carbon atoms, preferably having 0 to 4 carbon atoms, wherein one or more-CH groups₂-is optionally substituted with-O-and/or-NH-;

the R is₁And R₂Each independently as defined in claim 4.

6. The human interleukin 2-polyethylene glycol conjugate of claim 5, wherein the unnatural amino acid is a compound having one of the following structures:

7. the human interleukin 2-polyethylene glycol conjugate according to any one of claims 1 to 6, wherein the PEG comprising a hydroxylamino end group has a molecular weight of 20 to 50 KD.

8. Human interleukin 2-polyethylene glycol conjugate according to any of claims 1 to 7, wherein the recombinant human interleukin2 comprising at least one unnatural amino acid is prepared by codon expansion techniques or by chemical synthesis.

9. The human interleukin 2-polyethylene glycol conjugate of claim 8, wherein the codon expansion technique is implemented in E.

10. Use of the human interleukin 2-polyethylene glycol conjugate of any one of claims 1 to 9 for the preparation of a medicament for promoting immunity, preventing and/or treating solid and hematological tumors, and/or expanding CD8⁺Use in the manufacture of a medicament for T cells;

preferably, the solid tumor is bladder, bone, brain, breast, colorectal, esophageal, eye, head and neck, kidney, lung, melanoma, ovarian, pancreatic, or prostate cancer;

preferably, the hematological tumor is Chronic Lymphocytic Leukemia (CLL), Small Lymphocytic Lymphoma (SLL), Follicular Lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), Mantle Cell Lymphoma (MCL), Waldenstrom's macroglobulinemia, multiple myeloma, extranodal marginal zone B-cell lymphoma, nodal marginal zone B-cell lymphoma, Burkitt's lymphoma, non-Burkitt's high malignancy B-cell lymphoma, primary mediastinal B cell lymphoma (PMBL), immunoblastic large cell lymphoma, precursor B lymphoblastic B cell lymphoma, B cell prolymphocytic leukemia, lymphoplasmacytic lymphoma, splenic marginal zone lymphoma, plasma cell myeloma, plasmacytoma, mediastinal (thymic) large B cell lymphoma, intravascular large B cell lymphoma, primary effusion lymphoma, or lymphomatoid granulomatosis.

Technical Field

The invention relates to the field of biological pharmacy, in particular to a human interleukin 2-polyethylene glycol conjugate and application thereof.

Background

Interleukin-2 (Interleukin2, IL-2, often abbreviated as Interleukin 2) is an important immunomodulatory factor produced by activated T helper T lymphocytes of type I (Th1), known as T cell growth factors, whose major biological functions promote T cells, including CD4, in a dual manner of stimulation and anti-apoptosis⁺And CD8⁺T cells), and promote further secretion of cytokines. In addition, interleukin2 also stimulates NK cell proliferation, enhances NK killing activity, produces cytokines and induces LAK cell production; promoting B cell proliferation and secretion of antibodies; therefore, interleukin2 plays an important role in immune response of the body and in resisting viral infection, etc. (Gaffena S.L., Cytokine 28: 109e123, 2004).

Since the first discovery of IL-2 by Morgan et al in 1976, it has been widely used clinically. In 1991, rhIL-2 (product name: Aldesukin) produced by Cetus in the United states was approved by FDA to be on the market, widely applied to malignant tumors such as renal cell carcinoma, malignant melanoma, and malignant lymphoma (Proleukin Specification), and also has potential effect in adjuvant therapy of hepatitis B and hepatitis C infections (Tomova R. et al, Anticancer Research, 29: 5241-. The recombinant human interleukin2 biological product has 10 recombinant human interleukin2 biological products which are produced and marketed in China so far, is widely applied to the treatment of malignant tumors such as renal cell carcinoma, melanoma, breast cancer, bladder cancer, liver cancer, rectal cancer, lymph cancer, lung cancer and the like, the control of cancerous hydrothorax and ascites, the enhancement of the organism immunity of tumor patients after operations, radiotherapy and chemotherapy, the improvement of the cell immunity and the anti-infection capability of patients with congenital or acquired immunodeficiency, the treatment of various autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, sjogren syndrome and the like, and the recombinant human interleukin2 biological product has certain treatment effect on certain viral, bacillary diseases, intracellular parasitic bacteria infectious diseases such as hepatitis B, leprosy, tuberculosis, candida albicans infection and the like.

The human IL-2 precursor consists of 153 amino acid residues, and upon secretion from the cell, the signal peptide (containing 20 amino acid residues) is cleaved off, yielding 133 amino acids of mature IL-2 with a relative molecular weight of 15.4 kD. Activation of effector cells by IL-2 is achieved by binding to the IL-2 receptor (IL-2R) on the cell surface. It has now been found that the IL-2 receptor includes three of IL-2 ra, IL-2R β and IL-2R γ, which form a high affinity heteromultimeric glycoprotein functional complex IL-2R α β γ (Kd ═ 10)^-11mol/L). IL-2R beta and IL-2R gamma form a moderate affinity receptor complex IL-2R beta gamma (Kd 10 ═ 10)^{- 9}mol/L) has biological activity after being activated by IL-2; the IL-2R alpha subunit is a low affinity receptor form (Kd 10)^-8mol/L), its binding to IL-2 is unable to transmit intracellular proliferation signals; although IL-2R alpha and IL-2R beta can also form high affinity receptor complexes, no biological function can be activated by IL-2. The IL-2 receptor species are expressed to different extents in different cells, different developmental stages of the same cell type, and different states of the disease, thereby forming different receptor complexes. For example, LAK cell precursors express high levels of the IL-2R β 0 γ complex, which can attack and lyse cancer cells upon activation by IL-2; macrophages also express the IL-2R β 3 γ complex, and may also be activated by IL-2; monocytes express large amounts of IL-2R gamma and small amounts of IL-2R beta, while NK cells express large amounts of IL-2R beta and small amounts of IL-2R gamma, which form IL-2R beta gamma receptors of moderate affinity, respectively, which activate monocytes or NK cells after binding to high concentrations of IL-2 to form trimers; the surface of the activated T cell expresses IL-2R beta 2, IL-2R beta and IL-2R gamma, the excessive IL-2R alpha is beneficial to polymerizing with the IL-2R beta, and the IL-2R beta 1 is combined with the IL-2R gamma after being combined with the IL-2 to form a high-affinity receptor-IL-2 compound, so as to transmit signals and cause cell proliferation reaction. After the cell reaction, IL-2R alpha, IL-2R beta and IL-2R gamma are dissociated, and the cell is no longer sensitive to IL-2; human tumor cells also express IL-2 receptor, and IL-2 can inhibit tumor cell proliferation after binding with receptor complex on tumor cells, and IL-2 is improved due to different cancer cells expressing respective specific IL-2 receptor complexesThe structure can only act on the corresponding receptor on the surface of the specific tumor, can only attack cancer cells and reduce the damage to normal cells.

Based on the research theory, a plurality of researchers modify IL-2 in different directions, enhance the combination of the IL-2 with a specific receptor compound (such as an IL-2R beta gamma compound) on the surface of an anti-tumor related effector cell, activate cell types related to tumor killing, and simultaneously reduce the combination with an IL-2R alpha beta gamma compound highly expressed on the surface of a negative immunoregulation T cell (such as a Treg cell) as much as possible, thereby not only enhancing the drug effect, but also reducing the side effect of the drug. Existing modifications to IL-2 include: designing specific IL-2 variant proteins (e.g., Aron M.L. et al, Nature, 484(7395):529-33, 2012), altering the amino acid sequence of the binding site for IL-2R α, IL-2R β or IL-2R γ to render its spatial structure unfavorable for interaction with IL-2R α or to enhance interaction with IL-2R β or IL-2R γ; designing an IL-2/anti-IL-2 antibody (or IL-2 receptor) complex (e.g., Jared E.L. et al, J Immunother Cancer, 8 (1): e000673, 2020), using anti-IL-2 antibody to specifically mask the binding site to IL-2R, effecting alteration of IL-2 function and extension of in vivo half-life; fusion Expression of IL-2 with Fc or Human Serum Albumin (HSA) to achieve increased half-life of IL-2 in vivo (e.g., JianyongLei et al, Protein Expression and Purification, 84 (1): 154-; combining site-directed mutagenesis with HSA/Fc fusion to achieve both functional alteration and half-life extension (e.g., CN 112724259 a); non-site-specific coupling PEGylation of IL-2 extends the half-life of IL-2 (e.g., Deborah H.C. et al, Clin Cancer Res, 22(3):680-90, 2016).

The above studies on the modification of IL-2 have the following drawbacks:

1. the simple amino acid site-directed mutation can weaken the binding capacity with IL-2R alpha or strengthen the binding capacity with IL-2R beta or IL-2R gamma, but cannot effectively prolong the half-life of molecules, and the mutation product is easy to generate immunogenic reaction in vivo, easily reduces the biological activity of the product and generates larger toxicity risk.

2. Pure fusion expression (e.g., with Fc or HSA) or IL-2 modification, while able to extend the half-life of the molecule, does not yield significant advantages over unmodified IL-2 in practical use. Fusion expression can only realize modification of fusion molecules at the N terminal or the C terminal of a target protein, and optimization of modification sites cannot be realized.

3. Partial site-directed mutagenesis in combination with fusion-expressed IL-2 has not shown particular advantages in practical applications. (e.g., Rodrigo Vazzez-Lombardi et al, Nat Commun, 8:15373, 2017).

4. The conventional non-site coupling PEGylation IL-2 does not show special advantages in practical application, and the PEGylation IL-2 comprehensively weakening the binding capacity of IL-2R alpha is successful in stages, but the defects of difficult control of production process and quality, complex molecular structure, complex action mechanism and the like exist due to the characteristics of the non-site coupling process.

In response to the above limitations of IL-2 modification, researchers have developed PEG site-directed conjugation of IL-2 using codon expansion techniques (e.g., WO 2019028419A1) using Lys-azido as the unnatural amino acid with the formula shown below:

lys-azido terminal azide structure (-N)₃) Capable of reacting with alkyne-containing structures (e.g. BCN, i.e.) The conjugate (for example, Chinese patent CN 103153927B) is obtained by chemically linking modified carrier drugs (such as PEG and the like) and has high specific selectivity. However, the coupling method and the chemical modification method need to introduce an alkyne structure with higher cost, and an acceptable drug antibody coupling ratio can be obtained only when the equivalent is larger, so that the corresponding production cost is increased, the process is more complex, and the process conditions are harsh.

In summary, the currently aimed modification of IL-2 has many disadvantages, which require further research.

Disclosure of Invention

In view of the defects existing in the modification aspect of the prior IL-2, the invention provides a human interleukin 2-polyethylene glycol conjugate, which is formed by using a series of brand-new unnatural amino acids to perform site-specific mutagenesis on one or more natural amino acids in a recombinant human interleukin2 amino acid sequence and then performing site-specific coupling on polyethylene glycol (PEG) on the unnatural amino acids through an oximation reaction.

The invention also aims to provide the application of the human interleukin 2-polyethylene glycol conjugate, and the human interleukin 2-polyethylene glycol conjugate provided by the invention can be used for treating diseases such as malignant solid tumors, blood tumors and the like.

In a first aspect, the present invention provides a human interleukin 2-polyethylene glycol conjugate comprising recombinant human interleukin2 comprising at least one unnatural amino acid and PEG conjugated to the at least one unnatural amino acid;

wherein the unnatural amino acid is a compound containing a carbonyl end group with a structure shown as a formula (I) or an enantiomer thereof, PEG is coupled on at least one unnatural amino acid through an oxime bond formed by the carbonyl end group and PEG containing a hydroxylamine end group (i.e. aminoxy),

wherein X and Z each independently represent a substituted or unsubstituted C0-C20 straight or branched alkylene group, one or more-CH groups therein₂Optionally substituted by one or more of-O-, -S-, -NH-, -C (O) -, -S (O) -, Y represents-C (O) -, -S (O) -, or-CH₂-, and A represents a substituted or unsubstituted C6-C20 aryl group;

when X, Z and A each independently represent a substituted group, the substituent is selected from one or more of hydroxyl, mercapto, halogen, nitro, cyano, alkyl, alkenyl, alkynyl, alkoxy, acyl, amido, carboxyl, ester, amino, sulfonyl, sulfinyl, cycloalkyl, heterocyclyl, aryl, heteroaryl.

As shown in example 9, the present inventors found that the azide structure (-N) at the Lys-azido terminal is expensive and complicated₃) Is easily reduced to amino structure (-NH) when inserted into recombinant human interleukin2₂) (as shown in formula 1), thereby losing the coupling activity, and thus the reduction reaction reduces the yield in the preparation process of the conjugate.

The non-natural amino acid of the invention introduces carbonyl as an active reaction group at the end, has novel structure, simple preparation, mild coupling condition and lower production cost, and is not easy to cause structural change to cause loss of reaction activity when protein is inserted; the unnatural amino acid of the invention also comprises an aryl group connected with a carbonyl group, the stability of the obtained conjugate can be further enhanced by introducing the aryl group, and the conjugate is not easy to decompose even under the condition of lower pH. In addition, the unnatural amino acid also comprises an alkylene group with a certain chain length, so that the compound has better flexibility and is easier to form a conjugate.

In the conjugate provided by the invention, the unnatural amino acid contained in the recombinant human interleukin2 contains carbonyl end groups, and the used PEG contains hydroxylamine end groups and has a structure shown in a formula (II):

the carbonyl group in the unnatural amino acid can perform oximation reaction with the hydroxylamine group in the PEG to form an oxime bond, and the structure is shown as the formula (III), so that the PEG is coupled to the unnatural amino acid.

In the formula (III), D 'represents a residue of the recombinant human interleukin2 of the present invention from which a carbonyl moiety of an unnatural amino acid is removed, and D' represents removal of "NH₂-O- "end group PEG.

Compared with wild type IL-2 or commercial recombinant human IL-2, the conjugate provided by the invention has reduced binding force with IL-2R alpha and retains the binding activity with IL-2R beta gamma, and CD8 is bound by IL-2R beta gamma complex⁺Activation of T cells retains activation and expansion of CD8⁺The capacity of T cells can inhibit the expansion of Treg cells, the half-life period of the T cells in vivo is remarkably prolonged, and the T cells can effectively promote immunity and inhibit tumors. In addition, the conjugate provided by the invention has higher coupling rate and better stability.

In some preferred embodiments according to the present invention, the recombinant human interleukin2 is a protein represented by SEQ ID No. 3 or a functionally active fragment thereof.

In some preferred embodiments according to the invention, the position of the at least one unnatural amino acid in the recombinant human interleukin2 comprising the at least one unnatural amino acid is selected from one or more of the positions corresponding to position P34, position K35, position T37, position R38, position L40, position T41, position F42, position K43, position F44, position Y45, position E61, position E62, position K64, position P65, position E67, position E68, position N71, position L72 and position Y107 of SEQ ID No. 2. In some more preferred embodiments according to the invention, in the recombinant human interleukin2 comprising at least one unnatural amino acid, the position of the at least one unnatural amino acid is selected from the group consisting of positions corresponding to one or more of positions K35, T41, K43, Y45, E61, K64 and P65 of SEQ ID NO 2.

Among the unnatural amino acids described in the present invention, "C0 to Cn" includes C0 to C1, C0 to C2, and … … C0 to Cn, and when C0 is represented, this means that the group is not present, and C atoms at both ends are directly bonded. For example, the "C0-C6" group refers to a moiety having 0-6 carbon atoms, i.e., the group is absent, contains 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, or 6 carbon atoms; the "C6-C10" group refers to 6-10 carbon atoms in the moiety, i.e., 6, 7, 8, 9, or 10 carbon atoms.

In the non-natural amino acids described herein, "aryl" refers to a carbocyclic aromatic system containing one or two rings, wherein the rings may be joined together in a fused fashion. "aryl" includes monocyclic or bicyclic aryl groups such as phenyl, naphthyl, tetrahydronaphthyl aromatic groups. Preferably aryl is C6 to C10 aryl, more preferably aryl is phenyl and naphthyl, most preferably phenyl.

In some preferred embodiments according to the present invention, the substituent may be selected from one or more of hydroxyl, thiol, halogen, nitro, cyano, C1-C6 alkyl, C1-C6 alkoxy, acyl, amide, carboxyl, ester, amino, sulfonyl, sulfinyl, C3-C8 cycloalkyl, C3-C8 heterocyclic, C6-C20 aryl, and C4-C10 heteroaryl.

In some preferred embodiments according to the invention, X and Z may each independently represent a C0-C10 linear or branched alkylene group, one or more of which are-CH₂-may optionally be replaced by one or more of-O-, -S-, -NH-; in some more preferred embodiments according to the invention, X and Z may each independently represent a C0-C6 linear alkylene group, one or more-CH therein₂-may optionally be replaced by one or more of-O-, -S-, -NH-; in some more preferred embodiments according to the invention, said X and Z are not both C0 alkylene, i.e. the X and Z groups cannot be both absent.

In some preferred embodiments according to the present invention, the a may represent a substituted or unsubstituted C6 to C10 aryl group, and more preferably, the a may represent a substituted or unsubstituted phenyl or naphthyl group.

In some preferred embodiments according to the present invention, the unnatural amino acid can be a compound having a structure as shown in formula (I-1),

wherein X, Z and A are each independently as defined in any one of the preceding claims.

In some preferred embodiments according to the present invention, the unnatural amino acid can be a compound having a structure as shown in formula (I-2),

wherein X is as defined in any of the above claims;

R₁and R₂Each independently represents hydrogen, hydroxyl, sulfydryl, halogen, nitro, cyano, C1-C6 alkyl, C1-C6 alkoxy, acyl, amido, carboxyl, ester group, amino, sulfonyl, sulfinyl, C3-C8 naphthenic base, C3-C8 heterocyclic group, C6-C20 aryl or C4-C10 heteroaryl.

In some more preferred embodiments according to the present invention, the unnatural amino acid is a compound having a structure represented by formula (I-3), formula (I-4), formula (I-5), or formula (I-6),

wherein X' represents a linear alkylene group having 0 to 6 carbon atoms, more preferably a linear alkylene group having 0 to 4 carbon atoms, of which one or more-CH groups₂-is optionally substituted with-O-and/or-NH-;

the R is₁And R₂Each independently as defined in any of the above claims.

The unnatural amino acids of the invention include optically pure enantiomers and racemates.

In some more preferred embodiments according to the invention, the unnatural amino acid of the invention is a compound having one of the following structures:

in some preferred embodiments according to the invention, the compound of the invention contains a hydroxylamino group ("NH)₂-O- ") end group PEG can have a molecular weight of 10-100 KD, including but not limited to about 10KD, 20KD, 30KD, 40KD, 50KD, 60KD, 70KD, 80KD, 90KD, 100KD or any combination of molecular weight ranges. In some more preferred embodiments according to the invention, the compound contains "NH₂The molecular weight of PEG with the end group of-O- "can be 20-50 KD.

In some preferred embodiments according to the present invention, the recombinant human interleukin2 comprising at least one unnatural amino acid according to the invention can be prepared by codon expansion techniques or by chemical synthesis. In some more preferred embodiments according to the invention, the recombinant human interleukin2 comprising at least one unnatural amino acid of the invention is prepared by a codon expansion technique, wherein the codon expansion technique is performed in E.coli.

The codon expansion technology of the invention specifically comprises the following steps: compared with the nucleic acid molecule for coding the recombinant human interleukin2, the nucleic acid molecule for mutating the recombinant human interleukin2 is different in that: a codon corresponding to an amino acid at least one of positions P34, K35, T37, R38, L40, T41, F42, K43, F44, Y45, E61, E62, K64, P65, E67, E68, N71, L72 and Y107 of SEQ ID NO 2 is mutated to an amber codon UAG; the mutated nucleic acid molecule is expressed in E.coli and the carbonyl-containing lysine analog of the invention (e.g., NBOK) is incorporated into the expressed recombinant human interleukin2 by an orthogonal tRNA synthetase/tRNA pair. The working principle of the codon expansion system is as follows: tRNA^PylCan not utilizeHost cell lysyl tRNA enzymes, exclusively tRNA^PylRS acylation, tRNA^PylRS can only acylate tRNA^PylNot acylating other tRNA's, i.e. tRNA' s^PylAnd tRNA^PylOrthogonality among RSs, only tRNA^PylThe RS can acylate the corresponding unnatural amino acid to the orthogonal tRNA, and can acylate only the tRNA, but not other tRNA. The codon expansion system allows a lysine analog containing a carbonyl group to correspond to the UAG codon of amber (i.e., tRNA)^PylThe corresponding codon is UAG), thereby introducing carbonyl-containing lysine analogs into IL-2 in a targeted manner.

In some preferred embodiments according to the present invention, the step of protein denaturation, renaturation, ultrafiltration is further included after the expression of the mutated recombinant human interleukin2 in E.coli.

In some preferred embodiments according to the present invention, the oximation reaction of the unnatural amino acid in the recombinant human interleukin2 with PEG having a hydroxylamino group may comprise the following processes: before the oximation reaction, the pH of the mutated recombinant human interleukin2 solution is adjusted to about 3.5-4.5 (for example, the pH is adjusted to about 4.0 by using 2M acetic acid solution), the protein concentration is adjusted to 0.5-1.5 mg/ml (for example, sodium acetate buffer solution with 20mM and pH4.0) according to a certain molar ratio (for example, protein: PEG is 1: 15), the solution is fully dissolved, sealed and shaken in a constant temperature shaking table for reaction (for example, reaction is carried out for 30-60 h). The reaction can be followed by analysis of the coupling by conventional detection methods (e.g., RP-HPLC).

In some preferred embodiments according to the present invention, the reaction solution after the oximation reaction (i.e., coupling reaction) contains partially unreacted IL-2, hetero-protein, unreacted PEG, and thus can be further purified by cation exchange chromatography. For example, the following purification process may be used: chromatography medium: capto MMC; and (3) an equilibrium buffer: 20mM sodium citrate buffer (pH 3.0), elution buffer: 20mM sodium citrate buffer solution-1M NaCl (pH 7.8), adjusting the pH of the coupling reaction solution to 3.0 +/-0.2 by using an equilibrium buffer solution, adjusting the conductivity to be less than or equal to 5ms/cm, loading the coupling reaction solution to Capto MMC, performing linear elution by using an elution buffer solution (0-100% of the elution buffer solution, 20CV), and collecting target protein components. This purification process results in a target protein sample with a purity of about 95%.

In a second aspect, the present invention also provides the use of a human interleukin 2-polyethylene glycol conjugate according to any one of the above technical schemes for preparing a medicament for promoting immunity, preventing and/or treating solid tumors (especially malignant solid tumors) and hematological tumors, and/or expanding CD8⁺Use in the manufacture of a medicament for T cells.

In some preferred embodiments according to the invention, the solid tumor is bladder, bone, brain, breast, colorectal, esophageal, eye, head and neck, kidney, lung, melanoma, ovary, pancreas or prostate cancer.

In some preferred embodiments according to the invention, the hematological tumor is Chronic Lymphocytic Leukemia (CLL), Small Lymphocytic Lymphoma (SLL), Follicular Lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), Mantle Cell Lymphoma (MCL), Waldenstrom macroglobulinemia, multiple myeloma, extranodal marginal zone B-cell lymphoma, nodal marginal zone B-cell lymphoma, Burkitt's lymphoma, non-Burkitt's high malignancy B-cell lymphoma, primary mediastinal B cell lymphoma (PMBL), immunoblastic large cell lymphoma, precursor B lymphoblastic B cell lymphoma, B cell prolymphocytic leukemia, lymphoplasmacytic lymphoma, splenic marginal zone lymphoma, plasma cell myeloma, plasmacytoma, mediastinal (thymic) large B cell lymphoma, intravascular large B cell lymphoma, primary effusion lymphoma, or lymphomatoid granulomatosis.

In a third aspect, the present invention also provides a kit comprising any of the human interleukin-2-polyethylene glycol conjugates described above.

In a fourth aspect, the present invention also provides a method of prophylaxis and/or treatment of solid tumours (particularly malignant solid tumours) or haematological tumours comprising the step of administering to a patient in need thereof a therapeutically effective amount of a human interleukin 2-polyethylene glycol conjugate as described in any of the above.

In some preferred embodiments according to the invention, the solid tumor is bladder, bone, brain, breast, colorectal, esophageal, eye, head and neck, kidney, lung, melanoma, ovary, pancreas or prostate cancer.

In some preferred embodiments according to the invention, the hematological tumor is Chronic Lymphocytic Leukemia (CLL), Small Lymphocytic Lymphoma (SLL), Follicular Lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), Mantle Cell Lymphoma (MCL), Waldenstrom macroglobulinemia, multiple myeloma, extranodal marginal zone B-cell lymphoma, nodal marginal zone B-cell lymphoma, Burkitt's lymphoma, non-Burkitt's high malignancy B-cell lymphoma, primary mediastinal B cell lymphoma (PMBL), immunoblastic large cell lymphoma, precursor B lymphoblastic B cell lymphoma, B cell prolymphocytic leukemia, lymphoplasmacytic lymphoma, splenic marginal zone lymphoma, plasma cell myeloma, plasmacytoma, mediastinal (thymic) large B cell lymphoma, intravascular large B cell lymphoma, primary effusion lymphoma, or lymphomatoid granulomatosis.

In some preferred embodiments according to the present invention, the human interleukin-2-polyethylene glycol conjugate may be administered alone or in combination with one or more other anti-tumor agents.

The technical scheme provided by the invention has the following advantages:

(1) the novel unnatural amino acid can be introduced into a designated site through a codon expansion technology, so that the precise site-specific coupling of PEG and interleukin-2 is realized, the defect that the precise coupling cannot be realized in the traditional random coupling mode is overcome, and the product uniformity is high.

(2) Compared with the common lysine analogue (such as Lys-azido) containing an azide group, the unnatural amino acid disclosed by the invention is simpler and more convenient to prepare, better in safety, not easy to inactivate when protein is inserted, higher in combination rate with PEG, better in stability of the obtained conjugate, and still capable of achieving coupling efficiency of over 95% after inclusion body renaturation of recombinant protein.

(3) Through the design and screening of mutation sites, the invention obtains the interleukin-2 mutation site which can reduce the binding activity of IL-2R alpha and keep the binding activity of IL-2R beta and IL-2R gamma relatively unchanged, so that the specificity of the site-specific modified human interleukin-2-polyethylene glycol conjugate in a tumor microenvironment can promote CD8⁺Proliferation of T cells, and for CD4⁺The proliferation of T cells has no obvious effect, thereby being beneficial to the immunotherapy of tumors.

(4) The conjugates of the invention achieve an increase in the half-life of IL-2 in vivo by conjugation with PEG, thereby reducing the frequency of administration to the patient.

Drawings

FIG. 1 is a schematic representation of expression plasmid NB1S 3-WT.

FIG. 2 is a schematic representation of the helper plasmid NB 1W.

FIG. 3 is an SDS-PAGE electrophoresis of fermentation products obtained after addition of the unnatural amino acid NBOK of rhIL-2 expressing strains of different mutation sites obtained in example 2 (the band positions of the objective products are indicated by arrows); wherein, lane 1: NBOK rhIL2-K35-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 2: NBOK rhIL2-T41-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 3: NBOK rhIL2-K43-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 4: NBOK rhIL2-Y45-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 5: NBOK rhIL2-E61-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 6: NBOK rhIL2-K64-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 7: NBOK rhIL2-P65-BL21 thalli are fed, crushed, centrifuged and precipitated; lane 8: NBOK rhIL2-Y45-BL21 thalli sediment is added to obtain inclusion bodies after washing.

FIGS. 4A and 4B are RP-HPLC profiles before and after conjugation of mutant rhIL-2 with PEG in example 3, respectively; wherein, FIG. 4A shows each mutant rhIL-2 before conjugation, in which about 22.5min is the main peak of the target protein; FIG. 4B shows the conjugated mutant rhIL-2(PEG is 30KD PEG), wherein the main peak of the target protein is at about 21 min.

FIG. 5 shows the RP-HPLC profiles of the conjugate 30KD PEG-rhIL2-Y45 before and after column chromatography in example 4.

FIG. 6 is a mass spectrum of rhGH-V91 in example 9.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the following specific examples.

Reagents or raw materials used in the preparation examples and examples of the present invention are commercially available products unless otherwise specified; the experimental methods used are conventional in the art unless otherwise specified.

Human YT cells are disclosed in the literature "Yodoi, J.et al. (1985),. TCGF (IL 2) -receptor inducing factor(s),. I.Regulation of IL2 receptor on a natural killer-like cell line (YT cells),. Journal of Immunology,134(3),. 1623-.

Preparation example 1 preparation of unnatural amino acid NBOK

The structural formula of NBOK is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) in a reaction flask, p-methylacetophenone (4.0mL,30.0mmol) was added, solvent DCE (50.0mL) was added, NBS (6.41g,36.0mmol) and BPO (0.05g,0.3mmol) were added, and the mixture was refluxed at 80 ℃ for 24 hours, then the vessel was cooled in ice water to precipitate a solid, which was removed by filtration, and then saturated Na was used₂CO₃Washed 3 times, extracted 3 times with DCM, the organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the crude product 1-1(5.46g, 85% yield) which was used in the next step without purification.

b) In a reaction flask, the product 1-1(2.73g,12.80mmol) was added, the solvent dioxane (40mL) and water (40mL) was added, calcium carbonate (7.68g,76.8mmol) was added, the mixture was refluxed at 105 ℃ for 24 hours, cooled to room temperature, filtered to remove solids, extracted 3 times with DCM, the organic phases were combined, concentrated under reduced pressure, column chromatographed (eluent: PE: EA ═ 3:1) purification gave the product 1-2(1.80g, 94% yield).

c) In a two-necked reaction flask, p-nitrophenyl chloroformate (2.90g, 14.4mmol) was added, solvent DCM (10.0mL) was added, the temperature was reduced to 0 ℃, product 1-2(1.80g,12.0mmol) and pyridine (1.2mL, 14.4mmol) were added, after stirring at room temperature for 18 hours, saturated sodium carbonate solution (10mL) was added to the reaction solution, extraction was performed with DCM (50mL) 3 times, the organic phases were combined, washed with water 2 times, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, purified by column chromatography (eluent: PE: EA ═ 5:1) purification afforded the product 1-3(3.14g, 83% yield).

d) In a reaction flask, product 1-3(1.26g,4.0mmol) and Fmoc-Lys-OH hydrochloride (1.40g,3.33mmol) were added, solvent dioxane (15mL) and water (5mL) were added, triethylamine (1.2mL,8.3mmol) was added, the mixture was reacted at room temperature for 24 hours, and appropriate 1M HCl solution was added, extracted with DCM, and concentrated under reduced pressure to give crude product 1-4, which was used directly in the next step.

e) In a reaction flask, the product 1-4(1.10g,0.19mmol) was dissolved in DCM (10mL), diethylamine (5.0mL) was added, reacted at room temperature for 6 hours, the product precipitated, filtered and slurried with DCM 3 times to obtain the desired product 1-5(817mg, 63% yield over two steps).

¹H-NMR (400MHz, heavy water) δ 8.04(d, J ═ 8.4Hz,2H),7.55(d, J ═ 8.0Hz,2H),5.21(s,2H),3.74(t, J ═ 6.0Hz,1H),3.17(t, J ═ 6.4Hz,2H),2.70(s,3H), 1.95-1.83 (m,2H), 1.62-1.52 (m,2H), 1.47-1.35 (m,2H).

Preparation example 2 preparation of unnatural amino acid NPAK

The structural formula of NPAK is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) into a reaction flask, p-chloroacetophenone (1.00g,6.47mmol) was added, and diethyl malonate (6.84g,47.70mmol) and KHCO were added under a nitrogen atmosphere₃(0.97g,9.70mmol) and K₂CO₃(1.34g,9.70mmol) followed by the addition of Pd (dba)₂(0.019g,0.030mmol) and P (t-Bu)₃HBF₄(0.021g,0.071mmol), replacing nitrogen after adding, heating to 160 deg.C, and reacting for 40 h. After completion of the TLC detection reaction, water (30mL) was added to the reaction solution, extraction was performed 3 times with EA, the organic phases were combined, washed 2 times with water, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure at 0-5 ℃ to give a colorless transparent liquid, which was purified by column chromatography (eluent: PE: EA: 10:1) to give 2-1(0.80g, yield 60%).

b) LiOH (0.30g,11.64mmol) and water (5.0mL) were added to a reaction flask, ethanol (10mL) was added, product 2-1(0.80g,3.88mmol) was added, after stirring at room temperature for 2 hours, the completion of the reaction was checked by TLC, 2M HCl solution was added to the reaction solution to adjust pH to 1-2, extraction was performed with EA 3 times, the organic phases were combined, washed with water 2 times, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain product 2-2(0.5g, yield 72%).

c) To a reaction flask, product 2-2(0.20g,1.12mmol) was added followed by N-hydroxysuccinimide (NHS,0.19g,1.68mmol), DIPEA (0.07g, 0.56mmol), and DCM (2.0 mL). And cooling to 0-5 ℃, adding a solution of DCC (0.23g,1.12mmol) and DCM (2.0mL), and reacting for 2 hours under the condition of heat preservation. Warmed to room temperature and stirred overnight. After TLC detection reaction was complete, filtration was carried out, washing was carried out with DCM, the mother liquor was concentrated under reduced pressure, and column chromatography was carried out (eluent: PE: EA: 5:1) to obtain 2-3(0.19g, yield 62%).

d) To a reaction flask, the product 2-3(0.10g,0.36mmol) was added, followed by triethylamine (0.04g,0.36mmol), Fmoc-Lys-OH hydrochloride (0.13g,0.36mmol), dioxane (2.0mL) and water (2.0mL), and the reaction was stirred at room temperature for 18 h. After completion of TLC detection, the reaction was concentrated under reduced pressure, extracted 3 times with EA, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (eluent: DCM: MeOH: 15:1) to give 2-4(0.03g, yield 61%) as an oily liquid product.

e) In a reaction flask, product 2-4(0.08g,0.15mmol), DCM (1.0mL) and piperidine (0.04g, 0.47mmol) were added and stirred at room temperature for 3 h. After TLC detection reaction is completed, concentration is carried out under reduced pressure, the mixture is beaten by petroleum ether (5mL) for 1h, filtration is carried out, a filter cake is beaten by petroleum ether (5mL) for 1h, filtration is carried out, beating is carried out on the filter cake for 4 times by ethanol to remove residual piperidine, and finally off-white solid 2-5(0.02g, yield 43%) is obtained.

¹H-NMR (400MHz, heavy water) δ 7.85(d, J ═ 8.2Hz,2H),7.33(d, J ═ 8.2Hz,2H),3.94(t, J ═ 6.3Hz,1H),3.56(s,2H),3.12(t, J ═ 6.8Hz,2H),2.54(s,3H), 1.80-1.70 (m,2H), 1.54-1.45 (m,2H),1.40-1.224(m,2H).

Preparation example 3 preparation of unnatural amino acid NBPK

The structural formula of NBPK is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) in a reaction flask, p-methylacetophenone (4.0mL,30.0mmol) was added, solvent DCE (50.0mL) was added, NBS (6.41g,36.0mmol) and BPO (0.05g,0.3mmol) were added, and the mixture was refluxed at 80 ℃ for 24 hours. After TLC detection reaction is completed, the container is placed into ice water for cooling, solid is separated out, solid is removed by filtration, and saturated Na is used₂CO₃Washed 3 times, extracted 3 times with DCM, the organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give crude product 3-1(5.46g, 85% yield) which was used in the next step without purification.

b) In a reaction flask, NaH (0.58g,14.64mmol, 60%) was added, dried solvent THF (20mL) was added, and the solution was slowly added under ice-bath coolingEthylene glycol (6.7mL,122.0mmol) was stirred at room temperature for 1 hour. Then the product 3-1(2.60g,12.2mmol) was added and heated at 70 ℃ under reflux for 48h until the reaction was complete. Slowly dropping saturated NH under ice-bath cooling₄After quenching NaH with Cl, washing with water, extraction with EtOAc 3 times, combining the organic phases, drying with anhydrous sodium sulfate, filtration, concentration under reduced pressure, and purification by column chromatography (eluent: PE: EA ═ 2:1) yielded the product 3-2(1.39g, yield 59%).

c) In a reaction flask, product 3-2(1.39g,7.2mmol) was added, solvent DCM (10mL) was added, p-nitrophenyl chloroformate (1.74g,8.64mmol) and pyridine (0.7mL,8.64mmol) were added under cooling in an ice bath, and the mixture was stirred at room temperature for 18 hours. After completion of the TLC detection reaction, water was added and the reaction mixture was washed with EtOAc and extracted 3 times, the organic phases were combined, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure and purified by column chromatography (eluent: PE: EA ═ 3:1) to give the product 3-3(2.27g, yield 88%).

d) In a reaction flask, the product 3-3(2.27g,6.32mmol) was added, the solvent dioxane (16mL) and water (4mL) was added, Fmoc-Lys-OH hydrochloride (2.13g,5.27mmol) was added, triethylamine (1.85mL,13.2mmol) was added and the reaction was stirred at room temperature for 18 hours to completion. Adding appropriate amount of 1M HCl to adjust pH to about 2, extracting with ethyl acetate, mixing organic phases, adding anhydrous sodium sulfate, drying, filtering, and concentrating under reduced pressure to obtain crude product 3-4, which is directly used in the next step.

e) In a reaction flask, the product 3-4 of the previous step was dissolved in DCM (10mL), and diethylamine (5mL) was added and reacted at room temperature for 6 hours. After TLC detection of completion of the reaction, concentration under reduced pressure and column chromatography (eluent: DCM: MeOH: H)₂O40: 10:1) to give the product as a white solid 3-5(0.95g, 49% yield over two steps).

¹H-NMR (400MHz, heavy water) δ 8.04(d, J ═ 8.0Hz,2H),7.56(d, J ═ 8.0Hz,2H),4.72(s,2H),4.25(s,2H),3.81(s,2H),3.74(t, J ═ 6.0Hz,1H), 3.16-3.08 (m,2H),2.70(s,3H), 1.97-1.79 (m,2H), 1.60-1.48 (m,2H), 1.48-1.35 (m,2H).

Preparation example 4 preparation of unnatural amino acid NPOK

The structural formula of NPOK is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) in a reaction flask, triphosgene (BTC,2.18g,7.35mmol) was added, solvent THF (10.0mL) was added, p-hydroxyacetophenone (2.0g,14.7mmol) and pyridine (1.5mL,17.64mmol) were added under cooling in an ice bath, and the mixture was reacted at room temperature for 24 hours. After completion of the TLC check reaction, the appropriate amount of water was added, extracted 3 times with EtOAc and the organic phases were combined. Dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give crude 4-1(1.20g) which was used directly in the next step.

b) In a reaction flask, Boc-lysine (1.1g,5.0mmol) was added, solvent DCM (10.0mL) was added, and product 4-1(1.20g) and triethylamine (2mL,15mmol) were added. Stirring at room temperature for 24 hr, detecting by TLC, adding appropriate amount of 1M HCl to adjust pH to weak acidity, extracting with DCM for 3 times, and mixing organic phases. Dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, and subjected to column chromatography (eluent: DCM: MeOH ═ 5:1) to give the product 4-2(1.70g, yield 84%).

c) In a reaction flask, the product 4-2(1.70g,4.2mmol) was added, solvent DCM (5mL) was added, trifluoroacetic acid (5mL) was added, and the mixture was reacted at room temperature for 1 hour. After TLC detection, the reaction mixture is directly concentrated under reduced pressure and subjected to column chromatography (eluent: DCM: MeOH: H)₂O40: 10:1) gave 4-3(1.19g, 67% yield).

¹H-NMR (400MHz, heavy water) δ 8.09(d, J ═ 8.6Hz,2H),7.31(d, J ═ 8.6Hz,2H),3.78(t, J ═ 6.0Hz,1H),3.27(t, J ═ 6.8Hz,2H),2.70(s,3H), 1.98-1.87 (m,2H), 1.72-1.60 (m,2H), 1.55-1.43 (m,2H).

Preparation example 5 preparation of unnatural amino acid NBGK

The structural formula of NBGK is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) in a reaction flask, p-methylacetophenone (8.0mL,60.0mmol) was added, solvent DCE (80.0mL) was added, NBS (12.82g,72.0mmol) and BPO (145mg,0.6mmol) were added, and the mixture was refluxed at 90 ℃ for 24 hours. After TLC detection reaction is completed, the container is placed into ice water for cooling, solid is separated out, solid is removed by filtration, and saturated Na is used₂CO₃Wash 3 times, extract 3 times with DCM and combine the organic phases. After drying over anhydrous sodium sulfate, filtration and concentration under reduced pressure, the crude product 5-1(11.12g, yield 87%) was obtained and used in the next step without further purification.

b) In a reaction flask, mixingMS (14g) and LiOH (1.45g,34.54mmol) were dissolved in DMF (70mL), stirred at room temperature for 20min, glycine methyl ester hydrochloride (2.0g,15.7mmol) was added, and after stirring for 45min, product 5-1(4.0g,18.8mmol) was added and stirred at room temperature for 18 h. After TLC monitoring the reaction was complete, the solid was removed by filtration, the filter cake was washed with EA and the filtrate was washed twice with water. Dried over anhydrous sodium sulfate, concentrated under reduced pressure to give crude product 5-2, which was used directly in the next step.

c) In a reaction flask, the product 5-2 in the previous step is dissolved in dioxane (20mL), 1M NaOH is slowly added dropwise, and after 2 hours of reaction, the hydrolysis reaction is monitored by TLC to be completed to obtain the product 5-3. 20mL of saturated NaHCO was added₃Thereafter, Fmoc-OSu dissolved in dioxane (10mL) was slowly added, stirred at room temperature overnight, monitored by TLC for completion of the reaction, made weakly acidic with 1M HCl, extracted with EA, dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (eluent:DCM: MeOH ═ 10:1) gave product 5-4(3.60g, 89% yield).

d) In a reaction flask, product 5-3(3.60g,8.0mmol), NBS (1.10g,9.6mmol), EDCI (1.85g,9.6mmol) and DCM (50mL) as a solvent were added and the mixture was reacted at room temperature for 18 hours. After completion of the reaction monitored by TLC, it was washed 3 times with water, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give the product 5-5(3.20g, yield 75%).

e) In a reaction flask, the product 5-5(3.20g,6.0mmol) was added, the solvent dioxane (40mL) and water (10mL) was added, Fmoc-Lys-OH hydrochloride (3.0g,7.2mmol) was added, triethylamine (2.0mL,15.0mmol) was added, and the reaction was stirred at room temperature for 18 hours until completion. The pH was adjusted to about 2 by the addition of an appropriate amount of 1M HCl, extracted with EA, the organic phases were combined, dried over anhydrous sodium sulfate, filtered, concentrated under reduced pressure, and subjected to column chromatography (eluent: DCM: MeOH: AcOH ═ 20:1:0.5) to give the product 5-5(3.50g, yield 75%).

f) In a reaction flask, the product 5-5 was dissolved in DCM (20mL), diethylamine (20mL) was added and reacted at room temperature for 6 hours. TLC after monitoring the reaction was complete, concentrated under reduced pressure and column chromatographed (eluent: DCM: MeOH: H)₂O30: 10:1) gave the final product as a white powder 5-7(0.55g, 37% yield).

¹H-NMR (400MHz, heavy water) δ 7.98(d, J ═ 8.2Hz,2H),7.50(d, J ═ 8.2Hz,2H),3.84(s,2H),3.71(s,1H),3.31(s,2H),3.17(t, J ═ 6.9Hz,2H),2.67(s,3H), 1.97-1.73 (m,2H), 1.58-1.45 (m,2H),1.44-1.27(m,2H).

Preparation example 6 preparation of unnatural amino acid NPOK-2

The structural formula of NPOK-2 is shown as follows:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) in a reaction flask, p-acetylphenol (2.05g,15.0mmol) and bromoacetic acid (2.50g,18.0mmol) were added, and an aqueous solution (6mL) of NaOH (1.20g,30mmol) was further added. The mixture was refluxed at 100 ℃ for 24 hours until the reaction was complete. The reaction was cooled to room temperature, acidified with 1M hydrochloric acid, precipitated solid and filtered to give the crude white product 6-1(3.32g, 113% yield) which was used in the next step without further purification.

b) In a reaction flask, crude product 6-1 from the previous step (3.32g,17.0mmol) was dissolved in DCM (50mL) and NHS (2.35g,20.4mmol) and EDCI (3.90g,20.4mmol) were added. The mixture was stirred at ambient temperature for 18 hours until the reaction was complete. Extract with DCM, combine the organic phases, dry over anhydrous sodium sulfate, filter, and concentrate under reduced pressure. Further purification by column chromatography (eluent: DCM: MeOH: AcOH ═ 20:1:0.5) afforded the product 6-2(1.67g, yield 38%).

c) In a reaction flask, add product 6-2(1.67g,5.7mmol), add solvent dioxane (20mL) and water (50mL), add Fmoc-Lys-OH hydrochloride (1.9g,4.8mmol), add triethylamine (1.7mL,12.0mmol), stir at room temperature for 18 hours until reaction is complete, add the appropriate amount of 1M HCl to adjust pH to about 2, extract with EA, combine the organic phases, add anhydrous sodium sulfate to dry, filter, concentrate under reduced pressure. The resulting crude 6-3 was dissolved directly in DCM (10mL) and diethylamine (5mL) was added. The mixture was stirred at ambient temperature for 18 hours until the reaction was complete. Concentrating under reduced pressure, and performing column chromatography (eluent: DCM: MeOH: H)₂O ═ 40:10:1) purification afforded the final product 6-4(709mg, two step yield 39%).

¹H-NMR (400MHz, heavy water) δ 7.91(d, J ═ 8.8Hz,2H),6.98(d, J ═ 8.8Hz,2H),4.60(s,2H),3.59(t, J ═ 6.4Hz,1H),3.19(t, J ═ 6.8Hz,2H),2.52(s,3H),1.87 to 1.65(m,2H),1.56 to 1.40(m,2H),1.35 to 1.15(m,2H).

Preparation example 7 preparation of unnatural amino acid NBGK-2

The structural formula of NBGK-2 is shown below:

the reaction process is shown in the following chart:

the preparation process comprises the following steps:

a) to a reaction flask, bromoacetic acid (2.10g,15.0mmol) and an aqueous solution (10mL) of NaOH (0.80g,20mmol) were added and stirred for 10 minutes. Paracetanilide (1.40g,10.0mmol) was then added and the mixture refluxed at 100 ℃ for 18 hours until the reaction was complete. The reaction was cooled to room temperature, filtered and washed with water to give 7-1(1.30g, 67% yield) as a white crude product which was used in the next step without further purification.

b) In a reaction flask, add product 7-1(1.30g,6.7mmol) and NaHCO₃(1.70g,20.1mmol) in water (20 mL). Fmoc-OSu (2.80g,8.1mmol) and DMF (20mL) were added. The mixture was stirred at 60 ℃ for 18 hours until the reaction was complete. Cooled to room temperature and extracted with EA. The water phase is kept, the pH value is adjusted to about 2 by using 1M hydrochloric acid, and then EA is used for extraction to obtain an organic phase. Adding anhydrous sodium sulfate, drying, filtering, and concentrating under reduced pressure. The product 7-2 was obtained and used in the next step without further purification.

c) In a reaction flask, the product of the previous step, 7-2 (about 6.7mmol), NHS (0.90g,8.0mmol) and EDCI (1.50g,8.0mmol) were dissolved in DMF (50 mL). The reaction mixture was stirred at room temperature for 24 hours until the reaction was complete. Water was added and extracted with DCM to obtain the organic phase. Adding anhydrous sodium sulfate, drying, filtering, and concentrating under reduced pressure. The product 7-3 was obtained and used in the next step without further purification.

d) In a reaction flask, the product of the previous step 7-3 (about 6.7mmol), Fmoc-Lys-OH hydrochloride (2.30g,5.6mmol), and triethylamine (2.0mL,14.0mmol) were added. The reaction mixture was stirred at room temperature for 3 hours until the reaction was complete. The pH was then adjusted to about 2 with 1M hydrochloric acid and extracted with EA. Adding anhydrous sodium sulfate, drying, filtering, and concentrating under reduced pressure. The product 7-4 was obtained and used in the next step without further purification.

e) In the reaction flask, the product 7-4 of the previous step was added. The solvents DCM (20mL) and diethylamine (10mL) were added. The reaction mixture was stirred at room temperature for 12 hours until the reaction was complete. Concentrating under reduced pressure, adding acetonitrile (50mL) to dissolve again, concentrating under reduced pressure, and repeating for 3 times to remove excessive diethylamine. DCM was added and slurried twice to give the final product 7-5(1.65g, 51% overall yield).

¹H-NMR (400MHz, heavy water) δ 7.71(d, J ═ 8.8Hz,2H),6.51(d, J ═ 8.8Hz,2H),3.80(s,2H),3.53(t, J ═ 6.8Hz,1H),3.09(t, J ═ 6.8Hz,2H),2.39(s,3H), 1.73-1.60 (m,2H), 1.42-1.33 (m,2H), 1.25-1.14 (m,2H).

EXAMPLE 1 construction of expression Strain expressing recombinant human IL-2(rhIL-2) with site-directed insertion of unnatural amino acids

1. Obtaining of expression plasmid NB1S3-WT of wild type recombinant human IL-2

The precursor protein sequence of homo sapiens IL-2 (GenBank ID: CAA25292.1) was obtained from the National Center for Biotechnology Information (NCBI) as shown in SEQ ID NO: 1. The N-terminus of the precursor sequence contains a 20 amino acid signal peptide sequence which is cleaved during processing and maturation of the IL-2 protein molecule, thus removing the signal peptide sequence to yield the mature homo sapiens IL-2 protein sequence (SEQ ID NO: 2). According to literature reports (Liang S.M et al. Journal of Biological Chemistry,261(1):334-337, 1986), mature homo sapiens IL-2 contains 3 Cys cysteines in its protein sequence, wherein the two Cys at positions 58 and 105 form disulfide bonds, which are important for the Biological activity of homo sapiens IL-2. The Cys at the position 125 does not participate in the formation of disulfide bonds, but interferes with the formation of normal disulfide bonds in the renaturation process of the protein inclusion body of the recombinant homo sapiens IL-2, so that the Cys at the position 125 can be mutated into serine Ser, and the efficiency of renaturation is improved without obviously influencing the activity of the serine Ser. Meanwhile, in order to express the recombinant protein in E.coli, methionine Met is added to the N-terminus of the protein sequence for initiating the translation of the protein, thereby obtaining the mature protein sequence of recombinant human IL-2 (SEQ ID NO: 3). The gene sequence (SEQ ID NO:4) of the coding recombinant human IL-2 is obtained through the reverse translation process of amino acid and codon optimization, and the coding gene of the recombinant human IL-2 is obtained through whole-gene synthesis. Then the wild type recombinant human IL-2 expression plasmid NB1S3-WT (see FIG. 1) is obtained by connecting the wild type recombinant human IL-2 expression plasmid into an NB1S3 expression vector (the expression vector is modified from a commercial vector pET-21a, and an ampicillin resistance gene screening marker of the expression vector is replaced by a spectinomycin resistance gene amplified from a commercial vector pCDF-duet1 by a PCR mode), and the sequence is shown as SEQ ID NO: 5.

SEQ ID NO:1

MYRMQLLSCIALSLALVTNSAPTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFCQSIISTLT

SEQ ID NO:2

APTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFCQSIISTLT

SEQ ID NO:3

MAPTSSSTKKTQLQLEHLLLDLQMILNGINNYKNPKLTRMLTFKFYMPKKATELKHLQCLEEELKPLEEVLNLAQSKNFHLRPRDLISNINVIVLELKGSETTFMCEYADETATIVEFLNRWITFSQSIISTLT

SEQ ID NO:4

ATGGCGCCTACATCCAGCTCGACCAAAAAGACGCAGCTGCAACTGGAACACCTGCTCCTGGATCTGCAAATGATTCTTAACGGTATCAATAACTACAAAAATCCGAAACTGACCCGTATGCTGACGTTTAAATTCTATATGCCAAAGAAAGCGACCGAGCTGAAACATCTGCAGTGCCTGGAAGAGGAACTGAAACCGCTGGAGGAAGTTTTGAACCTGGCTCAGTCTAAAAACTTTCACCTGCGCCCTCGTGACCTGATTTCCAATATCAACGTGATTGTTCTGGAACTGAAAGGCTCTGAAACCACGTTTATGTGCGAGTACGCCGATGAAACCGCCACGATTGTGGAATTTCTGAATCGCTGGATCACCTTCTCCCAGAGCATTATTAGCACGCTGACCTAA

SEQ ID NO:5

GGCGAGAAAGGAAGGGAAGAAAGCGAAAGGAGCGGGCGCTAGGGCGCTGGCAAGTGTAGCGGTCACGCTGCGCGTAACCACCACACCCGCCGCGCTTAATGCGCCGCTACAGGGCGCGTCCCATTCGCCAATCCGGATATAGTTCCTCCTTTCAGCAAAAAACCCCTCAAGACCCGTTTAGAGGCCCCAAGGGGTTATGCTAGTTATTGCTCAGCGGTGGCAGCAGCCAACTCAGCTTCCTTTCGGGCTTTGTTAGCAGCCGGATCTCAGTGGTGGTGGTGGTGGTGCTCGAGTTAGGTCAGCGTGCTAATAATGCTCTGGGAGAAGGTGATCCAGCGATTCAGAAATTCCACAATCGTGGCGGTTTCATCGGCGTACTCGCACATAAACGTGGTTTCAGAGCCTTTCAGTTCCAGAACAATCACGTTGATATTGGAAATCAGGTCACGAGGGCGCAGGTGAAAGTTTTTAGACTGAGCCAGGTTCAAAACTTCCTCCAGCGGTTTCAGTTCCTCTTCCAGGCACTGCAGATGTTTCAGCTCGGTCGCTTTCTTTGGCATATAGAATTTAAACGTCAGCATACGGGTCAGTTTCGGATTTTTGTAGTTATTGATACCGTTAAGAATCATTTGCAGATCCAGGAGCAGGTGTTCCAGTTGCAGCTGCGTCTTTTTGGTCGAGCTGGATGTAGGCGCCATATGTATATCTCCTTCTTAAAGTTAAACAAAATTATTTCTAGAGGGGAATTGTTATCCGCTCACAATTCCCCTATAGTGAGTCGTATTAATTTCGCGGGATCGAGATCTCGATCCTCTACGCCGGACGCATCGTGGCCGGCATCACCGGCGCCACAGGTGCGGTTGCTGGCGCCTATATCGCCGACATCACCGATGGGGAAGATCGGGCTCGCCACTTCGGGCTCATGAGCGCTTGTTTCGGCGTGGGTATGGTGGCAGGCCCCGTGGCCGGGGGACTGTTGGGCGCCATCTCCTTGCATGCACCATTCCTTGCGGCGGCGGTGCTCAACGGCCTCAACCTACTACTGGGCTGCTTCCTAATGCAGGAGTCGCATAAGGGAGAGCGTCGAGATCCCGGACACCATCGAATGGCGCAAAACCTTTCGCGGTATGGCATGATAGCGCCCGGAAGAGAGTCAATTCAGGGTGGTGAATGTGAAACCAGTAACGTTATACGATGTCGCAGAGTATGCCGGTGTCTCTTATCAGACCGTTTCCCGCGTGGTGAACCAGGCCAGCCACGTTTCTGCGAAACGCGGGAAAAAGTGGAAGCGGCGATGGCGGAGCTGAATTACATTCCCAACCGCGTGGCACAACAACTGGCGGGCAAACAGTCGTTGCTGATTGGCGTTGCCACCTCCAGTCTGGCCCTGCACGCGCCGTCGCAAATTGTCGCGGCGATTAAATCTCGCGCCGATCAACTGGGTGCCAGCGTGGTGGTGTCGATGGTAGAACGAAGCGGCGTCGAAGCCTGTAAAGCGGCGGTGCACAATCTTCTCGCGCAACGCGTCAGTGGGCTGATCATTAACTATCCGCTGGATGACCAGGATGCCATTGCTGTGGAAGCTGCCTGCACTAATGTTCCGGCGTTATTTCTTGATGTCTCTGACCAGACACCCATCAACAGTATTATTTTCTCCCATGAAGACGGTACGCGACTGGGCGTGGAGCATCTGGTCGCATTGGGTCACCAGCAAATCGCGCTGTTAGCGGGCCCATTAAGTTCTGTCTCGGCGCGTCTGCGTCTGGCTGGCTGGCATAAATATCTCACTCGCAATCAAATTCAGCCGATAGCGGAACGGGAAGGCGACTGGAGTGCCATGTCCGGTTTTCAACAAACCATGCAAATGCTGAATGAGGGCATCGTTCCCACTGCGATGCTGGTTGCCAACGATCAGATGGCGCTGGGCGCAATGCGCGCCATTACCGAGTCCGGGCTGCGCGTTGGTGCGGATATCTCGGTAGTGGGATACGACGATACCGAAGACAGCTCATGTTATATCCCGCCGTTAACCACCATCAAACAGGATTTTCGCCTGCTGGGGCAAACCAGCGTGGACCGCTTGCTGCAACTCTCTCAGGGCCAGGCGGTGAAGGGCAATCAGCTGTTGCCCGTCTCACTGGTGAAAAGAAAAACCACCCTGGCGCCCAATACGCAAACCGCCTCTCCCCGCGCGTTGGCCGATTCATTAATGCAGCTGGCACGACAGGTTTCCCGACTGGAAAGCGGGCAGTGAGCGCAACGCAATTAATGTAAGTTAGCTCACTCATTAGGCACCGGGATCTCGACCGATGCCCTTGAGAGCCTTCAACCCAGTCAGCTCCTTCCGGTGGGCGCGGGGCATGACTATCGTCGCCGCACTTATGAAGCTTCTATCGTCGCCGCACTTATGACTGTCTTCTTTATCATGCAACTCGTAGGACAGGTGCCGGCAGCGCTCTGGGTCATTTTCGGCGAGGACCGCTTTCGCTGGAGCGCGACGATGATCGGCCTGTCGCTTGCGGTATTCGGAATCTTGCACGCCCTCGCTCAAGCCTTCGTCACTGGTCCCGCCACCAAACGTTTCGGCGAGAAGCAGGCCATTATCGCCGGCATGGCGGCCCCACGGGTGCGCATGATCGTGCTCCTGTCGTTGAGGACCCGGCTAGGCTGGCGGGGTTGCCTTACTGGTTAGCAGAATGAATCACCGATACGCGAGCGAACGTGAAGCGACTGCTGCTGCAAAACGTCTGCGACCTGAGCAACAACATGAATGGTCTTCGGTTTCCGTGTTTCGTAAAGTCTGGAAACGCGGAAGTCAGCGCCCTGCACCATTATGTTCCGGATCTGCATCGCAGGATGCTGCTGGCTACCCTGTGGAACACCTACATCTGTATTAACGAAGCGCTGGCATTGACCCTGAGTGATTTTTCTCTGGTCCCGCCGCATCCATACCGCCAGTTGTTTACCCTCACAACGTTCCAGTAACCGGGCATGTTCATCATCAGTAACCCGTATCGTGAGCATCCTCTCTCGTTTCATCGGTATCATTACCCCCATGAACAGAAATCCCCCTTACACGGAGGCATCAGTGACCAAACAGGAAAAAACCGCCCTTAACATGGCCCGCTTTATCAGAAGCCAGACATTAACGCTTCTGGAGAAACTCAACGAGCTGGACGCGGATGAACAGGCAGACATCTGTGAATCGCTTCACGACCACGCTGATGAGCTTTACCGCAGCTGCCTCGCGCGTTTCGGTGATGACGGTGAAAACCTCTGACACATGCAGCTCCCGGAGACGGTCACAGCTTGTCTGTAAGCGGATGCCGGGAGCAGACAAGCCCGTCAGGGCGCGTCAGCGGGTGTTGGCGGGTGTCGGGGCGCAGCCATGACCCAGTCACGTAGCGATAGCGGAGTGTATACTGGCTTAACTATGCGGCATCAGAGCAGATTGTACTGAGAGTGCACCATATATGCGGTGTGAAATACCGCACAGATGCGTAAGGAGAAAATACCGCATCAGGCGCTCTTCCGCTTCCTCGCTCACTGACTCGCTGCGCTCGGTCGTTCGGCTGCGGCGAGCGGTATCAGCTCACTCAAAGGCGGTAATACGGTTATCCACAGAATCAGGGGATAACGCAGGAAAGAACATGTGAGCAAAAGGCCAGCAAAAGGCCAGGAACCGTAAAAAGGCCGCGTTGCTGGCGTTTTTCCATAGGCTCCGCCCCCCTGACGAGCATCACAAAAATCGACGCTCAAGTCAGAGGTGGCGAAACCCGACAGGACTATAAAGATACCAGGCGTTTCCCCCTGGAAGCTCCCTCGTGCGCTCTCCTGTTCCGACCCTGCCGCTTACCGGATACCTGTCCGCCTTTCTCCCTTCGGGAAGCGTGGCGCTTTCTCATAGCTCACGCTGTAGGTATCTCAGTTCGGTGTAGGTCGTTCGCTCCAAGCTGGGCTGTGTGCACGAACCCCCCGTTCAGCCCGACCGCTGCGCCTTATCCGGTAACTATCGTCTTGAGTCCAACCCGGTAAGACACGACTTATCGCCACTGGCAGCAGCCACTGGTAACAGGATTAGCAGAGCGAGGTATGTAGGCGGTGCTACAGAGTTCTTGAAGTGGTGGCCTAACTACGGCTACACTAGAAGGACAGTATTTGGTATCTGCGCTCTGCTGAAGCCAGTTACCTTCGGAAAAAGAGTTGGTAGCTCTTGATCCGGCAAACAAACCACCGCTGGTAGCGGTGGTTTTTTTGTTTGCAAGCAGCAGATTACGCGCAGAAAAAAAGGATCTCAAGAAGATCCTTTGATCTTTTCTACGGGGTCTGACGCTCAGTGGAACGAAAACTCACGTTAAGGGACTGCAGCTATTTGTTTATTTTTCTAAATACATTCAAATATGTATCCGCTCATGAGACAATAACCCTGATAAATGCTTCAATAATATTGAAAAAGGAAGAGTATGAGGGAAGCGGTGATCGCCGAAGTATCGACTCAACTATCAGAGGTAGTTGGCGTCATCGAGCGCCATCTCGAACCGACGTTGCTGGCCGTACATTTGTACGGCTCCGCAGTGGATGGCGGCCTGAAGCCACACAGTGATATTGATTTGCTGGTTACGGTGACCGTAAGGCTTGATGAAACAACGCGGCGAGCTTTGATCAACGACCTTTTGGAAACTTCGGCTTCCCCTGGAGAGAGCGAGATTCTCCGCGCTGTAGAAGTCACCATTGTTGTGCACGACGACATCATTCCGTGGCGTTATCCAGCTAAGCGCGAACTGCAATTTGGAGAATGGCAGCGCAATGACATTCTTGCAGGTATCTTCGAGCCAGCCACGATCGACATTGATCTGGCTATCTTGCTGACAAAAGCAAGAGAACATAGCGTTGCCTTGGTAGGTCCAGCGGCGGAGGAACTCTTTGATCCGGTTCCTGAACAGGATCTATTTGAGGCGCTAAATGAAACCTTAACGCTATGGAACTCGCCGCCCGACTGGGCTGGCGATGAGCGAAATGTAGTGCTTACGTTGTCCCGCATTTGGTACAGCGCAGTAACCGGCAAAATCGCGCCGAAGGATGTCGCTGCCGACTGGGCAATGGAGCGCCTGCCGGCCCAGTATCAGCCCGTCATACTTGAAGCTAGACAGGCTTATCTTGGACAAGAAGAAGATCGCTTGGCCTCGCGCGCAGATCAGTTGGAAGAATTTGTCCACTACGTGAAAGGCGAGATCACCAAGGTAGTCGGCAAATAATGTCTAACAATTCGTTCAAGCCGAGGGGCCGCAAGATCCGGCCACGATGACCCGGTCGTCGGTTCAGGGCAGGGTCGTTAAATAGCCGCTTATGTCTATTGCTGGTTTACCGGTTTATTGACTACCGGAAGCAGTGTGACCGT

2. Site-directed mutagenesis site selection

Selecting P34, K35, T37, R38, L40, T41, F42, K43, F44, Y45, E61, E62, K64, P65, E67, E68, N71, L72 and Y107 of SEQ ID NO 2 as specific sites to carry out point mutation, and taking the mutant IL-2 as a raw material and carrying out site-directed modification on the mutant IL-2.

3. Primer design for site-directed mutagenesis and construction of mutagenesis vector

Primers capable of mutating codons encoding the amino acids into amber codons are designed aiming at P34, K35, T37, R38, L40, T41, F42, K43, F44, Y45, E61, E62, K64, P65, E67, E68, N71, L72 and Y107 of SEQ ID NO 2, and specific primers are shown in Table 1.

TABLE 1 mutant primer List

A linearized DNA plasmid is obtained by double digestion of the plasmid NB1S3-WT with restriction endonucleases XbaI and XhoI, a high fidelity DNA polymerase (purchased from Takara under the accession number R045A) is used as a template, primers R at various sites are paired with primers XbaI-F of Table 1, primers F at various sites are paired with primers XbaI-R of Table 1, a mutant gene of which amino acid codons at several sites of K35, T41, K43, Y45, E61, K64 and P65 of IL-2 are mutated into an amber stop codon is obtained by PCR amplification and overlapping PCR method (for example, a mutant gene of which downstream site is mutated by PCR amplification with the linearized plasmid NB1S3-WT as a template, XbaI-F and T41-R as primer pairs is used as a downstream site of the linearized plasmid NB1S 3-WT) to obtain an upstream fragment of the T41 site mutation, a downstream site is amplified with the linearized plasmid NB1S3-WT as a template, the XhoI-R and the T41-F as primers, and a downstream site is mutated by PCR amplification fragment of the T41 and a downstream site upstream fragment of the linearized plasmid NB 3638 is obtained by PCR amplification method The segment is taken as a template, XbaI-F and XhoI-R are taken as primer pairs to carry out overlapping PCR amplification to obtain a full-length gene with a T41 site mutation, and then the obtained mutant gene is respectively replaced by a fragment between two enzyme cutting sites of XbaI and XhoI of an NB1S3-WT plasmid by using a high-fidelity DNA assembly cloning kit (purchased from NEB and with the product number of E5520S) according to the instruction operation to construct 7 expression plasmids of NB1S3-K35, NB1S3-T41, NB1S3-K43, NB1S3-Y45, NB1S3-E61, NB1S3-K64 and NB1S3-P65, and the success of mutation is verified by sequencing.

4. Construction of site-directed mutant rhIL-2 expression strains

The plasmid pUltra structure described in the reference (Chatterjee, A. et al, Biochemistry,52(10),1828-1837,2013) was constructed by obtaining a gene encoding tRNA and tRNA synthetase (wild type Gum methane coccus pyrrilysin synthetase and the corresponding tRNA) which specifically recognizes the carbonyl-terminated lysine analog of the structure of the formula (I) of the present invention and a chloramphenicol resistance gene (SEQ ID NO:46) by total gene synthesis, amplifying a DNA fragment (SEQ ID NO:47) containing the replication initiation site of CloDF13 from a commercial vector pCDF-duet1 by PCR amplification, and further subcloning and ligating the two DNA fragments by using a high fidelity DNA assembly cloning kit to obtain a helper plasmid NB1W (see FIG. 2, hereinafter referred to as helper plasmid), which was screened for chloramphenicol resistance. Coli BL21(DE3) was co-transformed with the helper plasmid and the expression plasmid obtained in step 3 (spectinomycin resistance), respectively, and double-positive strains (double-positive strains mean strains that simultaneously acquired spectinomycin resistance and chloramphenicol resistance) were selected on spectinomycin-resistant and chloramphenicol-resistant plates: rhIL2-K35-BL21, rhIL2-T41-BL21, rhIL2-K43-BL21, rhIL2-Y45-BL21, rhIL2-E61-BL21, rhIL2-K64-BL21 and rhIL2-P65-BL 21.

The DNA fragment comprising the wild-type Gum methane coccus pyrrilysin synthetase encoding gene, the corresponding tRNA encoding gene and the chloramphenicol resistance gene (SEQ ID NO:46) is as follows:

CCTTATGCGACTCCCTGCATTAGGGAGCTGTTGACAATTAATCATCGGCTCGTATAATGTGTGGAATTGTGAGCGGATAACAATTTCACAAAGGAGGTCATATGGATAAAAAGCCTCTGAACACTCTGATTTCTGCGACCGGTCTGTGGATGTCCCGCACCGGCACCATCCACAAAATCAAACACCATGAAGTTAGCCGTTCCAAAATCTACATTGAAATGGCTTGCGGCGATCACCTGGTTGTCAACAACTCCCGTTCTTCTCGTACCGCTCGCGCACTGCGCCACCACAAATATCGCAAAACCTGCAAACGTTGCCGTGTTAGCGATGAAGATCTGAACAAATTCCTGACCAAAGCTAACGAGGATCAGACCTCCGTAAAAGTGAAGGTAGTAAGCGCTCCGACCCGTACTAAAAAGGCTATGCCAAAAAGCGTGGCCCGTGCCCCGAAACCTCTGGAAAACACCGAGGCGGCTCAGGCTCAACCATCCGGTTCTAAATTTTCTCCGGCGATCCCAGTGTCCACCCAAGAATCTGTTTCCGTACCAGCAAGCGTGTCTACCAGCATTAGCAGCATTTCTACCGGTGCTACCGCTTCTGCGCTGGTAAAAGGTAACACTAACCCGATTACTAGCATGTCTGCACCGGTACAGGCAAGCGCCCCAGCTCTGACTAAATCCCAGACGGACCGTCTGGAGGTGCTGCTGAACCCAAAGGATGAAATCTCTCTGAACAGCGGCAAGCCTTTCCGTGAGCTGGAAAGCGAGCTGCTGTCTCGTCGTAAAAAGGATCTGCAACAGATCTACGCTGAGGAACGCGAGAACTATCTGGGTAAGCTGGAGCGCGAAATTACTCGCTTCTTCGTGGATCGCGGTTTCCTGGAGATCAAATCTCCGATTCTGATTCCGCTGGAATACATTGAACGTATGGGCATCGATAATGATACCGAACTGTCTAAACAGATCTTCCGTGTGGATAAAAACTTCTGTCTGCGTCCGATGCTGGCCCCGAACCTGTACAACTATCTGCGTAAACTGGACCGTGCCCTGCCGGACCCGATCAAAATTTTCGAGATCGGTCCTTGCTACCGTAAAGAGTCCGACGGTAAAGAGCACCTGGAAGAATTCACCATGCTGAACTTTTGCCAGATGGGTAGCGGTTGCACGCGTGAAAACCTGGAATCCATTATCACCGACTTCCTGAATCACCTGGGTATCGATTTCAAAATTGTTGGTGACAGCTGTATGGTGTACGGCGATACGCTGGATGTTATGCACGGCGATCTGGAGCTGTCTTCCGCAGTAGTGGGCCCAATCCCGCTGGATCGTGAGTGGGGTATCGACAAACCTTGGATCGGTGCGGGTTTTGGTCTGGAGCGTCTGCTGAAAGTAAAACACGACTTCAAGAACATCAAACGTGCTGCACGTTCCGAGTCCTATTACAATGGTATTTCTACTAACCTGTAACTAGTGTCTCCAGCTTGGCTGTTTTGGCGGATGAGAGAAGATTTTCAGCCTGATACAGATTAAATCAGAACGCAGAAGCGGTCTGATAAAACAGAATTTGCCTGGCGGCAGTAGCGCGGTGGTCCCACCTGACCCCATGCCGAACTCAGAAGTGAGCACTGCAGCGGCTAACTAAGCGGCCTGCTGACTTTCTCGCCGATCAAAAGGCATTTTGCTATTAAGGGATTGACGAGGGCGTATCTGCGCAGTAAGATGCGCCCCGCATTGGAAACCTGATCATGTAGATCGAATGGACTCTAAATCCGTTCAGCCGGGTTAGATTCCCGGGGTTTCCGCCAAATTCGAAAAGCCTGCTCAACGAGCAGGCTTTTTTGCATCTCGAGCAGCTCAGGGTCGAATTTGCTTTCGAATTTCTGCCATTCATCCGCTTATTATCACTTATTCAGGCGTAGCAACCAGGCGTTTAAGGGCACCAATAACTGCCTTAAAAAAATTACGCCCCGCCCTGCCACTCATCGCAGTACTGTTGTAATTCATTAAGCATTCTGCCGACATGGAAGCCATCACAAACGGCATGATGAACCTGAATCGCCAGCGGCATCAGCACCTTGTCGCCTTGCGTATAATATTTGCCCATGGTGAAAACGGGGGCGAAGAAGTTGTCCATATTGGCCACGTTTAAATCAAAACTGGTGAAACTCACCCAGGGATTGGCTGAGACGAAAAACATATTCTCAATAAACCCTTTAGGGAAATAGGCCAGGTTTTCACCGTAACACGCCACATCTTGCGAATATATGTGTAGAAACTGCCGGAAATCGTCGTGGTATTCACTCCAGAGCGATGAAAACGTTTCAGTTTGCTCATGGAAAACGGTGTAACAAGGGTGAACACTATCCCATATCACCAGCTCACCGTCTTTCATTGCCATACGGAATTCCGGATGAGCATTCATCAGGCGGGCAAGAATGTGAATAAAGGCCGGATAAAACTTGTGCTTATTTTTCTTTACGGTCTTTAAAAAGGCCGTAATATCCAGCTGAACGGTCTGGTTATAGGTACATTGAGCAACTGACTGAAATGCCTCAAAATGTTCTTTACGATGCCATTGGGATATATCAACGGTGGTATATCCAGTGATTTTTTTCTCCATTTTAGCTTCCTTAGCTCCTGAAAATCTCGATAACTCAAAAAATACGCCCGGTAGTGATCTTATTTCATTATGGTGAAAGTTGGAACCTCTTACGTGCCGATCAACGTCTCATTTTCGCCAAAAGTTGGCCCAGGGCTTCCCGGTATCAACAGGGACACCAGGATTTATTTATTCTGCGAAGTGATCTTCCGTCACAGGTATTTATTCGGCGCAAAGTGCGTCGGGTGATGCTGCCAACTTACTGATTTAGTGTATGATGGTGTTTTTGAGGTGCTCCAGTGGCTTCTGTTTCTATCAGCTGTCCCTCCTGTTCAGCTACTGACGGGGTGGTGCGTAACGGCAAAAGCACCGCCGGACATCAGCGCGCGCTGCGGACAC

the DNA fragment of the replication initiation site of CloDF13 (SEQ ID NO:47) is as follows:

CGGACATCAGCGCGCGCTGCGGACACATACAAAGTTACCCACAGATTCCGTGGATAAGCAGGGGACTAACATGTGAGGCAAAACAGCAGGGCCGCGCCGGTGGCGTTTTTCCATAGGCTCCGCCCTCCTGCCAGAGTTCACATAAACAGACGCTTTTCCGGTGCATCTGTGGGAGCCGTGAGGCTCAACCATGAATCTGACAGTACGGGCGAAACCCGACAGGACTTAAAGATCCCCACCGTTTCCGGCGGGTCGCTCCCTCTTGCGCTCTCCTGTTCCGACCCTGCCGTTTACCGGATACCTGTTCCGCCTTTCTCCCTTACGGGAAGTGTGGCGCTTTCTCATAGCTCACACACTGGTATCTCGGCTCGGTGTAGGTCGTTCGCTCCAAGCTGGGCTGTAAGCAAGAACTCCCCGTTCAGCCCGACTGCTGCGCCTTATCCGGTAACTGTTCACTTGAGTCCAACCCGGAAAAGCACGGTAAAACGCCACTGGCAGCAGCCATTGGTAACTGGGAGTTCGCAGAGGATTTGTTTAGCTAAACACGCGGTTGCTCTTGAAGTGTGCGCCAAAGTCCGGCTACACTGGAAGGACAGATTTGGTTGCTGTGCTCTGCGAAAGCCAGTTACCACGGTTAAGCAGTTCCCCAACTGACTTAACCTTCGATCAAACCACCTCCCCAGGTGGTTTTTTCGTTTACAGGGCAAAAGATTACGCGCAGAAAAAAAGGATCTCAAGAAGATCCTTTGATCTTTTCTACTGAACCGCTCTAGATTTCAGTGCAATTTATCTCTTCAAATGTAGCACCTGAAGTCAGCCCCATACGATATAAGTTGTAATTCTCATGTTAGTCATGCCCCGCGCCCACCGGAAGGAGCTGACTGGGTTGAAGGCTCTCAAGGGCATCGGTCGAGATCCCGGTGCCTAATGAGTGAGCTAACTTACATTAATTGCGTTGCGCTCACTGCCCGCTTTCCAGTCGGGAAACCTGTCGTGCCAGCTGCATTAATGAATCGGCCAACGCGCGGGGAGAGGCGGTTTGCGTATTGGGCGCCAGGGTGGTTTTTCTTTTCACCAGTGAGACGGGCAACAGCTGATTGCCCTTCACCGCCTGGCCCTGAGAGAGTTGCAGCAAGCGGTCCACGCTGGTTTGCCCCAGCAGGCGAAAATCCTGTTTGATGGTGGTTAACGGCGGGATATAACATGAGCTGTCTTCGGTATCGTCGTATCCCACTACCGAGATGTCCGCACCAACGCGCAGCCCGGACTCGGTAATGGCGCGCATTGCGCCCAGCGCCATCTGATCGTTGGCAACCAGCATCGCAGTGGGAACGATGCCCTCATTCAGCATTTGCATGGTTTGTTGAAAACCGGACATGGCACTCCAGTCGCCTTCCCGTTCCGCTATCGGCTGAATTTGATTGCGAGTGAGATATTTATGCCAGCCAGCCAGACGCAGACGCGCCGAGACAGAACTTAATGGGCCCGCTAACAGCGCGATTTGCTGGTGACCCAATGCGACCAGATGCTCCACGCCCAGTCGCGTACCGTCTTCATGGGAGAAAATAATACTGTTGATGGGTGTCTGGTCAGAGACATCAAGAAATAACGCCGGAACATTAGTGCAGGCAGCTTCCACAGCAATGGCATCCTGGTCATCCAGCGGATAGTTAATGATCAGCCCACTGACGCGTTGCGCGAGAAGATTGTGCACCGCCGCTTTACAGGCTTCGACGCCGCTTCGTTCTACCATCGACACCACCACGCTGGCACCCAGTTGATCGGCGCGAGATTTAATCGCCGCGACAATTTGCGACGGCGCGTGCAGGGCCAGACTGGAGGTGGCAACGCCAATCAGCAACGACTGTTTGCCCGCCAGTTGTTGTGCCACGCGGTTGGGAATGTAATTCAGCTCCGCCATCGCCGCTTCCACTTTTTCCCGCGTTTTCGCAGAAACGTGGCTGGCCTGGTTCACCACGCGGGAAACGGTCTGATAAGAGACACCGGCATACTCTGCGACATCGTATAACGTTACTGGTTTCACATTCACCACCCTGAATTGACTCTCTTCCGGGCGCTATCATGCCATACCGCGAAAGGTTTTGCGCCATTCGATGGTGTCCGGGATCTCGACGCTCTCCCTTATGCGACTC

EXAMPLE 2 expression and purification of rhIL-2 by site-directed mutagenesis with insertion of unnatural amino acids

1. Expression of unnatural amino acid incorporation of mutant rhIL-2

The 7 expression strains obtained in example 1, rhIL2-K35-BL21, rhIL2-T41-BL21, rhIL2-K43-BL21, rhIL2-Y45-BL21, rhIL2-E61-BL21, rhIL2-K64-BL21 and rhIL2-P65-BL21 were inoculated into LB medium (yeast extract 5g/L, tryptone 10g/L, NaCl 10g/L, containing 100mg/L spectinomycin and 37.5mg/L chloramphenicol), respectively, cultured at 37 ℃ for 5-8 hours, and then secondary expanded (the composition of the medium is the same as before) to OD (bacterial liquid)₆₀₀The concentration is 2.0 +/-0.2, and secondary seed liquid is obtained.

The secondary seed liquid was inoculated into a fermentation medium for fermentation culture in a 5L fermentor in a culture volume of 2L in a2 XYT medium (16 g/L yeast extract, 10g/L tryptone, 5g/L NaCl), and the inoculum size: 5% (v/v); the culture temperature is as follows: 37 ℃; and (3) pH control: 6.90 +/-0.05, and automatically adding ammonia water or H when necessary₃PO₄(ii) a And (4) DO control: 30%, DO-related speed; bacterial liquid OD₆₀₀When the concentration of the mixture is 20.0 +/-2.0, IPTG and the unnatural amino acid NBOK obtained in the preparation example 1 are added, the final concentration is 1mM, and simultaneously 50% glycerol is fed at a feeding speed of 0.6 +/-0.1 mL/min; after induction expression for 5-6 hours, the cells were collected. The SDS-PAGE electrophoresis of each strain is shown in FIG. 3.

2. Separation and extraction of mutant rhIL-2

Resuspending the collected thallus with buffer solution (25mM Tris, 6mM EDTA, 1mM DTT, pH8.0), adding 1% DNase (1mg/mL) and 0.5% PMSF, mixing, and homogenizing at 50-80MPa for 3 times with ultra-high pressure homogenizer; centrifuging the homogeneous solution at 10000rpm for 20min, and collecting the lower layer inclusion body crude body.

The obtained inclusion body crude body was washed twice with a washing buffer (20mM Tris-HCl, 100mM NaCl, 2% TritonX-100, pH8.0), and then washed once with ultrapure water to obtain a purified inclusion body.

The purified inclusion bodies were dissolved in a denaturation buffer (20mM Tris-HCl, 100mM NaCl, 6M guanidine hydrochloride, 1mM DTT, pH8.0), centrifuged at 10000rpm after 30min, and the supernatant was collected as a denatured protein solution. Adding renaturation buffer solution (20mM Tris-HCl, 100mM NaCl, pH8.0) with 4 times volume into the collected denatured protein solution, fully stirring, standing for 12h, centrifuging at 10000rpm, and collecting supernatant to obtain the renaturation protein solution.

Concentrating renaturated protein solution to the original volume 1/4 by using an ultrafiltration membrane package (Millipore, Biomax-5) with the molecular weight cutoff of 5kDa, changing the solution by using a replacement buffer solution (20mM Tris-HCl, pH8.0) until the conductance is about 2ms/cm, further concentrating until the protein concentration is about 0.5-1mg/mL, centrifuging at 10000rpm, collecting supernatant to obtain mutant rhIL-2 crude protein rhIL2-K35, rhIL2-T41, rhIL2-K43, rhIL2-Y45, rhIL2-E61, rhIL2-K64 and rhIL2-P65, and directly using the supernatant for subsequent PEG coupling.

Example 3 site-directed conjugation of PEG to site-directed mutagenesis of rhIL-2 inserted with the unnatural amino acid NBOK

The site-specific coupling of the PEG and the rhIL-2 with site-specific mutation inserted into the unnatural amino acid is shown as the synthetic route of formula 2 (wherein P is₁To P₂In the N-terminal to C-terminal direction of the amino acid sequence).

Taking the example of coupling rhIL-2 by 30KD aminoxy PEG (i.e. hydroxylamine PEG) oximation reaction, the coupling reaction is performed as follows: before the coupling reaction, the target protein obtained above was adjusted to pH4.0 with 2M acetic acid solution, and the protein concentration was adjusted to about 1mg/ml with 20mM sodium acetate buffer (pH4.0) according to 1: 15 (molar ratio, protein: aminoxy PEG) was added to 30KD aminoxy PEG solid (purchased from Kyoto KeyTech Co., Ltd.), sufficiently shaken and dissolved to obtain a clear and transparent solution, and then the reaction solution was sealed and shaken in a constant temperature shaker (25 ℃ C., 100rpm) for reaction. After 48h the coupling was analysed using RP-HPLC, see FIGS. 4A and 4B. The results show that only weak rhIL-2 peaks are present in FIG. 4B, indicating that 7 target proteins achieve PEG coupling, and the coupling rate (100% -the residual rhIL-2 concentration after coupling/rhIL-2 concentration at zero coupling reaction x 100%) is greater than 95%, further indicating that the above-mentioned unnatural amino acid NBOK is inserted into the target protein.

The mutant rhIL-2 protein after coupling with PEG is respectively called as: 30KD PEG-rhIL2-K35, 30KD PEG-rhIL2-T41, 30KD PEG-rhIL2-K43, 30KD PEG-rhIL2-Y45, 30KD PEG-rhIL2-E61, 30KD PEG-rhIL2-K64 and 30KD PEG-rhIL 2-P65.

RP-HPLC analysis conditions were as follows:

mobile phase A (0.1% TFA-H)₂O)；

Mobile phase B (0.1% TFA-ACN).

Example 4 purification of 30kD PEG-rhIL2 with site-directed modification

Chromatography medium: capto MMC; and (3) an equilibrium buffer: 20mM sodium citrate buffer (pH 3.0), elution buffer: 20mM sodium citrate buffer-1M NaCl (pH 7.8).

The purification process specifically comprises: the coupling reaction liquid of 30KD PEG-rhIL2-K35, 30KD PEG-rhIL2-T41, 30KD PEG-rhIL2-K43, 30KD PEG-rhIL2-Y45, 30KD PEG-rhIL2-E61, 30KD PEG-rhIL2-K64 and 30KD PEG-rhIL2-P65 obtained in the embodiment 3 are respectively adjusted with an equilibrium buffer solution to have the pH value of 3.0 +/-0.2 and the conductivity of less than or equal to 5ms/cm, the coupling reaction liquid is loaded to Capto MMC, elution is carried out by using an elution buffer solution (0-100% of eluent, 20CV), and the target protein component is collected, thus obtaining the target protein sample with the purity of about 95%. Taking 30KD PEG-rhIL2-Y45 as an example, typical RP-HPLC patterns of the purified conjugate 30KD PEG-rhIL2-Y45 and the rhIL2-Y45 before conjugation are shown in figure 5. The purification results for other protein samples were similar.

Example 5 in vitro Activity evaluation of site-directed modification of 30KD PEG-rhIL2 (STAT5 phosphorylation experiment)

The method adopts two cell strains, wherein a mouse CTLL-2 cell is a cell strain containing IL-2R alpha beta gamma, a human YT cell is a cell strain containing IL-2R beta gamma, and rhIL-2 is combined with the IL-2R on the cell surface to activate a JAK-STAT signal channel. The modification sites of the samples are different, the relative activities of the samples on the two cells are different, and the ratio change percentage of the YT cells/CTLL-2 cells EC50 is lower, so that the effect of the samples on promoting the immune function is better; on the contrary, the better the effect of suppressing the immune function.

The specific process is as follows: mouse CTLL-2 cells (purchased from American Type Culture Collection) and human YT cells were cultured in respective media (CTLL-2 cell Culture medium: RPMI 1640+ 10% FBS +400IU/mL rhIL-2, 2mM L-glutamine, 1mM sodium pyruvate; YT cell Culture medium: RPMI 1640+ 10% FBS +1mM Non-Essential Amino Acids Solution (purchased from Gibco, Cat. No. 11140050)) at 37 ℃ in 5% carbon dioxide to a sufficient amount, starved for 4h before detection, and then adjusted to a cell density of 1 × 10⁶cells/mL are ready for use. 30KD PEG-rhIL2-K35, 30KD PEG-rhIL2-T41, 30KD PEG-rhIL2-Y45, 30KD PEG-rhIL2-E61 and 30KD PEG-rhIL2-P65, rhIL2-K35, rhIL2-T41, rhIL2-Y45, rhIL2-E61, rhIL2-P65 samples before coupling and an IL-2 reference substance (purchased from Beijing Solebao Tech technologies Co., Ltd., product number: P00020) are respectively diluted in a gradient way, each sample has 6 concentrations (in CTLL-2 cell experiment, the concentration range of the reference substance is 0.004-4 ng/mL, 4 times of gradient dilution), in YT cell experiment, the concentration range of the reference substance is 2.1-510 ng/mL, 3 times of gradient dilution, in other samples are screened in advance experiment, and corresponding cell stimulation values are obtained in 50 minutes in 852 EC 37 ℃, then cells are lysed, a western blot experiment is performed, pSTAT5 antibody (purchased from CST, product catalog number is 9359L) and beta-actin (purchased from CST, product catalog number is 8457S) are adopted for hybridization, the protein amounts of pSTAT5 and beta-actin in cell lysate are detected, and EC50 is calculated according to pSTAT 5/beta-actin gray scale result and sample concentration. The results are shown in Table 2. The results show that rhIL2 with the unnatural amino acid NBOK inserted into the sites of K35, T41, Y45, E61 and P65 and coupled with 30KD PEG all reach the original design requirements (taking the reference as a control, the EC50 ratio is changed in a lower percentage than the reference).

TABLE 2 STAT5 phosphorylation assay results

The calculation formula is: [ YT cell EC50 in 30KD PEG-rhIL2 sample/CTLL-2 cell EC50 in 30KD PEG-rhIL2 sample ]/[ YT cell EC50 in reference/CTLL-2 cell EC50 in reference ] x 100%

Example 6 pharmacokinetic Studies in mice

The experiment adopts female C57 mice (SPF grade, purchased from Wentonlifwa laboratory animal technology Co., Ltd., Zhejiang) and takes SpongrIL-2 (purchased from spring harbor pharmaceutical industry Co., Ltd., Shandong) as a positive control drug to examine the metabolism condition of the test object 30KD PEG-rhIL2-Y45 in the mice. 30KD PEG-rhIL2-Y45 and quacki rhIL-2 are respectively dosed by a single intravenous injection of 1mg/kg, and blood is collected at the following blood collection points, wherein each point is 0.5mL (n is 5): before administration, 0.0833h, 0.5h, 1h, 4h, 8h, 16h and 24h after administration, and 5 blood collection points are additionally arranged on 30KD PEG-rhIL 2-Y45: 48h, 72h, 96h, 120h and 144 h. The blood sample is placed at room temperature for 15min, and centrifuged at 6800g/min for 6min to obtain serum. Blood serum concentration was analyzed as follows:

(1) coating: 50 μ L of 1 μ g/mL Anti-IL-2 antibody (purchased from abcam, cat. No. ab9618) working solution was added to each well of a high-adsorption 96-well plate and incubated overnight at 2-8 ℃. (2) Cleaning: discard the well fluid, wash 3 times with 1 XPBST (0.05% Tween-20), 300. mu.L/well. (3) And (3) sealing: casein blocking solution (available from Thermo under catalog No. 37528) was added at 200. mu.L/well and allowed to stand at room temperature for 90 min. (4) Cleaning: discard the well liquid, wash 3 times with 1 XPBST, 300. mu.L/well. (5) Sample adding: diluting the QuanqirhIL-2, 30KD PEG-rhIL2-Y45 and the serum sample to be detected with mouse serum gradient, transferring into a microporous plate according to 50 muL/hole, and standing at room temperature for 120 min. (6) Cleaning: discard the well liquid, wash 3 times with 1 XPBST, 300. mu.L/well. (7) A first antibody: mu.L of 0.25. mu.g/mL IL-2Monoclonal Antibody (BG5), Biotin (ex Invitrogen, Cat. M600B) working solution was added to each well and allowed to stand at room temperature for 60 min. (8) Cleaning: discard the well liquid, wash 3 times with 1 XPBST, 300. mu.L/well. (9) Secondary antibody: will Pierce^TMHigh Sensitivity Streptavidin-HRP (available from Thermo, catalog No. 21130) was diluted 4000-fold with casein blocking solution, 50. mu.L per well and allowed to stand at room temperature for 60 min. (10) Medicine for treating acute respiratory syndromeWashing: discard the well liquid, wash 4 times with 1 XPBST, 300. mu.L/well. (11) Substrate: add 50. mu.L of 1-Step to each well^TMTurbo TMB-ELISA Substrate Solution (available from Thermo, catalog No. 34022). (12) Terminate and read: after 25min, 2M sulfuric acid stop solution was added and absorbance at 450nm and 650nm was read on a microplate reader (available from Perkin Elmer, model EnSight). (13) And (3) analysis: four-parameter fitting is carried out through Dazdaq Ltd. WorkOut 1.5 analysis software, the concentrations and units of the corresponding quanzhi rhIL-2 and 30KD PEG-rhIL2-Y45 are input, a curve is fitted for each of the concentrations and the units, and the blood concentration of the serum to be detected is calculated respectively. According to a non-atrioventricular model (statistical moment parameter) of DAS software, the average half-life t of the fudge rhIL-2 and the 30KD PEG-rhIL2-Y45 is calculated_1/20.83h and 19.83h respectively. The pharmacokinetic parameters of SpongrIL-2 and 30KD PEG-rhIL2-Y45 are shown in Table 3.

TABLE 3 pharmacokinetic parameters of quackie rhIL-2 and 30KD PEG-rhIL2-Y45 (n ═ 5)

Example 7 pharmacodynamic study in mice-antitumor Activity

The experiment adopts female Balb/c mice (SPF grade, Zhejiang vitamin Tonglihua laboratory animal technology Co., Ltd.), 2 × 10⁵0.1 mL/mouse CT26.WT (purchased from ATCC, Cat. No. CRL-2638) cell suspension and 4X 10⁵0.1 mL/mouse H22 (from CCTCC, Cat. GDC0091) cell suspension was inoculated subcutaneously into the right dorsal part of the mouse to achieve a tumor volume of 50mm³On the left and right, the mice were divided randomly into groups, and each group of 7 mice was administered with vehicle (1 XPBS), 0.7mg/kg 30KD PEG-rhIL2-T41, 5.0mg/kg 30KD PEG-rhIL2-T41, 0.7mg/kg 30KD PEG-rhIL2-Y45, and 5.0mg/kg 30KD PEG-rhIL2-Y45 (the administration volumes were all 10 mL/kg). Animal body weights and tumor volumes were measured 3 times per week during the experiment, and the mode of administration and the results of the experiment are shown in table 4. Relative inhibition ratio TGI_TWThe formula for the calculation of (%): (T)_WC-T_WT)/T_WCX 100% where T_WCMean tumor weight, T, for vehicle control group_WTAveraged for treatment groupTumor weight.

The result shows that compared with the solvent group, the high-low dose group of 2 test objects has obvious inhibition effect on mouse colon cancer CT26.WT and mouse liver cancer H22 homograft tumor.

TABLE 4 administration of test substances in the CT26.WT and H22 allograft tumor model and Effect on tumor weight in animals

Note: *: p is less than 0.05; **: p is less than 0.01; ***: p < 0.001, compared to vehicle group.

Example 8 pharmacodynamic Studies in mice-expression of immune cell populations

The experiment adopts female Balb/c mice (SPF grade, Zhejiang vitamin Tonglihua laboratory animal technology Co., Ltd.) of 2 × 10⁵0.1 mL/mouse CT26.WT cell suspension was inoculated subcutaneously into the right dorsal part of the mouse to achieve a tumor volume of 100mm³On the left and right, the mice were randomly grouped into 3 mice each and each test substance (among them) was administered according to Table 5For commercial recombinant human IL-2 injection), the administration volume is 10 mL/kg. On day 5, groups of tumor tissue samples were harvested for flow detection of CD8⁺T cells and CD4⁺The results of the change in the proportion of Treg cell population are shown in table 5.

Table 5 mode of administration of test substances in the ct26.wt allograft tumor model and effect on immune cell population

Comparison with the Quanqi control, of 30KD PEG-rhIL2-T41 and 30KD PEG-rhIL2-Y45CD8⁺A significant increase in the proportion of T cells, CD4⁺Significant reduction in the proportion of Treg cells, CD8⁺ T/CD4⁺The proportion of Tregs is obviously increased, and the excellent drug effect of enhancing immunity is shown.

EXAMPLE 9 reduction of the active group of Lys-azido

Referring to the method of example 1, rhIL-2 (rhGH-V91 for short) expression strain in which the codon for amino acid 91 (valine) was mutated into amber was constructed using the following primers:

V91-F：5’-GATTTCCAATATCAACTAGATTGTTCTGGAACTGA-3’(SEQ ID NO:48)

V91-R：5’-TCAGTTCCAGAACAATCTAGTTGATATTGGAAATC-3’(SEQ ID NO:49)。

referring to example 2, the rhGH-V91 expression strain was used to express rhIL-2 mutated at position 91 to Lys-azido by adding Lys-azido during fermentation, and purified by the corresponding purification method of example 2. The complete molecular weight of rhIL-2 in which position 91 was mutated to Lys-azido was analyzed by LC-MS (high resolution Mass Spectrometry: XevoG2-XS Q-Tof, Waters; ultra high Performance liquid chromatography: UPLC (acquisition UPLC I-Class), Waters) as shown in FIG. 6. The results showed that a fraction of about 26Da smaller than the theoretical molecular weight (15672.75Da) appeared in the sample, which was deduced to be an azide structure (-N) at the Lys-azido terminus₃) Is reduced to (-NH)₂) The product of (1).

Reduction of Lys-azido results in rhIL-2 mutated to Lys-azido not being able to couple to BCN-PEG, thus reducing the coupling rate. When the rhIL-2 containing the unnatural amino acid is coupled with PEG, the coupling rate is obviously improved, so that the reaction efficiency is obviously improved.

Unless otherwise defined, all terms used herein have the meanings commonly understood by those skilled in the art.

The described embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the present invention, and those skilled in the art may make various other substitutions, alterations, and modifications within the scope of the present invention, and thus, the present invention is not limited to the above-described embodiments but only by the claims.