CN111303246B

CN111303246B - Mimic peptide combined with cN-II and pharmaceutical application thereof

Info

Publication number: CN111303246B
Application number: CN202010222299.0A
Authority: CN
Inventors: 宋林; 王书峰; 张若琪; 贾运涛; 刘彬; 陈勇刚; 刘耀
Original assignee: Childrens Hospital of Chongqing Medical University
Current assignee: Childrens Hospital of Chongqing Medical University
Priority date: 2020-03-26
Filing date: 2020-03-26
Publication date: 2021-08-27
Anticipated expiration: 2040-03-26
Also published as: CN111303246A

Abstract

The invention relates to a mimic peptide combined with cN-II, and the amino acid sequence of the mimic peptide is shown in SEQ ID NO 1-SEQ ID NO 10. The mimetic peptide binds to cN-II and antagonizes cN-II. The mimic peptide cNMP represented by SEQ ID No.1 provided by the invention can inhibit the high expression of cN-II in Jurkat cells, and the combined culture can effectively improve the proliferation inhibition rate and apoptosis rate of the cells under the action of araC and 6-MP so as to reduce the drug resistance and disease recurrence of nucleoside analogues such as araC and 6-MP in the treatment of ALL diseases.

Description

Mimic peptide combined with cN-II and pharmaceutical application thereof

Technical Field

The invention belongs to the field of biotechnology and medicine, relates to a mimic peptide combined with cN-II, and also relates to application of the mimic peptide in preparation of drugs related to nucleoside analogue drug resistance diseases.

Background

II Acute Lymphoblastic Leukemia (ALL) is the most common hematological malignancy in childhood, is a malignant proliferative disease of the hematopoietic system, and is a leading cause of malignant death in children. It is characterized by that the leukemia cells are arrested in different stages of cell development, and lose the capacity of differentiation and maturation, and can be malignant proliferated. The malignant cloned leucocytopathy cells not only inhibit the normal hematopoiesis of bone marrow and other hematopoietic tissues, but also can further infiltrate other organs and tissues, and the clinical manifestations of the leucocytopathy are acute in onset, rapid in progress, severe in illness state, and seriously harm the life quality and life span of children patients. Chemotherapy is the most main treatment means at present, the cure rate is only 40%, about 20% of children patients have drug resistance and relapse, some children patients have drug resistance to chemotherapy drugs, and the children patients receive overhigh-intensity chemotherapy. Therefore, a new treatment way and a new treatment scheme are searched for, the overall cure rate is improved, adverse reactions of chemotherapeutic drugs are reduced, the life quality of children and family members is improved, the death rate is reduced, and the long-term prognosis is improved, so that the method becomes a hotspot and a problem to be urgently broken through in the current hematology research.

Nucleoside analogues are important chemotherapeutic drugs for the treatment of ALL, which act as precursors to generate active metabolism in cells via kinase phosphorylation to inhibit cell proliferation and kill tumor cells. cN-II (cytosolic 5 '-nucleotidase-II) is a cytoplasmic 5' -nucleotidase, and encodes nt5c2 (10 q24.32), which is a protein consisting of 561 amino acids, contains 4 identical subunits, has a molecular weight of 65kD, is highly conserved, and has at least 95% homology with cN-II proteins of other mammals. cN-II has both hydrolase and phosphotransferase activities, and can catalyze dephosphorylation and hydrolysis of purine nucleotides and phosphorylation of nucleosides. Multiple researches show that cN-II can hydrolyze monophosphoryl nucleoside analogue from 5' end to reduce intracellular concentration of active metabolite for resisting medicine; and cell and tissue experiments prove that the drug resistance of the drug is closely related to the abnormal expression of cN-II. In recent years, multiple studies show that high expression of nt5C2 and cN-II is an important reason for drug resistance and relapse treatment of nucleoside analogue chemotherapy of leukemia patients, and further Jurkat cell experiments prove that 6-mercaptopurine (6-MP) and cytarabine (Ara-C) can induce the expression of nt5C2 mRNA and cN-II of cells, and the expression degree of the nt5C2 mRNA and cN-II is obviously related to the apoptosis rate and proliferation inhibition rate of the cells under the action of the nucleoside analogue. Recent studies also showed that nt5c2 is a common downstream signal of multiple signaling pathways associated with ALL relapse; therefore, the cN-ii encoded by nt5c2 is a very critical antagonistic target in prevention and treatment studies of ALL resistance relapse.

Disclosure of Invention

In view of the above, the present invention provides a mimetic peptide bound to cN-ii, and further provides the use of the mimetic peptide bound to cN-ii in preparing drugs related to nucleoside analogue resistant diseases.

In order to achieve the purpose, the invention provides the following technical scheme:

1. a mimic peptide combined with cN-II, the amino acid sequence of the mimic peptide is shown as SEQ ID No.1-SEQ ID No. 10.

Furthermore, the amino acid sequence of the mimic peptide is shown as SEQ ID No. 1.

2. A pharmaceutical composition comprises a pharmaceutically acceptable carrier and an effective amount of a mimic peptide with an amino acid sequence shown as any one of SEQ ID NO 1-SEQ ID NO 10.

3. A pharmaceutically acceptable salt of a mimetic peptide which binds to cN-ii, said pharmaceutically acceptable salt being formed by reacting a mimetic peptide having an amino acid sequence as set forth in any one of SEQ ID No.1 to SEQ ID No.10 with an acidic compound or a basic compound.

Further said pharmaceutically acceptable salt is selected from the group consisting of sulfate, trifluoroacetate, sulfite, pyrosulfate, bisulfite, phosphate, acrylate, hydrogen phosphate, metaphosphate, pyrophosphate, hydrochloride, bromide, iodide, phenylpropionate, propionate, caprylate, formate, isobutyrate, hexanoate, heptanoate, propiolate, oxalate, maleate, malonate, succinate, suberate, fumarate, butyn-l, 4-dioate, hexyne-1, 6-dioate, acetate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phenylacetate, phenylbutyrate, dihydrogenphosphate, citrate, lactate, gamma-hydroxybutyrate, glycolate, acetate, dihydrogenphosphate, citrate, lactate, gamma-hydroxybutyrate, glycolate, acetate, citrate, phosphate, citrate, acetate, and/or a salt, acetate, and/or a salt, acetate, and/or a salt, One or more of tartrate, mesylate, propanesulfonate, naphthalene-l-sulfonate, naphthalene-2-sulfonate, and mandelate.

4. An Fc chimera of recombinant polypeptide is obtained by fusing a mimic peptide with an amino acid sequence shown as any one of SEQ ID No.1-SEQ ID No.10 with an Fc fragment of IgG1 by using a genetic engineering means or a semisynthesis method.

5. The application of the mimic peptide which has the amino acid sequence shown as any one of SEQ ID No.1-SEQ ID No.10 and is combined with cN-II in preparing the drugs related to the drug resistance symptoms of the nucleoside analogues.

Further, the nucleoside analogue is Ara-C and/or 6-MP.

6. The application of the Fc chimera of the recombinant polypeptide in preparing the medicine related to the drug resistance of the nucleoside analogue is obtained by fusing the mimic peptide with the Fc segment of IgG1, wherein the mimic peptide has an amino acid sequence shown as any one of SEQ ID No.1-SEQ ID No.10, by means of genetic engineering or semisynthesis.

7. The application of the mimic peptide with the amino acid sequence shown as any one of SEQ ID No.1-SEQ ID No.10 in preparing related medicines combined with cN-II.

The invention has the beneficial effects that: polypeptides are provided which bind to cN-II and are antagonistic to cN-II, act on cN-II dimers, inhibit formation of dimers, or act on preformed dimers or tetramers to inhibit tetramer formation and thereby affect their biological function. The mimic peptide cNMP represented by SEQ ID No.1 or SEQ ID No.11 provided by the invention can inhibit the high expression of cN-II in Jurkat cells, and the combined culture can effectively improve the proliferation inhibition rate and apoptosis rate of the cells under the action of araC and 6-MP so as to reduce the drug resistance and disease relapse of nucleoside analogues such as araC and 6-MP in the treatment of ALL diseases.

Drawings

In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1 shows the overall conformation of the interaction of HP1 with cN-II, the blue helix of which is the polypeptide HP 1.

FIG. 2 shows the H bond site of HP1 interacting with cN-II.

FIG. 3 shows the overall conformation of RP1 in response to cN-II, the blue linear polypeptide RP 1.

FIG. 4 shows the H bond site of RP1 interacting with cN-II.

FIG. 5 shows the dimeric structure of cN-II (cytosolic-5' -nucleotidase-II).

FIG. 6 shows the tetrameric structure of cN-II (cytosolic-5' -nucleotidase-II).

FIG. 7 is a graph showing the comparison of the relative expression levels of Ara-C in combination with HP1 and RP1 at different concentrations, respectively.

FIG. 8 is a graph showing the comparison of the relative expression levels of 6-MP in combination with HP1 and RP1 at different concentrations, respectively.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The experimental procedures, in which specific conditions are not specified in the examples, are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

Example 1

cN-II (cytosolic-5' -nucleotidase-II) plays a biological role in vivo as two identical dimers that are homologous to form a tetramer. Screening a large amount of mimic peptide (cNP-II mimetic peptide, cNMP) capable of being combined with cN-II by ribosome display technology; analyzing the crystal structure of cN-II, and performing bioinformatics analysis on the simulated peptide by repeated homologous modeling, molecular docking of the ZCDOCK and RDOCK tools of discovery studio (TM); further, in vitro tests are carried out to preferably select the mimic peptide with obvious effect of inhibiting the expression of the leukemia cell cN-II, so that the mimic peptide which is specifically combined with cN-II, has cN-II antagonistic effect and the effect of reversing ALL cell nucleoside analogue drug resistance, can act on cN-II dimer, can play a role in inhibiting the formation of dimer, or acts on the formed dimer or tetramer to inhibit the formation and the function of tetramer. FIG. 5 shows the dimer structure of cN-II (cytosolic-5 '-nucleotidase-II) and FIG. 6 shows the tetramer structure of cN-II (cytosolic-5' -nucleotidase-II).

A series of polypeptides with the length of 15, represented by two polypeptides shown as SEQ ID No.1 and SEQ ID No.11, are obtained through a large amount of screening results. SEQ ID No.1 is a polypeptide based on a helical structure: HP1: ASYESLFDNVRDAVS. FIG. 1 shows the overall conformation of the interaction of HP1 with cN-II, the blue helix of which is the polypeptide HP 1. FIG. 2 shows the H bond sites where HP1 interacts with cN-II, the most critical two amino acid sites in the middle of the polypeptide being the 11R and 12D sites, since these sites form H bonds with K at 308 and 254 on cN-II, respectively. On the basis, the amino acids at the 2 sites are kept unchanged, and the amino acids at other sites are changed, particularly, the mutation is optimally carried out by using similar amino acids, such as D-E, N-Q, V-A, L-I, K-R, F-Y, S-T and the like, and the other sites are subject to ensuring the helical structure of the polypeptide.

The polypeptide shown in SEQ ID No.11 is based on a band conformation, RP 1: QGTAFSQAVSPTGSL are provided. FIG. 3 is the global conformation of RP1 interacting with cN-II and the blue linear is polypeptide RP 1; FIG. 4 shows the H-bond sites at which RP1 interacts with cN-II, where sites 3, 5, 7, 8, and 10 are key sites in the polypeptide, forming H-bonds with 76R, 177R, 187D, and 200D on the cN-II dimer. On the basis, the amino acids at the 5 sites are kept unchanged, and the amino acids at other sites are changed, particularly, the mutation is optimally carried out by using similar amino acids, such as D-E, N-Q, V-A, L-I, K-R, F-Y, S-T and the like. Table 1 shows the mimetic peptide sequences that antagonize cN-II.

TABLE 1 mimetic peptide sequences for cN-II antagonism

Example 2

The polypeptide of the present invention may be prepared by recombinant DNA techniques or may be synthesized by chemical synthesis, such as Fmoc solid phase polypeptide synthesis. Using Wang resin as solid phase reaction matrix, linking-COOH of C-terminal amino acid of target peptide chain on solid phase resin with coupling reagent, and removing its-NH₂And (3) reacting the protecting group with-COOH of the next amino acid to form a peptide bond, repeating the steps to grow the peptide chain, namely performing coupling reaction, washing, removing the amino protecting group, washing and coupling in a new round until a target peptide segment is synthesized, finally cutting the target peptide from the solid phase carrier by using a cutting reagent, and performing certain treatment to obtain the target peptide.

The Fmoc solid-phase polypeptide synthesis method comprises the following specific steps:

preparation of Fmoc-Ser-Wang Resin

1.1 weighing Wang resin (substitution degree of 0.787mmol/g, 1% DVB, 100-;

1.2 weighing 1.1680g of Fmoc-Ser-OH, 0.058g of DMAP and 0.638g of HOBT, adding 10ml of DMF/DCM (1:1, V/V), stirring for dissolving, adding 2ml of DIC, activating at low temperature for 5min, and then pouring into resin;

1.4 reacting for 2h at normal temperature, and emptying reaction liquid after the reaction is finished;

1.5 washing the resin 3 times with DMF under nitrogen agitation; the resin was washed with DCM under nitrogen stirring for 2 times;

1.6 adding a mixed solution of acetic anhydride/pyridine (1:1, mol/mol) into resin, stirring for reacting for 8 hours, and emptying a reaction solution;

1.7 washing the resin with DMF under nitrogen stirring for 5 times, and then washing the resin with DCM under nitrogen stirring for 2 times; finally, washing with MeOH for 2 times, draining the solution, and placing the Resin in an oil pump for draining to obtain Fmoc-Ser-Wang Resin.

1.8 detecting the substitution degree (sub) for standby;

preparation of peptide resins

2.1 weighing the Fmoc-Ser-Wang Resin prepared above, adding 20% DBLK solution, fully stirring for reaction for 5min, and emptying the solution; adding 20% DBLK solution again, fully stirring and reacting for 7min, and emptying the solution; the resin was washed 5 times with DMF under nitrogen stirring, and 2 times with DCM under nitrogen stirring;

2.2 weighing 0.581g of Fmoc-Val-OH, 0.570g of HBTU and 0.243g of HOBT into a reaction vessel, adding DMF/DCM (1:1, v/v) and introducing nitrogen to stir for 2h, and emptying the reaction solution. Adding 10ml of DMF, and washing for 3 times;

2.3 adding 10ml of 20% DBLK solution, stirring the peptide resin thoroughly for about 5min, emptying the solution;

2.4 adding 10m l 20% DBLK solution, fully stirring the peptide resin for about 7min, and emptying the solution;

2.5 washing 5 times with DMF and 2 times with DCM;

2.6 weigh 0.596g of Fmoc-Ala-OH, 0.243g of HOBT, and 0.570g of HBTU into a reaction vessel, add DMF/DCM (1:1, v/v) and stir with nitrogen for 2h, and empty the reaction. 10ml of DMF was added and the mixture was washed 3 times. Repeating the steps for 2.3 to 2.5 according to the sequence of the HP1 peptide chain, and respectively coupling with corresponding amino acid; coupling up to the last amino acid;

2.7 adding 10ml MeOH in the resin, fully stirring the reaction for 10min, emptying the liquid, repeatedly washing with MeOH two times;

2.8 drying under vacuum gave a peptide resin containing the peptide sequence HP 1.

Cracking

3.1 the peptide resin was weighed and placed in a flask. A lysate (TFA: Tis: H2O: EDT: 91:3:3:3) was prepared at 10ml/g (10 times);

3.2 adding the lysate into a flask, and stirring for reaction for 2 hours;

3.3 filtering the resin reaction solution by using a sand core, and adding 10 times of the filtrate into the ethyl acetate for precipitation;

3.4, centrifugally separating and collecting precipitates. Washing with frozen diethyl ether for 2 times;

3.5 vacuum drying the precipitate, weighing, get crude HP1 polypeptide.

RP1 was also synthesized according to the amino acid sequence of SEQ ID No.11 by Fmoc solid phase polypeptide synthesis.

Example 3

Cytarabine (Ara-C) belongs to Cytarabine (Ara-C) and pyrimidine antimetabolites, is mainly used for treating acute leukemia and malignant lymphoma, and particularly has a good curative effect on acute myelocytic leukemia, and reports that: the complete remission rate of the initially treated acute myeloblastic leukemia patient receiving the Ara-C containing chemotherapy regimen is 65-80%. However, most patients who have achieved complete remission will relapse within two years after a clear diagnosis, which may be related to the development of drug resistance by tumor cells, leading to poor therapeutic efficacy of subsequent treatments. After Ara-C enters tumor cells, two-step phosphorylation activation reaction is carried out to generate an active product Ara-CTP, and the synthesis of DNA is inhibited. Similarly, cN-II also hydrolyzes Ara-CMP, the monophosphate-activated product of Ara-C, inhibiting its continued phosphorylation activation, leading to drug failure.

6-MP (6-mercaptopurine ) belongs to a cell synchronization specific drug for inhibiting a purine synthesis pathway, has a chemical structure similar to that of hypoxanthine, and can competitively inhibit the conversion process of the xanthine. When entering into the body, the cell must be converted from phosphoribosyl transferase to 6-mercaptopurine ribonucleotide and then has activity. The main action links are as follows: (1) inhibiting amidotransferase by negative feedback, thereby preventing the conversion of 1-pyrophosphate-5-phosphoribosyl phosphate (RRPP) to 1-amino-5-phosphoribosyl Phosphate (PRA), interfering with the initial stage of purine nucleotide synthesis; (2) inhibiting the mutual transformation of complex purine compounds, namely inhibiting the process of converting hypoxanthine nucleotide into adenine nucleotide and converting xanthine nucleotide into xanthine nucleotide and guanine nucleotide. However, treatment of leukemia with mercaptopurine often results in drug resistance, probably due to the loss of the ability to convert mercaptopurine to mercaptopurine ribonucleotides.

Human acute T cell leukemia cell line Jurkat, purchased from Shanghai Biochemical and cell biological cell Bank of Chinese academy of sciences. RPMI1640 medium was purchased from GIBCO.

Preheating RPMI1640 culture solution with 37 deg.C constant temperature water bath tank for half an hour, irradiating superclean bench 30 with ultraviolet lampAnd (3) minutes. Taking out the Jurkat cell cryopreservation tube from the liquid nitrogen tank by using forceps, quickly putting the Jurkat cell cryopreservation tube into a 37 ℃ constant temperature water bath box for water bath, and quickly and ceaselessly shaking the cell cryopreservation tube to fully melt the cell cryopreservation liquid. In a clean bench, the cell suspension was aspirated by a pipette, transferred to a 50mL centrifuge tube, and 20mL of RPMI1640 medium was added. Centrifuge at 1000rpm for 10 minutes and aspirate the supernatant. Then adding 2mL of RPMI1640 medium containing 15% fetal calf serum and 1% cyan-streptomycin, slightly blowing and scattering, and then inoculating in the RPMI1640 medium containing 15% fetal calf serum and 1% cyan-streptomycin, wherein the culture environment is as follows: temperature 37 ℃ and 5% CO₂And (4) a saturated humidity incubator, wherein liquid is changed for 2-3 days and subculture is carried out according to the ratio of 1:2-1:3, and cells used in the experiment are in a logarithmic phase.

After culturing Jurkat cells for 24h using Ara-C (5. mu.M/L), 6-MP (5. mu.M/L) alone and in combination with 3 different concentrations of HP1 or RP1 mimetic peptides (20. mu.M/L, 40. mu.M/L, 80. mu.M/L), respectively, intracellular cN-II mRNA expression was determined by real-time semi-quantitative PCR, with 3 replicates per assay set. Ara-C and 6-MP are respectively taken as controls, the relative expression quantity of cN-II in the Ara-C and the mimic peptide, and in the 6-MP and the mimic peptide is obviously reduced, FIG. 7 is the comparison of the relative expression quantity of cN-II under different concentrations by combining the Ara-C with HP1 and RP1 respectively, and FIG. 8 is the comparison of the relative expression quantity of cN-II under different concentrations by combining the 6-MP with HP1 and RP1 respectively. The HP1 or RP1 mimic peptide is shown to inhibit the high expression of cN-II in Jurkat cells.

Example 4

After Jurkat cells were cultured for 24h and 48h using Ara-C (5. mu.M/L), 6-MP (5. mu.M/L) alone and 3 different concentrations (20. mu.M/L, 40. mu.M/L, 80. mu.M/L) in combination with HP1 or RP1 mimetic peptides, respectively, the cell growth inhibition was tested with CCK-8, each of Ara-C and 6-MP as controls. And measuring the apoptosis rate of the cells by adopting an Annexin V-FITC/PI double staining method.

CCK-8 test cell growth inhibition: adjusting cell density to 1 × 10 with culture medium⁵～2×10⁵cell/mL, inoculated in 96-well plates, 100. mu.l per well, and added with Ara-C (5. mu.M/L), Ara-C (5. mu.M/L) + HP1 (20. mu.M/L), Ara-C (5. mu.M/L) + HP1 (40. mu.M/L), Ara-C (5. mu.M/L) + HP1 (80. mu.M/L), 6-MP (5. mu.M/L) + HP1 (20. mu.M/L), 6-MP (5. mu.M/L) + HP1 (40. mu.M/L), respectivelyM/L), 6-MP (5. mu.M/L) + HP1 (80. mu.M/L), etc., in an amount of 10. mu.l each. Meanwhile, a blank control group is arranged, 10 mu l of culture solution is added into the blank control group, each group is provided with 6 parallel holes, and the culture is carried out for 24h and 48 h. 3h before stopping culturing, adding 10 mul CCK-8 reagent into each hole to avoid generating air bubbles, and continuously culturing for 2h in an incubator after uniformly shaking. And then detecting the light absorption value A at the wavelength of 450nm by using a full-automatic enzyme standard instrument, and calculating the cell growth inhibition rate. Inhibition rate (1-experimental a value/blank a value). The RP1 mimetics were also tested according to this test method, and the results are shown in Table 2.

TABLE 2 inhibition of cell growth at 24 hours and 48 hours for each group

Determination of apoptosis rate by Annexin V-FITC/PI double staining method: (1) adjusting cell density to 1 × 10 with culture medium⁵～2×10⁵cell/mL was inoculated into 6-well plates at 5 mL/well, and the experimental fractions were mixed with different concentrations of drug groups, such as Ara-C (5. mu.M/L), Ara-C (5. mu.M/L) + HP1 (20. mu.M/L), Ara-C (5. mu.M/L) + HP1 (40. mu.M/L), Ara-C (5. mu.M/L) + HP1 (80. mu.M/L), 6-MP (5. mu.M/L) + HP1 (20. mu.M/L), 6-MP (5. mu.M/L) + HP1 (40. mu.M/L), 6-MP (5. mu.M/L) + HP1 (80. mu.M/L), in 6-well, 6 replicates each group. The culture was carried out in an incubator for 24 hours. Collecting cells by centrifuging for 5min at 1000g, gently suspending the cells with precooled PBS, and counting; (2) taking the resuspended cells 10 from step (1)⁵After collecting cells by adopting a method of centrifuging for 5min at 1000g, adding Binding Buffer of 200 mu Lannexin V-FITC to gently resuspend the cells; (3) adding 10 mu L Annexin V-FITC for gentle mixing; (4) incubating at room temperature in dark for 45 min; (5) centrifuging at 1000g for 5min to collect cells, and adding 200 μ L Binding Buffer of Annexin V-FITC to gently resuspend the cells; (6) adding 10 mu L of PI, mixing the mixture evenly and gently, and placing the cells in ice bath in a dark place; (7) detecting the apoptosis state of the cells by a computer. The RP1 mimetics were also tested according to this test method, and the results are shown in Table 3.

TABLE 3 apoptosis Rate (%) at 48 hours in each group

The results show that the combination culture of the mimic peptides cNMP shown by SEQ ID No.1 and SEQ ID No.11 can effectively improve the proliferation inhibition rate and the apoptosis rate of cells under the action of araC and 6-MP.

Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Sequence listing

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Claims

1. The mimic peptide combined with cN-II is characterized in that the amino acid sequence of the mimic peptide is shown as SEQ ID No. 1.

2. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and an effective amount of the mimetic peptide according to claim 1.

3. A pharmaceutically acceptable salt of a cN-ii binding mimetic formed by reacting a mimetic of claim 1 with an acidic compound or a basic compound.

4. The pharmaceutically acceptable salt of claim 3, selected from the group consisting of sulfate, trifluoroacetate, sulfite, pyrosulfate, bisulfite, phosphate, acrylate, hydrogen phosphate, metaphosphate, pyrophosphate, hydrochloride, bromide, iodide, phenylpropionate, propionate, caprylate, formate, isobutyrate, hexanoate, heptanoate, propiolate, oxalate, maleate, malonate, succinate, suberate, fumarate, butyn-l, 4-dioate, hexyne-1, 6-dioate, acetate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phenylacetate, phenylbutyrate, dihydrogenphosphate, citrate, lactate, gamma-hydroxybutyrate, glycolate, acetate, dihydrogenphosphate, citrate, lactate, gamma-hydroxybutyrate, glycolate, acetate, citrate, acetate, phosphate, acetate, phosphate, acetate, phosphate, acetate, phosphate, acetate, phosphate, acetate, phosphate, acetate, phosphate, One or more of tartrate, mesylate, propanesulfonate, naphthalene-l-sulfonate, naphthalene-2-sulfonate, and mandelate.

5. Use of a cN-ii binding mimetic peptide according to claim 1 in the manufacture of a medicament for treating a condition associated with resistance to a nucleoside analogue, wherein said nucleoside analogue is Ara-C and/or 6-MP.

6. Use of the mimetic peptide according to claim 1 for the manufacture of a medicament related to cN-ii binding.