Metal-based Anti-cancer complex

Abstract

A metal complex comprising: (a) a pharmaceutically acceptable central metal; (b) a DNA methyltransferase (DNMT) inhibitor; and (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA).

Description

[0001] METAL-BASED ANTI-CANCER COMPLEX

[0002] FIELD OF THE INVENTION

[0003] The present invention focuses on the nanomedicine field for anticancer therapies and in particular is concerned with metal complexes comprising a DNA methyltransferase (DNMT) inhibitor, pharmaceutical compositions comprising the metal complexes, the use of the metal complexes in methods of treating cancers, processes for preparing the metal complexes and synthetic intermediates useful in those processes.

[0004] BACKGROUND TO THE INVENTION

[0005] During the last decades, anti -cancer nanomedicine has been extensively studied for both therapeutic and diagnostic clinical applications such as drug delivery, gene delivery, thermotherapy, as well as diagnostic and molecular imaging.

[0006] Nanomedicine clinical application

[0007] Generally, nanomedicine can be classified as various types of liposome, polymeric micelles, metal or metal-oxide nanoparticles, as well as nano-biomaterials, tumor nanovaccines, and nucleic acid-related nanocarriers. To date, of the nano-pharmaceuticals approved for cancer therapy by the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), the majority (56%) are lipid-based nano-formulations, while the rest falls under the categories of protein-based (38%) and metal-based nanoformulations (6%) [1],

[0008] Nanomedicine limitation / obstacles:

[0009] Although a number of nanomedicines have been approved for clinical use or entered clinical trials, some of them still failed or were unsatisfactory in the clinic. Specifically, pharmaceutical nanoparticles with the advantage of good repeatability / reproducibility of particle size may suffer from: (a) poor safety and heavy side effects; (b) unsatisfactory treatment outcomes / efficacy; and / or (c) complex and expensive scale-up manufacturing. Nano-toxicity:

[0010] Many nanomedicines clinical trials fail due to nanotoxicity. For example, in 2020, the phase 1 clinical trial of the liposomal drug MRX34 (NCTO 182997), a liposomal mimic of microRNA-34a which represents the nanotechnology-enabled nucleic acid drug in cancer treatment, was terminated due to severe immune-related adverse reactions in four patients [2], Although it provided proof-of-concept for miRNA-based cancer therapies, there is still an urgent need for improvement of the poor safety profile and heavy side effects of nanomedicines. Of particular interest are green synthesis methods, where the active agents can be extracted from natural component / sources like plants or fungi, since components from these sources tend to degrade into substances that are biocompatible and / or are naturally found in the body.

[0011] Unsatisfying therapeutic effectiveness

[0012] According to a systemic study, which fully investigated the use of cancer nanoformulations in clinical trials as of September 2022, the probability for a successful phase 1 far exceeds 80%. Unfortunately, the success rates shown decreased in phase 2 clinical investigations [2], Between 2007 and 2022, there are 14 clinical studies associated with cancer nano-formulations involving chemotherapy, but only nine of them have published their results. Specifically, of the published studies, three phase 3 studies of HER-2 targeted liposomal doxorubicin hydrochloride in treating breast cancer (MM-302, NCT02213744), Paclitaxel micelle in treating breast cancer (NK105, NCT01644890), and Irinotecan PEG conjugate in treating breast cancer (NKTR-102, NCT01492101) resulted in failure due to their poor efficacy.

[0013] Complexity of chemistry and manufacturing:

[0014] Nanoparticle production for nanomedicine uses various materials, with lipids being the most common organic option. However, the production of lipid-based nanoparticles for nanomedicine involves complex processes such as high-pressure homogenization, microemulsion, solvent emulsification evaporation / diffusion, membrane contact, ultrasonication, and multiple emulsion techniques [3], These complexities pose significant challenges for scaling up production. In contrast, metal -based nanoparticles offer more straightforward manufacturing processes, making them more easily scalable and potentially more suitable for large-scale production.

[0015] Cancer disease background and treatment limitations:

[0016] Malignant tumours pose a significant threat to human health. Worldwide, such diseases rank as the third leading cause of death, following cardiovascular and infectious diseases. Clinical treatments for malignant tumour primarily include surgery, radiotherapy, chemotherapy, molecular targeted therapy, and immunotherapy. Surgery is advantageous for early-stage patients, but its benefits are limited for the majority of patients in intermediate and late stages. Severe side effects induced by radiotherapy and chemotherapy, particularly treatment intolerance caused by chemotherapy -induced bone marrow suppression, often prevent patients from completing the corresponding treatment regimens. Molecular targeted therapy is suitable for patients with specific genetic mutations, but drug resistance frequently leads to treatment failure. Immunotherapy has emerged as a hotspot in anti-tumour therapy in recent years, but its therapeutic benefits are confined to tumours with specific genetic mutations or abnormal expression of immune genes such as PD-1, LAG-3, and TIGIT.

[0017] The underlying mechanisms of epigenetic inhibitors in treating cancer:

[0018] Epigenetic alterations are closely associated with the occurrence and development of tumours. Therefore, epigenetic drugs have been applied as reversible chemical modifiers in clinical environments. Among the drugs considered for treatment of cancers or / and tumours, epigenetic inhibitor-based ones, for instance DNA methyltransferases (DNMTs) inhibitors, are representatives of a powerful strategy geared toward modulating DNA methylation patterns in restoring aberrant gene expression of tumour suppressors. For example, DNA methylation inhibitors, such as decitabine and azacytidine, have been approved by FDA for the treatment of patients diagnosed with myelodysplastic syndromes and / or acute myeloid leukemia since 2006 [4], Apart from these hematologic malignancies, various types of solid tumour, particularly colorectal cancer, have been demonstrated to exhibit widespread DNA aberrant methylation during early tumorigenesis and late-stage metastasis. Drawbacks of epigenetic inhibitor in clinical application:

[0019] Despite a dramatic improvement with hypomethylating agents, such as DNA methyltransferase (DNMT) inhibitor drugs, they still suffer from major drawbacks, for example, decitabines and azacytidines poor chemical stability, poor pharmacokinetics, as well as their relative toxicity, which all greatly restrict the clinical applicability.

[0020] Firstly, according to the technical sheet for decitabine, it is a sensitive / fragile molecule with very low stability which needs to be stored in cold (2-8 °C) 0.9% sodium chloride solution. The drug stability is only 3 hours (at 2-8 °C) when diluted, and the mother solution must be used immediately or, otherwise, discarded [5], Furthermore, DNA hypomethylation agents are highly unstable in aqueous solutions and prone to natural hydrolysis, rendering them unable to maintain effective plasma drug concentrations, thereby limiting their clinical efficacy [5], For example, the spontaneous hydrolytic cleavage of decitabine results in a halflife of between 3-4 hours in alkaline and acid solution in vitro. Furthermore, it can only be administrated intravenously as its very low bioavailability [6],

[0021] Secondly, decitabine shows a very short half-life following clinical administration. It has been demonstrated that >90% of decitabine is cleared / lost within an hour following infusion when administrated to patients via intravenous injection. This makes it difficult to achieve stable pharmacokinetics.

[0022] Lastly, as a relative low toxicity hypomethylating pharmaceutical agent, the most common adverse effects of decitabine include cytopenia, nausea, pain and erythema / nodules at the injection site [7], Nevertheless, there were some instances of more severe adverse effect cases when applied in clinical, for example acute myocarditis and urinary retention [7, 8],

[0023] Elements of metal complex approved by FDA for clinical use

[0024] Generally, metals are essential components of cellular activities and are involved in multiple biological processes. For example, in the liver, magnesium is an important regulator which is associated with gluconeogenic enzymes, therefore magnesium deficiency is significantly related to insulin resistance [9], Additionally, in the context of the immune system, magnesium plays a crucial role in the body’s response against cancer cells

[0010] , To date, metal complexes based on the elements Li, Mg, Al, K, Ca, Fe, Co, Ga, As, Sr, Y, Zr, Pd, Ag, Sb, Sm, Lu, Pt, Au, Hg, Bi, and Ra have already been approved for clinical use in the US and / or the EU

[0011] , Chaga (Inonotus obliqquus) as a green source for anti-cancer therapeutics with high clinical potential

[0025] Chaga (Inonotus obliquus) belongs to the Hymenochaetaceae genus and thrives in areas of Europe, Asia, and northern parts of America. In 2013, based on low molecular weight polyphenolic compounds analysis, two of seven natural extracts could be identified as 2,5- dihydroxyterephthalic acid (DTA) and syringic acid (SA). These two chemicals, which fortunately show an extremely low toxicity towards the activities of human DNA metabolic enzymes and DNA topoisomerase, are of great interest for medical applications. In 2023, the pharmaceutical and nutraceutical products contained in Chaga were proven to be effective against a diverse type of malignant tumours including human colon cancer, lung cancer, breast cancer, liver cancer, melanoma, prostate cancer, and gastric cancer

[0012] , In 2024, Chaga was reported as a promising supplementary medicine for the treatment of patients with oral cancer due to its active inhibition of the cancer cell energy metabolism

[0013] ,

[0026] Enhancing biocompatibility with nanoparticle -based therapeutics

[0027] In the technical fields of nanoparticle-based therapeutic, cell membranes may be used to coat nanoparticles and enhance bio interfacing capabilities

[0014] , Autologous cells exhibit excellent biocompatibility, interface effectively with their surrounding microenvironment, and possess anti-immunity

[0015] , These cells include blood cells (erythrocytes, platelet-derived vesicles), immune cells (such as neutrophil immune cells, T cells) and macrophages (natural macrophages extracted from bone marrow, peripheral blood, peritoneal cavity, and tumour- associated macrophages, established macrophages cell lines, and genetically engineered macrophages), tumour cells, cancer stem cells, mesenchymal stem cells, and eukaryotic cells.

[0028] Additionally, biopolymers like polymer modified chitosan have been used to coat nanoparticle for small interfering RNA (siRNA) delivery to tumour tissues, presenting a promising therapeutic strategy

[0016] , Biodegradable polymers sourced from natural resources, such as alginate, chitosan, gelatin, albumin, pullulan and dextran are also used to encapsulate nanoparticles

[0017] ,

[0029] For pharmaceutical applications, covering nanoparticles with cell membranes and polymers offers the advantage of biocompatibility, targeted delivery and therapeutic enhancement. In particular, coating the nanoparticles with (a) water stable layers, such as polymers, helps to avoid hydrolysis; (b) cell membranes helps to reduce immune response; and (c) histidine-rich cell -penetrating peptides (CPPs) helps to target nanoparticles into tumour cells.

[0030] Overall, despite recent advances in this area of medicine, there exists an ongoing need for improved cancer therapeutics, and in particular for nanomedicines which overcome the problems outlined above and provide safe and effective treatments for cancer.

[0031] SUMMARY OF THE INVENTION

[0032] The present invention arises from the surprising finding that a metal complex comprising (a) a pharmaceutically acceptable central metal; (b) a DNA methyltransferase (DNMT) inhibitor; and (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA), provides an effective anti -cancer treatment.

[0033] The metal complex is generally associated with low toxicity of healthy cells (for example non-cancerous cells), enhanced biocompatibility and targeting, and improved water stability, and can potentially also provide a sustained effect over an extended period of time.

[0034] Furthermore, the DNMT inhibitor interacts synergistically with the DTA / SA and the pharmaceutically acceptable central metal, thereby providing a treatment that is more effective than the DNMT inhibitor.

[0035] In view of in vitro testing of the metal complexes by the inventors, it is also believed that more types of cancer can be treated with the metal complex of the invention than with a DNMT inhibitor alone.

[0036] A further advantage of the metal complexes is that they readily form nanoparticles which can either be used without a shell, or with a multifunctional shell that can be selected to enhance to the advantages set out above.

[0037] The metal complexes also have the advantage that they can be prepared in an environmentally friendly manner, using “green” reagents and energy efficient steps.

[0038] These and other advantages will be further described and represented through the following detailed illustration.

[0039] The invention thus provides a metal complex comprising:

[0040] (a) a pharmaceutically acceptable central metal;

[0041] (b) a DNA methyltransferase (DNMT) inhibitor; and

[0042] (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA). The invention further provides a pharmaceutical composition comprising the metal complex according to any preceding claim and one or more pharmaceutically acceptable excipients or carriers.

[0043] The invention further provides the said metal complex or pharmaceutical composition according for use as a medicament.

[0044] The invention further provides the said metal complex or pharmaceutical composition according for use in treating cancer.

[0045] The invention further provides a method of treating cancer, which comprises administering the said metal complex or pharmaceutical composition according to a subject having said cancer.

[0046] The invention further provides use of a said metal complex or pharmaceutical composition in the manufacture of a medicament for treating cancer.

[0047] The invention further provides a process for preparing a said metal complex, the method comprising:

[0048] (i) contacting a source of a pharmaceutically acceptable central metal with a source of the DTA and / or SA to form an intermediate metal complex, and

[0049] (ii) contacting the resulting intermediate metal complex with a DNMT inhibitor, thereby to provide the metal complex.

[0050] The invention further provides an intermediate metal complex comprising:

[0051] (a) a pharmaceutically acceptable central metal; and

[0052] (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA). or

[0053] (a) a pharmaceutically acceptable central metal; and

[0054] (b) a DNA methyltransferase (DNMT) inhibitor

[0055] The invention further provides use of said intermediate metal complex for the preparation of a metal complex of the invention or as an active pharmaceutical.

[0056] BRIEF DESCRIPTION OF THE FIGURES

[0057] The following section provides a brief description of the Figures. Additional commentary is provided in the detailed description and Examples section. As used in the Figures, “MC” refers to the metal complex of the invention, while “Mg and Chaga complex” and “Metal-Chaga complex” refers to the intermediate complex before addition of decitabine. Figure 1 shows the XRD results, reflection electron microscopy (REM) images and scanning electron microscope (SEM) images of the metal complex from Example 1. Figure 1A shows XRD result and reflection electron microscopy (REM) images of Mg-DTA- Decitabine metal complex from Example 1, and in particular provide the images of surface features of metal complex from 25,000x. Figure IB shows XRD result and scanning electron microscope (SEM) images of Mg-SA-Decitabine metal complex from Example 1, and in particular provide the images from 2,500x and 20,000x, respectively.

[0058] Figures 2A and 2B show standard calibration curves of decitabine in ddH2O and pH2 HC1, respectively, as determined in Example 2(i) by employing UV absorption at the wavelength of maximum absorbance of decitabine at about 284 nm.

[0059] Figure 3 shows the percentage of decitabine remaining in the metal complex over time, as determined in Example 2(ii).

[0060] Figure 4 shows the cancer cell proliferation inhibited by different treatments. The cancer cell proliferation was detected by MTT assays of human colorectal cancer cells, with Figure 4A showing HCT-116 cells and Figure 4B showing SW620 cells, as assessed in Example 3.

[0061] Figure 5 shows the results of MTT assays of human nasopharyngeal carcinoma cells, with Figure 5A showing NPC-6-108 cells and Figure 5B showing NPC-S26 cells, as assessed in Example 3.

[0062] Figure 6 shows the cell morphology results (magnification, 20X) from Example 3, with Figure 6A showing the HCT-116 cells, Figure 6B showing the SW620 cells, Figure 6C showing the NPC-6-108 cells and Figure 6D showing the NPC-S26 cells

[0063] Figures 7 to 12 explore the interaction between the various components of the metal complex of the invention as described in Example 5.

[0064] Figure 7 shows the interaction between metal (Mg) and the DTA in a Mg-DTA complex.

[0065] Figure 8 shows the interaction between decitabine (DCA) and Mg-DTA in a Mg-DTA- decitabine complex.

[0066] Figure 9 shows the interaction between metal (Mg) and the SA in a Mg-SA complex.

[0067] Figure 10 shows the interaction between metal (Mg) and the DTA and SA in a Mg- DTA / SA complex. Figure 11 shows the interaction between decitabine (DCA) and Mg-DTA / S A in a Mg- DTA / SA-decitabine complex.

[0068] Figure 12 shows the interaction between Mg and decitabine (DCA).

[0069] Figure 13 shows the FTIR analysis of a Mg-DTA metal complex comprising decitabine. Figure 14 shows the XRD results of a Mg-DTA metal complex comprising decitabine.

[0070] DETAILED DESCRIPTION

[0071] The present invention is concerned with a metal complex comprising: (a) a pharmaceutically acceptable central metal; (b) a DNA methyltransferase (DNMT) inhibitor; and (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA). Optionally, the metal complex may further comprise (d) a cytidine deaminase (CD A) inhibitor.

[0072] The metal complex may consist of components (a) to (c) and, where present (d). Alternatively, the metal complex may consist essentially of components (a) to (c) and, where present (d). Thus, in some aspects the metal complex consists or consists essentially of components (a) to (c). In other aspects the metal complex consists or consists essentially of components (a) to (d). By “consist essentially”, it is mean that at least 95% by weight, preferably at least 97% by weight and more preferably at least 99% by weight of the metal complex is components (a) to (c) and, where present (d), based on the total weight of the metal complex.

[0073] The pharmaceutically acceptable central metal

[0074] The pharmaceutically acceptable central metal is typically selected from those that are FDA-approved in medical application, such as Li, Mg, Al, K, Ca, Fe, Co, Ga, As, Sr, Y, Zr, Pd, Ag, Sb, Sm, Lu, Pt, Au, Hg, Bi, and Ra. Preferably the pharmaceutically acceptable central metal is Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni or Zn

[0011] , and more preferably the pharmaceutically acceptable central metal is Mg, Fe, Co or Zn. Mg is particularly preferred.

[0075] The metal complexes of the invention may contain a single type of metal or may contain two or more, for example two, different metals. A single metal (such as Mg) is preferred.

[0076] The pharmaceutically acceptable central metal atom is typically selected such that it interacts with the other components of the metal complex, and in particular the DNMT inhibitor and / or the 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA) and (where present) the CDA inhibitor, and preferably with all of these components. Typically, the interaction is by way of coordinate bonds. In other words, it is preferable that the DNMT inhibitor, 2,5-dihydroxyterephthalic acid (DTA), syringic acid (SA) and (where present) the cytidine deaminase (CDA) inhibitor are ligands to the pharmaceutically acceptable central metal atom in the metal complex.

[0077] The DNA methyltransferase (DNMT) inhibitor

[0078] DNA methyltransferases (DNMTs) are enzymes responsible for maintaining and propagating DNA methylation patterns in proliferating cells

[0018] , DNMTs include DNMT1, DNMT3A and DNMT3B. DNMT inhibitors, such as decitabine, typically target one or more of DNMT 1, DNMT3A and DNMT3B, preferably at least DNMT1, and more preferably all of DNMT1, DNMT3A and DNMT3B. The ability of a given compound to act as a DNMT inhibitor can be easily assessed by a skilled person using techniques well known to those of skill in the art.

[0079] The DNMT inhibitors used in the present invention are typically ligands for the pharmaceutically acceptable central metal, and thus coordinate to the pharmaceutically acceptable central metal. The interaction of the DNMT inhibitor with the pharmaceutically acceptable central metal may result in a sustained release / effect of the DNMT inhibitor when administered as a metal complex of the invention.

[0080] Typically, the DNMT inhibitor is an inhibitor of DNMT1 (i.e. is a DNMT1 inhibitor). Typically, the DNMT inhibitor is capable of acting as a ligand. Optionally, the DNMT inhibitor forms a stable metal complex.

[0081] Typically, the DNMT inhibitor is a nucleoside DNMT inhibitor. Preferably, the nucleoside DNMT inhibitor is azacytidine, decitabine, zebularine and guadecitabine (SGI- 110).

[0082] Typically, the DNMT inhibitor is a non-nucleoside DNMT inhibitor. Preferably, the non-nucleoside DNMT inhibitor is procaine, MG98, RG108 and hydralazine.

[0083] Typically, the DNMT inhibitors used in the present invention comprise at least one of a hydroxyl group, an amine group and a carboxyl group. These functional groups are generally important in order to allow coordination with the pharmaceutically acceptable central metal. Typically, the DNMT inhibitor is azacytidine, decitabine, zebularine, guadecitabine (SGI-110), procaine, MG98, RG108 and hydralazine. Preferably, the DNMT inhibitor is decitabine or azacytidine. Most preferably, the DNMT inhibitor is decitabine.

[0084] The DNMT inhibitors may be used in the form of pharmaceutically acceptable salts, such as pharmaceutically acceptable salts of decitabine or azacytidine, but are typically not in the form of pharmaceutically acceptable salts. As used herein, a pharmaceutically acceptable salt is a salt with a pharmaceutically acceptable acid or base. Pharmaceutically acceptable acids include both inorganic acids such as hydrochloric, sulphuric, phosphoric, diphosphoric, hydrobromic or nitric acid and organic acids such as citric, fumaric, maleic, malic, ascorbic, succinic, tartaric, benzoic, acetic, methanesulphonic, ethanesulphonic, benzenesulphonic or p- toluenesulphonic acid. Pharmaceutically acceptable bases include alkali metal (e.g. sodium or potassium) and alkali earth metal (e.g. calcium or magnesium) hydroxides and organic bases such as alkyl amines such as meglumine, aralkyl amines or heterocyclic amines.

[0085] The metal complexes of the invention may contain a single DNMT inhibitor or may contain more than one, such as two, DNMT inhibitors (e.g. a mixture of decitabine and azacytidine). A single DNMT inhibitor is preferred.

[0086] 2,5-dihydroxyterephthalic acid (DTA) and syringic acid (SA)

[0087] The metal complex of the present invention comprises 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA). These compounds are associated with very low toxicity, and so are particularly suited to pharmaceutical use.

[0088] The metal complexes may comprise only DTA (and not SA) or may comprise only SA (and not DTA) or may comprise both DTA and SA, but it is preferable that the metal complexes comprise DTA.

[0089] DTA and SA can conveniently be sourced from Chaga mushroom (Inonotus obliquus) extracts. In particular, as discussed above, DTA and SA are two of seven identified components of Chaga mushroom extracts. Chaga mushroom extracts can therefore be used to prepare metal complexes of the invention in an environmentally friendly (i.e. “green” manner).

[0090] Accordingly, by contacting a Chaga mushroom extract with a pharmaceutically acceptable central metal atom, and then washing the resulting mixture, a metal complex comprising the pharmaceutically acceptable central metal, DTA and SA is generally obtained, with DTA and SA typically coordinated to the pharmaceutically acceptable central metal as ligands. The other components, which do not tend to coordinate to the pharmaceutically acceptable central metal, are generally removed during washing.

[0091] It is thus preferred that the DTA and / or SA are derived from a Chaga mushroom extract.

[0092] CDA inhibitors

[0093] The metal complexes may optionally further comprise a cytidine deaminase (CDA) inhibitor.

[0094] Cytidine deaminase (CDA) is a ubiquitous enzyme involved in the recycling of free pyrimidines

[0019] , Inhibition of CDA improves the oral bioavailability of DNMT inhibitors. Cedazuridine, an exemplary CDA inhibitor, is often co-administered with hypomethylating agents such as decitabine. It is therefore preferable that the metal complexes of the present invention further comprise a CDA inhibitor. The ability of a given compound to act as a CDA inhibitor can be easily assessed by a skilled person using techniques well known to those of skill in the art.

[0095] The metal complexes of the invention may contain a CDA inhibitor or may contain more than one, such as two, CDA inhibitors). A single CDA inhibitor is preferred.

[0096] The CDA inhibitors used in the present invention are typically ligands for the pharmaceutically acceptable central metal, and thus coordinate to the pharmaceutically acceptable central metal.

[0097] Preferably the CDA inhibitor is cedazuridin. Preferably, when cedazuridin is present, the DNMT inhibitor is decitabine.

[0098] The metal complexes

[0099] The metal complex of the present invention comprises a pharmaceutically acceptable central metal atom as described above. Typically, the DNMT inhibitor, DTA / SA and (where present) the CDA inhibitor are coordinated to the pharmaceutically acceptable central metal atom via coordinate bonds (i.e. the DNMT inhibitor and DTA / SA and CDA inhibitor act as ligands). In particular, as discussed above, the DNMT inhibitor, DTA, SA, and CDA inhibitor have functional groups that are suitable for forming coordinate bonds with the pharmaceutically acceptable central metal atom. The presence of coordinate bonds can be determined by techniques well known to those of skill in the art. For example, routine spectroscopic techniques such as UV-Vis spectroscopy may be used, as described below in the Examples.

[0100] An advantage of the metal complex of the present invention, as demonstrated in the Examples, is that stability of the DNMT inhibitor, such as decitabine, is increased, particularly at room temperature. In addition, as also demonstrated in the Examples, sustained release of DNMT inhibitor is also possible.

[0101] The metal complex may be in particulate form and further comprise a shell. The shell thus surrounds and encapsulates the particle of metal complex. In some instances, a shell may be absent. However, in other instances it may be preferable for the shell to be present.

[0102] Excluding any components forming the shell (when present), the preferred percentages by weight of each component of the metal complex based on the total weight of the metal complex are:

[0103] (a) 1-10% pharmaceutically acceptable central metal;

[0104] (b) 82 - 98% DNA methyltransferase (DNMT) inhibitor; and

[0105] (c) 1 - 8% 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA).

[0106] When present, the shell may comprise any material that is suitable for pharmaceutical applications, but preferably the shell comprises a liposome, polyethylene glycol-modified liposomes, biopolymer, a cell membrane or a peptide. For instance, the shell may comprise a biopolymer, a cell membrane or a peptide. The shell material can be selected to enhance the advantages of the metal complex of the invention.

[0107] Liposome: The liposomes are typically formed of phospholipids (e.g., phosphatidylcholine) and cholesterol, forming a concentric bilayer vesicle structure. They can be multilamellar vesicles (MLVs), small unilamellar vesicles (SUVs), or large unilamellar vesicles (LUVs).

[0108] Polyethylene glycol-modified liposomes (PEGylated liposomes): These liposomes incorporate an amphipathic lipid derivatized with a polyalkylether, such as phosphatidylethanolamine derivatized with PEG. The PEG coating, often referred to as a hydrophilic polymer chain surface coating, enhances the stability and prolongs the circulation time of the liposomes in the body by reducing immune system recognition.

[0109] Biopolymer shells typically improve the biocompatibility of the encapsulated nanoparticle, and more generally protect the nanoparticle and can allow for targeted release. The biopolymer is typically chitosan, Alginate, Ascorbyl palmitate (AP), Carboxymethyl Cellulose (CMC), Hyaluronic Acid (HA), Polyacrylic Acid (PAA), Phosphate-Modified Polymers, Polyglutamic Acid (PGA) liposomes, albumin, or polymeric micelles. Chitosan and Ascorbyl palmitate are preferred. Typically, when the shell is chitosan or ascorbyl palmitate, the weight ratio of chitosan or ascorbyl palmitate to metal complex is 1-3: 1.

[0110] Cell membrane shells typically improve the biocompatibility, targeting specificity and side effect profile of the encapsulated nanoparticle. Typically, the cell membrane is sourced from blood cells, immune cells and macrophages-natural macrophages extracted from bone marrow, peripheral blood, peritoneal cavity, tumour-associated macrophages, established macrophages cell lines, and genetically engineered macrophages, tumour cells, cancer stem cells, mesenchymal stem cells, and eukaryotic cells. Cell membranes from cancer cells are preferable. An example is a cell membrane from a colorectal cancer cell line (e.g. HCT-116). Typically, the weight ratio of cell membrane to metal complex is 1-2: 1.

[0111] Peptide shells are typically cell penetrating peptide shells, in particular histidine-rich cell penetrating peptides. Typically, such shells enhance delivery of the nanoparticles to the target cancer cells. In particular, positively charged histidine residues faced outward, facilitating direct translocation of nanoparticles through the negatively charged cancer cell membrane via electrostatic interactions. The histidine residues also contribute to stability of the nanoparticles when dissolved in water, to achieve a highly stable water-soluble nanoparticle. Typically, the weight ratio of histidine-rich cell penetrating peptide to metal complex is 1 : 8-20.

[0112] Processes and intermediates

[0113] The metal complexes of the invention are typically prepared by (i) contacting a source of the pharmaceutically acceptable central metal, such as a salt of the pharmaceutically acceptable central metal, with a source of the DTA and / or SA, and then (ii) contacting the resulting intermediate metal complex with the DNMT inhibitor, thereby to provide the metal complex of the invention.

[0114] Step (i) is typically carried out at room temperature (i.e. 22-25 °C) for about 24 hours. Alternatively, step (i) can be conducted using microwave radiation for less than two minutes. In both instances, no toxic reagents are needed, nor is conventional heating required, which makes the process environmentally friendly.

[0115] The intermediate metal complex comprising the pharmaceutically acceptable central metal and DTA and / or SA is then typically separated from any reaction solvents, for example by filtration, and washed with suitable solvents, such as ethanol and deionized H2O. The precipitate can then be dried using conventional techniques to give a powder.

[0116] Step (ii) generally involves an initial step of preparation of a solution of the DNMT inhibitor. Any suitable solvent may be used, such as methanol, DMSO or ethanol. The solution of the DNMT inhibitor is then contacted with the intermediate metal complex comprising the pharmaceutically acceptable central metal and DTA and / or SA from step (i), which results in formation of the metal complex of the invention.

[0117] As discussed above, the DTA and / or SA is conveniently obtained from a Chaga mushroom extract. Thus, the source of DTA and / or SA is typically a Chaga mushroom extract. The Chaga mushroom extract can be prepared by conventional techniques, such as contacting a powder of dried Chaga mushroom with water and / or ethanol, and subsequently removing the solid organic matter to provide a solution from which solvent can be removed to give the extract. The extract typically contains DTA and SA. Thus, a metal complex of the invention prepared using a Chaga mushroom extract will generally contain both DTA and SA, with other components of the extract being washed away during the synthetic process.

[0118] The intermediate metal complex comprising the pharmaceutically acceptable central metal and DTA and / or SA prepared following step (i) is a useful synthetic intermediate. Thus, the present invention also relates to an intermediate metal complex comprising (a) the pharmaceutically acceptable central metal, and (c) DTA and / or SA. The intermediate metal complex may comprise (a) the pharmaceutically acceptable central metal, and (c) DTA and SA, particularly if it has been prepared using a Chaga mushroom extract. Alternatively, the intermediate metal complex may comprise (a) the pharmaceutically acceptable central metal, and (c) DTA. Alternatively, the intermediate metal complex may comprise (a) the pharmaceutically acceptable central metal, and (c) SA. These intermediate metal complexes may be used as synthetic intermediates in the preparation of a metal complex of the invention.

[0119] An intermediate metal complex comprising (a) the pharmaceutically acceptable central metal and (b) a DNA methyltransferase (DNMT) inhibitor is also a useful synthetic intermediate, and can be prepared by analogy with the steps set out above. These intermediate metal complexes may be used as synthetic intermediates in the preparation of a metal complex of the invention.

[0120] Typically, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (b) a DNA methyltransferase (DNMT) inhibitor, the pharmaceutically acceptable central metal of the intermediate metal complex is Li, Mg, Al, K, Ca, Fe, Co, Ga, As, Sr, Y, Zr, Ag, Sb, Sm, Lu, Pt, Au, Hg, Bi, and Ra, preferably Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni or Zn. Typically, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (b) a DNA methyltransferase (DNMT) inhibitor, the pharmaceutically acceptable central metal of the intermediate metal complex is not Pd.

[0121] Typically, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (b) a DNA methyltransferase (DNMT) inhibitor, the DNMT inhibitor of the intermediate metal complex is capable of acting as a ligand, optionally, the DNMT inhibitor forms a stable metal complex, preferably the DNMT inhibitor is decitabine or azacytidine, most preferably the DNMT inhibitor is decitabine.

[0122] Typically, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (b) a DNA methyltransferase (DNMT) inhibitor, the DNMT inhibitor is not procaine.

[0123] Typically, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA), the pharmaceutically acceptable central metal of the intermediate metal complex is Li, Mg, Al, K, Ca, Fe, Co, Ga, As, Sr, Y, Zr, Pd, Ag, Sb, Sm, Lu, Pt, Au, Hg, Bi, and Ra, preferably Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni or Zn, more preferably Mg, Fe, Co or Zn, most preferably Mg.

[0124] In an embodiment, when the intermediate metal complex comprises (a) a pharmaceutically acceptable central metal and (c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA), the pharmaceutically acceptable central metal of the intermediate metal complex is preferably Ca or Ba. The intermediate metal complexes discussed above may be also be useful in their own right as active pharmaceuticals, for example for use in treating the cancers described herein.

[0125] If it is desired to add a shell to the metal complexes of the invention, then this can be achieved using any suitable method, for example as further described below in Example 4.

[0126] Pharmaceutical compositions

[0127] Pharmaceutical compositions comprise the metal complex of the invention and one or more pharmaceutically acceptable excipients or carriers.

[0128] Given that the metal complexes of the invention are preferably in nanoparticulate form with a size of < 200 nm, they can be administered intravenously (IV or i.v.), subcutaneously (SQ or s.q.), intracutaneously (IC or i.c.), intramuscularly (IM or i.m.), intraperitoneally (IP or i.p.) or oral (OP or o.p.). Accordingly, pharmaceutical compositions suitable for these particular routes of administration will be selected as appropriate.

[0129] For administration by injection (i.e. IV, SQ, IC, IM or iP), the pharmaceutical compositions typically take the form of an aqueous injectable solution. Examples of suitable aqueous carriers that may be employed in the injectable pharmaceutical compositions of the invention include water, buffered water and saline. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, or sodium chloride in the composition.

[0130] For oral administration, the pharmaceutical compositions of the present invention may take the form of, for example, tablets, lozenges or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methyl cellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogenphosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycolate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents, emulsifying agents, non-aqueous vehicles or preservatives. The preparations may also contain buffer salts, flavouring agents, colouring agents or sweetening agents, as appropriate. Pharmaceutical compositions of the invention may be prepared by any suitable method known to those of skill in the art.

[0131] Treatment of cancer

[0132] The metal complexes and pharmaceutical compositions of the invention may be used for the treatment of the human or animal body. Preferably the metal complexes and pharmaceutical compositions of the invention are used for the treatment of humans.

[0133] As discussed above, the metal complexes are associated with a number of advantages that make them particularly useful as therapeutics. Of particular interest is synergistic interact between the DNMT inhibitor and the DTA / SA, the wide range of cancers the metal complex can treat and longer effective period of those treatments.

[0134] Thus, preferably, the metal complexes and pharmaceutical compositions of the invention are used in methods of treating cancer.

[0135] Typically, the cancer is lung squamous cell carcinoma, kidney papillary carcinoma, clear cell kidney carcinoma, breast ductal carcinoma, renal cell carcinoma, cervical cancer (squamous), colorectal cancer (colon adenocarcinoma and / or rectal carcinoma), stomach adenocarcinoma, hepatocellular carcinoma, Head and neck (oral) squamous cell carcinoma, thyroid carcinoma, bladder urothelial carcinoma - nonpapillary, uterine corpus (endometrial carcinoma), pancreatic ductal adenocarcinoma, myelodysplastic syndromes, acute myeloid leukemia, chronic myelomonocytic leukemia, prostate adenocarcinoma, lung adenocarcinoma, cutaneous melanoma, breast lobular carcinoma and lower grade glioma, esophageal carcinoma, ovarian serous cystadenocarcinoma, lung squamous cell carcinoma, adrenocortical carcinoma, Diffuse Large B-cell lymphoma, paraganglioma & pheochromocytoma, cholangiocarcinoma, uterine carcinosarcoma, uveal melanoma, thymoma, sarcoma, mesothelioma, testicular germ cell cancer or nasopharyngeal carcinoma.

[0136] Preferably the cancer is colorectal cancer (which may be colon adenocarcinoma and / or rectal carcinoma), nasopharyngeal carcinoma, myelodysplastic syndromes, acute myeloid leukemia or chronic myelomonocytic leukemia. More preferably the cancer is colorectal cancer (which may be colon adenocarcinoma and / or rectal carcinoma) or nasopharyngeal carcinoma. Dosages and modes of administration

[0137] Determination of the appropriate mode of administration and / or dosage for particular situations may easily be determined by a skilled medical practitioner.

[0138] Actual dosage levels of may be varied so as to obtain an amount of the active ingredient, which is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration, without being toxic to the patient. The selected dosage level will depend upon a variety of pharmacokinetic factors including the activity of the particular metal complex / pharmaceutical composition of the present invention employed, the route of administration, the time of administration, the rate of excretion of the particular compound being employed, the duration of the treatment, other drugs, compounds and / or materials used in combination with the particular compositions employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts.

[0139] Dosage regimens may be adjusted to provide the optimum desired response. For example, a single dose may be administered, several divided doses may be administered over time or the dose may be proportionally reduced or increased as indicated by the exigencies of the therapeutic situation. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subjects to be treated; each unit contains a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier.

[0140] Administration may be in single or multiple doses. Multiple doses may be administered via the same or different routes and to the same or different locations. Dosage and frequency may vary depending on the half-life of the drugs in the patient and the duration of treatment desired.

[0141] EXAMPLES

[0142] The present invention is explained in more detail in the following by referring to the Examples, which are not to be construed as limiting. Example 1 - Preparation of metal complex

[0143] Initially, Chaga mushroom extracts were prepared, which are sources of SA and DTA, by alcoholic extraction. The alcoholic extraction involved the following steps:

[0144] 1. Dried Chaga mushroom was ground using a mortar and pestle. 30-50g of Chaga powder dissolved in 300-500 ml of proof grain alcohol and left for 30-45 days, at room temperature.

[0145] 2. Contact of the solution with air was avoided and it shaken 3-5 times per week, to ensure the mixture was thoroughly reacted.

[0146] 3. The extract was separated from the organic matter via filtration.

[0147] 4. A rotary evaporator was used to further evaporate the rest liquid from the extract, over a period of at least 36 hours. All samples were stored at -20°C upon preparation.

[0148] The metal complex was then prepared in the following manner.

[0149] (i) The synthesis of a metal-Chaga extract intermediate complex was conducted using the Chaga mushroom extract and one pharmaceutically accepted metal, namely Mg. a) > 0.5 parts of the Chaga mushroom extract was chemically reacted with 1 part of the pharmaceutically accepted metal (Mg) in salt form. b) In detail, the synthetic process was performed either at room temperature 22-25 °C for 24 hours or using microwave radiation for less than 2 minutes, without the use of toxic chemical reagents or of conventional heating. c) Subsequently, the precipitate was isolated via filtration and washed three times each with ethanol and deionized H2O. d) Finally, the precipitate was dried to provide a powder of the metal-Chaga extract intermediate complex.

[0150] (ii) The DNMT inhibitor, namely decitabine, was dissolved into methanol or DMSO or ethanol, to a concentration of 20-80 mg / 100 ml (weight / volume, w / v). Then it was mixed thoroughly at room temperature. Concentration (w / v) = (Amount of solute (mg) / Volume of solvent (ml)) * 100.

[0151] (iii) The solution from (ii) was dropped onto the metal-Chaga extract intermediate complex from (i) to synthesise the final metal complex. Commercially purchased DTA and SA were used for the synthesis of the Mg-DTA- Decitabine and Mg-SA-Decitabine. The X-ray powder diffraction (XRD) result of the Mg- DTA-Decitabine metal complex is shown in the Figure 1A, which is associated with the reflection electron microscopy images of those metal complex. Moreover, the XRD result of Mg-SA-Decitabine metal complex is shown in the Figure IB, which is associated with scanning electron microscopy images of those metal complex.

[0152] Example 2 - Advantages of metal complex: avoiding drug hydrolysis and extension of drug release

[0153] (i) The formation of the metal complex protects the DNMT inhibitor drug from hydrolysis UV-Visible spectrophotometric method was used to detect the absorbance of decitabine.

[0154] The effective and sensitive measurable wavelength of decitabine is at 284 nm in ddH2O and pH2 HC1. Standard calibration curves of decitabine in ddH2O are shown in Figure 2A; standard calibration curve of decitabine in pH2 HC1 are shown in Figure 2B.

[0155] The present invention allows for a stable and long-term preservation of decitabine at room temperature. Table 1 shown the UV spectrophotometric measurement results of fresh prepared decitabine solution and the metal complex containing decitabine > 30 days after synthesis, and confirms that there is no reduction in decitabine concentration when formulated in the metal complex. It is well known that decitabine is unstable in water - the EMA product information for decitabine (marketed as Dacogen) states that reconstituted solutions of decitabine can be stored at 2-8°C for a maximum of 3 hours, in view of instability.

[0156] Table 1

[0157] Fresh prepared Decitabine (Cone. 40 pM) 5.72 5.70 5.73

[0158] Metal complex >30 days

[0159] (containing decitabine with Cone. 40 pM) 5.82 5.98 5.99 Cone.: concentration

[0160] (ii) The metal complex potentially allows for extended decitabine drug release

[0161] The inventors employed optical detection methods to perform quantitative analysis and identification of decitabine in a solution of the metal complex. In particular, a Mg-DTA- Decitabine metal complex was dissolved in 0.9% NaCl solution at 5 mg / ml, and Decitabine levels were assessed over a period of 60 hours at room temperature. The results are shown in Figure 3, from which it is clear that the proportion of decitabine remaining in the metal complex decreases from 100% to between 70% and 80% over 60 hours.

[0162] Example 3 - Therapeutic uses on cancer cells

[0163] Various cancer cell lines were treated with (a) a blank control, (b) decitabine at concentration at 0.5 pM, (c) a metal (Mg) and DTA complex (without decitabine), and (d) a metal complex with decitabine, Mg and DTA. The metal complex with decitabine showed strong and long-term anti-proliferation efficacy, following 7 days treatment, as compared to the other treatments. The metal complexes according to the invention can therefore be used as nanomedicines to treat cancers, such as those described above.

[0164] (i) Cancer cell preparation: Two distinct colon adenocarcinoma cell lines and two distinct nasopharyngeal carcinoma cell lines were used to evaluate the effectiveness of the NMC in inhibiting cancer cell proliferation.

[0165] (ii) Treatments: For the in vitro experiments, four treatment groups were established, including blank control, decitabine 0.5 pM, metal and Chaga extract complex and metal complex containing decitabine. Treatments were administered according to a time-dependent regime from Day 0 to Day 7.

[0166] (iii) Methods: Following daily treatments on the cancer cells, MTT assays were conducted to assess the viability of the living cells.

[0167] (iv) Effect evaluation: Finally, the relative OD value represents the living cells following diversity treatments was calculated. Figure 4 shows the results of MTT assays of human colorectal cancer cells, with Figure 4A showing HCT-116 cells and Figure 4B showing SW620 cells. Figure 5 shows the results of MTT assays of human nasopharyngeal carcinoma cells, with Figure 5A showing NPC-6-108 cells and Figure 5B showing NPC-S26 cells.

[0168] (v) Furthermore, the cell morphology evaluation by scanning electron microscopy was performed on those different cancer cells, following 4 days treatments with blank control, decitabine 0.5 pM, metal and Chaga extract complex and metal complex containing decitabine. Figure 6 shows the cell morphology results (magnification, 20X), with Figure 6A showing the HCT-116 cells, Figure 6B showing the SW620 cells, Figure 6C showing the NPC-6-108 cells and Figure 6D showing the NPC-S26 cells.

[0169] (vi) In conclusion, the cell viability assays demonstrated that over a 7-days period, the metal complex of the present invention shown a synergistic effect in inhibiting cancer cell proliferation. Moreover, the “metal and Chaga extract complex” does not impact the cell viability, indicating the safety profile of its components.

[0170] Although, decitabine is approved for the treatment of haematologic malignancies, the inventors also show efficacy against solid tumours in models of human colorectal cancer and nasopharyngeal carcinoma.

[0171] Example 4 — shell coatings for NMCs (Chitosan, cell membrane, peptide)

[0172] Three different types of shells coating, namely chitosan, cell membrane and peptide, were applied to the metal complex containing decitabine, Mg and DTA.

[0173] (i) Chitosan coating for the metal complex:

[0174] A metal complex with chitosan shell with a particle size less than 200 nm, which is one important characteristic for pharmaceutical application, was prepared. Chitosan can have various functional groups - hydroxyl-groups, amine-groups and carboxyl -groups - which can enhance the metal complex’s biocompatibility and chemically reaction through covalent bonding. a) Chitosan with pharmaceutical primary standard was dissolved at 1 percent (weight / volume) in acetic acid. b) The solution was adjusted to pH to 4 - 6 and then stirred for 18-24 hours. c) The metal complex was dissolved in the chitosan solution at a 1 : 1 ratio, (volume / volume), then the mixture was rotated at 100-150 rpm for 1-1.5 hours, at 37-50 °C. d) After incubation, the suspension of chitosan coated metal complex was centrifuged at 10,000g for 15 minutes, then freeze dried.

[0175] (ii) Cell membrane coating for the metal complex:

[0176] Cell membranes may improve the biocompatibility, targeting specificity and side effect profile. The inventors coated the metal complex with cell membranes, while retaining a particle size less than 200 nm. The source cells were primary human colorectal cancer (CRC) cells, which have potential for immunotherapy

[0020] , HCT-116 cells were used as resourcing membrane. a) Cell membranes were collected by harvesting empty cells using differential centrifugation, hypotonic lysing, and mechanical membrane disruption. b) Cell membrane vesicles were prepared using physical extrusion in preparation of coating the metal complex. c) 10 mg of metal complex was mixed into the chitosan solution in 10 ml PBS solution, cell membrane vesicles were added into the PBS solution, then the spontaneous formation of a cell membrane coated metal complex suspension proceeded. d) A 200 nm porous polycarbonate membrane was used to extract the metal complex, which was coated with cell membrane, and the coated metal complex was then freeze dried.

[0177] (iii) Cell penetrating peptides coating for the metal complex

[0178] A coating of cell-penetrating peptides was used to enhance delivery of the metal complex to cancer cells. The positively charged histidine residues faced outward, facilitating the direct translocation of metal complex through the negatively charged cancer cell membrane via electrostatic interactions. The histidine residues also contribute to stability of the metal complex when dissolved in water, to achieve a highly stable water-soluble metal complex. a) The cell-penetrating peptides and the metal complex were mixed at with a weight ratio of 1 :8-20. b) The mixed mixture from step “a”, was dissolved in DMEM cell culture medium, then incubated at 37 °C in a thermomixer for 20 min at 300 rpm, then freeze dried.

[0179] Example 5 — interactions between components of metal complex To investigate the interaction between the components of complexes of the invention, the inventors performed UV-Vis (UV-visible) spectra of suspensions of metal (Mg) and DTA / SA complexes. The UV-Vis spectra confirmed the stability of Mg-DTA complex particles. A typical Mg-DTA absorption was observed between 300-320 nm, with peak maxima centred at 316 nm, indicating the signature of surface plasmon resonance (SPR) band of the Mg-DTA complex. These results are presented in Figure 7.

[0180] As described in Example 2, UV-Vis spectra successfully established the standard curve of decitabine across various concentrations. As shown in Figure 2A and 2B, the peak absorbance of the decitabine either in both deionized water and HC1 (pH2) occurs at about 284 nm. No non-bonding electrons were detected within the spectrometer’s measurable range.

[0181] The interaction between various components in the metal complex containing decitabine was also successfully detected using UV-visible absorption spectra. The results, as shown in Figure 8 indicate a peak absorbance at approximately 284 nm, corresponding to the decitabine component, and another peak at 316 nm, corresponding to the interaction between the magnesium and the DTA. These results suggest that the binding energy falls within the UV-visible range. The line provides evidence of the binding interaction between decitabine and the pharmaceutically acceptable central metal and DTA. Similarly, the interaction between magnesium and SA in the metal complex was detected using UV-visible absorption spectra. The results, as shown in Figure 9. The interaction between magnesium and the combination of DTA and SA in a metal complex was detected using UV-visible absorption spectra and shown in Figure 10. Additionally, the interactions in a metal complex of magnesium, DTA, SA and decitabine was shown in Figure 11. The interaction between magnesium and decitabine in the metal complex was shown in Figure 12.

[0182] Example 6 — The decitabine percentage of Mg-DTA metal complex

[0183] According to the synthetic method of Example 1, we prepared the intermediate metal complex of commercially purchased 2,5-dihydroxyterophthalic (DTA) and magnesium nitrate hexahydrate (Mg(NOs)2 • 6 H2O). Detailed below: a) 1-10% weight ratio of magnesium nitrate hexahydrate (Mg(NCh)2 • 6 H2O) serves as the central metal; b) 1-8% weight ratio of 2,5-dihydroxyterophthalic (DTA) serves as the linker; c) Organic solution containing of ethanol, N, N-Dimethylformamide (DMF) and deionized water is used to dissolve the above magnesium nitrate hexahydrate (Mg(N0s)2 • 6 H2O) and DTA, thoroughly. d) The reaction system is set at 20-150 °C and the reaction is continued for at least 2 hours. e) Decitabine as the epigenetic agent is used and associated with the Mg-DTA. The component percentage of decitabine in Mg-DTA metal complex has a weight ratio range from 0.1 : 1 to 1.5: 1, under room temperature (22-24 °C), the reaction is continued for at least 2 hours.

[0184] Tests of FTIR, element analysis (EA) and XRD are used to detect the associated functional groups, properties, and the component percentage of decitabine within a Mg-DTA metal complex. Figure 13 shows the FTIR results of the decitabine associated with the Mg-DTA metal complex. Figure 14 shows the XRD results of the decitabine associated with the Mg- DTA metal complex.

[0185] Decitabine has the molecular formula C8H12N4O4. Therefore, the component percentage of decitabine of the Mg-DTA metal complex in our present invention is calculated by the percentage of N element in the entire Mg-DTA metal complex. The EA result of Mg-DTA metal complex comprising decitabine is shown in Table 2. The average component percentage of decitabine in two probes of Mg-DTA metal complex is 57.34%, which according to the result of N% with 14.22% and 14.14% from EA results.

[0186] Table 2. The CHNS-Element analysis (EA) results of decitabine associated with the Mg-DTA metal complex.

[0187] Standard sample test 16.26 % 41.85 % 4.68 % 18.62 % 26.2 %

[0188] Mg-DTA metal complex comprising decitabine_ 14.22 % 34.32 % 4.648 % 0.266 % 0 % probe 1

[0189] Mg-DTA metal complex comprising decitabine_ 14.14 % 34.11 % 4.680 % 0.216 % 0 % probe 2 The following document have been cited in the preceding text, and the content of each document is hereby incorporated by references in its entirety.

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Claims

CLAIMS1. A metal complex comprising:(a) a pharmaceutically acceptable central metal;(b) a DNA methyltransferase (DNMT) inhibitor; and(c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA).

2. The metal complex according to claim 1, wherein the DNMT inhibitor is decitabine or azacytidine, and is preferably decitabine.

3. The metal complex according to claim 1 or 2, wherein the pharmaceutically acceptable central metal is Li, Mg, Al, K, Ca, Fe, Co, Ga, As, Sr, Y, Zr, Pd, Ag, Sb, Sm, Lu, Pt, Au, Hg, Bi, and Ra, preferably Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni or Zn.

4. The metal complex according to any preceding claim, which comprises(i) DTA; or(ii) SA; or(iii) DTA and SA.

5. The metal complex according to any preceding claim, which further comprises a cytidine deaminase (CD A) inhibitor comprising at least one of, preferably wherein the CDA inhibitor is cedazuridin.

6. The metal complex according to any preceding claim, wherein the DNMT inhibitor, the DTA and / or SA, and, where present, the CDA inhibitor interact with, and are preferably coordinated to, the pharmaceutically acceptable central metal.

7. The metal complex according to any preceding claim, which comprises the following percentages by weight of each component, based on the total weight of the metal complex:(a) 1-10% pharmaceutically acceptable central metal;(b) 82 - 98% DNA methyltransferase (DNMT) inhibitor; and(c) 1 - 8% 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA).

8. The metal complex according to any preceding claim, wherein the metal complex is in the form of particles and the particles further comprise a shell, preferably wherein the shell comprises at least one material selected from the group consisting of a liposome, polyethylene glycol-modified liposomes, biopolymer, a cell membrane or a peptide.

9. The metal complex according to any preceding claim, which further comprises one or more pharmaceutically acceptable components, wherein preferably said one or more pharmaceutically acceptable components interact with the pharmaceutically acceptable central metal and more preferably said one or more pharmaceutically acceptable components are coordinated to the pharmaceutically acceptable central metal.

10. A pharmaceutical composition comprising the metal complex according to any preceding claim and one or more pharmaceutically acceptable excipients or carriers.

11. The metal complex according to any one of claims 1 to 9 or the pharmaceutical composition according to claim 10 for use as a medicament, preferably for use in a method of treating cancer, typically wherein the cancer is lung squamous cell carcinoma, kidney papillary carcinoma, clear cell kidney carcinoma, breast ductal carcinoma, renal cell carcinoma, cervical cancer (squamous), colorectal cancer (colon adenocarcinoma and / or rectal carcinoma), stomach adenocarcinoma, hepatocellular carcinoma, Head and neck (oral) squamous cell carcinoma, thyroid carcinoma, bladder urothelial carcinoma - nonpapillary, uterine corpus (endometrial carcinoma), pancreatic ductal adenocarcinoma, myelodysplastic syndromes, acute myeloid leukemia, chronic myelomonocytic leukemia, prostate adenocarcinoma, lung adenocarcinoma, cutaneous melanoma, breast lobular carcinoma and lower grade glioma, esophageal carcinoma, ovarian serous cystadenocarcinoma, lung squamous cell carcinoma, adrenocortical carcinoma, Diffuse Large B-cell lymphoma, paraganglioma & pheochromocytoma, cholangiocarcinoma, uterine carcinosarcoma, uveal melanoma, thymoma, sarcoma, mesothelioma, testicular germ cell cancer or nasopharyngeal carcinoma, preferably wherein the cancer is colon adenocarcinoma, rectal carcinoma, nasopharyngeal carcinoma, myelodysplastic syndromes, acute myeloid leukemia or chronicmyelomonocytic leukemia, more preferably wherein the cancer is colon adenocarcinoma, rectal carcinoma or nasopharyngeal carcinoma.

12. A method of treating cancer as defined in claim 11, which comprises administering the metal complex according to any one of claims 1 to 9 or the pharmaceutical composition according to claim 10 to a subject having said cancer.

13. A process for preparing a metal complex as defined in any one of claims 1 to 9, the method comprising:(i) contacting a source of a pharmaceutically acceptable central metal as defined in claim 1 or 3 with a source of the DTA and / or SA to form an intermediate metal complex, and(ii) contacting the resulting intermediate metal complex with a DNMT inhibitor as defined in claim 1 or 2, thereby to provide the metal complex as defined in any one of claims 1 to 9.

14. An intermediate metal complex comprising:(a) a pharmaceutically acceptable central metal as defined in claim 1 or 3; and(c) 2,5-dihydroxyterephthalic acid (DTA) and / or syringic acid (SA), or(a) a pharmaceutically acceptable central metal as defined in claim 1 or 3; and(b) a DNA methyltransferase (DNMT) inhibitor optionally wherein said metal complex further comprises one or more pharmaceutically acceptable components, and preferably said one or more pharmaceutically acceptable components interact with the pharmaceutically acceptable central metal, and more preferably said one or more pharmaceutically acceptable components are coordinated to the pharmaceutically acceptable central metal.

15. Use of an intermediate metal complex as defined in claim 14, (a) for the preparation of a metal complex as defined in any one of claims 1 to 9, or (b) as an active pharmaceutical.

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