Patent Publication Number: US-2022226372-A1

Title: Use of metal ions to potentiate the therapeutic effects of arsenic

Description:
FIELD 
     The present invention pertains to the field of medicine and is based on the unexpected finding that therapeutic effects of arsenic can be potentiated by administration of divalent metal ions, and most specifically by Cu 2+  ions. 
     BACKGROUND 
     Therapeutic Use of Arsenic and Possible Mechanisms of Action 
     Arsenic compounds have widely been used as traditional medicines in many parts of the world for the treatment of various diseases such as psoriasis, syphilis, or rheumatic arthritis for over two thousand years. Many different arsenic preparations have been developed and used during the long history of these agents. For example, the Fowler&#39;s solution, which contains 1% potassium arsenite (KAsO 2 ), was prescribed for years as a remedy for leukemias and even as a tonic. 
     Some arsenical compounds are notably toxic and carcinogenic, with side effects such as cirrhosis of the liver, idiopathic portal hypertension, urinary bladder cancer, and skin cancers. Recently however, several arsenic compounds have been rediscovered and formulated to treat different diseases, such as cancer. 
     In particular, Arsenic Trioxide (As 2 O 3 , also noted “ATO” in the present text) occurs to be one of the most effective novel anticancer (“antineoplastic” or “cytotoxic”) agents. ATO has been approved by the US FDA for the treatment of acute promyelocytic leukemia (APL) resistant to “first line” agents, namely all-trans retinoic acid (ATRA). It has been shown that arsenic trioxide induces cancer cells to undergo apoptosis. 
     Arsenic Trioxide is also known or currently investigated as an agent against other diseases, such as auto-immune diseases. 
     Bobé et al. (Blood, 108, 13, p3967-3975, 2006) investigated the effects of arsenic trioxide in a mouse model of systemic lupus erythematosus. As 2 O 3  significantly prolonged survival of MRL/lpr mice by preventing young mice from developing the syndrome and quasi-totally reversing established disease in older animals. These authors suggested that this compound might be useful in the treatment of autoimmune diseases such as systemic lupus erythematosus. 
     In U.S. Pat. No. 8,394,422, Chelbi-Alix and Bobé suggested that arsenic trioxide could be used for treating autoimmune and/or inflammatory diseases. 
     Kavian et al. (J Immunol. 2012; 188(10):5142-9) reported the successful use of ATO in murine sclerodermatous GvHD. 
     More recently, Maier et al. (J. Immunol. 2014 Jan. 15; 192(2):763-70) demonstrated that arsenical compounds, including the FDA-approved anti-cancer therapeutic arsenic trioxide, are potent inhibitors of caspase-1 and the innate immune response (namely Interleukin 1-(3) and thus may have potential for the treatment of inflammatory components of autoimmune disorders. Furthermore, Li et al. showed that arsenic trioxide improves Treg and T17 balance in rheumatoid arthritis patients, thus being a potential useful immune modulator (Int. Immunopharmacology, 2019 , Arsenic trioxide improves Treg and Th 17  balance by modulating STAT 3  in treatment - naïve rheumatoid arthritis patients ). 
     It has been previously reported that As 2 O 3 -induced APL cell differentiation occurs as a result of direct binding of As 2 O 3  to cysteine residues of zinc fingers in the RING finger-B Box-Coiled Coil (RBCC) domain of PML-RARα fusion protein, which results in enhanced SUMOylation/Ubiquitination and then degradation of PML-RARα fusion protein, promoting cell differentiation leading to clinical remission (Zhang et al., Science. 2010; 328(5975):240-3; Chen et al., Blood. 2011 Jun. 16; 117(24):6425-37). However, although explanatory for the beneficial action of Arsenic in this rare cancer, this was not clearly a general phenomenon that could explain the action of As in other cancerous conditions in which it was (and still is) tested for efficacy (more than 100 clinical trials are or have been conducted with arsenic compounds by 2019, as reported in clinicaltrials.gov), nor in the autoimmune diseases or graft versus host disease. 
     To explain the recent observations of As beneficial action on the immune system, a new mechanism of action was proposed. Indeed, it became clear that one of the major consequences of the exposure of a number of cell types to As both in vitro (cell lines or primary cultures, normal or diseased) and in vivo (animal models for autoimmune diseases) was the induction of specific cell death, generally through the stimulation of various, although generally hypothetical, proapoptotic programs, expectedly leading to changes in cell subpopulations with often decreased cytokines levels and modified cell-cell communications. 
     One of the main assumptions has been that some oxidative stress pathways were activated, with ROS production (sometimes interestingly observed to be not inhibited by common antioxidants (such as N-acetylcysteine-NAC)), leading to gluthathione consumption and other cell stress inducing processes leading to cell death especially in pathologically immune activated cells (see for example Bobé et al 2006, supra and Kavian et al., supra, suggesting plasmacytoid dendritic cell death). 
     To understand arsenic&#39;s antitumor mechanism further, Zhang et al. (PNAS 2015; Vol. 112, No. 49) used a human proteome microarray to identify arsenic-binding proteins. They identified 360 arsenic-binding proteins and found proteins of glycolysis to be highly enriched. They suggest that glycolysis in general and the rate-limiting enzyme hexokinase-2 of the glycolytic pathway in particular, play a key role in mediating the anticancer activity of arsenic. 
     Moreover, it has been reported that Arsenic targets Pin1, described as a critical “driver” and a unique drug target in cancer and other diseases. Kozono et al. suggest that ATO and ATRA, at clinically safe doses, cooperatively block numerous cancer-driving pathways, through direct reversible inhibition of Pin 1, so that their combination offers an attractive approach for combating breast cancer and others (Nat Commun. 2018 Aug. 9; 9(1):3069). 
     However, the detailed mechanism(s) of action of As is(are) far from being completely elucidated. 
     Common Adverse Effects of Arsenic 
     As 2 O 3  is a pharmacologically active compound, with highly toxic properties at high concentrations or long term exposures. 
     Interestingly, treatments of Acute promyelocytic Leukemia (with FDA and EMA authorizations) and SLE (Phase 2a; terminated) or GvHDc (Phase 2, ongoing) only present reversible Adverse Effects (AE) for the intravenous (IV) dosage generally adopted (0.15 mg/kg/day over a one-two (and sometimes up to five) month periods of IV treatment). 
     The AEs are potential important threats to the health status of the patients, the most unwelcomed ones being a transient increase in the cardiac QT widening, possibly together with changes in blood electrolytes levels and hepatic increased release of liver enzymes. These AEs are carefully monitored, essentially reversible—but necessitate transient suspensions of the treatment for a few days—and occur in an important proportion of the patients. Typically, even when patients are recruited under strict inclusion/exclusion rules, about one third of them develop AEs. 
     Thus, there remains a need to decrease the amount of Arsenic administered to the patients treated with arsenic trioxide or other arsenicals to diminish the negative effects of the pharmacologically active ingredient (API; arsenic trioxide or any other arsenic compound) while keeping the same level of favorable biological activity. 
     However, on the one hand, the positive effects of arsenicals are dose-dependent and the doses commonly adopted are already calculated to minor the related adverse effects. On the other hand, as explained above the mechanism of action of arsenicals has been only partially determined and, by the time being, only a few observed biochemical and physiologic effects are of high value to appreciate the expected efficiency of the treatment. The most important one in the field of cancerology and immune pathologies is its ability to activate cell stress processes leading to cytokine releases and specific cell death, as well as a positive interference with specific immune mechanisms relevant to certain diseases. 
     Thus, there is currently a need to find drugs that would increase the positive effects of arsenic used as a medicament without exhibiting the toxicity profile of arsenic. Indeed, this would allow to decrease accordingly the amount of Arsenic salt(s) delivered for a given treatment, or to increase the efficacy of the treatment without increasing the amount of said administered arsenic salt(s). 
     ROS Production and Related Regulatory Antioxidants 
     In this context, the inventors investigated the possibilities to increase the effect of a given dose of the API by using in parallel, drugs or molecules able to increase the cell stress. 
     Cell stress is mainly mediated through an increase of Radical Oxygen Species (ROS). The main cell stress oxidative pathway is well known with its cascade of steps, including:
         i. Generation of superoxide radical: O 2 +1 e − →O 2   .−     ii. Generation of hydrogen peroxide: O 2   .− +O 2   .− +2H + →H 2 O 2 +O 2      iii. Generation of hydroxyl radical: H 2 O 2 +Fe 2+ →.OH+Fe 3+ +OH −         

     The amount of hydrogen peroxide is regulated by heme peroxidases that accelerate its dismutation and by the glutathione peroxidase (GPx) that catalyzes its reduction by glutathione (GSH). 
     Other ROS exist, such as peroxyl radicals RO 2 ., hydroperoxides RO 2 H and alkoxyl radicals RO.. 
     The H 2 O 2 -degrading Fenton reaction (reaction (iii) above) is typically catalyzed by free iron bivalent ions and leads to the generation of .OH. The Fenton reaction is admittedly localized at the endoplasmic reticulum or in perinuclear locations, but not in mitochondria or other cell compartments (Liu Q, et al. Proc Natl Acad Sci USA 2004; 101:4302-7). Sources of H 2 O 2  could be mitochondria (superoxide dismutase reaction), peroxisomes (acyl-CoA oxidase reaction) and amyloid beta of senile plaques (superoxide dismutase-like reactions). H 2 O 2  that escapes the cell antioxidant machinery, such as glutathione peroxidase and catalase, might be converted nonenzymatically in a perinuclear-localized Fenton reaction and act as an RNA- or DNA-damaging agent. 
     SUMMARY 
     The inventors investigated the possibility to increase the effect of a given dose of an arsenic compound by using in parallel, drugs or molecules able to increase the cell stress through the activation of the Fenton reaction. To this aim, they tested several elements known to increase this reaction, starting with the well-known Iron salts, as well as others, such as Zn, Mn, Mg, Cu, Au, etc. . . . 
     As described in the experimental part below, they found that in a manner totally unexpected and not explainable through the mere activation of the Fenton reaction, Cu 2+  ions specifically display strong synergic features of action with arsenic, including all searched features, i.e., H 2 O 2  cell production, apoptosis induction increase and physiologic effects in a basic and highly significant test for the immune system function, the Mixed Lymphocyte Reaction (MLR), developed with mouse cells of different genetic backgrounds. 
     The present invention thus pertains to a medicament comprising an arsenic compound and a metal ion selected from the group consisting of Cu 2+ , without omitting more classical Fenton-agents such as Au 2+ , Fe 2+ , Zn 2+ , Mn 2+ , Mg 2+  and mixtures thereof. 
     The invention also relates to the use of a combination of a Cu 2+  salt and an arsenic compound, in the treatment of various diseases including neoplastic diseases, autoimmune diseases, inflammatory diseases and neuro-degenerative diseases, wherein the arsenic compound and the Cu 2+  salt are administered to a patient simultaneously or sequentially. In such a combined treatment, the Cu 2+  ions increase the therapeutic effects of arsenic. 
    
    
     
       FIGURE LEGENDS 
         FIG. 1 : Effects of As 2 O 3  at increasing concentrations on the production of H 2 O 2 , GSH and cell viability in HL60 cells. 
         FIG. 2 : Effects of FeSO 4  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 3 : Effects of HAuCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 4 : Effects of ZnSO 4  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 5 : Effects of ZnCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 6 : Effects of MnSO 4  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 7 : Effects of MnCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 8 : Effects of CuSO 4  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 9 : Effects of CuCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 10 : Effects of As 2 O 3  (1 μM) combined to CuCl 2  (1 or 4 μM) on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 11 : Effects of As 2 O 3  (1 μM) combined to increasing concentrations of CuCl 2  (0.5 to 4 μM) on the production of GSH and cell viability in HL60 cells. 
         FIG. 12 : Effects of As 2 O 3  on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). Ordinate: DO UptiBlue, which measures the cellular metabolic activity (and is considered as a direct growth indicator). 
         FIG. 13 : Effects of FeSO 4  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 14 : Effects of HAuCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 15 : Effects of ZnSO 4  and ZnCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 16 : Effects of MnSO 4  and MnCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 17 : Effects of CuSO 4  and CuCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 18 : Effects of CuCl 2  at increasing concentrations, alone or combined to As 2 O 3  at 1 μM, on the production of H 2 O 2  and cell viability in A20 cells. 
         FIG. 19 : Effects of As 2 O 3  (1 μM) combined to increasing concentrations of CuCl 2  (0.5 to 4 μM) on the production of GSH and cell viability in A20 cells. 
         FIG. 20 : Effects of AsI 3  at increasing concentrations on the production of H 2 O 2 , GSH and cell viability in HL60 cells. 
         FIG. 21 : Effects of CuCl 2  at increasing concentrations, alone or combined to AsI 3  at 1 μM, on the production of H 2 O 2  and cell viability in HL60 cells. 
         FIG. 22 : Effects of As 2 O 3  and AsI 3  on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 23 : Effects of CuCl 2  at increasing concentrations, alone or combined to AsI 3  at 1 μM, on the proliferation of C57BL6 mice splenic cells in a mixed lymphocyte reaction (MLR). 
         FIG. 24 : Effect of treatments on the onset of skin abnormalities (alopecia) in chronic GvHD. Pictures represent the development of alopecia in the different experimental groups. A: Syngeneic (8 mice). B: Allogeneic (9 mice—7 with alopecia). C: Allogeneic+As 2 O 3  2.5 μg/g (9 mice—3 with alopecia). D: Allogeneic+As 2 O 3  2.5 μg/g+CuCl 2  2.5 μg/g (3 mice—none with alopecia). E: Allogeneic+CuCl 2  2.5 μg/g (2 mice—1 with alopecia). F: Allogeneic+As 2 O 3  2.5 μg/g+CuCl 2  10 μg/g (2 mice—none with alopecia). G: Allogeneic+CuCl 2  10 μg/g (5 mice—none with alopecia). H: Allogeneic+As 2 O 3  5 μg/g (5 mice—1 with alopecia). 
         FIG. 25 : Effects of the treatments on mice weight during the evolution of GVHD. A. syngeneic and allogeneic groups treated or not with As 2 O 3  (2.5 μg/g or 5 μg/g, as indicated). B. syngeneic group and allogenic groups treated or not with (As 2 O 3  2.5 μg/g and CuCl 2  2.5 μg/g). C. syngeneic group and allogenic groups treated or not with (As 2 O 3  2.5 μg/g and CuCl 2  10 μg/g). 
         FIG. 26 : Effects of the treatments on vasculitis (clinical scoring: ear thicknesses) during the evolution of GVHD. A. Thickness of the mice ears in the syngeneic and allogenic groups treated or not with As 2 O 3  at 2.5 μg/g or 5 μg/g. B. Thickness of the mice ears in the syngeneic and allogenic groups treated or not with As 2 O 3  at 2.5 μg/g and CuCl 2  at 2.5 μg/g. C. Thickness of the mice ears in the syngeneic and allogenic groups treated or not with As 2 O 3  at 2.5 μg/g and CuCl 2  at 10 μg/g. 
         FIG. 27 : Effects of the treatments on the liver: transaminases levels in each mouse blood. A. ALAT in the sera of syngeneic and allogeneic mice according to the treatments. B. ASAT in the sera of syngeneic and allogeneic mice according to the treatments. 
         FIG. 28 : Effects of the treatments on mice weights during the evolution of GVHD. Mice treated with copper at 0/0.2 μg/g and 0.5 μg/g. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the terms “treat”, “treatment” and “treating” refer to any reduction of one or more symptom(s) associated with a disease, such as, for example, a reduction of the occurrence and/or severity of symptoms in an autoimmune disease, and/or an increase in survival that results from the administration of a composition according to the invention to cancer patients. These terms are used herein to generally mean obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease and/or may be therapeutic in terms of a partial or complete cure for a disease and/or adverse effect attributable to the disease. “Treatment” as used herein covers any treatment of a disease in a mammal, and includes: preventing the disease from occurring in a subject which may be predisposed to the disease but has not yet been diagnosed as having it; inhibiting the disease, i.e., arresting its development; or relieving the disease, i.e., causing regression of the disease. The therapeutic agent may be administered before, during or after the onset of disease or injury. The treatment of ongoing disease, where the treatment stabilizes or reduces the undesirable clinical symptoms of the patient, is of particular interest. 
     As used herein, the phrase “ameliorating at least one symptom of” refers to decreasing one or more symptoms of the disease or condition for which the subject is being treated. In particular embodiments, the disease or condition being treated is a hematological malignancy, wherein the one or more symptoms ameliorated include, but are not limited to, weakness, fatigue, shortness of breath, easy bruising and bleeding, frequent infections, enlarged lymph nodes, distended or painful abdomen (due to enlarged abdominal organs), bone or joint pain, fractures, unplanned weight loss, poor appetite, night sweats, persistent mild fever, and decreased urination (due to impaired kidney function). 
     As used herein, “prevent,” and similar words such as “prevented,” “preventing” etc., indicate an approach for preventing, inhibiting, or reducing the likelihood of the occurrence or recurrence of, a disease or condition. It also refers to delaying the onset or recurrence of a disease or condition or delaying the occurrence or recurrence of the symptoms of a disease or condition. As used herein, “prevention” and similar words also include reducing the intensity, effect, symptoms and/or burden of a disease or condition prior to onset or recurrence of the disease or condition. 
     As used herein, the term “amount” refers to “an amount effective” or “an effective amount” of arsenic+metal ion sufficient to achieve a beneficial or desired prophylactic or therapeutic result, including clinical results. In one embodiment an effective amount refers to the amount of an arsenic-containing compound and of a metal ion sufficient to prevent, ameliorate one symptom of, or treat a disease, e.g., a hematological malignancy or an autoimmune disease contemplated herein. 
     A “prophylactically effective amount” refers to an amount of an arsenic-containing compound+a metal ion effective to achieve the desired prophylactic result. Typically but not necessarily, since a prophylactic dose is used in subjects prior to or at an earlier stage of disease, the prophylactically effective amount is less than the therapeutically effective amount. 
     A “therapeutically effective amount” of an arsenic-containing compound+a metal ion may vary according to factors such as the disease state, age, sex, and weight of the individual, and the natures of the agent (arsenic compound) and co-agent (metal ion) to elicit a desired response in the individual. A therapeutically effective amount is also one in which any toxic or detrimental effects of the agent are outweighed by the therapeutically beneficial effects. The term “therapeutically effective amount” includes an amount that is effective to “treat” a subject (e.g., a patient). 
     As used herein, the term “comprise” or “include” is intended to mean that the compositions and methods include the recited elements, but not excluding others. “Consist essentially of” when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination. For example, a composition consisting essentially of the elements as defined herein would not exclude other elements that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consist of” shall mean excluding more than trace amounts of other ingredients and substantial method steps recited. Embodiments defined by each of these transition terms are within the scope of this invention. 
     The term “about” when used before a numerical value indicates that the value may vary within reasonable range, such as ±10%, ±5%, and ±1%. The expression “about x” includes the value “x.” 
     The singular forms “a” and “the” include plural references unless the context clearly dictates otherwise. Thus, e.g., reference to “a metal ion” includes a plurality of metal ions. 
     Other definitions will be specified below, when necessary. 
     According to a first aspect, the present invention pertains to a medicament comprising an arsenic compound and a metal ion selected amongst Cu 2+ , Au 2+ , Fe 2+ , Zn 2+ , Mn 2+ , Mg 2+  and mixtures thereof. 
     Examples of arsenic compounds (generally salts) that can be used as active ingredients in a composition according to the invention include As 2 O 3 , AsI 3 , As 2 O 5 , As 4 O 6 , As 2 S 2 , As 2 S 3 , As 2 S 5 , As 4 S 4  and mixtures thereof. 
     Medicaments according to the present invention preferably comprise arsenic trioxide or arsenic triiodide, together with a metal ion as listed above, such as Cu 2+ , alone or combined to any other metal ion selected amongst Au 2+ , Fe 2+ , Zn 2+  Mn 2+  and Mg 2+ . 
     According to a particular embodiment illustrated in the examples below, the Cu 2+  ions are in the form of a salt such as copper sulfate (CuSO 4 ) or copper(II) chloride (CuCl 2 ). 
     The actual dosing for ATO when used in the treatment of hematologic cancers is 0.15 mg/kg/day. The results disclosed in the experimental part below demonstrate that when ATO is used in combination with Cu 2+ , its effects are potentiated. Hence, the same therapeutic efficacy should be obtained with a lower dose of ATO in the presence of Cu 2+  as that of the currently used ATO formulation. Depending on the situation, the physician can also choose to combine with Cu 2+  ions the same concentration of ATO as that currently approved in combination, to increase the therapeutic effects of ATO. 
     According to a particular embodiment of the invention, the composition according to the present invention is formulated so that one daily dose comprises between 0.01 to 0.15 mg/kg/day of arsenic trioxide (corresponding to 0.1 to 1.6 μmol/kg of arsenic atoms). 
     According to another particular embodiment of the invention, the composition according to the present invention is formulated so that one daily dose comprises between 0.01 to 0.05 mg/kg/day of arsenic trioxide. 
     According to another particular embodiment of the invention, the composition according to the present invention is formulated so that one daily dose comprises between 0.05 to 0.10 mg/kg/day of arsenic trioxide. 
     According to another particular embodiment of the invention, the composition according to the present invention is formulated so that one daily dose comprises between 0.10 to 0.15 mg/kg/day of arsenic trioxide. 
     When an arsenic compound different from arsenic trioxide is used in the frame of the present invention, its dosage can be chosen so that the amount of arsenic atoms administered to the patient is the same as that in the dosages indicated above for arsenic trioxide. 
     According to another particular embodiment of the invention, the composition according to the present invention is formulated so that one daily dose comprises between 0.05 μmol/kg and 10 μmol/kg of Cu 2+ , preferably between 0.06 μmol/kg and 2 μmol/kg of Cu 2+ , for example between 0.3 μmol/kg and 1.1 μmol/kg of Cu 2+ . According to particular embodiments, the composition according to the present invention is formulated so that one daily dose comprises about 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.15, 0.2, 0.25, 0.30, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.2, 2.2, 2.4, 2.6, 2.8, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9 or 10 μmol/kg of Cu 2+ . 
     Of course, the skilled person can choose any other scheme of copper administration, such as once every other day, once every three days or even once a week, to reach a dose equivalent to the daily dose described above. 
     Any disease which has already been successfully treated by ATO or any other arsenic compound can beneficiate from a treatment with a composition as above-described, since the combination of arsenic and the metal ions such as Cu 2+  increase the beneficial effects of arsenic. In addition, one might anticipate that diseases that share pathophysiologic mechanisms with diseases and disorders already successfully treated by arsenic but that could until now not beneficiate from the effects of arsenic because they would need higher doses of active principle, difficult to reconcile with safety, could now be treated with a synergistic combination of arsenic and a metal ion such as Cu 2+ . 
     The present invention thus pertains to the use of a composition as above-described in treating a disease selected amongst:
         neoplastic diseases,   autoimmune diseases and   inflammatory diseases.       

     The present invention also pertains to the use of a combination of a Cu 2+  salt (e.g., Cu 2 SO 4  or CuCl 2 ) and an arsenic compound (as above-described), in the treatment of a disease selected from the group consisting of a neoplastic disease, an autoimmune disease and an inflammatory disease, wherein said arsenic compound and said Cu 2+  salt are administered to a patient simultaneously or sequentially. 
     The present invention thus also pertains to the use of a composition comprising an arsenic compound, for treating a disease selected from the group consisting of a neoplastic disease, an autoimmune disease and an inflammatory disease, wherein said arsenic compound is administered to a patient in combination with a Cu 2+  salt or any other metallic ions with similar properties. According to a particular embodiment, the composition comprising an arsenic compound is administered before the composition comprising a Cu 2+  salt. According to another particular embodiment, the composition comprising an arsenic compound is administered after the composition comprising a Cu 2+  salt. In both cases, the arsenic compound and the Cu 2+  salt are administered in a time interval preferably not exceeding 12 hours. According to another particular embodiment, the composition comprising an arsenic compound and the composition comprising a Cu 2+  salt are administered simultaneously. Whatever the administration sequence, the arsenic compound and the Cu 2+  salt are administered either via the same route or via different routes. 
     According to another of its aspects, the present invention pertains to the use of a salt of a metal ion, e.g. a Cu 2+  salt, for potentiating/increasing the therapeutic effects of an arsenic compound as described above. Cu 2+  ions or the like can for example be used for potentiating the therapeutic effects of ATO or any other arsenic compound used in the treatment of a disease such as a neoplastic disease, an autoimmune disease, or more generally an inflammatory disease. By “potentiating” is herein meant that using a same amount of an arsenic compound (e.g., ATO), the therapeutic effects of arsenic are significantly increased when the patient also receives Cu 2+  ions, although the administration of Cu 2+  ions alone is without any measurable effect. This potentiation or synergy has been demonstrated at least in vitro, as illustrated in examples 1 to 9 below (which show a significant increase of H 2 O 2  cell production and apoptosis induction, as well as physiologic effects in a Mixed Lymphocyte Reaction (MLR), which is a highly significant assay for the immune system function). The results shown in example 10 illustrate this synergy in vivo, in an animal model. 
     According to another aspect, the present invention also pertains to a method for treating a disease selected from the group consisting of a neoplastic disease, an autoimmune disease, or more generally an inflammatory disease in a patient in need thereof, comprising the step of administering an effective dose of an arsenic compound (as above defined) and of a metal ion selected amongst Cu 2+ , Au 2+ , Fe 2+ , Zn 2+ , Mn 2+ , Mg 2+  and mixtures thereof to said patient. According to a particular embodiment, a Cu 2+  salt is administered to the patient. 
     Depending on the context (nature of the arsenic compound, disease concerned, stage of this disease and general parameters of the patient), the clinician will adapt the dosing and scheme of administration of arsenic compound and Cu 2+  salt or the like. 
     According to a particular embodiment, the arsenic compound is arsenic trioxide. In such a case, a therapeutically effective amount is at most 0.30 mg/kg/day of ATO, for example 0.30, 0.25, 0.20 or 0.15 mg/kg/day of ATO and a prophylactically effective amount is at most 0.15 mg/kg/day of ATO, for example 0.15, 0.10 or 0.05 mg/kg/day of ATO or even less, down to 0.01 mg/kg/day. 
     According to a particular embodiment, the patient is administered a daily dose that comprises between 0.01 to 0.15 mg/kg/day of arsenic trioxide, during 1 to 80 days. 
     According to another particular embodiment, the patient is administered a daily dose that comprises between 0.01 to 0.05 mg/kg/day of arsenic trioxide, during 1 to 80 days, with the possibility to reiterate the treatment if needed for reaching a satisfactory level of clinical efficacy. 
     According to another particular embodiment, the patient is administered a daily dose that comprises between 0.05 to 0.10 mg/kg/day of arsenic trioxide, during 1 to 80 days. 
     According to another particular embodiment, the patient is administered a daily dose that comprises between 0.10 to 0.15 mg/kg/day of arsenic trioxide, during 1 to 80 days. 
     According to another particular embodiment of the invention, the patient is administered a daily dose that comprises between 0.05 μmol/kg and 10 μmol/kg of Cu 2+ , preferably between 0.06 μmol/kg and 2 μmol/kg of Cu 2+ , for example between 0.3 μmol/kg and 1.1 μmol/kg of Cu 2+ , as long as he/she receives the arsenic compound. According to particular embodiments, the patient receives about 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.15, 0.2, 0.25, 0.30, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.2, 2.2, 2.4, 2.6, 2.8, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9 or 10 μmol/kg of Cu 2+ , each day, as long as he/she receives the arsenic compound. 
     The Cu 2+  ions can be, for example, in the form of copper sulfate or copper(II) chloride. 
     As already mentioned, the arsenic compound and the Cu 2+  salt are administered to the patient simultaneously or sequentially, through the same or a different route of administration. The Cu 2+  salt can be administered to the patient every day, every other day, two or three times a week, or even weekly. 
     According to a particular embodiment, the arsenic compound is administered intravenously. 
     According to another particular embodiment, the arsenic compound is administered orally. 
     According to another particular embodiment, the arsenic compound is administered topically. 
     According to another particular embodiment, the arsenic compound is administered as an aerosol. 
     According to another particular embodiment, the arsenic compound and the Cu 2+  salt are in the same pharmaceutical composition. This invention thus relates to a method of administering to a subject, a pharmaceutical composition comprising an arsenic compound and a Cu 2+  salt, comprising the steps of providing said pharmaceutical composition, and administering said pharmaceutical composition to said subject. This invention further relates to a method of treating an autoimmune disease, and more generally an inflammatory disease, or a neoplastic disease such as a cancer or a tumor in a patient in need thereof, comprising the step of administering to the patient a therapeutically effective amount of the pharmaceutical composition comprising an arsenic compound and a Cu 2+  salt. 
     Neoplastic Diseases 
     The term “neoplastic disease” is used herein to refer to a pathologic proliferation of cells in tissue of a subject, as compared with normal proliferation in the same type of tissue. Neoplasms include benign tumors and malignant tumors (e.g., leukemias or colon tumors or prostate cancer) that are either invasive or noninvasive. Malignant neoplasms are distinguished from benign neoplasms in that the former show a greater degree of anaplasia, or loss of differentiation and orientation of cells, and have the properties of invasion and metastasis 
     Cancers that can be treated according to the present invention include solid and non solid cancers. According to a particular embodiment, the cancer is a hematological malignancy. Example of hematological malignancies that can be treated according to the invention include acute myeloid leukemia; acute nonlymphocytic leukemia; myeloblastic leukemia, promyelocytic leukemia; chronic myelomonocytic leukemia; monocytic leukemia; erythroleukemia; acute neutrophilic leukemia; myelodysplastic syndrome; acute promyelocytic leukemia; chronic lymphocytic leukemia; chronic myeloid leukemia; hairy cell leukemia; myeloproliferative neoplasms; Hodgkin&#39;s lymphoma; non-Hodgkin&#39;s lymphoma; myeloma; giant cell myeloma; indolent myeloma; localized myeloma; multiple myeloma; plasma cell myeloma; sclerosing myeloma; solitary myeloma; smoldering multiple myeloma; nonsecretary myeloma; osteosclerotic myeloma; plasma cell leukemia; solitary plasmacytoma; and extramedullary plasmacytoma. 
     In another embodiment, said hematological malignancy is acute promyelocytic leukemia (APL). In one embodiment, said APL is newly diagnosed APL. In another embodiment, said APL is relapsed or refractory APL. 
     Other cancers that can be treated according to the present invention include, without limitation, carcinomas (e.g., squamous-cell carcinomas, adenocarcinomas, hepatocellular carcinomas, and renal cell carcinomas), particularly those of the bladder, bowel, breast, cervix, colon, esophagus, head, kidney, liver, lung, neck, ovary, pancreas, prostate, and stomach; benign and malignant melanomas; myeloproliferative diseases; sarcomas, particularly Ewing&#39;s sarcoma, hemangiosarcoma, Kaposi&#39;s sarcoma, liposarcoma, myosarcomas, peripheral neuroepithelioma, and synovial sarcoma; tumors of the central nervous system (e.g., gliomas, astrocytomas, oligodendrogliomas, ependymomas, gliobastomas, neuroblastomas, ganglioneuromas, gangliogliomas, medulloblastomas, pineal cell tumors, meningiomas, meningeal sarcomas, neurofibromas, and Schwannomas); germ-line tumors (e.g., bowel cancer, breast cancer, prostate cancer, cervical cancer, uterine cancer, lung cancer, ovarian cancer, testicular cancer, thyroid cancer, astrocytoma, esophageal cancer, pancreatic cancer, stomach cancer, liver cancer, colon cancer, and melanoma); mixed types of neoplasias, particularly carcinosarcoma and Hodgkin&#39;s disease; and tumors of mixed origin, such as Wilms&#39; tumor and teratocarcinomas. 
     Autoimmune and Inflammatory Diseases 
     Autoimmune diseases are diseases of the immune system characterized by the production of antibodies (called autoantibodies) which react with antigens (called autoantigens) originating from the tissues of the patient or diseases which are characterized by an activation of immune cells (for example cytotoxic cells) with or without the production of antibodies. 
     Inflammatory diseases include a vast array of disorders and conditions that are characterized by inflammatory processes, either secondary or primary or even unique (prevalent over other immune mechanisms). 
     Autoimmune diseases and inflammatory diseases that can be treated with a combination of an arsenic compound and a metal ion such as Cu 2+  according to the invention include, without limitation, systemic lupus erythematosus (SLE); acute disseminated lupus erythematosus; Bechet&#39;s disease; juvenile arthritis; Fiessinger-Leroy-Reiter syndrome; gout; osteoarthrosis; polymyositis; myocarditis; autoimmune rheumatoid arthritis (RA); systemic vasculitis; insulin-dependent diabetes mellitus (IDDM; type I diabetes, inflammatory bowel disease (IBD); celiac disease, autoimmune thyroid disease; Sjogren&#39;s syndrome, autoimmune gastritis, ulcerative colitis; Crohn&#39;s disease; autoimmune hepatitis, primary biliary cirrhosis; primary sclerosing cholangitis; cutaneous autoimmune diseases; autoimmune dilated cardiomyopathy, multiple sclerosis (MS) and other demyelinating diseases; myasthenia gravis (MG); vasculitis (e.g., Takayasu&#39;s arteritis and Wegener&#39;s granulomatosis); aplastic anemia, any disease associated with a nontumoral lymphoproliferation; B-lymphocyte lymphoma; Simmonds&#39; syndrome; subacute thyroiditis and Hashimoto&#39;s disease; Addison&#39;s disease; autoimmune diseases of the muscle, autoimmune neuromuscular disorders, such as ankylosing spondylitis, multiple sclerosis, its varied forms including pediatric syndromes and acute disseminated encephalitis; immune mediated neuropathies; autoimmune diseases of testis, autoimmune ovarian disease, autoimmune uveitis, Graves&#39; disease, psoriasis, ankylosing spondylitis, Addison disease, Hashimoto thyroiditis, idiopathic thrombocytopenic purpura, autoimmune lung disease such as Wegener&#39;s disease and Churg-Strauss syndrome; immunologic lung diseases such as asthma, infiltrative lung disease, hypersensitivity lung disease and sarcoidosis; dermatomyositis including scleroderma and polymyositis; and vitiligo. 
     The products of the present invention can also be used for treating graft-versus-host disease (GvHD) either as a preventive as well as a curative treatment. 
     Multiple Sclerosis 
     The beneficial effects of arsenic compounds, especially arsenic trioxide, has already been reported for multiple sclerosis (US 2018/325944). Thus, multiple sclerosis and related syndromes can be treated according to the invention with a combination of an arsenic compound and a metal ion such as Cu 2+ . 
     Particular diseases that can be treated according to the present invention are human diseases or their animal counterparts which are already successfully treated with ATO, such as acute promyelocytic leukemia, systemic lupus erythematosus (SLE), chronic graft versus host disease (GvHD), multiple sclerosis (MS), Sjögren syndrome, rheumatoid arthritis, Crohn&#39;s disease, myelocytic leukemia, chronic myeloid leukemia, chronic lymphocytic leukemia, malignant glioma, myelodysplastic syndrome, multiple myeloma and liver cancer. As explained above, the present invention provides a means to potentiate the effects of arsenic when used in the treatment of these diseases, thus enabling to use lower daily doses of ATO or to obtain better therapeutic results with the same dosage as currently used. 
     Other characteristics of the invention will also become apparent in the course of the description which follows of the biological assays which have been performed in the framework of the invention and which provide it with the required experimental support, without limiting its scope. 
     EXAMPLES 
     Absent any indication to the contrary, the experimental results shown in Examples 1 to 9 have been obtained using the following materials and methods. 
     a—Cells, Animals and Chemicals 
     HL60 Cell culture: the HL-60 cell line is a Human caucasian promyelocytic leukaemia cell line (ATCC n° CCL-240). This line was maintained throughout the experiment, retaining 2×10 5  cells per ml by Flask (Falcon 250 mL 75 cm 2 , Reference: 353135) in a RPMI 1640+GlutaMax culture medium Sigma-Aldrich (Saint-Quentin Fallavier, France) containing 10% Foetal Bovine Serum (Gibco, USA), 1% penicillin-streptomycin (Gibco, USA), 1% ciprofloxacine and 1% fungizone (Gibco, USA). 
     A20 Cell culture: the A20 cell line is a mouse cell line (ATCC n° TIB-208). This line was maintained throughout the experiment, retaining 2×10 5  cells per ml by Flask (Falcon 250 mL 75 cm 2 , Reference: 353135) in a RPMI 1640+GlutaMax culture medium Sigma-Aldrich (Saint-Quentin Fallavier, France) containing 10% Foetal Bovine Serum (Gibco, USA), 1% penicillin-streptomycin (Gibco, USA), 1 ciprofloxacine, 1% fungizone (Gibco, USA) and 1% 2-mercaptoethanol (Gibco, USA). 
     Animals: eight week-old female BALB/c and female C57Bl6 mice were purchased from Janvier Labs (Le Genest-Saint-Isle, France) and maintained with food and water ad libitum. They were given humane care, according to national guidelines. The spleen cells of each type mouse were used on the culture mixed of lymphocytes (model MLR). 
     Chemicals:
         The first five divalent cations tested were purchased from Sigma-Aldrich (Saint-Quentin Fallavier, France): CuSO 4 , FeSO 4 , MnSO 4 , ZnSO 4  as well as HAuCl 2  (Laboratory grades).   The three others divalent cations tested have been purchased from ChemCon (Freiburg, Germany): CuCl 2 , MnCl 2  and ZnCl 2  (GMP grades).   Arsenic trioxide (Arscimed, quality clinical batch, stock solution at 1 mg/ml) come from MEDSENIC (Strasbourg, France).       

     b—Statistical Analysis 
     All of the quantitative data were analyzed with GraphPad Prism5, using one-way ANOVA and a post-hoc (Tukey). A p value &lt;0.05 was considered statistically significant. 
     c—Effects of As 203  with or without Divalent Cations on H 2 O 2  Production and GSH Production in HL-60 Cultured Cells 
     Conditions of Culture and Treatment 
     Cells (5×10 5  per well) were seeded in 96-wells round bottom plates (Falcon, Corning, reference: 353077) and incubated for 48 hours with different experimental conditions in an incubator at 37° C. 5% CO2. Two plates were prepared in parallel to measure the H 2 O 2  production and HL-60 cell viability, respectively. 
     Measurement of H 2 O 2  Production 
     After 48 hours, the supernatant was removed and 50 μL per well of 50 μg/mL 2′, 7′-dichlorodihydrofluorescein diacetate (Sigma-Aldrich Saint-Quentin Fallavier, France) in PBS was added on cells in same conditions of treatment (medium, or As 2 O 3  with or without cation). 
     The H 2 O 2  production was assessed by spectrofluorimetry using a fusion spectrofluorimeter (Packard). Fluorescence intensity was recorded immediately (T0 hour) and after 6 hours of incubation (T6 hours). Fluorescence excitation/emission maxima were for 2′, 7′-dichlorodihydrofluorescein diacetate 485/530 nm. 
     Measurement of GSH Production 
     After 48 hours, the supernatant was removed and 50 μL per well of 50 μg/mL monochlorobimane (Sigma-Aldrich Saint-Quentin Fallavier, France) in PBS was added on cells in same conditions of treatment (medium, or As 2 O 3  with or without cation). 
     The GSH production was assessed by spectrofluorimetry using a fusion spectrofluorimeter (Packard). Fluorescence intensity was recorded immediately (T0 hour) and after 6 hours of incubation (T6 hours). Fluorescence excitation/emission maxima were for monochlorobimane, 380/461 nm. 
     HL-60 Cell Viability 
     The medium was removed and cells were stained with 0.5% crystal violet and 30% ethanol in PBS for 30 minutes at room temperature. After two washes in PBS, the stained cells were suspended in methanol, and absorbance was measured at 550 nm by a fusion spectrofluorimeter (as in Ngô et al., Reactive Oxygen Species Controls Endometriosis Progression; The American journal of pathology; 2009, 175(1):225-34). 
     Calculation of H 2 O 2  or GSH Produced During 6 Hours: 
     The H 2 O 2  or GSH production by the cells were calculated in each condition of treatment as follows: 
       Fluorescence intensity [arbitrary units] at T6h−fluorescence intensity [arbitrary units] at T0/DO produced by viable cells with membrane integrity
 
     Conditions of Treatments and Related Experimentations (2 Tests)
         H 2 O 2  or GSH production and cell survival: range of As 2 O 3 : 0.5; 1; 5 and 10 μM   H 2 O 2  production: comparison of 5 bivalent cations at 4 concentrations with or without AS2O3 (1 μM):
           Sigma:
               CuSO 4 : 0.5; 1; 2 and 4 μM   FeSO 4 : 0.5; 1; 2 and 4 μM   ZnSO 4 : 6; 12.5; 25 and 50 μM   HAuCl 2 : 0.125; 0.25; 0.5; 1 μM   MnSO 4 : 0.125; 0.25; 0.5; 1 μM   
               Chemcon:
               CuCl 2 : 0.5; 1; 2 and 4 μM   ZnCl 2 : 6; 12.5; 25 and 50 μM   MnCl 2 : 125; 0.25; 0.5; 1 μM   
               
               

     Additional Results
         H 2 O 2  or GSH production and cell survival: range of As 203  concentrations at 0.5; 1; 5 and 10 μM with CuCl 2  at 1 and 4 μM (1 test)   GSH production and cell survival: As 203  (1 μM) with CuCl 2  at 0.5, 1, 2 and 4 μM (2 tests)       

     d—Effects of As 203  with or without Divalent Cations on H 2 O 2  Production and GSH Production in A20 Cultured Cells 
     Conditions of Culture and Treatment 
     Cells (1×10 5  per well) were seeded in 96-wells round bottom plates (Falcon, Corning, reference: 353077) and incubated for 48 hours with different experimental conditions in an incubator at 37° C. 5% CO2. Two plates were prepared in parallel to measure respectively the H 2 O 2  production and A20 cell viability. 
     H 2 O 2  production, GSH production and cell viability were measured using the same protocols as above-described for H60 cells. 
     Conditions of Treatments and Related Experimentations: 1 Test H 2 O 2 — 1 Test GSH
         H 2 O 2  or GSH production and cell survival: As 2 O 3  (1 μM) with CuCl 2  at 0.5; 1; 2 and 4 μM.       

     e—As 203  with or without Divalent Cations on the Proliferation of C57Bl6 CD4 T Cells In Vitro (Cell Proliferation in Mixed Lymphocyte Cultures). 
     The model is based on the mixed culture of lymphocytes derived from the suspensions of spleen cells from a female C57Bl6 mouse and a female BALB/c mouse irradiated at 30 Gy. The spleen cells were mechanically separated and the erythrocytes were eliminated by hypotonic lysis of (ACK—NH 4 Cl 0.15M+KHCO 3  1 mM+Na 2 EDTA 0.1 mM). 
     The UptiBlue Viable Cell Counting assay was used to measure quantitatively the in vitro cell proliferation. C57Bl6 cells (responding cells) were seeded with irradiated BALB/c cells (stimulating cells) at 6×10 5  per well per line in 96-wells around bottom plates (Falcon, Corning, reference: 353077). The mixed cells culture was incubated for 48 hours at different experimental conditions in an incubator at 37° C. 5% CO 2 . 
     After 48 h, 10 μl of UptiBlue Viable Cell Counting assay (Interchim, reference: UP669413) was added directly in culture medium and the C57 cell proliferation was measured using a spectrofluorimeter (Fusion microplate reader fluorometer, Packard) after 24 hours of incubation with UptiBlue at 37° C. with 5% CO 2 . 
     Conditions of treatments: 2 tests were performed (except with ZnCl 2  and MnCl 2 )
         Sigma:
           CuSO 4 : 0.5; 1; 2 and 4 μM   FeSO 4 : 0.5; 1; 2 and 4 μM   ZnSO 4 : 6; 12.5; 25 and 50 μM   HAuCl 2 : 0.125; 0.25; 0.5; 1 μM   MnSO 4 : 0.125; 0.25; 0.5; 1 μM   
           Chemcon:
           CuCl 2 : 0.5; 1; 2 and 4 μM   ZnCl 2 : 6; 12.5; 25 and 50 μM   MnCl 2 : 125; 0.25; 0.5; 1 μM   
               

     Example 1: Effects of As 2 O 3  on H 2 O 2  and GSH Production and Cell Survival of HL60 Cells 
     The HL60 cell line is a human leukemia cell line. When a patient has leukemia, he undergoes chemotherapy to eliminate leukemia cells and then receives a bone marrow transplant from a healthy patient. In some cases, hematopoietic stem cell transplantation induces chronic Graft-versus Host Disease (GvHD). First-line therapy for chronic GVHD is based on immunosuppressive agents (corticosteroids with or without cyclosporine) achieving satisfactory response in around 30% of patients. A Phase II study is currently conducted by Medsenic to evaluate if the addition of arsenic trioxide to standard therapy is effective in controlling chronic GvHD and to reduce the duration of corticosteroid therapy. In this study, arsenic trioxide is administrated to patients at 0.15 mg/kg/day. One aspect of this study is to see if arsenic trioxide is able to act on possibly surviving leukemic cells resistant to chemotherapy, in addition to its effect on the autoimmune features of chronic GvHD, through a process involving the induction of cellular stress on the cells. 
     Cells are able to respond to cellular stress by inducing production of reactive oxygen species. In this study, investigators observed the effect of As compounds/As 2 O 3 -induced cell stress in the presence of divalent cations on the production of hydrogen peroxide (H 2 O 2 ), Glutathione production (GSH), and cell viability. 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates (Falcon, Corning, reference: 353077) and incubated for 48 hours in complete medium with or without arsenic trioxide at several concentrations: 0.1; 0.5; 1; 5 and 10 μM (As 2 O 3 ) in an incubator at 37° C. 5% CO 2 . 
     Effects of As 2 O 3 : 
       FIG. 1  shows the effect of As 2 O 3  at increasing concentrations on the production of H 2 O 2 , GSH and cell viability (4 independent tests). 
     The production of H 2 O 2  in the presence of As 2 O 3  is not significant, but it increases at 5 μM ( FIG. 1A ). 
     GSH production increases significantly in the presence of As 2 O 3  at 0.5, 1 and 5 μM, and disappears at 10 μM ( FIG. 1C ). 
     HL-60 cell viability decreases significantly in the presence of As 2 O 3  at 1, 5 and 10 μM (p&lt;0.05, p&lt;0.001 and P&lt;0.001 respectively;  FIGS. 1B and 1D ). 
     Cell death at 5 and 10 μM explains the decrease of H 2 O 2  and GSH production at these As 2 O 3  concentrations. 
     Conclusion 
     The dose of 1 μM of As 2 O 3  was selected to test the effect of combinations of As 2 O 3  and metal ions on H 2 O 2  production and cell survival of HL60 cells. 
     At this concentration, the biological effect of H 2 O 2  production is still compensated by the production of GSH and the cell viability is preserved. Thus, the As 2 O 3  effect can be modulated by a metal ion. 
     Example 2: Effects of Combinations of As 2 O 3  and Metal Ions on H 2 O 2  Production and Cell Survival of HL60 Cells 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates (Falcon, Corning, reference: 353077) and incubated for 48 hours in complete medium with or without arsenic trioxide 1 μM (As 2 O 3 ) with or without different cations or with culture medium alone in an incubator at 37° C. 5% CO 2 . The results presented come from 2 independent experiments (except MnCl 2  and ZnCl 2 ), and the cations have different quality levels: laboratory grade CuSO 4  (0.5; 1; 2 and 4 μM), FeSO 4  (0.5; 1; 2 and 4 μM), ZnSO 4  (6; 12.5; 25 and 50 μM), HAuCl 2  (0.125; 0.25; 0.5; 1 μM), MnSO 4  (0.125; 0.25; 0.5; 1 μM) and GMP grade CuCl 2  (0.5; 1; 2 and 4 μM), ZnCl 2  (6; 12.5; 25 and 50 μM), MnCl 2  (125; 0.25; 0.5; 1 μM). 
     Effects of Combinations of As 2 O 3  and Metal Ions: 
     The results of these experiments on HL60 cell for H 2 O 2  production and cell viability with FeSO 4 , HAuCl 2 , ZnSO 4 , ZnCl 2 , MnSO 4 , MnCl 2 , CuSO 4  and CuCl 2  are illustrated in  FIGS. 2 to 9 , respectively. 
     The statistically significant differences are represented on the figures as follows:
         control cells vs. cells treated by As 2 O 3      control cells vs. cells treated by cations only   cells treated by As 2 O 3  vs. cells treated by As 2 O 3 + cations.       

     FeSO 4  alone has a significant effect on H 2 O 2  production only at 4 μM (test 1), or with As 2 O 3  (1 μM) at 4 μM (test 1, p&lt;0.001) and at 2 and 4 μM (test 2, p&lt;0.01 and 0.001, respectively ( FIG. 2 , upper panels). FeSO 4  alone and with As 2 O 3  (1 μM) has no significant effect on HL60 viability ( FIG. 2 , lower panels). 
     HAuCl 2  alone has no significant effect on H 2 O 2  production; this effect is limited at 1 μM with As 2 O 3  (p&lt;0.01, test 1) and at 0.5 μM with As 2 O 3  (p&lt;0.01, test 2;  FIG. 3 , upper panels). HAuCl 2  alone and with As 2 O 3  (1 μM) has no significant effect on HL60 viability ( FIG. 3 , lower panels). 
     ZnSO 4  and ZnCl 2  alone have no reproducible effect on H 2 O 2  production ( FIGS. 4 and 5 , upper panels). With As 2 O 3  (1 μM), ZnSO 4  significantly increases H 2 O 2  production at 12.5; 25 and 50 μM (p&lt;0.001, only test 2;  FIG. 4 , right-hand upper panel). With As 2 O 3 , ZnSO 4  and ZnCl 2  have no significant and reproducible effect on cell viability ( FIGS. 4 and 5 , lower panels). 
     MnSO 4  has a significant dose-dependent effect on H 2 O 2  production at 0.25, 0.5 and 1 μM (tests 1 and 2,  FIG. 6 , upper panels) and additional effect with As 2 O 3  at 0.5 and 1 μM (p&lt;0.001; tests 1 &amp; 2;  FIG. 6 , upper panels) and even with As 2 O, at 0.25 (p&lt;0.001; test 2;  FIG. 6 , left-hand upper panel). MnSO 4 , with or without As 2 O 3 , have no real effect on cell viability ( FIG. 6 , lower panels). 
     MnCl 2 , with or without As 2 O 3  has a dose-dependent effect on H 2 O 2  production, but the increases are only significant at 1 μM (p&lt;0.001, test 1,  FIG. 7 , upper panel). MnSO 4 , with or without As 2 O 3 , has no real effect on cell viability ( FIG. 7 , lower panel). 
     CuSO 4  and CuCl 2  alone have no significant effect on H 2 O 2  production ( FIGS. 8 and 9 , upper panels). The apparent effect of CuSO 4  on H 2 O 2  production, in test 2, can be explained by an abnormally low control value. CuSO 4  and CuCl 2  both increase the effect of As 2 O 3 , at all concentrations tested (p&lt;0.001,  FIGS. 8 and 9 , upper panels). CuSO 4  and CuCl 2 , with or without As 2 O 3 , seem to have no real effect on cell viability ( FIGS. 8 and 9 , lower panels). 
     Table 1 summarizes the results obtained on H 2 O 2  production by HL60. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 H 2 O 2  Production: 
                 H 2 O 2  Production: 
                 Cell survival: 
                 Cell survival: 
               
               
                   
                 cations 
                 As 2 O 3  + cations 
                 cations 
                 As 2 O 3  + cations 
               
               
                 Cations 
                 vs control 
                 vs As 2 O 3   
                 vs control 
                 vs As 2 O 3   
               
               
                   
               
             
            
               
                 FeSO 4   
                 4 μM (test 1) 
                 4 μM (test 1) 
                 Not significant 
                 Not significant 
               
               
                 2 tests 
                 Not significant 
                 2 and 4 μM (test 2) 
                 (tests 1 and 2) 
                 (tests 1 and 2) 
               
               
                   
                 (test 2) 
               
               
                 HAuCl 2   
                 Not significant 
                 1 μM (test 1) 
                 Not significant 
                 Not significant 
               
               
                 2 tests 
                 (tests 1 and 2) 
                 0.5 μM (test 2) 
                 (tests 1 and 2) 
                 (tests 1 and 2) 
               
               
                 ZnSO 4   
                 Not significant 
                 Not significant 
                 Not significant 
                 Not significant 
               
               
                 2 tests 
                 (test 1) 
                 (test 1) 
                 (test 1) 
                 (tests 1 and 2) 
               
               
                   
                 50 μM (test 2) 
                 12.5, 25 and 50 μM 
                 25 and 50 μM 
               
               
                   
                   
                 (test 2) 
                 (test 2) 
               
               
                 ZnCl 2   
                 12.5 μM 
                 Not significant 
                 Not significant 
                 Not significant 
               
               
                 1 test 
               
               
                 MnSO 4   
                 0.25, 0.5, 1 μM 
                 0.25, 0.5 and 1 μM 
                 0.5 μM (test 1) 
                 Not significant 
               
               
                 2 tests 
                 (tests 1 and 2) 
                 (test 1) 
                 Not significant 
                 (tests 1 and 2) 
               
               
                   
                   
                 0.5 and 1 μM 
                 (test 2) 
               
               
                   
                   
                 (test 2) 
               
               
                 MnCl 2   
                 1 μM 
                 1 μM 
                 Not significant 
                 Not significant 
               
               
                 1 test 
               
               
                 CuSO 4   
                 Not significant 
                 0.5, 1, 2 and 4 μM 
                 Not significant 
                 Not significant 
               
               
                 2 tests 
                 (test 1) 
                 (tests 1 and 2) 
                 (test 1) 
                 (test 1) 
               
               
                   
                 0.5, 1, 2 and 4 μM 
                   
                 4 μM (test 2) 
                 0.5, 1, 2 and 
               
               
                   
                 (test 2) 
                   
                   
                 4 μM (test 2) 
               
               
                 CuCl 2   
                 Not significant 
                 0.5, 1, 2 and 4 μM 
                 Not significant 
                 Not significant 
               
               
                 2 tests 
                 (tests 1 and 2) 
                 (test 1) 
                 (tests 1 and 2) 
                 (tests 1 and 2) 
               
               
                   
                   
                 1, 2 and 4 μM 
               
               
                   
                   
                 (test 2) 
               
               
                   
               
               
                 Note: 
               
               
                 several tests have been performed to check the effect of a sequential deposit of As 2 O 3  followed by metal ions (or the opposite: metal ions + As 2 O 3 ) or a mix of the two actives ingredients. No significant difference was found between the series of tests (data not shown). 
               
            
           
         
       
     
     Conclusion 
     Copper ions have no effect on HL60 viability, alone or in the presence of As 2 O 3  but significantly increase the effect of As 203  on H 2 O 2  production, in a dose-dependent manner. CuCl 2  was chosen for further analysis because it has (and is immediately available in industrial quantities with) a GMP quality grade. 
     Example 3: Effects of Combination of As 2 O 3  and CuCl 2  on H 2 O 2  and GSH Production and Cell Survival of HL60 Cells 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates and incubated for 48 hours in complete medium with or without arsenic trioxide at several concentrations (0.1; 0.5; 1; 5 and 10 μM) and with and without CuCl 2  at 1 and 4 μM in an incubator at 37° C. 5% CO 2 . 
     Effects of the Combination of As 2 O 3  and CuCl 2 : 
     CuCl 2  at 1 and 4 μM significantly increases the H 2 O 2  production induced by As 2 O 3  at all concentrations ( FIG. 10 , left-upper panel). 
     CuCl 2  at 1 and 4 μM reduce the GSH production induced by As 2 O 3 , mainly at 1 and 5 μM of As 2 O 3  ( FIG. 10 , left-lower panel). 
     CuCl 2  at 1 and 4 μM has no additional nor protective effect on HL60 survival in the presence of As 2 O 3  ( FIG. 10 , right-hand panels). 
     Conclusion 
     CuCl 2 , tested at 1 and 4 μM with a large range of As 2 O 3  concentrations, shows no additional nor protective effect on HL60 survival but has an additional effect on H 2 O 2  production and a negative effect on GSH production. 
     Example 4: Effects of Combination of As 2 O 3  and CuCl 2  on GSH Production and Cell Survival of HL60 Cells 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates and incubated for 48 hours in complete medium with or without arsenic trioxide at 1 μM and with and without CuCl 2  at 0.5, 1, 2 and 4 μM in an incubator at 37° C. 5% CO 2 . 
     Effects of the Combination of As 2 O 3  (1 μM) and CuCl 2  (0.5, 1, 2 and 4 μM) 
     As 2 O 3  at 1 μM significantly increases GSH production. In test 1, CuCl 2  reduces the increase of GSH induced by As 2 O 3 , but this effect was only observed at higher concentrations ( FIG. 11 , upper panels). 
     CuCl 2  alone, at any of the 4 tested concentrations, has no significant effect on GSH production ( FIG. 11 , upper panels). 
     CuCl 2 , at any of the 4 tested concentrations, alone or with As 2 O 3 , has no significant effect on cell viability ( FIG. 11 , lower panels). 
     Table 2 displays the significant results on GSH production. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Cell survival: 
               
               
                   
                 GSH Production: 
                 GSH Production: 
                 Cell survival: 
                 As 2 O 3  + 
               
               
                   
                 cations 
                 As 2 O 3  + cations 
                 cations 
                 cations 
               
               
                   
                 vs control 
                 vs As 2 O 3   
                 vs control 
                 vs As 2 O 3   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 CuCl2: 
                 Not significant 
                 4 μM (test 1) 
                 Not significant 
                 Not significant 
               
               
                 (2 tests) 
                 (tests 1 and 2) 
                 2 and 4 μM (test 2) 
                 (tests 1 and 2) 
                 (tests 1 and 2) 
               
               
                   
               
            
           
         
       
     
     Conclusion 
     These results confirm the strong potentiating action of copper on As 2 O 3 -induced oxidative stress on HL60 cells. 
     Example 5: Effects of Combinations of As 2 O 3  and Metal Ions on the Proliferation of C57BL6 Mice Splenic Cells in a Mixed Lymphocyte Reaction (MLR) 
     Mixed lymphocyte reaction (MLR) is an ex vivo cellular immune assay that occurs between two allogeneic lymphocyte populations (same species but genetically distinct). The two populations of lymphocytes are incubated together, and the reaction that occurs is measured. 
     Here, MLR is used as a model of autoimmune reaction which corresponds to an in vitro proliferation of splenic cells from C57BL6 mice exposed to and stimulated by irradiated splenic cells from BalbC mice. This in vitro technique mimics the lymphocyte reaction that happens in vivo in graft versus host disease (GvHD) following allogenic hemapoietic stem cells transplant. 
     In vitro cell proliferation assays were performed on spleen cells from C57BL6 mice co-cultured with previously in vitro irradiated (30 Gray) BALB/c spleen cells. 
     For proliferation assays, the cells (6×10 5  cells/well/strain) were inoculated in 96-well plates (Falcon, Corning, reference: 353077) and incubated for 48 hours in complete medium with or without arsenic trioxide 1 μM (As 2 O 3 ), with or without different cations or with culture medium alone in an incubator at 37° C. 5% CO 2 . The results presented come from 2 independent experiments, and the cations have different quality levels, as described above in the section regarding materials and methods. 
     The results of these experiments on spleen cells for Controls, FeSO 4 , HAuCl 2 , Zn 2+  salts (ZnSO 4  and ZnCl 2 ), Mn 2+  salts (MnSO 4  and MnCl 2 ) and Cu 2+  salts (CuSO 4  and CuCl 2 ) are illustrated in  FIGS. 12 to 17 , respectively. The statistically significant differences are represented on the figures as follows:
         control cells vs cells treated by As 2 O 3      control cells vs cells treated by cations only, and   cells treated by As 2 O 3  vs cells treated by As 2 O 3 + cations.       

     Validation of culture conditions:  FIG. 12  shows the controls of proliferation measurement (4 independent tests): splenic cells from C57BL6 mice alone and splenic cells from BALB/c mice alone do not proliferate. In contrast, mixed cells show a lymphocyte reaction and a proliferation equal to that obtained in the presence of mitogen (CD3 5 μg/ml/CD28 2 μg/ml). Arsenic trioxide (1 μM) completely inhibits cell proliferation in the presence of mitogen. 
     Note: several tests have been performed to check the effect of a sequential deposit of As 2 O 3  followed by metal ions (or the opposite metal ions+As 2 O 3 ) or a solution of the two agents. No significant difference was found between the series of tests (data not shown). 
     Effects of Combinations of As 2 O 3  and Metal Ions 
     FeSO 4  does not have a significant effect on cell proliferation, either alone or with As 2 O 3  ( FIG. 13 ). 
     HAuCl 2  decreases the cell proliferation alone but this effect is limited at 1 μM with As 2 O 3  and only for test 1 (p&lt;0.001,  FIG. 14 ). 
     ZnSO 4  and ZnCl 2  decrease the cell proliferation alone, but this effect is limited at 50 μM with As 2 O 3  and only for test 1 (p&lt;0.01 and p&lt;0,001 respectively,  FIG. 15 ). 
     MnSO 4  and MnCl 2  significantly decrease the cell proliferation alone, but this effect is limited at 1 μM with As 2 O 3  and only for test 1 ( FIG. 16 ). 
     CuSO 4  and CuCl 2  significantly decrease the cell proliferation alone and this effect is significant at 4 μM or 2 and 4 μM with As 2 O 3  (p&lt;0.001,  FIG. 17 ). 
     Table 3 displays the significant results on cell proliferation decrease. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 Cell proliferation: 
               
               
                   
                 Cell proliferation: 
                 As 2 O 3  + 
               
               
                 Cations 
                 Cations vs control 
                 cations vs As 2 O 3   
               
               
                   
               
             
            
               
                 FeSO 4  (2 tests) 
                 Not significant (test 1) 
                 Not significant 
               
               
                   
                 0.5 μM (test 2) 
                 (tests 1 and 2) 
               
               
                 HauCl 2  (2 tests) 
                 0.125, 0.50 and 1 μM (tests 1 
                 1 μM (test 1) 
               
               
                   
                 and 2) 
                 Not significant (test 2) 
               
               
                 ZnSO 4  (2 tests) 
                 6, 25 &amp; 50 μM (test 1) 
                 50 μM (test 1) 
               
               
                   
                 6 &amp; 50 μM (test 2) 
                 Not significant (test 2) 
               
               
                 ZnCl 2  (2 tests) 
                 6 &amp; 50 μM (test 1) 
                 50 μM (test 1) 
               
               
                   
                 6, 12.5, 25 and 50 μM (test 2) 
                 Not significant (test 2) 
               
               
                 MnSO 4  (2 tests) 
                 0.125, 0.25, 0.50, 1 μM (tests 
                 1 μM (test 1) 
               
               
                   
                 1 and 2) 
                 Not significant (test 2) 
               
               
                 MnCl 2  (2 tests) 
                 Not significant (test 1) 
                 Not significant 
               
               
                   
                 0.125, 0.25, 0.50 and 1 μM 
                 (tests 1 and 2) 
               
               
                   
                 (test 2) 
               
               
                 CuSO 4  (2 tests) 
                 0.5, 1, 2 and 4 μM (tests 1 
                 2 and 4 μM (test 1) 
               
               
                   
                 and 2) 
                 Not significant (test 2) 
               
               
                 CuCl 2  (2 tests) 
                 0.5, 1, 2 and 4 μM (tests 1 
                 4 μM (test 1) 
               
               
                   
                 and 2) 
                 2 and 4 μM (test 2) 
               
               
                   
               
            
           
         
       
     
     Conclusion 
     Cu2+ is the most efficient metal ion for reducing the mixed lymphocyte reaction; changing the composition of the salt (CuSO 4  or CuCl 2 ) or the quality grade does not have any influence on the targeted effect. 
     Example 6: Effects of Combinations of As 2 O 3  and CuCl 2  on H 2 O 2  and GSH Production and Cell Survival of A20 Cells 
     A20 is a murine lymphoma cell line derived from a spontaneous reticulum cell neoplasm of a Balb/C AnN mouse. In this study, arsenic was tested on a murine cell line of cancer cells to study its effect in the same way as for HL60 cells. Indeed, the future in vivo model being performed in mice, it was necessary to check the As 2 O 3  effect on these murine cells in vitro. 
     In order to induce cell stress, the A20 cells (1×10 5  cells/well/strain) were seeded in 96-well plates and incubated for 48 hours in complete medium with or without arsenic trioxide at 1 μM and with and without CuCl 2  at 4 concentrations (0.5, 1, 2 and 4 μM) in an incubator at 37° C. 5% CO 2 . 
     The statistically significant differences are represented on the figures as follows:
         control cells vs cells treated by As 2 O 3      control cells vs cells treated by cations only   cells treated by As 2 O 3  vs cells treated by As 2 O 3 + cations.       

     Effects of combination of As 2 O 3  and CuCl 2    
     As 2 O 3  at 1 μM significantly increased the H 2 O 2  production and reduced the A20 viability (p&lt;0.001, test 1,  FIG. 18A ), but in test 2, As 2 O 3  only significantly reduced the A20 viability (p&lt;0.001,  FIG. 18B ), 
     CuCl 2  alone increased the H 2 O 2  production at any of the 4 concentrations tested (test 1 p&lt;0.001) and at 3 higher concentrations (test 2, p&lt;0.001). CuCl 2  alone apparently increased the A20 viability at 3 or 2 higher concentrations tested ( FIG. 18 ). 
     At any of the 4 tested concentrations, CuCl 2  increased the effect induced by As 2 O 3  on H 2 O 2  production (Tests 1 and 2,  FIG. 18 , left-hand panels). In the presence of As 2 O 3 , CuCl 2  slightly but significantly increased A20 viability at higher concentrations (Test 1: 2 and 4 μM and Test 2: 4 μM;  FIG. 18 , right-hand panels). 
     As 2 O 3  at 1 μM significantly increased the GSH production and significantly reduced A20 cells viability (p&lt;0.001, test 1,  FIG. 19 ). 
     CuCl 2  alone significantly decreased the GSH production and increased A20 cells viability at 2 and 4 μM (test 1;  FIG. 19 ). In the presence of As 2 O 3 , CuCl 2  significantly decreased arsenic-induced GSH production at higher concentrations and increased A20 cells viability only at 4 μM (test 1;  FIG. 19 ). 
     Tables 4 and 5 display the significant results on H 2 O 2  and GSH production and A20 viability. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 H 2 O 2   
                 H 2 O 2   
                   
                   
               
               
                   
                 Production: 
                 Production: 
                 Cell survival: 
                 Cell survival: 
               
               
                   
                 cations 
                 As 2 O 3  + cations 
                 cations 
                 As 2 O 3  + cations 
               
               
                 Cations 
                 vs control 
                 vs As 2 O 3   
                 vs control 
                 vs As 2 O 3   
               
               
                   
               
             
            
               
                 CuCl 2   
                 0.5, 1, 2 and 
                 0.5, 1, 2 and 4 μM 
                 1, 2 and 4 μM 
                 2 and 4 μM (test 1) 
               
               
                 (2 tests) 
                 4 μM (test 1) 
                 (tests 1 and 2) 
                 (test 1) 
                 4 μM (test 2) 
               
               
                   
                 1, 2 and 4 μM 
                   
                 2 and 4 μM 
               
               
                   
                 (test 2) 
                   
                 (test 2) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 GSH Production: 
                 GSH Production: 
                 Cell survival: 
                 Cell survival: 
               
               
                   
                 cations 
                 As 2 O 3  + cations 
                 cations 
                 As 2 O 3  + cations 
               
               
                 Cations 
                 vs control 
                 vs As 2 O 3   
                 vs control 
                 vs As 2 O 3   
               
               
                   
               
             
            
               
                 CuCl 2   
                 2 and 4 μM 
                 1, 2 and 4 μM 
                 2 and 4 μM 
                 4 μM 
               
               
                 (1 test) 
               
               
                   
               
            
           
         
       
     
     Conclusion 
     In the presence of As 2 O 3 , CuCl 2  significantly increased the H 2 O 2  production and decreased the GSH production without any significant effect on A20 cell survival. 
     Example 7: Effects of AsI 3  on H 2 O 2  and GSH Production and Cell Survival of HL60 Cells 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates (Falcon, Corning, reference: 353077) and incubated for 48 hours in complete medium with or without AsI 3  at several concentrations: 0.1; 0.5; 1; 5 and 10 μM in an incubator at 37° C. 5% CO 2 . 
     Effects of AsI 3  on HL60-cells: 
       FIGS. 20 to 23  show the effect of AsI 3  at increasing concentrations on the production of H 2 O 2  and GSH, and cell viability (1 test). 
     AsI 3  significantly reduced H 2 O 2  production at all tested concentrations (p&lt;0.001,  FIG. 20A ). 
     AsI 3  significantly increased GSH production at 0.1, 1 and 5 μM (p&lt;0.01, p&lt;0.001 and p&lt;0.001 respectively,  FIG. 20B ). 
     AsI 3  significantly reduced HL60 cells viability at 10 μM (p&lt;0.001,  FIG. 20C ). 
     Conclusion 
     The dose of 1 μM of AsI 3  was selected to test the effects of combinations with CuCl 2  on H 2 O 2  production and HL60-survival. 
     Example 8: Effects of Combinations of AsI 3  and CuCl 2  on H 2 O 2  Production and Cell Survival of HL60 Cells 
     In order to induce cell stress, the HL60 cells (5×10 5  cells/well/strain) were seeded in 96-well plates and incubated for 48 hours in complete medium with or without AsI 3  at 1 μM and with and without CuCl 2  at 0.5, 1, 2 and 4 μM in an incubator at 37° C. 5% CO 2 . 
     Effects of Combination of As 13  and CuCl 2 : 
     AsI 3  1 μM has not effect on H 2 O 2  production and cell survival ( FIG. 21 ). 
     Whatever the tested concentration, CuCl 2  significantly increased the effect of AsI 3  (at 1 μM) on H 2 O 2  production ( FIG. 21 , left-hand panel). CuCl 2  had no effect on cell survival in presence of AsI 3  ( FIG. 21 , right-hand panel). 
     Conclusion: 
     In the presence of AsI 3  (1 μM), there is already a significant potentializing effect of CuCl 2  on H 2 O 2  production, although it appears to be lower than that measured in the presence of As 2 O 3 . 
     Example 9: Effects of AsI 3  on the Proliferative Properties of C57Bl6 Spleen Cells During a Mixed Lymphocytic Reaction (MLR) 
     In vitro cell proliferation assays were performed on spleen cells from C57BL6 mice in co-culture with previously irradiated (30 Gray) so-called “stimulating” splenic cells from BALB/c mice. 
     For the proliferation tests, the cells (6×10 5  cells/well/strain) were seeded in 96-well plates (Falcon, Corning, reference: 353077) and incubated for 48 hours in complete medium supplemented or not, with arsenic trioxide (As 2 O 3 ) at 1 μM or with arsenic triiodide (AsI 3 ) at 1 μM in presence of mitogen or with copper at increasing concentrations, from 0.5 to 4 μM CuCl 2 . 
     Cell proliferation was determined by a spectrofluorimeter assay after 24 hours of incubation of the cells with 10% UptiBlue (20 μL in 200 μL of medium). 
     The results of arsenic trioxide (As 2 O 3 ) at 1 μM or with arsenic triiodide (AsI 3 ) at 1 μM on cell proliferation in the presence of mitogen are illustrated in  FIG. 22 . AsI 3  is only significantly active on test 2 ( FIGS. 22 and 23 , right-hand panels). 
     The results of these experiments on spleen cells for CuCl 2  with more or less arsenic triiodide (AsI 3 ) are illustrated in  FIG. 23 . 
     In the presence of AsI 3 , CuCl 2  significantly decreased the proliferation of C57BL6 spleen cells at 1, 2 and 4 μM (test 1) and at 4 μM (test 2). 
     Conclusion: 
     AsI 3  is active, but slightly less than As 2 O 3  and the synergy with CuCl 2  seems reduced, probably indicating that the important feature is the concentration in the As ion. 
     Example 10: Effects of As 2 O 3  and CuCl 2  in a Mice Model of Graft Versus Host Disease (GvHD) 
     The association of arsenic trioxide (As 2 O 3 ) and copper molecules (CuCl 2 ) was then evaluated in a well-established murine model of chronic sclerodermatous Graft versus Host Disease (Arsenic Trioxide Prevents Murine Sclerodermatous Graft-versus-Host Disease, Kavian et al., 2012). In this model, mice (female BALB/c mice-H-2d) previously sub-lethally irradiated with 7.5 Grays from a Gammacel source are grafted with bone marrow (1×10 6  cells) and splenocytes (2×10 6  cells) from mice presenting a low immune compatibility (male B10.D2 mice-H-2b). 
     7 days after transplantation, the mice received intraperitoneal injections of arsenic trioxide associated or not with copper chloride (“copper”), 5 times a week for 5 weeks. An irradiation control group was carried out to verify the irradiation efficacy and that the graft had succeeded in the recipient mice. A syngeneic group was grafted with splenocytes and bone marrow from mice of the same genetic background. This control group should not develop chronic GvHD. Once a week, a clinical assessment, scoring signs such as alopecia, weight loss, diarrhea, vasculitis allowed to evaluate the progression of the disease. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Experimental groups, with the strains of donor and 
               
               
                 recipient mice and the number of mice per group 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Number 
               
               
                 Groups 
                 Recipients 
                 Donor 
                 of mice 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Irradiation control 
                 BALB/c 
                 Ø 
                 3 
               
               
                 Syngeneic 
                 BALB/c 
                 BALB/c 
                 9 
               
               
                 Allogeneic 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g + CuCl 2  10 μg/g 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 Allogeneic + CuCl 2  10 μg/g 
                 BALB/c 
                 B10.D2 
                 7 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g + CuCl 2   
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 2.5 μg/g 
               
               
                 Allogeneic + CuCl 2  2.5 μg/g 
                 BALB/c 
                 B10.D2 
                 7 
               
               
                 Allogeneic + As 2 O 3  5 μg/g 
                 BALB/c 
                 B10.D2 
                 7 
               
               
                   
               
            
           
         
       
     
     Initial protocol: After 5 weeks, the mice should have been euthanized in order to evaluate the effect of the association of copper with arsenic trioxide on the organs affected by chronic GvHD (skin, lung, liver . . . ). 
     Protocol adjustment: Following a significant loss of mice in the copper-treated groups, the injections had to be stopped at the end of day 4. The treatment was resumed the following week on day 8 at a different rate until the end of the 5 weeks of treatment. Copper was then injected only twice a week instead of 5 in mice receiving copper, while mice treated with arsenic alone or combined to copper still received 5 injections of ATO per week. Under these new treatment conditions, no more copper-treated mice died. 
     The number of mice being greatly reduced, we decided to collect only the blood of the mice in order to perform the transaminase tests, but the organs were not harvested. These experiments show that Copper needs to be reduced to abolish its toxic effect on mice, at least when it is administered via the intraperitoneal route. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 Number of live mice at the end of the experiment 
               
               
                 compared to the initial number of mice 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Number of 
                 Number of 
               
               
                   
                   
                 mice at the 
                 mice at 
               
               
                   
                 Groups 
                 beginning 
                 the end 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Irradiation control 
                 3 
                 0 
               
               
                   
                 Syngeneic 
                 9 
                 8 
               
               
                   
                 Allogeneic 
                 10 
                 9 
               
               
                   
                 Allogeneic + As 2 O 3  2.5 μg/g 
                 10 
                 9 
               
               
                   
                 Allogeneic + As 2 O 3  2.5 μg/g + 
                 10 
                 2 
               
               
                   
                 CuCl 2  10 μg/g 
               
               
                   
                 Allogeneic + CuCl 2  10 μg/g 
                 7 
                 5 
               
               
                   
                 Allogeneic + As 2 O 3  2.5 μg/g + 
                 10 
                 3 
               
               
                   
                 CuCl 2  2.5 μg/g 
               
               
                   
                 Allogeneic + CuCl 2  2.5 μg/g 
                 7 
                 2 
               
               
                   
                 Allogeneic + As 2 O 3  5 μg/g 
                 7 
                 5 
               
               
                   
                   
               
            
           
         
       
     
     The results of this experiment are shown in Table 8 below and in  FIGS. 24 to 27 . 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Results of the experiment (alopecia) 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Number 
                 Percentage 
               
               
                   
                   
                 of mice 
                 of mice 
               
               
                   
                 Number 
                 with 
                 with 
               
               
                 Groups 
                 of mice 
                 alopecia 
                 alopecia 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Syngeneic 
                 8 
                 0 
                  0% 
               
               
                 Allogeneic 
                 9 
                 7 
                 77% 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g 
                 9 
                 3 
                 33% 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g + 
                 3 
                 0 
                  0% 
               
               
                 CuCl 2  2.5 μg/g 
               
               
                 Allogeneic + CuCl 2  2.5 μg/g 
                 2 
                 1 
                 50% 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g + 
                 2 
                 0 
                  0% 
               
               
                 CuCl 2  10 μg/g 
               
               
                 Allogeneic + CuCl 2  10 μg/g 
                 5 
                 0 
                  0% 
               
               
                 Allogeneic + As 2 O 3  5 μg/g 
                 5 
                 1 
                 20% 
               
               
                   
               
            
           
         
       
     
     Even though the number of mice per group is insufficient for significant statistics, we can still observe that none of the mice receiving a combined treatment with As 2 O 3  2.5 μg/g and CuCl 2  (2.5 or 10 μg/g) developed alopecia, which is better than mice receiving only As 2 O 3  2.5 μg/g (33% alopecia) and even better of mice receiving As 2 O 3  5 μg/g (20% alopecia) ( FIG. 24 ). This confirms that the effects of arsenic are potentiated when co-administered with Copper. 
     Concerning the weights of the mice, at the end of the treatment, there was no obvious difference between the groups even if the mice of the syngeneic group seemed to have a higher weight than the mice of the other groups ( FIG. 25 ). 
     Mice in the allogeneic group show an increase in ear thickness (vasculitis) compared to mice in the syngeneic group. We also observe that in the allogeneic group+As 2 O 3  2.5 μg/g, vasculitis was reduced and in the allogenic group+5 μg/g, it decreased even more until reaching the same values as the ones of the syngeneic group. ( FIG. 26 ) 
     Regarding the hepatic balance of animals, results obtained for sera transaminases are not consistent. This may be due to a variable toxic effect of our repeated intraperitoneal injections of arsenic trioxide and copper, liver being exposed to variable amounts depending on the particular site of each injection, and thus variable deleterious effects ( FIG. 27 ). 
     Example 11: Effects of As 2 O 3  and CuCl 2  in a Mice Model of Graft Versus Host Disease (GvHD), with a Lower Dosage of CuCl 2    
     Following these results, we decided to perform a copper cytotoxicity assessment. To this aim, we injected a lower dose of copper (0.2 and 0.5 μg/g) 5 times a week for 5 weeks to a new series of BALB/c mice. We observed the mice every day, monitored their weight and followed their survival to evaluate copper toxicity. 
     After 5 weeks, there was no death and the mean weights were similar between the control group receiving PBS and the groups receiving copper at 0.2 and 0.5 μg/g. The dosage of 0.5 μg/g was thus chosen for a new set of experiments, using the same protocol as described in Example 10, but with the conditions described in Table 9 below. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Experimental groups, with the strains of donor and 
               
               
                 recipient mice and the number of mice per group 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Number 
               
               
                 Groups 
                 Recipients 
                 Donor 
                 of mice 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Irradiation control 
                 BALB/c 
                 Ø 
                 3 
               
               
                 Syngeneic 
                 BALB/c 
                 BALB/c 
                 7 
               
               
                 Allogeneic 
                 BALB/c 
                 B10.D2 
                 7 
               
               
                 Allogeneic + AS 2 O 3  2.5 μg/g 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 Allogeneic + As 2 O 3  2.5 μg/g + CuCl 2   
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 0.5 μg/g 
               
               
                 Allogeneic + CuCl 2  0.5 μg/g 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                 Allogeneic + As 2 O 3  5 μg/g 
                 BALB/c 
                 B10.D2 
                 10 
               
               
                   
               
            
           
         
       
     
     Unfortunately, this series of experiments was interrupted because of the closure of the laboratory due to the COVID-19 crisis on Mar. 11, 2020. The experiments will be restarted upon reopening of the laboratory.