Zinc and tetrathiomolybdate for the treatment of Wilson’s disease and the potential efficacy of anticopper therapy in a wide variety of diseases

Abstract

Wilson’s disease, an autosomal recessive disease of copper accumulation and copper toxicity primarily in the liver and brain, has been the engine that has driven the development of anticopper drugs. Here we first briefly review Wilson’s disease, then review the four anticopper drugs used to treat Wilson’s disease. We then discuss the results of therapy with anticopper drugs in Wilson’s disease, with special emphasis on the newer and better drugs, zinc and tetrathiomolybdate. We then discuss new areas of anticopper therapy, lowering copper availability with tetrathiomolybdate as a therapy in fibrotic, inflammatory, and autoimmune disorders. Many of the cytokines which promote these disorders are copper dependent, and lowering copper availability lessens the activity of these cytokines, favorably influencing a variety of disease processes. Copper in the blood can be thought of as in two pools. One pool is covalently bound in ceruloplasmin, a protein containing six coppers, synthesized by the liver and secreted into the blood. Ceruloplasmin copper accounts for almost 85 to 90% of the blood copper in normal people. This copper is tightly bound and not readily available for cellular uptake and copper toxicity. The other 10–15% of copper is more loosely bound to albumin and other small molecules in the blood, and is readily and freely available to cells and available to cause copper toxicity, if this pool of copper is increased. We call this latter pool of copper “free” copper because of its more ready availability. However, it should be understood that it is not completely free, always being bound to albumin and other molecules. It is this pool of free copper that is greatly expanded in untreated Wilson’s patients undergoing copper toxicity.

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George J. Brewer

Dr Brewer is a physician and emeritus professor of Human Genetics and Internal Medicine at the University of Michigan. He has worked on zinc, copper and molybdenum interactions for the past 35 years. His group was responsible for developing zinc as an FDA approved Wilson’s disease maintenance therapy, and for a series of positive studies on tetrathiomolybdate treatment of the neurologic presentation of Wilson’s disease, and in evaluating tetrathiomolybdate efficacy in a wide array of fibrotic, inflammatory, and autoimmune diseases.

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I. Overview of Wilson’s disease

Wilson’s disease is an autosomal recessive inherited disease of copper accumulation and copper toxicity.^1–6 Wilson, for whom the disease is named, published early on the syndrome of concomitant liver and brain damage, which has been called hepatocerebellar degeneration.⁷ The etiologic role of copper was gradually established in the early 20th century by findings of elevated levels of copper in liver and brain tissue and in urine.^8–10 It was found that the body’s copper balance was maintained by excreting excessive copper in the bile for loss in the stool,¹¹ and it was later discovered that Wilson’s disease patients did not excrete this excess copper in the bile.¹² Finally, the causative gene, located on chromosome 13, was cloned and named ATP7B.^13–15 This gene produces a protein product in the liver which acts in the pathway of biliary copper excretion and is also responsible for attaching copper to ceruloplasmin. Wilson’s disease patients have mutations in both copies of this gene such that biliary copper excretion is blocked or impaired and secretion of copper containing ceruloplasmin is low, leading to a low blood ceruloplasmin in Wilson’s disease. There are by now several hundred causative mutations known¹⁶ and while some are fairly common in some populations, no small set of mutations allowing easy DNA testing exist, so diagnosis is still primarily dependent on abnormalities of copper levels.

Copper is an essential trace element. Humans ingest about 1.0 mg of copper per day in the diet, and about 0.75 mg of that is required to balance obligatory losses from skin, urine and stool. The other 0.25 mg is excess, and must be excreted in the bile to maintain copper balance. Because Wilson’s disease patients have a block in the biliary excretion of copper, they accumulate a little copper every day of their lives. At first the excess copper is stored in the liver, which begins to be damaged by the copper early in childhood. The disease may declare itself clinically in about 50% of patients in the second or third decade of life as liver disease, presenting as hepatitis, liver failure, or chronic cirrhosis. As the ability of the liver to store copper is exceeded, circulating levels of copper, and levels in other organs increase. The next most sensitive organ is the brain. About 50% of the patients present with neurologic symptoms of a movement disorder, usually presenting from about age 15 to 30.¹⁷ The areas of the brain that coordinate movements, such as the basal ganglia, are especially injured. In about half of patients who present neurologically, the neurologic signs and symptoms are preceded by, and accompanied by, behavioral abnormalities.¹⁸ These may exist for 2 or 3 years before the neurologic symptoms. The most common are loss of ability to focus (often leading to job loss or decline in school performance), change in temperament (such as loss of temper control), depression, memory loss, and insomnia. Occasionally patients have hallucinations or lose sexual inhibitions.

Female patients may have had one or more abortions prior to becoming symptomatic, and usually lose menstruation 1 or 2 years before the symptomatic point (personal observations). Other occasional presenting clinical signs and symptoms include osteoarthritis, especially of the knee, and sunflower cataract. Patients presenting neurologically have brownish copper rings at the outer circumference of their corneas, called Kayser–Fleischer (KF) rings, sometimes visually apparent but always detectable by slit lamp examination. These rings are present in only about 50% of patients who present with liver disease.

Some patients may be detected at the “presymptomatic” state by chance observation of KF rings, detection of subclinical liver disease, or more often by family workup of siblings of a diagnosed patient. Since this disease is an autosomal recessive, full siblings of an affected person have a 25% risk of also having the disease. Presymptomatic patients should always be treated prophylactically, since the disease is close to 100% penetrant.

The natural history of the disease without treatment is almost always progression of either or both liver disease and neurologic disease, and eventually death. As already mentioned presymptomatic patients without treatment will become symptomatic and progress to the same fate. The one exception to these statements is that we have observed that vegetarianism may halt or prevent the progression of the disease.¹⁹ The mechanism of this lies in the fact that copper is more poorly absorbed from vegetable foods than from meat.

The pathogenesis of the disease is due to copper toxicity.⁴ One of the best pieces of evidence for this is that drugs which accomplish lowering of body copper levels are beneficial and allow improvement as copper levels are lowered. Copper is redox active and causes toxicity through oxidant mechanisms.⁴ Free copper is so toxic that it is almost always bound. In cells it is bound to chaperones that target specific receptorproteins, or bound to storage proteins such as metallothionein. In the blood, in normal people, 90% of circulating copper is covalently bound to ceruloplasmin, and this is “safe” copper. The other 10% is more loosely bound to albumin , other proteins, polypeptides, and other small molecules. Because of its more exchangeable nature, this latter copper is called “free” copper. This free copper pool in the blood is greatly expanded in Wilson’s disease, and is intimately related to copper toxicity in various organs. This free copper pool is reduced by the anticopper drugs used to treat Wilson’s disease.

Making the diagnosis of Wilson’s disease is important because it is very treatable. The main problem in diagnosis is thinking of the possibility of the disease. Wilson’s disease is rare, in the order of one in 30 000 births, leading to a theoretical patient load of about 10 000 in the US. The occasional case of Wilson’s disease is buried among much more frequent cases of viral hepatitis, alcoholic cirrhosis, nonalcoholic steatohepatitis, Parkinson’s disease, essential tremor, drug abuse, and various psychiatric diagnoses.^1,3 A good screening test is 24 hour urine copper, which is invariably elevated over 100 μg in symptomatic patients. KF rings examination by slit lamp in neurologically presenting patients is extremely useful because they are invariably present. Blood ceruloplasmin is low in most patients, but 10–20% of affected patients have a normal or near normal value, and 10–20% of gene carriers have a relatively low value. The gold standard for diagnosis is a quantitative liver copper from a liver biopsy. The liver copper is almost always over 200 μg/g dry weight of liver. Normal is below 50 μg and gene carriers are rarely over 100 μg. About 25% of patients don’t have mutations in the coding part of the gene, and because of the plethora of causative mutations, mutation analyses are so far not highly useful, but DNAhaplotype analysis is very reliable for genotyping siblings of an affected case.

II. Overview of therapeutic agents for Wilson’s disease

Many drugs are used to treat the hepatic, neurologic and psychiatric manifestations of Wilson’s disease, but here we will deal only with the agents designed to attack the basic cause of the disease, excess copper. These drugs are called anticopper drugs, and there are three commercially available, and one in development.

1. Penicillamine

The first oral anticopper drug was penicillamine, developed by Walshe.²⁰ Penicillamine is a reductive chelator, which means it reduces copper, which causes copper to have lesser affinity for proteins, allowing penicillamine to bind the copper. It acts by causing a rather large excretion of copper in the urine. In untreated Wilson’s disease, the patient may be excreting up to 200 or 300 μg of copper per day in the urine. With penicillamine treatment this increases greatly, up to 1.0 to 1.5 mg per day in newly treated patients. This is more than enough to put the patient in a strong negative copper balance, and begin depleting the excess stores of copper. As copper is depleted, over time the amount of copper in the urine decreases to as low as 200–300 μg per day. In about six months liver function tests usually begin to improve and are often back to normal in 12 months. Neurological and psychiatric abnormalities may also begin to improve in six months and improvement may continue up to about 24 months after treatment initiation. This is assuming the patient doesn’t undergo initial neurologic worsening which is a major risk with penicillamine, discussed below. Neurologic symptoms still present after 24 months are usually permanent.

The dose of penicillamine is 1.0 g per day, usually given as 250 mg four times per day or 500 mg two times per day. Doses should be given at least 30 minutes before meals or at least two hours after meals. As copper levels are adequately controlled the dose can often be decreased to 500 to 750 mg per day. To monitor therapy, the 24 hour urine copper can be monitored, but it is not very useful because it reflects both body loading with copper and the therapeutic effect of the drug. The best monitoring approach is to follow free copper in the blood by simultaneous measurement of total serum copper and ceruloplasmin and subtracting the ceruloplasmin copper from the total. Each mg of ceruloplasmin contains 3 μg of copper. Thus, for example if the total serum copper is 40 μg/dl, and ceruloplasmin is 10 mg/dl, multiplying 10 times 3 = 30 μg of copper/dl in ceruloplasmin. 30 is subtracted from 40 to yield a value of 10 μg/dl of free copper in this example. A value of 10–15 μg/dl indicates good copper control.

Unfortunately, penicillamine has a very long list of side effects.^1,4 About 25–30% of patients have an initial hypersensitivity reaction. This can often be overcome by steroid administration, or by stopping the penicillamine, and restarting at a low dose and working up. The drug can also cause bone marrow depression, various types of skin abnormalities such as excessive wrinkling, proteinuria, a long list of autoimmune disorders such as systemic lupus erythematosus and Goodpasture’s syndrome, interference with connective tissue formation increasing the risk of aneurysms, etc. A major problem with penicillamine is that when it is used for initial treatment of neurologically presenting patients, 50% of them get worse, probably as a result of mobilizing hepatic copper and flushing it through the system, temporarily further elevating brain copper.²¹ Half of the patients who worsen never recover, and are often left with very serious disabilities. Penicillamine is also teratogenic if used during pregnancy. For all these reasons, we do not recommend penicillamine for the treatment of any phase of Wilson’s disease.

Penicillamine is FDA approved for the treatment of Wilson’s disease, with no restrictions on the phase or type of the disease being treated, but as mentioned above, we do not recommend its use.

2. Trientine

Because the large number of side effects made it impossible for some Wilson’s disease patients to take penicillamine, Walshe²² later developed trientine, another oral chelator for use by these patients. The dose of trientine, and the prohibitions against concomitant food intake are identical to those with penicillamine. The recommended monitoring system, using free copper values in the serum, is also identical to that recommended for penicillamine. Trientine also increases the urine copper, although not as markedly as penicillamine, but enough to put the patient in a negative copper balance and deplete the excess stores of copper. Over time the urine copper gradually decreases, to as low as 100 μg per day. The time course of improvement in liver function, neurologic function and psychiatric function is much like that of penicillamine.

Although trientine shares most of the side effects that penicillamine exhibits they occur at a much lower frequency than with penicillamine. A relatively prevalent one is proteinuria. Trientine also shares with penicillamine the risk of making neurologically presenting patients worse neurologically. This occurred 26% of the time in one of our studies, and patients who worsened generally did not do well.²³

Trientine is approved for use in patients intolerant of penicillamine but is currently seeing broader use. There are a fairly large number of anecdotal reports that it is safe during pregnancy. We believe it is safe to use trientine in patients with Wilson’s disease except for those presenting neurologically.

3. Zinc

Schouwink in the Netherlands first treated Wilson’s disease patients with zinc, but never published his work (they appeared in a thesis, ref. 24). Hoogenraad et al., also in the Netherlands followed up on this work and published on the use of zinc sulfate to treat Wilson’s disease patients.^25,26 Independently we made observations that zinc therapy produced copper deficiency in sickle cell patients,²⁷ and decided to try to develop zinc acetate as a therapy for Wilson’s disease. Over the following 20 years we did all the careful systematic work that led to FDA approval of zinc as a therapy for Wilson’s disease in 1997.^28–42

Zinc acts by inducing metallothionein in the intestinal cell,³⁷ which then binds copper from food and endogenous secretions and prevents its transfer to blood. Intestinal cells slough into the stool with about a six day turnover time and take the bound copper with them. It takes about 2 weeks of a minimal dose of 37.5 mg of zinc (expressed as elemental zinc) two times per day or 25 mg three times/day, to induce metallothionein and block copper absorption. Deinduction takes a similar period of time.³⁷ Taking a single daily dose of zinc, even in large amounts, seems to be ineffective. The zinc must be separated from food, preferably at least one hour before and at least two hours after meals, to be effective.

Early in our development of zinc, we did dose and regimen studies using copper balance and oral ⁶⁴Cu absorption assays as methods of evaluating efficacy, and established the need for minimal dosing as described earlier (a minimum of 37.5 mg twice daily, each dose separated from food).^28,35,39 Many studies were done to show that 25 mg three times/day, 50 mg two times/day, and 50 mg three times/day were always effective in producing negative copper balance and blocking oral ⁶⁴Cu absorption. After that we settled on 50 mg three times/day as the standard adult dose, and this is the dose approved by the FDA.

We did studies to show the mechanism of action, namely, the induction of intestinal cell metallothionein to block absorption.³⁷ We did studies to evaluate putative toxicities, namely pancreatitis,³² adverse effects on lymphocytes,⁴¹ and adverse effects on cholesterol metabolism,³⁶ and showed that these putative toxicities did not occur. We evaluated the possible value of combinations of zinc with trientine or penicillamine for maintenance therapy, and found that zinc alone was just as effective in producing negative copper balance as the combination.³⁸

The main side effect of zinc is gastric intolerance. Taken on an empty stomach zinc produces discomfort such as burning or nausea in up to 10% of patients; Particularly when they first start. The first morning dose is often the culprit; And taking that dose between breakfast and lunch may fix the problem. It is also acceptable to take offending doses with a little protein such as meat, cheese or jello, since protein interferes the least with zinc action. Other putative side effects of zinc have been disproven.^32,36,41,42 Zinc therapy will elevate serum amylase, lipase and alkaline phosphates a little, but this appears to be simply due to induction of higher levels of these enzymes in the pancreas and liver rather than due to organ damage.³²

Zinc is approved for the maintenance therapy of Wilson’s disease. It can also be used for the treatment of presymptomatic patients from the beginning.⁴⁰ These are usually patients diagnosed during family screening of a diagnosed patient, who have not yet developed clinical evidence of Wilson’s disease. It is also an effective therapy during pregnancy⁴³ and is generally safe for the fetus. It can be used in pediatric patients at a reduced dose, as discussed earlier.⁴⁴

4. Tetrathiomolybdate

Structurally, tetrathiomolybdate (TM) consists of a molybdenum molecule surrounded by four sulfhydryl groups. It forms a tripartite complex with protein (almost any protein will do), copper, and itself. This complex is very stable. The way TM is given allows two mechanisms of action.⁴⁵ Given with food, it binds copper in the food, as well as copper in endogenous secretions such as saliva and gastric juice, with food protein. This complex is not broken down and is excreted in the stool. This mechanism produces an immediate negative copper balance.⁴⁵ Second, if TM is given away from food, it is well absorbed and forms the tripartite complex with serum albumin and the free copper of the blood. This complex is not available for cellular uptake. It builds up in the blood, and is slowly metabolized by the liver and the components excreted in the bile. In this manner it is possible to bind up all the free copper in the blood, and reduce it to zero, within two weeks or less.^45–48 Since free copper in the blood is in equilibrium with free copper in the organs, with TM it is possible to stop further copper toxicity quickly.

The most studied dose of TM is 120 mg/day, 20 mg three times/day with meals, and 20 mg three times/day between meals, given for 8 weeks.

Tetrathiomolybdate given in the above dose has two main side effects.²³ One is anemia with or without leukopenia that occurs in 10–15% of patients. This appears to be due to bone marrow depletion of copper, since the patients who exhibit this side effect also show the best and quickest copper control. It is easily overcome by a temporary drug holiday and resuming at half the standard dose. The second side effect is a further elevation of transaminase levels, which also occurs in 10–15% of patients. Since we haven’t seen this in several hundred non-Wilson’s patients given TM,^49–53 we believe it is caused by the increased hepatic copper in the liver of Wilson’s disease patients. We know that TM can take copper off the storage protein, metallothionein, and it seems that the shifting pools of copper may temporarily exacerbate hepatitis. Liver function tests other than the transaminases are unaffected, and the increases are transitory, particularly if the dose is reduced to half levels (60 mg/day). Because these two side effects don’t occur in the first weeks of therapy, we have tried a drug regimen of 120 mg of TM for two weeks, then 60 mg of TM for 14 weeks. This approach significantly reduces side effects.⁵⁴

Tetrathiomolybdate has not yet been approved for the treatment of Wilson’s disease.

III. Results of anticopper drug therapy in Wilson’s disease

Please see Table 1 for our recommendations for treating various phases of Wilson’s disease.

Table 1 The author’s preferential treatments for various phases of Wilson’s disease

Phase of the disease	First choice	Second choice
Maintenance therapy	Zinc	Trientine
Pregnancy	Zinc	Trientine
Pediatrics	Zinc	Trientine
Initial therapy
Neurologic	Tetrathiomolybdate	Zinc
Hepatic (non-fulminant)	Trientine and zinc	Penicillamine and zinc
Hepatic (fulminant)	Liver transplantation	Trientine and zinc

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1. Zinc

The recommended dose of zinc for adults is 50 mg three times/day, to provide a safety factor, although as pointed out above, 50 mg two times/day is effective if taken faithfully. For children, we recommend treating as soon as the diagnosis is made, with a dose of 25 mg two times/day until age five years, then 25 mg three times/day until age 15 or a body weight of 125 pounds, then 50 mg three times/day.

Zinc therapy can be easily monitored by following 24 hour urine copper and zinc. Since the action of zinc is on stool copper, the urine copper is solely a reflection of the body loading of copper. At the time of initiation of zinc therapy, depending on prior treatment with other anticopper agents, 24 hour urine copper may be quite elevated, up to 250 μg or higher (normal is 20–50 μg). With zinc therapy this will come down over a year’s period to less than 125 μg and level out, returning towards normal levels only after many years of treatment.⁴² A value below 125 μg indicates good control. It is useful to measure 24 hour zinc on the same urine sample. A zinc treated patient taking their medication properly will have a 24 hour urine zinc of at least 2.0 mg.⁴² If the urine zinc falls below that, which it will do in a few days of inadequate treatment, it is an early warning of poor compliance. It takes some weeks or even months for urine copper to go up during poor compliance, so the urine zinc gives a good early warning.

The results of maintenance therapy with zinc and prolonged followup in a large series of Wilson’s disease patients were subsequently published.⁴² This followup was as long as 15 years in many patients and as long as 10 years in a larger number of patients. We used 24 hour urine zinc and copper, often obtained with a mail-in kit system, to monitor patients. We found zinc to be completely effective in controlling copper levels, and preventing recurrence of symptoms related to copper toxicity, except during periods of non-compliance. Non-compliance was easily documented by inadequate urine zinc levels. (In patients with adequate compliance, 24 hour urine zinc should be over 2.0 mg, with normal, untreated levels being 0.2 to 0.5 mg). Non-compliance is the major problem in the chronic life-long treatment of any illness, especially in young people. In our study we saw major non-compliance in 10% of patients and episodic non-compliance in 25%.⁴²

Special groups of Wilson’s disease patients undergoing zinc therapy were also studied . Thirteen presymptomatic patients received zinc from the beginning, never became symptomatic, and had well controlled copper levels.⁴⁰ Nineteen pregnant patients were treated with zinc therapy during pregnancy resulting in 26 babies, all but two of whom were completely normal.⁴³ One baby had a minor heart defect correctable by surgery, and one baby was microcephalic. The two mothers involved had relatively low urine copper levels. Since copper deficiency is a known teratogen, we now recommend that copper level control be loosened during pregnancy. This advice also probably applies to the use of trientine during pregnancy. We also treated a number of Wilson’s disease children with zinc, and developed pediatric dosing regimens of 25 mg twice daily until age 5 years, 25 mg three times daily until age 15 years or a body weight of 125 pounds, and then 50 mg three times/day.⁴⁴ This dosing regimen was subsequently adopted by another group, who used it successfully in a larger study of children.⁵⁵

2. Tetrathiomolybdate

In our opinion, penicillamine and trientine are contraindicated in the treatment of the initial presentation of neurologic Wilson’s disease, because of a high risk of causing disastrous neurologic worsening. Zinc is too slow acting for these patients, taking 9–12 months to control copper toxicity, during which time the disease can progress due to its natural history. Thus, we have been developing tetrathiomolybdate (TM), for this purpose.

In open label dose ranging studies of neurologically presenting Wilson’s disease patients, we established that 120 mg day, equally divided in with meal and between meal doses of 20 mg each, was as effective as higher doses in reducing blood free copper levels to zero within a short period of time.⁴⁸ We also established that eight weeks of therapy was adequate in terms of prolonged control of free copper levels and in terms of stabilizing neurologic function. We started zinc for maintenance therapy purposes at the 6 week point in some patients, and from the beginning in others, and it made no difference to either of the above endpoints. Thus, in subsequent studies we started zinc from the beginning of TM therapy, because it may offer some help with copper toxicity in the liver, by induced hepatic metallothionein and binding up some of the toxic copper. With the help of a neurologist who had worked in Huntington’s disease, a somewhat similar neurologic movement disorder, we developed a semiquantitative neurologic scoring test (SNST) to evaluate neurologic function during TM therapy. This test had potential scores ranging from 0 (normal) to 38 (severe impairment). We found that 5 points deterioration indicated significant neurologic deterioration.⁴⁸

In 55 scorable patients in the open label study of TM, only 2 reached our criteria for neurologic worsening (3.6%).⁴⁸ We believe that an occasional patient will deteriorate no matter what drug is used because of the natural history of the disease, while penicillamine causes a drug catalyzed worsening with a very high frequency of about 50%.²¹ The 3.6% rate of worsening we saw with TM represents a vast improvement over the 50% worsening we found with penicillamine. At about 6 months after therapy initiation the neurologic and psychiatric symptoms begin to improve, and improvement may continue for another 18 months.⁴⁸ Usually after two years residual symptoms are permanent.

Since trientine was already on the market, and was an unknown as far as initial therapy of neurologically presenting patients, we next carried out a double blind comparison of TM and trientine on these patients.²³ A standard dose of 120 mg of TM (again equally divided in between meal and with meal doses) was used in one arm, and 1000 mg of trientine given as 250 mg four times/day, away from food, was given in the second arm. Both drugs were given for 8 weeks, and in both arms, 50 mg of zinc twice daily was also given.

One of 25 patients (4%), receiving TM reached the criteria for neurologic deterioration, while 6 out of 23 patients (26%) receiving trientine deteriorated, a significant difference (p = 0.05).²³ Five of the trientine treated patients who deteriorated in the hospital had a spike of free copper associated in time with the neurologic worsening.⁵⁶ Additionally, the patients who deteriorated did not do well, with death in three out of the six and little recovery in two others.²³ This high rate of deterioration of trientine treated patients not only indicates this drug is contraindicated for this type of patient, but sets a lower limit for the deterioration rate for penicillamine. The 50% deterioration rate is a softer number, coming from a retrospective survey, but since the two drugs act in a similar manner, and trientine is gentler than penicillamine, the deterioration rate for penicillamine is certainly 26% or higher.

We have also conducted a third study of TM.⁵⁴ Since the two adverse events, anemia/leukopenia and transaminase elevations each occur with a frequency of 10–15%, neither occurs during the first weeks of therapy, and both respond to halving the dose, we have evaluated a new dose regimen. In a double bind comparison, patients, in one arm presenting neurologically received the standard 120 mg daily dose of TM for 8 weeks, and patients in the other arm received a loading dose of 120 mg of TM per day for two weeks, then a half (60 mg) daily dose of TM for 14 more weeks. Patients in both arms received 50 mg of zinc twice daily. With 41 patients admitted, we showed a statistically significant reduction in the two side effects with the new regimen.⁵⁴

3. Penicillamine and trientine

Patients with Wilson’s disease can be treated with the chelators, penicillamine or trientine. These are effective maintenance therapies, the drawbacks being the long list of side effects with penicillamine, some of which develop quite late after years of therapy, and the somewhat shorter list of side effects with trientine. We recommend trientine as second choice to zinc in the maintenance phase and various other phases of Wilson’s disease (see Table 1). The initial treatment of the liver presentation can also be carried out with one of these drugs. In fact, our current recommendation for treating the liver failure presentation, assuming the failure isn’t so severe as to mandate liver transplantation, is a combination of trientine and zinc (Table 1).⁵⁷

Both of these chelators are contraindicated for the treatment of the initial neurologic presentation of Wilson’s disease, in our opinion. Our survey data indicate a 50% rate of worsening of neurologic status in these patients with penicillamine²¹ and our double blind study indicates a 26% rate of worsening with trientine.²³ Many of the patients who worsen don’t do well, never recover, and are left with severe lifelong disability and often an early death.

Thus, an important future development is the approval of TM for neurologically presenting patients. Hopefully this can be accomplished in the near future.

IV. The potential efficacy of anticopper therapy in a wide array of diseases: animal model studies

It should be understood that the efficacy described in this section is due to lowering copper levels. Thus, tetrathiomolybdate, which has been used to lower copper levels in these studies, does not have other known efficacy beyond lowering copper levels.

1. Antiangiogenic, anticancer therapy

Lowering copper availability inhibits angiogenesis, probably because a number of proangiogenic factors are copper dependent. Since growth of solid tumors requires angiogenesis, and since normal adults don’t require angiogenesis, tumor growth can be inhibited by lowering copper levels. Using TM to lower copper availability, a series of cancers in animal models have been inhibited.^58–63

2. Antifibrotic therapy

The pathway of fibrosis involved in normal organ development and tissue repair, involves the transforming growth factor beta (TGF_β) pathway. This pathway becomes excessively activated in diseases of fibrosis, such as cirrhotic diseases, and is inhibited by a lowering of copper availability. Fibrosis in the bleomycin mouse model of pulmonary fibrosis is almost completely inhibited by TM therapy.^64,65 Animal model studies of TM in carbon tetrachloride cirrhosis⁶⁶ and in bile duct ligation liver fibrosis⁶⁷ were also both strongly positive. The carbon tetrachloride model was also used to produce fibrosis, and then TM therapy used to see if TM could enhance fibrosis dissolution.⁶⁸ This study was also strongly positive.

3. Antiinflammatory and anti-autoimmune therapeutic effects

In the face of lowered copper availability, TNFα and interleukin one beta (IL-1_β), levels are strongly inhibited. Both are major inflammatory producing cytokines. To test the antiinflammatory effects of TM therapy, animal model studies of acetaminophen induced hepatitis⁶⁹ and doxorubicin induced cardiac damage⁷⁰ were done. TM strongly inhibited the damage produced by both these agents.

Since autoimmune disease produces damage though inflammatory mechanisms, the autoimmune effects of TM therapy were studied in a series of animal models. TM strongly inhibited the immune modulated arthritis produced by bovine collagen II injection,⁷¹ the hepatitis produced by concanavalin A injection⁶⁶ and the neurologic disease and spinal cord lesions produced in a multiple sclerosis model.⁷² TM also delayed the onset of diabetes in non-obese diabetic (NOD) mice, a model of human type I diabetes.⁷³

V. Clinical trials of TM in cancer and fibrotic diseases

The positive animal model studies in cancer have led to a series of clinical trials in advanced human cancers, some of which have shown some lengthening of freedom from progression.^{49–51,53,74} Possibly the most likely area of clinical efficacy suggested by animal model work, inhibition of micrometastatic disease, hasn’t really been tested. The concept of TM inhibition of small tumor disease fits with the most positive of the clinical trials, in mesothelioma.⁵³ In this disease, the surgeon removes all visible tumor, leaving only thin remnants of tumor tissue, coming closer to micrometastatic disease. The animal model studies all suggest this is the most optimal setting for TM therapy.

The positive results in the bleomycin mouse study of pulmonary fibrosis have led to a small open label clinical trial in idiopathic pulmonary fibrosis (IPF)⁷⁵ since this mouse model is thought to be a good model for IPF. The clinical trial results were encouraging.

The positive animal model studies in cirrhosis and in the antiinflammatory and anti-autoimmune effects of TM led to a small double blind clinical trial of TM in primary biliary cirrhosis (PBC), an autoimmune disease attacking the bile ducts. This study, which averaged about 13 months of therapy in 13 TM patients vs. 15 placebo patients, reached its primary efficacy endpoints in that two transaminase enzymes and tumor necrosis factor alpha (TNFα) levels were significantly reduced in TM patients.⁷⁶ This positive study in PBC is very exciting and demands follow-up in a longer and larger study.

The only significant drug attributable side effect in the clinical IPF, PBC, and cancer studies has been bone marrow copper depletion, leading to anemia and/or leukopenia, easily corrected by a drug holiday or dose reduction. Of course, more marked lowering of copper availability leading to clinical copper deficiency can produce other and severe side effects. Thus, it is important to monitor ceruloplasmin levels and lower copper availability to a mild extent.

At this point it appears to us that copper lowering therapy with TM deserves further evaluation in cancer as well as autoimmune diseases such as PBC, rheumatoid arthritis, and multiple sclerosis where we have positive animal model work, as well as some of the other large number of autoimmune diseases in which we haven’t studied specific animal models. Wherever inflammation is a key component of the disease process, TM therapy may be helpful. In that sense, it is like steroids. Beyond this, fibrotic disease such as the various types of cirrhosis should be considered for trials, since TM not only protects against cirrhosis,^66,67 but enhances dissolution of fibrosis in an animal model.⁶⁸

References

1. G. J. Brewer, Wilson’s Disease: A Clinician’s Guide to Recognition, Diagnosis, and Management, Kluwer Academic Publishers, Boston, MA, 2001.
2. G. J. Brewer, Wilson’s Disease, in Harrison’s Principles of Internal Medicine, ed. A. S. Fauci, E. Braunward, D. L. Kasper, S. L. Hauser, D. L. Longo, J. L. Jameson and J. Loscalzo, McGraw-Hill Companies, Inc, New York, NY, 2008, pp. 2449–2452.
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4. G. J. Brewer and V. Yuzbasiyan-Gurkan, Wilson disease, Medicine, 1992, 71, 139–164.
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19. G. J. Brewer, V. Yuzbasiyan-Gurkan, R. Dick, Y. Wang and V. Johnson, Does a vegetarian diet control Wilson’s disease?, J. Am. Coll. Nutr., 1993, 12, 527–530.
20. J. M. Walshe, Penicillamine, a new oral therapy for Wilson’s disease, Am. J. Med., 1956, 21, 487–495.
21. G. J. Brewer, C. A. Terry, A. M. Aisen and G. M. Hill, Worsening of neurologic syndrome in patients with Wilson’s disease with initial penicillamine therapy, Arch. Neurol., 1987, 44, 490–493.
22. J. M. Walshe, Treatment of Wilson’s disease with trientine (triethylene tetramine) dihydrochloride, Lancet, 1982, 1, 643–647.
23. G. J. Brewer, F. Askari, M. T. Lorincz, M. Carlson, M. Schilsky, K. J. Kluin, P. Hedera, P. Moretti, J. K. Fink, R. Tankanow, R. B. Dick and J. Sitterly, Treatment of Wilson disease with ammonium tetrathiomolybdate: IV. Comparison of tetrathiomolybdate and trientine in a double-blind study of treatment of the neurologic presentation of Wilson disease, Arch. Neurol., 2006, 63, 521–527.
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27. G. J. Brewer, E. B. Schoomaker, D. A. Leichtman, W. C. Kruckleberg, L. F. Brewer and N. Myers, The Uses of Pharmacologic Doses of Zinc in the Treatment of Sickle Cell Anemia, in Zinc Metabolism: Current Aspects in Health and Disease, ed. G. J. Brewer and A. S. Prasad, Allan R. Liss. Inc., New York, 1977, pp. 241–258.
28. G. M. Hill, G. J. Brewer, A. S. Prasad, C. R. Hydrick and D. E. Hartmann, Treatment of Wilson’s disease with zinc. I. Oral zinc therapy regimens, Hepatology, 1987, 7, 522–528.
29. G. M. Hill, G. J. Brewer, J. E. Juni, A. S. Prasad and R. D. Dick, Treatment of Wilson’s disease with zinc. II. Validation of oral 64copper with copper balance, Am. J. Med. Sci., 1986, 292, 344–349.
30. G. J. Brewer, G. M. Hill, R. D. Dick, T. T. Nostrant, J. S. Sams, J. J. Wells and A. S. Prasad, Treatment of Wilson’s disease with zinc: III. Prevention of reaccumulation of hepatic copper, J. Lab. Clin. Med., 1987, 109, 526–531.
31. G. J. Brewer, G. Hill, A. Prasad and R. Dick, The treatment of Wilson’s disease with zinc. IV. Efficacy monitoring using urine and plasma copper, Proc. Soc. Exp. Biol. Med., 1987, 184, 446–455.
32. V. Yuzbasiyan-Gurkan, G. J. Brewer, G. D. Abrams, B. Main and D. Giacherio, Treatment of Wilson’s disease with zinc. V. Changes in serum levels of lipase, amylase, and alkaline phosphatase in patients with Wilson’s disease, J. Lab. Clin. Med., 1989, 114, 520–526.
33. G. J. Brewer, V. Yuzbasiyan-Gurkan, D. Y. Lee and H. Appelman, Treatment of Wilson’s disease with zinc. VI. Initial treatment studies, J. Lab. Clin. Med., 1989, 114, 633–638.
34. D. Y. Lee, G. J. Brewer and Y. X. Wang, Treatment of Wilson’s disease with zinc. VII. Protection of the liver from copper toxicity by zinc-induced metallothionein in a rat model, J. Lab. Clin. Med., 1989, 114, 639–645.
35. G. J. Brewer, V. Yuzbasiyan-Gurkan and R. Dick, Zinc therapy of Wilson’s disease: VIII. Dose response studies, J. Trace Elem. Exp. Med., 1990, 3, 227–234.
36. G. J. Brewer, V. Yuzbasiyan-Gurkan and V. Johnson, Treatment of Wilson’s disease with zinc. IX: Response of serum lipids, J. Lab. Clin. Med., 1991, 118, 466–470.
37. V. Yuzbasiyan-Gurkan, A. Grider, T. Nostrant, R. J. Cousins and G. J. Brewer, Treatment of Wilson’s disease with zinc: X. Intestinal metallothionein induction, J. Lab. Clin. Med., 1992, 120, 380–386.
38. G. J. Brewer, V. Yuzbasiyan-Gurkan, V. Johnson, R. D. Dick and Y. Wang, Treatment of Wilson’s disease with zinc: XI. Interaction with other anticopper agents, J. Am. Coll. Nutr., 1993, 12, 26–30.
39. G. J. Brewer, V. Yuzbasiyan-Gurkan, V. Johnson, R. D. Dick and Y. Wang, Treatment of Wilson’s disease with zinc XII: Dose regimen requirements, Am. J. Med. Sci., 1993, 305, 199–202.
40. G. J. Brewer, R. D. Dick, V. Yuzbasiyan-Gurkan, V. Johnson and Y. Wang, Treatment of Wilson’s disease with zinc. XIII: Therapy with zinc in presymptomatic patients from the time of diagnosis, J. Lab. Clin. Med., 1994, 123, 849–858.
41. G. J. Brewer, V. Johnson and J. Kaplan, Treatment of Wilson’s disease with zinc: XIV. Studies of the effect of zinc on lymphocyte function, J. Lab. Clin. Med., 1997, 129, 649–652.
42. G. J. Brewer, R. D. Dick, V. D. Johnson, J. A. Brunberg, K. J. Kluin and J. K. Fink, Treatment of Wilson’s disease with zinc: XV. long-term follow-up studies, J. Lab. Clin. Med., 1998, 132, 264–278.
43. G. J. Brewer, V. D. Johnson, R. D. Dick, J. K. Fink, K. J. Kluin and P. Hedera, Treatment of Wilson’s disease with zinc: XVII. Treatment during pregnancy, Hepatology, 2000, 31, 364–370.
44. G. J. Brewer, R. D. Dick, V. D. Johnson, J. K. Fink, K. J. Kluin and S. Daniels, Treatment of Wilson’s disease with zinc: XVI. Treatment during the pediatric years, J. Lab. Clin. Med., 2001, 137, 191–198.
45. G. J. Brewer, R. D. Dick, V. Yuzbasiyan-Gurkan, R. Tankanow, A. B. Young and K. J. Kluin, Initial therapy of patients with Wilson’s disease with tetrathiomolybdate, Arch. Neurol., 1991, 48, 42–47.
46. G. J. Brewer, R. D. Dick, V. Johnson, Y. Wang, V. Yuzbasiyan-Gurkan, K. Kluin, J. K. Fink and A. Aisen, Treatment of Wilson’s disease with ammonium tetrathiomolybdate. I. Initial therapy in 17 neurologically affected patients, Arch. Neurol., 1994, 51, 545–554.
47. G. J. Brewer, V. Johnson, R. D. Dick, K. J. Kluin, J. K. Fink and J. A. Brunberg, Treatment of Wilson disease with ammonium tetrathiomolybdate. II. Initial therapy in 33 neurologically affected patients and follow-up with zinc therapy, Arch. Neurol., 1996, 53, 1017–1025.
48. G. J. Brewer, P. Hedera, K. J. Kluin, M. Carlson, F. Askari, R. B. Dick, J. Sitterly and J. K. Fink, Treatment of Wilson disease with ammonium tetrathiomolybdate: III. Initial therapy in a total of 55 neurologically affected patients and follow-up with zinc therapy, Arch. Neurol., 2003, 60, 379–385.
49. E. M. Gartner, K. A. Griffith, Q. Pan, G. J. Brewer, G. F. Henja, S. D. Merajver and M. M. Zalupski, A pilot trial of the anti-angiogenic copper lowering agent tetrathiomolybdate in combination with irinotecan, 5-flurouracil, and leucovorin for metastatic colorectal cancer, Invest. New Drugs, 2008, Aug 20 (epub ahead of print).
50. N. L. Henry, R. Dunn, S. Merjaver, P. Pan, K. J. Pienta, G. J. Brewer and D. C. Smith, Phase II trial of copper depletion with tetrathiomolybdate as an antiangiogenesis strategy in patients with hormone refractory prostate cancer, Oncology, 2006, 71, 168–175.
51. B. G. Redman, P. Esper, Q. Pan, R. L. Dunn, H. K. Hussain, T. Chenevert, G. J. Brewer and S. D. Merajver, Phase II trial of tetrathiomolybdate in patients with advanced kidney cancer, Clin. Cancer Res., 2003, 9, 1666–1672.
52. A. K. Vine and G. J. Brewer, Tetrathiomolybdate as an antiangiogenesis therapy for subfoveal choroidal neovascularization secondary to age-related macular degeneration, Trans. Am. Ophthalmol. Soc., 2002, 100, 73–76.
53. H. I. Pass, G. J. Brewer, R. Dick, M. Carbone and S. Merajver, A phase II trial of tetrathiomolybdate after surgery for malignant mesothelioma: final results, Ann. Thorac. Surg., 2008, 86, 383–389.
54. G. J. Brewer, F. Askari, M. T. Lorincz, M. Carlson, K. J. Kluin, J. K. Fink, R. B. Dick and J. Sitterly, Treatment of Wilson’s Disease with Ammonium Tetrathiomolybdate: VI. New Dosage Regimen to Reduce Side Effects, unpublished work.
55. M. Marcellini, V. Di Ciommo, F. Callea, R. Devito, D. Comparcola, M. R. Sartorelli, G. Carelli and V. Nobili, Treatment of Wilson’s disease with zinc from the time of diagnosis in pediatric patients: a single-hospital, 10-year follow-up study, J. Lab. Clin. Med., 2005, 145, 139–143.
56. G. J. Brewer, F. Askari, R. Dick, J. A. Sitterly, J. K. Fink, M. Carlson, K. J. Kluin and M. T. Lorincz, The treatment of Wilson’s disease with tetrathiomolybdate (TM): V. Control of free copper by TM and a comparison with trientine, Transl. Res. , Submitted.
57. F. K. Askari, J. Greenson, R. D. Dick, V. D. Johnson and G. J. Brewer, Treatment of Wilson’s disease with zinc. XVIII. Initial treatment of the hepatic decompensation presentation with trientine and zinc, J. Lab. Clin. Med., 2003, 142, 385–390.
58. C. D. Cox, T. N. Teknos, M. Barrios, G. J. Brewer, R. D. Dick and S. D. Merajver, The role of copper suppression as an antiangiogenic strategy in head and neck squamous cell carcinoma, Laryngoscope, 2001, 111, 696–701.
59. C. Cox, S. D. Merajver, S. Yoo, R. D. Dick, G. J. Brewer, J. S. Lee and T. N. Teknos, Inhibition of the growth of squamous cell carcinoma by tetrathiomolybdate-induced copper suppression in a murine model, Arch. Otolaryngol. Head Neck Surg., 2003, 129, 781–785.
60. M. K. Khan, M. W. Miller, J. Taylor, N. K. Gill, R. D. Dick, K. Van Golen, G. J. Brewer and S. D. Merajver, Radiotherapy and antiangiogenic TM in lung cancer, Neoplasia, 2002, 4, 164–170.
61. Q. Pan, C. G. Kleer, K. L. van Golen, J. Irani, K. M. Bottema, C. Bias, M. De Carvalho, E. A. Mesri, D. M. Robins, R. D. Dick, G. J. Brewer and S. D. Merajver, Copper deficiency induced by tetrathiomolybdate suppresses tumor growth and angiogenesis, Cancer Res., 2002, 62, 4854–4859.
62. Q. Pan, L. W. Bao, C. G. Kleer, G. J. Brewer and S. D. Merajver, Antiangiogenic tetrathiomolybdate enhances the efficacy of doxorubicin against breast carcinoma, Mol. Cancer Ther., 2003, 2, 617–622.
63. K. L. van Golen, L. Bao, G. J. Brewer, K. J. Pienta, J. M. Kamradt, D. L. Livant and S. D. Merajver, Suppression of tumor recurrence and metastasis by a combination of the PHSCN sequence and the antiangiogenic compound tetrathiomolybdate in prostate carcinoma, Neoplasia, 2002, 4, 373–379.
64. G. J. Brewer, M. R. Ullenbruch, R. B. Dick, L. Olivarez and S. H. Phan, Tetrathiomolybdate therapy protects against bleomycin-induced pulmonary fibrosis in mice, J. Lab. Clin. Med., 2003, 141, 210–216.
65. G. J. Brewer, R. Dick, M. R. Ullenbruch, H. Jin and S. H. Phan, Inhibition of key cytokines by tetrathiomolybdate in the bleomycin model of pulmonary fibrosis, J. Inorg. Biochem., 2004, 98, 2160–2167.
66. F. K. Askari, R. B. Dick, M. Mao and G. J. Brewer, Tetrathiomolybdate therapy protects against concanavalin A and carbon tetrachloride hepatic damage in mice, Exp. Biol. Med., 2004, 229, 857–863.
67. M. Song, Z. Song, S. Barve, J. Zhang, T. Chen, T. Liu, G. E. Arteel, G. J. Brewer and C. J. McClain, Tetrathiomolybdate protects against bile duct ligation-induced cholestatic liver injury and fibrosis, J. Pharmacol. Exp. Ther., 2008, 325, 409–416.
68. G. Hou, R. Dick and G. J. Brewer, Improvement in dissolution of liver fibrosis in an animal model by tetrathiomolybdate, Exp. Biol. Med. , In press.
69. S. Ma, G. Hou, R. D. Dick and G. J. Brewer, Tetrathiomolybdate protects against liver injury from acetaminophen in mice, J. Appl. Res. Clin. Exp. Ther., 2004, 4, 419–426.
70. G. Hou, R. Dick, G. D. Abrams and G. J. Brewer, Tetrathiomolybdate protects against cardiac damage by doxorubicin in mice, J. Lab. Clin. Med., 2005, 146, 299–303.
71. M. D. McCubbin, G. Hou, G. D. Abrams, R. Dick, Z. Zhang and G. J. Brewer, Tetrathiomolybdate is effective in a mouse model of arthritis, J. Rheumatol., 2006, 33, 2501–2506.
72. G. Hou, G. Abrams, R. Dick and G. J. Brewer, Efficacy of tetrathiomolybdate in a mouse model of multiple sclerosis, Transl. Res., 2008, 52, 239–244.
73. G. J. Brewer, R. Dick, C. Zeng and G. Hou, The use of tetrathiomolybdate in treating fibrotic, inflammatory, and autoimmune diseases, including the non-obese diabetic mouse model, J. Inorg. Biochem., 2006, 100, 927–930.
74. G. J. Brewer, R. D. Dick, D. K. Grover, V. LeClaire, M. Tseng, M. Wicha, K. Pienta, B. G. Redman, J. Thierry, V. K. Sondak, M. Strawderman, G. LeCarpentier and S. D. Merajver, Treatment of metastatic cancer with tetrathiomolybdate, an anticopper, antiangiogenic agent: Phase I study, Clin. Cancer Res., 2000, 6, 1–10.
75. K. R. Flaherty, D. A. Arenberg, E. S. White, V. Thannickal, A. Andrei, S. Murray, T. V. Colby, W. D. Travis, E. A. Kazerooni, B. H. Gross, R. Paine, G. B. Toews, G. J. Brewer and F. J. Martinez, Treatment of Idiopathic Pulmonary Fibrosis with Tetrathiomolybdate, unpublished work.
76. F. Askari, D. Innis, R. Dick, G. Hou, J. Marrero, J. Greenson and G. J. Brewer, Treatment of primary biliary cirrhosis with tetrathiomolybdate: Results of a double blind trial, Transl. Res. , Submitted.

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