Dicyanogold (I) is a common human metabolite of different gold drugs.

Gold based drugs and their metabolites have been characterized using reversed phase, ion pairing chromatography with an inductively coupled plasma mass spectrometer as an element specific detector. For a patient receiving gold sodium thiomalate the principal gold species in the urine is [Au(CN)2]-, which is also seen in a low molecular weight infiltrate of the blood. The same compound is also identified in the urine and blood of a patient taking auranofin and in patients taking solganol. This represents the first identification of a specific gold metabolite in biological fluids taken from patients undergoing gold therapy and the first evidence that different gold drugs have common metabolites.

Gold concentrations in blood fractions of patients with rheumatoid arthritis treated with Myocrisin.

Gold levels in the plasma and blood cells of patients treated with the gold drug Myocrisin (sodium aurothiomalate) were determined by atomic absorption spectrometry. There is a correlation between whole blood gold and plasma gold concentrations which is different for smokers and non-smokers. Most cellular gold is associated with the membrane and is present in concentrations approximately equivalent to the number of reactive sulphydryl groups on the exofacial surface of the cell. Since gold would be expected to react with SH groups and since these groups are vital for cellular function, a possible role for gold in modifying cellular metabolism is indicated.

Action of gold sodium thiomalate on experimental thrombosis in vivo.

In order to study the effect of gold compounds on the action of thrombin in vivo, experiments were performed to measure platelet survival and the weight of thrombus formation in experimental models of intra-aortic thrombosis by two indwelling aortic catheter methods. We have called these the long and short catheter methods. Platelet survival was reduced in all gold-treated and control animals which had indwelling aortic catheters. In the long catheter model, New Zealand White male rabbits were treated with one of the following: gold sodium thiomalate, sterile water, gold thioglucose, gold sodium thiosulfate, disodium thiomalate. Gold sodium thiomalate-treated rabbits had a reduced weight of experimentally induced intra-aortic thrombi compared with animals treated with sterile water or equimolar concentrations of gold thioglucose, gold sodium thiosulfate, or disodium thiomalate. This reduction in thrombus weight in the animals treated with gold sodium thiomalate was not reflected by changes in platelet survival or fibrinolysis. The serum gold levels achieved in these in vivo experiments was in the range of 5.0 X 10(-5) to 1.0 X 10(-4) M. These values are comparable to levels which can be achieved in human subjects immediately after a gold injection. In the short catheter model, New Zealand White male rabbits were treated with either gold sodium thiomalate, gold thioglucose, disodium thiomalate, or auranofin. Controls were given either water or 0.05% chlorocresol. Water-treated and gold sodium thiomalate-treated animals were also given 51Cr-labeled platelets and 125I-fibrinogen before insertion of the catheter.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of sodium aurothiomalate during lactation.

The report concerns a mother who breast fed her infant whilst receiving sodium aurothiomalate for the treatment of rheumatoid arthritis. The milk:serum concentration ratio was not constant, reflecting the non-concurrence of the concentration-time profiles of gold in milk and maternal serum after i.m. injection. Gold was detected in the infant's serum. Calculations indicate that the weight-adjusted dose to the infant exceeded that received by the mother.

Binding of sodium aurothiomalate to human serum albumin in vitro at physiological conditions.

The binding of aurothiomalate to human serum albumin was studied by equilibrium dialysis at 37 degrees C, pH 7.3-7.4, and ionic strength 0.15-0.16 mol/l. It was found that aurothiomalate was bound to albumin at one site with an apparent association constant K1 = 3.0 X 10(4) M-1 and at three or more sites with the sum of association constants of the order of 10(3) M-1. Valuable information of the aurothiomalate-albumin interaction was deduced from the observed changes of pH of the albumin solutions during dialysis. A conceivable binding mechanism consistent with the results might be that aurothiomalate binds as Au+ to the high affinity binding site by exchanging a H+ and that this site might be the sulphydryl group in cysteine34; and that aurothiomalate binds as monomeric anions to the lower affinity binding sites.

The effect of cyanide on the uptake of gold by red blood cells.

Cyanide markedly increased the rate of uptake of gold by red blood cells when incubated with sodium aurothiomalate, a polymeric gold complex. Thiocyanate had no significant effect on gold uptake. The effect of cyanide was demonstrated to be due to the conversion of aurothiomalate to the complexion, aurocyanide, which is rapidly taken up by red blood cells. At a low ratio (1:20) of cyanide to aurothiomalate, cyanide appeared to act as a shuttle to carry gold into red blood cells. Tobacco smoking is known to increase the concentrations of gold in red blood cells in patients treated with aurothiomalate. The present data indicate that this effect of smoking is most likely due to cyanide inhaled in tobacco smoke and not to thiocyanate, a circulating metabolite of cyanide. An effect of cyanide on the uptake of polymeric gold complexes to target cells such as polymorphonuclear leukocytes and monocytes is suggested.

Comparative pharmacokinetics of triethylphosphine gold (auranofin) and gold sodium thiomalate (GST).

The pharmacokinetics of gold sodium thiomalate (GST) and triethylphosphine gold (auranofin; AF) are different. Gold sodium thiomalate (GST) is completely bioavailable while only 15-25% of auranofin (AF) is absorbed. Protein binding of AF occurs to a larger extent to macroglobulins than does GST and total body retention of GST is much greater than AF at six months (30% versus approximately 1%). While terminal serum half-lives are approximately equal, total body half-lives are 250 days for GST and 69 days for AF. In addition, excretory pathways contrast markedly, with 85% of AF appearing in the feces while only 30% of GST is excreted by this route; 15% of AF gold appears in the urine and approximately 70% of GST gold is excreted via this route. With all the above differences one would expect that organ and cellular distribution of these compounds would differ. While gold from both drugs is concentrated in kidney, the percent of the dose found in the kidneys is less for AF than GST, at least in animals (0.4% vs 4.8%). Minute quantities are found in other organs but more study is needed to more clearly define organ distribution of these gold compounds, particularly in man.

Role of metallothionein in cellular uptake and disposition of gold sodium thiomalate.

Rat liver and kidney tissue uptake of gold and its localization in the cytosol was studied following various doses of gold sodium thiomalate (GST). The timecourse of gold incorporation into intracellular gold-binding ligands following repeated injections of GST was also investigated (11 injections, one dose/week). Results show that between 30 and 60% of the hepatic and renal gold was localized in the cytosol over a wide range of GST doses. This was also true following repeated doses. In the kidney, the binding of gold to high molecular weight (HMW) proteins was saturated after the third GST dose, while incorporation into the metallothioneins (MT) continued to increase, accounting for as much as 50% of cytosolic gold. On the other hand the binding to hepatic MT was about 10x lower, and the proportion of cytosolic gold incorporated into the MT, decreased from 30% (after first 3 GST injections) to about 15% (following the last 3 injections). The results show that the stimulation of MT biosynthesis in different tissues as a response to the injected GST is not the same and varies within each organ with the dose and/or the duration of repeated exposure. In the liver, the ability of gold to induce MT synthesis was limited and the importance of MT in the cellular uptake and disposition of gold may largely be confined to the kidneys. It is suggested that besides playing a possible role in the detoxification of cellular gold, particularly in the kidney, MT may also contribute towards the retention and localization of gold in the tissues.

[Intracellular gold content of circulating blood cells using various gold compounds]. / Intrazellulärer Goldgehalt in zirkulierenden Blutzellen unter unterschiedlichen Goldverbindungen.

Evidence on the action mechanisms of gold salts in the treatment of rheumatoid arthritis is still inconclusive. The intracellular localization of the place of action is likely. Therefore not only the serum gold levels but also the intracellular concentration of gold are of special interest. We measured the gold concentration in the serum and in the blood cells after in vitro application of aurothiomalate (Tauredon), gold keratinate (Auro-Detoxin) and triethylphosphine-gold (Ridaura) and in blood samples of patients undergoing these gold salts treatments. Cell-bound concentrations were found to vary extensively as a function of the gold compound used. While no or very little gold was present intracellularly after administration of the 2 parenteral drugs, up to 40% of the circulating gold was found to bind to the cells after administration of the triethylphosphine compound for gastro-intestinal absorption. The red cell concentration was more or less the same as that in the extracellular compartment. Gold apparently accumulated in the white cells, because the cell-bound concentration relative to unit volume was up to 20 times higher than the plasma level. The method used did not offer any information on the actual binding site of gold in white cells, i.e. cytoplasm versus nucleus versus cell membrane.

I. Unbound serum gold: procedure for quantitation.

The unbound fraction of many drugs appears to be the therapeutically active component. However, the major problem encountered in following unbound serum gold (UBSG) concentration during chrysotherapy has been the ability to quantitate such a small quantity of gold reliably without matrix interference. The methodology detailed here overcomes these difficulties and provides an effective means of monitoring the UBSG fraction during chrysotherapy. We have observed that the unbound fraction of gold dissipates quickly after gold sodium thiomalate administration and constitutes less than 2% of the total serum gold concentration.

II. Unbound versus total serum gold concentration: pharmacological actions on cellular function.

Unbound serum gold (UBSG) has received little attention, possibly because of rapid in vivo decay and in vivo concentration below the range of existing analytical procedures. We have recently developed a methodology enabling quantitation and study of UBSG during chrysotherapy to assess effects on cellular functions. UBSG after gold administration is labile, declining rapidly after attaining peak values at which lymphocyte mitogen response and polymorphonuclear phagocytosis were observed to be suppressed. Oral gold, i.e., auranofin, 3 mg BID as compared to systemic chrysotherapy 50 mg/wk, resulted in a higher percentage of UBSG to total serum gold.

Inhibition of lymphocyte activation by gold sodium thiomalate.

Activation of lymphoid cells by both T and B cell mitogens was inhibited by gold sodium thiomalate (GST). The action of GST did not appear to be exerted at early stages of lymphocyte activation. Inhibition by GST was sustained throughout 4 days of culture. The inhibitory effect of GST was reduced at low serum concentrations. Sodium thiomalate and sodium chloroaurate were also able to inhibit lymphocyte activation.

Comparison of the kinetics of parenteral and oral gold.

The intramuscular (gold sodium thiomalate and aurothioglucose) and the orally (auranofin) administered gold compounds exhibit contrasting patterns of absorption, excretion and body tissue and fluid levels. The parenteral compounds are fully absorbed after injection but negligibly absorbed orally. Approximately 25% of the gold in auranofin is orally absorbed. Serum gold levels peak several hours after injection during conventional weekly treatment, attaining concentrations of 600-800 micrograms/dl, and then decline gradually, reaching 300-350 micrograms/dl before the next injection. Whole blood gold levels with auranofin vary from 10 to 90 micrograms/dl with doses of 1-9 mg/day. Blood gold levels plateau after 6-8 weeks with the injectable compounds and after 12 weeks with oral gold, reflecting the shorter blood half-life of gold sodium thiomalate (5.5 days) than of auranofin (17-26 days). A larger fraction of gold is within or attached to circulating blood cells, especially erythrocytes, with auranofin than with injectable gold. Fourty percent of the administered dose is excreted during injectable chrysotherapy, and 75-100% is recovered in excreta with auranofin. Parenteral gold is excreted primarily in urine (70%) while auranofin gold is recovered primarily in faeces (95%). Approximately 43% of intravenous radiolabelled gold sodium thiomalate is retained in the body at 60 days and 30% at 180 days; only 15% of radiolabelled auranofin remains at 10 days and less than 1% at 180 days. During injectable therapy, the total body burden of gold rises steadily; preliminary studies suggest minimal tissue accumulation with auranofin.

Assessment of immune response during chrysotherapy. Comparison of gold sodium thiomalate vs. auranofin.

Auranofin (AF) differs significantly from gold sodium thiomalate (GST) in formulation, i.e., aurous gold is stabilized by dual sulfur and phosphorus ligands, has hydrophobic rather than hydrophilic characteristics, and lacks ionic charge. These attributes facilitate: oral absorption of AF, plasma membrane penetration, increase in intracellular lymphocyte gold concentration and perhaps thereby influence lymphocyte function. AF therapy was observed to affect primarily T rather than B lymphocyte function in 16 RA subjects receiving 6 mg of AF per day for an average of 45 weeks (range 20-74 weeks) compared with GST-treated RA subjects. Lymphocytes from AF-treated subjects manifested prompt and sharp declines in mitogen-induced lymphoproliferative response (LPR); suppressed response to skin testing with dinitrochlorobenzene (DNCB); and blebbing of lymphocyte membranes as shown by scanning electron microscopy. Suppression of LPR with AF was approximately 60% after the first week and 80% after 20 weeks of therapy, contrasting with 0% and 30% for the respective intervals in GST-treated subjects. DNCB skin testing of AF patients, indicated 11 of 14, failed to respond, whereas all GST patients responded. Local or systemic fungal, bacterial and/or opportunistic infections were not encountered. The effect of AF on B cell effector function, e.g., suppression of immunoglobulins and rheumatoid factor titer, was less marked when contrasted with GST therapy in RA subjects, as previously reported.

Fate of the gold and the thiomalate part after intramuscular administration of aurothiomalate to mice.

Double isotope-labelled aurothiomalate (195Au-14C-thiomalate) has been administered to mice, and the excretory fate and tissue distribution have been studied. The results show that the gold and the thiomalate separate in vivo resulting in protein-bound gold and release of free thiomalate. About half of this thiol is excreted in the urine during the first day, and the remaining half is bound to tissue membranes and cells. Although thiomalate penetrates cellular membranes slowly in vitro. the compound is found in all organs, mostly in the liver and the kidneys, after administration of aurothiomalate. Separation of the gold moiety from its thiol carrier also takes place in man. This explains the finding of free thiomalate in the urine of patients receiving aurothiomalate intramuscularly. As thiomalate has now been shown to possess penicillamine-like biological activities it is suggested that at least part of the antirheumatic effects of aurothiomalate may be due to the thiol carrier being released in the body.

Remission-inducing drugs in rheumatoid arthritis.

The administration of certain drugs to patients with established rheumatoid arthritis frequently results in improvement that is slow to appear but persists for long periods, even after the drug is discontinued. The three main drugs with this effect, whose efficacy and toxicity are reviewed in this paper, are gold salts, D-penicillamine and chloroquine. The cytotoxic agents used to treat rheumatoid arthritis, which likely have nonspecific anti-inflammatory actions and have serious long-term side effects, are also briefly reviewed. A new drug, levamisole, is currently being tested in patients with rheumatoid arthritis. It is suggested that the time for considering the introduction of a remission-inducing drug in patients with progressive rheumatoid arthritis is after an adequate trial of therapy with salicylates or other nonsteroidal anti-inflammatory agents, or both, and before the oral administration of steroids. It is difficult, however, on the basis of rigorous clinical comparisons, to recommend which of the three main remission-inducing drugs should be tried first, although gold salts have been used the most. Patients who have improved with 6 months of chrysotherapy may continue treatment for at least 3 years, during which time the frequency of mucocutaneous and renal toxic effects will steadily decrease. Some aspects of the medical economics of therapy with remission-inducing drugs for rheumatoid arthritis are discussed.

Distribution of gold among plasma fractions in rheumatoid patients undergoing chrysotherapy compared with its distribution in plasma incubated with aurothiomalate in vitro.

The distribution of gold among the globulin, albumin, and unbound fractions of plasma, obtained either from rheumatoid patients receiving long-term aurothiomalate therapy or from samples incubated with aurothiomalate in vitro, has been investigated. In the rheumatoid patients it has been found that, although the majority of the plasma gold is always bound to albumin, the distribution varies cyclically in phase with the dose schedule. An explanation of these phenomena is provided, based on data obtained from the reaction between aurothiomalate and plasma constituents in vitro.

Quantitation of gold lymphocyte binding during chrysotherapy.

Carbon rod atomic absorption analysis (CRA) was applied to the quantiation of gold lymphocyte content (GLC) during chrysotherapy. Sensitivity and accuracy of CRA compared favorably with 195Au isotopic scintillation counting, circumventing the limitations and hazards of the latter in clinical applications. Picogram gold quantification of limited sample volume, less than 10 ml blood, e.g., 10(4)-10(5) lymphocytes (5 microliters) containing 5-10 pg was achieved. GLC after IM administration increased significantly in 60% of patients; for the remainder, GLC was observed to be independent of plasma gold content or cumulative dosage. GLC during auranofin administration (6 mg/day p.o.) approached values for IM gold despite significantly lower plasma levels. Unique sensitivity of CRA enables analysis of GLC under therapeutic conditions that could elucidate whether gold alters functional determinants.