[Intestinal absorption and urinary excretion of triethylenetetramine for Wilson's disease in rat]

Triethylenetetramine (TETA)

The WEEL for triethylenetetramine (TETA; CAS No. 112-24-3) was originally established in 1991 and updated in 1998 and 2009. Recent literature searches to identify new toxicity information were performed in 2016 and January 2021. No new studies or data relevant to the WEEL were identified. TETA is used in manufacturing; the hydrochloride salt of TETA is used as a copper-chelating drug in the treatment of Wilson's disease. TETA is severely irritating to the skin and eyes and produces skin sensitization; however, it is of low to moderate acute toxicity via the oral and dermal routes of exposure. In subchronic studies, signs of toxicity included multi-organ effects (lung, liver, and spleen) in mice, but not rats. TETA was genotoxic/mutagenic in short-term in vitro assays but not in in vivo assays. No data on reproductive toxicity were available. Embryo/fetal toxicity occurred at maternally toxic doses and was associated with copper deficiency. In humans, the use of TETA·2HCl for treatment of Wilson's disease during pregnancy resulted in no miscarriages or fetal abnormalities. No evidence of carcinogenicity was noted in a lifetime dermal study in mice. Based on a subchronic drinking water study in mice, 600 ppm (95 mg/kg-day) was determined to be the no-observed-adverse-effect level (NOAEL) and the point of departure (POD). This NOAEL was converted to an equivalent inhalation concentration by adjusting for respiratory rate, interindividual variability, and uncertainty. The resulting 8-h time-weighted average WEEL value of 1 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to airborne TETA.

Active uptake of hydrophilic copper complex Cu(ii)-TETA in primary cultures of neonatal rat cardiomyocytes

Myocardial ischemia leads to copper efflux from the heart. The ischemic tissue with a low copper content fails to take up copper from the circulation even under the conditions of serum copper elevation. Cardiac copper repletion thus requires other available forms of this element than those currently known to bind to copper transport proteins. The copper complex of triethylenetetramine (TETA) is a metabolite of TETA, which has the potential to increase cardiac copper content in vivo. In the present study, we synthesized Cu(ii)-TETA, analyzed its crystal structure, and demonstrated the role of this compound in facilitating copper accumulation in primary cultures of neonatal rat cardiomyocytes. The Cu(ii)-TETA compound formed a square pyramidal chloride salt [Cu(TETA)Cl]Cl structure, which dissociates from chloride in aqueous solution to yield the four-coordinate dication Cu(ii)-TETA. Cu(ii)-TETA was accumulated as an intact compound in cardiomyocytes. Analysis from time-dependent copper accumulation in cardiomyocytes defined a different dynamic process in copper uptake between Cu(ii)-TETA and CuCl2 exposure. An additive copper accumulation in cardiomyocytes was found when the cells were exposed to both CuCl2 and Cu(ii)-TETA. Gene silencing of copper transport 1 (CTR1) did not affect cross-membrane transportation of Cu(ii)-TETA, but inhibited copper cellular accumulation from CuCl2. Furthermore, the uptake of Cu(ii)-TETA by cardiomyocytes was ATP-dependent. It is thus concluded that the formation of Cu(ii)-TETA facilitates copper accumulation in cardiomyocytes through an active CTR1-independent transportation process.

The steady state pharmacokinetics of trientine in Wilson disease patients

PURPOSE

To determine the steady state pharmacokinetics of trientine in children (≥ 12 years of age) and adult patients who had been receiving trientine dihydrochloride therapy prior to the study.

METHODS

Twenty patients were exposed to trientine (trientine dihydrochloride capsules supplied by Univar) after standard oral dosing as part of ongoing therapy. Plasma trientine concentration was determined pre-dose and at 30 min, 1, 1.5, 2, 3, 4, 5, 6, 8, and 12 h post-dose. Concentrations of trientine in plasma were determined by LC-MS/MS using a validated bioanalytical method with stable labelled trientine as the internal standard.

RESULTS

Trientine was generally absorbed fairly rapidly with a median T_max of 1.49 h (range, 0.48-4.08 h). There was some variability in exposure, with a 10-fold range in C_max, and a 13.8-fold range in AUC0-t. This variability was slightly lower when PK parameters were dose-normalised (6.7-fold range in C_max/D and an 11.6-fold range in AUC0-t/D). The terminal half-life, which could be defined in 14 of the 20 patients, was broadly consistent between patients (range of 2.33 to 6.99 h). There was no marked difference in pharmacokinetics between adult patients (n = 16) and children (n = 4). The C_max range was 506 to 3100 ng/mL in adults and 309 to 1940 ng/mL in children-the equivalent ranges for AUC0-t were 1240 to 17,100 ng/mL h and 1500 to 8060 ng/mL h. When PK parameters were normalised for administered dose, the C_max/D and AUC0-t/D for children were contained within the ranges for the adult patients.

CONCLUSIONS

The steady state pharmacokinetics of trientine in Wilson disease patients were broadly similar to that reported in healthy subjects.

Triethylenetetramine pharmacology and its clinical applications

Triethylenetetramine (TETA), a Cu(II)-selective chelator, is commonly used for the treatment of Wilson's disease. Recently, it has been shown that TETA can be used in the treatment of cancer because it possesses telomerase inhibiting and anti-angiogenesis properties. Although TETA has been used in the treatment of Wilson's disease for decades, a comprehensive review on TETA pharmacology does not exist. TETA is poorly absorbed with a bioavailability of 8 to 30%. It is widely distributed in tissues with relatively high concentrations measured in liver, heart, and kidney. It is mainly metabolized via acetylation, and two major acetylated metabolites exist in human serum and urine. It is mainly excreted in urine as the unchanged parent drug and two acetylated metabolites. It has a relatively short half-life (2 to 4 hours) in humans. The most recent discoveries in TETA pharmacology show that the major pharmacokinetic parameters are not associated with the acetylation phenotype of N-acetyltransferase 2, the traditionally regarded drug acetylation enzyme, and the TETA-metabolizing enzyme is actually spermidine/spermine acetyltransferase. This review also covers the current preclinical and clinical application of TETA. A much needed overview and up-to-date information on TETA pharmacology is provided for clinicians or cancer researchers who intend to embark on cancer clinical trials using TETA or its close structural analogs.

Pharmacokinetics, pharmacodynamics, and metabolism of triethylenetetramine in healthy human participants: an open-label trial

The selective Cu(II)-chelator, triethylenetetramine (TETA), is undergoing clinical trials for the treatment of heart failure in patients with diabetes. Recently, the authors showed that 2 acetylated metabolites, N(1)-acetyltriethylenetetramine (MAT) and N(1),N(10)-diacetyltriethylenetetramine (DAT), are formed in humans following oral TETA administration. Thus, it became necessary to determine whether the N-acetyltransferase (NAT) 2 phenotype has any effects on the pharmacological properties and safety profile of TETA. Twelve fast and 12 slow NAT2-phenotype healthy participants were recruited. After oral drug administration, the authors collected plasma and urine samples, measured plasma concentrations of TETA and its 2 metabolites along with concomitant urinary copper concentrations, and performed safety tests. They present, for the first time, the complete 24-hour pharmacokinetic profiles of TETA, MAT, and DAT in humans. There was no evidence for clear-cut differences in pharmacokinetic profiles between fast and slow acetylators. Pharmacodynamic analysis showed no significant differences in cupruresis between the 2 NAT2 phenotypes. Safety results were consistent with TETA being well tolerated, and no significant differences in safety profiles were observed between the 2 phenotypes. Based on these data, NAT2 phenotype does not affect TETA's pharmacokinetic, pharmacodynamic, or safety profiles. TETA may be acetylated via an alternative mechanism, such as that catalyzed by spermidine/spermine N(1)-acetyltranferase.

Determination of triethylenetetramine (TETA) and its metabolites in human plasma and urine by liquid chromatography–mass spectrometry (LC–MS)

A liquid chromatography-mass spectrometry (LC-MS) method has been developed to measure triethylenetetramine (TETA) and its metabolites in human samples. We identified two metabolites of TETA, N1-acetyltriethylenetetramine (MAT) and N1,N10-diacetyltriethylenetetramine (DAT), the latter being novel. We further developed this LC-MS method for the measurement of TETA and these metabolites in human plasma and urine in a single injection. Separation of analytes was achieved on a cyano column using 15% acetonitrile, 85% water (18 M Omega), and 0.1% heptafluorobutyric acid as the mobile phase. Simultaneous MS detection was performed at [M+H]+ values of 147, 189, 231 and 245, corresponding to TETA, MAT, DAT, and N1-acetylspermine as the internal standard, respectively. This method was successfully applied to measure TETA, MAT and DAT in plasma and urine of humans receiving oral drug treatment.

Triethylenetetramine and Metabolites: Levels in Relation to Copper and Zinc Excretion in Urine of Healthy Volunteers and Type 2 Diabetic Patients

Triethylenetetramine (TETA), a selective Cu(II)-chelator used in the treatment of Wilson's disease, is now undergoing clinical trials for the treatment of heart failure in diabetes. Despite decades of clinical use, knowledge of its pharmacology in human subjects remains incomplete. Here, we first used liquid chromatography-mass spectrometry (LC-MS) to detect and identify major metabolites of TETA in human plasma and urine, and then used this method to measure concentrations of TETA and its metabolites in the urine of healthy and diabetic subjects who were administered increasing doses (300, 600, 1200, and 2400 mg) of TETA orally. Twenty-four-hour urine collections were performed before and after dosing participants. Two major metabolites of TETA were detected in human urine, N(1)-acetyltriethylenetetramine (MAT) and N(1),N(10)-diacetyltriethylenetetramine, the latter being novel. Both metabolites were verified with synthetic standards by LC-MS. The proportion of unchanged TETA excreted as a fraction of total urinary drug-derived molecules was significantly higher in healthy than in matched diabetic subjects, consistent with a higher rate of TETA metabolism in the latter. TETA-evoked increases in urinary Cu excretion in nondiabetic subjects were more closely correlated with parent drug concentrations than in diabetic subjects, whereas, by contrast, urinary Cu was more closely associated with the sum of TETA and MAT. These findings are consistent with the hypothesis that MAT could play a significant role in the molecular mechanism by which TETA extracts Cu(II) from the systemic compartment in diabetic subjects.

Liquid chromatographic determination of triethylenetetramine in human and rabbit sera based on intramolecular excimer-forming fluorescence derivatization

A highly selective and simple fluorimetric liquid chromatographic method for the determination of triethylenetetramine (TETA), a therapeutic drug for Wilson's disease, in human and rabbit sera is described. This method is based on intramolecular excimer-forming fluorescence derivatization, which allows spectrofluorometric discrimination of polyamino compounds from monoamino species, followed by liquid chromatography. TETA and 1,6-hexanediamine (internal standard) were converted to the corresponding excimer-forming derivatives with a pyrene reagent, 4-(1-pyrene)butyric acid N-hydroxysuccinimide ester. The derivatives were separated within 20 min on a reversed-phase column using isocratic elution and detected spectofluorometrically at 480 nm with excitation at 345 nm. This method was successfully applied to the monitoring of TETA in human and rabbit sera with a simple pretreatment. The detection limit for TETA in serum was 18 ng/ml (0.13 nmol/ml) corresponding to 0.2 pmol on column at a signal-to-noise ratio of 3.

Comparison of disposition behavior and de-coppering effect of triethylenetetramine in animal model for Wilson's disease (Long-Evans Cinnamon rat) with normal Wistar rat

The disposition behaviors and de-coppering effect of triethylenetetramine dihydrochloride (trientine), a selective chelating agent for copper and an 'orphan drug' for Wilson's disease, have been evaluated in an animal model, Long-Evans Cinnamon (LEC) rats, and normal rats (Wistar). In LEC rats, urinary excretion of trientine was remarkably lower than that of Wistar rats. The absorption rates from the jejunal loop and in vitro metabolism in the liver S9 fraction (supernatant of 9000 x g) were approximately the same for both strains. The decline of urinary excretion of trientine in LEC rats is thought to be due mainly to the lowering of the functional activity of the kidney, because urinary excretion of creatinine and phenolsulfonphthalein were significantly lower in LEC rats than those in Wistar rats. Both acceleration of urinary excretion of copper and reduction of hepatic copper levels were observed with treatment of trientine in LEC rats aged 6 weeks. In LEC rats aged 13 weeks, however, no de-coppering effect from the liver was observed, though urinary excretion of copper was increased. These results suggest that trientine has a pharmacological effect in disease state, especially in the early stages of hepatitis.