Toremifene Sawai

First line hormone treatment of hormone-dependent metastatic breast cancer in postmenopausal patients.

Toremifene Sawai is not recommended for patients with estrogen receptor negative tumours.

Posology

The recommended dose is 60 mg daily.

Renal impairment

Hepatic impairment

Pediatric population

There is no relevant use of Toremifene Sawai in the paediatric population.

Method of administration

Toremifene is administered orally. Toremifene can be taken with or without food.

- Pre-existing endometrial hyperplasia and severe hepatic failure are contra-indications in long-term use of toremifene.

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- Both in preclinical investigations and in humans, changes in cardiac electrophysiology have been observed following exposure to toremifene, in the form of QT prolongation. For reasons of drug safety, toremifene is therefore contraindicated in patients with:

- Congenital or documented acquired QT prolongation

- Electrolyte disturbances, particularly in uncorrected hypokalaemia

- Clinically relevant bradycardia

- Clinically relevant heart failure with reduced left-ventricular ejection fraction

- Previous history of symptomatic arrhythmias.

).

Gynaecological examination should be performed before treatment administration, closely looking at pre-existing endometrial abnormality.).

Anemia, leukopenia and thrombocytopenia have been reported.).

Toremifene Sawai has been shown to prolong the QTc interval on the electrocardiogram in some patients in a dose-related manner.).

If signs or symptoms that may be associated with cardiac arrhythmia occur during treatment with Toremifene Sawai, treatment should be stopped and an ECG should be performed.

If the QTc interval is > 500 ms, Toremifene Sawai should not be used.

Patients with non-compensated cardiac insufficiency or severe angina pectoris should be closely monitored.

Hypercalcemia may occur at the beginning of toremifene treatment in patients with bone metastasis and thus these patients should be closely monitored.

There are no systematic data available from patients with labile diabetes, from patients with severely altered performance status or from patients with cardiac failure.

Toremifene Sawai tablets contain lactose (28.5 mg/tablet). Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Toremifene has no influence on the ability to drive and use machines.

The most frequent adverse reactions are hot flushes, sweating, uterine bleeding, leukorrhea, fatigue, nausea, rash, itching, dizziness and depression. The reactions are usually mild and mostly due to the hormonal action of toremifene.

The frequencies of the adverse reactions are classified as follows:

Very common (> 1/10)

Common (> 1/100 to <1/10)

Uncommon (> 1/1,000 to < 1/100)

Rare (> 1/10,000 to < 1/1,000)

Very rare (< 1/10,000), not known (cannot be estimated from the available data).

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Toremifene treatment has been associated with changes in liver enzyme levels (increases of transaminases) and in very rare occasions with more severe liver function abnormalities (jaundice).

A few cases of hypercalcaemia have been reported in patients with bone metastases at the beginning of toremifene treatment.

Endometrial hypertrophy may develop during the treatment due to the partial estrogenic effect of toremifene.).

Toremifene Sawai increases the QT interval in a dose-related manner (see also section 4.4).

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via:

Ireland

HPRA Pharmacovigilance, Earlsfort Terrace, IRL - Dublin 2; Tel: +353 1 6764971, Fax: +353 1 6762517. Website: www.hpra.ie e-mail: [email protected]

United Kingdom

Yellow Card Scheme

Website: www.mhra.gov.uk/yellowcard

Vertigo, headache and dizziness were observed in healthy volunteer studies at daily dose of 680 mg. The dose-related QTc interval prolongation potential of Toremifene Sawai should also be taken into account in cases of overdose. There is no specific antidote and the treatment is symptomatic.

Pharmacotherapeutic group: Anti-estrogens, ATC code: L02BA02

Toremifene is a nonsteroidal triphenylethylene derivative. As other members of this class, e.g. tamoxifen and clomifene, toremifene binds to estrogen receptors and may produce estrogenic, anti-estrogenic or both effects, depending upon the duration of treatment, animal species, gender, target organ and variable selected. In general, however, nonsteroidal triphenylethylene derivatives are predominantly anti-estrogenic in rats and man and estrogenic in mice.

In post-menopausal breast cancer patients, toremifene treatment is associated with modest reductions in both total serum cholesterol and low density lipoprotein (LDL).

Toremifene binds specifically to estrogen receptors, competitively with oestradiol, and inhibits estrogen-induced stimulation of DNA synthesis and cell replication. In some experimental cancers and/or using high-dose, toremifene displays anti-tumour effects which are not estrogen-dependent.

The anti-tumour effect of toremifene in breast cancer is mainly due to the anti-estrogenic effect, although other mechanisms (changes in oncogene expression, growth factor secretion, induction of apoptosis and influence on cell cycle kinetics) may also be involved in the anti-tumour effect.

Absorption

Distribution

The serum concentration curve can be described by a biexponential equation. The half-life of the first (distribution) phase is 4 (range 2 - 12) hours, and of the second (elimination) phase 5 (range 2 - 10) days. The basal disposition parameters (CL and V) could not be estimated due to the lack of intravenous study. Toremifene binds extensively (> 99.5%) to serum proteins, mainly to albumin. Toremifene obeys linear serum kinetics at oral daily doses between 11 and 680 mg. The mean concentration of toremifene at steady-state is 0.9 (range 0.6 - 1.3) µg/ml at the recommended dose of 60 mg per day.

Biotransformation

Toremifene is extensively metabolised. In human serum the main metabolite is N-demethyltoremifene with mean half-life of 11 (range 4 - 20) days. Its steady-state concentrations are about twice compared to those of the parent compound. It has similar anti-estrogenic, albeit weaker anti-tumour activity than the parent compound.

It is bound to plasma proteins even more extensively than toremifene, the protein bound fraction being > 99.9%. Three minor metabolites have been detected in human serum: (deaminohydroxy)toremifene, 4-hydroxytoremifene, and N,N-didemethyltoremifene. Although they have theoretically interesting hormonal effects, their concentrations during toremifene treatment are too low to have any major biological importance.

Elimination

Toremifene is eliminated mainly as metabolites to the faeces. Enterohepatic circulation can be expected. About 10% of the administered dose is eliminated via urine as metabolites. Owing to the slow elimination, steady-state concentrations in serum are reached in 4 to 6 weeks.

Characteristics in patients

Clinical anti-tumour efficacy and serum concentrations have no positive correlation at the recommended daily dose of 60 mg.

No information is available concerning polymorphic metabolism. Enzyme complex, known to be responsible for the metabolism of toremifene in humans, is cytochrome P450-dependent hepatic mixed function oxidase. The main metabolic pathway, N-demethylation, is mediated mainly by CYP3A.

Pharmacokinetics of toremifene were investigated in an open study with four parallel groups of ten subjects: normal subjects, patients with impaired (mean AST 57 U/L - mean ALT 76 U/L - mean gamma GT 329 U/L) or activated liver function (mean AST 25 U/L - mean ALT 30 U/L - mean gamma GT 91 U/L - patients treated with antiepileptics) and patients with impaired renal function (creatinine: 176 µmol/L). In this study the kinetics of toremifene in patients with impaired renal function were not significantly altered as compared to normal subjects. The elimination of toremifene and its metabolites was significantly increased in patients with activated liver function and decreased in patients with impaired liver function.

The acute toxicity of toremifene is low with LD-50 in rats and mice of more than 2000 mg/kg. In repeated toxicity studies the cause of death in rats is gastric dilatation. In the acute and chronic toxicity studies most of the findings are related to the hormonal effects of toremifene. The other findings are not toxicologically significant. Toremifene has not shown any genotoxicity and has not been found to be carcinogenic in rats. In mice, estrogens induce ovarian and testicular tumours as well as hyperostosis and osteosarcomas. Toremifene has a species-specific estrogen-like effect in mice and causes similar tumours. These findings are postulated to be of little relevance for the safety in man, where toremifene acts mainly as an anti-estrogen.

Non clinical in vitro and in vivo studies have evidenced the potential of toremifene and its metabolite to prolong cardiac repolarisation and this can be attributed to the blockade of hERG channels.

In vivo, high plasma concentrations in monkeys caused a 24% prolongation in QTc, which is in line with QTc findings in humans.

It is also to be noted that the C_max observed in the monkeys (1800 ng/ml) is two-fold compared to the mean C_max observed in humans at a daily dose of 60 mg.

Action potential studies in isolated rabbit heart have shown that toremifene induce cardiac electrophysiological changes which start to develop at concentrations approximately 10 fold compared to the calculated free therapeutic plasma concentration in human.

Not applicable.

No special requirements.