The primary target of Toremifene is the estrogen receptor (ER). It acts as a selective estrogen receptor modulator (SERM), binding to estrogen receptors and exerting tissue-specific effects. In breast tissue, it acts primarily as an antagonist, inhibiting estrogen-driven proliferation of hormone receptor-positive cancer cells. It is an estrogen agonist for bone tissue and cholesterol metabolism but is antagonistic on mammary and uterine tissue. Toremifene may also inhibit tumor growth through other mechanisms, such as induction of apoptosis, regulation of oncogene expression, and growth factors.

Toremifene is a selective estrogen receptor modulator (SERM) of the second generation being developed to stop osteoporosis and other side effects of ADT-induced prostate cancer [1]. The proliferation of Ac-1 cells is inhibited in vitro by tamoxifen, toremifene, and atamestane, with IC50 values of 1.8±1.3μM, 1±0.3μM, and 60.4±17.2μM, respectively. The combination of toremifene and atamestane is more effective than either drug alone, according to in vitro research [3].
In vitro, Toremifene (7.5 mM) causes about 60% of cells to exhibit typical morphological features of programmed cell death or apoptosis in human breast cancer cells. It inhibits the growth of estrogen-sensitive breast cancer cells by inducing apoptosis in some cells and inhibiting others from entering mitosis. Toremifene competes with estradiol for the estrogen receptor and has growth-inhibitory effects on MCF-7 breast cancer cells. It has been shown to have antiproliferative activity in various cancer cell lines.

After that, the impact of this combination was investigated in vivo utilizing Ac-1 xenografts developed in female SCID mice with ovariectomies. Toremifene (1000 μg/day), atamestane (1000 μg/day), tamoxifen (100 μg/day), or a combination of toremifene and atamestane were injected into mice. The findings of this investigation indicate that toremifene plus atamestane is as effective as either drug alone, although it might not be any more so than either drug alone. There are no further benefits associated with tamoxifen usage [3].
In vivo, Toremifene is clinically approved for the treatment and prevention of estrogen receptor-positive metastatic breast cancer in postmenopausal women. It is also in development for the prevention of osteoporosis and other adverse effects resulting from androgen deprivation therapy (ADT) in men with prostate cancer. The compound is a first-generation nonsteroidal selective estrogen receptor modulator.

In vitro enzyme or receptor binding assays for Toremifene involve studying its binding affinity for the estrogen receptor. Radioligand binding assays are performed using estrogen receptor protein or cell lysates expressing the receptor. The compound is incubated with a radiolabeled ligand, such as [3H]estradiol, and the displacement of the ligand is measured to determine the affinity. Selectivity is assessed by testing the compound against other steroid receptors.

In vitro cell-based assays for Toremifene are performed using estrogen-responsive breast cancer cell lines such as MCF-7 and T47D. Cells are treated with the compound, and cell proliferation is measured using standard assays such as MTT or CCK-8. Apoptosis is detected by measuring caspase activation or using Annexin V/PI staining. The compound's effects on estrogen-responsive gene expression are assessed by qPCR.

In vivo animal experiments for Toremifene are conducted using rodent models of breast cancer and osteoporosis. The compound is administered orally or subcutaneously, and its effects on tumor growth, bone density, and uterine weight are assessed. The compound's tissue-specific effects as a SERM are evaluated by comparing its actions in different tissues.

Absorption, Distribution and Excretion
Absorbed well Toremifene is primarily metabolized via CYP3A4 to N-desmethyltoremifene, which also has anti-estrogenic activity, but weaker antitumor activity in vivo. 580 L 5 L/h Metabolism/Metabolites Hepatic metabolism. Primarily metabolized via CYP3A4 to N-desmethyltoremifene, which has anti-estrogenic activity, but weaker antitumor activity in vivo. Known human metabolites of toremifene include N-desmethyltoremifene. Biological half-life 5 days
Pharmacokinetic (PK) properties of Toremifene indicate that it is orally active. The compound has a molecular weight of 405.96 and a molecular formula of C26H28ClNO. It has a purity of ≥98%. The compound is metabolized in the liver, primarily by CYP3A4. Its half-life is approximately 5-7 days. Toremifene is highly protein-bound (approximately 99%). Storage at -20°C is recommended.

Hepatotoxicity
Toremifene is associated with mild to moderate elevations in serum ALT or AST in 5% to 19% of patients, but these abnormalities are usually transient and without symptoms or jaundice. Elevations in ALT or AST exceeding 5 times the upper limit of normal are uncommon (Probability score: D (likely to cause clinically significant liver damage)). Protein Binding Toremifene is primarily bound to albumin in serum (92%), 2% to α1-acid glycoprotein, and 6% to β1-globulin.
Toxicology (toxicology) data for Toremifene indicate that it is generally well-tolerated. Common side effects include hot flashes, nausea, vomiting, and vaginal discharge. As a SERM, it may increase the risk of endometrial cancer and thromboembolic events, similar to tamoxifen. The compound should be used with caution in patients with a history of thromboembolic disorders or endometrial hyperplasia.

[1]. Matthew R Smith, Selective Estrogen Receptor Modulators to Prevent Treatment-Related Osteoporosis.Rev Urol. 2005; 7(Suppl 3): S30-S35.

[2]. Screening and Reverse-Engineering of Estrogen Receptor Ligands as Potent Pan-Filovirus Inhibitors. J Med Chem. 2020 Sep 4.

[3]. Gauri J Sabnis, Luciana Macedo, Olga Goloubeva, Toremifene - Atamestane; Alone or In Combination: Predictions from the Preclinical Intratumoral Aromatase Model. J Steroid Biochem Mol Biol. 2008 January; 108(1-2): 1-7.

[4]. Taneja SS, Morton R, Barnette G, Prostate cancer diagnosis among men with isolated high-grade intraepithelial neoplasia enrolled onto a 3-year prospective phase III clinical trial of oral toremifene. J Clin Oncol. 2013 Feb 10;31(5):523-9.

Toremifene is a tertiary amine, organochlorine compound, and aromatic ether. It possesses antitumor, estrogen antagonist, estrogen receptor modulator, and bone mineral density protectant effects. It is derived from stilbene hydrides. Toremifene is a selective estrogen receptor modulator (SERM) and nonsteroidal anti-estrogen used to treat estrogen receptor-positive breast cancer. Like tamoxifen, toremifene belongs to the first-generation triphenylene derivative SERM class. Toremifene has tissue-specific effects: it has estrogenic (agonist) activity on the cardiovascular system and bone tissue, a weak estrogenic effect on uterine tissue, but also anti-estrogenic (estrogen antagonist) activity on breast tissue. Toremifene is an estrogen agonist/antagonist. Its mechanism of action is as a selective estrogen receptor modulator. Toremifene is a nonsteroidal anti-estrogen used to treat estrogen receptor-positive breast cancer. Long-term use of toremifene is associated with fatty liver, steatohepatitis, cirrhosis, and rare, clinically significant acute liver injury.
Toremifene is a nonsteroidal triphenylene antiestrogen. Chemically related to tamoxifen, toremifene is a selective estrogen receptor modulator (SERM). This drug competitively binds to estrogen receptors, thereby interfering with estrogen activity. Toremifene also possesses intrinsic estrogenic properties, the expression of which varies depending on tissue type or species. (NCI04)
First-generation selective estrogen receptor modulator (SERM). Similar to tamoxifen, toremifene is an estrogen agonist that promotes bone and cholesterol metabolism, but has antagonistic effects on breast and uterine tissues.
See also: Toremifene citrate (in salt form).
Drug Indications
For the treatment of estrogen receptor-positive or receptor-unknown metastatic breast cancer in postmenopausal women. Toremifene is currently being investigated as a prostate cancer prevention drug in men with high-grade prostatic intraepithelial neoplasia and no evidence of prostate cancer.
For first-line hormone therapy in postmenopausal hormone-dependent metastatic breast cancer. Farestom is not recommended for patients with estrogen receptor-negative tumors. Mechanism of Action Toremifene is a nonsteroidal triphenylene derivative. Toremifene binds to estrogen receptors and may exert estrogen-like, anti-estrogen-like, or both activities, depending on the duration of treatment, animal species, sex, target organ, or selected endpoint. The antitumor effect of toremifene in breast cancer is thought to be primarily attributed to its anti-estrogenic effect; in other words, it competes with estrogen for binding sites in cancer cells, thereby blocking the estrogen-induced growth of tumors. Toremifene may also inhibit tumor growth through other mechanisms, such as inducing apoptosis, regulating oncogene expression, and growth factors. Pharmacodynamics Toremifene is an antitumor hormone primarily used to treat advanced breast cancer. Toremifene is a nonsteroidal drug that has shown potent anti-estrogenic properties in animal systems. Its anti-estrogenic effect may be related to its ability to compete with estrogen for binding sites in target tissues such as the breast. Toremifene inhibited the development of dimethylbenzanthracene (DMBA)-induced breast cancer in rats and induced the regression of existing DMBA-induced tumors. In this rat model, toremifene appears to exert its antitumor effect by binding to estrogen receptors. In the cytosol of human breast adenocarcinoma cells, toremifene competes with estradiol for estrogen receptor proteins.
Other information: Toremifene is marketed under the brand name Fareston. It is a chlorinated tamoxifen analog. The compound is a second-generation selective estrogen-receptor modulator (SERM). It is used for the treatment of estrogen receptor-positive metastatic breast cancer in postmenopausal women. Its CAS number is 89778-26-7.

C26H28CLNO

405.97

405.185

89778-26-7

Toremifene citrate;89778-27-8;Toremifene-d6;Toremifene-d6 hydrochloride

3005573

White to light yellow solid powder

1.1±0.1 g/cm3

535.1±50.0 °C at 760 mmHg

108-110°C

277.4±30.1 °C

0.0±1.4 mmHg at 25°C

1.588

7.82

0

2

9

29

483

0

CN(C)CCOC1=CC=C(C=C1)/C(=C(/CCCl)\C2=CC=CC=C2)/C3=CC=CC=C3

XFCLJVABOIYOMF-QPLCGJKRSA-N

InChI=1S/C26H28ClNO/c1-28(2)19-20-29-24-15-13-23(14-16-24)26(22-11-7-4-8-12-22)25(17-18-27)21-9-5-3-6-10-21/h3-16H,17-20H2,1-2H3/b26-25-

Ethanamine, 2-(4-((1Z)-4-chloro-1,2-diphenyl-1-butenyl)phenoxy)-N,N-dimethyl-

GTx 006 Z-Toremifene Acapodene Farestone

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)