ER; selective estrogen receptor modulator (SERM)

Regardless of the expression levels of activating ERα mutations, lasoxifene (1 nM-1 μM; 48 hours) exhibits antagonist activity in ER+ breast cancer cells in comparison to wild-type (WT) ERα [2].

Lasoxifene (4 mg/mouse; subcutaneous injection; 5 days/week; for 43 days) by reducing cartilage oligomeric matrix protein (COMP), a serum marker of cartilage destruction, and lowering serum IL-6, an inflammatory Cytokines) levels, reducing the severity of arthritis in mice [1]. Lasoxifene (4 mg/mouse; subcutaneous injection; 5 days/week; for 43 d) prevents systemic bone loss in CIA by increasing trabecular bone mineral density (BMD) and cortical thickness in mice [1] . Lasoxifene (5 and 10 mg/kg; subcutaneous injection; 5 days/week; for 70 days) inhibits primary tumor growth and reduces lung and liver metastasis in mice [3].

Lasofoxifene, a SERM originally developed for the treatment/prevention of osteoporosis, was the only compound found to be as potent an antagonist when evaluated in cells expressing ERY537S or ERD538G when compared to ERWT (Fig. 2I). This latter observation is in agreement with the findings of a recent study from our group showing that lasofoxifene was as effective an inhibitor of ERmuts as ERWT in cellular models of gynecological cancers. These findings have important clinical implications that could inform the optimal selection of ER antagonists for the treatment of patients with ERmuts in advanced disease[2].
Considering the pharmacology noted in SKBR3 cells, we selected fulvestrant (potency shift observed with both mutants), AZD9496 (loss of efficacy as an inhibitor of ERY537S) and lasofoxifene (potency and efficacy unaffected by mutation status) for analysis in these model systems. The transcriptional activity and pharmacology of receptor combinations were assessed using a transfected ERE-luciferase reporter gene[2].

Animal/Disease Models: OVX (ovariectomized) DBA/1 mouse postmenopausal RA model (female DBA/1 mice, 8-10 weeks old, CIA treated) [1]
Doses: 4 mg/mouse/day
Route of Administration: subcutaneous injection; 5 days per week from first signs of arthritis (Day 18); 43 days
Experimental Results: Reduction in arthritis severity, including reduction in synovial inflammation and joint destruction. At 42 days post-immunization, the average incidence of arthritis was 47% compared with 81% in the vehicle group.

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Animal/Disease Models: NSG Mouse xenograft tumor model (MIND, mammary intraductal): WT, Y537S and D538G ERα renders tumors [3]
Doses: 1, 5 or 10 mg/kg
Route of Administration: SC; 5 days per week ; 70-day
Experimental Results: Excellent inhibitory effect at 10 mg/kg, resulting in potential tumor shrinkage of Y537S and D538G tumors. At doses of 5 mg/kg and 10 mg/kg, tumor weight was diminished to 60% and 50% for Y537S and D538G, respectively.

Absorption, Distribution and Excretion
Peak plasma concentration (Cmax) is reached at approximately 6.0 to 7.3 hours. Compared to other selective estrogen receptor modulators (SERMs), it exhibits higher oral bioavailability due to its nonpolar tetrahydronaphthalene structure, which enhances resistance to intestinal glucuronidation. In a comparative study in rats, lasoxifene's bioavailability was 62%. It is primarily excreted in feces, followed by renal clearance as metabolites, with less than 2% of the drug excreted unchanged in the urine. The apparent volume of distribution in postmenopausal women is 1350 L. The apparent oral clearance (CL/F) in postmenopausal women is approximately 6.6 L/h. Metabolism/Metabolites Phase I oxidative metabolism of lasoxifene primarily occurs via hepatic CYP3A4/CYP3A5 and CYP2D6, accounting for approximately half of total metabolism. Phase II binding reactions involve glucuronidation and sulfation. Glucuronidation is catalyzed by UGT expressed in the liver (UGT1A1, UGT1A3, UGT1A6, and UGT1A9) and intestine (UGT1A8 and UGT1A10). Other metabolites of lasoxifene detected in plasma include glucuronide of the hydroxylated metabolite and methylated catechol. Known human metabolites of lasoxifene include (2S,3S,4S,5R)-3,4,5-trihydroxy-6-[[(5R,6S)-6-phenyl-5-[4-(2-pyrrolidine-1-ylethoxy)phenyl]-5,6,7,8-tetrahydronaphth-2-yl]oxy]oxacyclohexane-2-carboxylic acid. The elimination half-life is approximately 6 days.

Protein Binding

Lasofoxifene has a high binding rate to plasma proteins (>99%), primarily binding to albumin and α1-acid glycoprotein.

[1]. Selective oestrogen receptor modulators lasofoxifene and bazedoxifene inhibit joint inflammation and osteoporosis in ovariectomised mice with collagen-induced arthritis. Rheumatology (Oxford). 2016 Mar;55(3):553-63.

[2]. The Dysregulated Pharmacology of Clinically Relevant ESR1 Mutants is Normalized by Ligand-activated WT Receptor. Mol Cancer Ther. 2020 Jul. 19(7):1395-1405.

[3]. Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer. Breast Cancer Res. 2021 May 12. 23(1):54.

Lasofoxifene belongs to the tetrahydronaphthyl group of compounds, with the structure 5,6,7,8-tetrahydronaphth-2-ol, wherein the hydrogen atoms at positions 5 and 6 are substituted with 4-[2-(pyrrolidone-1-yl)ethoxy]phenyl and phenyl, respectively (5R,6S-stereoisomers). It is a selective estrogen receptor modulator (SERM) suitable for the prevention and treatment of osteoporosis in postmenopausal women. It also possesses antitumor, cardioprotective, estrogen receptor agonist, estrogen receptor antagonist, and bone mineral density maintenance effects. Lasofoxifene belongs to the tetrahydronaphthyl group, aromatic ether group, naphthol group, and N-alkylpyrrolidine group of compounds. Lasofoxifene is a nonsteroidal third-generation selective estrogen receptor modulator (SERM) that binds selectively to ERα and ERβ with high affinity. It is a naphthalene derivative used for the prevention and treatment of osteoporosis and vaginal atrophy. Initially, Pfizer developed the drug under the brand name Oporia for the treatment of postmenopausal osteoporosis and vaginal atrophy, but neither was approved by the U.S. Food and Drug Administration (FDA). Later, Pfizer collaborated with Ligand Pharmaceuticals to develop Fablyn and submitted a New Drug Application (NDA) in 2008. This drug received approval from the European Commission in March 2009. Ligand Pharmaceuticals entered into a licensing agreement with Sermonix Pharmaceuticals to develop and market oral lasoxifene in the United States. Lasoxifen is a nonsteroidal naphthalene derivative, belonging to the third-generation selective estrogen receptor modulators (SERMs), and possesses potential antitumor and anti-osteoporosis activities. After oral administration, lasoxifene selectively binds with high affinity to estrogen receptor α (ERα; ESR1) and estrogen receptor β (ERβ; ESR2), mimicking the effects of endogenous estradiol in ER-expressing tissues, exhibiting both agonist and antagonist effects. Lasofoxifene's blockade of ERα may inhibit the proliferation of estrogen-dependent cancer cells in cancers expressing ER. Lasofoxifene may also bind to certain ERα mutants, including the Y537S ESR1 mutant, making it potentially useful in treating tumors resistant to other ER-targeting drugs.
See also: Lasofoxifene tartrate (note moved to).

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Drug Indications
It has been studied for the treatment of postmenopausal osteoporosis to reduce the risk of vertebral and non-vertebral fractures, and for the treatment of other postmenopausal conditions, including reducing the risk of breast cancer and treating vulvovaginal atrophy (VVA).
Fablyn is indicated for the treatment of osteoporosis in postmenopausal women with an increased risk of fracture. It has been shown to significantly reduce the incidence of vertebral and non-vertebral fractures, but has no significant effect on the incidence of hip fractures (see Section 5.1). When choosing fabulin or other therapies (including estrogen) for postmenopausal women, menopausal symptoms, effects on uterine and breast tissue, and cardiovascular risks and benefits should be considered (see Section 5.1).

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Mechanism of Action
Lasofoxifene acts as an agonist on estrogen receptors expressed in bone, mimicking the positive effects of estrogen by altering the NF-κB ligand (RANKL)/RANK/osteoplastin system, stimulating osteoblast (bone morphogen) activity, and other effects on calcium homeostasis, thereby reducing osteoclast production and lifespan. It acts as an antagonist in the uterus and breast by inhibiting estrogen signaling in oncogenic pathways and suppressing downstream gene transcription. One study also suggested that larosoxifene may act as a reverse agonist of the CB2 cannabinoid receptor, which is expressed in bone, and inhibits osteoclast formation and bone resorption activity.

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Pharmacodynamics
Lasofoxifene exhibits significant estrogenic and anti-estrogenic activity both in vitro and in vivo, targeting any tissue containing estrogen receptors (ER), such as bone, uterus, breast, blood vessels, and liver. Conjugation assays show that this compound has high affinity for both ERα and ERβ, and this affinity is tissue-dependent. It mimics the action of estradiol, exhibiting both agonist and antagonist effects.

413.55

413.235

C, 81.32; H, 7.56; N, 3.39; O, 7.74

180916-16-9

Lasofoxifene tartrate;190791-29-8

216416

White to off-white solid powder

1.15g/cm3

572.4ºC at 760mmHg

300ºC

1.05E-13mmHg at 25°C

1.613

5.666

1

3

6

31

533

2

C1=CC=C(C=C1)[C@H]2CCC3=CC(=CC=C3[C@H]2C4=CC=C(C=C4)OCCN5CCCC5)O

GXESHMAMLJKROZ-IAPPQJPRSA-N

InChI=1S/C28H31NO2/c30-24-11-15-27-23(20-24)10-14-26(21-6-2-1-3-7-21)28(27)22-8-12-25(13-9-22)31-19-18-29-16-4-5-17-29/h1-3,6-9,11-13,15,20,26,28,30H,4-5,10,14,16-19H2/t26-,28+/m1/s1

(5R,6S)-6-phenyl-5-[4-(2-pyrrolidin-1-ylethoxy)phenyl]-5,6,7,8-tetrahydronaphthalen-2-ol

CP 336156; CP 336,156; Lasofoxifene; CP336,156; CP336156; CP-336156; CP-33,6156; rac-Lasofoxifene; Oporia; 180915-78-0; CP 336156; (5R,6S)-6-phenyl-5-[4-(2-pyrrolidin-1-ylethoxy)phenyl]-5,6,7,8-tetrahydronaphthalen-2-ol; trade name Fably; Oporia;

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.)