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 concentrations (Cmax) were reached in about 6.0 to 7.3 hours. Displays higher oral bioavailability compared to other SERMs with increased resistance to intestinal glucuronidation due to nonpolar tetrahydronaphthalene structure. In a comparative study in the rat, lasofoxifene showed bioavailability of 62%.
Primarily fecal excretion and secondarily renal elimination as mainly metabolites, with less than 2% excreted in urine as unchanged parent drug.
The apparent volume of distribution in postmenopausal women is 1350L.
The apparent oral clearance (CL/F) of lasofoxifene in postmenopausal women is approximately 6.6 l/hr.

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Metabolism / Metabolites
Phase I oxidation via hepatic CYP3A4/CYP3A5 and CYP2D6 accounts for nearly half of total metabolism of lasofoxifene. Phase II conjugation reactions include glucuronidation and sulfation. Its glucuronidation is catalyzed by UGTs that are expressed in both the liver (UGT1A1, UGT1A3, UGT1A6, and UGT1A9) and the intestine (UGT1A8 and UGT1A10). Further metabolites of lasofoxifene detected in plasma are the glucuronide of a hydroxylated metabolite, and the methylated catechols.
Lasofoxifene has known human metabolites that include (2S,3S,4S,5R)-3,4,5-trihydroxy-6-[[(5R,6S)-6-phenyl-5-[4-(2-pyrrolidin-1-ylethoxy)phenyl]-5,6,7,8-tetrahydronaphthalen-2-yl]oxy]oxane-2-carboxylic acid.

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Biological Half-Life
Elimination half-life is approximately 6 days.

Protein Binding
Lasofoxifene is highly bound to plasma proteins (>99%) where it predominantly binds 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 is a member of the class of tetralins that is 5,6,7,8-tetrahydronaphthalen-2-ol in which the hydrogens at positions 5 and 6 are replaced by 4-[2-(pyrrolidin-1-yl)ethoxy]phenyl and phenyl groups, respectively (the 5R,6S-stereoisomer). It is a selective estrogen receptor modulator indicated for the prevention and treatment of osteoporosis in post-menopausal women. It has a role as an antineoplastic agent, a cardioprotective agent, an estrogen receptor agonist, an estrogen receptor antagonist and a bone density conservation agent. It is a member of tetralins, an aromatic ether, a member of naphthols and a N-alkylpyrrolidine.
Lasofoxifene is a non-steroidal 3rd generation selective estrogen receptor modulator (SERM) that selectively binds to both ERα and ERβ with high affinity. It is a naphthalene derivative marketed for prevention and treatment of osteoporosis and for the treatment of vaginal atrophy. It was initially developed as Oporia by Pfizer as a treatment for postmenopausal osteoporosis and vaginal atrophy, in which were both rejected for approval by FDA. Later Fablyn was developed as a result of a research collaboration between Pfizer and Ligand Pharmaceuticals with a newly submitted New Drug Application in 2008. It gained approval by European Commission in March 2009. Ligand Pharmaceuticals signed a license agreement with Sermonix Pharmaceuticals for the development and commercialization of oral lasofoxifene in the USA.
Lasofoxifene is a non-steroidal, naphthalene-derived, third-generation selective estrogen receptor modulator (SERM) with potential antineoplastic and anti-osteoporotic activities. Upon oral administration, lasofoxifene selectively binds to both estrogen receptor alpha (ERalpha; ESR1) and estrogen receptor beta (ERbeta; ESR2) with high affinity and mimics the effects of endogenous estradiol with varying agonist and antagonist effects in ER-expressing tissues. Blockade of ERalpha by lasofoxifene may potentially inhibit estrogen-dependent cancer cell proliferation in ER-expressing cancers. Lasofoxifene may also bind to the certain mutant forms of ERalpha, including the Y537S ESR1 mutant, making it potentially useful in the treatment of tumors that have acquired resistance to other ER-targeting agents.
See also: Lasofoxifene Tartrate (annotation moved to).

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Drug Indication
Investigated for use/treatment in postmenopausal osteoporosis to reduce the risk of both vertebral and novertebral fractures, as well as address other postmenopausal conditions, including reduction in risk of breast cancer and treatment of vulvar and vaginal atrophy (VVA)
Fablyn is indicated for the treatment of osteoporosis in postmenopausal women at increased risk of fracture. A significant reduction in the incidence of vertebral and non-vertebral fractures but not hip fractures has been demonstrated (see section 5. 1). When determining the choice of Fablyn or other therapies, including oestrogens, for a postmenopausal woman, consideration should be given to menopausal symptoms, effects on uterine and breast tissues, and cardiovascular risks and benefits (see section 5. 1).

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Mechanism of Action
Lasofoxifene mediates an agonist effect on estrogen receptors expressed on bone to mimic the positive effects of estrogen to reduce the production and lifespan of osteoclasts via altering the NF-kappaB ligand (RANKL)/RANK/osteoprotegerin system, stimulation of osteoblast (the bone forming cells) activity and additional effects on calcium homeostasis. It acts as an antagonist at uterus and mammary glands by suppressing the estrogen signaling in oncogenic pathways and inhibits the downstream gene transcription. A study also suggests that lasofoxifene may also act as an inverse agonist at CB2 cannabinoid receptor which is expressed in bone to inhibit osteoclast formation and resorptive activity.

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Pharmacodynamics
Lasofoxifene exhibits both significant estrogenic and antiestrogenic activity both in vitro and in vivo, targeting any tissues that possess ERs, such as bone, uterus, breast, blood vessels, and liver. Binding assays demonstrated high affinity of the compound for both ERα and ERβ in a tissue-dependent manner. It mimics the effects of estradiol with varying 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

Typically exists as solid at room temperature

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.)