Letrozole (CGS 20267)

For research use only.

Catalog No.S1235

23 publications

Letrozole (CGS 20267) Chemical Structure

CAS No. 112809-51-5

Letrozole (CGS 20267) is a third generation inhibitor of aromatase with IC50 of 0.07-20 nM in cell-free assays.It has no effect on the plasma levels of 17α-OH progesterone, thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), or androstenedione and does not affect normal urine electrolyte excretion or thyroid function in clinical studies. Letrozole induces autophagy.

Selleck's Letrozole (CGS 20267) has been cited by 23 publications

Purity & Quality Control

Choose Selective Aromatase Inhibitors

Biological Activity

Description Letrozole (CGS 20267) is a third generation inhibitor of aromatase with IC50 of 0.07-20 nM in cell-free assays.It has no effect on the plasma levels of 17α-OH progesterone, thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), or androstenedione and does not affect normal urine electrolyte excretion or thyroid function in clinical studies. Letrozole induces autophagy.
Targets
Aromatase [1]
(Cell-free assay)
0.07 nM-20 nM
In vitro

Letrozole potently inhibits aromatase derived from a variety of different sources including human placental microsomes, particulate fractions of human breast cancer, rat ovarian microsomes, MCF-7 cells transfected with aromatase (MCF-7Ca), JEG-3 human choriocarcinoma cells , CHO cells, hamster ovarian tissue, and particulate fractions of human breast cancer with IC50 of 11, 2, 7, 0.07, 0.07, 1.4, 20 and 0.8 nM. In the non-cellular systems, the IC50 of letrozole is calculated to be 1-13 nM. [1] Letrozole maximally inhibits estradiol production in vitro in LH-stimulated hamster ovarian tissue at 0.1 μM with an IC50 of 0.02 μM and does not significantly affect progesterone production up to 350 μM. In ACTH-stimulated rat adrenal tissue in vitro, aldosterone production is inhibited by with an IC50 of 210 μM. [2] Letrozole inhibits growth of the MCF-7 epithelial breast cancer cells in a dose-dependent way with IC50 of 1 nM. Inhibition can be observesed even at the very low concentrations tested (0.1 nM). Treatment of normal MCF-12A epithelial cells with letrozole did not affect their growth even when high letrozole concentrations (100 nM) or prolonged culture times. Letrozole (10 nM) significantly suppressed the stimulatory effects of 4-androstene-3,17-dione (100 nM) or testosterone (100 nM) on MCF-7 cell proliferation. Concurrent administration of 17-β-estradiol with letrozole (10 nM) decreased the stimulatory effect of the enzymatic activity of MMP-2 and - 9 released by estradiol. [3]

Cell Data
Cell Lines Assay Type Concentration Incubation Time Formulation Activity Description PMID
JEG3 M4qyS2Z2dmO2aX;uJIF{e2G7 NETmPYxKdmirYnn0bY9vKG:oIHHyc41ifGG|ZTDhZ5Rqfmm2eTDpckBpfW2jbjDKSWc{KGOnbHzzMEBKSzVyPUCuNFAxQDoQvF2= M2LqWFxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzF6NUmwNlczLz5zOEW5NFI4OjxxYU6=
JEG3 NWjXTo9kTnWwY4Tpc44h[XO|YYm= M{jDO2lvcGmkaYTpc44hd2ZiYYLvcYF1[XOnIHnuJIh2dWGwIFrFS|Mh[2WubIOgZpkhe2OrboTpcIxifGmxbjDzdIVkfHKxbXX0dpktKEmFNUC9NE4xODB6Od88US=> M{O2eVxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyMUS4OVY1Lz5{MEG0PFU3PDxxYU6=
MDA-MB-435 MV\Hdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? MUm0PEBpenN? M1nwWWdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJG1FSS2PQj20N|Uh[2WubIOgZYZ1\XJiNEigbJJ{KGK7IIP1cIZwemixZHHtbY5mKEJiYYPzZZktKEeLNUC9NE4xPjgQvF2= MWK8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zODl3MEi5PEc,OjB7NUC4PVg9N2F-
IGROV1 NHHIRYJIem:5dHigbY5pcWKrdHnvckBie3OjeR?= MmrmOFghcHK| MlvCS5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gTWdTV1ZzIHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTBwMEm1{txO MlXsQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjB7NUC4PVgoRjJyOUWwPFk5RC:jPh?=
MDA-MB-231 Ml7vS5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? MXy0PEBpenN? NHryRlVIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBOTEFvTVKtNlMy[2WubIOgZYZ1\XJiNEigbJJ{KGK7IIP1cIZwemixZHHtbY5mKEJiYYPzZZktKEeLNUC9NE4yPc7:TR?= NYn5clBLRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
T47D M{TIPWdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 Mk\3OFghcHK| M2rIbGdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJHQ1P0RiY3XscJMh[W[2ZYKgOFghcHK|IHL5JJN2dG[xcnjv[IFucW6nIFKgZZN{[XluIFfJOVA:OC52NN88US=> MYO8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zODl3MEi5PEc,OjB7NUC4PVg9N2F-
MCF7 M3TmOmdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MlPuOFghcHK| NF7VXWJIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBOS0Z5IHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTBwN988US=> M2rMZVxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
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SKOV3 M{fPT2dzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MV60PEBpenN? MkTES5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gV2tQXjNiY3XscJMh[W[2ZYKgOFghcHK|IHL5JJN2dG[xcnjv[IFucW6nIFKgZZN{[XluIFfJOVA:OS5yOd88US=> NWXIcXhbRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
NCI/ADR-RES M3SybWdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MUW0PEBpenN? MYjHdo94fGhiaX7obYJqfGmxbjDv[kBpfW2jbjDOR2kwSUSULWLFV{Bk\WyuczDh[pRmeiB2ODDodpMh[nlic4Xs[o9zcG:mYX3pcoUhSiCjc4PhfUwhT0l3ME2xMlE3|ryP M{HVW|xiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
MDA-N NV;UTncxT3Kxd4ToJIlvcGmkaYTpc44h[XO|YYm= NGrZOpE1QCCqcoO= M1[1N2dzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJG1FSS2QIHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTFwNkJOwG0> MnnvQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjB7NUC4PVgoRjJyOUWwPFk5RC:jPh?=
OVCAR5 NITTU3BIem:5dHigbY5pcWKrdHnvckBie3OjeR?= NHjmS|I1QCCqcoO= NUDLe2xbT3Kxd4ToJIlvcGmkaYTpc44hd2ZiaIXtZY4hV1[FQWK1JINmdGy|IHHmeIVzKDR6IHjyd{BjgSC|dXzmc5Jpd2SjbXnu[UBDKGG|c3H5MEBIUTVyPUGuOlLPxE1? NGTD[Fc9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{MEm1NFg6QCd-MkC5OVA5QTh:L3G+
Hs 578T NEnQRpRIem:5dHigbY5pcWKrdHnvckBie3OjeR?= NIeyXXo1QCCqcoO= M3npcmdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJGh{KDV5OGSgZ4VtdHNiYX\0[ZIhPDhiaILzJIJ6KHO3bH\vdohw\GGvaX7lJGIh[XO|YYmsJGdKPTB;Mj6xO:69VQ>? MXO8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zODl3MEi5PEc,OjB7NUC4PVg9N2F-
OVCAR8 NWTSNZh4T3Kxd4ToJIlvcGmkaYTpc44h[XO|YYm= MV60PEBpenN? NW[ySWRnT3Kxd4ToJIlvcGmkaYTpc44hd2ZiaIXtZY4hV1[FQWK4JINmdGy|IHHmeIVzKDR6IHjyd{BjgSC|dXzmc5Jpd2SjbXnu[UBDKGG|c3H5MEBIUTVyPUSuOe69VQ>? MkXZQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjB7NUC4PVgoRjJyOUWwPFk5RC:jPh?=
OVCAR3 Mmj0S5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? MYm0PEBpenN? MkPFS5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gU3ZESVJ|IHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTVwOEhOwG0> NXHyR5pYRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
MCF7a M1HzeWN6fG:2b4jpZ4l1gSCjc4PhfS=> M1XNUVExKGSjeYO= MYHDfZRwfG:6aXPpeJkh[WejaX7zeEBpfW2jbjDNR2Y4[SClZXzsd{BmgHC{ZYPzbY5oKFSndD3v[oYuO2KndHHIV2QyNUG{b32gZZN{\XO|ZXSgZZMhcW6qaXLpeIlwdiCxZjDUV3Que3SrbYXsZZRm\CClZXzsJJBzd2yrZnXyZZRqd25ibXXhd5Vz\WRiYX\0[ZIhOTBiZHH5d{whTUN3ME2wMlAxODByNN88US=> MWK8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zOjl3MUC3OEc,OjJ7NUGwO|Q9N2F-
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MCF7 M3n4N2N6fG:2b4jpZ4l1gSCjc4PhfS=> Mm[0NlQhfG9iOU[gbJJ{ NXzvb|B2S3m2b4TvfIlkcXS7IHHnZYlve3RiaIXtZY4hVUOINzDj[YxteyCjZoTldkAzPCC2bzC5OkBpenNuIFnDOVA:OC5yMt88US=> NX\6cWNQRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkSzOFU1QDFpPkK0N|Q2PDhzPD;hQi=>
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MCF7 MVrHdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? M33vd|czKGi{cx?= NE\ZRYtIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBOS0Z5IHPlcIx{KGmwY4XiZZRm\CCob4KgO|IhcHK|IHL5JINmdGxiY3;1cpRqdmdiYnHz[YQhdWW2aH;kMEBIUTVyPUSuNe69VQ>? MWS8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8{ODh{MkexN{c,OzB6MkK3NVM9N2F-
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insect cells M1PCUmZ2dmO2aX;uJIF{e2G7 MUHJcohq[mm2aX;uJI9nKHKnY3;tZolv[W62IHj1cYFvKGG{b33heIF{\SCneIDy[ZN{\WRiaX6gZoFkfWyxdnnyeZMhcW6oZXP0[YQhcW6|ZXP0JINmdGy|IIXzbY5oKE9vYnXufpltKG[udX;y[ZNk\WmwIHLlcpp6dCCnc4TldkBieyC|dXLzeJJifGViaX6gdJJme2WwY3Wgc4YhVkGGUFig[4Vv\XKjdHnu[{B{gXO2ZX2gZpkh\my3b4Lld4NmdmOnIHLhd4VlKGGwYXz5d4l{NCCLQ{WwQVAvODBzOd88US=> NHHnN|M9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9|MUSxOlc{QCd-M{G0NVY4Ozh:L3G+
MCF-7aro M33DUGZ2dmO2aX;uJIF{e2G7 MWmxJIhz MlXCTY5pcWKrdHnvckBw\iCjcn;tZZRie2ViaX6gbJVu[W5iTVPGMVdiem9iY3XscJMhfXOrbnegX|Fj\XSjLUPIYUBidmS{b4P0[Y5m\GmxbnWgZZMhe3Wkc4TyZZRmKGmwY4XiZZRm\CCob4KgNUBpeiCkeTDsbZF2cWRic3PpcpRqdGyjdHnvckBkd3WwdHnu[{Bu\XSqb3SsJGlEPTB;MD6wNFE6|ryP MVm8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8{OTd|MkK1Nkc,OzF5M{KyOVI9N2F-
insect cells NYK2bHhZTnWwY4Tpc44h[XO|YYm= MWOzNEBucW6| NHjjd5ZKdmirYnn0bY9vKG:oIHj1cYFvKHKnY3;tZolv[W62IHHyc41ifGG|ZTDlfJBz\XO|ZXSgbY4h[mGldXzveolzfXNiaX7m[YN1\WRiaX7z[YN1KGOnbHzzJJV{cW6pIF:tZoVvgnmuZnz1c5Jme2OnaX6gZoVvgnmuIHXzeIVzKGG|IIP1ZpN1emG2ZTDh[pRmeiB|MDDtbY5{NCCLQ{WwQVAvODBzMd88US=> NUmyW5VqRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:ve5d4NmWkaT7hZ{52cy:laHXtZoww[2:vcH;1coRgemWyb4L0Y4NiemRxQ1jFUWJNOTR2ND:nQmNpTU2ETEyvZV4>

... Click to View More Cell Line Experimental Data

In vivo Letrozole inhibits aromatase in vivo with ED50 of 1-3 μg/kg p.o.. [2] Letrozole displays anti-endocrine effects. Letrozole inhibits androstenedione-induced uterine hypertrophy in immature rats with ED50 of 1-3 μg/kg. In the adult female rat, Letrozole (0.3-1 mg/kg daily p.o., 14 days) completely interrupts ovarian cyclicity and reduces uterine weight and serum estradiol (E2) concentrations to a similar extent to that seen after ovariectomy. [1] Letrozole induces dose-dependent regression of estrogen-dependent, 9,10-dimethylbenz-a-anthracene (DMBA)-induced mammary tumors in adult female rats. The ED50 for Letrozole is determined to be 10 - 30 µg/kg/day, with complete inhibition at a daily dose of 10 µg/day. [4] Letrozole produces dose-dependent inhibition of tumor growth of MCF-7 cells transfected with human aromatase gene (MCF-7Ca) implanted athymic nude mice, with complete inhibition at 20 mg/kg per day p.o.. [5]

Protocol

Kinase Assay:

[6]

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Human placental aromatase activity:

The assay is performed in a total volume of 1 mL at 37 ℃. Unless otherwise noted, the incubation mixture contains 11 nM [4- 14C] androstene-3, 17-dione ([4- 14C]A), 24 mM NADPH (tetrasodium salt Type III), the appropriate concentrations of the desired inhibitor, and 120 μg of microsomal protein. The (4- 14C)A is added as a solution in 1.7% ethanol in 0.05 M potassium phosphate buffer (pH 7.4), so that the final concentration of ethanol does not exceed 0.02% (v/v). The reaction is started by the addition of enzyme and stopped after 20 min by the addition of 7 vol of ethyl acetate. The mixture is agitated on a vortex mixer and centrifuged at 600 g for 5 min. The aqueous phase is re-extracted with 7 vol of ethyl acetate, and the combined extracts are evaporated to dryness using an Evapo-Mix. Over 99% of the radio- active of [4- 14C] added is recovered using this extraction system. The residue obtained is dissolved in 150 μL acetone, and 100 μL aliquots are chromatographed for 65 min on thin-layer plates precoated with silica gel 60 using ethyl: acetate: isooctane (140:60, v/v; system A) or toluene: chloroform: methanol (70:140:20; system B). The radioactive zones of the plate are located with a Berthold LB 2760 thin-layer scanner. The radioactive estradiol (E2) and estrone (E1) neaks are identified by comparison with authentic standards. The corresponding bonding band of silica gel is transferred to vials containing 10 mL of scintillation fluid, and counted with a 6880 Liquid Scintillation system.
Cell Research:

[3]

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  • Cell lines: Human breast cancer cells MCF-7
  • Concentrations: ~100 nM
  • Incubation Time: 1 days
  • Method:

    Cells are seeded in duplicate at 5,000 to 10,000 cells per well in 24-well plates. The day after plating, different concentrations of Letrozole are added. At the end of incubation, cells are trypsinizated and placed in Isotone solution and counted immediately using a Coulter particle-counter.


    (Only for Reference)
Animal Research:

[5]

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  • Animal Models: Human breast carcinoma xenografts MCF-7 with human aromatase gene (MCF-7Ca)
  • Dosages: 20 mg/kg/day
  • Administration: orally administered by gavage once every 2 days
    (Only for Reference)

Solubility (25°C)

In vitro DMSO 57 mg/mL (199.78 mM)
Water Insoluble
Ethanol Insoluble
In vivo Add solvents to the product individually and in order(Data is from Selleck tests instead of citations):
0.5% CMC Na
For best results, use promptly after mixing.
10mg/mL

* Please note that Selleck tests the solubility of all compounds in-house, and the actual solubility may differ slightly from published values. This is normal and is due to slight batch-to-batch variations.

Chemical Information

Molecular Weight 285.3
Formula

C17H11N5

CAS No. 112809-51-5
Storage powder
in solvent
Synonyms N/A
Smiles C1=CC(=CC=C1C#N)C(C2=CC=C(C=C2)C#N)N3C=NC=N3

In vivo Formulation Calculator (Clear solution)

Step 1: Enter information below (Recommended: An additional animal making an allowance for loss during the experiment)
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Bio Calculators

Molarity Calculator

Molarity Calculator

Calculate the mass, volume or concentration required for a solution. The Selleck molarity calculator is based on the following equation:

Mass (mg) = Concentration (mM) × Volume (mL) × Molecular Weight (g/mol)

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*When preparing stock solutions, please always use the batch-specific molecular weight of the product found on the via label and SDS / COA (available on product pages).

Dilution Calculator

Dilution Calculator

Calculate the dilution required to prepare a stock solution. The Selleck dilution calculator is based on the following equation:

Concentration (start) x Volume (start) = Concentration (final) x Volume (final)

This equation is commonly abbreviated as: C1V1 = C2V2 ( Input Output )

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* When preparing stock solutions always use the batch-specific molecular weight of the product found on the vial label and SDS / COA (available online).

The Serial Dilution Calculator Equation

  • Serial Dilutions

  • Computed Result

  • C1=C0/X C1: LOG(C1):
    C2=C1/X C2: LOG(C2):
    C3=C2/X C3: LOG(C3):
    C4=C3/X C4: LOG(C4):
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Molecular Weight Calculator

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To calculate molar mass of a chemical compound, please enter its chemical formula and click 'Calculate'.

Definitions of molecular mass, molecular weight, molar mass and molar weight:

Molecular mass (molecular weight) is the mass of one molecule of a substance and is expressed in the unified atomic mass units (u). (1 u is equal to 1/12 the mass of one atom of carbon-12)
Molar mass (molar weight) is the mass of one mole of a substance and is expressed in g/mol.

Molarity Calculator

Mass Concentration Volume Molecular Weight

Clinical Trial Information

NCT Number Recruitment interventions Conditions Sponsor/Collaborators Start Date Phases
NCT04714619 Recruiting Drug: CB-103 Advanced Breast Cancer MedSIR|Cellestia Biotech AG April 2021 Phase 2
NCT04735367 Not yet recruiting Drug: palbociclib plus letrozole Breast Cancer Pfizer February 1 2021 --
NCT04227327 Recruiting Drug: Abemaciclib|Drug: Aromatase Inhibitors Advanced Breast Cancer University of Milano Bicocca January 7 2020 Phase 2
NCT03870919 Recruiting Drug: Palbociclib|Other: locoregional treatment Breast Cancer Stage IV|Radiotherapy|Surgery UNICANCER|Pfizer October 23 2019 Not Applicable

Tech Support

Answers to questions you may have can be found in the inhibitor handling instructions. Topics include how to prepare stock solutions, how to store inhibitors, and issues that need special attention for cell-based assays and animal experiments.

Handling Instructions

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Aromatase Signaling Pathway Map

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Cell Lines Assay Type Concentration Incubation Time Formulation Activity Description PMID