Letrozole (CGS 20267)

Catalog No.S1235

For research use only.

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.

Letrozole (CGS 20267) Chemical Structure

CAS No. 112809-51-5

Selleck's Letrozole (CGS 20267) has been cited by 28 publications

Purity & Quality Control

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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 MnjkSpVv[3Srb36gZZN{[Xl? M13hfGlvcGmkaYTpc44hd2ZiYYLvcYF1[XOnIHHjeIl3cXS7IHnuJIh2dWGwIFrFS|Mh[2WubIOsJGlEPTB;MD6wNFA5Qc7:TR?= MYC8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8yQDV7MEK3Nkc,OTh3OUCyO|I9N2F-
JEG3 MY\GeY5kfGmxbjDhd5NigQ>? NVP3RZhXUW6qaXLpeIlwdiCxZjDhdo9u[XSjc3WgbY4hcHWvYX6gTmVIOyClZXzsd{BjgSC|Y3nueIltdGG2aX;uJJNx\WO2cn;t[ZRzgSxiSVO1NF0xNjByMEi5{txO NGf3elg9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{MEG0PFU3PCd-MkCxOFg2PjR:L3G+
MDA-MB-435 MlH5S5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? NFvKXXc1QCCqcoO= MkOxS5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gUWRCNU2ELUSzOUBk\WyuczDh[pRmeiB2ODDodpMh[nlic4Xs[o9zcG:mYX3pcoUhSiCjc4PhfUwhT0l3ME2wMlA3P87:TR?= M4\zSFxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
IGROV1 MoXuS5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? NGHlU4M1QCCqcoO= M3fRbWdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJGlIWk:YMTDj[YxteyCjZoTldkA1QCCqcoOgZpkhe3WuZn;ybI9l[W2rbnWgRkBie3OjeTygS2k2OD1yLkC5Oe69VQ>? NF\RZmE9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{MEm1NFg6QCd-MkC5OVA5QTh:L3G+
MDA-MB-231 MW\Hdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? NXKyblBPPDhiaILz NXW1WIU{T3Kxd4ToJIlvcGmkaYTpc44hd2ZiaIXtZY4hVUSDLV3CMVI{OWOnbHzzJIFnfGW{IES4JIhzeyCkeTDzeYxnd3Kqb3ThcYlv\SCEIHHzd4F6NCCJSUWwQVAvOTYQvF2= M33JWlxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
T47D NHm1W5ZIem:5dHigbY5pcWKrdHnvckBie3OjeR?= NYrIZ4ViPDhiaILz NFG4ZmVIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBVPDeGIHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTBwNEVOwG0> NW\MXI5WRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
MCF7 M1HTVGdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MlnBOFghcHK| MkLSS5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gUWNHPyClZXzsd{Bi\nSncjC0PEBpenNiYomgd5Vt\m:{aH;kZY1qdmViQjDhd5NigSxiR1m1NF0xNjgQvF2= NF;SNWw9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{MEm1NFg6QCd-MkC5OVA5QTh:L3G+
OVCAR4 MoHsS5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? MkXTOFghcHK| M{\IbGdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJG9XS0GUNDDj[YxteyCjZoTldkA1QCCqcoOgZpkhe3WuZn;ybI9l[W2rbnWgRkBie3OjeTygS2k2OD1yLki4{txO NUX1elFZRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
BT549 NIrVPHVIem:5dHigbY5pcWKrdHnvckBie3OjeR?= MVK0PEBpenN? NX;WOI5WT3Kxd4ToJIlvcGmkaYTpc44hd2ZiaIXtZY4hSlR3NEmgZ4VtdHNiYX\0[ZIhPDhiaILzJIJ6KHO3bH\vdohw\GGvaX7lJGIh[XO|YYmsJGdKPTB;MD64Pe69VQ>? M4rD[|xiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
SKOV3 M3TkRmdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MVS0PEBpenN? NY\kTFV2T3Kxd4ToJIlvcGmkaYTpc44hd2ZiaIXtZY4hW0uRVkOgZ4VtdHNiYX\0[ZIhPDhiaILzJIJ6KHO3bH\vdohw\GGvaX7lJGIh[XO|YYmsJGdKPTB;MT6wPe69VQ>? NX73Z5Q2RGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkC5OVA5QThpPkKwPVUxQDl6PD;hQi=>
NCI/ADR-RES MVvHdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? MY[0PEBpenN? M1rmTmdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJG5EUS:DRGKtVmVUKGOnbHzzJIFnfGW{IES4JIhzeyCkeTDzeYxnd3Kqb3ThcYlv\SCEIHHzd4F6NCCJSUWwQVEvOTcQvF2= M2rLcVxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
MDA-N MXfHdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? MVm0PEBpenN? M2X4NWdzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJG1FSS2QIHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTFwNkJOwG0> MVG8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zODl3MEi5PEc,OjB7NUC4PVg9N2F-
OVCAR5 M2DNNGdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 NFzwfJo1QCCqcoO= MonoS5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gU3ZESVJ3IHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTFwNkNOwG0> M37U[FxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJyOUWwPFk5Lz5{MEm1NFg6QDxxYU6=
Hs 578T M2rDXWdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 MmP5OFghcHK| M3zkV2dzd3e2aDDpcohq[mm2aX;uJI9nKGi3bXHuJGh{KDV5OGSgZ4VtdHNiYX\0[ZIhPDhiaILzJIJ6KHO3bH\vdohw\GGvaX7lJGIh[XO|YYmsJGdKPTB;Mj6xO:69VQ>? MUK8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zODl3MEi5PEc,OjB7NUC4PVg9N2F-
OVCAR8 MUXHdo94fGhiaX7obYJqfGmxbjDhd5NigQ>? NYL0S452PDhiaILz Mo\5S5Jwf3SqIHnubIljcXSrb36gc4YhcHWvYX6gU3ZESVJ6IHPlcIx{KGGodHXyJFQ5KGi{czDifUB{fWyob4Loc4RidWmwZTDCJIF{e2G7LDDHTVUxRTRwNd88US=> MmDPQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjB7NUC4PVgoRjJyOUWwPFk5RC:jPh?=
OVCAR3 Mn74S5Jwf3SqIHnubIljcXSrb36gZZN{[Xl? NX7ETYc5PDhiaILz NEWzd3dIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBQXkODUkOgZ4VtdHNiYX\0[ZIhPDhiaILzJIJ6KHO3bH\vdohw\GGvaX7lJGIh[XO|YYmsJGdKPTB;NT64O:69VQ>? NHe5S5M9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{MEm1NFg6QCd-MkC5OVA5QTh:L3G+
MCF7a NYDDPZBNS3m2b4TvfIlkcXS7IHHzd4F6 MnTrNVAh\GG7cx?= M1W2UWN6fG:2b4jpZ4l1gSCjZ3HpcpN1KGi3bXHuJG1ETjejIHPlcIx{KGW6cILld5NqdmdiVHX0MY9n\i1|YnX0ZWhUTDFvQYLvcUBie3Onc4Pl[EBieyCrbnjpZol1cW:wIH;mJHRUXC2|dHnteYxifGWmIHPlcIwheHKxbHnm[ZJifGmxbjDt[YF{fXKnZDDh[pRmeiBzMDDkZZl{NCCHQ{WwQVAvODByMEC0{txO MYq8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zOjl3MUC3OEc,OjJ7NUGwO|Q9N2F-
V79MZh NVP4ZYxvTnWwY4Tpc44h[XO|YYm= MUDJcohq[mm2aX;uJI9nKGi3bXHuJGN[WDFzQkKg[ZhxemW|c3XkJIlvKGijbYP0[ZIhXjd7TWroJINmdGy|IIXzbY5oKFtzLEKtN2heNTFzLXTlc5h6NWOxcoTpZ49{fGW{b37lJIF{KHO3YoP0doF1\SxiSVO1NF0yNjR{zszN MXO8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zOzJ6MUixNkc,OjN{OEG4NVI9N2F-
V79MZh NF\IeXVHfW6ldHnvckBie3OjeR?= M{DWd2lvcGmkaYTpc44hd2ZiaIXtZY4hS1mSMUHCNUBmgHC{ZYPz[YQhcW5iaHHtd5RmeiCYN{nNXogh[2WubIOgeZNqdmdiW{GsNk0{UF1vMUGt[IVwgHlvY3;yeIlkd3O2ZYLvcoUh[XNic4Xid5Rz[XSnLDDJR|UxRTJwNkNOwG0> MWC8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zOzJ6MUixNkc,OjN{OEG4NVI9N2F-
H295R MVnGeY5kfGmxbjDhd5NigQ>? NFPxdVc2KHWP MXqyOEBpenN? MYnJcohq[mm2aX;uJI9nKEO\UEG5JIlvKGi3bXHuJGgzQTWUIHPlcIx{KHW|aX7nJHsy[mW2YT2zTEhPMV1vYX7kdo9{fC12LXXu[U0{NDF5LXTpc45mKGG2IEWgeW0h[W[2ZYKgNlQhcHK|IHL5JJRzcXSrYYTl[EB4[XSncjDy[Yxm[XOnIHHzd4F6 NFrMcWQ9[SC2YYLn[ZQ:L1:kbHHub{chcHKnZk2nbJR1eHN8Lz;weYJu\WRwbnPibU5vdG1wbnnoModwfi9{NECyOVA3QSd-MkSwNlUxPjl:L3G+
MCF7 NYXDcHJIS3m2b4TvfIlkcXS7IHHzd4F6 MknXO|IhcHK| Mme3R5l1d3SxeHnjbZR6KGGpYXnud5Qh\XO2cn;n[Y4u\GWyZX7k[Y51KGi3bXHuJG1ETjdiY3XscJMh[W[2ZYKgO|IhcHK|IHL5JG1VXCCjc4PhfUwhUUN3ME2wMlAxP87:TR?= MVq8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:ydXLt[YQvdmOkaT7ucI0vdmmqLnfvek8zPDN2NUS4NUc,OjR|NEW0PFE9N2F-
MCF7 M4HJNWN6fG:2b4jpZ4l1gSCjc4PhfS=> MlLVNlQhfG9iOU[gbJJ{ MWDDfZRwfG:6aXPpeJkh[WejaX7zeEBpfW2jbjDNR2Y4KGOnbHzzJIFnfGW{IEK0JJRwKDl4IHjyd{whUUN3ME2wMlAz|ryP NYq2O|dlRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxMkSzOFU1QDFpPkK0N|Q2PDhzPD;hQi=>
JEG-3 M1LYSWZ2dmO2aX;uJIF{e2G7 NV6zWINjUW6qaXLpeIlwdiCxZjDhdo9u[XSjc3WgLJVvc26xd36gc5Jq\2mwKTDlfJBz\XO|ZXSgbY4hUkWJLUOgZ4VtdHNuIFnDOVA:OC5yMEC4Pe69VQ>? Ml3aQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjV7OUK4PFAoRjJ3OUmyPFgxRC:jPh?=
insect cells NGTmT29HfW6ldHnvckBie3OjeR?= MVKzNEBucW6| NWG2dZN5UW6qaXLpeIlwdiCxZjDy[YNwdWKrbnHueEBpfW2jbjDDXXAyQSCneIDy[ZN{\WRiaX6gZoFkfWyxdnnyeZMhcW6oZXP0[YQhcW6|ZXP0JINmdGy|IIXzbY5oKE2IQzDhd{B{fWK|dILheIUhdWWjc4Xy[YQh[W[2ZYKgN|AhdWmwczDifUBndHWxcn;t[ZRzcWNiYX7hcJl{cXNuIFnDOVA:OC5yMEWz{txO M3XteVxiKHSjcnfleF0oZ2KuYX7rK{BpemWoPTfoeJRxezpxL4D1Zo1m\C6wY3LpMo5tdS6waXiu[493NzJ5NkS3N|Y4Lz5{N{[0O|M3PzxxYU6=
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T47D M{fXOGZ2dmO2aX;uJIF{e2G7 M33yU|I1KGi{cx?= MYjJcohq[mm2aX;uJI9nKGG{b33heIF{\SCjY4Tpeol1gSCrbjDoeY1idiCWNEfEJINmdGy|IHHmeIVzKDJ2IHjyd{whUUN3ME2yPU42|ryP MlHCQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOjh2MkewNVcoRjJ6NEK3NFE4RC:jPh?=
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MDA-MB-231 M{PGZmdzd3e2aDDpcohq[mm2aX;uJIF{e2G7 M{PrclczKGi{cx?= NFj1dXVIem:5dHigbY5pcWKrdHnvckBw\iCqdX3hckBOTEFvTVKtNlMyKGOnbHzzJIlv[3WkYYTl[EBnd3JiN{KgbJJ{KGK7IHPlcIwh[2:3boTpcoch[mG|ZXSgcYV1cG:mLDDHTVUxRTFyzszN MnuzQIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOzB6MkK3NVMoRjNyOEKyO|E{RC:jPh?=
insect cells NIXuZ3dHfW6ldHnvckBie3OjeR?= MVXJcohq[mm2aX;uJI9nKHKnY3;tZolv[W62IHj1cYFvKGG{b33heIF{\SCneIDy[ZN{\WRiaX6gZoFkfWyxdnnyeZMhcW6oZXP0[YQhcW6|ZXP0JINmdGy|IIXzbY5oKE9vYnXufpltKG[udX;y[ZNk\WmwIHLlcpp6dCCnc4TldkBieyC|dXLzeJJifGViaX6gdJJme2WwY3Wgc4YhVkGGUFig[4Vv\XKjdHnu[{B{gXO2ZX2gZpkh\my3b4Lld4NmdmOnIHLhd4VlKGGwYXz5d4l{NCCLQ{WwQVAvODBzOd88US=> MnS4QIEhfGG{Z3X0QUdg[myjbnunJIhz\WZ;J3j0eJB{Qi9xcIXicYVlNm6lYnmucoxuNm6raD7nc5YwOzF2MU[3N|goRjNzNEG2O|M5RC:jPh?=
MCF-7aro NH24[XpHfW6ldHnvckBie3OjeR?= NIKyTVkyKGi{ MYLJcohq[mm2aX;uJI9nKGG{b33heIF{\SCrbjDoeY1idiCPQ1[tO4FzdyClZXzsd{B2e2mwZzDbNYJmfGFvM1jdJIFv\HKxc4TlcoVlcW:wZTDhd{B{fWK|dILheIUhcW6ldXLheIVlKG[xcjCxJIhzKGK7IHzpdZVq\CC|Y3nueIltdGG2aX;uJINwfW62aX7nJI1mfGixZDygTWM2OD1yLkCwNVnPxE1? NVzBSYRRRGFidHHy[4V1RSehYnzhcosoKGi{ZX[9K4h1fHC|Oj:vdJVjdWWmLn7jZokvdmyvLn7pbE5od3ZxM{G3N|IzPTJpPkOxO|MzOjV{PD;hQi=>
insect cells NFP0[IVHfW6ldHnvckBie3OjeR?= M1n4eFMxKG2rboO= NYfL[mtkUW6qaXLpeIlwdiCxZjDoeY1idiC{ZXPvcYJqdmGwdDDhdo9u[XSjc3Wg[ZhxemW|c3XkJIlvKGKjY4Xsc5ZqenW|IHnu[oVkfGWmIHnud4VkfCClZXzsd{B2e2mwZzDPMYJmdnq7bH\seY9z\XOlZXnuJIJmdnq7bDDld5RmeiCjczDzeYJ{fHKjdHWgZYZ1\XJiM{CgcYlveyxiSVO1NF0xNjByMUJOwG0> MXW8ZUB1[XKpZYS9K39jdGGwazegbJJm\j1paIT0dJM7Ny:5d4eu[YJqNmGlLoXrM4Np\W2kbD;jc41xd3WwZG;y[ZBwenShY3Hy[E9EUEWPQlyxOFQ1Nyd-Q3jFUWJNRC:jPh?=
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 (from reference)

Kinase Assay:

[6]

  • 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]

  • 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.

Animal Research:

[5]

  • 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

Solubility (25°C)

In vitro

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

Chemical Information

Molecular Weight 285.3
Formula

C17H11N5

CAS No. 112809-51-5
Storage 3 years -20°C powder
2 years -80°C in solvent
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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Working concentration: mg/ml;

Method for preparing DMSO master liquid: mg drug pre-dissolved in μL DMSO ( Master liquid concentration mg/mL, Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug. )

Method for preparing in vivo formulation: Take μL DMSO master liquid, next addμL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O, mix and clarify.

Method for preparing in vivo formulation: Take μL DMSO master liquid, next add μL Corn oil, mix and clarify.

Note: 1. Please make sure the liquid is clear before adding the next solvent.
2. Be sure to add the solvent(s) in order. You must ensure that the solution obtained, in the previous addition, is a clear solution before proceeding to add the next solvent. Physical methods such
as vortex, ultrasound or hot water bath can be used to aid dissolving.

Molarity Calculator

Mass Concentration Volume Molecular Weight

Clinical Trial Information

NCT Number Recruitment Interventions Conditions Sponsor/Collaborators Start Date Phases
NCT05181033 Not yet recruiting Drug: Lenvatinib + Letrozole|Drug: Fulvestrant Breast Cancer National University Hospital Singapore|Eisai Co. Ltd. January 2022 Phase 2
NCT05067309 Not yet recruiting Drug: Letrozole 2.5mg Termination of Early Pregnancy in Scarred Uterus Ahmed Elsayed Aref|Sohag University October 1 2021 --
NCT04714619 Active not recruiting Drug: CB-103 Advanced Breast Cancer MedSIR|Cellestia Biotech AG May 6 2021 Phase 2
NCT04735367 Recruiting Drug: palbociclib plus letrozole Breast Cancer Pfizer February 3 2021 --

(data from https://clinicaltrials.gov, updated on 2022-01-17)

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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