Летрозол

Описание

Letrozole, also known as Femara, is an orally active aromatase inhibitor that works by competitively inhibiting aromatase. This inhibition prevents the conversion of androgens to estrogen (estrogen stimulates breast tissues and breast cancer reoccurrence) and gonadal steroidogenesis. It can be used for the treatment of breast cancer that is hormonally-responsive or has an unknown receptor status in postmenopausal women. Besides this, Letrozole also has some off-label use such as ovarian stimulation, pretreatment of termination of pregnancy, treatment of gynecomastia, treatment of endometriosis, and promoting spermatogenesis for male patients of nonobstructive azoospermia.

Химические свойства

white to light yellow crystal

Использование

Letrozole has been used:

• in organoid growth assay to determine its inhibitory capacity(48)
• to investigate steroid receptor coactivator-1 (SRC-1) mediated endogenous estrogen regulation of hippocampal PSD-95(49)
• to determine its effects on tumor-induced hyperalgesia(50)
• for hormonal manipulation in rats(51)
• to study its effects on lipocalin-2 (Lcn2)(52)
• to determine its effects on mechanical hyperalgesia and aromatase expression(53)

Общее описание

Letrozole, 4,4'-(1H-1,2,4-triazol-1-ylmethylene)dibenzonitrile (Femara), is used for most of thesame indications as anastrozole. It reduces concentrations ofestrogens by 75% to 95%, with maximal suppressionachieved within 2 to 3 days. Letrozole is specific for aromataseinhibition, with no additional effects on adrenal corticoidbiosynthesis. CYPs 3A4 and 2A6 are involved in themetabolism of letrozole to the major carbinol metabolite,which is inactive. The loss of the triazole ring, which is involvedin coordination of the heme iron, would explain theloss of activity. Letrozole strongly inhibits CYP2A6 invitro, with moderate inhibition of CYP2C19. The effect ofthis in vitro inhibition on the pharmacokinetics of coadministereddrugs is unknown. Tamoxifen reduces the levels ofletrozole significantly if they are used together, so combinationtreatment with these agents is not recommended.

Биологическая активность

Letrozole is a potent, cell-permeable inhibitor of aromatase (IC50 = 2 nM). It inhibits proliferation of estrogen receptor-positive (ER+) MCF-7 cells when used alone at concentrations ranging from 0.1 to 100 nM and when used at a concentration of 10 nM in combination with testosterone or 4-androstene-3,17-dione. It also reduces matrix metalloproteinase-2 (MMP-2) and MMP-9 levels in MCF-7 cells when used at a concentration of 10 nM. Letrozole (10 μg per day) reduces tumor growth in an MCF-7Ca ovariectomized-mouse xenograft model. Formulations containing letrozole have been used in the treatment of postmenopausal breast cancer.

Механизм действия

Inhibition of arom atase by letrazole is competitive and highly specific , with no effect on enzymes that are responsible for the production of glucocorticosteroids and mineralocorticosteroids. This agent is significantly more effective than tamoxifen in treating horm one-dependent cancer.

Клиническое использование

Femara was launched in France and the UK for second-line treatment of advanced breast cancer. Letrazole can be synthesized in two steps from 4- bromomethyl-benzonitrile with 1,2,4-triazole and is a third generation aromatase inhibitor. It is a highly specific inhibitor of P450_arom which prevents the conversion of androstenedione to estrone. The reduction of plasma estrogen was immediate and long lasting. This is accomplished with no inhibition of other steroid biosynthesis making it the most selective aromatase inhibitor tested. Letrazole has remarkable antitumor activity, is well tolerated and has no toxic side effects. It is 10,000 times more potent than aminoglutethimide, in vivo, the first well established aromatase inhibitor.

использованная литература

https://www.drugbank.ca/drugs/DB01006
https://en.wikipedia.org/wiki/Letrozole