MC: Gonadal Hormones & Inhibitors Required reading W & G 12th Ed, page 819-864 Reference Foye's 7th Ed, Page 1346-1434 PHRM 614-P2 Shengquan Liu Ph. D 12-06-18, Th, AM, Rm 170 File name: EPA_181206aTh/12-03 1 MoA Review (14 Classes & 32 Drugs) Female: Ovary Male: Testis Antagonist: ganirelix & cetrorelix “-relix” ↓ ovarian hyperstimulation Agonist: “-relix” ↓ PC Leuprolide ↓ FSH/LH ↓ E/A (-) E® ↑ FSH/LH (+) ovulation ↓ FSH/LH (-) P450 & (-) E/A ® (-) P450 ↓ [EPA] ↓ PC (-) P450 & E/A® ↓ BPH/alopecia ↓ E®+ BC 5-1: 5-3: 5-1: ↓ PC ↓ E®+ BC 5-3: (-) A/M® ↓ hirsutism 2 Learning Objectives: Chemical Structures 1. Biosynthesis & metabolism of 3 natural sex hormones (endogenous ligands, E, P & T) – Native hormones are orally inactive & short-lived rapid metabolism ↓ F/t1/2/DoA (-) metabolism ↑ F/t1/2/DoA new drug designs 2. Metabolism of major drugs & its relations to 1. Bioavailability, DoA & SAR 2. Prodrugs 3. Pharmacophore & SAR related to 1. MoA/site (tissues) of action, indication & SEs 2. Potency/selectivity (agonists & antagonists) 3. Oral activity & DoA 4. Recognize chemical structures of major drugs – structure ↔ name ↔ drug classification ↔ MoA ↔ indication/SE drug selection & clinical decision 3 Gonadal Hormones & Inhibitors (32): Outline 1. Ovarian hormones (“female sex hormones”) 1. Estrogens & antiestrogens ↑ or ↓ E action respectively 1. Estradiol (E2), ethinyl estradiol & other estrogens (+) E® 2. Antiestrogens (±) or (-) E®; AIs (-) aromatase ↓ [E] 1. SERMs (tamoxifen) (±) E® (±) or (-) E® ↓ E®+ BC 2. Pure antagonist: fulvestrant (-) E® 3. Aromatase inhibitors (AIs, anastrozole) (-) aromatase ↓ [E] ↓ E®+ BC 2. Progestins & antiprogestins ↑ or ↓ P action respectively 1. Progesterone (“pregnancy hormone”), norgestrel & its analogs (+) P® 2. Antiprogestins (mifepristone) (-) P® abortion 2. Testis hormones (“male sex hormone”) – Androgens & antiandrogens ↑ or ↓ A action respectively 1. Testosterone (T) & its analogs (+) A® ↑ A action – 5a-dihydrotestosterone (DHT, a more potent metabolite) 2. Antiandrogens ↓ A action – A® antagonists (flutamide) (-) A® ↓ PC – 5a-Reductase inhibitors (finasteride*) ↓ [DHT] ↓ BPH/hirsutism – Synthesis inhibitors (ketoconazole) (-) CYP ↓ [E, P or A] 4 Biosynthesis of Sex Hormones Acetate What is MoA of: 1. Ketoconazole 2. Anastrozole 3. Finasteride (DHEA) 5a-reductase DHT Hormonal Control of the Female Reproductive System 6 1. Natural Sex Hormones (Remember) Steroids that are necessary for reproduction in females & males & affect the development of 2nd sex characteristics – Progesterone (P) precursor to testosterone, estrogens, cortisol & aldosterone – Testosterone (T) Precursors of estrogens T 5a-Dihydrotestosterone (DHT, 10 X more active than T) – Estradiol (E2) 7 1. Natural Ovarian (Female) Hormones Structure 18 Cs 21 Cs 3-,17-di-OH (E2) 17-acetyl Aromatic A ring 3-keto/4-ene A ring Class Estrogens Progestins Released by Follicle in ovary Corpus luteum in ovary Functions 2nd sex characteristics For pregnancy Uses hypoGonad/HRT, OC, osteoporosis HRT/infertility/OC Effects on heart ↓ LDL, ↑ HDL/TG/Thrombosis* ↑ LDL/TG, ↓ HDL, Risk of BC or ↑ ↓ endometrial CA Higher concentration in females * Deep Vein Thrombosis (DVT). 8 1. Ovarian (Female) Hormones: Estrogens Nature Reviews Endocrinology 7, 715-726 (December 2011) 9 3 Endogenous Estrogens: Ph, 3- & 17-di-O(H) # of OH FG 1 2 3 Potency 1 10 (most potent) very weak In circulation (%) 60-80 10-20 10-20 In urine Conjugates Uses HRT HRT HRT (rare) An extract of ovaries can produce estrus (1932) All are 18 Cs, 3-OH & 17-OH (or keto), phenolic A ring (for binding w/ E®) Uses: estrogen component in HRT Many phenols are estrogenic 10 1.1. Metabolism in Liver F-: Major Pathway 16a-hydroxylation & 17-OH oxidation in D ring – Minor pathway: 2-, or 4-hydroxylation 2- or 4-O-methylation (COMT) Metabolism mainly in liver & largely excreted as glucuronide & sulfate conjugates in urine or bile (enterohepatic circulation) SEs: ↑ clotting factor synthesis To avoid these SEs, use vaginal, transdermal or injection form11 1.1. Steroidal Estrogens: Estradiol (3,17-OH) Uses: hypogonadism/HRT & contraceptives F-/PO+ formulations: – Micronized form (PO) for menopause ↑ absorption – I.M. injection st – Transdermal patch for menopause No 1 pass metabolism Less DVT risk – Vaginal cream/ring Lipophilic high protein binding High affinity for E®s high potency parenterally, but Poor oral bioavailability (F ≈ 5%) due to: – 3-OH-conjugation in intestine & metabolic oxidation of 17-OH in liver ↓ oral activity & elimination t1/2 20 min. Can we design longer-acting or more orally active drugs & how ? Think about 3 &17-OH – 3 methods 12 1.1. 17b-Estradiol Esters (IM) ↑ DoA 17-Ester prodrug IM (in oil) for long-term therapy Slowly hydrolyzed to estradiol in vivo long-acting – ↑ R size ↑ log P & more hindered ↓ absorption rate ↑ DoA – Tx: hypogonadism in girls or women 13 Ethinyl Estradiol* (EE, 17a-C≡CH PO, OCs) (-) metabolic inactivation ↑ F/t1/2/DoA – 17b-OH metabolism was blocked & permanently protected w/ 17a-ethynyl group – ↑ potency (200 X more potent than estradiol) Use: Combined oral contraceptive (COC)/HRT14 Ethinyl Estradiol (EE) Metabolism: 2, 3-OMe Use: COC – Like many other OCs, 3A4 substrate DDIs – 3-O-glucuronide & -sulfate metabolites (inactive) Why some broad-spectrum antibiotics ↓ OC efficacy? – 3-O-methyl ether of EE = Mestranol 15 Mestranol (3-OCH3, COC) Ethinyl Estradiol A prodrug of EE – Synthetic estrogens, no 3-O-conjugation ↑ DoA Rapidly bioactived mainly to EE by hepatic O-demethylation following PO Both mestranol & ethinyl estradiol are used primarily in COC Please compare these 2 drugs Can you use mestranol locally? 16 1.1. Conjugated Estrogens: Water-Soluble Equilin & equilenin (equine = horse) – Obtained from Pregnant mares’ urine as “Premarin* or conjugated estrogen for HRT Premarin: a mixture of sodium estrone sulfate, sodium equilin sulfate & sulfate conjugates of some metabolites Excreted in urine as sodium sulfate conjugates – Water-soluble metabolites of natural estrogens Conjugated Estrogens USP is a mixture of sodium salts of sulfate esters of estradiol derived from equine urine or prepared synthetically from estrone & equilin 17 1.1. Nonsteroidal Estrogens: Stilbenes The steroid nucleus is NOT required for activity (B & C rings can open) Some stilbene (diphenylethylene) drugs – trans isomers are more stable & potent than cis isomers Diethylstilbestrol (DES) – Never used in pregnancy, removed from US, only used in veterinary med now 18 1.1. SAR : General Important FGs 1. Aromatic A ring 1. Planar hydrophobic scaffold 2. Steroids w/ an aromatic A ring lack affinity to other steroid hormone ®s 2. 3 & 17b-OH (2 HBDs) 3. Distance between 3-OH & 17-OH groups ≈ 10.3-12.1 Å 19 1.1. Steroid Hormone: MOA 2 HBDs 20 1.1. SAR : Substituents Aromatic A ring, 3 & 17-OH are important SAR is often in PCOA exam! 21 1.1. Estrogens: Same MoA & Different PK Uses \ Drugs E2 Estrogen esters EE: Orally active Conjugates (IM) estrogens equine estrogens PO Poor oral activity ↑ DoA ↑ F/t1/2/DoA /potency Retain some activity Short t1/2/DOA (e.g. equilin sodium sulfate) Metabolism 1st-pass metabolism Slowly hydrolyzed to E2 Resistance to 1st-pass Conjugation hepatic metabolism Metabolic conjugates retain some activity (e.g. equilin sodium sulfate) Hypogonadism + HRT E1, 2 & 3 ++ ++ OC +++ Potency ++ ++++ 200X vs. E2 + 22 Estrogen: Estradiol: MoA Rapid uptake & retained more in breast, uterus & vagina 2 main estrogen ®s – ERa: mainly in female reproductive tract & mammary glands – ERb: mainly in vascular endothelial cells, bone & male prostate tissues – Estradiol has similar affinities for both ERs Certain non-steroidal estrogens & antiestrogens are different ® binding estradiol-® complex – Conformation change of the ®s homo or heterodimers – Interacts w/ estrogen response elements (ERE) of cellular DNA – DNA transcription mRNA protein synthesis Regulation of gene expression & protein synthesis 23 Estrogens: Estradiol & Breast Cancers (FYI) (+) gene expression ↑ production of several proteins – Intracellular proteins important for breast cell function & growth Enzymes needed for DNA synthesis – DNA polymerase, dihydrofolate reductase …… – Proteins that influence tumor growth & metastasis Transforming growth factor-a (TGFa) & TGFb Insulin-like growth factor I (IGF-I) Cathepsin D protein: (+) breast cancer cell metastasis So, ↑↑ estrogens can (+) proliferation of breast cells & causes estrogen-dependent breast cancer (ER+ BC) – ↑ growth of hormone-dependent mammary carcinoma 24 2.2. Antiestrogens: BCs & Ovarian Cancers Estrogen is a growth factor for ER+ BC cells (-) estrogen action ↓ ER+ BC Tx: ER+ BC & infertility 3 groups 1. Triphenylethylene antiestrogens (±) ERs • Selective estrogen receptor modulators (SERMs) • Act as estrogen agonist in some tissues, partial agonists or estrogen antagonists in other tissues tissue-specific 2. Pure antagonists 3. (-) aromatase ↓ estrogen (E) biosynthesis ↓ [E] ↓ BC 25 SERMs: Triphenylethylenes Antiestrogens Tamoxifen: High affinity for ERs Produce antiestrogen-® complexes that – Prevent translocation of E-® complex into nucleus of target cells – (-) binding of E-® complex to estrogen response elements (ERE) of cellular DNA Toremifene (Cl): similar structure/property/indication & toxicity to tamoxifen, but – Beneficial effects on bone, CV & HDL 26 1st G. SERM (Triphenylethylenes): Tamoxifen* Antagonist on breasts prevent or treat E®+ BC Antagonist on CNS hot flash Agonist on