依替米貝課件

1、The discovery and synthesis of ezetimibeCONTENTINTRODUCTIONTHE DISCOVERY OF EZETIMIBETHE SYNTHESIS OF EZETIMIBEHigh blood-cholesterol levels constitute a major risk factor for cardiovascular disease, the leading cause of death in the Western industrialized world.The total blood cholesterol level is

2、primarily regulated by two complementary mechanisms: (1) cholesterol biosynthesis in the liver and (2) absorption of dietary cholesterol in the small intestine. Since their introduction in the late 1980s, statins have by far become the predominant class of current lipid-lowering drugs (96% of total

3、sales in 2001). Statins inhibit HMG-CoA reductase, the enzyme that catalyzes the rate-limiting step of cholesterol biosynthesis in the liver.However, the patient response to statins varies greatly, with half of all patients on statin therapies failing to reach their cholesterol goals. Ezetimibe, whi

4、ch was approved in late 2002 for use either alone and in combination with a statin, is the only example to date of a drug that involves inhibition of intestinal cholesterol absorption.prefaceINTRODUCTIONTHE DISCOVERY OF EZETIMIBETHE SYNTHESIS OF EZETIMIBEzetia(Ezetimibe) (1-(4-fluorophenyl)-(3R)-3-(

5、4-fluorophenyl)-(3S)-hydroxypropyl-(4S)-(4-hydroxyphenyl)-2-azetidinoneSCH 58235(found by Merck and Schering-Plough)2002 published in Germany, 2007 in Chinafirst of the cholesterol absorption inhibitors, inhibit the absorption of biliary and dietary cholesterol from the small intestine without affec

6、ting the absorption of fat-soluble vitamins, triglycerides or bile acidsEzetimibe reduces the small intestinal enterocyte uptake and absorption of cholesterol by binding to Niemann-Pick C1 Like 1 (NPC1L1)1, introductionmetalbolism of ezetimibeFollowing oral administration, ezetimibe is rapidly absor

7、bed in the intestine and extensively metabolised (80%) to the pharmacologically active ezetimibe-glucuronide in the intestine and liver.Total ezetimibe (sum of parent ezetimibe plus ezetimibe-glucuronide) concentrations reach a maximum 1-2 hours post-administration, followed by enterohepatic recycli

8、ng and slow elimination.The estimated terminal half-life of ezetimibe and ezetimibe-glucuronide is approximately 22 hours.lack of clinically relevant interactions between ezetimibe and a variety of drugsUGT1A1,UGT13,UGT2B15Biotransformation pathway for ezetimibe in humans and animals cholesterol met

9、abolism2D view of the NPC1 topologyHypothetical NPC1 membrane arrangement. Basedon the topology of NPC1 and its similarity to prokaryotic molecular pumps, NPC1 may act in a similar manner by forming a channel within mammalian membranes. Cylinders denote NPC1 transmembrane domains. Roman numerals den

10、ote the number of each transmembrane domainPredicted loops are labeled throughout the protein sequence (AN). The pentahelical SSD is highlighted in purple. Key residues for 3HAS binding (Phe/Tyr-532 and Met/Ile-543) and sequence variants found exclusively in low (red circle) or high (lightblue circl

11、e) absorbers of cholesterol as identified in the Dallas Heart study are shown. The hotspot of hypoabsorption polymorphisms adjacent to key residues determining 3HAS binding are highlighted (red triangle).model of NPC1L1-dependent cholesterol uptake A working model of NPC1L1-mediated cholesterol upta

12、ke and intracellular transport. In PM, NPC1L1 and flotillins collaborate with each other to form cholesterol-rich microdomains, which is subsequently coated by clathrin/AP2 complex and subjected to endocytosis. The endocytic vesicles are then transported to ERC along the microfilaments. Finally,chol

13、esterol is released from ERC and transported to ER and other membranes via unknown mechanism. When the intracellular cholesterol level is low, the Cdc42 is activated andbinds to NPC1L1, promoting the recruitment of Myosin Vb and actin. Meanwhile, Cdc42 downstream effectors N-WASP and Arp2/3 are acti

14、vated to initiate actin polymerization near NPC1L1-vesicles and contribute to the transport of NPC1L1flotillin complex to PM. PM, plasma membrane; ERC, endocytic recycling compartment.SAR of ezetimibeThe azetidinone ring is requiredThe presence of a 4-methoxyphenyl or similar hydrogen bonding moiety

15、 and proper absolute stereo chemistry at C-4 are both criticalAn N-aryl group is required, but there is considerable tolerance for substitution on the phenyl ringThe phenylalkyl group at C-3 and monosus-btitution at C-3 are also important, but the geometry of the groups at C-3 is less critical.INTRO

16、DUCTIONTHE DISCOVERY OF EZETIMIBETHE SYNTHESIS OF EZETIMIBE2, the discovery of ezetimibeThe discovery program that ultimately led to ezetimibebegan as a program to discover novel ACAT (acyl-coenzyme A cholesterol acyltransferase) inhibitors.Profile of 14 in cholesterol-fed animal models In addition

17、to blocking accumulation of hepatic cholesteryl esters in the hamster, 14 reduces serum cholesterol levels in the cholesterol-fed rat, dog, and monkey. Of particular significance is the activity in the cholesterol-fed rhesus monkey. Effect of 14 in the cholesterol-fed rhesus monkeyControl animals sh

18、ow a profound hypercholesterolemia after 3 weeks that is completely blocked by 1 mg/kg doseof 14 admininistered in the diet. When the control animals are then treated with 1 mg/kg of 14, their cholesterol levels return to nearly baseline within 1 week, while withdrawal of drug causes a gradual rise

19、in cholesterol levels over the same time period.While these data provided encouragement, the absence of an in vitro assay made it difficult to separate potential effects on intrinsic potency from effects on pharmacokinetics.To address this latter issue, Van Heek and colleagues devised a unique exper

20、imental protocol designed to determine if there were active metabolites and how they contributed to the overall in vivo profile of 14.In this way, both the pharmacological effects as well as the disposition of drug could be measured in a single experiment by following counts of 14C and 3H, respectiv

21、ely. Furthermore, because of the bile duct diversion, the pharmacological effects reflectedprimarily the activity of the species being dosed and not the effects of any subsequently produced metabolites.resultthe metabolite bile was clearly more effective and reduced 14C levels comparably to the pare

22、nt compound 14 in intact animalsConsistent with this, when 3H-14 bile was dosed, the majority of the tritium counts were recovered in the bile.However, when 3H metabolite bile was dosed, the majority of the counts remained in the intestinal wall and lumen.These data strongly suggested that formation

23、 of one or more active metabolites plays a significant role in the in vivo activity of 14.These data suggest not only that are there active metabolites but that these metabolites localize at the putative site of action more efficiently than 14 itself.To address this, metabolite bile was fractionated

24、 by HPLC and each fraction was evaluatedthese data showed that the bulk of the activity resided in fraction 6, and subsequent analysis showed that this fraction was composed primarily of the glucuronide of compound 19, a phenolic metabolite of 14In total, these data strongly suggested that much of t

25、he in vivo activity of 14 was due to the formation of 19. Furthermore, they suggested that metabolism of 14 to 19 helped to localize the compound in the intestines at the putative site of action of the compound.Rosenblum et al. prepared authentic samples of a number of known or putative metabolites

26、that were evaluated for activity in the cholesterol-fed hamsterBoth phenol 20 and bisphenol 21 showed substantial activity in the cholesterol-fed hamster, although neither was more active than 14 or 19, suggesting that metabolism on the N-aryl moiety was not required for activity.phenol 22 was less active than 14, suggesting that this route of metabolism mig