Structure-activity relationships of 1-alkyl-5-(3,4-dichlorophenyl)- 5-[2-[(3-substituted)-1-azetidinyl]ethyl]-2-piperidones. 1. Selective antagonists of the neurokinin-2 receptor.
The design, synthesis, and pharmacological evaluation of a novel class of neurokinin-2 (NK2) antagonists 1-alkyl-5-(3,4-dichlorophenyl)-5-[2-[(3-substituted)-1-azetidinyl]ethyl]-2-piperidones (5-44) are described. These compounds are formally derived from 2 by incorporating the metabolically vulnerable N-methylamide function into a more stable six-membered ring lactam 4, resulting in increased stability in human liver microsome (HLM) preparations relative to 2 (T1/2(HLM) of 30 min vs <10 min for 2). This series was further optimized by replacing the 4,4-disubstituted piperidine functionality found in 4 with simple 3-substituted azetidines. This series, exemplified by 1-benzyl-5-(3,4-dichlorophenyl)-5-[2-[3-(4-morpholinyl)-1-azetidinyl]ethyl]-2-piperidone 5, was found to possess excellent functional potency for the NK2 receptor in the Rabbit pulmonary artery (RPA) assay (pA2 = 9.3) and increased in vitro metabolic stability (T1/2(HLM) = 70 min) relative to 4. Metabolic route identification studies revealed that N-benzyl oxidation was a major route in this relatively lipophilic lead (log D = 3.2). Further exploration of the N-lactam substituent SAR targeting reduced lipophilicity to attenuate P-450 metabolism revealed that incorporation of a cyclopropylmethyl group in this region of the molecule gave a balance of good potency and high metabolic stability. For example, the significantly less lipophilic analogue 29 (log D = 2.3) possessed both good functional potency (RPA, pA2 = 8.1) and high in vitro metabolic stability (T1/2(HLM) = 120 min). Optimization in this N-cyclopropylmethyllactam series by modification of the nature of the azetidine 3-substituent as a strategy to further increase potency and moderate log D led to the identification of sulfamide analogue 33, which possessed both excellent metabolic stability in vitro (T1/2(HLM) >120 min) and high potency in both RPA (pA2 = 8.9) and human bladder smooth muscle (pK(b) = 8.9) functional assays. In addition, NK2 antagonist 33 (IC50 = 4 nM) showed excellent selectivity over both the related human neurokinin receptors h-NK1 (IC50 = 7.9 microM) and h-NK3 (IC50 = 1.8 microM) in radioligand binding studies.
MacKenzie
A Roderick
AR
Department of Discovery Chemistry, Pfizer Global Research and Development, Sandwich, Kent CT13 9NJ, UK.
Marchington
Allan P
AP
Middleton
Donald S
DS
Newman
Sandra D
SD
Jones
Barry C
BC
D000818:Animals; D001384:Azetidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D016466:CHO Cells; D006224:Cricetinae; D004355:Drug Stability; D006801:Humans; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010881:Piperidones / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D011869:Radioligand Assay; D018041:Receptors, Neurokinin-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018042:Receptors, Neurokinin-3 / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
C416764:4-(1-(2-(1-(cyclopropylmethyl)-3-(3,4-dichlorophenyl)-6-oxo-3-piperidyl)ethyl)azetidin-3-yl)-1-piperazine sulfamide; D001384:Azetidines; D010879:Piperazines; D010881:Piperidones; D018041:Receptors, Neurokinin-2; D018042:Receptors, Neurokinin-3