Non-benzimidazole containing inhibitors of respiratory syncytial virus.

Several non-benzimidazole containing inhibitors of respiratory syncytial virus are described. Core template modification, analysis of antiviral activity, physicochemistry and optimisation of properties led to the thiazole-imidazole 13, that showed a good potency and pharmacokinetic profile in the rat.

An in situ oxidation strategy towards overcoming hERG affinity.

In an effort to overcome hERG affinity with a lead compound, several S-oxide and N-oxide analogues were synthesised with a much improved hERG profile but low in vivo absorption. This led to the implementation of an in situ oxidation strategy wherein a sulfide was dosed orally and systemic levels of the corresponding sulfoxide and sulfone were monitored. SAR and pharmacokinetic data to support this as a possible strategy are presented, although ultimately the approach was shown not to be suitable due to very low levels of active circulating metabolites.

1-Amido-1-phenyl-3-piperidinylbutanes - CCR5 antagonists for the treatment of HIV. Part 1.

The development of a new class of CCR5 antagonist replacing the tropane core of maraviroc by piperidine with a branched N-substituent is described. Compound 15h shows good whole cell antiviral activity together with microsomal stability and only weak activity at the hERG ion channel.

1-Amido-1-phenyl-3-piperidinylbutanes--CCR5 antagonists for the treatment of HIV: part 2.

Optimisation of a series of 4-piperidinyltriazoles led to the identification of compound 28a which showed good whole cell antiviral activity, excellent selectivity over the hERG ion channel and complete oral absorption.

The design and discovery of novel amide CCR5 antagonists.

The synthesis of a range of novel amine-containing structures and their primary potency as inhibitors of HIV-1 fusion via blocking of the CCR5 receptor is described. The development of the medicinal chemistry strategy and SAR's which led to the identification of the piperidine amide compounds 33 and 36 as excellent leads for further evaluation is described, along with key physicochemical data which highlighted their lead potential.

Discovery of a small molecule inhibitor through interference with the gp120-CD4 interaction.

A series of piperazine derivatives were designed and synthesised as gp120-CD4 inhibitors. SAR studies led to the discovery of potent inhibitors in a cell based anti viral assay represented by compounds 9 and 28. The rat pharmacokinetic and antiviral profiles of selected compounds are also presented.

Design and optimisation of potent gp120-CD4 inhibitors.

The synthesis and structure-activity relationship of a series of novel gp120-CD4 inhibitors are described. Pharmacokinetic studies and antiviral spectrum assessment of lead compounds led to the identification of compound 36, a potent gp120-CD4 inhibitor which exhibited antiviral potency across a spectrum of 25 clade B isolates.

Designing rapid onset selective serotonin re-uptake inhibitors. 2: structure-activity relationships of substituted (aryl)benzylamines.

A series of substituted benzylamines 2-48 were prepared as part of a strategy to identify structurally differentiated and synthetically more accessible selective serotonin reuptake inhibitors, relative to clinical candidate 1. In particular, 44 and 48; demonstrated low nanomolar potency and good selectivity, in a structurally simplified template and, in vivo, very low Vdu, significantly lower than l, and a more rapid T(max), consistent with our clinical objectives.

Designing rapid onset selective serotonin re-uptake inhibitors. Part 3: Site-directed metabolism as a strategy to avoid active circulating metabolites: structure-activity relationships of (thioalkyl)phenoxy benzylamines.

A series of thio-alkyl containing diphenylethers were designed and evaluated, as a strategy to competitively direct metabolism away from unwanted amine N-demethylation and deliver a pharmacologically inactive S-oxide metabolite. Overall, sulfonamide 20 was found to possess the best balance of target pharmacology, pharmacokinetics and metabolism profile.

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.

Synthesis and biological evaluation of acyclic phosphonic acid nucleoside derivatives.

As part of a project to generate a library of nucleosides as potential antiviral agents, a small subset of novel acyclic phosphonic acid nucleosides was prepared. Practical synthetic routes are described for three targets, which were then tested against HIV, hepatitis C virus (HCV), and Dengue virus.

Comparison of the non-nucleoside reverse transcriptase inhibitor lersivirine with its pyrazole and imidazole isomers.

Lersivirine is a potent non-nucleoside reverse transcriptase inhibitor with exceptional mutant resilience. Here, we compare the pharmacological and pharmacokinetic profile of lersivirine with its pyrazole and imidazole isomers and briefly explore the profile of these series. This work establishes lersivirine as the outstanding molecule in this set.

An imidazopiperidine series of CCR5 antagonists for the treatment of HIV: the discovery of N-{(1S)-1-(3-fluorophenyl)-3-[(3-endo)-3-(5-isobutyryl-2-methyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-1-yl)-8-azabicyclo[3.2.1]oct-8-yl]propyl}acetamide (PF-232798).

Preventing entry of HIV into human host cells has emerged as an attractive approach to controlling viral replication. Maraviroc 1 is an approved antagonist of the human CCR5 receptor which prevents the entry of HIV. Herein, we report the design and discovery of a series of imidazopiperidine CCR5 antagonists which retain the attractive antiviral profile and window over hERG activity of maraviroc 1, combined with improved absorption profiles in rat and dog. Furthermore, this series of compounds has been shown to retain activity against a laboratory generated maraviroc-resistant HIV-1 strain, which indicates an alternative resistance profile to that of maraviroc 1. Compound 41f (PF-232798) was selected as a clinical candidate from the imidazopiperidine series and is currently in phase II clinical trials.

Inhalation by design: novel tertiary amine muscarinic M3 receptor antagonists with slow off-rate binding kinetics for inhaled once-daily treatment of chronic obstructive pulmonary disease.

A novel tertiary amine series of potent muscarinic M(3) receptor antagonists are described that exhibit potential as inhaled long-acting bronchodilators for the treatment of chronic obstructive pulmonary disease. Geminal dimethyl functionality present in this series of compounds confers very long dissociative half-life (slow off-rate) from the M(3) receptor that mediates very long-lasting smooth muscle relaxation in guinea pig tracheal strips. Optimization of pharmacokinetic properties was achieved by combining rapid oxidative clearance with targeted introduction of a phenolic moiety to secure rapid glucuronidation. Together, these attributes minimize systemic exposure following inhalation, mitigate potential drug-drug interactions, and reduce systemically mediated adverse events. Compound 47 (PF-3635659) is identified as a Phase II clinical candidate from this series with in vivo duration of action studies confirming its potential for once-daily use in humans.

Novel indazole non-nucleoside reverse transcriptase inhibitors using molecular hybridization based on crystallographic overlays.

A major problem associated with non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment of HIV is their lack of resilience to mutations in the reverse transcriptase (RT) enzyme. Using structural overlays of the known inhibitors efavirenz and capravirine complexed in RT as a starting point, and structure-based drug design techniques, we have created a novel series of indazole NNRTIs that possess excellent metabolic stability and mutant resilience.

Optimization of 5-aryloxyimidazole non-nucleoside reverse transcriptase inhibitors.

A major problem associated with non-nucleoside reverse transcriptase inhibitors (NNRTIs) for the treatment of HIV is their vulnerability to mutations in the allosteric binding site of reverse transcriptase that can result in the development of a resistant virus. Herein we present the optimization of a series of 5-aryloxy imidazoles, which possess a balanced pharmacological profile against both wild-type enzyme and the clinically relevant mutations K103N and Y181C. Subtle structural changes were used to probe structure-activity relationships relating to both potency and metabolic stability, which led to an imidazole derivative with an impressive overall profile.

Novel selective inhibitors of neutral endopeptidase for the treatment of female sexual arousal disorder.

A series of substituted glutaramides were synthesised using Candoxatrilat 1 as a lead and evaluated for potency against neutral endopeptidase (NEP) as a potential treatment for female sexual arousal disorder (FSAD). In this paper, we describe studies in which we were able to increase NEP activity substantially over the levels reported for previous compounds from this programme by appropriate substitution in both the P(1)(') and P(2)(') regions. Optimisation led to the 4-chlorophenpropylamide S-30 which was selected as a candidate for further study.

Highly potent and selective zwitterionic agonists of the delta-opioid receptor. Part 1.

A series of zwitterionic delta-opioid agonists, with targeted physicochemistry, as a strategy to limit potential for CNS exposure, were prepared. These agents were found to possess exquisite potency and selectivity over mu and kappa-opiate activity. Furthermore, analogue 3a was found to display restricted CNS exposure, as evidenced by its inactivity in a rodent hyperlocomotion assay of central opiate activity. Dog pharmacokinetic studies on 3a indicated encouraging oral bioavailability.

Designing rapid onset selective serotonin re-uptake inhibitors. Part 1: Structure-activity relationships of substituted (1S,4S)-4-(3,4-dichlorophenyl)-N-methyl-1,2,3,4-tetrahydro-1-naphthaleneamine.

A series of sertraline analogues 4-39 which possess polar groups on the fused tetrahydronaphthalene ring, targeting reduced V(d) as a strategy to reduce T(max) and increase rate of elevation of central 5-HT levels, were prepared. These studies led to the successful identification of 22a, which demonstrated equivalent pharmacology and metabolic stability to 1, but which possessed greatly reduced V(d) leading to significantly shorter T(max), in rat pharmacokinetic studies.