Thomas Ryckmans

Rapid assessment of a novel series of selective CB2 agonists using parallel synthesis protocols: A Lipophilic Efficiency (LipE) analysis

A series of libraries were designed using the 1-(cyclopropylmethyl)-2-alkyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-5-ium templates 2a-b, and Sulfonamide derivatives 11a-n proved to be potent agonists of the CB(2) receptor. Analysis of the Lipophilic Efficiency (LipE) of potent compounds provided new insight for the design of potent, metabolically stable CB2 agonists.

Design and synthesis of morpholine derivatives. SAR for dual serotonin & noradrenaline reuptake inhibition.

Single enantiomer (SS) and (RR) 2-[(phenoxy)(phenyl)methyl]morpholine derivatives 5, 8-23 are inhibitors of monoamine reuptake. Target compounds were prepared using an enantioselective synthesis employing a highly specific enzyme-catalysed resolution of racemic n-butyl 4-benzylmorpholine-2-carboxylate (26) as the key step. Structure-activity relationships established that serotonin and noradrenaline reuptake inhibition are functions of stereochemistry and aryl/aryloxy ring substitution. Consequently, selective SRI, selective NRI and dual SNRIs were all identified. One of these compounds, a potent and selective dual SNRI, (SS)-5a was selected as a candidate for further pre-clinical evaluation.

Quantitative UPLC-MS/MS analysis of the gut microbial co-metabolites phenylacetylglutamine, 4-cresyl sulphate and hippurate in human urine: INTERMAP Study

The role of the gut microbiome in human health, and non-invasive measurement of gut dysbiosis are of increasing clinical interest. New high-throughput methods are required for the rapid measurement of gut microbial metabolites and to establish reference ranges in human populations. We used ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) -- positive and negative electrospray ionization modes, multiple reaction monitoring transitions -- to simultaneously measure three urinary metabolites (phenylacetylglutamine, 4-cresyl sulphate and hippurate) that are potential biomarkers of gut function, among multi-ethnic US men and women aged 40-59 from the INTERMAP epidemiologic study (n = 2000, two timed 24-hr urine collections/person). Metabolite concentrations were quantified via stable isotope labeled internal standards. The assay was linear in the ranges 1ng/mL (lower limit of quantification) to 1000ng/mL (phenylacetylglutamine and 4-cresyl sulfate) and 3ng/mL to 3000ng/mL (hippurate). These quantitative data provide new urinary reference ranges for population-based human samples: mean (standard deviation) 24-hr urinary excretion for phenylacetylglutamine was: 1283.0 (751.7) μmol/24-hr (men), 1145.9 (635.5) μmol/24-hr (women); for 4-cresyl sulphate, 1002.5 (737.1) μmol/24-hr (men), 1031.8 (687.9) μmol/24-hr (women); for hippurate, 6284.6 (4008.1) μmol/24-hr (men), 4793.0 (3293.3) μmol/24-hr (women). Metabolic profiling by UPLC-MS/MS in a large sample of free-living individuals has provided new data on urinary reference ranges for three urinary microbial co-metabolites, and demonstrates the applicability of this approach to epidemiological investigations.

Design and pharmacological evaluation of PF-4840154, a non-electrophilic reference agonist of the TrpA1 channel.

TrpA1 is an ion channel involved in nociceptive and inflammatory pain. It is implicated in the detection of chemical irritants through covalent binding to a cysteine-rich intracellular region of the protein. While performing an HTS of the Pfizer chemical collection, a class of pyrimidines emerged as a non-reactive, non-covalently binding family of agonists of the rat and human TrpA1 channel. Given the issues identified with the reference agonist Mustard Oil (MO) in screening, a new, non-covalently binding agonist was optimized and proved to be a superior agent to MO for screening purposes. Compound 16a (PF-4840154) is a potent, selective agonist of the rat and human TrpA1 channel and elicited TrpA1-mediated nocifensive behaviour in mouse.

SAR mining and its application to the design of TRPA1 antagonists

Given the large amounts of screening data now available, empirical methods derived from matched-molecular pairs are being used as a means for suggesting bioisosteric replacements to the medicinal chemist. The pairwise analysis of compounds has been extended to the pairwise analysis of series to bring further context to these suggestions. A validation dataset derived from recent literature has been used to demonstrate that, given a series of active compounds, this approach would be expected to predict a more potent compound, if it exists, in around 46% of cases. The approach has been successfully applied to a series of TRPA1 antagonists.

Derivatives of (3S)-N-(biphenyl-2-ylmethyl)pyrrolidin-3-amine as selective noradrenaline reuptake inhibitors: Reducing P-gp mediated efflux by modulation of H-bond acceptor capacity.

Derivatives of (3S)-N-(biphenyl-2-ylmethyl)pyrrolidin-3-amine are disclosed as a new series of noradrenaline reuptake inhibitors (NRI). Carboxamide 9e, carbamate 11b and sulfonamide 13a were identified as potent NRIs with excellent selectivity over SRI and DRI, good in vitro metabolic stability and weak CYP inhibition. Carbamate 11b demonstrated superior transit performance in MDCK-mdr1 cell lines with minimal P-gp efflux which was attributed to reduced HBA capacity of the carbamate group. Evaluation in vivo, in rat microdialysis experiments, showed 11b increased noradrenaline levels by 400% confirming good CNS penetration.

Application of Barluenga Boronic Coupling (BBC) to the Parallel Synthesis of Drug‐like and Drug Fragment‐like Molecules

Library and array synthesis has proven an invaluable tool for medicinal chemists to quickly assess key structure–activity relationships against a biological target. The main requirements for the adoption of a given synthetic protocol are: 1) the availability of a diverse set of monomers (building blocks), 2) the reaction should be adapted to the preparation of drug-like molecules and thus should tolerate a wide range of functional groups, and 3) the process should ideally be airand moisturetolerant. As a consequence, the protocols used for library synthesis have traditionally been biased toward polar bond formation, such as amide couplings. However, emerging C C bond formation methodologies are often crucial to establish new synthetic methods and disconnections, but publications in this field often focus on simplified substrates, yielding products of high lipophilicity (i.e. , high cLog P) and few functionalities such as hydrogen bond donors or acceptors (i.e. , low topological polar surface area (TPSA)). High cLog P and low TPSA values are correlated with a range of preclinical issues such as low solubility, promiscuity, and toxicity, and have emerged as a key descriptors of drug-likeness 3] and drug fragment-likeness. For these reasons, medicinal chemists often find recently published C C bond formation reactions ill-suited to generate new compounds with good drug-like (“rule-of-five”) and drug fragment-like (“rule-ofthree”) properties. In a recent review, MacDonald et al. elegantly demonstrate that there is limited overlap between the “synthetic space” described in recent synthetic communications and the “drug-like space” defined by the “rule-of-five” and related approaches. To assess the diversity of reactions used in parallel chemistry at our Pfizer research facility in Sandwich, we analyzed the protocols used for the preparation of more than 1300 libraries over the last 18 months (2010–2011). The protocols were pooled by bond-type formation (Figure 1). N-Acylation reactions (in which we included amide, sulfonamide, urea, and carbamate formation) accounted for a significant number (30 %) of protocols. C N bond formation (including N-alkylation, N-arylation, and reductive aminations) represented 18 % of protocols. Heterocycle formation accounted for 9 % of protocols, while C C bond formation (which includes Suzuki and Stille couplings) was only used in 8 % of protocols. The category “other” (31 %) captures both seldom-used reactions and multistep reactions: for example, a combination of the above protocols with protection/deprotection steps. These results are roughly comparable to data gathered from the medicinal chemistry literature, which show that C C bond formation reactions account for ~11 % of the methods used to prepare drug candidates. Interestingly, the overall success rates of C C bond formation protocols (67 % success rate) used in our parallel synthesis were similar to N-acylation (73 % success rate) and C N (66 % success rate) bond formation protocols. Assuming all protocols yield compounds with similar drug-like properties, these results demonstrate that although robust C C bond formation protocols are now available, this type of reaction is still underused by medicinal chemists for the preparation of library compounds. In this context, the Barluenga boronic coupling (BBC) recently caught our attention. This novel reaction involves the formation of a C C bond between a diazo compound (generated in situ from a para-toluenesulfonyl (tosyl) hydrazone) and a boronic acid through a reductive coupling (Scheme 1). Of special interest to us was the fact that a small number of examples (four out of 27) included polar functional groups such as anilinic NH2 and N H heterocycles, and the synthesis of a single small, highly polar drug-like molecule (compound 1) was indeed exemplified. The average isolated yields are consistently high (>80 %) with only two examples <60 % (two of 27). Given the ease of preparation of tosylhydrazones from a Figure 1. Distribution of synthetic protocols used for the synthesis of over 1300 libraries included in this survey, representing ~90 000 compounds successfully prepared; overall success rate: 60 %.

TAK1 Inhibition in the DFG-Out Conformation

The first example of an inhibitor of the kinase TAK1 that binds in the DFG‐out conformation is disclosed. These preliminary studies used kinase‐targeted screening and structure‐based drug design to create a molecule with dual pharmacological inhibition of p38 and TAK1 that demonstrated significant activity in a cell‐based, anti‐inflammatory assay.

Chapter 6 Advances in Vasopressin Receptor Agonists and Antagonists

Publisher Summary This chapter discusses the recent advances in the development of non-peptidic vasopressin receptor ligands, focusing on new series, structure–activity relationship (SAR), and preclinical data. Arginine vasopressin (AVP) is a 9–amino-acid cyclic peptide that exerts its effect through the V1a, V1b, V2, and oxytocin (OT) family of G-protein- coupled receptors (GPCRs). There is growing evidence that AVP, through its action at V1a and V1b receptors, is involved in the modulation of several higher brain functions such as response to stress, mood, memory formation, aggressivity, and sociality. The chapter examines V2 receptor antagonists and agonists for the modulation of renal function and cardiovascular conditions. V1a receptor antagonists are being actively investigated for indications such as dysmenorrhea, given the unmet medical need and the large patient population. On the contrary, the involvement of the V1a and V1b receptors in depression, anxiety and stress disorders has been clearly demonstrated in preclinical models. However, the discovery of an orally bioavailable, well-tolerated, and central nervous system (CNS)-penetrant antagonist of these receptors is still a challenge.

[4-(Phenoxy) pyridin-3-yl] methylamines: A new class of selective noradrenaline reuptake inhibitors

[4-(Phenoxy)pyridine-3-yl]methylamines are disclosed as a new series of selective noradrenaline reuptake inhibitors (NRI). Structure-activity relationships established that potent NRI activity could be achieved by appropriate substitution at the 2-position of the phenoxy ring. Compound 31 demonstrated potent NRI activity combined with good selectivity over serotonin and dopamine reuptake and no significant off-target pharmacology.