Lipophilic Pocket Research Articles

Abstract 5789: Discovery of clinical candidate BMS-986158, an oral BET inhibitor, for the treatment of cancer

Abstract Background: The bromodomains and extra-terminal domain (BET) proteins are a family of 4 adapter proteins, BRD2, BRD3, BRD4, and BRDT, that bind to specific acetylated lysine residues on the histone tails of chromatin and recruit additional proteins to regulate gene transcription. The c-MYC oncogene, which is amplified and deregulated in 40% to 70% of all cancers, is directly regulated by BET proteins. Preclinical studies provide a strong rationale for pursuing transcriptional regulation via BET inhibition in cancer treatment (Lenhart, et al. Mol Cancer Ther. 2015;14:2167-2174; Filippakopoulos, et al. Nature. 2010;468:1067-1073). Here, we present results of crystal structure-guided structure-activity relationship (SAR) studies that resulted in the identification of BMS-986158, a highly potent BET inhibitor. Methods: Using fluorescence resonance energy transfer (FRET), we screened a library of compounds and identified a carbazole series of BET inhibitors. Alkylation of the carbazole nitrogen resulted in a 10-fold boost in potency against BET. We then created a differently oriented carbazole series and, subsequently, a carboline series of compounds to improve potency and pharmaceutical properties. A thermal shift assay was used to evaluate selectivity for binding to the BET family of bromodomains. Results: Crystal structure and subsequent SAR studies demonstrated that the isoxazole moiety formed critical interactions with the BET bromodomains. Lead compounds demonstrated potent binding to BRD4 and reduction in c-MYC expression and proliferation in cell lines such as KMS-11. Accessing a second lipophilic pocket in the BRD4 binding site increased potency significantly. Modification of the lead series from a carbazole carboxamide to a carboline resulted in significant improvement in pharmaceutical properties and led to the identification of BMS-986158, which demonstrated in vitro and in vivo potency against a variety of tumor types. In c-MYC-driven cancer cell lines, BMS-986158 caused dose-dependent downregulation of c-MYC expression and induced cancer cell death. BMS-986158 demonstrated > 70% tumor growth inhibition at tolerated doses in patient-derived xenograft models (lung, colorectal, and triple-negative breast cancers). Antitumor activity in mice and pharmacokinetic properties in animal studies support oral dosing in humans. Conclusions: Structure-based drug design led to the discovery of BMS-986158, a highly potent BET inhibitor. With promising antitumor activity in preclinical studies, BMS-986158 is currently being evaluated in a phase 1/2a clinical trial in patients with advanced cancers. Citation Format: Ashvinikumar V. Gavai, Derek Norris, David Tortolani, Daniel O'Malley, Yufen Zhao, Claude Quesnelle, Patrice Gill, Wayne Vaccaro, Tram Huynh, Vijay Ahuja, Dharmpal Dodd, Christopher Mussari, Lalgudi Harikrishnan, Muthoni Kamau, John S. Tokarski, Steven Sheriff, Richard Rampulla, Dauh-Rurng Wu, Jianqing Li, Huiping Zhang, Peng Li, Dawn Sun, Henry Yip, Yingru Zhang, Arvind Mathur, Haiying Zhang, Christine Huang, Zheng Yang, Asoka Ranasinghe, Celia D'Arienzo, Ching Su, Gerry Everlof, Lisa Zhang, Nirmala Raghavan, John T. Hunt, Michael Poss, Gregory D. Vite, Richard A. Westhouse, Susan Wee. Discovery of clinical candidate BMS-986158, an oral BET inhibitor, for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5789.

Discovery of benzimidazole derivatives as orally active renin inhibitors: Optimization of 3,5-disubstituted piperidine to improve pharmacokinetic profile

We previously identified 2-tert-butyl-4-[(3-methoxypropyl)amino]-N-(2-methylpropyl)-N-[(3S,5R)-5-(morpholin-4-ylcarbonyl)piperidin-3-yl]pyrimidine-5-carboxamide 3 as a potent renin inhibitor. Since 3 showed unacceptably low bioavailability (BA) in rats, structural modification, using SBDD and focused on physicochemical properties was conducted to improve its PK profile while maintaining renin inhibitory activity. Conversion of the amino group attached at the 4-position of pyrimidine to methylene group improved PK profile and decreased renin inhibitory activity. New central cores with carbon side chains were explored to improve potency. We had designed a series of 5-membered azoles and fused heterocycles that interacted with the lipophilic S3 pocket. In the course of modification, renin inhibitory activity was enhanced by the formation of an additional hydrogen bonding with the hydroxyl group of Thr77. Consequently, a series of novel benzimidazole derivatives were discovered as potent and orally bioavailable renin inhibitors. Among those, compound 13 exhibited more than five-fold of plasma renin inhibition than aliskiren in cynomolgus monkeys at dose ratio.

Structure-based design, synthesis and crystallization of 2-arylquinazolines as lipid pocket ligands of p38α MAPK.

In protein kinase research, identifying and addressing small molecule binding sites other than the highly conserved ATP-pocket are of intense interest because this line of investigation extends our understanding of kinase function beyond the catalytic phosphotransfer. Such alternative binding sites may be involved in altering the activation state through subtle conformational changes, control cellular enzyme localization, or in mediating and disrupting protein-protein interactions. Small organic molecules that target these less conserved regions might serve as tools for chemical biology research and to probe alternative strategies in targeting protein kinases in disease settings. Here, we present the structure-based design and synthesis of a focused library of 2-arylquinazoline derivatives to target the lipophilic C-terminal binding pocket in p38α MAPK, for which a clear biological function has yet to be identified. The interactions of the ligands with p38α MAPK was analyzed by SPR measurements and validated by protein X-ray crystallography.

Design, synthesis, and biological evaluation of 2,4-dihydropyrano[2,3-c]pyrazole derivatives as autotaxin inhibitors

Inhibition of Autotaxin (ATX) is a potential treatment strategy for several diseases, including tumors with elevated ATX-lysophosphatidic acid (LPA) signaling. Combining structure-based virtual screening together with hen egg-white Autotaxin (ewATX) activity assays enabled the discovery of novel small-molecule ATX inhibitors with a 2,4-dihydropyrano[2,3-c]pyrazole scaffold. These compounds are suggested to bind to the lipophilic pocket, leaving the active site unrestrained. Our most potent compound, (S)-6-amino-4-(3,4-dichlorophenyl)-3-(4-[(4-fluorobenzyl)oxy]phenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile [(S)-25], inhibited human ATX (hATX) with an IC50-value of 134nM. It also blocked ATX-evoked but not LPA-mediated A2058 melanoma cell migration. Noteworthy, molecular modeling correctly predicted the biologically active enantiomer of 2,4-dihydropyrano[2,3-c]pyrazoles, as verified by compound crystallization and activity assays. Our study established the ewATX activity assay as a valid and affordable tool in ATX inhibitor discovery. Overall, our study offers novel insights and approaches into design of novel ATX inhibitors targeting the hydrophobic pocket instead of the active site.

Discovery, synthesis, and structure-activity relations of 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-ones as potassium-competitive acid blockers

With the aim to discover a gastric antisecretory agent more potent than the existing proton pump inhibitors, novel 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-one derivatives, which could occupy two important lipophilic pockets (described as LP-1 and LP-2) of H+,K+-ATPase and can strongly bind to the K+-binding site, were designed based on a docking model. Among the compounds synthesized, compound 4d showed a strong H+,K+-ATPase-inhibitory activity and a high stomach concentration in rats, resulting in potent inhibitory action on histamine-stimulated gastric acid secretion in rats. Furthermore, 4d exerted significant inhibitory action on histamine-stimulated gastric-acid secretion in rats with a rapid onset and moderate duration of action after the administration. These findings may lead to a new insight into the drug design of potassium-competitive acid blockers.

O-prenylated 3-carboxycoumarins as a novel class of 15-LOX-1 inhibitors.

Allyloxy, Isopentenyloxy, geranyloxy and farnesyloxy derivatives of 3-carboxycoumarin, at position 5, 6, 7, and 8, were synthesized and their inhibitory potency against human 15-lipoxygenase-1 (human 15-LOX-1) were determined. Among the synthetic coumarins, O-allyl and O-isopentenyl derivatives demonstrated no considerable lipoxygenase inhibition while O-geranyl and O-farnesyl derivatives demonstrated potent inhibitory activity. 5-farnesyloxy-3-carboxycoumarin demonstrated the most potent inhibitory activity by IC50 = 0.74 μM while 6-farnesyloxy-3-carboxycoumarin was the weakest inhibitor among farnesyl analogs (IC50 = 10.4 μM). Bonding affinity of the designed molecular structures toward 15-LOX-1 3D structure complexed with RS75091, as potent 15-LOX-1 inhibitor, was studied by utilizing docking analysis. There was a direct relationship between lipoxygenase inhibitory potency and prenyl length chain. The ability of the prenyl portion to fill the lipophilic pocket which is formed by Ile663, Ala404, Arg403, Ile400, Ile173 and Phe167 side chains can explain the observed relationship. Similarity rate between the docked models and complexed form of RS75091, from point of view of configuration and conformation, could explain inhibitory potency variation between each prenyloxy substitution of 3-carboxycoumarins.

Bicyclic Peptide Based Lectinomimic

Peptide based lectin mimetics represent an attractive approach for the development of artificial carbohydrate receptors that might find application in bio-analytical and medicinal fields. Taking into consideration the structure of typical lectin binding site, we have designed a novel artificial receptor molecule possessing a rigid three-dimensional structure, hydrogen-bonding site and lipophilic binding pocket to promote hydrophobic interaction and hydrogen-bonding. A new solid- phase synthetic approach that allows complete synthesis of desired bicyclic peptide 1 on the solid support was developed. CD spectra of peptides 1 and 2 indicate that the structure of 1 is rather rigid and preorganised for the three-dimensional monosaccharide substrates binding. The binding affinities of bicyclic peptide receptor 1 toward various carbohydrate substrates at physiologically relevant conditions were estimated by UV/vis and fluorimetric titration experiments, and the observed values are in the millimolar range. With these results we have demonstrated that the bicyclic peptide 1 represent a promising basis for the design of new and more efficient carbohydrate receptors that may have broader application in bio-analytical or medicinal field.

Oxime Ethers of (E)-11-Isonitrosostrychnine as Highly Potent Glycine Receptor Antagonists.

A series of (E)-11-isonitrosostrychnine oxime ethers, 2-aminostrychnine, (strychnine-2-yl)propionamide, 18-oxostrychnine, and N-propylstrychnine bromide were synthesized and evaluated pharmacologically at human α1 and α1β glycine receptors in a functional fluorescence-based and a whole-cell patch-clamp assay and in [3H]strychnine binding studies. 2-Aminostrychnine and the methyl, allyl, and propargyl oxime ethers were the most potent α1 and α1β antagonists in the series, displaying IC50 values similar to those of strychnine at the two receptors. Docking experiments to the strychnine binding site of the crystal structure of the α3 glycine receptor indicated the same orientation of the strychnine core for all analogues. For the most potent oxime ethers, the ether substituent was accommodated in a lipophilic receptor binding pocket. The findings identify the oxime hydroxy group as a suitable attachment point for linking two strychnine pharmacophores by a polymethylene spacer and are, therefore, important for the design of bivalent ligands targeting glycine receptors.

The relationship between the apolipoprotein M-sphingosine-1-phosphate axis and atherosclerosis

Apolipoprotein M-sphingosine-1-phosphate axis (apoM-S1P axis) signaling pathway consists of apolipoproteinM (apoM), sphingosine-1-phosphate (S1P) and sphingosine- 1-phosphate receptor (S1PR). Plasma apoM belongs to lipocalinsuperfamily members, and is mainly associated to high density lipoprotein(HDL), whereas HDL-cholesterol correlates inversely with cardiovascular risk. The ability of apoM to bind S1P is due to a lipophilic binding pocket within the lipocalin structure of the apoM molecule. S1P, a bioactive mediator of phospholipid metabolism, predominantly abound in HDL among all lipoproteins. S1P can not only be used as intracellular second messengers, but also as intercellular signal molecules, activating of G protein-coupled receptors (S1PR) to mediate various physiological functions. It′s clear that apoM protects human beings from atherosclerosis. Furthermore, recent studies showed that S1P has a significant impact on atherosclerosis, and ApoM-S1P axis may play a important role in the pathogenesis or progression of atherosclerosis.(Chin J Lab Med, 2016, 39: 983-987) Key words: Atherosclerosis; Apolipoproteins; Lipocalins; Lysophospholipids; Sphingosine

Development of a versatile laboratory experiment to teach the metabolic transformation of hydrolysis

In this paper we describe an easy, reliable, versatile and inexpensive laboratory experiment to teach the metabolic transformation of hydrolysis to Pharmacy students. The experiment does not require the sacrifice of any experimental animal, or any work with organs or tissues, and so can be implemented in a typical university chemistry laboratory. We used acetylsalicylic acid (ASA), hexyl salicylate (HS) and two enzymes, a lipase and an esterase. Since both ASS and HS liberate salicylic acid (SA) upon hydrolysis, students can evaluate the different enzymatic transformations by monitoring the amount of SA liberated. The learning outcomes are an enhanced student understanding of: (1) the process of hydrolysis; (2) the application of enzymatic transformations of molecules from food to xenobiotics; (3) the differences between the general specificity of substrate of both enzymes; (4) the concepts of the lipophilic pocket; (5) the catalytic triad and its regioselectivity in relation to the ester bond. A questionnaire was administered to participating students at three points in time: at the beginning of the module, after enzymatic hydrolysis was taught in class, and after the laboratory experiment. From an analysis of the questionnaire data we conclude that this practical helped Pharmacy students to understand these concepts.

Discovery of 4-[(5-arylidene-4-oxothiazolidin-3-yl)methyl]benzoic acid derivatives active as novel potent allosteric inhibitors of protein tyrosine phosphatase 1B: In silico studies and in vitro evaluation as insulinomimetic and anti-inflammatory agents

New 4-{[5-arylidene-2-(4-fluorophenylimino)-4-oxothiazolidin-3-yl]methyl}benzoic acids (5) and 2-thioxo-4-thiazolidinone analogues (6) were synthesised as a part of a continuing search for new inhibitors of protein tyrosine phosphatase 1B (PTP1B), an enzyme which is implicated in metabolic disorders and inflammatory signaling. Most of the tested compounds were shown to be potent PTP1B inhibitors. Moreover, their inhibition mechanism was markedly influenced by the substituents in the positions 2 and 5, as kinetic studies indicated. Docking experiments suggested that certain derivatives 5 and 6 may efficiently fit into an allosteric site positioned between the β-sheet including Leu71 and Lys73 and a lipophilic pocket closed by the loop consisting of Pro210 to Leu 204. In cellular assays, several of these new 4-thiazolidinone derivatives showed insulinomimetic and anti-inflammatory properties. Out of them, compound 5b exhibited the most promising profile, being able to promote the activation of both insulin receptor and downstream Akt protein as well as to increase 2-deoxyglucose cellular uptake. Interestingly, compound 5b was also able to interrupt critical events in inflammatory signaling.

Discovery of a 7-arylaminobenzimidazole series as novel CRF1 receptor antagonists

A promising lead compound 1 of a benzimidazole series has been identified as a corticotropin-releasing factor 1 (CRF1) receptor antagonist. In this study, we focused on replacement of a 7-alkylamino group of 1, predicted to occupy a large lipophilic pocket of a CRF1 receptor, with an aryl group. During the course of this examination, we established new synthetic approaches to 2,7-diarylaminobenzimidazoles. The novel synthesis of 7-arylaminobenzimidazoles culminated in the identification of compounds exhibiting inhibitory activities comparable to the alkyl analog 1. A representative compound, p-methoxyanilino analog 16g, showed potent CRF binding inhibitory activity against a human CRF1 receptor and human CRF1 receptor antagonistic activity (IC50=27nM, 56nM, respectively). This compound exhibited ex vivo 125I-Tyr0 (125I-CRF) binding inhibitory activity in mouse frontal cortex, olfactory bulb, and pituitary gland at 20mg/kg after oral administration. In this report, we discuss the structure–activity-relationship of these 7-arylamino-1H-benzimidazoles and their synthetic method.

Design, Synthesis, and Biological Evaluation of Imidazo[1,5-a]quinoline as Highly Potent Ligands of Central Benzodiazepine Receptors.

A series of imidazo[1,5-a]quinoline derivatives was designed and synthesized as central benzodiazepine receptor (CBR) ligands. Most of the compounds showed high CBR affinity with Ki values within the submicromolar and subnanomolar ranges with interesting modulations in their structure-affinity relationships. In particular, fluoroderivative 7w (Ki = 0.44 nM) resulted in the most potent ligand among the imidazo[1,5-a]quinoline derivatives described so far. Overall, these observations confirmed the assumption concerning the presence of a large though apparently saturable lipophilic pocket in the CBR binding site region interacting with positions 4 and 5 of the imidazo[1,5-a]quinoline nucleus. The in vivo biological characterization revealed that compounds 7a,c,d,l,m,q,r,w show anxiolytic and antiamnestic activities without the unpleasant myorelaxant side effects of the classical 1,4-BDZ. Furthermore, the effect of 7l,q,r, and 8i in lowering lactate dehydrogenase (LDH) release induced by ischemia-like conditions in rat brain slices suggested neuroprotective properties for these imidazo[1,5-a]quinoline derivatives.

A Real-World Perspective on Molecular Design.

We present a series of small molecule drug discovery case studies where computational methods were prospectively employed to impact Roche research projects, with the aim of highlighting those methods that provide real added value. Our brief accounts encompass a broad range of methods and techniques applied to a variety of enzymes and receptors. Most of these are based on judicious application of knowledge about molecular conformations and interactions: filling of lipophilic pockets to gain affinity or selectivity, addition of polar substituents, scaffold hopping, transfer of SAR, conformation analysis, and molecular overlays. A case study of sequence-driven focused screening is presented to illustrate how appropriate preprocessing of information enables effective exploitation of prior knowledge. We conclude that qualitative statements enabling chemists to focus on promising regions of chemical space are often more impactful than quantitative prediction.

Deepening the Topology of the Translocator Protein Binding Site by Novel N,N-Dialkyl-2-arylindol-3-ylglyoxylamides.

As a continuation of our studies on 2-phenylindol-3-ylglyoxylamides as potent and selective translocator protein (TSPO) ligands, two subsets of novel derivatives, featuring hydrophilic group (OH, NH2, COOH) at the para-position of the pendent 2-phenyl ring (8-16) or different 2-aryl moieties, namely, 3-thienyl, p-biphenyl, 2-naphthyl (23-35), were synthesized and biologically evaluated, some of them showing Ki values in the subnanomolar range and the 2-naphthyl group performance being the best. The resulting SARs confirmed the key role played by interactions taking place between ligands and the lipophilic L1 pocket of the TSPO binding site. Docking simulations were performed on the most potent compound of the present series (29) exploiting the recently available 3D structures of TSPO bound to its standard ligand (PK11195). Our theoretical model was fully consistent with SARs of the newly investigated as well of the previously reported 2-phenylindol-3-ylglyoxylamide derivatives.

A study on quantitative structure–activity relationship and molecular docking of metalloproteinase inhibitors based on L-tyrosine scaffold

BackgroundMMP-2 enzyme is a kind of matrix metalloproteinases that digests the denatured collagens and gelatins. It is highly involved in the process of tumor invasion and has been considered as a promising target for cancer therapy. The structural requirements of an MMP-2 inhibitor are: (1) a functional group that binds the zinc ion, and (2) a functional group which interacts with the enzyme backbone and the side chains which undergo effective interactions with the enzyme subsites.MethodsIn the present study, a QSAR model was generated to screen new inhibitors of MMP-2 based on L–hydroxy tyrosine scaffold. Descriptors generation were done by Hyperchem 8, DRAGON and Gaussian98W programs. SPSS and MATLAB programs have been used for multiple linear regression (MLR) and genetic algorithm partial least squares (GA-PLS) analyses and for theoretical validation. Applicability domain of the model was performed to screen new compounds. The binding site potential of all inhibitors was verified by structure-based docking according to their binding energy and then the best inhibitors were selected.ResultsThe best QSAR models in MLR and GA-PLS were reported, with the square correlation coefficient for leave-one-out cross-validation (Q2LOO) larger than 0.921 and 0.900 respectively. The created MLR and GA-PLS models indicated the importance of molecular size, degree of branching, flexibility, shape, three-dimensional coordination of different atoms in a molecule in inhibitory activities against MMP-2.The docking study indicated that lipophilic and hydrogen bonding interactions among the inhibitors and the receptor are involved in a ligand-receptor interaction. The oxygen of carbonyl and sulfonyl groups is important for hydrogen bonds of ligand with Leu82 and Ala83. R2 and R3 substituents play a main role in hydrogen bonding interactions. R1 is sited in the hydrophobic pocket. Methylene group can help a ligand to be fitted in the lipophilic pocket, so two methylene groups are better than one. The Phenyl group can create a π-π interaction with Phe86.ConclusionsThe QSAR and docking analyses demonstrated to be helpful tools in the prediction of anti-cancer activities and a guide to the synthesis of new metalloproteinase inhibitors based on L-tyrosine scaffold.

Synthesis and cytotoxicity of thieno[2,3-b]pyridine and furo[2,3-b]pyridine derivatives

Forty seven thieno[2,3-b]pyridines-2-carboxamides, furo[2,3-b]pyridines-2-carboxamides and tetrahydrothieno[2,3-b]quinolones-2-carboxamides derivatives were synthesized and tested for their antiproliferative activity against the NCI-60 cell lines. The 5-keto-tetrahydrothieno[2,3-b]quinolones-2-carboxamides (series 17) were found to have the greatest activity, with the compound containing a 3-methoxyphenylcarboxamide (compound 17d) being the most active, with GI50 values in the low nanomolar range against a range of cell lines, in particular the melanoma cell line MDA-MD-435 (GI50 – 23 nM) and the breast cancer cell line MDA-MB-468 (GI50 – 46 nM). Molecular modelling of series 17 against phosphoinositide specific-phospholipase C reveals that the side chains of the amino acids His356, Glu341, Arg549 and Lys438 are involved in hydrogen bonding with the ligands as well as a lipophilic pocket is occupied by the phenyl carboxamide moiety.

A polyphenylene dendrimer drug transporter with precisely positioned amphiphilic surface patches.

The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using zebrafish embryos. The unique PPD scaffold allows the precise placement of functional groups in a given environment and offers a universal platform for designing drug transporters that closely mimic many features of proteins.

Mode of interaction of 1,4-dioxane agonists at the M2 and M3 muscarinic receptor orthosteric sites

The methyl group in cis stereochemical relationship with the basic chain of all pentatomic cyclic analogues of ACh is crucial for the agonist activity at mAChR. Among these only cevimeline (1) is employed in the treatment of xerostomia associated with Sjögren’s syndrome. Here we demonstrated that, unlike 1,3-dioxolane derivatives, in the 1,4-dioxane series the methyl group is not essential for the activation of mAChR subtypes. Docking studies, using the crystal structures of human M2 and rat M3 receptors, demonstrated that the 5-methylene group of the 1,4-dioxane nucleus of compound 10 occupies the same lipophilic pocket as the methyl group of the 1,3-dioxolane 4.

Purine derivatives as potent Bruton’s tyrosine kinase (BTK) inhibitors for autoimmune diseases

Investigation of various heterocyclic core isosteres of imidazopyrazines 1 &2 yielded purine derivatives 3 &8 as potent and selective BTK inhibitors. Subsequent SAR studies of the purine series led to the discovery of 20 as a leading compound. Compound 20 is very selective when screened against a panel of 400 kinases and is a potent inhibitor in cellular assays of human B cell function including B-Cell proliferation and CD86 cell surface expression and exhibited in vivo efficacy in a mouse PCA model. Its X-ray co-crystal structure with BTK shows that the high selectivity is gained from filling a BTK specific lipophilic pocket. However, physical and ADME properties leading to low oral exposure hindered further development.