Highly Selective Inhibition of Tyrosine Kinase 2 (TYK2) for the

Article Cite This: J. Med. Chem. XXXX, XXX, XXX−XXX

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Highly Selective Inhibition of Tyrosine Kinase 2 (TYK2) for the Treatment of Autoimmune Diseases: Discovery of the Allosteric Inhibitor BMS-986165 Stephen T. Wrobleski,*,† Ryan Moslin,*,† Shuqun Lin,† Yanlei Zhang,† Steven Spergel,† James Kempson,‡ John S. Tokarski,§ Joann Strnad,∥ Adriana Zupa-Fernandez,∥ Lihong Cheng,∥ David Shuster,∥ Kathleen Gillooly,∥ Xiaoxia Yang,∥ Elizabeth Heimrich,∥ Kim W. McIntyre,∥ Charu Chaudhry,⊥ Javed Khan,§ Max Ruzanov,§ Jeffrey Tredup,§ Dawn Mulligan,§ Dianlin Xie,§ Huadong Sun,# Christine Huang,# Celia D’Arienzo,# Nelly Aranibar,# Manoj Chiney,# Anjaneya Chimalakonda,# William J. Pitts,† Louis Lombardo,† Percy H. Carter,† James R. Burke,∥ and David S. Weinstein† †

Immunosciences Discovery Chemistry, ‡Department of Discovery Synthesis, §Molecular Structure and Design, Molecular Discovery Technologies, ∥Immunosciences Discovery Biology, ⊥Leads Discovery and Optimization, #Metabolism and Pharmacokinetic Department, Pharmaceutical Candidate Optimization, Bristol-Myers Squibb Research & Development, P.O. Box 4000, Princeton, New Jersey 08543, United States S Supporting Information *

ABSTRACT: Small molecule JAK inhibitors have emerged as a major therapeutic advancement in treating autoimmune diseases. The discovery of isoform selective JAK inhibitors that traditionally target the catalytically active site of this kinase family has been a formidable challenge. Our strategy to achieve high selectivity for TYK2 relies on targeting the TYK2 pseudokinase (JH2) domain. Herein we report the late stage optimization efforts including a structure-guided design and water displacement strategy that led to the discovery of BMS-986165 (11) as a high affinity JH2 ligand and potent allosteric inhibitor of TYK2. In addition to unprecedented JAK isoform and kinome selectivity, 11 shows excellent pharmacokinetic properties with minimal profiling liabilities and is efficacious in several murine models of autoimmune disease. On the basis of these findings, 11 appears differentiated from all other reported JAK inhibitors and has been advanced as the first pseudokinase-directed therapeutic in clinical development as an oral treatment for autoimmune diseases.

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INTRODUCTION Tyrosine kinase 2 (TYK2)1 is a member of the Janus family of kinases (JAK) that also includes JAK1, JAK2, and JAK3. The JAK family of nonreceptor tyrosine kinases is known to be critical in mediating the signaling of numerous cytokines that cause inflammation.2−4 As a result, small molecule inhibitors of the JAK kinases offer promise as effective treatments for a variety of serious inflammatory and autoimmune diseases.5,6 To date, all known small molecule JAK inhibitors that have progressed into development are active site-directed inhibitors that bind to the adenosine triphosphate (ATP) site of the catalytic domain (also referred to as the JH1 or “Janus Homology 1” domain) of the JAK protein, which prevents © XXXX American Chemical Society

catalytic activity of the kinase by blocking ATP, downstream phosphorylation, and resulting pathway signal transduction.6 This includes the first generation clinically approved inhibitors 1−4 as well as the second-generation inhibitors 5−10 currently in development (Figure 1). In contrast, BMS-986165 (11) is differentiated from previous JAK inhibitors due its unique ability to selectively bind to the pseudokinase (JH2) domain of TYK2 and inhibit its function through an allosteric mechanism. This work will describe the late-stage discovery efforts that Received: March 14, 2019

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DOI: 10.1021/acs.jmedchem.9b00444 J. Med. Chem. XXXX, XXX, XXX−XXX

Journal of Medicinal Chemistry

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Figure 1. Structures of the first-generation clinically approved JAK inhibitors 1−4, the second-generation experimental JAK inhibitors 5−10, and the TYK2-selective allosteric inhibitor 11 in the clinic for the treatment of chronic immunological disorders. Inhibitors 1−10 are conventional active-site (JH1) inhibitors, whereas 11 is an allosteric (JH2) inhibitor.

baricitinib (3). Inhibitor 2 has been approved as a treatment for myelofibrosis and is also being explored in phase III studies as an oral treatment for steroid-refractory graft vs host disease (GvHD) and as a topical treatment for atopic dermatitis (AD).24−26 Inhibitor 3 has demonstrated efficacy in RA and PSO patients in phases III and IIb, respectively, and is also being explored in SLE and atopic dermatitis in phase II trials.27−30 However, safety concerns remain as only the lower 2 mg dose of 3 was recently approved by the FDA to treat moderate-to-severely active RA patients due to a safety concern related to a potential thrombosis risk at the higher, more efficacious 4 mg dose.31 The pan-JAK inhibitor peficitinib (4) has also shown efficacy in RA patients in two phase III trials and was recently approved in Japan.32,33 Although these first-generation JAK inhibitors have established proof-of-concept in treating serious diseases, achieving robust efficacy while maintaining a safe therapeutic window, has been a significant challenge in the long term treatment of chronic diseases. Dose-limiting side effects such as anemia, neutropenia, and increased infection risk and dyslipidemia have been observed34−36 and attributed to inhibition of JAK1 and JAK2, the latter of which is well-known to be involved in hematopoiesis.37 These safety concerns led to the development of second-generation JAK inhibitors that have been reported to be more selective over JAK2, including the reported JAK1selective inhibitors filgotinib (5), upadacitinib (6), and abrocitinib (7).38−40 These inhibitors have recently advanced into phase III clinical trials with some encouraging safety and tolerability results. Inhibitor 5 has been reported to show efficacy in RA in combination with methotrexate or as a single agent without the side effects such as anemia or changes in levels of lymphocyte, natural killer (NK) cells, or liver function tests (LFT) observed with 1.41−43 However, increased creatinine levels and reduced neutrophil and platelet counts were observed. Inhibitor 5 was also reported to show efficacy

ultimately led to the identification of 11, currently in phase III clinical trials as a potential treatment for psoriasis. Because of the high homology of the ATP active site across the kinome and especially within the JAK family, achieving high selectivity for a specific JAK family member while also maintaining selectivity within the kinome is a significant challenge. As a result, many JAK inhibitors that have been developed are pan-JAK inhibitors or are modestly selective for one or more JAK family member. While these inhibitors have shown encouraging results in treating autoimmune diseases, undesirable side effects leading to a narrow therapeutic index have been observed and suggests the need for improved treatments. Tofacitinib (1), a pan-JAK inhibitor of JAK1, JAK2, JAK3, and to a lesser extent TYK2, became the first orally available small molecule kinase inhibitor to be approved for the treatment of moderately to severely active rheumatoid arthritis (RA) in 2012.7 However, only the lower 5 mg twicedaily dose of 1 was approved by the Food and Drug Administration (FDA) based on an unfavorable risk-to-benefit ratio observed with the higher 10 mg twice-daily dose. Efficacy was also achieved with 1 in late-stage phase III clinical trials for the treatment of psoriasis (PSO), psoriatic arthritis (PsA), and ulcerative colitis (UC) and recently gained FDA approval for the treatment of active PsA and moderately to severely active UC.8−16 Despite these achievements, the FDA declined approval of 1 for the treatment of PSO in 2015 based on issues of clinical efficacy and long-term safety.17 It is currently in phase III studies for the treatment of ankylosing spondylitis (AS), phase II studies for alopecia areata (AA) and inflammatory eye disease, and phase I studies for systemic discoid lupus erythematosus (DLE), systemic lupus erythematosus (SLE), diffuse cutaneous systemic sclerosis (dcSSc), and treatment-refractory dermatomyositis.18−23 Other firstgeneration JAK inhibitors approved include the JAK1/JAK2 selective inhibitors ruxolitinib (2) and the structurally related B



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in Crohn’s disease (CD) by meeting phase II primary end points in a 10-week interim analysis without any drug-related significant adverse events (SAEs).44 More recently, the JAK1selective inhibitor 6 was disclosed to have met all primary and ranked secondary end points in a phase III study in RA, yet laboratory changes were shown to be very similar to those observed with 1.45 This included increased levels of liver transaminases, creatine phosphokinase, LDL cholesterol, and HDL cholesterol and decreased counts of NK cells, lymphocytes, and neutrophils. Other reported more selective inhibitors are in development, including the JAK1-selective inhibitor 7, that has advanced to phase III studies in atopic dermatitis46 and the dual JAK3/TEC family irreversible inhibitor PF-06651600 (8)47 being investigated in phase II studies in CD, UC, and AA.48−50 Despite this progress, it is yet to be determined whether more selective JAK1 and/or JAK3 inhibition can achieve a superior therapeutic profile compared to first-generation inhibitors in these complex diseases. Selective inhibition of TYK2 has recently emerged as a potential strategy for treating various autoimmune diseases.51−53 A dual JAK1/TYK2 inhibitor PF-06700841 (9)54 has shown efficacy in patients with plaque PSO in phase II studies55,56 and is currently enrolled in additional phase II studies for CD, UC, and AA.48−50 Yet, at maximally efficacious doses in PSO patients, 9 gave significant reductions in absolute reticulocyte and neutrophil counts as well as reduced platelet counts that was believed to be associated with JAK2 and JAK1 inhibition, respectively.56 The inhibitor PF-06826647 (10) has recently been disclosed to be more selective for TYK2 and is currently under evaluation in phase I studies for the treatment of PSO.57−59 Our goal was to identify a more selective TYK2 inhibitor in the hope of establishing clinical efficacy in autoimmune diseases while demonstrating an improved safety profile. Toward that goal, we were the first to report the discovery of highly selective allosteric TYK2 inhibitors that act by their unique ability to bind to and stabilize the TYK2 pseudokinase (JH2) domain to block TYK2 signaling.60,61 On the basis of these initial findings, we disclose in the preceding article our hit-to-lead efforts that led to a new series of N-methylpyridine3-carboxamides (nicotinamides) and N-methyl pyridazine-3carboxamides as allosteric TYK2 inhibitors that have demonstrated in vivo proof-of-concept in CD40 agonistinduced colitis, a murine disease model of inflammatory bowel disease (IBD).62 Herein, we report further optimization efforts within this series that culminated in the discovery of BMS-986165 (11) currently under clinical development as a potential treatment for PSO, CD, and SLE (Clinicaltrials.gov identifiers NCT03624127, NCT03611751, NCT03599622, NCT03252587). Comparison of the TYK2 and other JAK family biochemical potencies of 11 relative to the classic activesite clinical JAK inhibitors 1−10 show a distinct selectivity profile that is envisioned to permit maximal efficacy from selective TYK2 inhibition but with decreased potential for adverse side effects that have been observed with less selective inhibitors (Table 1). As noted, 11 is a potent allosteric inhibitor of TYK2 that acts by binding to the TYK2 JH2 domain with high affinity (IC50 = 0.2 nM) and achieves remarkable selectivity over inhibition of catalytically active JH1 domains of the JAK family, a distinct profile that translates to an observed high functional selectivity for TYK2 over JAK1, JAK2, and JAK3.63 Consistent with this selectivity profile, 11

Table 1. Reported JAK Family Biochemical Potencies for Clinical Inhibitors 1−10 Compared to 11e assay IC50 (nM) compd

JAK1

JAK2

JAK3

TYK2 (JH1/JH2)

1a 2a 3a 4b 5a 6c 7a 8a 9a 10a 11d

15 6 4 4 363 47 29 >10000 17 383 >10000

77 9 7 5 2400 120 803 >10000 77 74 >10000

55 487 787 0.7 >10000 2304 >15000 33 6494 >10000 >10000

489/nd 30/nd 61/nd 5/nd 2600/nd 4690/nd 1250/nd >10000/nd 23/nd 17/nd >10000/0.2

a Assays run in the presence of 1 mM ATP according to ref 5 for 1−3 and 5, ref 40 for 7, ref 47 for 8, ref 54 for 9, and ref 58 for 10. bAssays run at the Km for ATP according to ref 33. cAssays run in the presence of 0.1 mM ATP according to ref 39. dUsing homogeneous timeresolved fluorescence (HTRF) binding assays measuring the displacement of a probe compound (please see Experimental Section). end: not determined.

has recently shown encouraging efficacy in phase II studies64 in treating patients with active PSO without incidences of adverse effects that have commonly been observed with less selective JAK inhibitors such as neutropenia, elevations in liver enzyme levels or serum creatinine, or dyslipidemia. Furthermore, 11 has demonstrated robust efficacy in murine models of lupus nephritis and IBD.63 Herein, we disclose additional preclinical studies with 11 that demonstrate robust efficacy in a murine psoriasis-like disease model that further supports the therapeutic potential of this agent as a treatment across multiple autoimmune diseases. A Novel Allosteric Approach to Selective TYK2 Inhibition. Small molecule TYK2 inhibitors that are able to block both the IL-23/IL-12 and the type I interferon (IFNα, IFNβ) pathways may offer the potential to safely and more efficaciously treat a broad spectrum of inflammatory and autoimmune diseases. However, a significant challenge in this regard is achieving the desired level of TYK2 selectivity to avoid undesirable off-target effects. This includes ensuring adequate selectivity over the other members of the JAK kinases as well as against the entire kinome containing >500 kinases. Despite the potential of TYK2 inhibition, identifying small molecules that are selective is challenging. Our strategy relies on small molecule allosteric inhibitors such as the Ndeuteromethyl pyridazine carboxamide 12 that potently inhibit TYK2-dependent signaling with high specificity by binding to and stabilizing its pseudokinase JH2 domain (Figure 2).60−64 The JH2 domain directly precedes the catalytically active JH1 kinase domain containing the canonical ATP-binding site, a structural feature that is unique to the JAK family.65 While the TYK2 JH2 domain closely resembles its JH1 domain and contains an ATP binding site much like the JH1 domain, specific residue differences within JH2 precludes any catalytic function.66 Although the precise mechanism of the allosteric inhibition of TYK2 through the JH2 domain remains to be elucidated, evidence suggests that small molecule ligand binding to JH2 stabilizes autoinhibitory intramolecular interactions between the JH2 domain and the JH1 active site. These JH2−JH1 interactions are believed to limit the C



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efforts that provided in vivo proof-of-concept in a murine model of IBD.62 As a result, further optimization was focused on improving potency in human whole blood (hWB) within this series. In addition, mitigation of a potential cardiovascular liability was required because 12 was shown to be an inhibitor of the human ether-á-go-go-related gene (hERG) ion channel in vitro (patch clamp IC50 = 10.9 μM) that translated into an observed QTc prolongation in an in vivo telemetrized rabbit study (data not shown). Fortunately, emerging structure− activity relationships (SAR) studies in replacing the 2aminopyridyl side chain in 12 with alkyl amide side chains, in particular cyclopropyl amide, gave reduced hERG inhibition and suggested a path forward, albeit with some decrease in potency.62 Therefore, immediate optimization efforts were focused on improving potency within the series to better enable mitigation of the potential hERG liability while allowing for a lower projected human dose. Because of the aforementioned role of the deuteromethyl amide group in providing high selectivity by binding to the atypical “alanine pocket” of TYK2 JH2, this group was maintained and optimization was instead focused on modifications around the aryl methyl sulfone group of 12. These efforts were guided by X-ray cocrystal structures of sulfone analogues such as 12 bound to TYK2 JH2 (Figure 3).62 Notably, the methyl group

Figure 2. Schematic illustrating the general protein structure of TYK2 and depicting the N-deuteromethyl pyridazine carboxamide 12 that potently inhibits TYK2 dependent signaling by binding to the TYK2 pseudokinase (JH2) domain with high specificity over the JAK family kinase (JH1) domains.

conformational mobility of the JH1 active site that is required for phosphotransfer catalysis.67,68 A notable advantage of inhibiting TYK2 by binding to its JH2 domain is the potential to achieve maximal efficacy while maintaining a high level of selectivity over the kinome, especially with respect to the other JAKs. To that end, we have previously demonstrated in vivo proof-of-concept studies with the JH2 ligand 12 in a CD40 agonist-induced colitis murine disease model of IBD62 Inhibitor 12 has been shown to be highly selective for TYK2 over JAK1, JAK2, and JAK3 by virtue of a key deuteromethyl amide substituent. Importantly, this group provides high selectivity by binding to a pocket created by a rare alanine residue (“alanine pocket”) in the TYK2 JH2 ligand binding domain. Furthermore, deuteration of the N-methyl group was shown to block generation of a less selective primary amide metabolite in vivo by suppressing an N-demethylation metabolic pathway via deuterium kinetic isotope effect (DKIE).62 In homogeneous time-resolved fluorescence (HTRF) biochemical affinity assays that measure the inhibition of binding of fluorescein-tagged probe molecules,60 12 binds to the TYK2 JH2 domain with high affinity (IC50 = 0.5 nM) and specificity over binding to the TYK2, JAK1, JAK2, and JAK3 catalytically active JH1 domains (IC50 values >10000 nM).62 In cell-based luciferase reporter assays in T-cells that measure JAK family functional selectivity,60 12 is a selective inhibitor of IFNα-stimulated TYK2-dependent signaling (IC50 = 27 nM) and is highly selective over GM-CSF stimulated JAK2-dependent signaling (∼270-fold) and IL-2 stimulated JAK1/3-dependent signaling (∼210-fold). Furthermore, 12 is also highly selective (>1000-fold) against >250 kinases in an in-house panel using similar biochemical affinity assays with the only exception being cKit (∼690-fold). On the basis of the encouraging selectivity profile and preclinical proof-of-concept studies of 12, efforts were focused on continued optimization within this series of allosteric TYK2 inhibitors to identify potential candidates for advancement into clinical development.

Figure 3. X-ray crystal structure representation of 12 cocomplexed with TYK2 JH2 (PDB 6NZR). Carbons of 12 in magenta. TYK2 JH2 ribbon and carbons in green. Key hydrogen bond interactions within the ligand binding site are represented as dotted lines. Binding regions, including the unique “alanine pocket”, and the observed structural water are highlighted in blue text with other key residues labeled. The P-loop region has been partially omitted for clarity.

of the methyl sulfone of 12 favorably occupies a shallow lipophilic pocket in the C-terminal domain region that is created by Pro694, the side chain of Leu741, and the methine backbone of Asn739 at the bottom of the ligand binding site. Additional favorable interactions between 12 and TYK2 JH2 include two hydrogen bonds to the conserved Lys642 from the N-deuteromethyl amide carbonyl oxygen and one of the sulfone oxygens as well as the presence of a structural water molecule facilitating indirect hydrogen bond interactions between the second sulfone oxygen of 12 with the C-terminal domain Arg738 and the Gln597 of the P-loop region. On the basis of these observations, and due to our previous success in displacing a structural water resulting in improved potency in an early series of p38 kinase inhibitors,69 we were inspired to

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RESULTS AND DISCUSSION Program Objectives for Further Optimization. Inhibitor 12 was a promising analogue from our initial hit-to-lead D



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Gratifyingly, one of the initial analogues 15 containing a cyano group at C3′ showed a significant improvement in potency compared to the C3′ unsubstituted analogue 14, giving comparable potency to the sulfone 13 in both the TYK2 JH2 and IFNα cellular assay. Although 15 was ∼3-fold less potent in hWB vs 13, we were encouraged by this initial result and expanded our SAR investigation to include C3′ amides. The intermediate acid 16 was prepared and tested along with the primary amide 17 and the N-methyl amide 18. All of these analogues were found to be nearly equipotent to 13 in binding and cellular potency including in hWB, with the exception of acid 16, which did not show any activity in cells likely due to poor permeability as measured in an in vitro Caco-2 permeability assay (apical-to-basal Pc < 15 nm/s). Remarkably, removal of the C2′ methoxy group while retaining the C3′ methyl amide in 19 results in a ∼60-fold loss in TYK2 JH2 potency, ∼100-fold loss in functional potency, and no significant activity in hWB at the highest concentration tested, thereby highlighting the importance of the C2′ methoxy group. Transposition of the amide group from the C3′ position to the adjacent C4′ position was also explored while maintaining the C2′ methoxy group as in 20 and 21. These analogues were also potent in the TYK2 JH2 assay but were noticeably less potent in the cellular assays relative to their C3′ amide counterparts 17 and 18, possibly due to decreased permeability as observed in the Caco-2 assay (apical-to-basal Pc = 50 nm/s for 18 vs 80 μM) and a measurable, but low, permeability in the Caco-2 assay (apical-to-basal Pc = 23 nm/s). More surprisingly, potency in hWB for the cyclopropyl amide 42 was maintained (IC50 = 16 nM), in contrast to cyclopropyl amide-containing analogues in the methyl sulfone series, which typically showed reduced potency in hWB.62 Furthermore, 42 showed good in vitro mouse microsomal stability (93% remaining after 10 min incubation). Because 42 represented a promising profile for advancement, the corresponding deuterated methyl amide 43 was prepared to prevent in vivo metabolism of the N-methyl amide 42 by an N-dealkylation pathway, a strategy that had been shown to be successful in the methyl sulfone series.62 Unfortunately, oral administration of 43 to C57BL/6 mice at 10 mg/kg as a solution in a PEG-300 based vehicle afforded lower than expected drug exposures due to a low initial maximum concentration (Cmax = 310 nM). This finding was attributed to low permeability rather than poor metabolic stability as 43 showed reduced permeability in the Caco-2 assay (apical-tobasal Pc < 15 nm/s). To specifically address the permeability issue, the pyridazine variant of 43 was prepared because previous pyridazines within the series had routinely resulted in improved permeability relative to their pyridine counterparts.62 This modification resulted in the identification of 11, a compound with significantly improved permeability (apical-tobasal Pc = 70 nm/s) that translated to a 24-fold improvement in Cmax relative to its pyridine counterpart 43 in mouse PK studies (Cmax = 7.5 μM for 11 vs 310 nM for 43). In addition, 11 maintained excellent potency in human and mouse whole blood (IC50 values = 13 and 100 nM, respectively) and showed no significant hERG inhibition in the flux assay (IC50 > 80 μM). Having achieved a favorable potency and selectivity profile with excellent PK properties and reduced hERG inhibition, 11 was more fully characterized as a potential candidate for advancement. X-ray Structure Confirms Proposed Binding Mode of C3′ Triazole 11. An X-ray structure of triazole 11 bound to TYK2 JH2 was solved, confirming the proposed binding mode (Figure 5a). Similar to previous X-ray cocrystal structures within the series, the pyridazine core and pendant C6 amino and C3 methyl amide side chains form a hydrogen bonding triad to the hinge region of the protein. The cyclopropyl group projects into the extended hinge region and the Ndeuteromethyl amide group occupies the “alanine pocket” near Ala671, the binding feature critical for achieving high TYK2 JH2 selectivity.62 The C2′ methoxy forms a hydrogen bond with the conserved Lys642 with the methyl group of the methoxy buried into the shallow C-terminal lipophilic pocket proximal to Pro694 and Leu741 (vide supra). Remarkably, the des-methoxy variant of 11 (not shown) was determined to be ∼100-fold less potent in TYK2 JH2 binding affinity compared to 11 and was inactive in hWB (IC50 > 10 μM), illustrating the contribution of the C2′ group to potency. A similar finding was previously observed in comparing the C3′ amide 18 and its des-methoxy counterpart 19 (Table 2). In this comparison, the results are reminiscent of the methyl effect in protein−ligand

a

In vitro assays. Mean values determined from at least three experiments unless otherwise noted. bMouse liver microsomal stability as percent remaining after a 10 min incubation. cValue determined from one experiment. dnd: not determined.

unique “alanine pocket” of TYK2 JH2.62 Gratifyingly, 38 was consistent with this trend, providing >1000-fold selectivity for TYK2 JH2 when tested in HTRF binding assays against an inhouse kinase panel consisting of ∼260 diverse kinases, including the JH1 domains of TYK2, JAK1, JAK2, and JAK3. Unfortunately, additional off-target profiling of 38 in a highthroughput ion channel flux assays revealed that it was a modest inhibitor of the hERG ion channel (IC50 = 31 μΜ) reminiscent of the initial lead 12, which had shown QTc prolongation in telemetrized rabbits (vide supra). While the ∼10-fold improvement in potency in hWB was anticipated to improve the therapeutic window, we continued to explore SAR in an attempt to further reduce the hERG inhibition. These investigations focused on modifications of the C6 side chain within the potent C3′ N-methyl triazole series (Table 5). Differentially substituted 2-aminopyridine side chains (R1) were explored such as in 39 and 40, however, a reduction in hERG inhibition was not realized (hERG flux IC50 = 6.7 and 16 μM, respectively). More extensive modification to include G



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Table 5. Select Analogues from C3′ N-Methyl Triazole Series

a

In vitro assays. Mean values determined from at least three experiments unless otherwise noted. bValue determined from one experiment. cMouse liver microsomal stability assay measuring percent remaining after a 10 min incubation period or half-life (T1/2) in minutes. dMean value determined from two experiments.

Figure 5. (a) X-ray cocrystal structure of triazole 11 in TYK2 JH2 (PDB 6NZP) showing key interactions including hydrogen bonds to hinge region of JH2 via N-methyl pyridazine amide, the d3-N-methyl amide occupying the unique alanine pocket (Ala671) with the cyclopropylamide in the extended hinge region, the key triazole moiety displacing structural water present in X-ray structure of 12 to form a direct hydrogen bond to Arg738, and the orientation of the C2′ methoxy near Lys642 protruding into a shallow, C-terminal lobe pocket (displayed in gray surface representation). (b) WaterMap simulation73 results superimposed with X-ray structure of 11 predict multiple unfavorable (ΔG > 2.2 kcal/mol) waters W1−W5 that are likely displaced by C3′ triazole and C2′ methoxy groups of 11.

binding, sometimes referred to as the “magic methyl” effect, where addition of a methyl in place of hydrogen results in dramatic increase in potency due to preferred conformational biasing and burial of the methyl group in a hydrophobic pocket of the protein.71,72 Although, in this instance, in addition to providing favorable conformational control and hydrophobic interactions, the C2′ methoxy also forms a direct hydrogen

bond interaction with the protein (Lys642) that likely contributes to the observed increase in potency. The crystal structure also confirmed that displacement of the structural water molecule observed in 12 by the newly installed C3′ triazole group of 11 was realized with the N-2 triazole nitrogen engaging in a direct hydrogen bond with Arg738 as designed. In an attempt to understand additional factors that may be H



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contributing to the potency of 11, a WaterMap simulation73 of the TYK2 JH2 ligand binding domain was performed using the X-ray structure of 11 with the ligand present but with the methoxy group and triazole ring replaced with hydrogens. This simulation predicted the presence of an energetically unfavorable water molecule (W1) that overlapped with the structural water molecule that was shown to be displaced by the C3′ triazole of 11 (Figure 5b). In addition, several other high energy waters were predicted in the ligand binding site. Most notably are the presence of additional waters that are likely displaced by the C3′ triazole group (W2−W4) and the C2′ methoxy group (W5) of 11. This analysis is consistent with SAR that highlights the importance of these groups for potency and suggests that displacement of energetically unfavorable waters contributes to the high affinity of 11 for binding to the TYK2 JH2 domain. Potency and Selectivity Profile of 11. Because of its high affinity approaching the lower limits of the binding assay, we evaluated 11 using a Morrison titration by varying the concentration of the fluorescent probe in the TYK2 JH2 assay.63 This analysis gave results that were consistent with competitive binding and determined a dissociation constant (Ki) of 0.02 nM for 11.63 In addition, 11 was evaluated in both binding and human cellular assays to determine selectivity within the JAK family and across the kinome (Table 6).63 Consistent with earlier analogues, 11 is highly specific for binding to TYK2 JH2 and does not show any significant binding affinity in the canonical TYK2, JAK1, JAK2, and JAK3 JH1 assays (IC50 values >10000 nM). Furthermore, 11 is

>1000-fold selective against an in-house panel of 249 protein and lipid kinases and pseudokinases, with the exception of BMPR2 (IC50 = 193 nM) and JAK1 JH2 pseudokinase domain (IC50 = 1 nM). Binding affinity assays for JAK2 and JAK3 JH2 domains were not available for evaluation. Despite its potent affinity for JAK1 JH2, low functional activity in a JAK1/JAK3 dependent IL-2 stimulated cellular assay is observed as 11 is ∼300-fold less potent in the IL-2 assay (IC50 = 592 nM) compared to the TYK2-dependent IFNα assay using the same pSTAT5 end point. Similarly, weak potency was measured against other JAK1-regulated pathways not dependent on TYK2, including IL-6-stimulated phosphorylation of STAT3 and IL-13-stimulated STAT6 phosphorylation.63 JAK1/JAK3 functional potency of 11 in hWB was also determined using an IL-2 stimulated STAT5 phosphorylation assay (IC50 = 1900 nM), which is ∼150-fold less potent than TYK2-dependent IFNα pSTAT5 phosphorylation in hWB (IC50 = 13 nM). The JAK1/JAK2-mediated IL-6-stimulated pSTAT3 response in hWB was similarly weak (IC50 = 609 nM). This high functional selectivity was consistently observed within the series and suggests that either allosteric binding to JAK1 JH2 imparts decreased functional consequences relative to TYK2 JH2 binding or binding affinity determined in the JAK1 JH2 assay is overpredictive (higher) relative to JAK1 JH2 binding in cells. In addition to functional selectivity over JAK1, 11 also exhibits a high degree of functional selectivity over JAK2 relative to other reported JAK inhibitors. In a JAK2-dependent EPOstimulated STAT5A phosphorylation assay in isolated TF-1 cells, 11 does not show any significant inhibition up to a concentration of 10 μM, indicating >5000-fold selectivity for TYK2 over JAK2 signaling. High selectivity over JAK2 signaling was also demonstrated in hWB using a JAK2dependent TPO-stimulated STAT5 phosphorylation assay in platelets (IC50 > 10 μM), establishing a functional selectivity window of >770-fold at the highest concentration tested. Triazole 11 Shows Minimal Profiling Liabilities, Excellent PK Properties, and Is Highly Efficacious in Inflammatory and Autoimmune Disease Models. Having demonstrated excellent potency and functional selectivity for inhibition of TYK2-dependent responses, 11 was further profiled in vitro and showed minimal liabilities and acceptable PK properties for further advancement (Table 7). Incubation in liver microsomes shows excellent stability (T1/2 > 120 min) across multiple species including human, mouse, rat, monkey, dog, and rabbit. Good permeability is also observed in a Caco2 assay with moderate efflux (apical-to-basal Pc = 73 nm/s; basal to apical Pc = 740 nm/s; efflux ratio ∼10). Assessment of

Table 6. Selectivity Profile of 11 in Binding and Human Cellular Assays binding or cellular assaya

stimulus (pathway)

IC50, nM (selectivity)

TYK2 JH2 JAK1 JH2 TYK2 JH1 JAK1 JH1 JAK2 JH1 JAK3 JH1 in-house selectivity panel of 249 kinases

(TYK2) (JAK1) (TYK2) (JAK1) (JAK2) (JAK3) (kinome selectivity)

0.2 ± 0.1 1.0 ± 0.1 >10000 >10000 >10000 >10000 all >1000 fold-selective except BMPR2 (∼960-fold)

PBMC PBMC TF-1 PBMC PBMC PBMC

IFNα (TYK2)b IL-23 (TYK2)c EPO (JAK2)d IL-2 (JAK1/JAK3)b IL-6 (JAK1)b IL-13 (JAK1)e

2 9 >10000 (>5000×) 592 (∼300×) 615 (∼310×) 2091 (>1000×)

human whole blood

IFNα (TYK2)b TPO (JAK2)f IL-2 (JAK1/JAK3)b IL-6 (JAK1/JAK2)g

13 >10000 (>770×) 1900 (∼150×) 609 (∼47×)

Table 7. Profiling Properties of Triazole 11 profiling assays liver microsomal T1/2 (min) Caco-2 Pc (nm/s), A-to-Bb Caco-2 Pc (nm/s), B-to-Ab CYP450 inhibition IC50s (1A2, 2C9, 2C19, 2D6, 3A4) CYP Induction/PXR-TA EC50 hERG (% inhibition at 10 μM) protein binding (%free)

a

In vitro assays. Mean values determined from at least three separate experiments unless otherwise noted. bMeasuring STAT5 phosphorylation in CD3+ T-cells as end point. c Measuring STAT3 phosphorylation in CD161+ CD3+ T-cells. dMeasuring STAT5A phosphorylation in TF-1 cells (n = 2). eMeasuring STAT6 phosphorylation in mononuclear cells (n = 2). fMeasuring STAT5 phosphorylation in platelets. gMeasuring STAT3 phosphorylation in CD3+ T-cells.

aq solubility at pH 7.4

11 >120 all speciesa 73 ± 7 740 ± 140 all >40 μM >40 μM 26 ± 11c 13% human, 12% cyno, 15% mouse 5.2 μg/mLd

a

Human, rat, mouse, dog, cyno, and rabbit. bA = apical, B = basal. cn = 7 in patch clamp assay. dCrystalline free base.

I



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Table 8. In Vivo PK Summary for Triazole 11 iv PK parametersa species mouse dogc monkeyc

−1

CL (mL min 13.2 6.8 4.8

−1

kg )

po PK parametersb

Vss (L/kg)

T1/2 (h)

MRT (h)

dose (mg/kg)

Cmax (μM)

AUC (μM × h)

F (%)

2.9 2.3 2

4.2 4.6 5.3

3.6 5.5 7

10 10 10

7.5 6.9 5.9

36.4 73.6 75.7

122 128 87

a

IV administration at 1 mg/kg in 80% PEG 400/20% water unless otherwise noted. bPO administration at 10 mg/kg as a solution in ethanol/ TPGS/PEG 300 (5:5:90). cIV administration at 2 mg/kg.

Figure 6. (a) Dose−response of 11 showing inhibitory effect in an IL-23 induced psoriasis-like acanthosis mouse model74 compared to an anti-IL23 adnectin as a positive control.75 Values are presented as means ± SEM, eight mice per group. Statistical analysis was performed with one-way ANOVA. Vehicle, 5:5:90, EtOH:TGPS:PEG300. (b) Dose−response of histological scores showing dose-dependent inhibition of epidermal hyperplasia (acanthosis) and inflammatory cellular infiltration. (c) Inflammatory cytokine expression by quantitative PCR analysis of skin biopsies showing dose-dependent inhibition.

in vivo clearance rates in mouse, dog, and monkey of 13.2, 6.8, and 4.8 mL min−1 kg−1, respectively. Low volume of distribution (Vss) is also observed in the 2−3 L/kg range with moderate half-lives of ∼4−5 h across species. When administered orally at 10 mg/kg, 11 is well absorbed with excellent exposures and high bioavailability (%F > 85) in mouse, dog, and monkey. Circulating primary amide metabolite formation from N-dealkylation of the deuteromethyl amide of 11 was near the lower limits of detection ( 120 min), 11 affords low to modest J



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cellular infiltration mediated by Th17 cells and IL-22, similar to the underlying mechanisms in psoriasis (Figure 6).74 In this model, 11 dose-dependently protects from IL-23-induced acanthosis in mice, with the 15 mg/kg oral dose of 11 administered twice-daily for 9 days proving to be as effective as an anti-IL-23 adnectin as a positive control (Figure 6a).75 The 30 mg/kg twice-daily oral dose is more effective than the antiIL-23 adnectin at providing protection. Histological evaluation shows that the epidermal hyperplasia and the inflammatory cellular infiltration is also inhibited in a dose-dependent manner, with the high dose of 30 mg/kg twice daily providing protection more effectively than the anti-IL-23 adnectin positive control (Figure 6b). Quantitative polymerase chain reaction (PCR) analysis of skin biopsies reveals 11 to be quite effective at blocking inflammatory cytokine expression, including IL-17A, IL-21, and subunits of IL-12 and IL-23 (Figure 6c). PK measurements on study animals shows that the 7.5, 15, and 30 mg/kg twice-daily doses provides drug levels at or above the in vitro mouse whole blood IC50 value of 100 nM (IFNα-induced pSTAT1) for 19, 21, and 24 h, respectively. In addition to preclinical models of psoriasis, 11 has also been shown to be highly efficacious in murine models of colitis and lupus.63 These results demonstrate in an antiCD40-induced colitis model in severe-combined-immunodeficient-diseased (SCID) mice, 11 administered 50 mg/kg twicedaily provides inhibition of peak weight loss (IL-12 driven) by 99% and inhibition of histological scores by 70% comparable to an anti-p40 monoclonal antibody control. Furthermore, when orally administered up to a maximum 30 mg/kg oncedaily dose in a three-month lupus disease model using NZB/W lupus-prone mice, 11 is well-tolerated and highly efficacious in protecting from nephritis. In this latter study, efficacy is wellcorrelated with inhibition of type I IFN-dependent gene expression in both whole blood and kidneys in study mice and is at least as effective as a blocking anti-IFNαR antibody. In summary, 11 is efficacious against both type I IFN-, IL12-, and IL-23-dependent pathobiology in preclinical studies in mice. Efficacy from oral administration of 11 in all disease models studied is well correlated with coverage of the whole blood IC50 value over the dosing intervals and is at least as effective as the blocking antibody controls used in these studies. Chemistry. Preparation of the N-methyl nicotinamide and N-methyl pyridazine-3-carboxamide analogues in this work utilized similar chemistry methods as previously reported.62 The analogues were prepared from the 4,6-dichloro-N(methyl)nicotinamide (X = C) or pyridazine-3-carboxamide (X = N) intermediate 44 as the nondeuteromethyl amide (R = CH3) or deuteromethyl variant (R = CD3) (Scheme 1). Various substituted anilines (ArNH2) were coupled under basic conditions and in moderate to high yields using lithium or sodium hexamethylsilazide in THF at ambient temperature to give coupling at the C4 position exclusively to afford 45. A second coupling to install the C6 amino substituents was performed using the palladium-catalyzed Buchwald−Hartwig amination reaction76,77 to afford the final compounds 46. Initial C6 couplings were performed using XantPhos as the palladium ligand under high temperatures (130−145 °C), which resulted in low yields in some cases. However, more efficient coupling for problematic cases could be performed at lower temperatures (85−110 °C) using BrettPhos as the palladium ligand or 1,1′-bis(dicyclohexylphosphino)ferrocene (dppf) as a ligand in the case of cyclopropyl amide couplings.

Scheme 1. General Preparation of N-Methyl Nicotinamides and N-Methyl Pyridazine-3-Carboxamidesa

a

Reagents and conditions: (a) NaHMDS or LiHMDS, ArNH2, THF, rt; 53−92%; (b) Pd2(dba)3, XantPhos, Cs2CO3, DMA or 1,4-dioxane, 130−145 °C, 1 h, 23−64%; (c) Pd(OAc)2 or Pd2(dba)3 BrettPhos or dppf, K2CO3 or Cs2CO3 or LiHMDS, 1,4-dioxane, 85−110 °C, 1 h, 40−97%.

Specific substitutions (R′) were explored by either incorporating on the aniline before C-4 coupling to afford 45 or at a later stage after C6-coupling depending on functional group compatibility and/or ease of intermediate isolations. This synthetic route proved to be highly versatile for both SAR exploration as well as larger scale preparation of key compounds for advancing through preclinical studies. As an example, the synthesis of 11 is highlighted (Scheme 2). Beginning with commercially available methyl-2-hydroxy-3nitrobenzoate (47), methylation followed by ammonolysis of the intermediate methyl ester afforded amide 48. The triazole group was readily installed by reaction of 48 with DMF-DMA followed by condensation with hydrazine hydrate to afford 49. Methylation of the triazole with methyl iodide in the presence of potassium carbonate afforded a 2:1 mixture of the desired regioisomer 50 and undesired regioisomer 51, respectively. The regioisomers could be separated by supercritical fluid chromatography (SFC) to afford the desired, isomerically pure 50 in 67% overall yield. Attempts to improve the alkylation regioselectivity found that using potassium hexamethylsilazide as the base in place of potassium carbonate and using THF in place of DMF, as the solvent afforded an improved regioselectivity of ∼8:1 in favor of the desired isomer 50. This result obviated separation of the isomers by SFC chromatography on a larger scale, as the crude product enriched in the desired isomer could be crystallized to afford isomerically pure 50. With pure 50 in hand, nitro group reduction under standard palladium-catalyzed hydrogenation conditions afforded aniline 52 in 92%, which was subsequently coupled to 5362 using lithium hexamethyldisilazide as the base at ambient temperature to afford the penultimate intermediate 54 in 66% yield. Coupling of 54 with cyclopropyl amide (55) under palladium-catalyzed Buchwald−Hartwig reaction conditions76,77 using XantPhos as the palladium ligand afforded 11 in 46% yield. A significant improvement in this final coupling reaction was identified by replacing the XantPhos as a ligand with 1,1′-bis(dicyclohexylphosphino)ferrocene (dppf) and using aqueous potassium triphosphate in place of cesium carbonate as the base. These modified conditions permitted a lower reaction temperature and afforded an improved 76% K



Article

Scheme 2. Preparation of the Clinical TYK2 Inhibitor 11a

Reagents and conditions: (a) CH3I, K2CO3, DMF, rt, 98%; (b) aq NH4OH, NH3 in MeOH, rt, 86%; (c) (i) DMF-DMA, 95 °C, (ii) hydrazine hydrate, EtOH, AcOH, rt, 69% over 2 steps; (d) CH3I, K2CO3, DMF, rt, 91%, (∼2:1 mixture); (e) KHMDS, CH3I, THF, rt, 58% of pure 50; (f) 5% Pd-C, 1 atm H2, EtOH, rt, 92%; (g) LiHMDS, THF, rt, 66%; (h) Pd2(dba)3, XantPhos, Cs2CO3, 1,4-dioxane, 130 °C, 46%; (i) Pd2(dba)3, dppf, K3PO4, dioxane, 85 °C, 76%. a

that deuterium was incorporated during the de novo design and optimization process to shunt a metabolic pathway in vivo and address a specific metabolite concern. Other notable strategies in our efforts include heterocyclic core modifications (pyridine to pyridazine) to provide optimal permeability and bioavailability and the use of a cyclopropyl carboxamide as a replacement for the C6 amino heterocycles to reduce undesirable hERG ion channel activity.62 The versatility of the cyclopropane fragment in overcoming multiple roadblocks in drug discovery has been previously reported.79 In this instance, it is notable that the cyclopropyl carboxamide group was found to be an effective replacement for the 2aminopyridine side chain and reduced hERG affinity, likely due to decreased aromaticity and increased sp3 character.80 Finally, an innovative structure-based drug design strategy targeted at displacing a structural water molecule observed within the TYK2 JH2 binding site led to C3′ substituted analogues having significantly enhanced potency and ultimately resulting in the identification of 11 containing a C3′ N-methyl triazole group. These results highlight the potential of targeting the displacement of water molecules from ligand binding sites as a successful strategy for drug design and optimization and suggests the application of computational methods to predict hydration thermodynamics as potentially useful tools in directing medicinal chemistry efforts.81−85 Additional allosteric TYK2 inhibitors from our efforts will be reported in due course. In summary, 11 has been identified as a highly potent and selective allosteric TYK2 inhibitor having excellent PK properties across species with minimal profiling liabilities and is orally efficacious with dose-dependent activity in a murine disease model of psoriasis. Significant activity has also been observed with 11 in other murine autoimmune disease models of colitis and lupus.63 On the basis of these findings, 11 has been advanced into clinical studies as a potential treatment for patients suffering from a spectrum of IFN- and IL-12/IL-23 driven inflammatory and autoimmune diseases.

yield in the preparation of multigram quantities of 11 for advanced preclinical studies.

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CONCLUSION The discovery of the TYK2 inhibitor 11 as the first known pseudokinase-specific ligand to enter clinical development has been described. This work was achieved through optimization of a series of highly selective N-methyl nicotinamides and Nmethyl pyridazine-3-carboxamides as a novel class of potent allosteric inhibitors that act by binding to and stabilizing the pseudokinase (JH2) domain of TYK2. As a result of this unique mechanism, 11 is highly differentiated from all other reported JAK/TYK2 inhibitors due to its ability to achieve an unprecedented level of selectivity for TYK2, especially over JAK1, JAK2, and JAK3. Notably, several key discoveries and innovative strategies were important in identifying 11 as a suitable candidate for clinical development. A chemogenomics approach was used to find initial lead molecules that allosterically inhibit TYK2-dependent IL-23 signaling by virtue of their binding to the TYK2 pseudokinase domain.60 This key discovery spawned a medicinal chemistry effort that identified additional novel leads for optimization including the N-methyl nicotinamide series.61,62 A critical methyl amide group within this series was discovered that surprisingly afforded a high level of selectivity by accessing an atypical pocket created by a rare alanine residue (“alanine pocket”) in the ligand binding domain of TYK2 JH2. To preserve the selectivity of the methyl amides in vivo, deuterium was incorporated into the methyl group to block an N-demethylation metabolic pathway that generated a less selective primary amide metabolite. While incorporation of deuterium into drug molecules is not an uncommon practice, the large majority of known examples typically involve deuterium incorporation into already existing drug developmental candidates or marketed drugs in an attempt to decrease overall clearance rates and improve PK properties.78 Our approach is unique from these strategies in L



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(534 mg, 0.924 mmol), and cesium carbonate (4.01 g, 12.3 mmol) were added. The vessel was evacuated three times (backfilling with nitrogen) and then sealed and heated to 130 °C using a preheated oil bath for 140 min. The reaction was filtered through diatomaceous earth (washing with ethyl acetate), and the resulting filtrate was concentrated to obtain the crude product. This material was adsorbed onto diatomaceous earth using dichloromethane and was purified using automated chromatography (100% ethyl acetate) to provide 11 as a near-white solid (1.22 g, 46% yield). 1H NMR (500 MHz, CDCl3) δ 10.99 (s, 1H), 9.81 (s, 1H), 8.23 (s, 1H), 8.11 (s, 1H), 8.03 (s, 1H), 7.80 (dd, J = 7.9, 1.6 Hz, 1H), 7.52 (dd, J = 7.9, 1.5 Hz, 1H), 7.26 (t, J = 7.8 Hz, 1H), 4.00 (s, 3H), 3.81 (s, 3H), 1.88−1.82 (m, 1H), 1.16−1.06 (m, 2H), 0.94−0.83 (m, 2H). 13C NMR (500 MHz, CDCl3) δ 173.2, 166.8, 160.3, 155.8, 151.5, 146.1, 143.9, 134.9, 132.4, 127.0, 126.0, 124.5, 123.4, 97.9, 61.5, 36.4, 26.0−24.1 (m, J = 21.8 Hz, 1C), 15.9, 8.7 (s, 2C). LCMS (E+) m/z: 426.1 (MH+), RT = 0.62 min. An analytically pure sample was obtained by SFC. Anal. Calcd for C20H19D3N8O3·0.06H2O·0.03CH3OH: C 56.24; H 5.32; N 26.20. Found: C 55.86; H 5.22; N 26.12. HRMS calcd for C20H20D3N8O3[M + H]+, 426.20759; found, 426.20734. Alternative Coupling Conditions for Synthesis of 11. A mixture of 54 (17.52 g, 46.5 mmol) and cyclopropane carboxamide 55 (4.75 g, 55.8 mmol) were taken up in 1,4-dioxane (186 mL) and nitrogen bubbled through the slurry for about 10−15 min. Pd2(dba)3 (1.06 g, 1.16 mmol) and 1,1′-bis(dicyclohexylphosphino)ferrocene (1.34 g, 2.32 mmol) were then added with a continued nitrogen flow for an additional ∼5 min. An aqueous solution of potassium phosphate tribasic (2 M, 58.1 mL, 116 mmol) was then added in one portion and the reaction heated to 85 °C for 48 h. The reaction was allowed to cool to room temperature before diluting with ethyl acetate (200 mL) and water (200 mL). The separated aqueous phase was further extracted with ethyl acetate (3 × 200 mL), and the combined organic layers were then dried (MgSO4) and concentrated under vacuum to give the crude product. The crude product was then taken up in MeTHF (400 mL) and ethyl acetate (400 mL), then N-acetyl cysteine (10% aqueous solution, 300 mL) was added and the biphasic mixture was allowed to stir at room temperature overnight. The layers were separated and the aqueous phase was extracted with ethyl acetate (3 × 200 mL). The combined organics were washed with 10% ammonium hydroxide solution (500 mL), and the organic layer then dried (MgSO4) and evaporated under vacuum to afford the crude product which was purified by MPLC using a RediSep 750 g gold silica gel column and eluting with a gradient of solvent A (dichloromethane) and solvent B (20% methanol in dichloromethane) at a flow rate of 300 mL/min. The desired product was collected at 30% A to B concentration and fractions were concentrated under vacuum to afford 11 as a cream-colored solid (15.0 g, 76% yield). 4-((3-Cyano-2-methoxyphenyl)amino)-6-((5-fluoropyridin-2-yl)amino)-N-methyl-nicotinamide (15). To a suspension of 4-((3carbamoyl-2-methoxyphenyl)amino)-6-((5-fluoropyridin-2-yl)amino)-N-methylnicotinamide (17, 21 mg, 0.051 mmol) in dichloromethane (0.2 mL) and THF (0.2 mL) was added Burgess reagent (24.4 mg, 0.10 mmol) in one portion under nitrogen, and the resulting mixture was allowed to stir overnight at room temperature. HPLC and LCMS indicated only ∼15% conversion of starting material to afford the desired product (observed MH+ of 393). Therefore, the reaction was concentrated to remove the THF and dichloromethane and acetonitrile (0.3 mL) was added followed by additional Burgess reagent (24.4 mg, 0.10 mmol). After 4 h at room temperature, the reaction mixture became a clear solution and HPLC analysis indicated completed conversion of starting material to the desired product. The reaction was concentrated, diluted with DMF (1 mL), filtered, and was purified by reverse phase preparative LCMS with the following conditions: Column, Waters XBridge C18, 19 mm × 200 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Gradient: 15−100% B over 20 min, then a 5 min hold at 100% B. Flow: 25 mL/min. Fractions containing the desired product were combined and dried via centrifugal evaporation to afford 7.2 mg (35%) of 15. 1H NMR

EXPERIMENTAL SECTION

All animal research was conducted in accordance with institutional guidelines as defined by Institutional Animal Care and Use Committee for U.S. institutions and with the approval of the Bristol-Myers Squibb Animal Care and Use Committee. Mice were housed under a 12 h/12 h light/dark cycle and provided standard access to rodent chow diet and fresh drinking water ad libitum. All biochemical potencies and selectivities were determined using homogeneous time-resolved fluorescence (HTRF) assays where compounds were shown to compete with a fluorescent probe for binding to human recombinant JAK1, JAK2, JAK3, and TYK2 JH1 domain proteins in addition to TYK2 and JAK1 JH2 protein domains. Dose−response curves were generated to determine the concentration required for inhibiting 50% of the HTRF signal (IC50) as derived by nonlinear regression analysis. Cellular potencies and selectivities were determined using stably integrated STAT-dependent luciferase reporter assays in T-cells using IFNα-stimulation for measuring TYK2/JAK1 dependent signaling and IL-23 stimulation for measuring TYK2/JAK1 dependent signaling. JAK2 dependent signaling was measured in TF-1 cells using GM-CSF stimulation. Dose−response curves were generated to determine the concentration required to inhibit 50% of cellular response (IC50) as derived by nonlinear regression analysis. Potencies and selectivities for JAKdependent signaling were also measured in human and mouse whole blood using specific cytokine stimulations and measuring the phosphorylation of specific STAT proteins by cellular staining and flow cytometry. Experimental details for all assays have been previously reported.60,63 All compounds active in biological assays were electronically filtered for structural attributes common to pan assay interference compounds (PAINS) and were found to be negative.86 Synthesis. Chemistry General Methods and Compound Characterization. All reagents and starting materials were obtained from commercial suppliers and used without further purification unless otherwise stated. Reactions were run under an atmosphere of nitrogen and at ambient temperature unless otherwise noted. Reaction progress was monitored using a variety of LC instruments equipped with electrospray positive ionization detectors. Reported liquid chromatography retention times (RT) were established using the following conditions: Column, Waters Acquity UPLC BEH C18, 2.1 mm × 50 mm, 1.7 μm particles. Mobile phase A: 2:98 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 98:2 acetonitrile:water with 10 mM ammonium acetate. Temperature: 50 °C. Gradient: 0−100% B over 1 min, then a 0.5 min hold at 100% B. Flow: 0.8 mL/min. Detection: MS and UV (220 nm). In some cases, alternative liquid chromatography conditions (specified as condition B or condition C) were used. Condition B = column: Waters Acquity BEH C18, 2.1 mm× 50 mm, 1.7 μm particles. Mobile phase A: water. Mobile phase B: acetonitrile with buffer, 0.05% TFA. Temperature: 50 °C. Gradient range: 2%−98% B (0−1 min), 98% B (to 1.5 min), then 98%−2% B (to 1.6 min). Flow: 1.11 mL/min. Detection: MS and UV (220 nm). Condition C = column: Waters Acquity UPLC BEH C18, 2.1 mm× 50 mm, 1.7 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Temperature: 50 °C. Gradient: 2−98% B over 1 min, then a 0.6 min hold at 98% B. Flow: 0.8 mL/min. Detection: MS and UV (220 nm). Proton (1H NMR) magnetic resonance spectra were obtained in CDCl3, CD3OD, or DMSO-d6 at 400 MHz at 298 K unless otherwise noted. The following abbreviations were utilized to describe peak patterns when appropriate: br = broad, s = singlet, d = doublet, q = quartet, t = triplet, and m = multiplet. All final compounds used for testing in assays and biological studies had purities that were determined to be >95% by HPLC or LCMS based on ultraviolet detection at 220 nm. Synthesis of 6-(Cyclopropanecarboxamido)-4-((2-methoxy-3-(1methyl-1H-1,2,4-triazol-3-yl)phenyl)-amino)-N-(methyl-d 3 )pyridazine-3-carboxamide (11). A mixture of 54 (2.3 g, 6.2 mmol) and cyclopropane carboxamide (55, 1.05 g, 12.3 mmol) was dissolved in dioxane (62 mL), and Pd2(dba)3 (564 mg, 0.616 mmol), XantPhos M



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(500 MHz, DMSO-d6) δ 10.79 (s, 1H), 9.87 (br s, 1H), 8.58 (br d, J = 3.1 Hz, 1H), 8.50 (s, 1H), 8.17 (d, J = 3.1 Hz, 1H), 7.87 (dd, J = 7.9, 1.2 Hz, 1H), 7.77−7.58 (m, 3H), 7.50 (d, J = 7.9 Hz, 1H), 7.43− 7.33 (m, 1H), 3.92 (s, 3H), 2.79 (d, J = 4.9 Hz, 3H). LCMS (E+) m/ z: 393.1 (MH+), RT = 1.53 min. 3-((2-((5-Fluoropyridin-2-yl)amino)-5-(methylcarbamoyl)pyridin-4-yl)amino)-2-methoxy-benzoic Acid (16). A solution of 4,6dichloro-N-methylnicotinamide62 (2 g, 9.75 mmol) and 3-amino-2methoxybenzoic acid87 (1.96 g, 11.7 mmol) in 20 mL of DMA was cooled in an ice bath, and a solution of lithium bis(trimethylsilyl)amide (1 M in THF, 39.0 mL, 39.0 mmol) was added dropwise via syringe over 3−5 min. After the addition was complete, the ice bath was removed and the dark-brown mixture was allowed to warm to room temperature and stir for ∼30 min. LCMS analysis at this time indicated the complete conversion to afford a single major component that was consistent with the formation of the desired coupled intermediate (observed MH+ 336/338). The reaction was cooled in an ice bath and was quenched by the slow addition of cold water (∼150 mL), giving a dark-amber colored solution. The pH of the solution was made acidic (pH ∼ 1−2) by a dropwise addition of 6 N aq HCl, causing a heavy tan precipitate to form. The resulting slurry was allowed to stir for 1 h, then the solid was collected by vacuum filtration and the solid was rinsed with additional water (∼50 mL). The solid was allowed to partially air-dry in the funnel for 2−3 h and then was slurried in methanol (∼50 mL). Ethyl acetate (∼100 mL) was added initially, giving complete dissolution followed by precipitation of a solid. The solid was collected by vacuum filtration and dried in a funnel overnight to afford 1.0 g of an off-white solid. The resulting filtrate was concentrated under vacuum to afford an additional 2 g of additional solid (overall yield 3 g, 92%). MS (E+) m/ z: 336/338 (MH+ with chloride isotope pattern). A reaction vial was charged with solid obtained from previous step (130 mg, 0.39 mmol), 5-fluoropyridin-2-amine (60.8 mg, 0.54 mmol), BrettPhos (8.31 mg, 0.015 mmol), and Pd2(dba)3 (7.1 mg, 7.8 μmol), and the contents were flushed with nitrogen. Dioxane (1.5 mL) and DMA (0.5 mL) were then added, and the resulting slurry was sparged with additional nitrogen for ∼1 min. A solution of lithium bis(trimethylsilyl)amide (1 M in THF, 0.85 mL, 0.85 mmol) was added, and the resulting dark-amber-colored solution was heated in a preheated heating block at 110 °C for 2 h. The reaction mixture was cooled to room temperature and was analyzed by LCMS, which indicated formation of a major product that was consistent with the desired product (observed MH+ 412). The reaction mixture was diluted with water (10 mL) and made slightly acidic (pH ∼ 3) by slowly adding 1N aq HCl dropwise, causing a solid to precipitate. The slurry was allowed to stir at room temperature overnight, and then the solid was collected by vacuum filtration and dried under vacuum to afford 128 mg (80%) of 16 as a beige solid. MS (E+) m/z: 412.1 (MH+). An analytical sample for testing was prepared by purification by preparative LC/MS with the following conditions: Column, Waters XBridge C18, 19 mm × 250 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Gradient: 0−100% B over 25 min, then a 5 min hold at 100% B. Flow: 20 mL/min. Fractions containing the desired product were combined and dried via centrifugal evaporation to afford pure 16. 1H NMR (500 MHz, DMSO-d6) δ 10.68 (s, 1H), 9.81 (s, 1H), 8.52 (q, J = 4.1 Hz, 1H), 8.47 (s, 1H), 8.15 (d, J = 3.1 Hz, 1H), 7.74−7.67 (m, 3H), 7.66−7.60 (m, 1H), 7.41−7.37 (m, 1H), 7.31−7.26 (m, 1H), 3.76 (s, 3H), 2.78 (d, J = 4.3 Hz, 3H). LCMS (E+) m/z: 412.1 (MH+), RT = 0.75 min. 4-((3-Carbamoyl-2-methoxyphenyl)amino)-6-((5-fluoropyridin2-yl)amino)-N-methyl-nicotinamide (17). 3-((2-((5-Fluoropyridin2-yl)amino)-5-(methylcarbamoyl)pyridin-4-5-yl)-amino)-2-methoxybenzoic acid (16, 15 mg, 0.036 mmol), Hunig’s base (0.019 mL, 0.109 mmol), and ammonium chloride (3.90 mg, 0.073 mmol) were stirred in DMF at room temperature for a few minutes, then BOP (20.96 mg, 0.047 mmol) was added to the resulting slurry. After stirring at room temperature for 1 h, methanol (0.1 mL) and DMF (1.0 mL) were successively added and the solution was filtered

through a Millipore filter. The resulting solution was subjected to purification by reverse-phase preparative LCMS using the following conditions: Column, Waters XBridge C18, 19 mm × 200 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Gradient: 100% B over 20 min, then a 5 min hold at 100% B. Flow: 25 mL/min. Fractions containing the desired product were combined and dried via centrifugal evaporation to afford 7.6 mg (48%) of 17. 1H NMR (500 MHz, DMSO-d6) δ 10.64 (s, 1H), 10.06 (s, 1H), 8.55 (br s, 1H), 8.45 (s, 1H), 8.21−8.11 (m, 1H), 7.75 (br s, 1H), 7.63 (br dd, J = 7.6, 1.5 Hz, 4H), 7.56 (br s, 1H), 7.36−7.30 (m, 1H), 7.29−7.24 (m, 1H), 3.73 (s, 3H), 2.78 (d, J = 4.3 Hz, 3H). LCMS (E+) m/z: 411.2 (MH+), RT = 1.23 min. 6-((5-Fluoropyridin-2-yl)amino)-4-((2-methoxy-3(methylcarbamoyl)phenyl)-amino)-N-methylnicotinamide (18). Prepared from 16 in a manner similar to 17 using methylamine in place of ammonium chloride to afford 7.6 mg of 18. 1H NMR (500 MHz, DMSO-d6) δ 10.64 (s, 1H), 9.78 (s, 1H), 8.51 (br d, J = 4.3 Hz, 1H), 8.45 (s, 1H), 8.28−8.19 (m, 1H), 8.14 (d, J = 3.1 Hz, 1H), 7.74−7.57 (m, 4H), 7.30−7.20 (m, 2H), 3.71 (s, 3H), 2.78 (dd, J = 8.2, 4.6 Hz, 6H). LCMS (E+) m/z: 425.2 (MH+), RT = 1.17 min. 6-((5-Fluoropyridin-2-yl)amino)-4-((3-(methylcarbamoyl)phenyl)-amino)-N-methyl-nicotinamide (19). Prepared from 4,6dichloro-N-methylnicotinamide62 using similar procedures as described for the preparation of 17 and using 3-amino-N-methylbenzamide in place of 3-amino-2-methoxybenzoic acid to afford 8.7 mg of 19. 1H NMR (500 MHz, DMSO-d6) δ 10.63 (s, 1H), 9.81 (s, 1H), 8.48 (s, 2H), 8.56−8.43 (m, 1H), 8.10 (d, J = 2.5 Hz, 1H), 7.78 (s, 1H), 7.76−7.72 (m, 1H), 7.68−7.59 (m, 2H), 7.57−7.53 (m, 1H), 7.49 (t, J = 7.7 Hz, 1H), 7.42 (d, J = 8.9 Hz, 1H), 2.81−2.76 (m, 6H). 4-(4-Carbamoyl-2-methoxyphenylamino)-6-(5-fluoropyridin-2ylamino)-N-methyl-nicotinamide (20). To a stirred solution of 4,6dichloro-N-methylnicotinamide62 (1.0 g, 4.9 mmol) in DMA (30 mL) was added 4-amino-3-methoxybenzoic acid (1.22 g, 7.32 mmol) followed by addition of a solution of sodium bis(trimethylsilyl)amide (1 M in THF, 36.6 mL, 36.6 mmol). The reaction mixture was stirred for 2 h, at which point the THF was removed in vacuo and HCl (1 M aq) was added to adjust pH to ∼5. The resulting heterogeneous slurry was filtered to collect the solid as crude 4-(2-chloro-5(methylcarbamoyl)pyridin-4-ylamino)-3-methoxybenzoic acid. The filtrate was extracted with dichloromethane and washed with water (3×), dried, concentrated, and purified by automated silica gel chromatography (0−100% MeOH/DCM) to yield additional 4-(2chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-3-methoxybenzoic acid (0.87 g total, 53%). 1H NMR (500 MHz, DMSO-d6) δ 10.63 (s, 1H), 9.81 (s, 1H), 8.48 (s, 2H), 8.56−8.43 (m, 1H), 8.10 (d, J = 2.5 Hz, 1H), 7.78 (s, 1H), 7.76−7.72 (m, 1H), 7.68−7.59 (m, 2H), 7.57−7.53 (m, 1H), 7.49 (t, J = 7.7 Hz, 1H), 7.42 (d, J = 8.9 Hz, 1H), 2.81−2.76 (m, 6H). LCMS (E+) m/z: 336 (MH+). To a mixture of 5-fluoropyridin-2-amine (217 mg, 1.94 mmol) and 4-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-3-methoxybenzoic acid (500 mg, 1.49 mmol) was added DMA (10 mL) followed by Pd2(dba)3 (136 mg, 0.15 mmol), XantPhos (172 mg, 0.30 mmol), and cesium carbonate (0.970 g, 2.98 mmol). The vessel was then evacuated and backfilled with nitrogen three times and then heated to 145 °C for 2 h. The crude product was filtered and then concentrated to afford an oil as the crude product. This material was adsorbed onto silica gel, dried and then purified using automated chromatography (0−100% MeOH/DCM) to provide 300 mg (49%) of 4-((2-((5fluoropyridin-2-yl)amino)-5-(methylcarbamoyl)pyridin-4-yl)amino)3-methoxybenzoic acid. LCMS (E+) m/z: 412 (MH+). To a DMF (1 mL) solution containing 4-((2-((5-fluoropyridin-2yl)amino)-5-(methylcarbamoyl)-pyridin-4-yl)amino)-3-methoxybenzoic acid (30 mg, 0.073 mmol), ammonium chloride (7.8 mg, 0.15 mmol), and N,N-diisopropylethylamine (51 μL, 0.29 mmol) was added O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU, 36 mg, 0.095 mmol) and the reaction stirred for 1 h. The reaction was filtered and purified by preparative HPLC, providing 20 (12 mg, 40%). 1H NMR (500 MHz, DMSO-d6) δ 10.66 (s, 1H), 9.86 (s, 1H), 8.53−8.48 (m, 1H), 8.47 (s, 1H), 8.20 N



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(d, J = 2.0 Hz, 1H), 7.95 (s, 1H), 7.87 (s, 1H), 7.69−7.63 (m, 2H), 7.60−7.55 (m, 3H), 7.31 (br s, 1H), 3.91 (s, 3H), 2.77 (d, J = 4.5 Hz, 3H). LCMS (E+) m/z: 411.2 (MH+), RT = 1.09 min. 6-((5-Fluoropyridin-2-yl)amino)-4-((2-methoxy-4(methylcarbamoyl)phenyl)-amino)-N-methylnicotinamide (21). Prepared from 4,6-dichloro-N-methylnicotinamide62 using similar procedures as described for the preparation of 20 and using methylamine in place ammonium chloride to afford 18.3 mg of 21. 1 H NMR (500 MHz, DMSO-d6) δ 10.69−10.57 (m, 1H), 9.86 (br s, 1H), 8.51 (br s, 1H), 8.45 (s, 1H), 8.40 (br d, J = 4.4 Hz, 1H), 8.18 (s, 1H), 7.82 (br s, 1H), 7.69−7.50 (m, 5H), 3.91 (s, 3H), 2.81 (br d, J = 4.2 Hz, 3H), 2.77 (br d, J = 4.1 Hz, 3H). LCMS (E+) m/z: 425.2 (MH+), RT = 1.25 min. 4-((3-Carbamoyl-2-methoxyphenyl)amino)-6-((5-fluoro-4-methylpyridin-2-yl)amino)-N-methylnicotinamide (22). Prepared from 3(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoic acid as described for the preparation of 17 and using 2-amino-4methyl-5-fluoropyridine in place of 2-amino-5-fluoropyridine to afford 9.1 mg of 22. 1H NMR (500 MHz, DMSO-d6) δ 10.66 (s, 1H), 9.69 (s, 1H), 8.53−8.43 (m, 2H), 8.04 (s, 1H), 7.77−7.66 (m, 2H), 7.63 (dd, J = 7.6, 1.5 Hz, 1H), 7.58−7.53 (m, 2H), 7.32−7.23 (m, 2H), 3.74 (s, 3H), 2.78 (d, J = 4.3 Hz, 3H), 2.23 (s, 3H). LCMS (E+) m/z: 425.2 (MH+), RT = 1.20 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3(methylcarbamoyl)phenyl)-amino)-N-methylnicotinamide (23). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)2-methoxybenzoic acid using similar procedures as described for the preparation of 18 using 2-amino-4-methyl-5-fluoropyridine in place of 2-amino-5-fluoropyridine to afford 7.6 mg of 23. 1H NMR (500 MHz, DMSO-d6) δ 10.69 (s, 1H), 9.65 (br s, 1H), 8.55 (br s, 1H), 8.46 (s, 1H), 8.29−8.18 (m, 1H), 8.07 (s, 1H), 7.66−7.58 (m, 2H), 7.50 (br s, 1H), 7.26 (br d, J = 4.9 Hz, 2H), 3.72 (s, 3H), 2.83−2.75 (m, 6H), 2.24 (s, 3H). LCMS (E+) m/z: 439.2 (MH+), RT = 1.29 min. 4-((3-(Ethylcarbamoyl)-2-methoxyphenyl)amino)-6-((5-fluoro-4methylpyridin-2-yl)amino)-N-methylnicotinamide (24). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5-fluoropyridine in place of 2-amino-5-fluoropyridine and ethylamine hydrochloride in place of ammonium chloride to afford 9.7 mg of 24. 1H NMR (500 MHz, DMSO-d6) δ 10.70 (s, 1H), 9.71 (br s, 1H), 8.54−8.48 (m, 1H), 8.48 (s, 1H), 8.29 (br s, 1H), 8.05 (s, 1H), 7.70 (br s, 1H), 7.62 (br d, J = 7.4 Hz, 1H), 7.56 (br s, 1H), 7.32−7.14 (m, 2H), 3.72 (s, 3H), 3.35 (m, 2H), 2.78 (br d, J = 4.0 Hz, 3H), 2.24 (s, 3H), 1.13 (br t, J = 7.1 Hz, 3H). LCMS (E+) m/z: 453.2 (MH+), RT = 1.56 min. 4-((3-(Dimethylcarbamoyl)-2-methoxyphenyl)amino)-6-((5-fluoro-4-methylpyridin-2-yl)-amino)-N-methylnicotinamide (25). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5-fluoropyridine in place of 2-amino-5-fluoropyridine and dimethylamine in place of ammonium chloride to afford 6.8 mg of 25. 1H NMR (500 MHz, DMSO-d6) δ 10.67−10.54 (m, 1H), 9.71−9.63 (m, 1H), 8.54−8.42 (m, 2H), 8.04 (s, 1H), 7.68 (br s, 1H), 7.62−7.46 (m, 2H), 7.29− 7.15 (m, 1H), 6.92 (br d, J = 7.5 Hz, 1H), 3.68−3.65 (m, 3H), 2.81− 2.75 (m, 9H), 2.23 (s, 3H). LCMS (E+) m/z: 453.2 (MH+), RT (condition B) = 0.69 min. 4-((3-((Cyclopropylmethyl)carbamoyl)-2-methoxyphenyl)amino)-6-((5-fluoro-4-methyl-pyridin-2-yl)amino)-N-methylnicotinamide (26). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5fluoropyridine in place of 2-amino-5-fluoropyridine and cyclopropylmethylamine in place of ammonium chloride to afford 6.3 mg of 26. 1H NMR (500 MHz, DMSO-d6) δ 10.72 (s, 1H), 9.72 (br s, 1H), 8.51 (br d, J = 3.7 Hz, 1H), 8.48 (s, 1H), 8.37 (t, J = 5.5 Hz, 1H), 8.05 (s, 1H), 7.70 (br s, 1H), 7.64 (dd, J = 7.6, 2.1 Hz, 1H), 7.56 (br d, J = 4.3 Hz, 1H), 7.33−7.17 (m, 2H), 3.74 (s, 3H), 3.16 (t, J = 6.4 Hz, 2H), 2.78 (d, J = 4.3 Hz, 3H), 2.24 (s, 3H), 1.11−0.98 (m,

1H), 0.48−0.42 (m, 2H), 0.28−0.21 (m, 2H). LCMS (E+) m/z: 479.2 (MH+), RT = 1.57 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((3-((2hydroxyethyl)carbamoyl)-2-methoxy-phenyl)amino)-N-methylnicotinamide (27). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5fluoropyridine in place of 2-amino-5-fluoropyridine and 2-hydroxyethylamine in place of ammonium chloride to afford 6.5 mg of 27. 1 H NMR (500 MHz, DMSO-d6) δ 10.71 (s, 1H), 9.71 (br s, 1H), 8.51 (br d, J = 4.3 Hz, 1H), 8.48 (s, 1H), 8.30 (br t, J = 5.5 Hz, 1H), 8.05 (s, 1H), 7.70 (br s, 1H), 7.65 (br d, J = 6.7 Hz, 1H), 7.57 (br d, J = 4.9 Hz, 1H), 7.35−7.23 (m, 2H), 4.79 (t, J = 5.5 Hz, 1H), 3.73 (s, 3H), 3.54 (q, J = 5.9 Hz, 2H), 3.36 (m, 2H), 2.78 (d, J = 4.3 Hz, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 469.2 (MH+), RT = 1.18 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-((2morpholinoethyl)-carbamoyl)phenyl)amino)-N-methylnicotinamide (28). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4ylamino)-2-methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5fluoropyridine in place of 2-amino-5-fluoropyridine and 2-morpholinylethylamine in place of ammonium chloride to afford 8.3 mg of 28. 1 H NMR (500 MHz, DMSO-d6) δ 10.68 (s, 1H), 9.71 (s, 1H), 8.54− 8.49 (m, 1H), 8.48 (s, 1H), 8.36−8.29 (m, 1H), 8.05−8.02 (m, 1H), 7.69 (s, 1H), 7.65 (d, J = 7.9 Hz, 1H), 7.59−7.54 (m, 1H), 7.36−7.32 (m, 1H), 7.31−7.25 (m, 1H), 3.76 (s, 3H), 3.60−3.54 (m, 4H), 3.45−3.38 (m, 5H), 2.78 (d, J = 4.3 Hz, 3H), 2.46−2.37 (m, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 538.2 (MH+), RT = 1.32 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-((pyridin-2-ylmethyl)-carbamoyl)phenyl)amino)-N-methylnicotinamide (29). Prepared from 3-(2-chloro-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoic acid using similar procedures as described for the preparation of 17 and using 2-amino-4-methyl-5-fluoropyridine in place of 2-amino-5-fluoropyridine and pyridin-2-ylmethanamine in place of ammonium chloride to afford 11.2 mg of 29. 1H NMR (500 MHz, DMSO-d6) δ 10.72 (s, 1H), 9.72 (br s, 1H), 9.02 (br t, J = 5.8 Hz, 1H), 8.53 (br dd, J = 11.3, 4.6 Hz, 2H), 8.49 (s, 1H), 8.05 (s, 1H), 7.83−7.78 (m, 1H), 7.70 (br s, 1H), 7.67 (br d, J = 7.9 Hz, 1H), 7.57 (br d, J = 4.9 Hz, 1H), 7.42 (d, J = 7.3 Hz, 1H), 7.37 (br d, J = 6.7 Hz, 1H), 7.33−7.26 (m, 2H), 4.61 (d, J = 5.5 Hz, 2H), 3.75 (s, 3H), 2.79 (d, J = 4.3 Hz, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 516.2 (MH+), RT = 1.44 min. Preparation of 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2methoxy-3-(1,3,4-oxadiazol-2-yl)phenyl)amino)-N-methylnicotinamide (30). Intermediate 3-((2-((5-fluoropyridin-2-yl)amino)-5(methylcarbamoyl)pyridin-4−5-yl)amino)-2-methoxybenzoic acid (60 mg, 0.141 mmol) from the preparation of 22, Hunig’s base (0.074 mL, 0.423 mmol), and tert-butyl hydrazinecarboxylate (22.4 mg, 0.169 mmol) was stirred in DMF (0.6 mL) for a few minutes at room temperature, then (benzotriazol-1- yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP, 81 mg, 0.183 mmol) was added. After stirring the resulting slurry at room temperature for 1 h, the reaction mixture was slowly diluted with water (∼3 mL), and the resulting suspension was sonicated briefly and the precipitated solid was collected by vacuum filtration and dried under vacuum to afford 64 mg (84%) of tert-butyl 2-(3-(2-(5-fluoro-4-methylpyridin-2ylamino)-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoyl)-hydrazinecarboxylate as a light-tan solid. LCMS (E+) m/z: 540.2 (MH+). To a slurry of tert-butyl 2-(3-(2-(5-fluoro-4-methylpyridin-2ylamino)-5-(methylcarbamoyl)pyridin-4-ylamino)-2-methoxybenzoyl)-hydrazinecarboxylate (64 mg, 0.119 mmol) in dichloromethane (0.5 mL) was added trifluoroacetic acid (0.18 mL, 2.4 mmol) to give a clear solution This mixture was stirred at room temperature for 1 h then was concentrated and redissolved in DCM (10 mL). The solution was reconcentrated, and the process was repeated one additional time to remove residual trifluoroacetic acid. The resulting material was triturated with ether (2 × 5 mL) to give an oil, which foamed and solidified under vacuum to afford 55 mg of 6-(5-fluoro-4methylpyridin-2-ylamino)-4-(3-(hydrazinecarbonyl)-2-methoxypheO



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flask was evacuated and supplied with hydrogen gas from a balloon for 3 h. After the reaction was complete, the hydrogen balloon was removed and the flask was flushed with nitrogen before adding 50 mL of additional ethanol. The mixture was filtered to remove the catalyst, and the resulting clear filtrate was concentrated to afford 120 mg (92%) of a ∼4:1 isomeric mixture of 2-methoxy-3-(1-methyl-1Hpyrazol-3-yl)aniline and 2-methoxy-3-(1-methyl-1H-pyrazol-5-yl)aniline, respectively. LCMS (E+) m/z: 204 (MH+). To a solution of 4,6-dichloro-N-methylnicotinamide62 (110 mg, 0.54 mmol) and a ∼4:1 isomeric mixture of 2-methoxy-3-(1-methyl1H-pyrazol-3-yl)aniline and 2-methoxy-3-(1-methyl-1H-pyrazol-5-yl)aniline (120 mg, 0.59 mmol) in DMA (1 mL) was added a solution of lithium bis(trimethylsilyl)amide (1 M in THF, 1.34 mL, 1.34 mmol) dropwise via syringe at room temperature over ∼5 min. After stirring for ∼30 min at room temperature, additional lithium bis(trimethylsilyl)amide (1 M in THF, 0.6 mL, 0.6 mmol) was added and the mixture was stirred for an additional 30 min. Water was then added, and the resulting mixture was concentrated to remove most of the volatiles. The resulting aqueous solution was acidified to a pH of ∼4 by slowly adding 1N aq HCl dropwise with stirring, causing a solid to precipitate from solution. The resulting slurry was stirred at room temperature for ∼1 h. The resulting solid was collected by vacuum filtration, rinsed with water, and dried to afford 155 mg (78%) of a tan solid as a ∼4:1 isomeric mixture of 6-chloro-4-(2-methoxy-3-(1methyl-1H-pyrazol-3-yl)phenylamino)-N-methylnicotinamide and 6chloro-4-(2-methoxy-3-(1-methyl-1H-pyrazol-5-yl)phenylamino)-Nmethylnicotinamide, respectively. LCMS m/z: 204 (MH+) for both isomers. A ∼4:1 isomeric mixture of 6-chloro-4-(2-methoxy-3-(1-methyl1H-pyrazol-3-yl)phenylamino)-N-methylnicotinamide and 6-chloro4-(2-methoxy-3-(1-methyl-1H-pyrazol-5-yl)phenylamino)-N-methylnicotinamide (25 mg, 0.067 mmol), 5-fluoro-4-methylpyridin-2-amine (12.7 mg, 0.10 mmol), cesium carbonate (43.8 mg, 0.134 mmol), and 2-(dicyclohexylphosphino)-3,6-dimethoxy-2′,4′,6′-triisopropyl-l, I′-biphenyl (BrettPhos, 5.4 mg, 10.1 μmol) in dioxane (0.5 mL) was sparged with nitrogen for 5 min, then Pd2(dba)3 (9.2 mg, 10.1 μmol) was added and the reaction was placed into a preheated 110 °C heating block for 1 h. The reaction was cooled to room temperature, diluted with DMSO, filtered, and subjected to purification by reverse phase preparative LCMS with the following conditions: column, XBridge C18, 19 mm × 200 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10-mM ammonium acetate. Gradient: 25−65% B over 20 min, then a 0 min hold at 100% B. Flow: 20 mL/ min. Fractions containing the resolved isomeric products were combined and dried via centrifugal evaporation to afford 13.2 mg (40%) of the major isomer 32 and 3.0 mg (9%) of the minor isomer 33. Data for the Major Isomer 32. 1H NMR (500 MHz, DMSO-d6) δ 10.79−10.59 (m, 1H), 9.68 (s, 1H), 8.49 (d, J = 4.9 Hz, 1H), 8.48 (s, 1H), 8.04 (s, 1H), 7.77 (d, J = 1.8 Hz, 1H), 7.72 (s, 1H), 7.63−7.55 (m, 2H), 7.49 (d, J = 1.9 Hz, 1H), 7.23 (t, J = 1.9 Hz, 1H), 6.73 (d, J = 2.4 Hz, 1H), 3.91 (s, 3H), 3.64−3.58 (m, 3H), 2.79 (d, J = 4.3 Hz, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 462.2 (MH+), RT = 1.66 min. Data for the Minor Isomer 33. 1H NMR (500 MHz, DMSO-d6) δ 10.76 (s, 1H), 9.85 (br s, 1H), 8.56 (br s, 1H), 8.47 (s, 1H), 8.09 (s, 1H), 7.67 (d, J = 8.5 Hz, 2H), 7.51 (s, 2H), 7.32 (t, J = 1.6 Hz, 1H), 7.07 (d, J = 7.3 Hz, 1H), 6.38 (s, 1H), 3.69 (s, 3H), 3.47 (br s, 3H), 2.78 (d, J = 3.7 Hz, 3H), 2.25 (s, 3H). LCMS (E+) m/z: 462.2 (MH+), RT = 1.65 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(1H1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (34). A slurry of 22 (25 mg, 0.06 mmol) in DMF-DMA (1.5 mL, 11.2 mmol) was heated to 110 °C, giving a clear solution initially then eventually becoming a heterogeneous slurry after stirring at this temperature for 30 min. The resulting mixture was then cooled slightly and concentrated to remove the DMF-DMA to afford a solid which was dried further under vacuum. To this residue was added acetic acid (0.12 mL) and ethanol (0.6 mL), giving a clear solution which was immediately by cooled in a −10 °C brine/ice bath, giving a

nylamino)-N-methylnicotinamide as a pale-yellow solid. LCMS (E+) m/z: 440.2 (MH+). A portion of 6-(5-fluoro-4-methylpyridin-2-ylamino)-4-(3-(hydrazinecarbonyl)-2-methoxyphenylamino)-N-methylnicotinamide from the previous step (15 mg, 0.027 mmol) was dissolved in trimethoxymethane (144 mg, 1.36 mmol) and was heated to 105 °C for 2 h using a preheated heating block. The reaction mixture was concentrated to remove excess trimethoxymethane, diluted with DMF (∼1 mL), filtered, and was purified by preparative reverse phase LCMS with the following conditions: column, Waters XBridge C18, 19 mm × 200 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Gradient: 15−100% B over 20 min, then a 5 min hold at 100% B. Flow: 25 mL/ mins. Fractions containing the desired product were combined and dried via centrifugal evaporation to afford 7.2 mg (59%) of 30. 1H NMR (500 MHz, DMSO-d6) δ 10.83 (s, 1H), 9.75 (br s, 1H), 9.41 (s, 1H), 8.59−8.53 (m, 1H), 8.50 (s, 1H), 8.07 (s, 1H), 7.82 (d, J = 7.4 Hz, 1H), 7.78−7.68 (m, 1H), 7.63 (br d, J = 7.4 Hz, 1H), 7.60− 7.51 (m, 1H), 7.43 (t, J = 7.9 Hz, 1H), 3.79 (s, 3H), 2.79 (d, J = 4.4 Hz, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 450.2 (MH+), RT = 1.40 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(5methyl-1,3,4-oxadiazol-2-yl)phenyl)amino)-N-methylnicotinamide (31). Prepared using similar procedures as described for the preparation of 30 and using trimethoxyorthoacetate in place of trimethoxymethane to afford 7.5 mg (59%) of 31. 1H NMR (500 MHz, DMSO-d6) δ 10.82 (s, 1H), 9.73 (s, 1H), 8.53 (br d, J = 4.4 Hz, 1H), 8.50 (s, 1H), 8.06 (s, 1H), 7.79 (d, J = 7.7 Hz, 1H), 7.73 (s, 1H), 7.57 (br d, J = 6.7 Hz, 2H), 7.41 (t, J = 8.1 Hz, 1H), 3.78 (s, 3H), 2.79 (d, J = 4.4 Hz, 3H), 2.60 (s, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 464.2 (MH+), RT = 1.46 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(1methyl-1H-pyrazol-3-yl)phenyl)amino)-N-methylnicotinamide (32) and 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(1methyl-1H-pyrazol-5-yl)phenyl)amino)-N-methylnicotinamide (33). A slurry of l-(2-methoxy-3-nitrophenyl)ethanone88 (450 mg, 2.306 mmol) in Ν,Ν-dimethylformamide dimethyl acetal (DMFDMA, 8.15 g, 68.4 mmol) was heated to 80 °C, giving a clear solution. After stirring at this temperature for ∼30 min, the reaction was cooled, diluted with 100 mL of ethyl acetate, washed with water (3×), then brine, dried over anhydrous sodium sulfate, filtered, and concentrated to afford 432 mg of a tan oil. This material was dissolved in ethanol (4.0 mL) and was cooled in an ice bath, then hydrazine hydrate (0.22 mL, 6.9 mmol) was added dropwise with good stirring. After the addition was complete, the reaction was allowed to warm to room temperature and stirred overnight (∼16 h). The resulting mixture was concentrated to remove the ethanol, diluted with 100 mL of ethyl acetate, washed with water (3×), then brine, dried over sodium sulfate, filtered, and concentrated to afford a tan semisolid. To this material was added 4 mL of acetone and potassium carbonate (956 mg, 6.92 mmol), and the resulting mixture was stirred at room temperature for 10 min before adding iodomethane (0.577 mL, 9.22 mmol) dropwise. After stirring the reaction mixture at room temperature overnight, the mixture was concentrated and was partitioned between ethyl acetate and water. The layers were separated, and the organic portion was washed with water (3×), dried over sodium sulfate, filtered, and concentrated under vacuum to afford tan oil. This material was purified by flash silica gel chromatography using hexanes/ethyl acetate mixtures as the eluent. Fractions containing the major uv active component were combined and concentrated under vacuum to afford 155 mg (29% overall yield) of a ∼4:1 isomeric mixture of 3-(2-methoxy-3nitrophenyl)-1-methyl-1H-pyrazole and 5-(2-methoxy-3-nitrophenyl)-1-methyl-1H-pyrazole, respectively, which was used directly in the next reaction. LCMS (E+) m/z: 235 (MH+). To a solution of a ∼4:1 isomeric mixture of 3-(2-methoxy-3nitrophenyl)-1-methyl-1H-pyrazole and 5-(2-methoxy-3-nitrophenyl)-1-methyl-1H-pyrazole (0.15 g, 0.643 mmol) in ethanol (10 mL) was added 10% palladium on carbon (0.021 g, 0.019 mmol), and the P



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slurry. At this time, 60 μL (∼10 equiv) of hydrazine hydrate was added dropwise via syringe with good stirring to afford light-pink slurry. After addition was complete, the reaction was slowly heated to 60 °C and stirring was continued for 2 h. The reaction mixture was then cooled to room temperature and allowed to stir overnight. The reaction mixture was diluted with ∼2 mL of DMSO and was subjected to reverse phase preparative LCMS purification with the following conditions: column, Waters XBridge C18, 19 mm × 200 mm, 5 μm particles. Mobile phase A: 5:95 acetonitrile:water with 10 mM ammonium acetate. Mobile phase B: 95:5 acetonitrile:water with 10 mM ammonium acetate. Gradient: 10−100% B over 25 min, then a 5 min hold at 100% B. Flow: 25 mL/min. Fractions containing the major product were combined and dried via centrifugal evaporation to afford 8.6 mg (33%) of 34. 1H NMR (500 MHz, DMSO-d6) δ 10.73 (s, 1H), 9.71 (s, 1H), 8.54 (br d, J = 3.7 Hz, 1H), 8.49 (s, 1H), 8.29 (br s, 1H), 8.04 (s, 1H), 7.70 (s, 1H), 7.68−7.61 (m, 3H), 7.58 (br d, J = 4.9 Hz, 1H), 7.34 (br t, J = 7.9 Hz, 1H), 3.69 (s, 3H), 2.79 (br d, J = 3.8 Hz, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 449.2 (MH+), RT = 1.25 min. 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(5methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (35). Prepared from 22 using a similar procedure as described for the preparation of 34 and using N,N-dimethylacetamide dimethyl acetal in place of DMF-DMA to afford 12.3 mg (34%) of 35. 1H NMR (400 MHz, methanol-d4) δ 8.43 (s, 1H), 7.99 (s, 1H), 7.74 (d, J = 7.7 Hz, 2H), 7.64 (br s, 1H), 7.44−7.31 (m, 2H), 3.79 (s, 3H), 3.00 (s, 3H), 2.54 (s, 3H), 2.34 (s, 3H). LCMS (E+) m/z: 463.4 (MH+), RT = 0.66 min (condition C). 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(4methyl-4H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (36). Prepared from 22 using a similar procedure as described for the preparation of 34 and using N,N-dimethylacetamide dimethyl acetal in place of DMF-DMA and N-methyl hydrazine in place of hydrazine hydrate to afford 4.8 mg (10%) of 36. 1H NMR (400 MHz, methanold4) δ 8.40 (s, 1H), 7.99 (d, J = 1.1 Hz, 1H), 7.84 (dd, J = 8.1, 1.6 Hz, 1H), 7.74 (s, 1H), 7.40 (t, J = 7.9 Hz, 1H), 7.31 (d, J = 5.5 Hz, 1H), 7.26 (dd, J = 7.7, 1.6 Hz, 1H), 3.76 (s, 3H), 3.58 (s, 3H), 2.94 (s, 3H), 2.43 (s, 3H), 2.33 (s, 3H). LCMS (E+) m/z: 477.4 (MH+), RT = 0.68 min (condition C). 6-((4,5-Dimethylpyridin-2-yl)amino)-4-((2-methoxy-3-(1-methyl1H-1,2,4-triazol-5-yl)phenyl)amino)-N-methylnicotinamide (37). Prepared from 22 using a similar procedure as described for the preparation of 34 and using N-methyl hydrazine in place of hydrazine hydrate to afford 15 mg (42%) of 37. 1H NMR (400 MHz, methanold4) δ 8.43 (s, 1H), 8.11 (s, 1H), 8.01 (br s, 1H), 7.88 (d, J = 7.7 Hz, 1H), 7.78 (s, 1H), 7.43 (t, J = 7.8 Hz, 1H), 7.34 (d, J = 5.5 Hz, 1H), 7.29 (d, J = 7.7 Hz, 1H), 3.86 (s, 3H), 3.59 (s, 3H), 2.97 (s, 3H), 2.35 (s, 3H). LCMS (E+) m/z: 463.1 (MH+). RT = 0.69 min (condition C). 6-((5-Fluoro-4-methylpyridin-2-yl)amino)-4-((2-methoxy-3-(1methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (38). Prepared from 3-((2-chloro-5-(methylcarbamoyl)pyridin-4-yl)amino)-2-methoxybenzoic acid by amide formation using a similar procedure as described in the preparation of 17 to afford 4-((3carbamoyl-2-methoxyphenyl)amino)-6-chloro-N-methylnicotinamide. Reaction of 4-((3-carbamoyl-2-methoxyphenyl)amino)-6-chloro-Nmethylnicotinamide with DMF-DMA followed by hydrazine hydrate using a similar procedure as described for the preparation of 34 afforded 6-chloro-4-((2-methoxy-3-(1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide. Methylation of 6-chloro-4-((2-methoxy-3-(1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide using a similar procedure as described for the preparation of 50 afforded 6-chloro-4-((2-methoxy-3-(1-methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methyl-nicotinamide. Final coupling of 6-chloro-4((2-methoxy-3-(1-methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-Nmethylnicotinamide with 2-amino-4-methyl-5-fluoropyridine using a similar procedure as described for the preparation of 32 and 33 afforded 38. 1H NMR (500 MHz, DMSO-d6) δ 10.70 (s, 1H), 9.70 (br s, 1H), 8.55 (s, 1H), 8.51 (br s, 1H), 8.48 (s, 1H), 8.06 (s, 1H), 7.78−7.68 (m, 1H), 7.65−7.57 (m, 2H), 7.53 (br d, J = 7.3 Hz, 1H),

7.28 (t, J = 7.9 Hz, 1H), 3.95 (s, 3H), 3.74 (s, 3H), 2.81−2.77 (m, 3H), 2.24 (s, 3H). LCMS (E+) m/z: 463.2 (MH+), RT = 1.32 min. 6-((5-Cyanopyridin-2-yl)amino)-4-((2-methoxy-3-(1-methyl-1H1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (39). Prepared using similar procedures as described for the preparation of 38 by using 2-amino-5-cyanopyridine in place of 2-amino-4-methyl-5fluoropyridine to afford 4.2 mg of 39. 1H NMR (400 MHz, methanold4) δ 8.54−8.51 (m, 2H), 8.45 (s, 1H), 7.91 (dd, J = 8.8, 2.4 Hz, 1H), 7.78 (s, 1H), 7.71−7.70 (m, 1H), 7.68 (d, J = 1.1 Hz, 1H), 7.64 (dd, J = 7.9, 1.5 Hz, 1H), 7.35 (t, J = 7.9 Hz, 1H), 4.06 (s, 3H), 3.77 (s, 3H), 2.96 (s, 3H). LCMS (E+) m/z: 456.0 (MH+), RT = 0.64 min (condition C). 4-((2-Methoxy-3-(1-methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)N-methyl-6-((5-(trifluoromethyl)pyridin-2-yl)amino)nicotinamide (40). Prepared using similar procedures described for the preparation of 38 by using 2-amino-5-trifluoromethylpyridine in place of 2-amino5-fluoropyridine to afford 6.9 mg of 40. 1H NMR (400 MHz, methanol-d4) δ 8.51 (s, 1H), 8.47−8.45 (m, 1H), 8.45 (s, 1H), 7.89 (dd, J = 8.7, 2.3 Hz, 1H), 7.82 (s, 1H), 7.74−7.62 (m, 3H), 7.34 (t, J = 7.9 Hz, 1H), 4.06 (s, 3H), 3.78 (s, 3H), 2.97 (s, 3H). LCMS (E+) m/z: 499.0 (MH+). RT = 0.73 min (condition C). 6-((2,6-Dimethylpyrimidin-4-yl)amino)-4-((2-methoxy-3-(1methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (41). Prepared using similar procedures described for the preparation of 38 by using 2,6-dimethylpyrimidin-4-amine in place of 2-amino-5fluoropyridine to afford 13 mg of 41. 1H NMR (400 MHz, methanold4) δ 8.50 (s, 1H), 8.49 (s, 1H), 7.72 (br d, J = 7.9 Hz, 1H), 7.60 (d, J = 7.9 Hz, 1H), 7.33 (t, J = 7.9 Hz, 1H), 4.02 (s, 3H), 3.73 (s, 3H), 2.95 (s, 3H), 2.59 (s, 3H), 2.47 (s, 3H). LCMS (E+) m/z: 460.3 (MH+). RT = 0.53 min (condition C). Preparation of 6-(Cyclopropanecarboxamido)-4-((2-methoxy-3(1-methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylnicotinamide (42). Prepared by a sequential coupling of 2-methoxy-3-(1methyl-1H-1,2,4-triazol-3-yl)aniline (52) and cyclopropylamide (55) to 4,6-dichloro-N-methylnicotinamide62 using similar procedures as described in the preparation of 11 to afford 17.8 mg (36% over 2 steps) of 42 as an off-white solid. 1H NMR (400 MHz, methanol-d4) δ 8.54 (s, 1H), 8.38 (s, 1H), 7.83 (dd, J = 7.9, 1.5 Hz, 1H), 7.59 (dd, J = 7.9, 1.5 Hz, 1H), 7.38 (t, J = 7.9 Hz, 1Η), 6.94 (br s, 1H), 4.06 (d, J = 0.4 Hz, 3H), 3.75 (s, 3H), 2.98 (s, 3H), 1.87−1.76 (m, 1H), 1.15− 1.07 (m, 2H), 1.06−0.97 (m, 2H). LCMS (E+) m/z: 422.2 (MH+), RT = 0.57 min (condition C). 6-(Cyclopropanecarboxamido)-4-((2-methoxy-3-(1-methyl-1H1,2,4-triazol-3-yl)phenyl)amino)-N-(methyl-d3-nicotinamide (43). Prepared by a sequential coupling of 2-methoxy-3-(1-methyl-1H1,2,4-triazol-3-yl)aniline (52) and cyclopropylamide to 5362 using similar procedures as described in the preparation of 11 to afford 26.3 mg (60% over 2 steps) of 43 as an off-white solid. 1H NMR (500 MHz, DMSO-d6) δ 10.71 (br s, 1H), 10.61 (br s, 1H), 8.58 (br s, 1H), 8.52 (br s, 1H), 8.48 (br s, 1H), 8.03 (br s, 1H), 7.62−7.42 (m, 2H), 7.22 (t, J = 7.4 Hz, 1H), 3.93 (br s, 3H), 3.69 (br s, 3H), 2.01− 1.88 (m, 1H), 0.85−0.69 (m, J = 4.4 Hz, 4H). LCMS (E+) m/z: 425.3 (MH+), RT = 1.09 min. 2-Methoxy-3-nitrobenzamide (48). To a solution of 10 g (51 mmol) of commercially available methyl 2-hydroxy-3-nitrobenzoate (47) in DMF (100 mL) at room temperature was added potassium carbonate (14 g, 101 mmol) followed by addition of methyl iodide (6.34 mL, 101 mmol), and the resulting orange mixture was heated to 60 °C for 1 h. LCMS analysis at this time showed complete and clean conversion to a major product consistent with the expected product (observed MH+ 212). The reaction mixture was allowed to cool to room temperature and crushed ice (∼100 mL) was added followed by water to a total volume of ∼400 mL, causing a yellow solid to crystallize from the solution. The solution was stirred for a few minutes to give a slurry, then the solid was collected by vacuum filtration. The resulting solid was rinsed with additional water (∼100 mL) to afford a white solid, which was partially air-dried then transferred to a round-bottom flask and further dried under vacuum overnight to afford 10.5 g (98%) of a pale-yellow solid as the intermediate methyl 2-methoxy-3-nitrobenzoate. 1H NMR (400 MHz, CDCl3) δ 8.04 (dd, J = 7.9, 1.8 Hz, 1H), 7.92 (dd, J = 8.1, Q



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1.8 Hz, 1H), 7.31−7.28 (m, 1H), 4.02 (s, 3H), 3.97 (s, 3H). LCMS (E+) m/z: 212 (MH+), RT = 0.83 min. Methyl 2-methoxy-3-nitrobenzoate (11 g, 52 mmol) was dissolved in a cold solution of ammonia in methanol (7 N, 250 mL), and concentrated aqueous ammonium hydroxide (100 mL) was added. The flask was sealed, and the resulting solution was allowed to gently stir at room temperature overnight (∼17 h). The reaction mixture was concentrated in vacuo under mild warming using a water bath to yield an aqueous slurry. This slurry was diluted with additional water (∼300 mL) and was briefly sonicated. The resulting yellow solid was collected by vacuum filtration and was rinsed with additional water (∼100 mL) and air-dried in the funnel for several hours then under vacuum to afford 7.12 g of 48 as a yellow solid. A second crop was obtained by extracting the filtrate with ethyl acetate (3 × 100 mL), followed by washing the extracts with brine, drying over anhydrous sodium sulfate, decanting, and concentration under vacuum to afford 1.67 g of additional 48 as a yellow solid (86% overall combined yield). LCMS (E+) m/z: 197 (MH+), RT = 0.58 min. 3-(2-Methoxy-3-nitrophenyl)-1H-1,2,4-triazole (49). A slurry of 48 (7.1 g, 36 mmol) in dimethylformamide dimethyl acetal (DMFDMA, 48.5 mL, 362 mmol) was heated to 95 °C. giving a clear, paleyellow solution. After heating for ∼30 min at this temperature, the reaction was cooled and concentrated in vacuo. The resulting yellow oil was azeotroped twice with 1,2-dichloroethane (40 mL portions) to ensure complete removal of any residual DMF-DMA. The oil containing the crude DMF-DMA adduct was dissolved in 35 mL of ethanol and was immediately used in the following step. In a separate flask was prepared a mixture of ethanol (150 mL) and acetic acid (35 mL), and the resulting solution was cooled in an ice bath. Once cooled, hydrazine hydrate (17.6 mL, 362 mmol) was added dropwise, followed by a dropwise addition of the previously prepared ethanol solution of the crude DMF-DMA adduct via cannula over ∼15 min with stirring. During the addition, a pale-yellow solid formed in the solution. After the addition was complete, the resulting cloudy yellow mixture was allowed to warm to room temperature and stir for ∼4 h. The reaction mixture was concentrated in vacuo to remove the ethanol, diluted with additional water, and filtered to collect the solid. The solid was washed with additional portions of water and was airdried in the funnel, then under vacuum to afford 5.5 g (69%) of 49 as a pale-yellow solid. LCMS (E+) m/z: 221 (MH+), RT = 0.61 min. 3-(2-Methoxy-3-nitrophenyl)-1-methyl-1H-1,2,4-triazole (50). A solution of 49 (2.2 g, 10.1 mmol) in DMF (20 mL) was treated with potassium carbonate (4.2 g, 30 mmol). After cooling, the resulting mixture in an ice bath, and a solution of iodomethane (0.86 mL, 13.7 mmol) in DMF (5 mL) was slowly added dropwise by syringe over 2 min. After the addition was complete, the ice bath was removed and the reaction mixture was allowed to warm to room temperature. After stirring at room temperature for ∼4 h, LCMS analysis indicated complete and clean conversion to a regioisomeric mixture of products in ∼2:1 ratio. The reaction was cooled in an ice bath and was diluted with water (∼ 50 mL), and the solution was extracted with ethyl acetate (3 × 40 mL) and the combined extracts were washed with 10% aq lithium chloride (2 × 20 mL), water (20 mL), then brine before concentrating to afford 2.2 g (91%) of a yellow oil as the crude product, which solidified to a yellow solid upon standing. This crude material was combined with another batch of additional crude product (∼0.45 g) obtained from a previous similar reaction using 49, and the combined material was purified by SFC to resolve the isomers [conditions: column = chiral IC 3 cm 5 cm, 5 μm; column temp = 35 °C; flow rate = 200 mL/min; mobile phase = CO2/MeOH = 80/20; injection program = stacked (2.3 min/cycle), 2.5 mL/per injection; sampler conc (mg/mL), 60 mg/mL; detector wavelength = 220 nm] to afford 1.87 g (66%) of the major isomer 50 as a pale-yellow solid and 0.7 g (25%) of the minor isomer 51 as a pale-yellow oil. Data for major (desired) isomer 50: 1H NMR (400 MHz, methanol-d4: δ 8.50 (s, 1H), 8.11 (dd, J = 7.9, 1.8 Hz, 1H), 7.85 (dd, J = 8.1, 1.8 Hz, 1H), 7.38 (t, J = 8.0 Hz, 1H), 4.03 (s, 3H), 3.83 (s, 3H). LCMS (E+) m/z: 235 (MH+), RT = 0.74 min. Alternative Conditions for Synthesis of 50. To a yellow suspension of 49 (49.3 g, 224 mmol) in THF (1000 mL) under

nitrogen at room temperature was added a 1 M solution of potassium bis(trimethylsilyl)amide in THF (269 mmol) dropwise over 20 min. During the addition, the reaction turned dark-red to ultimately darkbrown in color. The temperature of the reaction at the end of addition was 27 °C. The reaction was left to stir at room temperature for 4 h, then methyl iodide (28.0 mL, 448 mmol) was added dropwise over a period of 15 min. The reaction was then left to stir at room temperature overnight. After 20 h, the reaction was checked by LCMS, indicating complete conversion had occurred. The reaction was then slowly quenched with water (350 mL) and ethyl acetate (650 mL) was added. The layers were partitioned in a separatory funnel. The organic layer was washed with brine (200 mL) and then dried over solid magnesium sulfate. Filtration and concentrating afforded 49 g (93%) of a crude yellow oil that solidified upon standing. The crude solid was then suspended in 30−40 mL of ethanol and warmed slowly to 45 °C with a heating mantle. Once all the solid has dissolved, the heat was shut off and the solution was allowed to slowly cool. When the solution reached 30 °C, it was seeded to initiate crystallization. The mixture was stirred for 1 h at room temperature, then the slurry was filtered through Whatman 2 filter paper to collect the crystalline solid. The filter cake was washed with cold (−30 °C) ethanol and was dried under vacuum overnight to afford 12 g (51.3 mmol, 23%) of the major isomer 50 as an off-white solid. The mother liquor from the filtration was concentrated, and the crystallization step was repeated with stirring overnight. Filtration and drying the collected crystalline solid afforded an additional 8.38 g (35.8 mmol, 16%) of the major isomer 50 as an off-white solid. The mother liquor was once again concentrated to an oil (29.3 g) and purified on an Isco RediSep Silica 1.5 kg Gold column. The isomers were eluted with a gradient of 100% A for 1 column volume then to 18% B over 10 column volumes where A = dichloromethane and B = 80/20 dichloromethane/methanol to afford 20.38 g of an isomeric mixture. The material was then purified by SFC using previously described conditions to yield an additional 10 g (19%) of 50 as a white solid. 2-Methoxy-3-(1-methyl-1H-1,2,4-triazol-3-yl)aniline (52). A solution of 50 (1.87 g, 7.98 mmol) in ethanol (50 mL) was sparged with nitrogen for a few minutes and charged with 5% Pd-C (0.85 g, 0.40 mmol). The reaction mixture was then sparged with hydrogen from a balloon for a few minutes and allowed to stir under a balloon of hydrogen for 1.5 h at room temperature. The mixture was then sparged with nitrogen to deactivate the catalyst and the mixture was filtered through a pad of diatomaceous earth washing with additional amounts of ethanol, and the resulting clear, colorless filtrate containing the product was concentrated under vacuum to afford a colorless oil. This material was azeotroped with two portions of dry toluene (∼25 mL each) to afford an off-white solid which was dried further under vacuum to afford 1.5 g (92%) of 52 as a free-flowing white solid. 1H NMR (400 MHz, CDCl3) δ 8.09 (s, 1H), 7.35 (dd, J = 7.8, 1.7 Hz, 1H), 7.00 (t, J = 7.8 Hz, 1H), 6.82 (dd, J = 7.8, 1.7 Hz, 1H), 4.00 (s, 3H), 3.94 (br s, 2H), 3.78 (s, 3H). LCMS (E+) m/z: 205 (MH+), RT = 0.44 min. 6-Chloro-4-((2-methoxy-3-(1-methyl-1H-1,2,4-triazol-3-yl)phenyl)amino)-N-methylpyridazine-3-carboxamide (54). To a solution of 52 (10.26 g, 50.2 mmol) and 5362 (10.5 g, 50.2 mmol) in THF (120 mL) was added a 1 M solution of lithium bis(trimethylsilyl)amide in THF (151 mL, 151 mmol) in a dropwise manner using a pressure equalized addition funnel. The reaction was run for 10 min after the completion of the addition and then quenched with HCl (1 M aq, 126 mL, 126 mmol). The reaction was concentrated in vacuo until the majority of the THF was removed and a precipitate prevailed throughout the vessel. Water (∼500 mL) was then added, and the slurry was sonicated for 5 min and stirred for 15 min. The solid was collected by vacuum filtration, rinsed with water, and then air-dried for 30 min. The powder was collected and dissolved in dichloromethane. The organic layer was washed with water and brine and then dried over sodium sulfate, filtered, and concentrated to provide 12.5 g (66%) of 54 as a pale-yellow solid. 1H NMR (400 MHz, DMSO-d6) δ 11.11 (s, 1H), 9.36 (s, 1H), 8.56 (s, 1H), 7.72 (dd, J = 7.8, 1.6 Hz, 1H), 7.60 (dd, J = 7.9, 1.5 Hz, 1H), R



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7.29 (t, J = 7.9 Hz, 1H), 7.19 (s, 1H), 3.95 (s, 3H), 3.72 (s, 3H). LCMS (E+) m/z: 377 (MH+), RT = 0.83 min. IL-23-Induced Acanthosis in Mice. Acanthosis was induced in 6−8-week-old C57BL/6 female mice (19−20 g average weight, Jackson Laboratories) by intradermal injection of dual chain, recombinant human IL-23 into the right ear. IL-23 injections were administered every other day from day 0 through day 9 of the study. Treatment groups consisted of eight mice per group. Compound 11 at 7.5, 15, and 30 mg/kg BID in vehicle (EtOH:TPGS:PEG300, 5:5:90) and vehicle alone dosed BID by oral gavage, with the first dose given the evening before the first IL-23 injection. An anti-IL-23 adnectin (3 mg/kg) and PBS control were administered subcutaneously approximately 1 h prior to the first IL-23 injection and then twice a week thereafter. Ear thickness was measured using a Mitutoyo (no. 2412F) dial caliper and calculated as the percent change in thickness from the baseline measurement taken on day 0 before initial IL-23 injections for each animal. At the end of the study, IL-23̈ control ears were collected from four injected ears as well as naive animals per group for histological examination and gene expression analyses. Terminal blood samples collected via the retro-orbital sinus were used for PK determinations. Statistical analyses were performed using Student’s t tests or ANOVA with Dunnett’s post test. At the end of the study, ears were removed and fixed in 10% neutral-buffered formalin for 24−48 h. The fixed ears were then cut longitudinally, and two pieces were parallel embedded to make the paraffin blocks. The paraffin blocks were then sectioned and placed on microscope slides for H&E staining for histological evaluation. Severity of ear inflammation was scored using an objective scoring system based on the following parameters: extent of the lesion, severity of hyperkeratosis, number and size of pustules, height of epidermal hyperplasia (acanthosis, measured in interfollicular epidermis), and the amount of inflammatory infiltrate in the dermis and soft tissue. The latter two parameters, acanthosis and inflammatory infiltrate, were scored independently on a scale from 0 to 4: 0, none; 1, minimal; 2, mild; 3, moderate; 4, marked. The histological changes were blindly evaluated by a pathologist. Statistical analyses was performed using one-way ANOVA with Dunnett’s test for comparison of each treatment versus the vehicle control. X-ray Crystallography. Protein production and purification of TYK2 JH2 (575-869) was carried out as previously reported.60−62 Cocrystals of TYK2 JH2 in complex with a previously reported BMS compound60 was first grown under conditions similar to that reported earlier.60−62 These cocrystals were subsequently used for soaking inhibitors of interest. Compounds 11, 12, and 29 was soaked into the TYK2 JH2 cocrystals (24 h soak) by adding 5 mM inhibitor (final concentration) to a 10 μL well of harvest mother liquor. Crystals were frozen from mother liquor solution containing 25% glycerol. Structure determination was as described previously.60−62

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AUTHOR INFORMATION

Corresponding Authors

*For S.T.W.: phone, (609)252-4873; E-mail, stephen. [email protected]. *For R.M.: E-mail, [email protected]. ORCID

Stephen T. Wrobleski: 0000-0001-7793-1530 Ryan Moslin: 0000-0002-0332-4778 Steven Spergel: 0000-0002-5190-3942 James Kempson: 0000-0002-9540-3886 Percy H. Carter: 0000-0002-5880-1164 Present Address

For D.W.: Vividion Therapeutics, Inc. 5820 Nancy Ridge Drive, San Diego, CA 92121, United States. Author Contributions

S.W. and R. M. contributed equally to this work. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was funded by Bristol-Myers Squibb Company. We thank Dr. Robert Borzilleri, Dr. Joseph Tino, and Dr. John Hynes Jr., and Dr. Murali Dhar for helpful comments in the writing of this manuscript, Dr. Phil Baran for useful discussions, Dr. Andrew Tebben and Charlotte Raymond for their assistance in the design of the proposed cover art illustration, Sylwia Stachura for assistance in the preparation of analogues, the Synthesis and Analysis Technology Team and the Department of Discovery Synthesis (DDS) including Dr. Dauh-Rurng Wu, Shiuhang Yip, Richard Rampulla, and the Biocon Bristol-Myers Squibb Research and Development Center (BBRC) DDS team for assistance in the synthesis and purification of compounds. Finally, the we acknowledge the beamline staff at the IMCA-CAT beamline 17-ID at the Advanced Photon Source and the CLS 08ID at Canadian Light Source for their support in diffraction data collection.

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ABBREVIATIONS USED TYK2, tyrosine kinase 2; JAK1, Janus kinase 1; JAK2, Janus kinase 2; JAK3, Janus kinase 3; JH1, Janus homology 1; JH2, Janus homology 2; STAT, signal transducer and activator of transcription; pSTAT, phospho signal transducer and activator of transcription; hWB, human whole blood; mWB, mouse whole blood; IC, Inhibitory concentration; nM, nanomolar; μM, micromolar; mM, millimolar; IFN, interferon; IL, interleukin; GM-CSF, granulocyte-macrophage colony-stimulatory factor; EPO, erythropoietin; TPO, thrombopoietin; ATP, adenosine triphosphate; FDA, Food and Drug Administration; RA, rheumatoid arthritis; PSO, psoriasis; PsA, psoriatic arthritis; UC, ulcerative colitis; AS, ankylosing spondylitis; AA, alopecia areata; DLE, discoid lupus erythematosus; SLE, systemic lupus erythematosus; dcSSc, diffuse cutaneous systemic sclerosis; CD, Crohn’s disease; SAEs, significant adverse events; mg, milligram; g, gram; NK, natural killer; LFT, liver function tests; LDL, low density lipoprotein; HDL, high density lipoprotein; CD40, cluster of differentiation 40; compd, compound; HTRF, homogeneous time-resolved fluorescence; SPA, scintillation proximity assay; Th1, T-helper 1; Th17, T-helper 17; SH2, Src homology 2; IBD, inflammatory bowel disease; Pro, proline; Leu, leucine; Asn, asparagine; Lys, lysine; Gln, glutamine; Thr, threonine;; Val,

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jmedchem.9b00444. X-ray crystallographic data and refinement statistics for compounds 11, 12, and 29 in TYK2 JH2 (PDF) Molecular formula strings list (CSV) Accession Codes

Atomic coordinates for the X-ray structures of compound 11 (PDB 6NZP), 12 (PDB 6NZR), and 29 (PDB 6NZQ) in TYK2 JH2 are available from the RCSB Protein Data Bank (www.rscb.org). Authors will release the atomic coordinates upon article publication. S



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valine; Ala, alanine; Arg, arginine; SAR, structure−activity relationships; PSA, polar surface area; Me, methyl; Et, ethyl; s, seconds; min, minute; Pc, permeability coefficient; Å, angstroms; MLM, mouse liver microsomes; HLM, human liver microsomes; Het, heterocycle; hERG, human ether a-gogo-related gene; PK, pharmacokinetic; PEG, polyethylene glycol; Cmax, maximum concentration; CL, clearance; MRT, mean residence time; AUC, area under the curve; F, bioavailability; kcal, kilocalories; BMPR2, bone morphogenetic receptor type 2; PBMC, peripheral blood mononuclear cell; DDI, drug−drug interactions; CYP, cytochrome p450; mL, milliliter; kg, kilogram; Vss, volume of distribution; L, liter; h, hour; A, apical; B, basal; PXR-TA, pregnane X receptor transactivation; EC, efficacious concentration; Aq, aqueous; iv, intravenous administration; po, oral administration; TPGS, tocopheryl polyethylene glycol; PCR, quantitative chain reaction; SCID, severe-combined immunodeficient; IFNαR, interferon-α receptor; ng, nanogram; WB, whole blood; LLQ, lower limit of detection; SEM, standard error of the mean; EtOH, ethanol; mpk, milligrams per kilogram; BID, twice-daily administration; QD, once-daily administration; Ar, aryl; SFC, supercritical fluid chromatography; THF, tetrahydrofuran; DMF, dimethylformamide; DMA, dimethylacetamide; dppf, 1,1′-bis(dicyclohexylphosphino)ferrocene; dba, dibenzylideneacetone; RT, retention times; NMR, nuclear magnetic resonance; LC, liquid chromatography; HPLC, high performance liquid chromatography; HRMS, high resolution mass spectrometer; MHz, megahertz; K, Kelvin; UV, ultraviolet; MS, mass spectrometer; DMSO, dimethyl sulfoxide; br, broad; s, singlet; d, doublet; dd, doublet of doublet; m, multiplet; Hz, hertz; rt, room temperature; conc, concentration; MH+, molecular ion; mmol, millimolar; MPLC, medium pressure liquid chromatography

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