Discovery of the TLR7/8 Antagonist MHV370 for Treatment of Systemic Autoimmune Diseases

Toll-like receptor (TLR) 7 and TLR8 are endosomal sensors of the innate immune system that are activated by GU-rich single stranded RNA (ssRNA). Multiple genetic and functional lines of evidence link chronic activation of TLR7/8 to the pathogenesis of systemic autoimmune diseases (sAID) such as Sjögren's syndrome (SjS) and systemic lupus erythematosus (SLE). This makes targeting TLR7/8-induced inflammation with small-molecule inhibitors an attractive approach for the treatment of patients suffering from systemic autoimmune diseases. Here, we describe how structure-based optimization of compound 2 resulted in the discovery of 34 (MHV370, (S)-N-(4-((5-(1,6-dimethyl-1H-pyrazolo[3,4-b]pyridin-4-yl)-3-methyl-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridin-1-yl)methyl)bicyclo[2.2.2]octan-1-yl)morpholine-3-carboxamide). Its in vivo activity allows for further profiling toward clinical trials in patients with autoimmune disorders, and a Phase 2 proof of concept study of MHV370 has been initiated, testing its safety and efficacy in patients with Sjögren's syndrome and mixed connective tissue disease.

Structure-Based Design of Selective LONP1 Inhibitors for Probing In Vitro Biology

LONP1 is an AAA+ protease that maintains mitochondrial homeostasis by removing damaged or misfolded proteins. Elevated activity and expression of LONP1 promotes cancer cell proliferation and resistance to apoptosis-inducing reagents. Despite the importance of LONP1 in human biology and disease, very few LONP1 inhibitors have been described in the literature. Herein, we report the development of selective boronic acid-based LONP1 inhibitors using structure-based drug design as well as the first structures of human LONP1 bound to various inhibitors. Our efforts led to several nanomolar LONP1 inhibitors with little to no activity against the 20S proteasome that serve as tool compounds to investigate LONP1 biology.

Target-Based Identification and Optimization of 5-Indazol-5-yl Pyridones as Toll-like Receptor 7 and 8 Antagonists Using a Biochemical TLR8 Antagonist Competition Assay

Inappropriate activation of endosomal TLR7 and TLR8 occurs in several autoimmune diseases, in particular systemic lupus erythematosus (SLE). Herein, the development of a TLR8 antagonist competition assay and its application for hit generation of dual TLR7/8 antagonists are reported. The structure-guided optimization of the pyridone hit 3 using this biochemical assay in combination with cellular and TLR8 cocrystal structural data resulted in the identification of a highly potent and selective TLR7/8 antagonist (27) with in vivo efficacy. The two key steps for optimization were (i) a core morph guided by a TLR7 sequence alignment to achieve a dual TLR7/8 antagonism profile and (ii) introduction of a fluorine in the piperidine ring to reduce its basicity, resulting in attractive oral pharmacokinetic (PK) properties and improved TLR8 binding affinity.

Discovery of Orally Active Hydroxyethylamine Based SPPL2a Inhibitors

SPPL2a (Signal Peptide Peptidase Like 2a) is an intramembrane aspartyl protease engaged in the function of B-cells and dendritic cells. Despite being an attractive target for modulation of the immune system, selective SPPL2a inhibitors are barely described in the literature. Recently, we have disclosed a selective, small molecular weight agent SPL-707 which confirmed that pharmacological inhibition of SPPL2a leads to the accumulation of its substrate CD74/p8 and as a consequence to a reduction in the number of B-cells as well as myeloid dendritic cells in mice. In this paper we describe the discovery of novel hydroxyethylamine based SPPL2a inhibitors. Starting from a rather lipophilic screening hit, several iterative optimization cycles allowed for its transformation into a highly potent and selective compound 15 (SPL-410) which inhibited in vivo CD74/p8 fragment processing in mice at 10 mg/kg oral dose.

Identification of Potent and Selective RIPK2 Inhibitors for the Treatment of Inflammatory Diseases

NOD2 (nucleotide-binding oligomerization domain-containing protein 2) is an internal pattern recognition receptor that recognizes bacterial peptidoglycan and stimulates host immune responses. Dysfunction of NOD2 pathway has been associated with a number of autoinflammatory disorders. To date, direct inhibitors of NOD2 have not been described due to technical challenges of targeting the oligomeric protein complex. Receptor interacting protein kinase 2 (RIPK2) is an intracellular serine/threonine/tyrosine kinase, a key signaling partner, and an obligate kinase for NOD2. As such, RIPK2 represents an attractive target to probe the pathological roles of NOD2 pathway. To search for selective RIPK2 inhibitors, we employed virtual library screening (VLS) and structure based design that eventually led to a potent and selective RIPK2 inhibitor 8 with excellent oral bioavailability, which was used to evaluate the effects of inhibition of RIPK2 in various in vitro assays and ex vivo and in vivo pharmacodynamic models.

Overcoming EGFR(T790M) and EGFR(C797S) resistance with mutant-selective allosteric inhibitors

EGFR tyrosine kinase inhibitors (TKIs) gefitinib, erlotinib and afatinib are approved treatments for non-small cell lung cancers harboring activating mutations in the EGFR kinase^1,2, but resistance arises rapidly, most frequently due to the secondary T790M mutation within the ATP-site of the receptor.^3,4 Recently developed mutant-selective irreversible inhibitors are highly active against the T790M mutant^5,6, but their efficacy can be compromised by acquired mutation of C797, the cysteine residue with which they form a key covalent bond⁷. All current EGFR TKIs target the ATP-site of the kinase, highlighting the need for therapeutic agents with alternate mechanisms of action. Here we describe rational discovery of EAI045, an allosteric inhibitor that targets selected drug-resistant EGFR mutants but spares the wild type receptor. A crystal structure shows that the compound binds an allosteric site created by the displacement of the regulatory C-helix in an inactive conformation of the kinase. The compound inhibits L858R/T790M-mutant EGFR with low-nanomolar potency in biochemical assays, but as a single agent is not effective in blocking EGFR-driven proliferation in cells due to differential potency on the two subunits of the dimeric receptor, which interact in an asymmetric manner in the active state⁸. We observe dramatic synergy of EAI045 with cetuximab, an antibody therapeutic that blocks EGFR dimerization^9,10, rendering the kinase uniformly susceptible to the allosteric agent. EAI045 in combination with cetuximab is effective in mouse models of lung cancer driven by L858R/T790M EGFR and by L858R/T790M/C797S EGFR, a mutant that is resistant to all currently available EGFR TKIs. More generally, our findings illustrate the utility of purposefully targeting allosteric sites to obtain mutant-selective inhibitors.

Abstract 2585: Discovery of a potent covalent mutant-selective EGFR inhibitor - the journey from high throughput screening to EGF816

Epidermal growth factor receptor (EGFR) is a validated therapeutic target for lung cancer. First and second generation EGFR inhibitors (e.g., gefitinib, erlotinib and afatinib) have revolutionized treatment paradigms of non-small cell lung cancer (NSCLC) patients with oncogenic EGFR mutations. The use of EGFR tyrosine kinase inhibitors (TKI) provides superior efficacy compared to chemotherapy in patients with EGFR L858R or exon 19 deletion tumors. However, resistance inevitably develops after 8-12 months of treatment; most commonly via a secondary T790M point mutation at the gatekeeper residue of EGFR. Furthermore, responses are hindered due to treatment intolerance in the form of rash and diarrhea that are mediated by simultaneous inhibition of wild-type (WT) EGFR at doses required for mutant EGFR suppression. To overcome these limitations, we initiated a project to identify mutant-selective EGFR inhibitors that potently inhibit both activating and T790M resistance EGFR mutations while sparing WT EGFR.

In this presentation, we report our medicinal chemistry approach and optimization that led to the discovery of EGF816, a selective and potent covalent mutant-selective EGFR inhibitor with single digit nanomolar cellular target modulation on both activating and T790M resistance mutations. In addition, we will also report validated clinical efficacy data from the first patient treated with EGF816.

Citation Format: Gerald Lelais, Robert Epple, Pierre-Yves Michellys, Thomas H. Marsilje, Yun Long, Matthew McNeill, Bei Chen, Wenshuo Lu, Badry Bursulaya, Michael DiDonato, Yong Jia, Shailaja Kasibhatla, Chun Li, Igor Matushansky, Steven Bender. Discovery of a potent covalent mutant-selective EGFR inhibitor - the journey from high throughput screening to EGF816. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2585. doi:10.1158/1538-7445.AM2015-2585

Abstract 1734: In vitro characterization of EGF816, a third-generation mutant-selective EGFR inhibitor

EGFR is a major oncogene in NSCLC. Patients with the oncogenic mutations L858R and Ex19Del are responsive to the first generation pan-EGFR tyrosine kinase inhibitors (TKIs) erlotinib and gefitinib. The associated dose-limiting toxicities (DLTs) are severe rash and GI tolerability due to WT EGFR inhibition. However, therapy is universally limited by the development of acquired drug resistance where EGFR gatekeeper mutation T790M accounts for 50% of incidence. Second generation irreversible pan-EGFR TKI afatinib was developed to overcome T790M resistance. Though effective in animal models, the efficacy of afatinib on T790M patients is largely limited by its DLTs due to potent inhibition of WT EGFR. A strong medical need still exists for better tolerated therapy to treat NSCLC patients harboring EGFR mutations. Here we report the discovery and development of a potent third generation, irreversible mutant-selective EGFR TKI that is expected to improve/maintain efficacy on oncogenic EGFR mutant patients while demonstrating reduced side effects. EGF816 potently inhibits both activating (L858R and Ex19Del) and T790M resistant mutations in various cellular assays; it is selective against a large panel of kinases in both Ambit and BaF3 profiling, and more importantly is selective against WT EGFR. EGF816 is efficacious in mutant EGFR-driven xenograft models, is well tolerated in IND-enabling toxicology studies, and is entering phase 1 trials.

Citation Format: Yong Jia, Jose Juarez, Mari Manuia, Gerald Lelais, Shailaja Kasibhatla, Oliver Long, Matthew McNeill, Michael DiDonato, Badry Bursulaya, Debbie Liao, Eric Murphy, Robert Epple, Thomas Marsilje, Nuzhat Pathan, Pierre-Yves Michellys, Steven Bender, Jennifer Harris. In vitro characterization of EGF816, a third-generation mutant-selective EGFR inhibitor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1734. doi:10.1158/1538-7445.AM2014-1734

Abstract 957: The ALK inhibitor LDK378 overcomes crizotinib resistance in non-small cell lung cancer

Non-small cell lung cancers (NSCLC) harboring anaplastic lymphoma kinase (ALK) gene rearrangements are sensitive to the ALK tyrosine kinase inhibitor (TKI) crizotinib. However, these cancers invariably relapse due to the development of resistance, and approximately 1/3 of such cancers develop resistance mutations within the ALK tyrosine kinase domain. Here we report the preclinical evaluation of the next-generation ALK TKI, LDK378 in the setting of crizotinib resistance. Using EML4-ALK mutant Ba/F3 cellular models, in vivo models of acquired resistance to crizotinib, and novel cell lines established from biopsies of crizotinib-resistant NSCLC patients, we have examined the efficacy of LDK378 in crizotinib-naïve and -resistant ALK-positive cancers. These studies reveal that LDK378 is more potent than crizotinib and effectively overcomes resistance in vitro and in vivo. In particular, LDK378 inhibits ALK harboring crizotinib resistance mutations, including L1196M, G1269A, I1171T and S1206Y. Cell lines derived from crizotinib-resistant biopsies were sensitive to LDK378, including one that did not harbor an ALK resistance mutation and was also sensitive to crizotinib, suggesting that some crizotinib-resistant cancers with wildtype ALK are still sensitive to complete ALK inhibition. We observed that LDK378 did not effectively overcome two crizotinib-resistant ALK mutations, G1202R and F1174C

ALK, and mutations in one of these residues was identified in 5 out of 11 biopsies from patients with acquired resistance to LDK378. Altogether our results demonstrate that LDK378 can overcome many mechanisms of crizotinib resistance, consistent with emerging clinical data showing marked efficacy of LDK378 in patients with crizotinib-resistant disease.

Citation Format: Luc Friboulet, Nanxin Li, Ryohei Katayama, Christian C. Lee, Justin F. Gainor, Adam S. Crystal, Pierre-Yves Michellys, Mark M. Awad, Noriko Yanagitani, Sungjoon Kim, AnneMarie Pferdekamper, Jie Li, Shailaja Kasibhatla, Frank Sun, Xiuying Sun, Su Hua, Peter McNamara, Sidra Mahmood, Elizabeth L. Lockerman, Naoya Fujita, Makoto Nishio, Jennifer L. Harris, Alice T. Shaw, Jeffrey A. Engelman. The ALK inhibitor LDK378 overcomes crizotinib resistance in non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 957. doi:10.1158/1538-7445.AM2014-957

The ALK inhibitor ceritinib overcomes crizotinib resistance in non-small cell lung cancer

Non-small cell lung cancers (NSCLC) harboring anaplastic lymphoma kinase (ALK) gene rearrangements invariably develop resistance to the ALK tyrosine kinase inhibitor (TKI) crizotinib. Herein, we report the first preclinical evaluation of the next-generation ALK TKI, ceritinib (LDK378), in the setting of crizotinib resistance. An interrogation of in vitro and in vivo models of acquired resistance to crizotinib, including cell lines established from biopsies of patients with crizotinib-resistant NSCLC, revealed that ceritinib potently overcomes crizotinib-resistant mutations. In particular, ceritinib effectively inhibits ALK harboring L1196M, G1269A, I1171T, and S1206Y mutations, and a cocrystal structure of ceritinib bound to ALK provides structural bases for this increased potency. However, we observed that ceritinib did not overcome two crizotinib-resistant ALK mutations, G1202R and F1174C, and one of these mutations was identified in 5 of 11 biopsies from patients with acquired resistance to ceritinib. Altogether, our results demonstrate that ceritinib can overcome crizotinib resistance, consistent with clinical data showing marked efficacy of ceritinib in patients with crizotinib-resistant disease.

SIGNIFICANCE

The second-generation ALK inhibitor ceritinib can overcome several crizotinib-resistant mutations and is potent against several in vitro and in vivo laboratory models of acquired resistance to crizotinib. These findings provide the molecular basis for the marked clinical activity of ceritinib in patients with ALK-positive NSCLC with crizotinib-resistant disease. Cancer Discov; 4(6); 662-73. ©2014 AACR. See related commentary by Ramalingam and Khuri, p. 634 This article is highlighted in the In This Issue feature, p. 621.

NMR Structural Studies of Interactions of a Small, Nonpeptidyl Tpo Mimic with the Thrombopoietin Receptor Extracellular Juxtamembrane and Transmembrane Domains

Thrombopoietin (Tpo) is a glycoprotein growth factor that supports hematopoietic stem cell survival and expansion and is the principal regulator of megakaryocyte growth and differentiation. Several small, nonpeptidyl molecules have been identified as selective human Tpo receptor (hTpoR) agonists. To understand how the small molecule Tpo mimic SB394725 interacts and activates hTpoR, we performed receptor domain swap and mutagenesis studies. The results suggest that SB394725 interacts specifically with the extracellular juxtamembrane region (JMR) and the transmembrane (TM) domain of hTpoR. Solution and solid-state NMR structural studies using a peptide containing the JMR-TM sequences showed that this region of hTpoR, unexpectedly, consists of two alpha-helices separated by a few nonhelical residues. SB394725 interacts specifically with His-499 in the TM domain and a few distinct residues in the JMR-TM region and affects several specific C-terminal TM domain residues. The unique structural information provided by these studies both sheds light on the distinctive mechanism of action of SB394725 and provides valuable insight into the mechanism of ligand-induced cytokine receptor activation.

Conjugate hydrocyanation of 17-acetyl-11-carbomethoxygona-1,3,5(10),13(17)-tetraenes

The conjugate hydrocyanation of 17-acetylgona-11-carbomethoxy-1,3,5(10),13(17)-tetraenes using diethylaluminum cyanide (Nagata reaction) is reported. This methodology has allowed the introduction of an angular cyano group at the C-13 position of the steroid skeleton. Subsequent reduction of the nitrile group yielded various functionalized steroids. One of them, 22 bears the natural trans/anti/trans stereochemistry and possesses an hydroxyl and aminomethyl functionalities in the positions 11beta and 13beta, respectively. The characteristic (1)H and (13)C NMR spectroscopic features of the synthesized steroids are reported.

Biological characterization of a heterodimer-selective retinoid X receptor modulator: potential benefits for the treatment of type 2 diabetes

Specific retinoid X receptor (RXR) agonists, such as LG100268 (LG268), and the thiazolidinedione (TZD) PPARgamma agonists, such as rosiglitazone, produce insulin sensitization in rodent models of insulin resistance and type 2 diabetes. In sharp contrast to the TZDs that produce significant increases in body weight gain, RXR agonists reduce body weight gain and food consumption. Unfortunately, RXR agonists also suppress the thyroid hormone axis and generally produce hypertriglyceridemia. Heterodimer-selective RXR modulators have been identified that, in rodents, retain the metabolic benefits of RXR agonists with reduced side effects. These modulators bind specifically to RXR with high affinity and are RXR homodimer partial agonists. Although RXR agonists activate many heterodimer partners, these modulators selectively activate RXR:PPARalpha and RXR:PPARgamma, but not RXR:RARalpha, RXR:LXRalpha, RXR:LXRbeta, or RXR:FXRalpha. We report the in vivo characterization of one RXR modulator, LG101506 (LG1506). In Zucker fatty (fa/fa) rats, LG1506 is a potent insulin sensitizer that also enhances the insulin-sensitizing activities of rosiglitazone. Administration of LG1506 reduces both body weight gain and food consumption and blocks the TZD-induced weight gain when coadministered with rosiglitazone. LG1506 does not significantly suppress the thyroid hormone axis in rats, nor does it elevate triglycerides in Sprague Dawley rats. However, LG1506 produces a unique pattern of triglycerides elevation in Zucker rats. LG1506 elevates high-density lipoprotein cholesterol in humanized apolipoprotein A-1-transgenic mice. Therefore, selective RXR modulators are a promising approach for developing improved therapies for type 2 diabetes, although additional studies are needed to understand the strain-specific effects on triglycerides.

Design and synthesis of benzofused heterocyclic RXR modulators

Benzofused heterocyclic analogs of the RXR selective modulator 1 (LG101506) were synthesized, and tested for their ability to bind RXRalpha and activate RXR homo and heterodimers. Potency and efficacy were observed to be dependent upon the choice of heterocycle as well as the sidechain employed.

Design, synthesis and structure–activity relationship of novel RXR-selective modulators

The synthesis and in vitro characterization of novel RXR-selective ligands possessing various substituted 1-benzofuran or 1-benzothiophene moieties are described.

Design and synthesis of novel RXR-selective modulators with improved pharmacological profile

New RXR-selective modulators possessing a 6-fluoro trienoic acid moiety (6Z olefin) or a fluorinated/heterocyclic-substituted benzene core ring, were synthesized in an expedient and selective way. A subset of these compounds was evaluated for their metabolic properties (exposure in IRC male mice) and show a dramatic increase of exposure compared to our reference compound, 3 (LG101506).

Design and synthesis of fluorinated RXR modulators

Fluorinated trienoic acid analogues of the RXR selective modulator 1 (LG101506) were synthesized, and tested for their ability to bind RXRalpha and activate RXR homo and heterodimers. Potency and efficacy were observed to be dependent upon the position of fluorination, and improvement in pharmacological profile was demonstrated in some cases.

Design, synthesis, and structure-activity relationship studies of novel 6,7-locked-[7-(2-alkoxy-3,5-dialkylbenzene)-3-methylocta]-2,4,6-trienoic acids

Retinoid X receptor:peroxisome proliferative-activated receptor (RXR:PPAR) heterodimers play a critical role in the regulation of glucose (RXR/PPARgamma) and lipid metabolism (RXR/PPARalpha). Previously, we described a concise structure-activity relationship study of selective RXR modulators possessing a (2E,4E,6Z)-3-methyl-7-(3,5-dialkyl-6-alkoxyphenyl)-octa-2,4,6-trienoic acid scaffold. These studies were focused on the 2-position alkoxy side chain. We describe here the design and synthesis of a novel series of RXR selective modulators possessing the same aromatic core structure with the addition of a ring locked 6-7-Z-olefin on the trienoic acid moiety. The synthesis and structure-activity relationship studies of these 6,7-locked cyclopentenyl, phenyl, thienyl, furan, and pyridine-trienoic acid derivatives is presented herein.

Novel (2E,4E,6Z)-7-(2-alkoxy-3,5-dialkylbenzene)-3-methylocta-2,4,6-trienoic acid retinoid X receptor modulators are active in models of type 2 diabetes

Previous data have shown that RXR-selective agonists (e.g., 3 and 4) are insulin sensitizers in rodent models of non-insulin-dependent diabetes mellitus (NIDDM). Unfortunately, they also produce dramatic increases in triglycerides and profound suppression of the thyroid hormone axis. Here we describe the design and synthesis of new RXR modulators that retain the insulin-sensitizing activity of RXR agonists but produce substantially reduced side effects. These molecules bind selectively and with high affinity to RXR and, unlike RXR agonists, do not activate RXR homodimers. To further evaluate the antidiabetic activity of these RXR modulators, we have designed a concise and systematic structure-activity relationship around the 2E,4E,6Z-7-aryl-3-methylocta-2,4,6-trienoic acid scaffold. Selected compounds have been evaluated using insulin-resistant rodents (db/db mice) to characterize effects on glucose homeostasis. Our studies demonstrate the effectiveness of RXR modulators in lowering plasma glucose in the db/db mouse model.

A very short synthesis of steroids from 1,3-butadiene and benzocyclobutenes

Lewis acid mediated addition of 1,8-bis(trimethylsilyl)octa-2,6-diene (BISTRO) 1 to succinic anhydride led to spirolactone 2 [(+/-)-6,9-divinyl-1-oxaspiro[4.4]nonan-2-one]. Methoxycarbonylation followed by stereoselective alkylation by various benzocyclobutenes afforded the substituted benzocyclobutene steroid precursors 5. Thermolysis of 5 gave rise to steroids (+/-)-6 with a trans-anti-cis configuration in five steps and in a highly stereoselective manner. Modifications of the sequence allowed the preparation of steroids (+/-)-11 with trans-anti-trans configuration.