HM71224, a novel Bruton's tyrosine kinase inhibitor, suppresses B cell and monocyte activation and ameliorates arthritis in a mouse model: a potential drug for rheumatoid arthritis

Novel Bruton's tyrosine kinase inhibitor TAS5315 suppresses the progression of inflammation and joint destruction in rodent collagen-induced arthritis

Rheumatoid arthritis is an inflammatory autoimmune disease, characterized by autoantibody production, synovial inflammation, and joint destruction. Its pathogenesis is due to environmental factors and genetic backgrounds. Bruton's tyrosine kinase is a cytoplasmic non-receptor tyrosine kinase, expressed in most hematopoietic cell lineages, except T cells and plasma cells, and regulates various immune-related signaling pathways, thereby playing a crucial role in pathogenesis. Thus, inhibiting Bruton's tyrosine kinase may prove beneficial in treating autoimmune diseases. In the present study, we characterized Bruton's tyrosine kinase inhibitor, TAS5315, in vitro and evaluated its therapeutic effects in experimental arthritis models. TAS5315 markedly inhibited Bruton's tyrosine kinase enzyme activity and suppressed the B-cell receptor signaling pathway in Ramos cells. Moreover, it suppressed the expression of CD69, CD86, and MHC class II in mouse B lymphocytes and the production of TNF-α and MIP-1α in mouse macrophages and decreased bone resorption activity in mouse osteoclasts. Furthermore, it ameliorated the pathological changes in two rodent models of collagen-induced arthritis in vivo. TAS5315 improved bone mineral density and bone intensity. Thus, these results suggest that TAS5315 could be a promising therapeutic option for the treatment of rheumatoid arthritis.

Bruton's Kinase Inhibitors for the Treatment of Immunological Diseases: Current Status and Perspectives

The use of Bruton’s tyrosine kinase (BTK) inhibitors has changed the management of patients with B-cell lymphoid malignancies. BTK is an important molecule that interconnects B-cell antigen receptor (BCR) signaling. BTK inhibitors (BTKis) are classified into three categories, namely covalent irreversible inhibitors, covalent reversible inhibitors, and non-covalent reversible inhibitors. Ibrutinib is the first covalent, irreversible BTK inhibitor approved in 2013 as a breakthrough therapy for chronic lymphocytic leukemia patients. Subsequently, two other covalent, irreversible, second-generation BTKis, acalabrutinib and zanubrutinib, have been developed for lymphoid malignancies to reduce the ibrutinib-mediated adverse effects. More recently, irreversible and reversible BTKis have been under development for immune-mediated diseases, including autoimmune hemolytic anemia, immune thrombocytopenia, multiple sclerosis, pemphigus vulgaris, atopic dermatitis, rheumatoid arthritis, systemic lupus erythematosus, Sjögren’s disease, and chronic spontaneous urticaria, among others. This review article summarizes the preclinical and clinical evidence supporting the role of BTKis in various autoimmune, allergic, and inflammatory conditions.

Discovery and Preclinical Characterization of BIIB091, a Reversible, Selective BTK Inhibitor for the Treatment of Multiple Sclerosis

Multiple Sclerosis is a chronic autoimmune neurodegenerative disorder of the central nervous system (CNS) that is characterized by inflammation, demyelination, and axonal injury leading to permeant disability. In the early stage of MS, inflammation is the primary driver of the disease progression. There remains an unmet need to develop high efficacy therapies with superior safety profiles to prevent the inflammation processes leading to disability. Herein, we describe the discovery of BIIB091, a structurally distinct orthosteric ATP competitive, reversible inhibitor that binds the BTK protein in a DFG-in confirmation designed to sequester Tyr-551, an important phosphorylation site on BTK, into an inactive conformation with excellent affinity. Preclinical studies demonstrated BIB091 to be a high potency molecule with good drug-like properties and a safety/tolerability profile suitable for clinical development as a highly selective, reversible BTKi for treating autoimmune diseases such as MS.

Bruton's Tyrosine Kinase (BTK) Inhibitors and Autoimmune Diseases: Making Sense of BTK Inhibitor Specificity Profiles and Recent Clinical Trial Successes and Failures

Clinical development of BTK kinase inhibitors for treating autoimmune diseases has lagged behind development of these drugs for treating cancers, due in part from concerns over the lack of selectivity and associated toxicity profiles of first generation drug candidates when used in the long term treatment of immune mediated diseases. Second generation BTK inhibitors have made great strides in limiting off-target activities for distantly related kinases, though they have had variable success at limiting cross-reactivity within the more closely related TEC family of kinases. We investigated the BTK specificity and toxicity profiles, drug properties, disease associated signaling pathways, clinical indications, and trial successes and failures for the 13 BTK inhibitor drug candidates tested in phase 2 or higher clinical trials representing 7 autoimmune and 2 inflammatory immune-mediated diseases. We focused on rheumatoid arthritis (RA), multiple sclerosis (MS), and systemic lupus erythematosus (SLE) where the majority of BTK nonclinical and clinical studies have been reported, with additional information for pemphigus vulgaris (PV), Sjogren’s disease (SJ), chronic spontaneous urticaria (CSU), graft versus host disease (GVHD), and asthma included where available. While improved BTK selectivity versus kinases outside the TEC family improved clinical toxicity profiles, less profile distinction was evident within the TEC family. Analysis of genetic associations of RA, MS, and SLE biomarkers with TEC family members revealed that BTK and TEC family members may not be drivers of disease. They are, however, mediators of signaling pathways associated with the pathophysiology of autoimmune diseases. BTK in particular may be associated with B cell and myeloid differentiation as well as autoantibody development implicated in immune mediated diseases. Successes in the clinic for treating RA, MS, PV, ITP, and GVHD, but not for SLE and SJ support the concept that BTK plays an important role in mediating pathogenic processes amenable to therapeutic intervention, depending on the disease. Based on the data collected in this study, we propose that current compound characteristics of BTK inhibitor drug candidates for the treatment of autoimmune diseases have achieved the selectivity, safety, and coverage requirements necessary to deliver therapeutic benefit.

Target modulation and pharmacokinetics/pharmacodynamics translation of the BTK inhibitor poseltinib for model-informed phase II dose selection

The selective Bruton tyrosine kinase (BTK) inhibitor poseltinib has been shown to inhibit the BCR signal transduction pathway and cytokine production in B cells (Park et al.Arthritis Res. Ther.18, 91, 10.1186/s13075-016-0988-z, 2016). This study describes the translation of nonclinical research studies to a phase I clinical trial in healthy volunteers in which pharmacokinetics (PKs) and pharmacodynamics (PDs) were evaluated for dose determination. The BTK protein kinase inhibitory effects of poseltinib in human peripheral blood mononuclear cells (PBMCs) and in rats with collagen-induced arthritis (CIA) were evaluated. High-dimensional phosphorylation analysis was conducted on human immune cells such as B cells, CD8 + memory cells, CD4 + memory cells, NK cells, neutrophils, and monocytes, to map the impact of poseltinib on BTK/PLC and AKT signaling pathways. PK and PD profiles were evaluated in a first-in-human study in healthy donors, and a PK/PD model was established based on BTK occupancy. Poseltinib bound to the BTK protein and modulated BTK phosphorylation in human PBMCs. High-dimensional phosphorylation analysis of 94 nodes showed that poseltinib had the highest impact on anti-IgM + CD40L stimulated B cells, however, lower impacts on anti-CD3/CD-28 stimulated T cells, IL-2 stimulated CD4 + T cells and NK cells, M-CSF stimulated monocytes, or LPS-induced granulocytes. In anti-IgM + CD40L stimulated B cells, poseltinib inhibited the phosphorylation of BTK, AKT, and PLCγ2. Moreover, poseltinib dose dependently improved arthritis disease severity in CIA rat model. In a clinical phase I trial for healthy volunteers, poseltinib exhibited dose-dependent and persistent BTK occupancy in PBMCs of all poseltinib-administrated patients in the study. More than 80% of BTK occupancy at 40 mg dosing was maintained for up to 48 h after the first dose. A first-in-human healthy volunteer study of poseltinib established target engagement with circulating BTK protein. Desirable PK and PD properties were observed, and a modeling approach was used for rational dose selection for subsequent trials. Poseltinib was confirmed as a potential BTK inhibitor for the treatment of autoimmune diseases.

Trial registration: This article includes the results of a clinical intervention on human participants [NCT01765478].

Bruton's Tyrosine Kinase Inhibition for the Treatment of Rheumatoid Arthritis

Bruton’s tyrosine kinase (BTK) inhibitors are an emerging class of drugs that inhibit B cell receptor activation, FC-γ receptor signaling, and osteoclast proliferation. Following on approval for treatment of hematologic malignancies, BTK inhibitors are now under investigation to treat a number of different autoimmune diseases, including rheumatoid arthritis (RA). While the results of BTK inhibitors in RA animal models have been promising, the ensuing human clinical trial outcomes have been rather equivocal. This review will outline the mechanisms of BTK inhibition and its potential impact on immune mediated disease, the types of BTK inhibitors being studied for RA, the findings from both preclinical and clinical trials of BTK inhibitors in RA, and directions for future research.

Bruton's Tyrosine Kinase Inhibition as an Emerging Therapy in Systemic Autoimmune Disease

Systemic autoimmune disorders are complex heterogeneous chronic diseases involving many different immune cells. A significant proportion of patients respond poorly to therapy. In addition, the high burden of adverse effects caused by "classical" anti-rheumatic or immune modulatory drugs provides a need to develop more specific therapies that are better tolerated. Bruton's tyrosine kinase (BTK) is a crucial signaling protein that directly links B-cell receptor (BCR) signals to B-cell activation, proliferation, and survival. BTK is not only expressed in B cells but also in myeloid cells, and is involved in many different signaling pathways that drive autoimmunity. This makes BTK an interesting therapeutic target in the treatment of autoimmune diseases. The past decade has seen the emergence of first-line BTK small-molecule inhibitors with great efficacy in the treatment of B-cell malignancies, but with unfavorable safety profiles for use in autoimmunity due to off-target effects. The development of second-generation BTK inhibitors with superior BTK specificity has facilitated the investigation of their efficacy in clinical trials with autoimmune patients. In this review, we discuss the role of BTK in key signaling pathways involved in autoimmunity and provide an overview of the different inhibitors that are currently being investigated in clinical trials of systemic autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, as well as available results from completed trials.

Recent Advances in BTK Inhibitors for the Treatment of Inflammatory and Autoimmune Diseases

Bruton’s tyrosine kinase (BTK) plays a crucial role in B-cell receptor and Fc receptor signaling pathways. BTK is also involved in the regulation of Toll-like receptors and chemokine receptors. Given the central role of BTK in immunity, BTK inhibition represents a promising therapeutic approach for the treatment of inflammatory and autoimmune diseases. Great efforts have been made in developing BTK inhibitors for potential clinical applications in inflammatory and autoimmune diseases. This review covers the recent development of BTK inhibitors at preclinical and clinical stages in treating these diseases. Individual examples of three types of inhibitors, namely covalent irreversible inhibitors, covalent reversible inhibitors, and non-covalent reversible inhibitors, are discussed with a focus on their structure, bioactivity and selectivity. Contrary to expectations, reversible BTK inhibitors have not yielded a significant breakthrough so far. The development of covalent, irreversible BTK inhibitors has progressed more rapidly. Many candidates entered different stages of clinical trials; tolebrutinib and evobrutinib are undergoing phase 3 clinical evaluation. Rilzabrutinib, a covalent reversible BTK inhibitor, is now in phase 3 clinical trials and also offers a promising future. An analysis of the protein–inhibitor interactions based on published co-crystal structures provides useful clues for the rational design of safe and effective small-molecule BTK inhibitors.

Small molecules in targeted cancer therapy: advances, challenges, and future perspectives

Due to the advantages in efficacy and safety compared with traditional chemotherapy drugs, targeted therapeutic drugs have become mainstream cancer treatments. Since the first tyrosine kinase inhibitor imatinib was approved to enter the market by the US Food and Drug Administration (FDA) in 2001, an increasing number of small-molecule targeted drugs have been developed for the treatment of malignancies. By December 2020, 89 small-molecule targeted antitumor drugs have been approved by the US FDA and the National Medical Products Administration (NMPA) of China. Despite great progress, small-molecule targeted anti-cancer drugs still face many challenges, such as a low response rate and drug resistance. To better promote the development of targeted anti-cancer drugs, we conducted a comprehensive review of small-molecule targeted anti-cancer drugs according to the target classification. We present all the approved drugs as well as important drug candidates in clinical trials for each target, discuss the current challenges, and provide insights and perspectives for the research and development of anti-cancer drugs.

Discovery of potent and selective reversible Bruton's tyrosine kinase inhibitors

Bruton's tyrosine kinase (BTK) is a cytoplasmic, non-receptor tyrosine kinase member of the TEC family of tyrosine kinases. Pre-clinical and clinical data have shown that targeting BTK can be used for the treatment for B-cell disorders. Here we disclose the discovery of a novel imidazo[4,5-b]pyridine series of potent, selective reversible BTK inhibitors through a rational design approach. From a starting hit molecule 1, medicinal chemistry optimization led to the development of a lead compound 30, which exhibited 58 nM BTK inhibitory potency in human whole blood and high kinome selectivity. Additionally, the compound demonstrated favorable pharmacokinetics (PK), and showed potent dose-dependent efficacy in a rat CIA model.

The Results of Well-conducted Negative Clinical Trials Should Be Reported in a Peer-reviewed Journal

We expect that the pathogenesis, manifestations, and successful management of disease will be fully reported in peer-reviewed journals. However, there are multiple publications addressing the likelihood that clinical trials that do not report a positive result are underreported in the medical literature, with a maximum of 50% of negative studies published, even after 5 years of availability of their results1,2.

Small molecule approaches to treat autoimmune and inflammatory diseases (Part I): Kinase inhibitors

Autoimmune and inflammatory diseases place a huge burden on the healthcare system. Small molecule (SM) therapeutics provide much needed complementary treatment options for these diseases. This digest series highlights the latest progress in the discovery and development of safe and efficacious SMs to treat autoimmune and inflammatory diseases with each part representing a class of SMs, namely: 1) protein kinases; 2) nucleic acid-sensing pathways; and 3) soluble ligands and receptors on cell surfaces. In this first part of the series, the focus is on kinase inhibitors that emerged between 2018 and 2020, and which exhibit increased target and tissue selectivity with the aim of increasing their therapeutic index.

Safety and Efficacy of Poseltinib, Bruton's Tyrosine Kinase Inhibitor, in Patients With Rheumatoid Arthritis: A Randomized, Double-blind, Placebo-controlled, 2-part Phase II Study

OBJECTIVE

To evaluate the efficacy and safety of poseltinib (formerly LY3337641/HM71224), an irreversible covalent inhibitor of Bruton's tyrosine kinase in a 2-part, phase II trial (RAjuvenate; ClinicalTrials.gov: NCT02628028) in adults with active rheumatoid arthritis (RA).

METHODS

In Part A, 36 patients with mildly active RA were randomized 1:1:1:1 to oral poseltinib 5, 10, or 30 mg or placebo once daily for 4 weeks to assess safety and tolerability. No safety signals precluded moving to Part B, where 250 patients with moderate-to-severe RA were randomized 1:1:1:1 to oral poseltinib 5 mg (n = 63), 10 mg (n = 62), or 30 mg (n = 63), or placebo (n = 62) once daily for 12 weeks. Parts A and B permitted stable doses of background disease-modifying antirheumatic drugs. The primary endpoint in Part B was proportion of patients achieving 20% improvement in American College of Rheumatology criteria (ACR20) at Week 12. Logistic regression compared each poseltinib dose to placebo for primary and secondary endpoints. Nonresponder imputation was used for missing data.

RESULTS

After interim analysis showed low likelihood of demonstrating significant efficacy, the sponsor discontinued Part B of the study. One hundred and eighty-nine (76%) patients completed 12 weeks in Part B; 61 discontinued study treatment (27 [44%] due to study termination by sponsor). There was no statistically significant difference in ACR20 response between any dose of poseltinib and placebo at Week 12 (P > 0.05 for all comparisons). Five serious adverse events occurred (n = 2, placebo; n = 3, 30 mg); there was 1 death due to a fall.

CONCLUSION

While no safety findings precluded continuation, the study was terminated after interim data demonstrated low likelihood of benefit in RA.

Driving Potency with Rotationally Stable Atropisomers: Discovery of Pyridopyrimidinedione-Carbazole Inhibitors of BTK

Bruton's tyrosine kinase (BTK) has been shown to play a key role in the pathogenesis of autoimmunity. Therefore, the inhibition of the kinase activity of BTK with a small molecule inhibitor could offer a breakthrough in the clinical treatment of many autoimmune diseases. This Letter describes the discovery of BMS-986143 through systematic structure-activity relationship (SAR) development. This compound benefits from defined chirality derived from two rotationally stable atropisomeric axes, providing a potent and selective single atropisomer with desirable efficacy and tolerability profiles.

Synthesis and biological activity of imidazole group-substituted arylaminopyrimidines (IAAPs) as potent BTK inhibitors against B-cell lymphoma and AML

Bruton's tyrosine kinase (BTK) is a member of the Tec kinase family and plays a key role in the modulation of the B-cell receptor (BCR)-mediated signaling pathway. Inhibition of BTK has been proven to be an effective therapeutic approach for various hematological malignancies, such as chronic lymphocytic leukemia (CLL), mantle cell leukemia (MCL), diffuse large B-cell lymphoma (DLBCL) and acute myeloid leukemia (AML). Here, a new series of imidazole group-substituted arylaminopyrimidines (IAAPs) were designed and synthesized as potent inhibitors of the enzymatic activity of BTK with a half maximal inhibitory concentration (IC₅₀) ranging from 13.10 to 42.40 nM. In particular, 11a and 11b exhibited stronger antiproliferative activity against AML and B lymphomas cell lines compared with BTK inhibitor ibrutinib and showed low cytotoxicity against normal peripheral blood mononuclear cells (PBMCs). In addition, analysis of the mechanism of action of these compounds revealed that 11a and 11b induced significant apoptosis in AML and B lymphoma cells by arresting the cell cycle at the G1/G0 or G2/M stage and blocked BTK autophosphorylation as well as the ensuing abrogation of pro-survival AKT and ERK signaling. Taken together, these results suggest that 11a and 11b might serve as valuable preclinical candidates for the treatment of AML and B-cell lymphoma.

Analysis of the Function of the Lymphocytic Choriomeningitis Virus S Segment Untranslated Region on Growth Capacity In Vitro and on Virulence In Vivo

Lymphocytic choriomeningitis virus (LCMV) is a prototypic arenavirus. The function of untranslated regions (UTRs) of the LCMV genome has not been well studied except for the extreme 19 nucleotide residues of both the 5′ and 3′ termini. There are internal UTRs composed of 58 and 41 nucleotide residues in the 5′ and 3′ UTRs, respectively, in the LCMV S segment. Their functional roles have yet to be elucidated. In this study, reverse genetics and minigenome systems were established for LCMV strain WE and the function of these regions were analyzed. It was revealed that nucleotides 20–40 and 20–38 located downstream of the 19 nucleotides in the 5′ and 3′ termini, respectively, were involved in viral genome replication and transcription. Furthermore, it was revealed that the other internal UTRs (nucleotides 41–77 and 39–60 in the 5′ and 3′ termini, respectively) in the S segment were involved in virulence in vivo, even though these regions did not affect viral growth capacity in Vero cells. The introduction of LCMV with mutations in these regions attenuates the virus and may enable the production of LCMV vaccine candidates.

Advances in covalent kinase inhibitors

This comprehensive review details recent advances, challenges and innovations in covalent kinase inhibition within a 10 year period (2007–2018).

Tyrosine kinase inhibitors for the treatment of rheumatoid arthritis: phase I to Ⅱ clinical trials

Introduction: Rheumatoid arthritis (RA) is a chronic, refractory disorder caused by autoimmunity in the synovial joints. Disease-modifying anti-rheumatic drugs (DMARDs) and biologicals offer remission in only two-thirds of RA patients within 3 months, hence new therapeutic approaches are necessary. Tyrosine kinase inhibitors (TKIs) are newly developed small molecule drugs which have demonstrated encouraging results in this disease.Areas covered: The key findings from phase I and II clinical trials that have investigated the use of novel TKIs in the treatment of RA are discussed. We examined the literature published between January 2014 to January 2019 using electronic databases including PubMed, Web of Science, Medline, Embase, and Google Scholar. Additional information about phase I and II trials on the ClinicalTrial.gov website up to January 2019 was also retrieved.Expert opinion: JAK inhibitors are promising drugs with sound efficacy and acceptable safety and may be beneficial to patients who do not respond to DMARDs and biologicals. The response rates among RA patients to TKIs are diverse; genetic and environmental factors may be involved in the varying responses which are closely related to the pathogenesis of RA. Future studies may reveal the underlying mechanisms of resistance and non-response.

Cartilage and Bone Destruction in Arthritis: Pathogenesis and Treatment Strategy: A Literature Review

Arthritis is inflammation of the joints accompanied by osteochondral destruction. It can take many forms, including osteoarthritis, rheumatoid arthritis, and psoriatic arthritis. These diseases share one commonality—osteochondral destruction based on inflammation. The background includes a close interaction between osseous tissues and immune cells through various inflammatory cytokines. However, the tissues and cytokines that play major roles are different in each disease, and as a result, the mechanism of osteochondral destruction also differs. In recent years, there have been many findings regarding not only extracellular signaling pathways but also intracellular signaling pathways. In particular, we anticipate that the intracellular signals of osteoclasts, which play a central role in bone destruction, will become novel therapeutic targets. In this review, we have summarized the pathology of arthritis and the latest findings on the mechanism of osteochondral destruction, as well as present and future therapeutic strategies for these targets.

Pharmacophore modeling and virtual screening in search of novel Bruton's tyrosine kinase inhibitors

Bruton's tyrosine kinase (BTK) is a known drug target for B cell malignancies and autoimmune diseases like rheumatoid arthritis. Consequently, efforts to develop BTK inhibitors have gained momentum in the last decade, resulting in a number of potential inhibitory molecules. However, to date, there are only two FDA approved drugs for B cell malignancies (Ibrutinib and Acalabrutinib), thus continued efforts are warranted. A large number of molecular scaffolds with potential BTK inhibitory activity are already available from these studies, and therefore we employed a ligand-based approach towards computer-aided drug design to develop a pharmacophore model for BTK inhibitors. Using over 400 molecules with known half maximal inhibitory concentrations (IC₅₀) for BTK, a four-point pharmacophore hypothesis was derived, with two aromatic rings (R), one hydrogen bond acceptor (A) and one hydrogen bond donor (D). Screening of two small-molecule databases against this pharmacophore returned 620 hits with matching chemical features. Docking these against the ATP-binding site of the BTK kinase domain through a virtual screening workflow yielded 30 hits from which ultimately two natural compounds (two best scoring poses for each) were prioritized. Molecular dynamics simulations of these four docked complexes confirmed the stability of protein-ligand binding over a 200 ns time period, and thus their suitability for lead molecule development with further optimization and experimental testing. Of note, the pharmacophore model developed in this study would also be further useful for de novo drug design and virtual screening efforts on a larger scale. Graphical abstract Pharmacophore modeling and virtual screening in search of novel Bruton's tyrosine kinase inhibitors.

Efficacy and Pharmacodynamic Modeling of the BTK Inhibitor Evobrutinib in Autoimmune Disease Models

Because of its role in mediating both B cell and Fc receptor signaling, Bruton's tyrosine kinase (BTK) is a promising target for the treatment of autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Evobrutinib is a novel, highly selective, irreversible BTK inhibitor that potently inhibits BCR- and Fc receptor-mediated signaling and, thus, subsequent activation and function of human B cells and innate immune cells such as monocytes and basophils. We evaluated evobrutinib in preclinical models of RA and SLE and characterized the relationship between BTK occupancy and inhibition of disease activity. In mouse models of RA and SLE, orally administered evobrutinib displayed robust efficacy, as demonstrated by reduction of disease severity and histological damage. In the SLE model, evobrutinib inhibited B cell activation, reduced autoantibody production and plasma cell numbers, and normalized B and T cell subsets. In the RA model, efficacy was achieved despite failure to reduce autoantibodies. Pharmacokinetic/pharmacodynamic modeling showed that mean BTK occupancy in blood cells of 80% was linked to near-complete disease inhibition in both RA and SLE mouse models. In addition, evobrutinib inhibited mast cell activation in a passive cutaneous anaphylaxis model. Thus, evobrutinib achieves efficacy by acting both on B cells and innate immune cells. Taken together, our data show that evobrutinib is a promising molecule for the chronic treatment of B cell-driven autoimmune disorders.

Covalent Inhibition in Drug Discovery

Although covalent inhibitors have been used as therapeutics for more than a century, there has been general resistance in the pharmaceutical industry against their further development due to safety concerns. This inclination has recently been reverted after the development of a wide variety of covalent inhibitors to address human health conditions along with the US Food and Drug Administration (FDA) approval of several covalent therapeutics for use in humans. Along with this exciting resurrection of an old drug discovery concept, this review surveys enzymes that can be targeted by covalent inhibitors for the treatment of human diseases. We focus on protein kinases, RAS proteins, and a few other enzymes that have been studied extensively as targets for covalent inhibition, with the aim to address challenges in designing effective covalent drugs and to provide suggestions in the area that have yet to be explored.

Synthesis and biological evaluation of novel 1-substituted 3-(3-phenoxyprop-1-yn-1-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amines as potent Bruton's tyrosine kinase (BTK) inhibitors

A new series of 1-substituted pyrazolopyrimidine derivatives were synthesized as potent BTK inhibitors and they were evaluated by enzyme-based assay and anti-proliferation against multiple B-cell lymphoma cell lines in vitro. Among these compounds, 9h exhibited the highest potency against BTK enzyme, with IC₅₀ value of 4.2 nM. In particular, 8 and 9f performed better inhibition against the proliferation of B lymphoma cell lines DOHH2 and WSU-DLCL2 than the clinical drug ibrutinb. In addition, the test toward the normal PBMC cells showed that 8 possessed low cell cytotoxicity. All these explorations indicated that 8 could serve as a valuable anti-tumor agent for B-cell lymphoblastic leukemia treatment.

Molecular Modeling Studies on Carbazole Carboxamide Based BTK Inhibitors Using Docking and Structure-Based 3D-QSAR

Rheumatoid arthritis (RA) is the second common rheumatic immune disease with chronic, invasive inflammatory characteristics. Non-steroidal anti-inflammatory drugs (NSAIDs), slow-acting anti-rheumatic drugs (SAARDs), or glucocorticoid drugs can improve RA patients’ symptoms, but fail to cure. Broton’s tyrosine kinase (BTK) inhibitors have been proven to be an efficacious target against autoimmune indications and B-cell malignancies. Among the current 11 clinical drugs, only BMS-986142, classified as a carbazole derivative, is used for treating RA. To design novel and highly potent carbazole inhibitors, molecular docking and three dimensional quantitative structure–activity relationship (3D-QSAR) were applied to explore a dataset of 132 new carbazole carboxamide derivatives. The established comparative molecular field analysis (CoMFA) (q² = 0.761, r² = 0.933) and comparative molecular similarity indices analysis (CoMSIA) (q² = 0.891, r² = 0.988) models obtained high predictive and satisfactory values. CoMFA/CoMSIA contour maps demonstrated that bulky substitutions and hydrogen-bond donors were preferred at R₁ and 1-position, respectively, and introducing hydrophilic substitutions at R₁ and R₄ was important for improving BTK inhibitory activities. These results will contribute to the design of novel and highly potent BTK inhibitors.

Possible targets to treat myeloma-related osteoclastogenesis

INTRODUCTION

Bone destruction is the hallmark of multiple myeloma (MM). About 80% of MM patients at diagnosis presents myeloma bone disease (MBD) leading to bone pain and pathological fractures, significantly affecting patients' quality of life. Bisphosphonates are the treatment of choice for MBD, but osteolytic lesions remain a critical issue in the current management of MM patients. Several studies clarified the mechanisms involved in MM-induced osteoclast formation and activation, leading to the identification of new possible targets and the development of better bone-directed therapies, that are discussed in this review. Areas covered: This review summarizes the latest advances in the knowledge of the pathophysiology of the osteoclast formation and activation induced by MM cells, and the new therapeutic targets identified. Recently, neutralizing antibodies (i.e. denosumab, siltuximab, daratumumab), as well as recombinant fusion proteins, and receptor molecular inhibitors, have been developed to block these targets. Clinical trials testing their anti-MBD potential are ongoing. The emerging role of exosomes and microRNAs in the regulation of osteoclast differentiation has been also discussed. Expert commentary: Although further studies are needed to arrive at a clinical approving, the basis for the development of better bone-directed therapies has been established.

Identification of highly potent BTK and JAK3 dual inhibitors with improved activity for the treatment of B-cell lymphoma

The BTK and JAK3 receptor tyrosine kinases are two validated and therapeutically amenable targets in the treatment of B-cell lymphomas. Here we report the identification of several classes of pyrimidine derivatives as potent BTK and JAK3 dual inhibitors. Among these molecules, approximately two thirds displayed strong inhibitory capacity at less than 10 nM concentration, and four compounds (7e, 7g, 7m and 7n) could significantly inhibit the phosphorylation of BTK and JAK3 enzymes at concentrations lower than 1 nM. Additionally, these pyrimidine derivatives also exhibited enhanced activity to block the proliferation of B-cell lymphoma cells compared with the representative BTK inhibitor ibrutinib. In particular, two structure-specific compounds 7b and 7e displayed stronger activity than reference agents in cell-based evaluation, with IC₅₀ values lower than 10 μM. Further biological studies, including flow cytometric analysis, and a xenograft model for in vivo evaluation, also indicated their efficacy and low toxicity in the treatment of B-cell lymphoma. These findings provide a new insight for the development of novel anti-B-cell lymphoma drugs with multi-target actions.

Intracellular B Lymphocyte Signalling and the Regulation of Humoral Immunity and Autoimmunity

B lymphocytes are critical for effective immunity; they produce antibodies and cytokines, present antigens to T lymphocytes and regulate immune responses. However, because of the inherent randomness in the process of generating their vast repertoire of antigen-specific receptors, B cells can also cause diseases through recognizing and reacting to self. Therefore, B lymphocyte selection and responses require tight regulation at multiple levels and at all stages of their development and activation to avoid diseases. Indeed, newly generated B lymphocytes undergo rigorous tolerance mechanisms in the bone marrow and, subsequently, in the periphery after their migration. Furthermore, activation of mature B cells is regulated through controlled expression of co-stimulatory receptors and intracellular signalling thresholds. All these regulatory events determine whether and how B lymphocytes respond to antigens, by undergoing apoptosis or proliferation. However, defects that alter regulated co-stimulatory receptor expression or intracellular signalling thresholds can lead to diseases. For example, autoimmune diseases can result from altered regulation of B cell responses leading to the emergence of high-affinity autoreactive B cells, autoantibody production and tissue damage. The exact cause(s) of defective B cell responses in autoimmune diseases remains unknown. However, there is evidence that defects or mutations in genes that encode individual intracellular signalling proteins lead to autoimmune diseases, thus confirming that defects in intracellular pathways mediate autoimmune diseases. This review provides a synopsis of current knowledge of signalling proteins and pathways that regulate B lymphocyte responses and how defects in these could promote autoimmune diseases. Most of the evidence comes from studies of mouse models of disease and from genetically engineered mice. Some, however, also come from studying B lymphocytes from patients and from genome-wide association studies. Defining proteins and signalling pathways that underpin atypical B cell response in diseases will help in understanding disease mechanisms and provide new therapeutic avenues for precision therapy.

HM71224, a selective Bruton's tyrosine kinase inhibitor, attenuates the development of murine lupus

Background

Systemic lupus erythematosus (SLE) is associated with B cell hyperactivity, and lupus nephritis (LN), in particular, is promoted by the production of autoantibodies and immune complex deposition. Bruton’s tyrosine kinase (BTK) plays critical roles in B cell receptor-related and Fc receptor-related signaling. We aimed to investigate the impact of therapeutic intervention with HM71224 (LY3337641), a selective BTK inhibitor, on the development of murine SLE-like disease features.

Methods

We examined the therapeutic effects of HM71224 on SLE-like disease features in MRL/lpr and NZB/W F1 mice. The disease-related skin lesion was macroscopically observed in MRL/lpr mice, and the impact on splenomegaly and lymphadenopathy was determined by the weight of the spleen and cervical lymph node. The renal function was evaluated by measuring blood urea nitrogen, serum creatinine, and urine protein, and the renal damage was assessed by histopathological grading. Survival rate was observed during the administration period. The impact of B cell inhibition was investigated in splenocytes from both mice using flow cytometry. Autoantibody was measured in serum by ELISA.

Results

HM71224 effectively suppressed splenic B220⁺GL7⁺, B220⁺CD138⁺, and B220⁺CD69⁺ B cell counts, and anti-dsDNA IgG and reduced splenomegaly and lymph node enlargement. The compound also prevented skin lesions caused by lupus development, ameliorated renal inflammation and damage with increased blood urea nitrogen and creatinine, and decreased proteinuria. Furthermore, HM71224 also decreased mortality from lupus development in both mouse models.

Conclusion

Our results indicate that inhibition of BTK by HM71224 effectively reduced B cell hyperactivity and significantly attenuated the development of SLE and LN in rodent SLE models.

Acalabrutinib (ACP-196): A Covalent Bruton Tyrosine Kinase Inhibitor with a Differentiated Selectivity and In Vivo Potency Profile

Several small-molecule Bruton tyrosine kinase (BTK) inhibitors are in development for B cell malignancies and autoimmune disorders, each characterized by distinct potency and selectivity patterns. Herein we describe the pharmacologic characterization of BTK inhibitor acalabrutinib [compound 1, ACP-196 (4-[8-amino-3-[(2S)-1-but-2-ynoylpyrrolidin-2-yl]imidazo[1,5-a]pyrazin-1-yl]-N-(2-pyridyl)benzamide)]. Acalabrutinib possesses a reactive butynamide group that binds covalently to Cys481 in BTK. Relative to the other BTK inhibitors described here, the reduced intrinsic reactivity of acalabrutinib helps to limit inhibition of off-target kinases having cysteine-mediated covalent binding potential. Acalabrutinib demonstrated higher biochemical and cellular selectivity than ibrutinib and spebrutinib (compounds 2 and 3, respectively). Importantly, off-target kinases, such as epidermal growth factor receptor (EGFR) and interleukin 2-inducible T cell kinase (ITK), were not inhibited. Determination of the inhibitory potential of anti-immunoglobulin M-induced CD69 expression in human peripheral blood mononuclear cells and whole blood demonstrated that acalabrutinib is a potent functional BTK inhibitor. In vivo evaluation in mice revealed that acalabrutinib is more potent than ibrutinib and spebrutinib. Preclinical and clinical studies showed that the level and duration of BTK occupancy correlates with in vivo efficacy. Evaluation of the pharmacokinetic properties of acalabrutinib in healthy adult volunteers demonstrated rapid absorption and fast elimination. In these healthy individuals, a single oral dose of 100 mg showed approximately 99% median target coverage at 3 and 12 hours and around 90% at 24 hours in peripheral B cells. In conclusion, acalabrutinib is a BTK inhibitor with key pharmacologic differentiators versus ibrutinib and spebrutinib and is currently being evaluated in clinical trials.

Design and synthesis of sulfonamide-substituted diphenylpyrimidines (SFA-DPPYs) as potent Bruton's tyrosine kinase (BTK) inhibitors with improved activity toward B-cell lymphoblastic leukemia

A new series of diphenylpyrimidine derivatives (SFA-DPPYs) were synthesized by introducing a functional sulfonamide into the C-2 aniline moiety of pyrimidine template, and then were biologically evaluated as potent Bruton's tyrosine kinase (BTK) inhibitors. Among these molecules, inhibitors 10c, 10i, 10j and 10k displayed high potency against the BTK enzyme, with IC₅₀ values of 1.18 nM, 0.92 nM, 0.42 nM and 1.05 nM, respectively. In particular, compound 10c could remarkably inhibit the proliferation of the B lymphoma cell lines at concentrations of 6.49 μM (Ramos cells) and 13.2 μM (Raji cells), and was stronger than the novel agent spebrutinib. In addition, the inhibitory potency toward the normal PBMC cells showed that inhibitor 10c possesses low cell cytotoxicity. All these explorations indicated that molecule 10c could serve as a valuable inhibitor for B-cell lymphoblastic leukemia treatment.

Irreversible inhibition of BTK kinase by a novel highly selective inhibitor CHMFL-BTK-11 suppresses inflammatory response in rheumatoid arthritis model

BTK plays a critical role in the B cell receptor mediated inflammatory signaling in the rheumatoid arthritis (RA). Through a rational design approach we discovered a highly selective and potent BTK kinase inhibitor (CHMFL-BTK-11) which exerted its inhibitory efficacy through a covalent bond with BTK Cys481. CHMFL-BTK-11 potently blocked the anti-IgM stimulated BCR signaling in the Ramos cell lines and isolated human primary B cells. It significantly inhibited the LPS stimulated TNF-α production in the human PBMC cells but only weakly affecting the normal PBMC cell proliferation. In the adjuvant-induced arthritis rat model, CHMFL-BTK-11 ameliorated the inflammatory response through blockage of proliferation of activated B cells, inhibition of the secretion of the inflammatory factors such as IgG1, IgG2, IgM, IL-6 and PMΦ phagocytosis, stimulation of secretion of IL-10. The high specificity of CHMFL-BTK-11 makes it a useful pharmacological tool to further detect BTK mediated signaling in the pathology of RA.

Discovery of Novel Bruton's Tyrosine Kinase (BTK) Inhibitors Bearing a N,9-Diphenyl-9H-purin-2-amine Scaffold

Based on the pyrimidine skeleton of EGFR^T790M inhibitors, a series of N,9-diphenyl-9H-purin-2-amine derivatives were identified as effective BTK inhibitors. Among these compounds, inhibitors 10d, 10i, and 10j, possessing IC₅₀ values of 0.5, 0.5, and 0.4 nM, displayed anti-BTK kinase activity that was as potent as the reference compounds. In particular, compound 10j suppressed the proliferation of two typical B-cell leukemia cell lines expressing high levels of BTK with concentrations of 7.75 and 12.6 μM. The activity of the subject compound as determined by the CCK-8 method and apoptosis analysis validated that inhibitor 10j is slightly more potent than AVL-292 and ibrutinib. The results of these experimental explorations suggested that 10j could serve as a valuable molecule for control of leukemia pending further developments.

Design and synthesis of phosphoryl-substituted diphenylpyrimidines (Pho-DPPYs) as potent Bruton's tyrosine kinase (BTK) inhibitors: Targeted treatment of B lymphoblastic leukemia cell lines

A family of phosphoryl-substituted diphenylpyrimidine derivatives (Pho-DPPYs) were synthesized and biologically evaluated as potent BTK inhibitors in this study. Compound 7b was found to markedly inhibit BTK activity at concentrations of 0.82nmol/L, as well as to suppress the proliferations of B-cell leukemia cell lines (Ramos and Raji) expressing high levels of BTK at concentrations of 3.17μM and 6.69μM. Moreover, flow cytometry analysis results further indicated that 7b promoted cell apoptosis to a substantial degree. In a word, compound 7b is a promising BTK inhibitor for the treatment of B-cell lymphoblastic leukemia.

Discovery of 6-Fluoro-5-(R)-(3-(S)-(8-fluoro-1-methyl-2,4-dioxo-1,2-dihydroquinazolin-3(4H)-yl)-2-methylphenyl)-2-(S)-(2-hydroxypropan-2-yl)-2,3,4,9-tetrahydro-1H-carbazole-8-carboxamide (BMS-986142): A Reversible Inhibitor of Bruton's Tyrosine Kinase (BTK) Conformationally Constrained by Two Locked Atropisomers

Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase, is a member of the Tec family of kinases. BTK plays an essential role in B cell receptor (BCR)-mediated signaling as well as Fcγ receptor signaling in monocytes and Fcε receptor signaling in mast cells and basophils, all of which have been implicated in the pathophysiology of autoimmune disease. As a result, inhibition of BTK is anticipated to provide an effective strategy for the clinical treatment of autoimmune diseases such as lupus and rheumatoid arthritis. This article details the structure-activity relationships (SAR) leading to a novel series of highly potent and selective carbazole and tetrahydrocarbazole based, reversible inhibitors of BTK. Of particular interest is that two atropisomeric centers were rotationally locked to provide a single, stable atropisomer, resulting in enhanced potency and selectivity as well as a reduction in safety liabilities. With significantly enhanced potency and selectivity, excellent in vivo properties and efficacy, and a very desirable tolerability and safety profile, 14f (BMS-986142) was advanced into clinical studies.

Challenges to develop novel anti-inflammatory and analgesic drugs

Chronic inflammatory diseases and persistent pain of different origin represent common medical, social, and economic burden, and their pharmacotherapy is still an unresolved issue. Therefore, there is a great and urgent need to develop anti-inflammatory and analgesic agents with novel mechanisms of action, but it is a very challenging task. The main problem is the relatively large translational gap between the preclinical experimental data and the clinical results due to characteristics of the models, difficulties with the investigational techniques particularly for pain, as well as species differences in the mechanisms. We summarize here the current state-of-the-art medication and related ongoing strategies, and the novel targets with lead molecules under clinical development. The first members of the gold-standard categories, such as nonsteroidal anti-inflammatory drugs, glucocorticoids, and opioids, were introduced decades ago, and since then very few drugs with novel mechanisms of action have been successfully taken to the clinics despite considerable development efforts. Several biologics targeting different key molecules have provided breakthrough in some autoimmune/inflammatory diseases, but they are expensive, only parenterally available, their long-term side effects often limit their administration, and they do not effectively reduce pain. Some kinase inhibitors and phosphodiesterase-4 blockers have recently been introduced as new directions. There are in fact some promising novel approaches at different clinical stages of drug development focusing on transient receptor potential vanilloid 1/ankyrin 1 channel antagonism, inhibition of voltage-gated sodium/calcium channels, several enzymes (kinases, semicarbazide-sensitive amine oxidases, and matrix metalloproteinases), cytokines/chemokines, transcription factors, nerve growth factor, and modulation of several G protein-coupled receptors (cannabinoids, purinoceptors, and neuropeptides). WIREs Nanomed Nanobiotechnol 2017, 9:e1427. doi: 10.1002/wnan.1427 For further resources related to this article, please visit the WIREs website.

Identification of compound-protein interactions through the analysis of gene ontology, KEGG enrichment for proteins and molecular fragments of compounds

Compound-protein interactions play important roles in every cell via the recognition and regulation of specific functional proteins. The correct identification of compound-protein interactions can lead to a good comprehension of this complicated system and provide useful input for the investigation of various attributes of compounds and proteins. In this study, we attempted to understand this system by extracting properties from both proteins and compounds, in which proteins were represented by gene ontology and KEGG pathway enrichment scores and compounds were represented by molecular fragments. Advanced feature selection methods, including minimum redundancy maximum relevance, incremental feature selection, and the basic machine learning algorithm random forest, were used to analyze these properties and extract core factors for the determination of actual compound-protein interactions. Compound-protein interactions reported in The Binding Databases were used as positive samples. To improve the reliability of the results, the analytic procedure was executed five times using different negative samples. Simultaneously, five optimal prediction methods based on a random forest and yielding maximum MCCs of approximately 77.55 % were constructed and may be useful tools for the prediction of compound-protein interactions. This work provides new clues to understanding the system of compound-protein interactions by analyzing extracted core features. Our results indicate that compound-protein interactions are related to biological processes involving immune, developmental and hormone-associated pathways.