Bruton tyrosine kinase inhibitor ONO/GS-4059: from bench to bedside

Small molecule protein kinase inhibitors approved by regulatory agencies outside of the United States

Owing to genetic alterations and overexpression, the dysregulation of protein kinases plays a significant role in the pathogenesis of many autoimmune and neoplastic disorders and protein kinase antagonists have become an important drug target. Although the efficacy of imatinib in the treatment of chronic myelogenous leukemia in the United States in 2001 was the main driver of protein kinase inhibitor drug discovery, this was preceded by the approval of fasudil (a ROCK antagonist) in Japan in 1995 for the treatment of cerebral vasospasm. There are 21 small molecule protein kinase inhibitors that are approved in China, Japan, Europe, and South Korea that are not approved in the United Sates and 75 FDA-approved inhibitors in the United States. Of the 21 agents, eleven target receptor protein-tyrosine kinases, eight inhibit nonreceptor protein-tyrosine kinases, and two block protein-serine/threonine kinases. All 21 drugs are orally bioavailable or topically effective. Of the non-FDA approved drugs, sixteen are prescribed for the treatment of neoplastic diseases, three are directed toward inflammatory disorders, one is used for glaucoma, and fasudil is used in the management of vasospasm. The leading targets of kinase inhibitors approved by both international regulatory agencies and by the FDA are members of the EGFR family, the VEGFR family, and the JAK family. One-third of the 21 internationally approved drugs are not compliant with Lipinski's rule of five for orally bioavailable drugs. The rule of five relies on four parameters including molecular weight, number of hydrogen bond donors and acceptors, and the Log of the partition coefficient.

Approved Small-Molecule ATP-Competitive Kinases Drugs Containing Indole/Azaindole/Oxindole Scaffolds: R&D and Binding Patterns Profiling

Kinases are among the most important families of biomolecules and play an essential role in the regulation of cell proliferation, apoptosis, metabolism, and other critical physiological processes. The dysregulation and gene mutation of kinases are linked to the occurrence and development of various human diseases, especially cancer. As a result, a growing number of small-molecule drugs based on kinase targets are being successfully developed and approved for the treatment of many diseases. The indole/azaindole/oxindole moieties are important key pharmacophores of many bioactive compounds and are generally used as excellent scaffolds for drug discovery in medicinal chemistry. To date, 30 ATP-competitive kinase inhibitors bearing the indole/azaindole/oxindole scaffold have been approved for the treatment of diseases. Herein, we summarize their research and development (R&D) process and describe their binding models to the ATP-binding sites of the target kinases. Moreover, we discuss the significant role of the indole/azaindole/oxindole skeletons in the interaction of their parent drug and target kinases, providing new medicinal chemistry inspiration and ideas for the subsequent development and optimization of kinase inhibitors.

Waldenstrom Macroglobulinemia/Lymphoplasmacytic Lymphoma Associated with Nephrotic Syndrome during Hemodialysis, Treated Successfully with Tirabrutinib

A 74-year-old woman was diagnosed with Waldenstrom macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) in X-18. Fludarabine plus rituximab (FR) was started, and she showed remission. In July X-7, the serum creatinine (Cr) level increased to 1.67 mg/dL, and bendamustine plus rituximab (BR) was started. By November X-7, the Cr level had increased to 8.41 mg/dL, so she was started on hemodialysis (HD). In September X-1, she developed nephrotic syndrome. She was started on tirabrutinib at 480 mg. In July X, her nephrotic syndrome had improved, and a complete response (CR) was achieved. This is the first case of the administration of tirabrutinib in a patient undergoing HD.

Semi-Mechanistic PK/PD Modeling and Simulation of Irreversible BTK Inhibition to Support Dose Selection of Tirabrutinib in Subjects with RA

Tirabrutinib is an irreversible, small-molecule Bruton's tyrosine kinase (BTK) inhibitor, which was approved in Japan (VELEXBRU) to treat B-cell malignancies and is in clinical development for inflammatory diseases. As an application of model-informed drug development, a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for irreversible BTK inhibition of tirabrutinib was developed to support dose selection in clinical development, based on clinical PK and BTK occupancy data from two phase I studies with a wide range of PK exposures in healthy volunteers and in subjects with rheumatoid arthritis. The developed model adequately described and predicted the PK and PD data. Overall, the model-based simulation supported a total daily dose of at least 40 mg, either q.d. or b.i.d., with adequate BTK occupancy (> 90%) for further development in inflammatory diseases. Following the PK/PD modeling and simulation, the relationship between model-predicted BTK occupancy and preliminary clinical efficacy data was also explored and a positive trend was identified between the increasing time above adequate BTK occupancy and better efficacy in treatment for RA by linear regression.

Progress in the development of small molecular inhibitors of the Bruton's tyrosine kinase (BTK) as a promising cancer therapy

Bruton tyrosine kinase (BTK) is a key kinase in the B cell antigen receptor signal transduction pathway, which is involved in the regulation of the proliferation, differentiation and apoptosis of B cells. BTK has become a significant target for the treatment of hematological malignancies and autoimmune diseases. Ibrutinib, the first-generation BTK inhibitor, has made a great contribution to the treatment of B cell malignant tumors, but there are still some problems such as resistance or miss target of site mutation. Therefore, there is an imperative need to develop novel BTK inhibitors to overcome these problems. Besides, proteolysis targeting chimera (PROTAC) technology has been successfully applied to the development of BTK degradation agents, which has opened a fresh way for the BTK targeted treatment. This paper reviews the biological function of BTK, the discovery and development of BTK targeted drugs as a promising cancer therapy. It mainly reviews the binding sites and structural characteristics of BTK, structure-activity relationships, activity and drug resistance of BTK inhibitors, as well as potential treatment strategies to overcome the resistance of BTK, which provides a reference for the rational design and development of new powerful BTK inhibitors.

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.

Bruton's tyrosine kinase inhibition effectively protects against human IgE-mediated anaphylaxis

No known therapies can prevent anaphylaxis. Bruton's tyrosine kinase (BTK) is an enzyme thought to be essential for high-affinity IgE receptor (FcεRI) signaling in human cells. We tested the hypothesis that FDA-approved BTK inhibitors (BTKis) would prevent IgE-mediated responses including anaphylaxis. We showed that irreversible BTKis broadly prevented IgE-mediated degranulation and cytokine production in primary human mast cells and blocked allergen-induced contraction of isolated human bronchi. To address their efficacy in vivo, we created and used what we believe to be a novel humanized mouse model of anaphylaxis that does not require marrow ablation or human tissue implantation. After a single intravenous injection of human CD34+ cells, NSG-SGM3 mice supported the population of mature human tissue-resident mast cells and basophils. These mice showed excellent responses during passive systemic anaphylaxis using human IgE to selectively evoke human mast cell and basophil activation, and response severity was controllable by alteration of the amount of allergen used for challenge. Remarkably, pretreatment with just 2 oral doses of the BTKi acalabrutinib completely prevented moderate IgE-mediated anaphylaxis in these mice and also significantly protected against death during severe anaphylaxis. Our data suggest that BTKis may be able to prevent anaphylaxis in humans by inhibiting FcεRI-mediated signaling.

Aberrantly expressed Bruton's tyrosine kinase preferentially drives metastatic and stem cell-like phenotypes in neuroblastoma cells

PURPOSE

Neuroblastoma, a common childhood tumor, remains one of the most elusive diseases to treat. To date, high-risk neuroblastoma is associated with low survival rates. To address this, novel and more effective therapeutic strategies must continue to be explored.

METHODS

We employed a bioinformatics approach corroborated with in vitro and in vivo data. Samples from neuroblastoma patients were retrieved and immuno-stained for Bruton's tyrosine kinase (BTK). To evaluate its effect on cellular functions, BTK expression in SK-N-BE(2) and SH-SY5Y neuroblastoma cells was downregulated using gene silencing or inhibition with ibrutinib or acalabrutinib. Xenograft mouse models were used to investigate the in vivo role of BTK in neuroblastoma tumorigenesis.

RESULTS

We found that BTK was highly expressed in primary neuroblastoma samples, preferentially in MYCN-amplified neuroblastoma cases, and was associated with a poor prognosis. Immunohistochemical staining of tissues from our neuroblastoma cohort revealed a strong BTK immunoreactivity. We also found that neuroblastoma SK-N-BE(2) and SH-SY5Y cells were sensitive to treatment with ibrutinib and acalabrutinib. Pharmacologic or molecular inhibition of BTK elicited a reduction in the migratory and invasive abilities of neuroblastoma cells, and ibrutinib considerably attenuated the neurosphere-forming ability of neuroblastoma cells. Both inhibitors showed synergism with cisplatin. In vivo assays showed that acalabrutinib effectively inhibited neuroblastoma tumorigenesis.

CONCLUSIONS

From our data we conclude that BTK is a therapeutically targetable driver of neuroblastoma.

Discovery and biological evaluation of N-(3-(7-((2-methoxy-4-(4-methylpiperazin-1-yl)phenyl)amino)-4-methyl-2-oxo-2H-pyrimido[4,5-d][1,3]oxazin-1(4H)-yl)phenyl)acrylamide as potent Bruton's tyrosine kinase inhibitors

Bruton's tyrosine kinase (BTK) is a key component of the B cell receptor (BCR) signaling pathway and plays a crucial role in B cell malignancies and autoimmune disorders; thus, it is an attractive target for the treatment of B cell related diseases. Here, we evaluated the BTK inhibitory activity of a series of pyrimido[4,5-d][1,3]oxazin-2-one derivatives. Combining this evaluation with structure-activity relationship (SAR) analysis, we found that compound 2 exhibited potent BTK kinase inhibitory activity, with an IC₅₀ of 7 nM. This derivative markedly inhibited BTK activation in TMD8 B cell lymphoma cells and thus inhibited the in vitro growth of the cells. Further studies revealed that compound 2 dose dependently arrested TMD8 cells at G₁ phase, accompanied by decreased levels of Rb, phosphorylated Rb, and cyclin D1. Moreover, following treatment with compound 2, TMD8 cells underwent apoptosis associated with PARP and caspase 3 cleavage. Interestingly, the results of the kinase activity assay on a small panel of 35 kinases showed that the kinase selectivity of compound 2 was superior to that of the first-generation inhibitor ibrutinib, suggesting that compound 2 could be a second-generation inhibitor of BTK. In conclusion, we identified a potent and highly selective BTK inhibitor worthy of further development.

Overview of Current Targeted Anti-Cancer Drugs for Therapy in Onco-Hematology

The upgraded knowledge of tumor biology and microenviroment provides information on differences in neoplastic and normal cells. Thus, the need to target these differences led to the development of novel molecules (targeted therapy) active against the neoplastic cells' inner workings. There are several types of targeted agents, including Small Molecules Inhibitors (SMIs), monoclonal antibodies (mAbs), interfering RNA (iRNA) molecules and microRNA. In the clinical practice, these new medicines generate a multilayered step in pharmacokinetics (PK), which encompasses a broad individual PK variability, and unpredictable outcomes according to the pharmacogenetics (PG) profile of the patient (e.g., cytochrome P450 enzyme), and to patient characteristics such as adherence to treatment and environmental factors. This review focuses on the use of targeted agents in-human phase I/II/III clinical trials in cancer-hematology. Thus, it outlines the up-to-date anticancer drugs suitable for targeted therapies and the most recent finding in pharmacogenomics related to drug response. Besides, a summary assessment of the genotyping costs has been discussed. Targeted therapy seems to be an effective and less toxic therapeutic approach in onco-hematology. The identification of individual PG profile should be a new resource for oncologists to make treatment decisions for the patients to minimize the toxicity and or inefficacy of therapy. This could allow the clinicians to evaluate benefits and restrictions, regarding costs and applicability, of the most suitable pharmacological approach for performing a tailor-made therapy.

Molecular regulation of dendritic cell development and function in homeostasis, inflammation, and cancer

Dendritic cells (DCs) are the principal antigen-presenting cells of the immune system and play key roles in controlling immune tolerance and activation. As such, DCs are chief mediators of tumor immunity. DCs can regulate tolerogenic immune responses that facilitate unchecked tumor growth. Importantly, however, DCs also mediate immune-stimulatory activity that restrains tumor progression. For instance, emerging evidence indicates the cDC1 subset has important functions in delivering tumor antigens to lymph nodes and inducing antigen-specific lymphocyte responses to tumors. Moreover, DCs control specific therapeutic responses in cancer including those resulting from immune checkpoint blockade. DC generation and function is influenced profoundly by cytokines, as well as their intracellular signaling proteins including STAT transcription factors. Regardless, our understanding of DC regulation in the cytokine-rich tumor microenvironment is still developing and must be better defined to advance cancer treatment. Here, we review literature focused on the molecular control of DCs, with a particular emphasis on cytokine- and STAT-mediated DC regulation. In addition, we highlight recent studies that delineate the importance of DCs in anti-tumor immunity and immune therapy, with the overall goal of improving knowledge of tumor-associated factors and intrinsic DC signaling cascades that influence DC function in cancer.

Acalabrutinib, A Second-Generation Bruton's Tyrosine Kinase Inhibitor

The Bruton's tyrosine kinase (BTK) is an essential in the B-cell receptor (BCR) signaling pathway which was identified as crucial in the pathogenesis of B-cell malignancies. Ibrutinib, a first-in-class BTK inhibitor, has been approved for the treatment of distinct B-cell malignancies. To overcome off-target side effects of and emerging resistances to ibrutinib, more selective second-generation BTK inhibitors were developed. Acalabrutinib is a novel second-generation BTK inhibitor and has shown promising safety and efficacy profiles in phase 1/2 clinical trials in patients with relapsed CLL and pretreated MCL. Recently, acalabrutinib was approved by the FDA for treatment of adult patients with MCL who received at least one prior therapy. However, clinical trials on a direct comparison between ibrutinib and acalabrutinib and on combination treatment options with other agents as CD20 antibodies are warranted.

Bruton's tyrosine kinase (BTK) inhibitors in treating cancer: a patent review (2010-2018)

INTRODUCTION

Bruton's tyrosine kinase (BTK) plays a critical role in the regulation of survival, proliferation, activation and differentiation of B-lineage cells. It participates by regulating multiple cellular signaling pathways, including B cell receptor and FcR signaling cascades. BTK is abundantly expressed and constitutively active in the pathogenesis of B cell hematological malignancies, as well as several autoimmune diseases. Therefore, BTK is considered as an attractive target for treatment of B-lineage lymphomas, leukemias, and some autoimmune diseases. Many industry and academia efforts have been made to explore small molecular BTK inhibitors.

AREAS COVERED

This review aims to provide an overview of the patented BTK inhibitors for the treatment of cancer from 2010 to 2018.

EXPERT OPINION

BTK inhibitors attract much interest for their therapeutic potential in the treatment of cancers and autoimmune diseases, especially for B cell hematological malignancies. In 2013, ibrutinib was approved by the FDA as the first-in-class BTK inhibitors for the treatment of mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL), and now it is also undergoing clinical evaluation for other indications in either single or combined therapy. It is clear that BTK inhibitors can provide a promising clinical benefit in treating B-lineage lymphomas and leukemias.

Review of Bruton tyrosine kinase inhibitors for the treatment of relapsed or refractory mantle cell lymphoma

Mantle cell lymphoma (mcl) is a rare subtype of aggressive B-cell non-Hodgkin lymphoma that remains incurable with standard therapy. Patients typically require multiple lines of therapy, and those with relapsed or refractory (r/r) disease have a very poor prognosis. The Bruton tyrosine kinase (btk) inhibitor ibrutinib has proven to be an effective agent for patients with r/r mcl. Although usually well tolerated, ibrutinib can be associated with unique toxicities, requiring discontinuation in some patients. Effective and well-tolerated alternatives to ibrutinib for patients with r/r mcl are therefore needed. Novel btk inhibitors such as acalabrutinib, zanubrutinib, and tirabrutinib are designed to improve on the safety and efficacy of first-generation btk inhibitors such as ibrutinib. Data from single-arm clinical trials suggest that, compared with ibrutinib, second-generation btk inhibitors have comparable efficacy and might have a more favourable toxicity profile. Those newer btk inhibitors might therefore provide a viable treatment option for patients with r/r mcl.

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.

Development of BTK inhibitors for the treatment of B-cell malignancies

BTK is a key component of B-cell receptor signaling and functions as an important regulator of cell proliferation and survival in B-cell malignancies. The first-in-class BTK inhibitor ibrutinib is a small molecule drug that binds covalently to BTK and has been proved to be an effective treatment for various B-cell malignancies. However, it has off-target activities on non-BTK kinases that are related to side effects or might be translated into clinical limitations, with resistance to ibrutinib also reported. Much progress has been made in the development of more selective and second-generation BTK inhibitors. A recent shift in the mechanisms of action of BTK inhibitors is noteworthy, and novel inhibitors acting through noncovalent BTK inhibition are now being developed. This review describes key characteristics of ibrutinib, including current issues of its clinical use, and summarizes preclinical properties and clinical developments of second-generation BTK inhibitors for the treatment of B-cell malignancies. A review of novel noncovalent BTK inhibitors are also included.

Targeting the B-cell receptor pathway: a review of current and future therapies for non-Hodgkin's lymphoma

INTRODUCTION

The B-cell receptor (BCR) pathway is a crucial aspect of mature lymphocytes and is maintained in B-cell neoplasms. Many small module inhibitors targeting kinases within the BCR pathway are approved, with others in development, offering alternative treatment options to standard chemoimmunotherapy. Areas covered: This review covers both approved inhibitors and investigational inhibitors of spleen tyrosine kinase (SYK), Bruton's tyrosine kinase (BTK), and phosphoinositide-3-kinase (PI3K) in the treatment of B-cell lymphomas. To collect relevant articles, a literature search was completed through the use of PubMed and abstracts from ASH and ASCO national meetings. Search terms including non-Hodgkin lymphoma, and BCR inhibitors, as well as the individual drug names, were utilized. The majority of included studies are dated from 2012 to March 2018. Expert opinion: BCR pathway inhibitors, such as ibrutinib and idelalisib, are novel treatments for non-Hodgkin lymphomas. While providing alternative treatment options to those with high-risk disease, poor functional status, and relapsed disease, outside of chronic lymphocytic leukemia (CLL), they have been limited to the relapsed/refractory setting. Their mechanisms of action, off/on-target effects, and resistance patterns create unique therapeutic dilemmas. It is our opinion that more specific inhibitors, as well as combination therapy, will define the future for BCR inhibitors.

The B cell receptor signaling pathway in mantle cell lymphoma

Signal transduction through the constitutively activated B cell receptor (BCR) plays a key role in the pathogenesis of B-cell tumors by promoting survival and proliferation of malignant B cells. The BCR signaling pathway is known to be deregulated in Mantle Cell Lymphoma (MCL) due to mutations or epigenetic events that impact regulatory proteins. One such protein is Bruton's tyrosine kinase (BTK), an integral component of the BCR signaling pathway. The success of ibrutinib, a BTK inhibitor, and other drugs that target components of the BCR pathway is evidence that regulation of the BCR signaling pathway is an effective method of MCL treatment. The complexity of the pathway indicates that it contains other potential therapeutic targets for the treatment of MCL. This is supported by recent and ongoing clinical trials of inhibitors of molecules such as PI3K, BCL-2, and BTK that show promising initial results. Additionally, agents that target different points of the pathway may have synergistic effects when used in combination. This review provides a description of the BCR signaling pathway on the molecular level followed by an explanation of its relationship to MCL. The role of the BCR signaling pathway in the pathogenesis of MCL is explained through an overview of the drugs that target BCR signaling in MCL treatment.

Loss of thyroid hormone receptor interactor 13 inhibits cell proliferation and survival in human chronic lymphocytic leukemia

Background

The genetic regulation of apoptosis and cell proliferation plays a role in the growth of chronic lymphocytic leukemia (CLL), the most common form of leukemia in the Western hemisphere. Although thyroid hormone receptor interactors (TRIPs) are known to play roles in cell cycle, the potential involvement of the novel family member TRIP13 in CLL has not yet been investigated.

Methods

Quantitative PCR (qPCR) was used to detect expression of TRIP13 in 36 CLL patients and 33 healthy donors CD19+ B cells. Loss-of-function (siRNA) assays were used to alter TRIP13 expression levels. The effect of TRIP13 on cell proliferation and apoptosis was measured by MTT, Annexin V-based flow cytometry and Caspase 3/7 activity assay. Affymetrix GeneChip and Ingenuity Pathway Analysis (IPA) were used to describe an overview of TRIP13 potential biological function and downstream pathways. Dual-luciferase reporter assay was performed to assess the promoting effect of c-MYC on TRIP13 transcription.

RESULTS

The qPCR data showed that TRIP13 is significantly over-expressed in CLL patients. Microarray analyses indicated that the biological function of TRIP13 in CLL is majorly cell apoptosis and cell proliferation associated. TRIP13 siRNA expressing cells exhibited a slower cell proliferation rate and underwent apoptosis compared with control cells. TRIP13 knockdown induced CLL cells apoptosis through PUMA independent of p53. TRIP13 up-regulation is induced by c-MYC dependent transcriptional activation.

Conclusion

Overall, our data suggest the bio-function of TRIP13 in CLL cell for the first time, and that this gene might be a therapeutic target for CLL.

Novel synthetic drugs currently in clinical development for chronic lymphocytic leukemia

INTRODUCTION

Over the last few years, several new synthetic drugs, particularly Bruton's tyrosine kinase (BTK), phosphatidylinositol 3-kinase (PI3K) and BCL-2 inhibitors have been developed and investigated in chronic lymphocytic leukemia (CLL). Areas covered: This review highlights key aspects of BTK, PI3K and BCL-2 inhibitors that are currently at various stages of preclinical and clinical development in CLL. A literature review of the MEDLINE database for articles in English concerning CLL, B-cell receptor, BCL-2 antagonists, BTK inhibitors and PI3K inhibitors, was conducted via PubMed. Publications from 2000 through July 2017 were scrutinized. The search terms used were acalabrutinib, ACP-196, BGB-3111, ONO-4059, GS-4059, duvelisib, IPI-145, TGR-1202, copanlisib, Bay 80-6946, buparlisib, BKM-120, BCL-2 inhibitors, venetoclax, ABT-263, navitoclax, CDK inhibitors, alvocidib, flavopiridol, dinaciclib, SCH 727,965, palbociclib, PD-0332991, in conjunction with CLL. Conference proceedings from the previous five years of the ASH and EHA Annual Scientific Meetings were searched manually. Additional relevant publications were obtained by reviewing the references from the chosen articles. Expert opinion: The use of new synthetic drugs is a promising strategy for the treatment of CLL. Data from ongoing and future clinical trials will aid in better defining the status of new drugs in the treatment of CLL.

A Small Molecule Inhibitor of Bruton's Tyrosine Kinase Involved in B-Cell Signaling

Protein kinases are fundamental within almost all cellular signal transduction networks. Among these, Bruton's tyrosine kinase (Btk), which belongs to the Tec family of proteins, plays an imperative part in B-cell signaling. Owing to its role, Btk has been established as an important therapeutic target for a vast range of disorders related to B-cell development and function, such as the X-linked agammaglobulinemia, various B-cell malignancies, inflammation, and autoimmune diseases. Herein, using computer-based screening of a library of 20 million small molecules, we identified a small molecule capable of directly binding the Btk kinase domain. On the basis of this hit compound, we conducted a focused structure-similarity search to explore the effect of different chemical modifications on binding toward Btk. This search identified the molecule N2,N6-bis(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-9H-purine-2,6-diamine as a potent inhibitor of Btk. The latter small molecule binds Btk with a dissociation constant of 250 nM and inhibits Btk activity both in vitro and in-cell.

Syk inhibitors in clinical development for hematological malignancies

Spleen tyrosine kinase (Syk) is a cytosolic non-receptor protein tyrosine kinase (PTK) and is mainly expressed in hematopoietic cells. Syk was recognized as a critical element in the B-cell receptor signaling pathway. Syk is also a key component in signal transduction from other immune receptors like Fc receptors and adhesion receptors. Several oral Syk inhibitors including fostamatinib (R788), entospletinib (GS-9973), cerdulatinib (PRT062070), and TAK-659 are being assessed in clinical trials. The second generation compound, entospletinib, showed promising results in clinical trials against B-cell malignancies, mainly chronic lymphoid leukemia. Syk inhibitors are being evaluated in combination regimens in multiple malignancies.

Population Pharmacokinetics and Exposure Response Assessment of CC-292, a Potent BTK Inhibitor, in Patients With Chronic Lymphocytic Leukemia

CC‐292, a potent Bruton tyrosine kinase inhibitor, is under development for the treatment of B‐cell malignancies. An analysis was performed to develop a population pharmacokinetic model of CC‐292 and assess the influence of demographics and disease‐related covariates on CC‐292 exposure and to assess the exposure‐response (overall response rate) relationship in patients with chronic lymphocytic leukemia. Population pharmacokinetic analysis was based on a 2‐compartment base model conducted in NONMEM. Categorical exposure‐response analysis was performed using logistic regression in SAS. The population pharmacokinetic analysis results indicated that CC‐292 pharmacokinetic disposition is similar between healthy subjects and patients. CC‐292 showed a larger central compartment volume of distribution than the peripheral compartment volume of distribution (158 L and 72 L, respectively) and a faster clearance than intercompartmental clearance (134 L/h and 18.7 L/h, respectively), indicating that for CC‐292, clearance from blood occurs faster than distribution into deep tissues and organs. CC‐292 clearance is not affected by demographics or baseline clinical lab factors, except for sex. Although sex significantly reduced variation of apparent clearance, the sex effect on apparent clearance is unlikely to be clinically relevant. The exposure‐response analysis suggested that higher drug exposure is linearly correlated with higher overall response rate. A twice‐daily dose regimen showed higher overall response rate as compared to once‐daily dosing, consistent with a threshold concentration of approximately 300 ng/mL, above which the probability of overall response rate significantly increases.

Diagnosis and treatment of CD20 negative B cell lymphomas

CD20 negative B cell non-Hodgkin lymphoma (NHL) is rare and accounts for approximately 1-2% of B cell lymphomas. CD20- negative NHL is frequently associated with extranodal involvement, atypical morphology, aggressive clinical behaviour, resistance to standard chemotherapy and poor prognosis. The most common types of these include plasmablastic lymphoma, primary effusion lymphoma, large B-cell lymphoma arising from HHV8-associated multicentric Castleman’s disease, and ALK+ large B cell lymphoma. This review provides an overview of the diagnostic and treatment modalities for CD20 negative B cell NHL.