Emerging antiangiogenics for renal cancer

Introduction: Antiangiogenic therapy is considered to be the backbone of treatment strategy in metastatic renal cell carcinoma (mRCC). New, more focused, targeted drugs are emerging, while other targeted drugs oriented toward resistance or alternative mechanisms are under development.

Areas covered: Antiangiogenic agents include two types of agents: the monoclonal antibody, targeting vascular endothelial growth factor (VEGF), bevacizumab and the tyrosine kinase inhibitors (TKIs). Data regarding efficacy and safety of these agents are reported. Differences between the first generation of TKIs, sunitinib, sorafenib, and the new generation, pazopanib, axitinib and tivozanib are also detailed. Most of these agents have been approved in the treatment of kidney cancer in specific settings of the disease.

Expert opinion: The class of antiangiogenic drugs for treatment of mRCC is already relatively full. After ‘me-too' drugs, more targeted drugs against VEGFR have been developed but have to demonstrate a benefit in first-line treatment. Another option for the development is to combine a known drug with an antiangiogenic inhibition profile and at least one additional target involved in resistance to an antiangiogenic or in an alternative pathway. The cost of approach with targeted drugs, including antiangiogenics, has led to a tremendous increase in the cost of care in mRCC.     

Emerging therapeutics in refractory renal cell carcinoma

Introduction: Metastatic renal cell carcinoma (mRCC) has seen the introduction of numerous new treatments over the past decade. However, the efficacy of these therapies has plateaued, and new treatment options are needed for the majority of patients with mRCC whose disease inevitably progresses through one or more standard therapies (‘refractory’ mRCC). Recently approved agents in this space have shown great promise.

Areas covered: This article reviews the evidence behind current management strategies for mRCC. After reviewing clinical trials that established current first-line therapies and agents used in the refractory setting, we address new ideas for the treatment of refractory disease including combination therapies and novel targeted agents. In particular, we focus on targeted immunotherapy in refractory mRCC. We conclude by considering future directions in combination treatments utilizing these novel agents.

Expert opinion: Numerous approaches have produced tangible benefits for the treatment of patients with mRCC. These include development of next generation VEGFR/TKIs, targeted immunotherapy agents, and the development of combined regimens. In particular, immunotherapy agents targeting the PD1/PD-L1 pathway have shown great promise with a robust survival advantage seen in patients treated with nivolumab. A tolerable side effect profile of immunotherapy agents makes them amenable for use in combination therapies and ongoing trials are addressing this question.     

Comparative effectiveness of everolimus and axitinib as second targeted therapies for metastatic renal cell carcinoma in the US: a retrospective chart review

Background Second targeted therapies for metastatic renal cell carcinoma (mRCC) include mammalian target of rapamycin inhibitors (mTORis) and tyrosine kinase inhibitors (TKIs). This observational study compares overall survival (OS) and progression-free survival (PFS) of patients treated with everolimus (an mTORi) and axitinib (a TKI) following first TKI, and assesses the impact of type and duration of first TKI on the relative effectiveness of these second targeted therapies.

Methods Retrospective reviews of medical records were conducted by medical oncologists or hematologists/oncologists recruited from a nationwide panel. Included patients with mRCC were required to have discontinued a first TKI (sunitinib, sorafenib, or pazopanib) for medical reasons, and to have initiated everolimus or axitinib as second targeted therapy between February 2012 and January 2013. OS and PFS were compared between patients treated with everolimus vs. axitinib using multivariable Cox proportional hazards regression models. Comparative results were also stratified by type and duration of first TKI.

Results Included patients (n?=?325 for everolimus and n?=?127 for axitinib) had a mean age of 61 years and 31% were female. Sunitinib was the most commonly used first TKI (73%). After adjusting for patient characteristics, no statistically significant differences were observed in OS or PFS between everolimus and axitinib. When stratifying by type and duration of first TKI, there was no statistically significant difference in OS between everolimus and axitinib in all subgroups except for patients with?<6 months on sunitinib or sorafenib as first TKI. No significant difference in PFS was observed in any subgroup.

Limitations Important limitations include potential missing or inaccurate data in medical charts, and confounding due to unobserved factors.

Conclusions In this retrospective chart review, no significant differences were detected in OS or PFS between axitinib and everolimus as second targeted therapy. Longer duration of first TKI was not associated with increased effectiveness of subsequent axitinib compared to everolimus.     

AIT-082, a novel purine derivative with neuroregenerative properties

Introduction: The interaction between the VEGFRs and their ligands plays an important role in tumor angiogenesis. Despite a series of problems encountered during early work on blocking growth factors, current evidence injects further vigor into researching the modulation of VEGFR activity. Emerging preclinical and clinical studies suggest that attenuating receptor activity can synergistically promote antitumor action if utilized concurrently with conventional therapies.

Areas covered: This review presents an up-to-date assessment of the potential role of modulating receptor activities in various cancers. The sentinel work on the proof of principles in various animal models, and the current translational research on these small molecule inhibitors and receptor blocking antibodies, from Phase I to Phase III trials, has been systematically examined with an emphasis on agents in earlier stages of development.

Expert opinion: Many clinical trials are ongoing, but early phase trials show promising results. Recently, there has been a huge explosion of research activity either in the development of new drugs or in the understanding its biology. Many current trials lend support to the rationale behind these therapies, which can function as adjuvants to conventional treatments. It has been argued that normalization of tumor-induced vasculature can promote better drug delivery and prevent resistance to radiotherapy. However, strategies involving the inhibition of the interaction of VEGFRs with ligands and their downstream pathways are not, in general, at a stage where it will be directly useful in clinical cancer treatment. A deeper understanding of these biologic therapies will help to improve the efficacy of conventional treatments and furthermore reduce dose-dependent cytotoxic activity.     

Emerging drugs for the treatment of bone metastasis

Introduction: Bone metastases are virtually incurable resulting in significant disease morbidity, reduced quality of life and mortality. Bone provides a unique microenvironment whose local interactions with tumor cells offer novel targets for therapeutic interventions. Increased understanding of the pathogenesis of bone disease has led to the discovery and clinical utility of bone-targeted agents other than bisphosphonates and denosumab, currently, the standard of care in this setting.

Areas covered: In this review, we present the recent advances in molecular targeted therapies focusing on therapies that inhibit bone resorption and/or stimulate bone formation and novel anti-tumoral agents that exerts significant effects on skeletal metastases, nowadays available in clinical practice or in phase of development.

Expert opinion: New emergent bone target therapies radium-223, mTOR inhibitors, anti-androgens have demonstrated the ability to increase overall survival in bone metastatic patients, other compounds, such as ET-1 and SRC inhibitors, up to now failed to clearly confirm in clinical trials their promising preclinical data.     

Lenvatinib for use in combination with everolimus for the treatment of patients with advanced renal cell carcinoma following one prior anti-angiogenic therapy

Introduction: In patients with mRCC options for second line therapies, following progression on anti-angiogenic agents, that demonstrate a survival advantage in clinical trials have been limited. Recently a number of agents have demonstrated efficacy in this setting. Here in we profile one such therapy, the combination of lenvatinib and everolimus, and discuss the expanded options for therapy available in this setting.

Areas covered: In this review, we discuss current algorithms for treatment of mRCC in both the first-line and second-line setting. We discuss the recent addition of cabozantinib and nivolumab, in the second line setting, to the market. Lenvatinib’s pharmacology, clinical efficacy and toxicity profile is discussed. A comprehensive literature review was performed using PUBMED.

Expert commentary: The current treatment algorithms for mRCC will likely see significant change in the coming years. The addition of immunotherapy to our treatment options in mRCC is of particular importance. Future trials examining the use of immunotherapy, both as monotherapy and in combination with VEGF targeted therapy, will likely be a dominant influence in the therapeutic landscape of mRCC. Progress in terms of the rapid expansion of available active therapies in mRCC needs to be balanced with current deficiencies in terms of predictive biomarkers.     

Axitinib for the management of metastatic renal cell carcinoma

In recent years, targeted agents have changed the treatment landscape for patients with advanced renal cell carcinoma (RCC), greatly improving treatment outcomes. Several targeted agents are now licensed for the treatment of metastatic RCC (mRCC), and a number of new agents are under investigation. Axitinib, a small molecule indazole derivative is an oral, potent multitargeted tyrosine kinase receptor inhibitor, which selectively inhibits vascular endothelial growth factor receptors (VEGFR)-1, -2, and -3 at subnanomolar concentrations, in vitro. In various nonclinical models, axitinib has demonstrated in vivo target modulation and antiangiogenesis. In pharmacokinetic studies, axitinib administered orally with food at the proposed regimen of 5mg twice daily continuous daily dosing, is rapidly absorbed, reaching peak concentrations within 2–6 hours. Axitinib is metabolized primarily in the liver via the cytochrome P450 (CYP) system with less than 1% of the administered drug passing unchanged in the urine. The pharmacokinetics of axitinib do not appear to be altered by coadministered chemotherapies, and antacids do not have a clinically significant effect. However, coadministration with CYP3A4 and 1A2 inducers is contraindicated. In addition, proton pump inhibitors reduce the rate of axitinib absorption. Increased axitinib exposure is associated with higher efficacy indicated by decreased tumor perfusion and volume. In three phase II clinical trials in patients with advancedRCCpreviously treated with cytokines, chemotherapy or targeted agents, axitinib has demonstrated antitumor activity with a favorable noncumulative toxicity profile. In one study of Western patients with cytokine-refractory mRCC, an objective response rate (ORR) of 44.2% (95% CI 30.5, 58.7) was achieved. The median time to progression was 15.7 months (95%CI 8.4, 23.4) and the median overall survival (OS) was 29.9 months (95%CI 20.3, not estimable). In the second study of patients with sorafenib-refractory mRCC, ORR was 22.6% (95% CI 12.9, 35.0). The median progression-free survival (PFS) was 7.4 months (95% CI 6.7, 11.0) and a median OS of 13.6 months (95% CI 8.4, 18.8) was achieved. Results from the third study in Japanese patients with cytokine-refractory mRCC reported an ORR of 55% and median PFS of 12.9 months (95% CI 9.8, 15.6).In the three studies, themost common adverse events reported were fatigue, hypertension, hand-foot syndrome (HFS), and gastrointestinal toxicity, which were generally manageable with standard medical intervention. Of note, the incidence of HFS and proteinuria in the Japanese study was higher than that reported in the Western study in cytokine-refractory mRCC patients.An observed association between diastolic blood pressure ≥90 mmHg and increased efficacy suggests potential use as a prognostic biomarker. However, this requires further investigation. Two randomized phase III clinical trials are ongoing to determine the efficacy of axitinib in patients with mRCC in the first- and second-line setting. These results will help to determine the place of axitinib in the mRCC treatment algorithm.     

The clinical development of histone deacetylase inhibitors as targeted anticancer drugs

Importance of the field: Histone deacetylase (HDAC) inhibitors are being developed as a new, targeted class of anticancer drugs.

Area covered in this review: This review focuses on the mechanisms of action of the HDAC inhibitors, which selectively induce cancer cell death.

What the reader will gain: There are 11 zinc-dependent HDACs in humans and the biological roles of these lysine deacetylases are not completely understood. It is clear that these different HDACs are not redundant in their activity. This review focuses on the mechanisms by which HDAC inhibitors can induce transformed cell growth arrest and cell death, inhibit cell mobility and have antiangiogenesis activity. There are more than a dozen HDAC inhibitors, including hydroxamates, cyclic peptides, benzamides and fatty acids, in various stages of clinical trials and many more compounds in preclinical development. The chemically different HDAC inhibitors may target different HDACs.

Take home message: There are extensive preclinical studies with transformed cells in culture and tumor-bearing animal models, as well as limited clinical studies reported to date, which indicate that HDAC inhibitors will be most useful when used in combination with cytotoxic or other targeted anticancer agents.     

Molecular targeted therapy in recurrent glioblastoma: current challenges and future directions

Introduction: The survival of patients with glioblastoma (GBM), which is the most common primary brain malignancy, remains poor with current treatment modalities. However, an enhanced understanding of gliomagenesis is supporting the development of targeted molecular therapies with the potential for improving clinical outcomes.

Areas covered: Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor (VEGFR) initiate key signaling pathways in GBM; however, trials with anti-EGFR agents have failed to show improved outcomes. Bevacizumab, a monoclonal antibody targeting VEGF, remains the only FDA-approved molecular drug in GBM; yet its use has only improved progression-free survival without any improvement in overall survival. We review the evidence supporting the continued evaluation of targeted molecular therapies in recurrent GBM. In addition, newer potential therapies targeting other signaling pathways, heat shock proteins and proteosomes, as well as the concept of targeting glioma stem cells are discussed.

Expert opinion: The complex genetic origin of GBM makes it challenging to identify molecular subsets that may benefit from specific targeted therapies. Pathway inhibition, via multisite kinase inhibitors or a carefully selected combination of molecular drugs with or without cytotoxic agents, is currently undergoing evaluation in clinical trials and may improve outcomes in these patients.     

Sunitinib malate for the treatment of renal cell carcinoma

Introduction: Over the past decade, a greater understanding into the molecular pathogenesis of renal cell carcinoma (RCC) has led to major advances in treatment options. Sunitinib is an oral, small-molecule, multi-targeted receptor tyrosine kinase inhibitor (TKI) that targets a number of receptors, including vascular endothelial growth factor receptors (VEGFR) and platelet-derived growth factor receptors (PDGFR). Sunitinib was one of the first targeted agents studied in metastatic RCC (mRCC) and is currently used worldwide in the management of mRCC.

Areas covered: This drug evaluation addresses the preclinical and clinical development of sunitinib. It provides an in-depth discussion of the Phase II data that led to its approval in mRCC and the subsequent Phase III clinical trial comparing sunitinib to interferon-α. More recent data from the large international expanded access trial, in non-clear cell carcinoma patients, different dosing schedule studies and safety issues are also discussed. Finally, areas for the future use of sunitinib, including in the adjuvant setting, are reviewed.

Expert opinion: Since the FDA approved sunitinib for advanced RCC in January 2006, much more has been learned about its efficacy and tolerability. Over the past decade of its clinical use, it has become clear that expertise is required when prescribing sunitinib, in terms of maximizing dose, anticipating and managing side effects, and assessing responses. In the future, a better understanding of sunitinib's role compared with other VEGF TKIs and mTOR inhibitors, and in other roles such as the adjuvant setting or in non-clear cell pathology, will become evident.     

Pazopanib for the treatment of renal cancer

Introduction: Dramatic advances in the care of patients with advanced renal cell carcinoma (RCC) have occurred over the last 10 years. Insights into the molecular pathogenesis of this disease have elucidated the importance of signaling cascades related to angiogenesis in the management of RCC. Pazopanib is a novel, small-molecule tyrosine kinase inhibitor that targets vascular endothelial growth factor receptors (VEGFR)-1, -2, and -3; platelet-derived growth factor receptors (PDGFR)-α and -β; and c-kit tyrosine kinases. Pazopanib exhibits distinct pharmacokinetic and toxicity profiles compared with other agents in the class of VEGF signaling pathway inhibitors.

Areas covered: This review discusses the scientific rationale for the development of pazopanib, as well as the preclinical and clinical trials that led to the approval of pazopanib for patients with advanced RCC. The most recent information, including data from the 2010 meeting of the American Society of Clinical Oncology and the design of ongoing Phase III trials, is discussed. Finally, an algorithm utilizing level I evidence for the treatment of patients with this disease is proposed.

Expert opinion: The treatment of metastatic RCC has changed dramatically over the last 5 years. Six novel agents – sunitinib, sorafenib, temsirolimus, everolimus, bevacizumab (used in combination with interferon), and pazopanib (Votrient) – have been approved for the treatment of metastatic RCC. The clinical data to date clearly place pazopanib among the most active of the targeted therapies.     

DNA synthesis inhibitors for the treatment of gastrointestinal cancer

Introduction: Intensive laboratory, preclinical and clinical studies have identified and validated molecular targets in cancers, leading to a shift toward the development of novel, rationally designed and specific therapeutic agents. However, gastrointestinal cancers continue to have a poor prognosis, largely due to drug resistance.

Areas covered: Here, we discuss the current understanding of DNA synthesis inhibitors and their mechanisms of action for the treatment of gastrointestinal malignancies.

Expert opinion: Conventional agents, including DNA synthesis inhibitors such as fluoropyrimidines and platinum analogs, remain the most effective therapeutics and are the standards against which new drugs are compared. Novel DNA synthesis inhibitors for the treatment of gastrointestinal malignancies include a combination of the antimetabolite TAS-102, which consists of trifluorothymidine with a thymidine phosphorylase inhibitor, and a novel micellar formulation of cisplatin NC-6004 that uses a nanotechnology-based drug delivery system. The challenges of translational cancer research using DNA synthesis inhibitors include the identification of drugs that are specific to tumor cells to reduce toxicity and increase antitumor efficacy, biomarkers to predict pharmacological responses to chemotherapeutic drugs, identification of ways to overcome drug resistance and development of novel combination therapies with DNA synthesis inhibitors and other cancer therapies, such as targeted molecular therapeutics. Here, we discuss the current understanding of DNA synthesis inhibitors and their mechanisms of action for the treatment of gastrointestinal malignancies.     

Protein kinase inhibitors in renal cell carcinoma

Introduction: Metastatic Renal Cell Carcinoma (mRCC) was historically treated with cytokine therapy with a poor outcome. In the last decade, new therapies targeting vascular endothelial growth factor (VEGF) or the mammalian target of rapamycin (m-TOR) pathways demonstrated efficacy in mRCC. Protein kinase inhibitors as well as monoclonal antibodies targeting these pathways have become the standard treatment of renal cell carcinoma (RCC) in the first-line setting and beyond.

Areas covered: This review describes the various Phase III trials concerning protein kinase inhibitors including anti-angiogenic tyrosine kinase inhibitors (TKIs) and m-TOR serine/threonine kinase inhibitors, which have demonstrated a benefit in the treatment of mRCC. It focuses on efficacy, safety and management.

Expert opinion: VEGF TKI and m-TOR inhibitors have significantly improved the outcome of mRCC and offer a gain in survival by sequential treatments for the majority of patients. But they induce a particular toxicity profile. An adequate management of each drug and its sequence in treatment is essential to optimise the outcome and preserve the quality of life (QoL) of patients with mRCC. In forthcoming years, pending results should indicate whether VEGF TKI are of interest in an adjuvant setting and if new drugs targeting will challenge the current standard guidelines in the metastatic setting.     

Clinical investigation of receptor and non-receptor tyrosine kinase inhibitors for the treatment of epithelial ovarian cancer

Introduction: Epithelial ovarian cancer (EOC) is the second most common gynecologic malignancy and the leading cause of death from gynecologic cancer in the USA. EOC is an exquisitely chemo-sensitive disease with response rates of over 75% in the upfront setting. Despite this, due to high rates of recurrence and development of chemo-resistance, the overall survival of EOC remains about 25%. Thus, there is a great need for new therapeutic approaches to render more durable responses. Based on preclinical and early phase clinical studies, key targeted pathways include targets that drive angiogenesis and chemo-resistance. Receptor tyrosine kinases and non-receptor tyrosine kinases play important roles in these processes and several small molecule tyrosine kinase inhibitors (TKIs) are in clinical development.

Areas covered: This review summarizes clinical rationale, mechanisms of action and clinical data for the TKIs under evaluation in the Phase III setting for EOC.

Expert opinion: Despite reasonable preclinical activity, small molecule TKIs are unlikely to improve patient survival as single agent therapies in an unselected EOC population. Incorporation of tissue evaluation during ongoing clinical trials is required to identify molecularly defined groups that respond to single agents and direct rational combination strategies based on mechanisms of resistance to improve outcomes in EOC.     

Emerging targeted therapies for melanoma

Introduction: Melanoma is an aggressive cutaneous malignancy associated with poor response to traditional therapies. Recent regulatory approval for immune checkpoint inhibitors and agents targeting mutated BRAF has led to a tremendous expansion of effective treatment options for patients with advanced melanoma. Unfortunately, primary or acquired resistance develops in most patients, highlighting the need for additional therapies. Numerous genetic and other molecular features of this disease may provide effective targets for therapy development.

Areas covered: This article reviews available melanoma treatments, including immune and molecularly-targeted therapies. We then discuss agents in development, with a focus on targeted (rather than immune) therapies. In particular, we discuss agents that block mitogen-activated protein kinase (MAPK) signaling, as well as other emerging approaches such as antibody-drug conjugates, cell-cycle targeting, and novel genetically-informed clinical trials.

Expert opinion: Despite the incredible advances in melanoma therapeutics over the last several years, a clear need to develop more effective therapies remains. Molecularly-targeted therapy approaches will likely remain a cornerstone of melanoma treatment in parallel to immune therapy strategies.     

Pharmacoeconomic and clinical implications of sequential therapy for metastatic renal cell carcinoma patients in Central and Eastern Europe

Introduction: The incidence and mortality rates of kidney cancer in the Central and Eastern European (CEE) region are among the highest in the world. Access to second and subsequent lines of metastatic renal cell carcinoma (mRCC) therapies is highly varied in the region. Despite the increasing body of evidence supporting the clinical benefit of multiple lines of treatment, access to treatment beyond first line is restricted in many of these countries.

Areas covered: The adoption of targeted therapies for the first-line treatment of mRCC in the region was slow and faced many obstacles. In order to evaluate the current status of treatment beyond the first-line setting in the CEE region, this review examines the availability and reimbursement of mRCC drugs and clinical practice in institutions that treat patients with mRCC.

Expert opinion: This review highlights the need to raise awareness among physicians, payers and regulators on clinical trial and cost-effectiveness data regarding the treatment of mRCC beyond the first line. The obstacles to mRCC drug access highlighted in this review need to be overcome to ensure that patients are receiving the best treatment available.     

Anti-angiogenic therapies for malignant pleural mesothelioma

Introduction: Malignant pleural mesothelioma (MPM) is a disease with a dismal prognosis. Currently available treatments have modest results. Therefore, new agents and new treatment strategies are eagerly awaited by patients and clinicians. Preclinical and clinical studies have shown that angiogenesis plays a very important role in MPM. Therefore, a great hope has been placed in the use of anti-angiogenic agents in this disease.

Areas covered: Studies regarding anti-angiogenic treatments in MPM with bevacizumab, tyrosine-kinase inhibitors (TKIs) and other agents were critically analyzed, with an overview of ongoing trials and future perspectives, including research on biomarkers.

Expert opinion: The clinical use of angiogenesis inhibitors in MPM patients has resulted more challenging than anticipated. The intrinsic complexity of neo-angiogenesis, and its redundant regulatory mechanisms, suggests that multiple and different biomarkers are needed to predict efficacy of anti-angiogenic agents and to monitor their biological and therapeutic effects. The growing understanding of the molecular alterations and key pathways that underlie the resistance to VEGF inhibitors will allow to design studies of the combination of agents targeting these pathways with anti-VEGF therapies. Only a tight integration of preclinical and clinical studies will allow to achieve a real progress in MPM patients with this therapeutic strategy.     

RET inhibition: implications in cancer therapy

Introduction: The RET gene encodes a receptor tyrosine kinase essential for ontogenesis of the enteric nervous system and kidney. Following identification of RET, it was found that somatic rearrangements of this gene, conventionally designated as RET/PTC, are frequently present in papillary thyroid carcinoma. Subsequently, activating germ line point mutations of RET were identified as being responsible for the hereditary medullary thyroid carcinoma syndromes MEN2A, MEN2B and FMTC. RET rearrangements have recently been identified in a small fraction of lung adenocarcinomas.

Area covered: The authors review the current field concerning the RET gene and protein, its involvement in cancer and the preclinical and clinical studies which highlight its role as a potentially important therapeutic target for several cancers.

Expert opinion: Many multitargeted inhibitors which crossreact with RET have been developed and investigated in clinical trials targeting many cancer indications. In particular, VEGFR/PDGFR inhibitors, widely explored as antiangiogenics, have been intensively studied in thyroid carcinoma patients. Notwithstanding the efficacy observed with such agents, their common clinical activity in thyroid carcinoma is of short duration and includes frequent and severe side effects, limiting their therapeutic action. These findings are discussed and the need for improved, more specific RET-targeting drugs is highlighted.     

PCI-32765: a novel Bruton's tyrosine kinase inhibitor for the treatment of lymphoid malignancies

Introduction: There has been a significant paradigm shift in the manner in which lymphoid malignancies are treated and managed. Treatment has been moving away from conventional chemotherapy and towards targeted therapy. The success of new classes of agents such as monoclonal antibodies, proteasome inhibitors and immunomodulatory derivatives has sparked further searches for novel pathways to inhibit. The Bruton's tyrosine kinase (Btk) pathway is a downstream mediator of the B-cell receptor (BCR) pathway, which is crucial in B-cell production and maintenance, and a potential therapeutic target.

Areas covered: This review will summarize the current knowledge of the Btk pathway and its role in lymphoid malignancies. It will also discuss the present data about PCI-32765 in both the preclinical and clinical setting.

Expert opinion: PCI-32765 is an oral irreversible Btk inhibitor with high potency and both preclinical and clinical activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin's lymphoma (NHL). Phase I studies have demonstrated that it is well tolerated and has an excellent safety profile. Further studies are ongoing as a single agent and in combination with other targeted and conventional therapies. PCI-32765 is a very promising targeted therapy, and the data from these trials will ultimately decide its future role and success.