miR-29 modulates CD40 signaling in chronic lymphocytic leukemia by targeting TRAF4: an axis affected by BCR inhibitors.

B-cell receptor (BCR) signaling and T-cell interactions play a pivotal role in chronic lymphocytic leukemia (CLL) pathogenesis and disease aggressiveness. CLL cells can use microRNAs (miRNAs) and their targets to modulate microenvironmental interactions in the lymph node niches. To identify miRNA expression changes in the CLL microenvironment, we performed complex profiling of short noncoding RNAs in this context by comparing CXCR4/CD5 intraclonal cell subpopulations (CXCR4dimCD5bright vs CXCR4brightCD5dim cells). This identified dozens of differentially expressed miRNAs, including several that have previously been shown to modulate BCR signaling (miR-155, miR-150, and miR-22) but also other candidates for a role in microenvironmental interactions. Notably, all 3 miR-29 family members (miR-29a, miR-29b, miR-29c) were consistently down-modulated in the immune niches, and lower miR-29(a/b/c) levels associated with an increased relative responsiveness of CLL cells to BCR ligation and significantly shorter overall survival of CLL patients. We identified tumor necrosis factor receptor-associated factor 4 (TRAF4) as a novel direct target of miR-29s and revealed that higher TRAF4 levels increase CLL responsiveness to CD40 activation and downstream nuclear factor-κB (NF-κB) signaling. In CLL, BCR represses miR-29 expression via MYC, allowing for concurrent TRAF4 upregulation and stronger CD40-NF-κB signaling. This regulatory loop is disrupted by BCR inhibitors (bruton tyrosine kinase [BTK] inhibitor ibrutinib or phosphatidylinositol 3-kinase [PI3K] inhibitor idelalisib). In summary, we showed for the first time that a miRNA-dependent mechanism acts to activate CD40 signaling/T-cell interactions in a CLL microenvironment and described a novel miR-29-TRAF4-CD40 signaling axis modulated by BCR activity.

Efficacy of high-dose corticosteroid-based treatment for chronic lymphocytic leukemia patients with p53 abnormalities in the era of B-cell receptor inhibitors.

PURPOSE: High-dose methylprednisolone (HDMP) with or without anti-CD20 antibody treatment in the pre B-cell receptor inhibitor (BCRi) era was used as potential salvage therapy for relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma (r/r CLL/SLL) patients bearing the 17p deletion. PATIENTS AND METHODS: Outcomes were compared in retrospect between r/r patients treated with HDMP (n = 20), ibrutinib (n = 39) and idelalisib with rituximab (n = 14). RESULTS: Higher overall response rates were found in those patients undergoing BCRi therapy compared to HDMP (79.2% vs. 0%; p < 0.0001), along with longer median progression-free survival (not reached vs. 24.1 months; p < 0.01). Nevertheless, there were no differences in the overall survival (HDMP 35.87 months vs. not reached; p = 0.58). CONCLUSION: HDMP treatment was significantly inferior in terms of response rate and progression-free survival in r/r CLL/SLL patients with the 17p deletion, and may only be used whenever novel compounds are unavailable.

CRISPR/Cas9-generated models uncover therapeutic vulnerabilities of del(11q) CLL cells to dual BCR and PARP inhibition.

The deletion of 11q (del(11q)) invariably comprises ATM gene in chronic lymphocytic leukemia (CLL). Concomitant mutations in this gene in the remaining allele have been identified in 1/3 of CLL cases harboring del(11q), being the biallelic loss of ATM associated with adverse prognosis. Although the introduction of targeted BCR inhibition has significantly favored the outcomes of del(11q) patients, responses of patients harboring ATM functional loss through biallelic inactivation are unexplored, and the development of resistances to targeted therapies have been increasingly reported, urging the need to explore novel therapeutic approaches. Here, we generated isogenic CLL cell lines harboring del(11q) and ATM mutations through CRISPR/Cas9-based gene-editing. With these models, we uncovered a novel therapeutic vulnerability of del(11q)/ATM-mutated cells to dual BCR and PARP inhibition. Ex vivo studies in the presence of stromal stimulation on 38 CLL primary samples confirmed a synergistic action of the combination of olaparib and ibrutinib in del(11q)/ATM-mutated CLL patients. In addition, we showed that ibrutinib produced a homologous recombination repair impairment through RAD51 dysregulation, finding a synergistic link of both drugs in the DNA damage repair pathway. Our data provide a preclinical rationale for the use of this combination in CLL patients with this high-risk cytogenetic abnormality.

Lyn is involved in host defense against S. agalactiae infection and BCR signaling in Nile tilapia (Oreochromis niloticus).

Lyn, a member of Src protein kinase family, plays a crucial role in immune reactions against pathogenic infection. In this study, Lyn from Nile tilapia (Oreochromis niloticus) (OnLyn) was identified and characterized at expression pattern against bacterial infection, and regulation function in BCR signaling. The open reading frame of OnLyn contained 1536 bp of nucleotide sequence encoded a protein of 511 amino acids. The OnLyn protein was highly conversed to other species Lyn, including SH3, SH2 and a catalytic Tyr kinase (TyrKc) domain. Transcriptional expression analysis revealed that OnLyn was detected in all examined tissues and was highly expressed in the head kidney. The up-regulation OnLyn expression was observed in the head kidney and spleen following challenge with Streptococcus agalactiae (S. agalactiae) in vivo, and was also displayed in head kidney leukocytes challenge with S. agalactiae and LPS in vitro. In addition, after induction with mouse anti-OnIgM mAb in vitro, the OnLyn expression and phosphorylation of OnLyn (Y507) were significantly up-regulated in the head kidney leukocytes. Moreover, after treatment with AZD0530 and mouse anti-OnIgM monoclonal antibody, the down-regulation of cytoplasmic free-Ca2+ concentration was detected in the head kidney leukocytes in vitro. Taken together, the findings of this study revealed that OnLyn might play potential roles in BCR signaling and get involved in host defense against bacterial infection in Nile tilapia.

Targeting ROR1 identifies new treatment strategies in hematological cancers.

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a member of the ROR receptor family consisting of two closely related type I transmembrane proteins ROR1 and ROR2. Owing to mutations in their canonical motifs required for proper kinase activity, RORs are classified as pseudokinases lacking detectable catalytic activity. ROR1 stands out for its selective and high expression in numerous blood and solid malignancies compared with a minimal expression in healthy adult tissues, suggesting high potential for this molecule as a drug target for cancer therapy. Current understanding attributes a survival role for ROR1 in cancer cells; however, its oncogenic function is cancer-type-specific and involves various signaling pathways. High interest in ROR1-targeted therapies resulted in the development of ROR1 monoclonal antibodies such as cirmtuzumab, currently in a phase I clinical trial for chronic lymphocytic leukemia. Despite these advances in translational studies, the molecular mechanism employed by ROR1 in different cancers is not yet fully understood; therefore, more insights into the oncogenic role of ROR1 signaling are crucial in order to optimize the use of targeted drugs. Recent studies provided evidence that targeting ROR1 simultaneously with inhibition of B-cell receptor (BCR) signaling is more effective in killing ROR1-positive leukemia cells, suggesting a synergistic correlation between co-targeting ROR1 and BCR pathways. Although this synergy has been previously reported for B-cell acute lymphoblastic leukemia, the molecular mechanism appears rather different. These results provide more insights into ROR1-BCR combinatorial treatment strategies in hematological malignancies, which could benefit in tailoring more effective targeted therapies in other ROR1-positive cancers.

Activity of the novel BCR kinase inhibitor IQS019 in preclinical models of B-cell non-Hodgkin lymphoma.

BACKGROUND: Pharmacological inhibition of B cell receptor (BCR) signaling has recently emerged as an effective approach in a wide range of B lymphoid neoplasms. However, despite promising clinical activity of the first Bruton's kinase (Btk) and spleen tyrosine kinase (Syk) inhibitors, a small fraction of patients tend to develop progressive disease after initial response to these agents. METHODS: We evaluated the antitumor activity of IQS019, a new BCR kinase inhibitor with increased affinity for Btk, Syk, and Lck/Yes novel tyrosine kinase (Lyn), in a set of 34 B lymphoid cell lines and primary cultures, including samples with acquired resistance to the first-in-class Btk inhibitor ibrutinib. Safety and efficacy of the compound were then evaluated in two xenograft mouse models of B cell lymphoma. RESULTS: IQS019 simultaneously engaged a rapid and dose-dependent de-phosphorylation of both constitutive and IgM-activated Syk, Lyn, and Btk, leading to impaired cell proliferation, reduced CXCL12-dependent cell migration, and induction of caspase-dependent apoptosis. Accordingly, B cell lymphoma-bearing mice receiving IQS019 presented a reduced tumor outgrowth characterized by a decreased mitotic index and a lower infiltration of malignant cells in the spleen, in tight correlation with downregulation of phospho-Syk, phospho-Lyn, and phospho-Btk. More interestingly, IQS019 showed improved efficacy in vitro and in vivo when compared to the first-in-class Btk inhibitor ibrutinib, and was active in cells with acquired resistance to this latest. CONCLUSIONS: These results define IQS019 as a potential drug candidate for a variety of B lymphoid neoplasms, including cases with acquired resistance to current BCR-targeting therapies.

The Dual Syk/JAK Inhibitor Cerdulatinib Antagonizes B-cell Receptor and Microenvironmental Signaling in Chronic Lymphocytic Leukemia.

Purpose: B-cell receptor (BCR)-associated kinase inhibitors, such as ibrutinib, have revolutionized the treatment of chronic lymphocytic leukemia (CLL). However, these agents are not curative, and resistance is already emerging in a proportion of patients. IL4, expressed in CLL lymph nodes, can augment BCR signaling and reduce the effectiveness of BCR kinase inhibitors. Therefore, simultaneous targeting of the IL4- and BCR signaling pathways by cerdulatinib, a novel dual Syk/JAK inhibitor currently in clinical trials (NCT01994382), may improve treatment responses in patients.Experimental Design: PBMCs from patients with CLL were treated in vitro with cerdulatinib alone or in combination with venetoclax. Cell death, chemokine, and cell signaling assay were performed and analyzed by flow cytometry, immunoblotting, q-PCR, and ELISA as indicated.Results: At concentrations achievable in patients, cerdulatinib inhibited BCR- and IL4-induced downstream signaling in CLL cells using multiple readouts and prevented anti-IgM- and nurse-like cell (NLC)-mediated CCL3/CCL4 production. Cerdulatinib induced apoptosis of CLL cells, in a time- and concentration-dependent manner, and particularly in IGHV-unmutated samples with greater BCR signaling capacity and response to IL4, or samples expressing higher levels of sIgM, CD49d+, or ZAP70+ Cerdulatinib overcame anti-IgM, IL4/CD40L, or NLC-mediated protection by preventing upregulation of MCL-1 and BCL-XL; however, BCL-2 expression was unaffected. Furthermore, in samples treated with IL4/CD40L, cerdulatinib synergized with venetoclax in vitro to induce greater apoptosis than either drug alone.Conclusions: Cerdulatinib is a promising therapeutic for the treatment of CLL either alone or in combination with venetoclax, with the potential to target critical survival pathways in this currently incurable disease. Clin Cancer Res; 23(9); 2313-24. ©2016 AACR.

Dendrimer-based nanoparticles for potential personalized therapy in chronic lymphocytic leukemia: Targeting the BCR-signaling pathway.

Chronic lymphocytic leukemia (CLL) is one of the most prevalent forms of leukemia in western society. Although classic chemoimmune therapy is still the gold standard of care for leukemic patients, effective therapy of CLL is yet to be achieved. The present study examines the influence of poly(propylene)imine (PPI) dendrimers with primary amino surface groups modified with maltotriose residues in approximately 90% (PPI-G4-DS-Mal-III) or 30% (PPI-G4-OS-Mal-III) of cases on CLL cells (MEC-1 cell line with del(17p)), and confirms that the main trigger in this interaction is the induction of the apoptotic mechanism. The efficacy of each dendrimer was compared using fludarabine (FA). Gene expression profiling (GEP) by microarray identified a group of genes in the BCR signaling pathway characterized by different levels of expression directly associated with the tested agent and type of interaction. Network analysis revealed the potential patterns involved in potential personalized therapy of CLL. The expression of most BCR genes decreased under the influence of dendrimers, which might translate into decreased maturation and proliferation of CLL lymphocytes. Moreover, PPI-G4-OS/DS-Mal-III dendrimers affected gene expression and CLL cells in a different way to FA. Thanks to unique properties, dendrimers may be specifically targeted, thus improving the effectiveness of CLL therapy.

PDZK1 prevents neointima formation via suppression of breakpoint cluster region kinase in vascular smooth muscle.

Scavenger receptor class B, type I (SR-BI) and its adaptor protein PDZK1 mediate responses to HDL cholesterol in endothelium. Whether the receptor-adaptor protein tandem serves functions in other vascular cell types is unknown. The current work determined the roles of SR-BI and PDZK1 in vascular smooth muscle (VSM). To evaluate possible VSM functions of SR-BI and PDZK1 in vivo, neointima formation was assessed 21 days post-ligation in the carotid arteries of wild-type, SR-BI-/- or PDZK1-/- mice. Whereas neointima development was negligible in wild-type and SR-BI-/-, there was marked neointima formation in PDZK1-/- mice. PDZK1 expression was demonstrated in primary mouse VSM cells, and compared to wild-type cells, PDZK1-/- VSM displayed exaggerated proliferation and migration in response to platelet derived growth factor (PDGF). Tandem affinity purification-mass spectrometry revealed that PDZK1 interacts with breakpoint cluster region kinase (Bcr), which contains a C-terminal PDZ binding sequence and is known to enhance responses to PDGF in VSM. PDZK1 interaction with Bcr in VSM was demonstrated by pull-down and by coimmunoprecipitation, and the augmented proliferative response to PDGF in PDZK1-/- VSM was abrogated by Bcr depletion. Furthermore, compared with wild-type Bcr overexpression, the introduction of a Bcr mutant incapable of PDZK1 binding into VSM cells yielded an exaggerated proliferative response to PDGF. Thus, PDZK1 has novel SR-BI-independent function in VSM that affords protection from neointima formation, and this involves PDZK1 suppression of VSM cell proliferation via an inhibitory interaction with Bcr.

Managing high-risk CLL during transition to a new treatment era: stem cell transplantation or novel agents?

Allogeneic hematopoietic stem cell transplantation (HSCT) has been considered as the treatment of choice for patients with high-risk chronic lymphocytic leukemia (HR-CLL; ie, refractory to purine analogs, short response [<24 months] to chemoimmunotherapy, and/or presence of del[17p]/TP53 mutations). Currently, treatment algorithms for HR-CLL are being challenged by the introduction of novel classes of drugs. Among them, BCR signal inhibitors (BCRi) and B-cell lymphoma 2 antagonists (BCL2a) appear particularly promising. As a result of the growing body of favorable outcome data reported for BCRi/BCL2a, uncertainty is emerging on how to advise patients with HR-CLL about indication for and timing of HSCT. This article provides an overview of currently available evidence and theoretical considerations to guide this difficult decision process. Until the risks and benefits of different treatment strategies are settled, all patients with HR-CLL should be considered for treatment with BCRi/BCL2a. For patients who respond to these agents, there are 2 treatment possibilities: (1) performing an HSCT or (2) continuing treatment with the novel drug. Individual disease-specific and transplant-related risk factors, along with patient's preferences, should be taken into account when recommending one of these treatments over the other.

Transcriptional and post-transcriptional regulation of IκB-ζ upon engagement of the BCR, TLRs and FcγR.

IκB-ζ is a nuclear IκB protein robustly induced in macrophages and fibroblasts upon TLR or IL-1R stimulation. IκB-ζ associates with NF-κB in the cell nucleus and is essential for the induction of a subset of secondary response genes represented by IL-6. Here, we analyzed induction of IκB-ζ in mouse B cells and found that IκB-ζ is induced by BCR or TLR stimulation. Similar to TLR stimulation, BCR stimulation elicited NF-κB-mediated transcriptional activation and mRNA stabilization of IκB-ζ via a cis-element in IκB-ζ mRNA. Proteasome inhibitors inhibited transcriptional activation but not post-transcriptional activation, indicating independency of the two signals. Co-stimulation of the BCR and TLR9 or TLR7, but not TLR2/1, synergistically induced IκB-ζ. Co-engagement of inhibitory Fcγ receptor suppressed BCR-mediated IκB-ζ expression but not that induced by TLR stimulation alone or co-stimulation of TLR and the BCR. The PI3K inhibitor LY294002 inhibited BCR-mediated, but not TLR-mediated, induction of IκB-ζ, consistent with the role of PI3K in BCR signaling and its suppression by FcγR. Analysis of IκB-ζ-deficient B cells demonstrated that IκB-ζ was essential upon stimulation of BCR or TLR for the expression of several genes including IL-10 and CTLA4. IκB-ζ-deficient B cells exhibited impaired proliferation and enhanced up-regulation of CD86 following stimulation of TLR9, but not the BCR, indicating critical roles for IκB-ζ in TLR signaling in B cells. Strict regulatory mechanisms for the induction of IκB-ζ via multiple pathways and its essential function upon stimulation indicate that IκB-ζ plays an important role in B cells.

Rapid and sensitive allele-specific (AS)-RT-PCR assay for detection of T315I mutation in chronic myeloid leukemia patients treated with tyrosine-kinase inhibitors.

Point mutations in the kinase domain of BCR-ABL were described in 40-90% of patients with chronic myeloid leukemia (CML) resistant to Imatinib. We herein describe the development of a rapid allele-specific (AS)-RT-PCR assay to identify the T315I mutation, which confers full resistance to all available tyrosine-kinase inhibitors (TKI). The mutation status of 65 patients with resistant CML was evaluated, and the T315I was detected in 3/65 (4.6%). Comparisons between sequencing and AS-RT-PCR results, as well as serial dilutions experiments proved that the method is specific and reproducible, with maximum sensitivity of 1 × 10(-3). The developed assay is a convenient and easy tool to be used in research of CML resistance for rapid mutation screening and, together with sequencing, may be included in efficient strategies for early detection of TKI resistance in patients with CML.

A novel chalcone derivative which acts as a microtubule depolymerising agent and an inhibitor of P-gp and BCRP in in-vitro and in-vivo glioblastoma models.

BACKGROUND: Over the past decades, in spite of intensive search, no significant increase in the survival of patients with glioblastoma has been obtained. The role of the blood-brain barrier (BBB) and especially the activity of efflux pumps belonging to the ATP Binding Cassette (ABC) family may, in part, explain this defect. METHODS: The in-vitro activities of JAI-51 on cell proliferation were assessed by various experimental approaches in four human and a murine glioblastoma cell lines. Using drug exclusion assays and flow-cytometry, potential inhibitory effects of JAI-51 on P-gp and BCRP were evaluated in sensitive or resistant cell lines. JAI-51 activity on in-vitro microtubule polymerization was assessed by tubulin polymerization assay and direct binding measurements by analytical ultracentrifugation. Finally, a model of C57BL/6 mice bearing subcutaneous GL26 glioblastoma xenografts was used to assess the activity of the title compound in vivo. An HPLC method was designed to detect JAI-51 in the brain and other target organs of the treated animals, as well as in the tumours. RESULTS: In the four human and the murine glioblastoma cell lines tested, 10 muM JAI-51 inhibited proliferation and blocked cells in the M phase of the cell cycle, via its activity as a microtubule depolymerising agent. This ligand binds to tubulin with an association constant of 2 x 105 M-1, overlapping the colchicine binding site. JAI-51 also inhibited the activity of P-gp and BCRP, without being a substrate of these efflux pumps. These in vitro studies were reinforced by our in vivo investigations of C57BL/6 mice bearing GL26 glioblastoma xenografts, in which JAI-51 induced a delay in tumour onset and a tumour growth inhibition, following intraperitoneal administration of 96 mg/kg once a week. In accordance with these results, JAI-51 was detected by HPLC in the tumours of the treated animals. Moreover, JAI-51 was detected in the brain, showing that the molecule is also able to cross the BBB. CONCLUSION: These in vitro and in vivo data suggest that JAI-51 could be a good candidate for a new treatment of tumours of the CNS. Further investigations are in progress to associate the title compound chemotherapy to radiotherapy in a rat model.

Bcr kinase activation by angiotensin II inhibits peroxisome-proliferator-activated receptor gamma transcriptional activity in vascular smooth muscle cells.

Bcr is a serine/threonine kinase activated by platelet-derived growth factor that is highly expressed in the neointima after vascular injury. Here, we demonstrate that Bcr is an important mediator of angiotensin (Ang) II and platelet-derived growth factor-mediated inflammatory responses in vascular smooth muscle cells (VSMCs). Among transcription factors that might regulate Ang II-mediated inflammatory responses we found that ligand-mediated peroxisome proliferator-activated receptor (PPAR)gamma transcriptional activity was significantly decreased by Ang II. Ang II increased Bcr expression and kinase activity. Overexpression of Bcr significantly inhibited PPARgamma activity. In contrast, knockdown of Bcr using Bcr small interfering RNA and a dominant-negative form of Bcr (DN-Bcr) reversed Ang II-mediated inhibition of PPARgamma activity significantly, suggesting the critical role of Bcr in Ang II-mediated inhibition of PPARgamma activity. Point-mutation and in vitro kinase analyses showed that PPARgamma was phosphorylated by Bcr at serine 82. Overexpression of wild-type Bcr kinase did not inhibit ligand-mediated PPARgamma1 S82A mutant transcriptional activity, indicating that Bcr regulates PPARgamma activity via S82 phosphorylation. DN-Bcr and Bcr small interfering RNA inhibited Ang II-mediated nuclear factor kappaB activation in VSMCs. DN-PPARgamma reversed DN-Bcr-mediated inhibition of nuclear factor kappaB activation, suggesting that PPARgamma is downstream from Bcr. Intimal proliferation in low-flow carotid arteries was decreased in Bcr knockout mice compared with wild-type mice, suggesting the critical role of Bcr kinase in VSMC proliferation in vivo, at least in part, via regulating PPARgamma/nuclear factor kappaB transcriptional activity.

Targeted drugs in chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by the presence of the Philadelphia (Ph) chromosome, which results from a reciprocal translocation between the long arms of the chromosomes 9 and 22 t(9;22)(q34;q11). This translocation creates two new genes, BCR-ABL on the 22q- (Ph chromosome) and the reciprocal ABL-BCR on 9q-. The BCR-ABL gene encodes for a 210-kD protein with deregulated tyrosine kinase (TK) activity, which is crucial for malignant transformation in CML. The recognition of the BCR-ABL gene and corresponding protein led to the synthesis of small-molecule drugs, designed to interfere with BCR-ABL tyrosine kinase activation by competitive binding at the ATP-binding site. The first tyrosine kinase inhibitor (TKI), introduced into clinical practice in 1998, was imatinib mesylate. Imatinib became the first choice drug in chronic phase CML, because of its high efficacy, low toxicity and ability to maintain durable hematological and cytogenetic responses. However, approximately 20-25% of patients initially treated with imatinib will need alternative therapy, due to drug resistance, which is often caused by the appearance of clones expressing mutant forms of BCR-ABL. Second-generation TKIs have provided new therapeutic option for the patients resistant to imatinib. Dasatinib is the first, second-generation TKI, approved in the US and European Union for the treatment of CML patients with imatinib resistance or intolerance. This drug is a dual SRC-ABL kinase inhibitor, active in most clinically relevant BCR-ABL mutations, except highly resistant T315I. Other second-generation TKIs include nilotinib, bosutinib and INNO 406. Apart from TKIs, the promising group of molecules is inhibitors of Aurora family of serine-threonine kinases. One of these molecules, MK0457, has entered clinical trials, and initial reports indicate that this compound could be active in disease associated with T315I mutation. Thus, wide spectrum of new agents, with different mode of action, is currently in clinical development for CML. It is likely that combination therapy will be the best therapeutic strategy in the future.

Preclinical pharmacokinetics and in vitro metabolism of dasatinib (BMS-354825): a potent oral multi-targeted kinase inhibitor against SRC and BCR-ABL.

PURPOSE: Dasatinib (BMS-354825), a potent oral multi-targeted kinase inhibitor against SRC and BCR-ABL, has recently been approved for the treatment of chronic myelogenous leukaemia (CML) in imatinib-acquired resistance and intolerance. In vitro and in vivo studies were conducted to characterize the pharmacokinetics and metabolism of dasatinib in mouse, rat, dog, and monkey. Possible mechanisms contributing to the incomplete oral bioavailability of dasatinib in animals were investigated. METHODS: Metabolic stability of dasatinib was measured after incubation with liver microsomes (either NADPH- or UDPGA-fortified) and isolated hepatocytes obtained from mouse, rat, dog, monkey, and human. In all cases, substrate depletion over time was measured, and appropriate scaling factors were used to predict in vivo clearance. Pharmacokinetics of dasatinib were determined in mice, rats, dogs, and monkeys after administration of single intravenous or oral doses. In addition, the routes of excretion were investigated after administration of dasatinib to bile duct cannulated (BDC) rats. Absorption and first-pass metabolism were evaluated as possible reasons for the incomplete oral bioavailability using various in vitro and in vivo models like Caco-2 cells, P-glycoprotein (P-gp) knockout mice, and intra-portal dosing in rats. RESULTS: In vivo systemic plasma clearance values of dasatinib were 62, 26, 25, and 34 ml/min/kg in mouse, rat, dog, and monkey, respectively. Scaling of in vitro hepatocyte and liver microsomal data gave reasonably good predictions of in vivo clearances across all species. Percent distribution in blood cells ranged from 43% in mouse to 57% in dog. Dasatinib showed high volumes of distribution (>3 l/kg) and high serum protein binding values (>90%) in all four species tested. Oral bioavailability of dasatinib ranged from 14% in the mouse to 34% in the dog. In rats, bioavailability after an intraportal dose was comparable to that after intra-arterial administration. In BDC rats, less than 15% of an intravenous dose was excreted unchanged in urine, bile, and the gastrointestinal tract, suggesting that dasatinib is cleared primarily via metabolism. Dasatinib has high intrinsic permeability in Caco-2 cells, however, the efflux ratio was approximately two-fold indicating that it may be a substrate for an intestinal efflux transporter. However, in vivo studies in P-gp knockout mice versus wild-type mice showed no difference in the amount of dasatinib remaining unabsorbed in the gastrointestinal tract, suggesting that P-gp may not be responsible for the incomplete bioavailability. CONCLUSIONS: Dasatinib shows intermediate clearance in mouse, rat, dog, and monkey, and distributes extensively in those species. Oxidative metabolism appears to be the predominant clearance pathway. The incomplete oral bioavailability may be due to both incomplete absorption and high first-pass metabolism. However, the efflux transporter, P-glycoprotein does not appear to be limiting oral absorption.

Treatment of acute lymphoblastic leukaemia : a new era.

Acute lymphocytic leukaemia (ALL) is a heterogeneous group of disorders that result from the clonal proliferation and expansion of malignant lymphoid cells in the bone marrow, blood and other organs. Distinct clinicopathological ALL entities have been identified, resulting in the adoption of risk-oriented treatment approaches. Advances in ALL therapy have led to long-term survival rates of >80% in children. However, only approximate, approximately 30-40% of adults achieve long-term disease-free survival. Contemporary ALL treatment programmes include induction, intensified consolidation, maintenance phases and CNS prophylaxis. The optimal treatment of Philadelphia chromosome-positive patients requires the addition of BCR-ABL tyrosine kinase inhibitors, such as imatinib, whereas allogeneic stem-cell transplantation remains the preferred approach for high-risk patients in first remission. Since only approximate, approximately 38% of adult ALL patients are free of disease 5 years after diagnosis and the outcome of salvage chemotherapy is very poor (complete remission rates of 20-30%, median survival of 3-6 months), novel agents are desperately required. Of those currently in clinical studies, the outlook for sphingosomal vincristine, pegylated asparaginase (pegaspargase), liposomal annamycin, ABT-751, pemetrexed, talotrexin, nelarabine and the novel BCR-ABL kinase inhibitors is discussed.

Preclinical pharmacology of the novel antitumor agent adaphostin, a tyrphostin analog that inhibits bcr/abl.

PURPOSE: To define several pharmacological properties for the potential anticancer agent, adaphostin, in order to determine whether the compound is appropriate for clinical evaluation as an anticancer agent. METHODS: The analytical procedure involved high-performance liquid chromatography and utilized an analytical J'Sphere ODS H-80 column. RESULTS: The stability of adaphostin at two different concentrations was determined at temperatures of 37 degrees C, 4 degrees C, and -80 degrees C, in the plasma of mice, rats, dogs, and humans. The compound was most stable at the lower temperatures. At all temperatures, adaphostin was generally most stable in human plasma and least stable in dog plasma. Adaphostin bound strongly (>93%) to proteins in plasma from all four species. Following intravenous (i.v.) administration to mice (50 mg/kg; 150 mg/m(2)), plasma concentrations declined rapidly from 50 microM at 2 min to 1 microM at 2 h. Elimination was triexponential, with t (1/2) values of 1.1, 9.1, and 41.2 min. The Cl(tb) was 0.411 L/(min.m(2)), the V (dss) was 24.6 L/m(2), and the AUC was 927 microM.min. In a comparison of vehicles for intraperitoneal (i.p.) dosing, PEG 300 allowed the highest plasma concentrations of adaphostin. Bioavailability following an i.p. dose was greater than that following a subcutaneous dose, or that for a dose administered by oral gavage. For rats dosed i.v. with adaphostin (50 mg/kg; 300 mg/m(2)), plasma concentrations also decreased triexponentially, with t (1/2) values of 1.8, 10.6, and 136 min. Other pharmacokinetic values were Cl(tb) = 0.466 L/(min.m(2)), AUC = 1,161 microM.min, and V (dss)=8.0 L/m(2). Analysis of samples collected from two dogs dosed i.v. with adaphostin (7.5 mg/kg; 150 mg/m(2)) showed that plasma concentrations decreased in a biphasic manner, with individual values for t (1/2alpha) of 6.0 and 9.8 min for the distribution phase and t (1/2beta) of 40.6 and 66.2 min for the elimination phase. Other pharmacokinetic values were Cl(tb) = 0.565 and 0.852 L/(min.m(2)), AUC = 673 and 446 microM min, and V (dss) = 29.6 and 56.8 L/m(2). CONCLUSIONS: The stability of adaphostin in plasma varies with species. In mice and dogs dosed with adaphostin, plasma concentrations of the compound decreased rapidly. The clearance of adaphostin from plasma, on an m(2) basis, was equivalent for mice and rats but more rapid in dogs. These results are relevant for assessing the pharmacologic and toxicologic profiles and the antitumor activity of adaphostin in humans.