The microtubule-targeted agent lisavanbulin (BAL101553) shows anti-tumor activity in lymphoma models.

Microtubules are major components of the cellular cytoskeleton, ubiquitously founded in all eukaryotic cells. They are involved in mitosis, cell motility, intracellular protein and organelle transport, and maintenance of cytoskeletal shape. Avanbulin (BAL27862) is a microtubule-targeted agent (MTA) that promotes tumor cell death by destabilization of microtubules. Due to its unique binding to the colchicine site of tubulin, differently from other MTAs, avanbulin has previously shown activity in solid tumor cell lines. Its prodrug, lisavanbulin (BAL101553), has shown early signs of clinical activity, especially in tumors with high EB1 expression. Here, we assessed the preclinical anti-tumor activity of avanbulin in diffuse large B cell lymphoma (DLBCL) and the pattern of expression of EB1 in DLBCL cell lines and clinical specimens. Avanbulin showed a potent in vitro anti-lymphoma activity, which was mainly cytotoxic with potent and rapid apoptosis induction. Median IC50 was around 10 nM in both ABC and GCB-DLBCL. Half of the cell lines tested showed an induction of apoptosis already in the first 24 h of treatment, the other half in the first 48 h. EB1 showed expression in DLBCL clinical specimens, opening the possibility for a cohort of patients that could potentially benefit from treatment with lisavanbulin. These data show the basis for further preclinical and clinical evaluation of lisavanbulin in the lymphoma field.

Safety and anti-tumor activity of lisavanbulin administered as 48-hour infusion in patients with ovarian cancer or recurrent glioblastoma: a phase 2a study.

PURPOSE: Lisavanbulin (BAL101553) is the prodrug of avanbulin (BAL27862), a microtubule-destabilizing agent. The goal of this study (NCT02895360) was to characterize the safety, tolerability and antitumor activity of lisavanbulin administered as a 48-hour intravenous (IV) infusion at the recommended Phase 2 dose (RP2D) of 70 mg/m2. Results from the Phase 1 dose-escalation portion of the study identifying the RP2D have been previously reported. Here, we present the findings from the Phase 2a portion of this study. Methods. This multi-center, open-label study included patients with ovarian, fallopian-tube, or primary peritoneal cancer that was either platinum-resistant or refractory (11 patients), or with first recurrence of glioblastoma (12 patients). Lisavanbulin was administered as a 48-hour IV infusion on Days 1, 8, and 15 of a 28-day cycle. Results. Lisavanbulin was well tolerated in both patient cohorts. Thirteen patients (56.5%) developed 49 adverse events assessed as related to study treatment. The majority were mild or moderate; four were grade 3/4. Sixteen SAEs were reported in nine patients (39.1%), with none considered related to study treatment. No AEs led to permanent treatment discontinuation. Three patients in the ovarian cancer cohort had stable disease with lesion size reductions after two cycles of treatment; in the glioblastoma cohort, one patient showed partial response with a > 90% glioblastoma area reduction as best response, and one patient had stable disease after eight cycles of treatment. Conclusion. This study demonstrated a favorable safety and tolerability profile of 48-hour continuous IV infusion of lisavanbulin in patients with solid extracranial tumors or glioblastoma. Clinicaltrials.gov registration: NCT02895360.

The fibroblast growth factor receptor inhibitor, derazantinib, has strong efficacy in human gastric tumor models and synergizes with paclitaxel in vivo.

Derazantinib (DZB) is an inhibitor of fibroblast growth factor receptors 1-3 (FGFR1-3), with additional activity against colony-stimulating-factor-1 receptor (CSF1R). We have profiled the activity of DZB in gastric cancer (GC) as monotherapy and combined with paclitaxel, and explored means of stratifying patients for treatment. The antiproliferative potency of DZB in vitro was quantified in 90 tumor cell lines and shown to correlate significantly with FGFR expression (<0.01) but not with FGFR DNA copy-number (CN) or FGFR mutations. In four GC cell lines in vitro , little or no synergy was observed with paclitaxel. In athymic nude mice, bearing cell-line derived xenografts (CDX) or patient-derived xenograft (PDX) GC models, DZB efficacy correlated highly significantly with FGFR gene expression ( r2 = 0.58; P = 0.0003; n = 18), but not FGFR mutations or DNA-CN. In FGFR-driven GC models, DZB had comparable efficacy to three other FGFR inhibitors and was more efficacious than paclitaxel. DZB had dose-dependent plasma pharmacokinetics but showed low brain penetration at all doses. GC models (one CDX and six PDX) were tested for sensitivity to the combination of DZB and paclitaxel and characterized by immunohistochemistry. The combination showed synergy (5) or additivity (2), and no antagonism, with synergy significantly associated ( P < 0.05) with higher levels of M2-type macrophages. The association of strong efficacy of the combination in vivo with M2 macrophages, which are known to express CSF1R, and the absence of synergy in vitro is consistent with the tumor microenvironment also being a factor in DZB efficacy and suggests additional means by which DZB could be stratified for cancer treatment in the clinic.

Derazantinib, a fibroblast growth factor receptor inhibitor, inhibits colony-stimulating factor receptor-1 in macrophages and tumor cells and in combination with a murine programmed cell death ligand-1-antibody activates the immune environment of murine syngeneic tumor models.

Derazantinib (DZB) is an inhibitor of the fibroblast growth factor receptors 1-3 (FGFRi) with similar potency against colony-stimulating factor receptor-1 (CSF1R), a protein important in the recruitment and function of tumor-associated macrophages. DZB inhibited pCSF1R in the macrophage cell line RAW264.7, and tumor cells GDM-1 and DEL, and had the same potency in HeLa cells transiently over-expressing FGFR2. DZB exhibited similar potency against pCSF1R expressed by isolated murine macrophages, but as in the cell lines, specific FGFRi were without significant CSF1R activity. DZB inhibited growth of three tumor xenograft models with reported expression or amplification of CSF1R, whereas the specific FGFRi, pemigatinib, had no efficacy. In the FGFR-driven syngeneic breast tumor-model, 4T1, DZB was highly efficacious causing tumor stasis. A murine PD-L1 antibody was without efficacy in this model, but combined with DZB, increased efficacy against the primary tumor and further reduced liver, spine and lung metastases. Immunohistochemistry of primary 4T1 tumors showed that the combination favored an antitumor immune infiltrate by strongly increasing cytotoxic T, natural killer and T-helper cells. Similar modulation of the tumor microenvironment was observed in an FGFR-insensitive syngeneic bladder model, MBT-2. These data confirm CSF1R as an important oncology target for DZB and provide mechanistic insight for the ongoing clinical trials, in which DZB is combined with the PD-L1 antibody, atezolizumab.

Preclinical modeling in glioblastoma patient-derived xenograft (GBM PDX) xenografts to guide clinical development of lisavanbulin-a novel tumor checkpoint controller targeting microtubules.

BACKGROUND: Glioblastoma (GBM) is an incurable disease with few approved therapeutic interventions. Radiation therapy (RT) and temozolomide (TMZ) remain the standards of care. The efficacy and optimal deployment schedule of the orally bioavailable small-molecule tumor checkpoint controller lisavanbulin alone, and in combination with, standards of care were assessed using a panel of IDH-wildtype GBM patient-derived xenografts. METHODS: Mice bearing intracranial tumors received lisavanbulin +/-RT +/-TMZ and followed for survival. Lisavanbulin concentrations in plasma and brain were determined by liquid chromatography with tandem mass spectrometry, while flow cytometry was used for cell cycle analysis. RESULTS: Lisavanbulin monotherapy showed significant benefit (P < .01) in 9 of 14 PDXs tested (median survival extension 9%-84%) and brain-to-plasma ratios of 1.3 and 1.6 at 2- and 6-hours postdose, respectively, validating previous data suggesting significant exposure in the brain. Prolonged lisavanbulin dosing from RT start until moribund was required for maximal benefit (GBM6: median survival lisavanbulin/RT 90 vs. RT alone 69 days, P = .0001; GBM150: lisavanbulin/RT 143 days vs. RT alone 73 days, P = .06). Similar observations were seen with RT/TMZ combinations (GBM39: RT/TMZ/lisavanbulin 502 days vs. RT/TMZ 249 days, P = .0001; GBM26: RT/TMZ/lisavanbulin 172 days vs. RT/TMZ 121 days, P = .04). Immunohistochemical analyses showed a significant increase in phospho-histone H3 with lisavanbulin treatment (P = .01). CONCLUSIONS: Lisavanbulin demonstrated excellent brain penetration, significant extension of survival alone or in RT or RT/TMZ combinations, and was associated with mitotic arrest. These data provide a strong clinical rationale for testing lisavanbulin in combination with RT or RT/TMZ in GBM patients.

Derazantinib: an investigational drug for the treatment of cholangiocarcinoma.

INTRODUCTION: This review evaluates the clinical role of fibroblast growth factor receptor 2 (FGFR2) inhibition with derazantinib in patients with intrahepatic cholangiocarcinoma (iCCA) harboring actionable oncogenic FGFR2 fusions/rearrangements, mutations and amplifications. FGFR inhibitors such as derazantinib are currently being evaluated to address the unmet medical need of patients with previously treated, locally advanced or metastatic iCCA harboring such genetic aberrations. AREAS COVERED: We summarize the pharmacokinetics, and the emerging safety and efficacy data of the investigational FGFR inhibitor derazantinib. We discuss the future directions of this novel therapeutic agent for iCCA. EXPERT OPINION: Derazantinib is a potent FGFR1‒3 kinase inhibitor which also has activity against colony stimulating factor-1‒receptor (CSF1R) and vascular endothelial growfth factor receptor‒2 (VEGFR2), suggesting a potentially differentiated role in the treatment of patients with iCCA. Derazantinib has shown clinically meaningful efficacy with durable objective responses, supporting the therapeutic potential of derazantinib in previously treated patients with iCCA harboring FGFR2 fusions/rearrangements, mutations and amplifications. The clinical safety profile of derazantinib was well manageable and compared favorably to the FGFR inhibitor class, particularly with a low incidence of drug-related hand-foot syndrome, stomatitis, retinal and nail toxicity. These findings support the need for increased molecular profiling of cholangiocarcinoma patients.

Treating ICB-resistant glioma with anti-CD40 and mitotic spindle checkpoint controller BAL101553 (lisavanbulin).

Glioblastoma is a highly malignant brain tumor with no curative treatment options, and immune checkpoint blockade has not yet shown major impact. We hypothesized that drugs targeting mitosis might affect the tumor microenvironment and sensitize cancer cells to immunotherapy. We used 2 glioblastoma mouse models with different immunogenicity profiles, GL261 and SB28, to test the efficacy of antineoplastic and immunotherapy combinations. The spindle assembly checkpoint activator BAL101553 (lisavanbulin), agonistic anti-CD40 antibody, and double immune checkpoint blockade (anti-programmed cell death 1 and anti-cytotoxic T lymphocyte-associated protein 4; anti-PD-1 and anti-CTLA-4) were evaluated individually or in combination for treating orthotopic GL261 and SB28 tumors. Genomic and immunological analyses were used to predict and interpret therapy responsiveness. BAL101553 monotherapy increased survival in immune checkpoint blockade-resistant SB28 glioblastoma tumors and synergized with anti-CD40 antibody, in a T cell-independent manner. In contrast, the more immunogenic and highly mutated GL261 model responded best to anti-PD-1 and anti-CTLA-4 therapy and more modestly to BAL101553 and anti-CD40 combination. Our results show that BAL101553 is a promising therapeutic agent for glioblastoma and could synergize with innate immune stimulation. Overall, these data strongly support immune profiling of glioblastoma patients and preclinical testing of combination therapies with appropriate models for particular patient groups.

Phase 1/2a trial of intravenous BAL101553, a novel controller of the spindle assembly checkpoint, in advanced solid tumours.

BACKGROUND: BAL101553 (lisavanbulin), the lysine prodrug of BAL27862 (avanbulin), exhibits broad anti-proliferative activity in human cancer models refractory to clinically relevant microtubule-targeting agents. METHODS: This two-part, open-label, phase 1/2a study aimed to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of 2-h infusion of BAL101553 in adults with advanced or recurrent solid tumours. The MTD was determined using a modified accelerated titration design in phase I. Patients received BAL101553 at the MTD and at lower doses in the phase 2a expansion to characterise safety and efficacy and to determine the recommended phase 2 dose (RP2D). RESULTS: Seventy-three patients received BAL101553 at doses of 15-80 mg/m2 (phase 1, n = 24; phase 2a, n = 49). The MTD was 60 mg/m2; DLTs observed at doses ≥60 mg/m2 were reversible Grade 2-3 gait disturbance with Grade 2 peripheral sensory neuropathy. In phase 2a, asymptomatic myocardial injury was observed at doses ≥45 mg/m2. The RP2D for 2-h intravenous infusion was 30 mg/m2. The overall disease control rate was 26.3% in the efficacy population. CONCLUSIONS: The RP2D for 2-h infusion of BAL101553 was well tolerated. Dose-limiting neurological and myocardial side effects were consistent with the agent's vascular-disrupting properties. CLINICAL TRIAL REGISTRATION: EudraCT: 2010-024237-23.

Young adult outcomes of childhood prophylaxis for severe hemophilia A: results of the Joint Outcome Continuation Study.

The Joint Outcome Study (JOS), a randomized controlled trial, demonstrated that children with severe hemophilia A (HA) initiating prophylactic factor VIII (FVIII) prior to age 2.5 years had reduced joint damage at age 6 years compared with those treated with episodic FVIII for bleeding. The Joint Outcome Continuation Study (JOS-C) evaluated early vs delayed prophylaxis effects on long-term joint health, following JOS participants to age 18 years in an observational, partially retrospective study. Index joint magnetic resonance imaging (MRI) scores of osteochondral (OC) damage (primary outcome), joint physical examination scores, and annualized rates of joint/other bleeding episodes (secondary outcomes) were collected. Thirty-seven of 65 JOS participants enrolled in JOS-C, including 15 randomized to prophylaxis at mean age 1.3 years ("early prophylaxis"); 18 initially randomized to episodic treatment, starting "delayed prophylaxis" at mean age 7.5 years; and 4 with high-titer inhibitors. At JOS-C exit, MRI OC damage was found in 77% of those on delayed and 35% of those on early prophylaxis for an odds ratio of OC damage, in the delayed vs early prophylaxis group, of 6.3 (95% confidence interval, 1.3, 29.9; P = .02). Annualized bleeding rates were higher with delayed prophylaxis (mean plus or minus standard deviation, 10.6 ± 6.6 vs 3.5 ± 2.1; P < .001), including when only comparing time periods on prophylaxis (6.2 ± 5.3 vs 3.3 ± 1.9; P < .05). In severe HA, early initiation of prophylaxis provided continued protection against joint damage throughout childhood compared with delayed initiation, but early prophylaxis was not sufficient to fully prevent damage. This trial was registered at www.clinicaltrials.gov as #NCT01000844.

EB1-dependent long survival of glioblastoma-grafted mice with the oral tubulin-binder BAL101553 is associated with inhibition of tumor angiogenesis.

Glioblastoma (GBM) are aggressive brain tumors with limited treatment options. Cancer stem-like cells (CSLCs) contribute to GBM invasiveness, representing promising targets. BAL101553, a prodrug of BAL27862, is a novel small molecule tubulin-binding agent, promoting tumor cell death through spindle assembly checkpoint activation, which is currently in Phase 1/2a in advanced solid tumor patients including GBM. This study aimed to evaluate long-term daily oral BAL101553 treatment of mice orthotopically grafted with GBM CSLCs (GBM6) according to EB1 expression-level, and to decipher its mechanism of action on GBM stem cells. Oral treatment with BAL101553 for 100 days provoked a large EB1 expression level-dependent survival benefit, together with a decrease in tumor growth and brain invasion. Formation of vascular structures by the fluorescent GBM6-GFP-sh0 cells, mimicking endothelial vascular networks, was observed in the brains of control grafted mice. Following BAL101553 treatment, vessels were no longer detectable, suggesting inhibition of the endothelial trans-differentiation of GBM stem cells. In vitro, BAL27862 treatment resulted in a switch to the endothelial-like phenotype of GBM6 towards an astrocytic phenotype. Moreover, the drug inhibited secretion of VEGF, thus preventing normal endothelial cell migration activated by CSLCs. The decrease in VEGF secretion was confirmed in a human GBM explant following drug treatment. Altogether, our data first confirm the potential of EB1 expression as a response-predictive biomarker of BAL101553 in GBM we previously published and add new insights in BAL101553 long-term action by counteracting CSLCs mediated tumor angiogenesis. Our results strongly support BAL101553 clinical studies in GBM patients.

A Phase 1 study of BAL101553, a novel tumor checkpoint controller targeting microtubules, administered as 48-h infusion in adult patients with advanced solid tumors.

Purpose BAL101553, the prodrug of the microtubule-destabilizer BAL27862, previously showed signs of antitumor activity when administered as a 2-h infusion, but its use was limited by vascular toxicity. We investigated an alternative dosing strategy aimed at improving the safety profile of BAL101553. Methods This multicenter, open-label, Phase 1 dose-escalation study used a 3 + 3 design to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetics, and antitumor activity of BAL101553 administered as a 48-h IV infusion on Days 1, 8, and 15 of a 28-day cycle. Patients received oral BAL101553 on Days 15-21 of cycle 2 to assess oral bioavailability. Results BAL101553 was well tolerated at doses up to ≤70 mg/m2. Three grade 3 DLTs occurred: hypotension (70 mg/m2), hyponatremia and neutropenia (both 90 mg/m2). The MTD for 48-h IV BAL101553 was 70 mg/m2. At this dose level, the AUC for BAL27862 was 8580 ng.h/mL and the Cmax was 144 ng/mL. No apparent dose-related effects on blood pressure were observed with 48-h BAL101553 IV infusion. BAL27862 oral bioavailability was >80%. Conclusions Continuous 48-h IV BAL101553 infusion achieved higher exposure of the BAL27862 active metabolite than a 2-h infusion at the RP2D and did not cause vascular toxicity. Clinicaltrials.gov registration: NCT02895360.

Dual Inhibition of the Lactate Transporters MCT1 and MCT4 Is Synthetic Lethal with Metformin due to NAD+ Depletion in Cancer Cells.

Highly glycolytic cancer cells prevent intracellular acidification by excreting the glycolytic end-products lactate and H+ via the monocarboxylate transporters 1 (MCT1) and 4 (MCT4). We report that syrosingopine, an anti-hypertensive drug, is a dual MCT1 and MCT4 inhibitor (with 60-fold higher potency on MCT4) that prevents lactate and H+ efflux. Syrosingopine elicits synthetic lethality with metformin, an inhibitor of mitochondrial NADH dehydrogenase. NAD+, required for the ATP-generating steps of glycolysis, is regenerated from NADH by mitochondrial NADH dehydrogenase or lactate dehydrogenase. Syrosingopine treatment leads to high intracellular lactate levels and thereby end-product inhibition of lactate dehydrogenase. The loss of NAD+ regeneration capacity due to combined metformin and syrosingopine treatment results in glycolytic blockade, leading to ATP depletion and cell death. Accordingly, ATP levels can be partly restored by exogenously provided NAD+, the NAD precursor nicotinamide mononucleotide (NMN), or vitamin K2. Thus, pharmacological inhibition of MCT1 and MCT4 combined with metformin treatment is a potential cancer therapy.

Detection of circulating tumour cell clusters in human glioblastoma.

Human glioblastoma (GBM) is a highly aggressive, invasive and hypervascularised malignant brain cancer. Individual circulating tumour cells (CTCs) are sporadically found in GBM patients, yet it is unclear whether multicellular CTC clusters are generated in this disease and whether they can bypass the physical hurdle of the blood-brain barrier.  Here, we assessed CTC presence and composition at multiple time points in 13 patients with progressing GBM during an open-label phase 1/2a study with the microtubule inhibitor BAL101553. We observe CTC clusters ranging from 2 to 23 cells and present at multiple sampling time points in a GBM patient with pleomorphism and extensive necrosis, throughout disease progression. Exome sequencing of GBM CTC clusters highlights variants in 58 cancer-associated genes including ATM, PMS2, POLE, APC, XPO1, TFRC, JAK2, ERBB4 and ALK. Together, our findings represent the first evidence of the presence of CTC clusters in GBM.

The novel microtubule targeting agent BAL101553 in combination with radiotherapy in treatment-refractory tumor models.

BACKGROUND AND PURPOSE: Resistance to microtubule targeting agents (MTA) represents a major drawback in successful cancer therapy with MTAs. Here we investigated the combined treatment modality of the novel MTA BAL101553 in combination with radiotherapy in paclitaxel and epothilone-resistant tumor models. MATERIAL AND METHODS: Multiple regimens of BAL101553, or its active moiety BAL27862 for in vitro experiments, were probed in combination with radiotherapy in P-glycoprotein-overexpressing, human colon adenocarcinoma cells (SW480) and in tubulin-mutated human NSCLC cells (A549EpoB40) and tumors thereof. RESULTS: BAL27862 reduced the proliferative activity of SW480 and A549EpoB40 tumor cells with similar potency as in A549 wildtype cells. Combined treatment of BAL27862 with ionizing radiation in vitro resulted in an additive reduction of clonogenicity. Moreover, treatment of paclitaxel- and epothilone-resistant tumors with fractionated irradiation and different regimens of BAL101553 (a single i.v. bolus vs. oral daily) suppressed tumor growth and resulted in an extended additive tumor growth delay with strong reduction of tumor proliferation and mean tumor vessel density. CONCLUSIONS: BAL101553 is a promising alternative in taxane- and epothilone-refractory tumors as part of a combined treatment modality with ionizing radiation. Its potent antitumor effect is not only tumor cell-directed but also targets the tumor microenvironment.

Syrosingopine sensitizes cancer cells to killing by metformin.

We report that the anticancer activity of the widely used diabetic drug metformin is strongly potentiated by syrosingopine. Synthetic lethality elicited by combining the two drugs is synergistic and specific to transformed cells. This effect is unrelated to syrosingopine's known role as an inhibitor of the vesicular monoamine transporters. Syrosingopine binds to the glycolytic enzyme α-enolase in vitro, and the expression of the γ-enolase isoform correlates with nonresponsiveness to the drug combination. Syrosingopine sensitized cancer cells to metformin and its more potent derivative phenformin far below the individual toxic threshold of each compound. Thus, combining syrosingopine and codrugs is a promising therapeutic strategy for clinical application for the treatment of cancer.

The Novel Tubulin-Binding Checkpoint Activator BAL101553 Inhibits EB1-Dependent Migration and Invasion and Promotes Differentiation of Glioblastoma Stem-like Cells.

Glioblastoma patients have limited treatment options. Cancer stem-like cells (CSLC) contribute to glioblastoma invasiveness and repopulation; hence, they represent promising targets for novel therapies. BAL101553 is a prodrug of BAL27862, a novel microtubule-destabilizing agent inhibiting tumor cell proliferation through activation of the spindle assembly checkpoint, which is currently in phase I/II clinical development. Broad anticancer activity has been demonstrated against human cancer models, including tumors refractory to conventional treatments. We have shown that overexpression of microtubule + end-binding 1-protein (EB1) correlates with glioblastoma progression and poor survival. Here, we show that BAL27862 inhibits the growth of two glioblastoma CSLCs. As EB1 is overexpressed in the CSLC line GBM6, which displays a high tumorigenicity and infiltrative pattern of migration in vivo, we investigated drug activity on GBM6 according to EB1 expression. BAL27862 inhibited migration and colony formation at subcytotoxic concentrations in EB1-expressing control cells (GBM6-sh0) but only at cytotoxic concentrations in EB1-downregulated (GBM-shE1) cells. Three administrations of BAL101553 were sufficient to provoke an EB1-dependent survival benefit in tumor-bearing mice. Patterns of invasion and quantification of tumor cells in brain demonstrated that GBM6-sh0 cells were more invasive than GBM6-shEB1 cells, and that the antiproliferative and anti-invasive effects of BAL101553 were more potent in mice bearing control tumors than in EB1-downregulated tumors. This was associated with inhibition of stem cell properties in the GBM6-sh0 model. Finally, BAL27862 triggered astrocytic differentiation of GBM6 in an EB1-dependent manner. These results support the potential of BAL101553 for glioblastoma treatment, with EB1 expression as a predictive biomarker of response. Mol Cancer Ther; 15(11); 2740-9. ©2016 AACR.

The novel microtubule-destabilizing drug BAL27862 binds to the colchicine site of tubulin with distinct effects on microtubule organization.

Microtubule-targeting agents are widely used for the treatment of cancer and as tool compounds to study the microtubule cytoskeleton. BAL27862 is a novel microtubule-destabilizing drug that is currently undergoing phase I clinical evaluation as the prodrug BAL101553. The drug is a potent inhibitor of tumor cell growth and shows a promising activity profile in a panel of human cancer models resistant to clinically relevant microtubule-targeting agents. Here, we evaluated the molecular mechanism of the tubulin-BAL27862 interaction using a combination of cell biology, biochemistry and structural biology methods. Tubulin-binding assays revealed that BAL27862 potently inhibited tubulin assembly at 37 °C with an IC50 of 1.4 µM and bound to unassembled tubulin with a stoichiometry of 1 mol/mol tubulin and a dissociation constant of 244±30 nM. BAL27862 bound to tubulin independently of vinblastine, without the formation of tubulin oligomers. The kinetics of BAL27862 binding to tubulin were distinct from those of colchicine, with evidence of competition between BAL27862 and colchicine for binding. Determination of the tubulin-BAL27862 structure by X-ray crystallography demonstrated that BAL27862 binds to the same site as colchicine at the intradimer interface. Comparison of crystal structures of tubulin-BAL27862 and tubulin-colchicine complexes shows that the binding mode of BAL27862 to tubulin is similar to that of colchicine. However, comparative analyses of the effects of BAL27862 and colchicine on the microtubule mitotic spindle and in tubulin protease-protection experiments suggest different outcomes of tubulin binding. Taken together, our data define BAL27862 as a potent, colchicine site-binding, microtubule-destabilizing agent with distinct effects on microtubule organization.

The effect of secondary prophylaxis versus episodic treatment on the range of motion of target joints in patients with haemophilia.

This study prospectively compared the effect of secondary prophylaxis to episodic treatment on target joint (TJ) range of motion (ROM), number of joint haemorrhages and new TJ development in patients with moderate or severe haemophilia. Two-hundred and eighty-six males, 17% in prophylaxis, 83% in episodic treatment group, participating in the Centers for Disease Control and Prevention's Universal Data Collection project, fulfilled inclusion criteria: age >2 years at enrollment, free of TJs at enrollment, developed at least one TJ after enrollment, and received either prophylaxis or episodic treatment continuously for two follow-up visits after TJ development. The outcomes of interest - percentage change in TJ ROM, number of joint haemorrhages and new TJ development, were modelled using multivariate linear, Poisson and logistic regression techniques respectively. Individuals who received secondary prophylaxis in comparison to episodic treatment were younger at TJ development (P < 0.01); there was no difference in the decrease in TJ ROM between the two groups (P = 0.9). Factors significantly associated with a higher rate of haemarthroses included episodic treatment, severe haemophilia, age >5 years at TJ development, obesity and inhibitor negative status. Secondary prophylaxis significantly decreased haemarthroses but was not associated with a significant improvement in TJ ROM or with new TJ development.

Effectiveness and molecular interactions of the clinically active mTORC1 inhibitor everolimus in combination with tamoxifen or letrozole in vitro and in vivo.

INTRODUCTION: Strategies to improve the efficacy of endocrine agents in breast cancer (BC) therapy and to delay the onset of resistance include concomitant targeting of the estrogen receptor alpha (ER) and the mammalian target of rapamycin complex 1 (mTORC1), which regulate cell-cycle progression and are supported by recent clinical results. METHODS: BC cell lines expressing aromatase (AROM) and modeling endocrine-sensitive (MCF7-AROM1) and human epidermal growth factor receptor 2 (HER2)-dependent de novo resistant disease (BT474-AROM3) and long-term estrogen-deprived (LTED) MCF7 cells that had acquired resistance associated with HER2 overexpression were treated in vitro and as subcutaneous xenografts with everolimus (RAD001-mTORC1 inhibitor), in combination with tamoxifen or letrozole. End points included proliferation, cell-cycle arrest, cell signaling, and effects on ER-mediated transactivation. RESULTS: Everolimus caused a concentration-dependent decrease in proliferation in all cell lines, which was associated with reductions in S6 phosphorylation. Everolimus plus letrozole or tamoxifen enhanced the antiproliferative effect and G1-accumulation compared with monotherapy, as well as increased phosphorylation (Ser10) and nuclear accumulation of p27 and pronounced dephosphorylation of Rb. Sensitivity was greatest to everolimus in the LTED cells but was reduced by added estrogen. Increased pAKT occurred in all circumstances with everolimus and, in the BT474 and LTED cells, was associated with increased pHER3. Decreased ER transactivation suggested that the effectiveness of everolimus might be partly related to interrupting cross-talk between growth-factor signaling and ER. In MCF7-AROM1 xenografts, letrozole plus everolimus showed a trend toward enhanced tumor regression, versus the single agents. In BT474-AROM3 xenografts, everolimus alone was equally effective at reducing tumor volume as were the combination therapies. CONCLUSIONS: The results provide mechanistic support for recent positive clinical data on the combination of everolimus and endocrine therapy, as well as data on potential routes of escape via enhanced HER2/3 signaling. This merits investigation for further improvements in treatment efficacy.

Persistence of functional antibodies to group B streptococcal capsular polysaccharides following immunization with glycoconjugate vaccines.

The duration of functional activity of group B streptococcal (GBS) glycoconjugate vaccine-induced capsular polysaccharide-specific (CPS) IgG was evaluated among healthy adult responders. Opsonophagocytic activity declined significantly from a 4-week post-immunization peak, but substantial functional activity, exceeding 1 log(10) reduction in GBS cfu/mL, was retained at 18 months to 2 years post-immunization for each GBS type assessed. The persistence of functional antibody activity when GBS CPS-specific IgG concentrations decline, although remaining significantly higher than pre-immunization levels, suggests that long-term protection may be expected from candidate GBS glycoconjugates administered to this population.