Venetoclax plus rituximab in relapsed or refractory chronic lymphocytic leukaemia: a phase 1b study.

BACKGROUND: Selective BCL2 inhibition with venetoclax has substantial activity in patients with relapsed or refractory chronic lymphocytic leukaemia. Combination therapy with rituximab enhanced activity in preclinical models. The aim of this study was to assess the safety, pharmacokinetics, and activity of venetoclax in combination with rituximab. METHODS: Adult patients with relapsed or refractory chronic lymphocytic leukaemia (according to the 2008 Modified International Workshop on CLL guidelines) or small lymphocytic lymphoma were eligible for this phase 1b, dose-escalation trial. The primary outcomes were to assess the safety profile, to determine the maximum tolerated dose, and to establish the recommended phase 2 dose of venetoclax when given in combination with rituximab. Secondary outcomes were to assess the pharmacokinetic profile and analyse efficacy, including overall response, duration of response, and time to tumour progression. Minimal residual disease was a protocol-specified exploratory objective. Central review of the endpoints was not done. Venetoclax was dosed daily using a stepwise escalation to target doses (200-600 mg) and then monthly rituximab commenced (375 mg/m2 in month 1 and 500 mg/m2 in months 2-6). Adverse events were graded according to the National Cancer Institute Common Terminology Criteria for adverse events version 4.0. Protocol-guided drug cessation was allowed for patients who achieved complete response (including complete response with incomplete marrow recovery) or negative bone marrow minimal residual disease. Analyses were done per protocol for all patients who commenced drug and included all patients who received at least one dose of venetoclax. Data were pooled across dose cohorts. Patients are still receiving therapy and follow-up is ongoing. The trial is registered at ClinicalTrials.gov, number NCT01682616. FINDINGS: Between Aug 6, 2012, and May 28, 2014, we enrolled 49 patients. Common grade 1-2 toxicities included upper respiratory tract infections (in 28 [57%] of 49 patients), diarrhoea (27 [55%]), and nausea (25 [51%]). Grade 3-4 adverse events occurred in 37 (76%) of 49 patients; most common were neutropenia (26 [53%]), thrombocytopenia (eight [16%]), anaemia (seven [14%]), febrile neutropenia (six [12%]), and leucopenia (six [12%]). The most common serious adverse events were pyrexia (six [12%]), febrile neutropenia (five [10%]), lower respiratory tract infection, and pneumonia (each three [6%]). Clinical tumour lysis syndrome occurred in two patients (resulting in one death) who initiated venetoclax at 50 mg. After enhancing tumour lysis syndrome prophylaxis measures and commencing venetoclax at 20 mg, clinical tumour lysis syndrome did not occur. The maximum tolerated dose was not identified; the recommended phase 2 dose of venetoclax in combination with rituximab was 400 mg. Overall, 42 (86%) of 49 patients achieved a response, including a complete response in 25 (51%) of 49 patients. 2 year estimates for progression-free survival and ongoing response were 82% (95% CI 66-91) and 89% (95% CI 72-96), respectively. Negative marrow minimal residual disease was attained in 20 (80%) of 25 complete responders and 28 (57%) of 49 patients overall. 13 responders ceased all therapy; among these all 11 minimal residual disease-negative responders remain progression-free off therapy. Two with minimal residual disease-positive complete response progressed after 24 months off therapy and re-attained response after re-initiation of venetoclax. INTERPRETATION: A substantial proportion of patients achieved an overall response with the combination of venetoclax and rituximab including 25 (51%) of 49 patients who achieved a complete response and 28 (57%) of 49 patients who achieved negative marrow minimal residual disease with acceptable safety. The depth and durability of responses observed with the combination offers an attractive potential treatment option for patients with relapsed or refractory chronic lymphocytic leukaemia and could allow some patients to maintain response after discontinuing therapy, a strategy that warrants further investigation in randomised studies. FUNDING: AbbVie Inc and Genentech Inc.

Rapid enhancement of two-step wiring plasticity by estrogen and NMDA receptor activity.

Cortical information storage requires combined changes in connectivity and synaptic strength between neurons, but the signaling mechanisms underlying this two-step wiring plasticity are unknown. Because acute 17beta-estradiol (E2) modulates cortical memory, we examined its effects on spine morphogenesis, AMPA receptor trafficking, and GTPase signaling in cortical neurons. Acute E2 application resulted in a rapid, transient increase in spine density, accompanied by temporary formation of silent synapses through reduced surface GluR1. These rapid effects of E2 were dependent on a Rap/AF-6/ERK1/2 pathway. Intriguingly, NMDA receptor (NMDAR) activation after E2 treatment potentiated silent synapses and elevated spine density for as long as 24 h. Hence, we show that E2 transiently increases neuronal connectivity by inducing dynamic nascent spines that "sample" the surrounding neuropil and that subsequent NMDAR activity is sufficient to stabilize or "hold" E2-mediated effects. This work describes a form of two-step wiring plasticity relevant for cortical memory and identifies targets that may facilitate recovery from brain injuries.

Novel analogs and stereoisomers of the marine toxin neodysiherbaine with specificity for kainate receptors.

Antagonists for kainate receptors (KARs), a family of glutamategated ion channels, are efficacious in a number of animal models of neuropathologies, including epilepsy, migraine pain, and anxiety. To produce molecules with novel selectivities for kainate receptors, we generated three sets of analogs related to the natural marine convulsant neodysiherbaine (neoDH), and we characterized their pharmacological profiles. Radioligand displacement assays with recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and KARs demonstrated that functional groups at two positions on the neoDH molecule are critical pharmacological determinants; only binding to the glutamate receptor (GluR)5-2a subunit was relatively insensitive to structural modifications of the critical functional groups. NeoDH analogs in which the l-glutamate congener was disrupted by epimerization retained low affinity for GluR5-2a and GluR6a KAR subunits. Most of the analogs showed agonist activity in electrophysiological recordings from human embryonic kidney-T/17 cells expressing GluR5-2a KARs, similar to the natural convulsant neoDH. In contrast, 2,4-epi-neoDH inhibited glutamate currents evoked from both GluR5-2a and GluR6a receptor-expressing cells. Therefore, this compound represents the first compound to exhibit functional antagonist activity on GluR5-2a and GluR6a KAR subunits without concurrent activity on AMPA receptor subunits. Finally, binding affinity of the synthetic ligands for the GluR5-2a subunit closely correlated with their seizurogenic potency, strongly supporting a role for receptors containing this subunit in the convulsant reaction to KAR agonists. The analogs described here offer further insight into structural determinants of ligand selectivity for KARs and potentially represent useful pharmacological tools for studying the role of KARs in synaptic physiology and pathology.

Small-molecule intramimics of formin autoinhibition: a new strategy to target the cytoskeletal remodeling machinery in cancer cells.

Although the cancer cell cytoskeleton is a clinically validated target, few new strategies have emerged for selectively targeting cell division by modulating the cytoskeletal structure, particularly ways that could avoid the cardiotoxic and neurotoxic effects of current agents such as taxanes. We address this gap by describing a novel class of small-molecule agonists of the mammalian Diaphanous (mDia)-related formins, which act downstream of Rho GTPases to assemble actin filaments, and their organization with microfilaments to establish and maintain cell polarity during migration and asymmetric division. GTP-bound Rho activates mDia family members by disrupting the interaction between the DID and DAD autoregulatory domains, which releases the FH2 domain to modulate actin and microtubule dynamics. In screening for DID-DAD disruptors that activate mDia, we identified two molecules called intramimics (IMM-01 and -02) that were sufficient to trigger actin assembly and microtubule stabilization, serum response factor-mediated gene expression, cell-cycle arrest, and apoptosis. In vivo analysis of IMM-01 and -02 established their ability to slow tumor growth in a mouse xenograft model of colon cancer. Taken together, our work establishes the use of intramimics and mDia-related formins as a new general strategy for therapeutic targeting of the cytoskeletal remodeling machinery of cancer cells.

Full domain closure of the ligand-binding core of the ionotropic glutamate receptor iGluR5 induced by the high affinity agonist dysiherbaine and the functional antagonist 8,9-dideoxyneodysiherbaine.

The prevailing structural model for ligand activation of ionotropic glutamate receptors posits that agonist efficacy arises from the stability and magnitude of induced domain closure in the ligand-binding core structure. Here we describe an exception to the correlation between ligand efficacy and domain closure. A weakly efficacious partial agonist of very low potency for homomeric iGluR5 kainate receptors, 8,9-dideoxyneodysiherbaine (MSVIII-19), induced a fully closed iGluR5 ligand-binding core. The degree of relative domain closure, approximately 30 degrees , was similar to that we resolved with the structurally related high affinity agonist dysiherbaine and to that of l-glutamate. The pharmacological activity of MSVIII-19 was confirmed in patch clamp recordings from transfected HEK293 cells, where MSVIII-19 predominantly inhibits iGluR5-2a, with little activation apparent at a high concentration (1 mm) of MSVIII-19 (<1% of mean glutamate-evoked currents). To determine the efficacy of the ligand quantitatively, we constructed concentration-response relationships for MSVIII-19 following potentiation of steady-state currents with concanavalin A (EC(50) = 3.6 microm) and on the nondesensitizing receptor mutant iGluR5-2b(Y506C/L768C) (EC(50) = 8.1 microm). MSVIII-19 exhibited a maximum of 16% of full agonist efficacy, as measured in parallel recordings with glutamate. Molecular dynamics simulations and electrophysiological recordings confirm that the specificity of MSVIII-19 for iGluR5 is partly attributable to interdomain hydrogen bond residues Glu(441) and Ser(721) in the iGluR5-S1S2 structure. The weaker interactions of MSVIII-19 with iGluR5 compared with dysiherbaine, together with altered stability of the interdomain interaction, may be responsible for the apparent uncoupling of domain closure and channel opening in this kainate receptor subunit.

Total synthesis and biological evaluation of neodysiherbaine A and analogues.

Dysiherbaine (1) and its congener neodysiherbaine A (2) are naturally occurring excitatory amino acids with selective and potent agonistic activity for ionotropic glutamate receptors. We describe herein the total synthesis of 2 and its structural analogues 3-8. Advanced key intermediate 16 was employed as a branching point to assemble a series of these analogues 3-8 with respect to the C8 and C9 functionalities, which would not have been accessible through manipulations of the natural product itself. The synthesis of key intermediate 16 features (i) stereocontrolled C-glycosylation to set the C6 stereocenter, (ii) concise synthesis of the bicyclic ether skeleton through chemo- and stereoselective dihydroxylation of the exo-olefin and stereoselective epoxidation of the endo-olefin, followed by epoxide ring opening/5-exo ring closure, and (iii) catalytic asymmetric hydrogenation of enamide ester to construct the amino acid appendage. A preliminary biological evaluation of analogues for their in vivo toxicity against mice and binding affinity for glutamate receptors showed that both the type and stereochemistry of the C8 and C9 functional groups affected the subtype selectivity of dysiherbaine analogues for members of the kainic acid receptor family.

Mechanisms of membrane estrogen receptor-alpha-mediated rapid stimulation of Ca2+ levels and prolactin release in a pituitary cell line.

The role of membrane estrogen receptor-alpha (mERalpha) in rapid nongenomic responses to 17beta-estradiol (E(2)) was tested in sublines of GH3/B6 rat prolactinoma cells selected for high (GH3/B6/F10) and low (GH3/B6/D9) mERalpha expression. E(2) elicited rapid, concentration-dependent intracellular Ca(2+) concentration ([Ca(2+)](i)) increases in the F10 subline. Lack of inhibition by thapsigargin depletion of intracellular Ca(2+) pools, together with abrogation of the response in Ca(2+)-free medium, suggested an extracellular source of Ca(2+) for this response. The participation of voltage-dependent channels in the E(2)-induced [Ca(2+)](i) increase was confirmed by the specific L-type Ca(2+) channel inhibitor nifedipine. For comparison, the D9 mERalpha-depleted subline was insensitive to steroid action via this signaling mechanism. [Ca(2+)](i) elevation was correlated with prolactin (PRL) release in the F10 cell line in as little as 3 min. E(2) caused a much higher PRL release than KCl treatment (which caused maximal Ca(2+) elevation), suggesting that secretion was also controlled by additional mechanisms. Participation of mERalpha in these effects was confirmed by the ability of E(2)-peroxidase (a cell-impermeable analog of E(2)) to cause these responses, blockage of the responses with the ER antagonist ICI 182 780, and the inability of the E(2) stereoisomer 17alpha-E(2) to elicit a response. Thus rapid exocytosis of PRL is regulated in these cells by mERalpha signaling to specific Ca(2+) channels utilizing extracellular Ca(2+) sources and additional signaling mechanisms.

Protein kinase A-dependent enhanced NMDA receptor function in pain-related synaptic plasticity in rat amygdala neurones.

Mechanisms of pain-related plasticity in the amygdala, a key player in emotionality, were studied at the cellular and molecular levels in a model of arthritic pain. The influence of the arthritis pain state induced in vivo on synaptic transmission and N-methyl-d-aspartate (NMDA) receptor function was examined in vitro using whole-cell voltage-clamp recordings of neurones in the latero-capsular part of the central nucleus of the amygdala (CeA), which is now defined as the 'nociceptive amygdala'. Synaptic transmission was evoked by electrical stimulation of afferents from the pontine parabrachial area (part of the spino-parabrachio-amygdaloid pain pathway) in brain slices from control rats and from arthritic rats. This study shows that pain-related synaptic plasticity is accompanied by protein kinase A (PKA)-mediated enhanced NMDA-receptor function and increased phosphorylation of NMDA-receptor 1 (NR1) subunits. Synaptic plasticity in the arthritis pain model, but not normal synaptic transmission in control neurones, was inhibited by a selective NMDA receptor antagonist. Accordingly, an NMDA receptor-mediated synaptic component was recorded in neurones from arthritic animals, but not in control neurones, and was blocked by inhibition of PKA but not protein kinase C (PKC). Exogenous NMDA evoked a larger inward current in neurones from arthritic animals than in control neurones, indicating a postsynaptic effect. Paired-pulse facilitation, a measure of presynaptic mechanisms, was not affected by an NMDA-receptor antagonist. Increased levels of phosphorylated NR1 protein, but not of total NR1, were measured in the CeA of arthritic rats compared to controls. Our results suggest that pain-related synaptic plasticity in the amygdala involves a critical switch of postsynaptic NMDA receptor function through PKA-dependent NR1 phosphorylation.