Ravulizumab (ALXN1210) in patients with paroxysmal nocturnal hemoglobinuria: results of 2 phase 1b/2 studies.

Ravulizumab (ALXN1210), a humanized monoclonal antibody to complement component C5, was engineered from eculizumab to have a substantially longer terminal half-life, permitting longer dosing intervals for paroxysmal nocturnal hemoglobinuria (PNH) treatment. Two phase 1b/2 multicenter open-label studies evaluated efficacy and safety of multiple doses and regimens of ravulizumab in PNH patients naive to complement-inhibitor treatment. Patients in study 103 (n = 13) received ravulizumab 900 mg (lower trough exposure) or 1800 mg every 4 weeks (higher trough exposure); those in study 201 (n = 26) received 1000 mg every 4, 1600 mg every 6, 2400 mg every 8, or 5400 mg every 12 weeks. Trough exposure levels with study 201 dosing regimens were similar to the study 103 900-mg every-4-weeks regimen. Rapid sustained reduction of plasma lactate dehydrogenase (LDH) occurred across all cohorts (73%-90% at end point vs baseline). A greater proportion of patients had normalized LDH (<234 U/L) at least once from days 29 to 253 in the higher- (85.7%) vs lower-trough-exposure (50.0%-83.3%) cohorts; the weighted average of the proportion of instances of LDH normalization from days 29 to 253 was highest in higher- vs lower-trough-exposure cohorts (62.3% vs 31.4%-54.5%). No patients in the higher-trough-exposure cohort, but 1 to 2 patients in all lower-trough-exposure cohorts, experienced breakthrough hemolysis. Ravulizumab improved quality of life (QoL) measures in all cohorts. Two patients experienced meningococcal infections; both recovered and continued in the study. In summary, ravulizumab provided rapid and sustained reduction in complement-mediated hemolysis and improved QoL at dosing intervals up to 12 weeks. This trial was registered at www.clinicaltrials.gov as #NCT02598583 (study 103) and NCT02605993 (study 201).

Hypothalamic orexin stimulates feeding-associated glucose utilization in skeletal muscle via sympathetic nervous system.

Hypothalamic neurons containing orexin (hypocretin) are activated during motivated behaviors and active waking. We show that injection of orexin-A into the ventromedial hypothalamus (VMH) of mice or rats increased glucose uptake and promoted insulin-induced glucose uptake and glycogen synthesis in skeletal muscle, but not in white adipose tissue, by activating the sympathetic nervous system. These effects of orexin were blunted in mice lacking beta-adrenergic receptors but were restored by forced expression of the beta(2)-adrenergic receptor in both myocytes and nonmyocyte cells of skeletal muscle. Orexin neurons are activated by conditioned sweet tasting and directly excite VMH neurons, thereby increasing muscle glucose metabolism and its insulin sensitivity. Orexin and its receptor in VMH thus play a key role in the regulation of muscle glucose metabolism associated with highly motivated behavior by activating muscle sympathetic nerves and beta(2)-adrenergic signaling.

Splenectomy normalizes hematocrit in murine polycythemia vera.

Splenic enlargement (splenomegaly) develops in numerous disease states, although a specific pathogenic role for the spleen has rarely been described. In polycythemia vera (PV), an activating mutation in Janus kinase 2 (JAK2(V617)) induces splenomegaly and an increase in hematocrit. Splenectomy is sparingly performed in patients with PV, however, due to surgical complications. Thus, the role of the spleen in the pathogenesis of human PV remains unknown. We specifically tested the role of the spleen in the pathogenesis of PV by performing either sham (SH) or splenectomy (SPL) surgeries in a murine model of JAK2(V617F)-driven PV. Compared to SH-operated mice, which rapidly develop high hematocrits after JAK2(V617F) transplantation, SPL mice completely fail to develop this phenotype. Disease burden (JAK2(V617)) is equivalent in the bone marrow of SH and SPL mice, however, and both groups develop fibrosis and osteosclerosis. If SPL is performed after PV is established, hematocrit rapidly declines to normal even though myelofibrosis and osteosclerosis again develop independently in the bone marrow. In contrast, SPL only blunts hematocrit elevation in secondary, erythropoietin-induced polycythemia. We conclude that the spleen is required for an elevated hematocrit in murine, JAK2(V617F)-driven PV, and propose that this phenotype of PV may require a specific interaction between mutant cells and the spleen.

Control of cell growth and survival by enzymes of the fatty acid synthesis pathway in HCT-116 colon cancer cells.

PURPOSE: For many tumor cells, de novo lipogenesis is a requirement for growth and survival. A considerable body of work suggests that inhibition of this pathway may be a powerful approach to antineoplastic therapy. It has recently been shown that inhibition of various steps in the lipogenic pathway individually can induce apoptosis or loss of viability in tumor cells. However, it is not clear whether quantitative differences exist in the ability of lipogenic enzymes to control tumor cell survival. We present a systematic approach that allows for a direct comparison of the control of lipogenic pathway enzymes over tumor cell growth and apoptosis using different cancer cells. EXPERIMENTAL DESIGN: RNA interference-mediated, graded down-regulation of fatty acid synthase (FAS) pathway enzymes was employed in combination with measurements of lipogenesis, apoptosis, and cell growth. RESULTS: In applying RNA interference titrations to two lipogenic enzymes, acetyl-CoA carboxylase 1 (ACC1) and FAS, we show that ACC1 and FAS both significantly control cell growth and apoptosis in HCT-116 cells. These results also extend to PC-3 and A2780 cancer cells. CONCLUSIONS: Control of tumor cell survival by different steps in de novo lipogenesis can be quantified. Because ACC1 and FAS both significantly control tumor cell growth and apoptosis, we propose that pharmacologic inhibitors of either enzyme might be useful agents in targeting cancer cells that critically rely on fatty acid synthesis. The experimental approach described here may be extended to other targets or disease-relevant pathways to identify steps suitable for therapeutic intervention.

The metabolic and cardiovascular effects of hyperthyroidism are largely independent of beta-adrenergic stimulation.

Hyperthyroidism and states of adrenergic hyperactivity have many common clinical features, suggesting similar pathogenic mechanisms of action. The widespread use of beta-adrenergic receptor (betaAR) antagonists (beta-blockers) to treat hyperthyroidism has led to the belief that the physiological consequences of thyroid hormone (TH) excess are mediated in part via catecholamine signaling through betaARs. To test this hypothesis, we compared the response to TH excess in mice lacking the three known betaARs (beta-less) vs. wild-type (WT) mice. Although beta-less mice had a lower heart rate at baseline in comparison to WT mice, the metabolic and cardiovascular responses to hyperthyroidism were equivalent in both WT and beta-less mice. These data indicate that the metabolic and cardiovascular effects of TH excess are largely independent of betaARs. These findings suggest that the efficacy of clinical treatment of hyperthyroidism with beta-blockers is due to antagonism of sympathetic signaling, and that this process functions independently of TH action.

betaAR signaling required for diet-induced thermogenesis and obesity resistance.

Excessive caloric intake is thought to be sensed by the brain, which then activates thermogenesis as a means of preventing obesity. The sympathetic nervous system, through beta-adrenergic receptor (betaAR) action on target tissues, is likely the efferent arm of this homeostatic mechanism. To test this hypothesis, we created mice that lack the three known betaARs (beta-less mice). beta-less mice on a Chow diet had a reduced metabolic rate and were slightly obese. On a high-fat diet, beta-less mice, in contrast to wild-type mice, developed massive obesity that was due entirely to a failure of diet-induced thermogenesis. These findings establish that betaARs are necessary for diet-induced thermogenesis and that this efferent pathway plays a critical role in the body's defense against diet-induced obesity.