Emerging drugs in randomized controlled trials for sickle cell disease: are we on the brink of a new era in research and treatment?

ABSTRACT Introduction: Sickle cell disease (SCD) is caused by a mutation in the HBB gene which is key for making a component of hemoglobin. The mutation leads to the formation of an abnormal hemoglobin molecule called sickle hemoglobin (HbS). SCD is a chronic, complex disease with a multiplicity of pathophysiological targets; it has high morbidity and mortality. Hydroxyurea has for many years been the only approved drug for SCD; hence, the development of new therapeutics is critical. Areas covered: This article offers an overview of the key studies of new therapeutic options for SCD. We searched the PubMed database and Cochrane Database of Systemic Reviews for agents in early phase clinic trials and preclinical development. Expert opinion: Although knowledge of SCD has progressed, patient survival and quality of life must be improved. Phase II and phase III clinical trials investigating pathophysiology-based novel agents show promising results in the clinical management of SCD acute events. The design of longterm clinical studies is necessary to fully understand the clinical impact of these new therapeutics on the natural history of the disease. Furthermore, the building of global collaborations will enhance the clinical management of SCD and the design of primary outcomes of future clinical trials

NEW THERAPEUTIC OPTIONS FOR THE TREATMENT OF SICKLE CELL DISEASE

Sickle cell disease (SCD; ORPHA232; OMIM # 603903) is a chronic and invalidating disorder distributed worldwide, with high morbidity and mortality.  Given the disease complexity and the multiplicity of pathophysiological targets, development of new therapeutic options is critical, despite the positive effects of hydroxyurea (HU), for many years the only approved drug for SCD. New therapeutic strategies might be divided into (1) pathophysiology-related novel therapies and (2) innovations in curative therapeutic options such as hematopoietic stem cell transplantation and gene therapy. The pathophysiology related novel therapies are: a) Agents which reduce sickling or prevent sickle red cell dehydration; b) Agents targeting SCD vasculopathy and sickle cell-endothelial adhesive events; c) Anti-oxidant agents. This review highlights new therapeutic strategies in SCD and discusses future developments, research implications, and possible innovative clinical trials

Impaired pro‐resolving mechanisms promote abnormal NETosis , fueling autoimmunity in sickle cell disease

Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorders with still high mortality and morbidity and limited therapeutic options. SCD is characterized by anemia, chronic hemolysis, and acute vaso-occlusive painful crises. The biocomplexity of SCD goes beyond red cells, involving neutrophils and soluble factors such as cytokines or alternative complement pathway intensively cross-talking with vascular endothelial cells. In addition, in SCD, the overactivation of neutrophils contributes to the production of neutrophil extracellular traps (NETs) (1, 2). This might trigger endothelial vascular injury, promoting acute sickle cell related events and increasing the risk of infections in patients with SC

Effects of hypoxia\u2013reoxygenation stimuli on renal redox status and nuclear factor erythroid 2-related factor 2 pathway in sickle cell SADmice

Hypoxia\u2013reoxygenation (H/R) stress is known to increase oxidative stress in transgenic sickle mice and can cause organ failure. Here we described the effects of H/R on nuclear factor erythroid 2-related factor 2 (Nrf2) as a putative regulator of redox status in the kidneys of SAD mice investigating Nrf2-regulated antioxidant enzymes. Transgenic SAD mice and healthy C57Bl/6J mice were exposed to 4 h of hypoxia followed by various times of reoxygenation at ambient air (2 or 6 h). Regardless of the conditions (i.e. normoxia or H/R), SAD mice expressed higher renal oxidative stress levels. Nuclear Nrf2 protein expression decreased after 2 h post-hypoxia only in the medulla region of the kidney and only in SAD mice. Simultaneously, haem oxygenase transcripts were affected by H/R stimulus with a significant enhancement after 2 h post-hypoxia. Similarly, hypoxia inducible factor-1 staining increased after 2 h post-hypoxia in SAD mice in both cortex and medulla areas. Our data confirm that the kidneys are organs that are particularly sensitive toH/R stimuli in sickle cell SAD mice. Also, these results suggest an effect of the duration of recovery period (short vs. long) and specific responses according to kidney areas, medulla vs. cortex, on Nrf2 expression in response to H/R stimuli in SAD mice

Membrane association of peroxiredoxin-2 in red cells is mediated by n-terminal cytoplasmic domain of band 3

Band 3(B3),the anion transporter, is an integral membrane protein that plays a key structural role by anchor in the plasmamembrane to the spectrin-based membrane skeleton in the red cell. In addition, it also plays a critical role in the assembly of glycolytic enzymes to regulate red cell metabolism. However, its ability to recruit proteins that can prevent membrane oxidation has not been previously explored. In this study, using a variety of experimental approaches including cross-linking studies, fluorescence and dichroic measurements,surface plasmon resonance analysis, and proteolytic digestion assays, we document that the antioxidant protein peroxiredoxin-2(PRDX2), the third most abundant cytoplasmic protein in RBCs, interacts with the cytoplasmic domain of B3. The surface electrostatic potential analysis and stoichiometry measurements revealed that the N-terminal peptide of B3 is involved in the interaction. PRDX2 underwent a conformational change upon its binding to B3 without losing its peroxidase activity. Hemichrome formation induced by phenylhydrazine of RBCs prevented membrane association of PRDX2, implying overlapping binding sites. Documentation of the absence of binding of PRDX2 to B3 Neapolis red cell membranes, in which the initial N-terminal 11 amino acids are deleted, enabled us to conclude that PRDX2 binds to the N-terminal cytoplasmic domain of B3 and that the first 11 amino acids of this domain are crucial for PRDX2 membrane association in intact RBCs. These findings imply yet another important role for B3 in regulating red cell membrane function

ERK 1/2 activation does not contribute to increased survival mediated by bone marrow cells after 90% partial hepatectomy in wistar rats

We investigated the influence of bone marrow cells upon activation of ERK ½ in an animal model of 90% PH. Phosphorylated ERK 1/2 was evaluated by western blot. No differences were found between the groups. Thus, increased survival does not appear to be mediated by ERK 1/2 activation

Hypoxia-reperfusion affects osteogenic lineage and promotes sickle cell bone disease

Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorder, characterized by severe organ complication. Sickle bone disease (SBD) affects the large part of SCD patients and its pathogenesis has been only partially investigated. Here, we studied bone homeostasis in humanized mouse model for SCD. Under normoxia, SCD mice display bone loss and bone impairment with increased osteoclast and reduced osteoblast activity. Hypoxia/reperfusion (H/R) stress, mimicking acute vaso-occlusive crises (VOCs), increased bone turnover, osteoclast activity (RankL) and osteoclast recruitment (Rank) with up-regulation of Il6 as pro-resorptive cytokine. This was associated with further suppression of osteogenic lineage (Runx2, Sparc). In order to interfer with the development of SBD, zoledronic-acid, a potent inhibitor of osteoclast activity/osteoclastogenesis and promoter of osteogenic lineage, was used in H/R exposed mice. Zoledronic-acid markedly inhibited osteoclast activity and recruitment, promoting osteogenic lineage. The recurrent H/R stress further worsened bone structure, increased bone turnover, depressed osteoblastogenesis (Runx2, Sparc) and increased both osteoclast activity (RankL, Cathepsin k) and osteoclast recruitment (Rank) in SCD mice compared to either normoxic or single H/R episode SCD mice. Zoledronic-acid used before recurrent VOCs prevented bone impairment and promoted osteogenic lineage. Our findings support the view that SBD is related to osteoblast impairment and increased osteoclast activity resulted from local hypoxia, oxidative stress and the release of pro-resorptive cytokine such as IL6. Zoledronic acid might act on both osteoclast and osteoblast compartment as multimodal therapy to prevent SBD

Bitopertin, a selective oral GLYT1 inhibitor, improves anemia in a mouse model of \u3b2-thalassemia

Anemia of \u3b2-thalassemia is caused by ineffective erythropoiesis and reduced red cell survival. Several lines of evidence indicate that iron/heme restriction is a potential therapeutic strategy for the disease. Glycine is a key initial substrate for heme and globin synthesis. We provide evidence that bitopertin, a glycine transport inhibitor administered orally, improves anemia, reduces hemolysis, diminishes ineffective erythropoiesis, and increases red cell survival in a mouse model of \u3b2-thalassemia (Hbbth3/+ mice). Bitopertin ameliorates erythroid oxidant damage, as indicated by a reduction in membrane-associated free \u3b1-globin chain aggregates, in reactive oxygen species cellular content, in membrane-bound hemichromes, and in heme-regulated inhibitor activation and eIF2\u3b1 phosphorylation. The improvement of \u3b2-thalassemic ineffective erythropoiesis is associated with diminished mTOR activation and Rab5, Lamp1, and p62 accumulation, indicating an improved autophagy. Bitopertin also upregulates liver hepcidin and diminishes liver iron overload. The hematologic improvements achieved by bitopertin are blunted by the concomitant administration of the iron chelator deferiprone, suggesting that an excessive restriction of iron availability might negate the beneficial effects of bitopertin. These data provide important and clinically relevant insights into glycine restriction and reduced heme synthesis strategies for the treatment of \u3b2-thalassemia