Rifaximin for sickle cell disease

Endari treatment ameliorates sickle cell-related disruption in intestinal barrier functions and is associated with prolonged survival in sickle cell mice

BACKGROUND

Endari (L-glutamine) is a conditional amino acid that reduces the frequency of vaso-occlusive crisis (VOC) in sickle cell disease (SCD).

AIM

To investigate whether Endari could ameliorate intestinal barrier function and improve survival outcomes in SCD.

METHODS

We treated female Townes SCD mice with Endari and evaluated their intestinal barrier functions by measuring the recovery of orally administered fluorescein isothiocyanate (FITC)-conjugated dextran 4 kDa in serum, and serum intestinal fatty acid binding proteins (iFABP) and lipopolysaccharide (LPS) concentrations by ELISA. We also explored the impact the Endari has on the survival of the SCD mice that underwent repeated experimentally-induced VOC.

RESULTS

Compared to SCD mice treated with water only, Endari-treated mice showed improved intestinal barrier functions, with decrease in the barrier permeability and reduction in the translocation of lipopolysaccharides from the intestinal lumen into the circulation. These changes occurred after only 4 weeks of Endari treatment. Improved intestinal barrier function was also associated with prolonged survival in Endari-treated SCD mice after repeated experimentally-induced VOC.

CONCLUSION

Our findings provide the evidence supporting the beneficial effects of Enadri in improving intestinal barrier function and associated survival outcomes in SCD.

Intestinal barrier dysfunction in murine sickle cell disease is associated with small intestine neutrophilic inflammation, oxidative stress, and dysbiosis

The intestinal microbiome has emerged as a potential contributor to the severity of sickle cell disease (SCD). We sought to determine whether SCD mice exhibit intestinal barrier dysfunction, inflammation, and dysbiosis. Using the Townes humanized sickle cell mouse model, we found a 3-fold increase in intestinal permeability as assessed via FITC-dextran (4 kDa) assay in SS (SCD) mice compared to AA (wild type) mice (n = 4, p < 0.05). This was associated with 25 to 50% decreases in claudin-1, 3, and 15 and zonula occludens-1 gene expression (n = 8-10, p < 0.05) in the small intestine. Increased Ly6G staining demonstrated more neutrophils in the SS small intestine (3-fold, n = 5, p < 0.05) associated with increased expression of TNFα, IL-17A, CXCL1, and CD68 (2.5 to 5-fold, n = 7-10, p < 0.05). In addition, we observed 30 to 55% decreases in superoxide dismutase-1, glutathione peroxidase-1, and catalase antioxidant enzyme expression (n = 7-8, p < 0.05) concomitant to an increase in superoxide (2-fold, n = 4, p < 0.05). Importantly, all significant observations of a leaky gut phenotype and inflammation were limited to the small intestine and not observed in the colon. Finally, characterization of the composition of the microbiome within the small intestine revealed dysbiosis in SS mice compared to their AA littermates with 47 phyla to species-level significant alterations in amplicon sequence variants. We conclude that the intestinal barrier is compromised in SCD, associated with decreased gene expression of tight junction proteins, enhanced inflammation, oxidative stress, and gut microbiome dysbiosis, all specific to the small intestine.

Effects of GBT1118, a voxelotor analog, on intestinal pathophysiology in sickle cell disease

Voxelotor is an allosteric haemoglobin (Hb) modulator that binds covalently and reversibly to Hb alpha chain to facilitate improved Hb-O₂ affinity and arterial oxygen. It, therefore, reduces the susceptibility of erythrocytes carrying Haemoglobin S to sickle. In this study, we have used GBT1118, an analog of voxelotor, to treat male Townes sickle cell disease (SCD) mice to investigate whether the Hb modulator could attenuate the intestinal pathophysiologic changes associated with SCD. Compared with mice fed with control chow, GBT1118-treated mice showed improvement in the intestinal pathophysiology. These mice exhibited improved small intestinal barrier functions, reduced intestinal microbial density, reduced enterocyte injury, lower serum lipopolysaccharides and smaller spleens. These improvements were observed after only 3 weeks of GBT1118 treatment. Benefits were also observed after experimentally-induced vaso-occlusive crisis (VOC). Recovery from the VOC-induced changes was faster in mice that were treated with GBT1118. The improved small intestinal barrier function was associated with higher expression of genes encoding enterocyte E-cadherin, JAM-A, ZO-1, MUC-2 and occludin while the lower intestinal microbial density associated with higher expression of genes encoding the antimicrobial peptides defensin-α 1 and defensin-α 4. Our findings provide the evidence to support the beneficial effects of GBT1118 in SCD-related intestinal pathophysiology.

Management of Older Adults with Sickle Cell Disease: Considerations for Current and Emerging Therapies

People with sickle cell disease (SCD) are living longer than ever before, with the median survival increasing from age 14 years in 1973, beyond age 40 years in the 1990s, and as high as 61 years in recent cohorts from academic centers. Improvements in survival have been attributed to initiatives, such as newborn screening, penicillin prophylaxis, vaccination against encapsulated organisms, better detection and treatment of splenic sequestration, and improved transfusion support. There are an estimated 100,000 people living with SCD in the United States and millions of people with SCD globally. Given that the number of older adults with SCD will likely continue to increase as survival improves, better evidence on how to manage this population is needed. When managing older adults with SCD (defined herein as age ≥ 40 years), healthcare providers should consider the potential pitfalls of extrapolating evidence from existing studies on current and emerging therapies that have typically been conducted with participants at mean ages far below 40 years. Older adults with SCD have historically had little to no representation in clinical trials; therefore, more guidance is needed on how to use current and emerging therapies in this population. This article summarizes the available evidence for managing older adults with SCD and discusses potential challenges to using approved and emerging drugs in this population.

Microbial gut evaluation in an angolan paediatric population with sickle cell disease

Sickle cell disease (SCD) is one of the most common genetic conditions worldwide. It can contribute up to 90% of under-5 mortality in sub-Saharan Africa. Clinical manifestations are very heterogeneous, and the intestinal microbiome appears to be crucial in the modulation of inflammation, cell adhesion and induction of aged neutrophils, the main interveners of recurrent vaso-occlusive crisis. Enterocyte injury, increased permeability, altered microbial composition and bacterial overgrowth have all been documented as microbial and pathophysiologic changes in the gut microbiome of SCD patients in recent studies. Our aim was to sequence the bacterial 16S rRNA gene in order to characterize the gut microbiome of Angolan children with SCA and healthy siblings as a control. A total of 72 stool samples were obtained from children between 3 and 14 years old. Our data showed that the two groups exhibit some notable differences in microbiota relative abundance at different classification levels. Children with SCA have a higher number of the phylum Actinobacteria. As for the genus level, Clostridium cluster XI bacteria was more prevalent in the SCA children, whereas the siblings had a higher abundance of Blautia, Aestuariispira, Campylobacter, Helicobacter, Polaribacter and Anaerorhabdus. In this study, we have presented the first microbiota analysis in an Angolan paediatric population with SCD and provided a detailed view of the microbial differences between patients and healthy controls. There is still much to learn before fully relying on the therapeutic approaches for gut modulation, which is why more research in this field is crucial to making this a reality.

How Hydroxyurea Alters the Gut Microbiome: A Longitudinal Study Involving Angolan Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is an inherited hematological disorder and a serious global health problem, especially in Sub-Saharan Africa. Although hydroxyurea (HU) is the leading treatment for patients with SCA, its effects on the gut microbiome have not yet been explored. In this context, the aim of this study was to investigate this association by characterizing the gut microbiome of an Angolan SCA pediatric population before and after 6 months of HU treatment. A total of 66 stool samples were obtained and sequenced for the 16S rRNA gene (V3-V4 regions). Significant associations were observed in alpha and beta-diversity, with higher values of species richness for the children naïve for HU. We also noticed that children after HU had higher proportions of several beneficial bacteria, mostly short-chain fatty acids (SCFAs) producing species, such as Blautia luti, Roseburia inulinivorans, Eubacterium halli, Faecalibacterium, Ruminococcus, Lactobacillus rogosae, among others. In addition, before HU there was a higher abundance of Clostridium_g24, which includes C. bolteae and C. clostridioforme, both considered pathogenic. This study provides the first evidence of the HU effect on the gut microbiome and unravels several microorganisms that could be considered candidate biomarkers for disease severity and HU efficacy.

Emerging drugs for the treatment of sickle cell disease: a review of phase II/III trials

INTRODUCTION

The substitution of glutamic acid by valine on the ß-globin gene produces the hemoglobin S variant responsible for sickle cell disease (SCD), a disorder that affects millions of people worldwide and leads to acute and cumulative organ damage. Even though life expectancy has significantly improved where the best medical care is available, there are still few therapeutic options for SCD and those are limited by their availability, cost, and individual toxicities.

AREAS COVERED

This review summarizes the clinical data on current treatments for SCD and emerging therapies studied in the acute setting as well as potential disease-modifying agents, with an emphasis on the FDA-approved agents.

EXPERT OPINION

Hydroxyurea has been a gold standard for two decades, showing benefits in acute complications and overall survival in sickle cell anemia, although data is lacking for certain genotypes such as hemoglobin SC. As progress is made in our understanding of the pathophysiological networks characterizing SCD, numerous pathways appear to be targetable, with L-glutamine, Crizanlizumab and Voxelotor now approved by the FDA. Pursuing a multi-agent approach could alter the disease course in a more effective fashion and provide an alternative option to curative therapies, but longer clinical studies are needed.

L-glutamine for sickle cell disease: more than reducing redox

Oxidative stress is a major contributor to the pathophysiology of sickle cell disease (SCD) including hemolysis and vaso-occlusive crisis (VOC). L-glutamine is a conditionally essential amino acid with important roles, including the synthesis of antioxidants, such as reduced glutathione and the cofactors NAD(H) and NADP(H), as well as nitric oxide. Given the increased levels of oxidative stress and lower (NADH):(NAD +  + NADH) ratio in sickle erythrocytes that adversely affects the blood rheology compared to normal red blood cells, L-glutamine was investigated for its therapeutic potential to reduce VOC. While L-glutamine was approved by the United States (US) Food and Drug Administration to treat SCD, its impact on the redox environment in sickle erythrocytes is not fully understood. The mechanism through which L-glutamine reduces VOC in SCD is also not clear. In this paper, we will summarize the results of the Phase 3 study that led to the approval of L-glutamine for treating SCD and discuss its assumed mechanisms of action. We will examine the role of L-glutamine in health and propose how the extra-erythrocytic functions of L-glutamine might contribute to its beneficial effects in SCD. Further research into the role of L-glutamine on extra-erythrocyte functions might help the development of an improved formulation with more efficacy.

Genes modulating intestinal permeability and microbial community are dysregulated in sickle cell disease

Based on previous studies showing abnormalities in the intestinal pathophysiology characterized by disruption in the gut barrier functions, and alteration in the intestinal microbial load and composition, we set out in the study to examine the expression of genes that might be involved in mediating these changes in Townes sickle cell disease (SCD) mice at 6 months old compared to non-SCD control mice. Using qPCR on total RNA isolated from the intestine, we found downregulation of the TJ genes JAM-A, Occludin, and ZO-1 in both the small intestine and colon. E-Cadherin and MUC2 were also downregulated. In contrast, gene encoding claudin-2 that mediates increase permeability to water and ions was upregulated in the small intestine. Claudin-2 upregulation is usually also associated with ongoing inflammation. Intestinal epithelium also includes Paneth cells that produce antimicrobial peptides (AMPs) that regulate intestinal microbial community. We also found that the expression of the genes encoding the AMPs defensin-α4 was reduced in the small intestine and colon and defensin-α1 in the colon in the SCD mice. Our findings are novel and provide direction for further studies into the characteristics and mechanisms of the intestinal pathophysiologic changes observed in SCD.

Fecal Microbiota Transplant for Hematologic and Oncologic Diseases: Principle and Practice

Simple Summary

The transfer of a normal intestinal microbial community from healthy donors by way of their fecal material into patients with various diseases is an emerging therapeutic approach, particularly to treat patients with recurrent or refractory C. difficile infections (CDI). This approach, called fecal microbiota transplant (FMT), is increasingly being applied to patients with hematologic and oncologic diseases to treat recurrent CDI, modulate treatment-related complications, and improve cancer treatment outcome. In this review paper, we discussed the principles and methods of FMT. We examined the results obtained thus far from its use in hematologic and oncologic patients. We also propose novel uses for the therapeutic approach and appraised the challenges associated with its use, especially in this group of patients.

Abstract

Understanding of the importance of the normal intestinal microbial community in regulating microbial homeostasis, host metabolism, adaptive immune responses, and gut barrier functions has opened up the possibility of manipulating the microbial composition to modulate the activity of various intestinal and systemic diseases using fecal microbiota transplant (FMT). It is therefore not surprising that use of FMT, especially for treating relapsed/refractory Clostridioides difficile infections (CDI), has increased over the last decade. Due to the complexity associated with and treatment for these diseases, patients with hematologic and oncologic diseases are particularly susceptible to complications related to altered intestinal microbial composition. Therefore, they are an ideal population for exploring FMT as a therapeutic approach. However, there are inherent factors presenting as obstacles for the use of FMT in these patients. In this review paper, we discussed the principles and biologic effects of FMT, examined the factors rendering patients with hematologic and oncologic conditions to increased risks for relapsed/refractory CDI, explored ongoing FMT studies, and proposed novel uses for FMT in these groups of patients. Finally, we also addressed the challenges of applying FMT to these groups of patients and proposed ways to overcome these challenges.

Intestinal pathophysiological abnormalities in steady state and after vaso-occlusive crisis in murine sickle cell disease

We showed in the present study that, not unlike in adult patients with sickle cell disease (SCD), Townes mice exhibit increases in serum intestinal fatty acid binding proteins and lipopolysaccharides (LPS), together with a breach in the intestinal barrier. These abnormalities increased rapidly after the induction of vaso-occlusive crisis (VOC). We also confirmed higher intestinal microbial density in SCD. These findings support the concept that SCD and/or its complications, and not hospitalisation or medications, are responsible for the intestinal pathophysiological changes. The present results provide the basis for use of Townes mice to further elucidate the mechanistic relationship between intestinal pathophysiology and VOC.

Vaso-occlusive crisis in sickle cell disease: a vicious cycle of secondary events

Painful vaso-occlusive crisis (VOC) remains the most common reason for presenting to the Emergency Department and hospitalization in patients with sickle cell disease (SCD). Although two new agents have been approved by the Food and Drug Administration for treating SCD, they both target to reduce the frequency of VOC. Results from studies investigating various approaches to treat and shorten VOC have so far been generally disappointing. In this paper, we will summarize the complex pathophysiology and downstream events of VOC and discuss the likely reasons for the disappointing results using monotherapy. We will put forward the rationale for exploring some of the currently available agents to either protect erythrocytes un-involved in the hemoglobin polymerization process from sickling induced by the secondary events, or a multipronged combination approach that targets the complex downstream pathways of VOC.

Allogeneic hematopoietic stem cell transplant for sickle cell disease: The why, who, and what

Allogeneic hematopoietic stem cell transplants (allo-HSCTs) from matched-related donors (MRDs), mismatched-related donors (MMRDs), and matched-unrelated donors (MUDs) are increasingly being used to treat sickle cell disease (SCD) in both pediatric and adult patients. The overall results have been extremely encouraging, especially if a MRD is available and the transplant being performed before the age of 13. Although there is a general consensus that patients with high-risk SCD, even in adults and irrespective of donor characteristics, should be offered allo-HSCT, the debates on optimal patient selection and timing of transplant have yet to be resolved. Unlike patients with hematologic malignancies, there are also a number of clinical issues that require to be addressed in patients with SCD undergoing allo-HSCT. In this review, we will discuss the reasons allo-HSCT should be offered more widely to patients with SCD, the challenges facing physicians in patient selection and timing of transplant, and the awareness of and solutions to prevent the complications that are unique or more common in SCD undergoing allo-HSCT.

Antibiotics to modify sickle cell disease vaso-occlusive crisis?

Despite the availability of hydroxyurea, the clinical use of the medication among patients with sickle cell disease (SCD) remains low in the United States. Given the high healthcare utilization cost, SCD requires new therapeutic approaches. Recent studies demonstrated bacterial overgrowth and dysbiosis-related intestinal pathophysiological changes in SCD. Intestinal microbes regulate neutrophil ageing. Aged and activated neutrophils contribute to the pathogenesis of vaso-occlusive crisis (VOC) in SCD. In this paper, we will review the pre-clinical and clinical data on how antibiotics might reduce the intestinal microbial density and influence the course of VOC. Based on these observations, we will discuss rationales for and potential challenges to antibiotic-based therapeutic approaches that may modify the clinical course of VOC in SCD.

Randomized phase 2 trial of Intravenous Gamma Globulin (IVIG) for the treatment of acute vaso-occlusive crisis in patients with sickle cell disease: Lessons learned from the midpoint analysis

Sickle Cell Disease (SCD) is a chronic hemolytic disorder associated with frequent pain episodes, end organ damage and a shortened lifespan. Currently there exist no disease specific targeted therapies for the treatment of acute vaso-occlusive crisis (VOC) and management with analgesics and hydration is purely supportive. Improvement in understanding of disease pathophysiology has resulted in a great interest in disease modifying novel therapies and many are being evaluated in clinical trials. Here we report the results from the pre-specified mid-point analysis of the Phase 2 study of Intravenous Gamma Globulin (IVIG) for the treatment of acute VOC in patients with SCD and lessons learned.

Bidirectional interaction between intestinal microbiome and cancer: opportunities for therapeutic interventions

Gut microbiota composition influences the balance between human health and disease. Increasing evidence suggests the involvement of microbial factors in regulating cancer development, progression, and therapeutic response. Distinct microbial species have been implicated in modulating gut environment and architecture that affects cancer therapy outcomes. While some microbial species offer enhanced cancer therapy response, others diminish cancer treatment efficacy. In addition, use of antibiotics, often to minimize infection risks in cancer, causes intestinal dysbiosis and proves detrimental. In this review we discuss the role of gut microbiota in cancer development and therapy. We also provide insights into future strategies to manipulate the microbiome and gut epithelial barrier to augment therapeutic responses while minimizing toxicity or infection risks.