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Individuals with sickle cell disease (SCD) are living further into adulthood in high-resource countries. However, despite increased quantity of life, recurrent, acute painful episodes cause significant morbidity for affected individuals. These SCD-related painful episodes, also referred to as vaso-occlusive crises (VOCs), have multifactorial causes, and they often occur as a result of multicellular aggregation and vascular adherence of red blood cells, neutrophils, and platelets, leading to recurrent and unpredictable occlusion of the microcirculation. In addition to severe pain, long-term complications of vaso-occlusion may include damage to muscle and/or bone, in addition to vital organs such as the liver, spleen, kidneys, and brain. Severe pain associated with VOCs also has a substantial detrimental impact on quality of life for individuals with SCD, and is associated with increased health care utilization, financial hardship, and impairments in education and vocation attainment. Previous treatments have targeted primarily SCD symptom management, or were broad nontargeted therapies, and include oral or parenteral hydration, analgesics (including opioids), nonsteroidal anti-inflammatory agents, and various other types of nonpharmacologic pain management strategies to treat the pain associated with VOC. With increased understanding of the pathophysiology of VOCs, there are several new potential therapies that specifically target the pathologic process of vaso-occlusion. These new therapies may reduce cell adhesion and inflammation, leading to decreased incidence of VOCs and prevention of end-organ damage. In this review, we consider the benefits and limitations of current treatments to reduce the occurrence of VOCs in individuals with SCD and the potential impact of emerging treatments on future disease management.

Sickle cell disease (SCD) affects millions of individuals worldwide, and is characterized by both acute, episodic pain and chronic, persistent pain. Despite the significant burden of the disease, clinicians continue to face significant challenges in treating SCD pain due to variability in pain experiences. The objectives of this study were (1) to identify distinct pain subgroups based on demographic and biopsychosocial characteristics and (2) to evaluate the relationship between the subgroups and pain impact – a SCD-disease specific measure of pain interference. To achieve these objectives, we performed a hierarchical cluster analysis on a cross-sectional sample of adults with SCD who are enrolled in the Globin Research Network Data and Discovery (GRNDaD) registry. Five hundred thirty-two participants (61% females and 64% with chronic pain) were included in the analysis. Six distinct subgroups were identified, 3 with chronic pain (Clusters 1–3) and 3 without chronic pain (Clusters 4–6). Despite differences in biological markers of disease severity such as genotype, hemoglobin and fetal hemoglobin percentage, chronic pain subgroups had comparable odds of reporting worse pain impact, suggesting that chronic pain has a disproportionate influence on SCD pain when compared to other factors. Longitudinal studies are needed to further validate these findings and to determine how these pain subgroups may change. Overall, our findings indicate that understanding and preventing chronic pain in SCD must be a top priority to improve the quality of life of those living with SCD.

Newly produced platelets acquire a low activation state, but whether the megakaryocyte plays a role in this outcome has not been fully uncovered. Mesenchymal stem cells (MSCs) were previously shown to promote platelet production and lower platelet activation. We found that healthy megakaryocytes transfer mitochondria to MSCs, which is mediated by connexin 43 (Cx43) gap junctions on MSCs and leads to platelets at a low energetic state with increased LYN activation, characteristic of resting platelets with increased LYN activation, characteristic of resting platelets. On the contrary, MSCs have a limited ability to transfer mitochondria to megakaryocytes. Sickle cell disease (SCD) is characterized by hemolytic anemia and results in heightened platelet activation, contributing to numerous disease complications. Platelets in SCD mice and human samples had a heightened energetic state with increased glycolysis. MSC exposure to heme in SCD led to decreased Cx43 expression and a reduced ability to uptake mitochondria from megakaryocytes. This prevented LYN activation in platelets and contributed to increased platelet activation at steady state. Altogether, our findings demonstrate an effect of hemolysis in the microenvironment leading to increased platelet activation in SCD. These findings have the potential to inspire new therapeutic targets to relieve thrombosis-related complications of SCD and other hemolytic conditions.

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by painful vaso-occlusive crises (VOC) and chronic hemolysis. The mononuclear phagocyte system is pivotal to SCD pathophysiology, but the mechanisms governing monocyte/macrophage differentiation remain unknown. This study examined the influence of hemolysis on circulating monocyte trajectories in SCD. We discovered that hemolysis stimulated CSF-1 production, partly by endothelial cells via Nrf2, promoting classical monocyte (CMo) differentiation into blood patrolling monocytes (PMo) in SCD mice. However, hemolysis also upregulated CCL-2 through IFN-I, inducing CMo transmigration and differentiation into tissue monocyte-derived macrophages. Blocking CMo transmigration by anti-P-selectin antibody in SCD mice increased circulating PMo, corroborating that CMo-to-tissue macrophage differentiation occurs at the expense of CMo-to-blood PMo differentiation. We observed a positive correlation between plasma CSF-1/CCL-2 ratios and blood PMo levels in SCD patients, underscoring the clinical significance of these two opposing factors in monocyte differentiation. Combined treatment with CSF-1 and anti-P-selectin antibody more effectively increased PMo numbers and reduced stasis compared to single-agent therapies in SCD mice. Altogether, these data indicate that monocyte fates are regulated by the balance between two heme pathways, Nrf2-CSF-1 and IFN-I-CCL-2, and suggest that the CSF-1/CCL-2 ratio may present a diagnostic and therapeutic target in SCD.

Sickle cell disease (SCD) is characterized by a point mutation in the β globin molecule, causing the sickling of red blood cells, and leading to hemolytic anemia, pain, and end-organ damage. Hydroxyurea (HU) is a cornerstone of SCD patient treatment, while chronic transfusions (CT) are used as part of treatment for more severe SCD. Increases in aged neutrophils and inflammation have been linked to more severe SCD and contribute to vaso-occlusive crises. The current study was designed to test the hypothesis that HU reduces inflammation and aged neutrophils. We compared clinical characteristics, aged neutrophils, levels of select cytokines, chemokines, and cell adhesion molecules in the blood and the Shannon diversity index (SDI) and ratio of Firmicutes/Bacteroides (F:B) in stool samples from pediatric SCD patients treated with HU (n=40) versus CT (n=14). Patients in the HU group had significantly lower total and aged neutrophils ( <0.0001) compared to the CT group and also had lower levels of several chemokines including CXCL10 (IP-10), CCL2 (MCP-1) and CCL4 (MIP-1β) as well as IFN-γ and IL10. Conversely, HU was associated with higher levels of IL-1α, IL-6 and IL-8. There were no significant differences in cell adhesion markers or in markers of gut microbial dysbiosis between treatment groups. In a multivariable linear regression model, only being on CT was associated with increased number of aged neutrophils (p<0.001) whereas being on CT and having a lower SDI were associated with higher total neutrophil count. Lower numbers of total and aged neutrophils and lower levels of several cytokines and chemokines in the HU group highlight the drug's potential to modulate leukocyte activation and recruitment. These findings suggest that adding or maintaining HU therapy in SCD patients undergoing CT could potentially enhance immunologic regulation and warrants further study.

Vasculopathy is a hallmark of sickle cell disease ultimately resulting in chronic end organ damage. Leg ulcer is one of its sequelae, occurring in ~ 5–10% of adult sickle cell patients. The majority of leg ulcer publications to date have emanated from single center cohort studies. As such, there are limited studies on the geographic distribution of leg ulcers and associated risk factors worldwide. The Consortium for the Advancement of Sickle Cell Research (CASiRe) was formed to improve the understanding of the different phenotypes of sickle cell disease patients living in different geographic locations around the world (USA, UK, Italy, Ghana). This cross-sectional cohort sub-study of 659 sickle cell patients aimed to determine the geographic distribution and risk factors associated with leg ulcers. The prevalence of leg ulcers was 10.3% and was associated with older age, SS genotype, male gender, and Ghanaian origin. In fact, the highest prevalence (18.6%) was observed in Ghana. Albuminuria, proteinuria, increased markers of hemolysis (lower hemoglobin, higher total bilirubin), lower oxygen saturation, and lower body mass index were also associated with leg ulceration. Overall, our study identified a predominance of leg ulcers within male hemoglobin SS patients living in sub-Saharan Africa with renal dysfunction and increased hemolysis.

Background: Crizanlizumab is a novel inhibitor of P-selectin, a key player in multicellular adhesion and inflammatory signaling, that leads to vaso-occlusion in sickle cell disease (SCD). Objectives: The SOLACE-adults study evaluated the pharmacokinetics, pharmacodynamics (P-selectin inhibition), safety, and efficacy of crizanlizumab, with or without hydroxyurea/hydroxycarbamide, in patients with SCD. Design: Phase II, single-arm, multicenter study. Methods: Patients with SCD aged 16–70 years, with ⩾1 vaso-occlusive crisis (VOC) within 12 months before screening, received crizanlizumab 5.0 or 7.5 mg/kg intravenous infusion every 4 weeks; dose groups were enrolled sequentially. Results: Of 57 patients enrolled, 45 received crizanlizumab 5.0 mg/kg and 12 received 7.5 mg/kg for a median duration of 206 and 170 weeks, respectively. Crizanlizumab concentrations reached maximum levels after a 30-min infusion and remained steady for 6 h, without significant accumulation. P-selectin inhibition was nearly complete for both doses. The median (interquartile range) absolute change in the annualized rate of VOCs leading to healthcare visit from baseline was −0.79 (−3.04, 2.01) in the 5.0 mg/kg group and −0.98 (−1.11, −0.41) in the 7.5 mg/kg group. All patients experienced at least one adverse event (AE), with no apparent differences between the two doses in the frequency and severity of AEs. Grade ⩾3 AEs occurred in 60% of the 5.0 mg/kg group and 58% of the 7.5 mg/kg group. Two patients in the 5.0 mg/kg group and one in the 7.5 mg/kg group had severe crizanlizumab-related infusion-related reactions, which resolved with treatment. No patients developed antibodies against crizanlizumab. Conclusion: Crizanlizumab 5.0 and 7.5 mg/kg demonstrated a dose-proportional increase in exposure, sustained P-selectin inhibition, a tolerable safety profile, and a sustained reduction in VOCs leading to healthcare visit. This suggests that crizanlizumab is a useful treatment option for patients with SCD who have experienced VOCs. Trial Registration: NCT03264989 Plain language summary Understanding the effects of crizanlizumab in patients with sickle cell disease: Results from the SOLACE-adults study Crizanlizumab is a drug that inhibits P-selectin, which is involved in the inflammation and blockage of blood vessels that occurs in an inherited blood disorder called sickle cell disease (SCD). The SOLACE-adults study investigated the effects of crizanlizumab on the pharmacokinetics (how the drug moves through the body), pharmacodynamics (its effects on P-selectin), safety, and efficacy in patients with SCD. This was a Phase II study conducted at multiple centers, where all patients received crizanlizumab. Patients aged between 16 to 70 years who had SCD and experienced vaso-occlusive crises (VOCs, painful episodes caused by blocked blood vessels) within the year before the study were given crizanlizumab intravenously every 4 weeks at a dose of either 5.0 mg/kg or 7.5 mg/kg. A total of 57 patients enrolled in the study, of whom 45 received the 5.0 mg/kg dose and 12 received the 7.5 mg/kg dose. Crizanlizumab levels in the blood peaked 30 minutes after the infusion and remained steady for 6 hours. Both doses effectively inhibited P-selectin. The median reduction in the rate of vaso-occlusive crises leading to healthcare visits was -0.79 in the 5.0 mg/kg group and -0.98 in the 7.5 mg/kg group. All patients experienced adverse events, but there were no major differences between the two doses. Grade ⩾3 adverse events occurred in 60% of the 5.0 mg/kg group and 58% of the 7.5 mg/kg group. Some patients had severe reactions to the infusion, but these reactions resolved with treatment. None of the patients developed antibodies against crizanlizumab. In conclusion, crizanlizumab at both doses reached levels of exposure that caused sustained inhibition of P-selectin, had tolerable safety, and reduced VOCs requiring medical visits. This suggests that crizanlizumab is a beneficial treatment option for patients with SCD experiencing these painful crises.

Background Hydroxyurea (HU) is recommended as standard practice for youth with sickle cell disease (SCD). Yet, despite its efficacy, HU adherence in adolescents and young adults is often poor. Poor medication adherence increases disease burden, healthcare cost and widens health disparities. Adolescence is a critical time to improve adherence through improved chronic disease self-management. This study aims to test the efficacy of an intervention delivered to youth/parent dyads by community health workers (CHWs), augmented by tailored text messages on HU adherence (primary outcome). Secondary outcomes are intervention sustainability, youth health-related quality of life, self-management responsibility concordance, acute hospital use and self-reported disease symptoms. Methods Hydroxyurea Adherence for Personal Best in Sickle Cell Disease, “HABIT,” is a 12 month multi-center randomized controlled trial. One hundred four youth, 10 to 18 years of age prescribed HU who meet eligibility criteria, enrolled with their parent as dyads, will be randomized 1:1 to either the HABIT intervention or to usual clinical care plus education handouts. All subjects will complete clinic visits at months 0, 2, 4, 6 (efficacy component), 9 and 12 (sustainability component) for assessment of HbF biomarker, other hematologic parameters, and to complete questionnaires. In addition, dyads assigned to the HABIT intervention will work with CHWs to identify a daily habit (e.g., brushing teeth) on which to build a HU adherence habit. Tailored daily text message reminders to support the habit will be developed by the dyad in collaboration with the CHWs and sent to parent and youth. At the 6 month visit, the intervention will end and the sustainability portion of the trial will begin. All data analyses will be based on intention to treat with all randomized subjects included in the analyses. Discussion Prior retrospective studies demonstrate that a majority of adolescents are poorly adherent to HU. If efficacious, the HABIT intervention has the potential to improve the lives of youth with SCD. Trial registration Clinicaltrials.gov NCT03462511 . Registered March 6, 2018, last updated July 26, 2019.

Preclinical and clinical studies demonstrate the feasibility of treating β-thalassemia and Sickle Cell Disease (SCD) by lentiviral-mediated transfer of the human β-globin gene. However, previous studies have not addressed whether the ability of lentiviral vectors to increase hemoglobin synthesis might vary in different patients.We generated lentiviral vectors carrying the human β-globin gene with and without an ankyrin insulator and compared their ability to induce hemoglobin synthesis in vitro and in thalassemic mice. We found that insertion of an ankyrin insulator leads to higher, potentially therapeutic levels of human β-globin through a novel mechanism that links the rate of transcription of the transgenic β-globin mRNA during erythroid differentiation with polysomal binding and efficient translation, as reported here for the first time. We also established a preclinical assay to test the ability of this novel vector to synthesize adult hemoglobin in erythroid precursors and in CD34(+) cells isolated from patients affected by β-thalassemia and SCD. Among the thalassemic patients, we identified a subset of specimens in which hemoglobin production can be achieved using fewer copies of the vector integrated than in others. In SCD specimens the treatment with AnkT9W ameliorates erythropoiesis by increasing adult hemoglobin (Hb A) and concurrently reducing the sickling tetramer (Hb S).Our results suggest two major findings. First, we discovered that for the purpose of expressing the β-globin gene the ankyrin element is particularly suitable. Second, our analysis of a large group of specimens from β-thalassemic and SCD patients indicates that clinical trials could benefit from a simple test to predict the relationship between the number of vector copies integrated and the total amount of hemoglobin produced in the erythroid cells of prospective patients. This approach would provide vital information to select the best candidates for these clinical trials, before patients undergo myeloablation and bone marrow transplant.

Complications associated with sickle cell disease (SCD) that are highly impactful for patients but until recently have been less understood include priapism, nephropathy, and neurologic injury. We conducted a retrospective study using US administrative claims data from July 01, 2013 through March 31, 2020 to analyze incidence of these complications, SCD treatment patterns, and healthcare resource utilization (HCRU) and costs among 2524 pediatric and adult patients with SCD (mean [SD] age 43.4 [22.4] years). The most common treatments during follow‐up were short‐acting opioids (54.0% of patients), red blood cell transfusion (15.9%), and hydroxyurea (11.0%). SCD complications occurred frequently; in the overall population, the highest follow‐up incidences per 1000 person‐years were for acute kidney injury (53.1), chronic kidney disease (40.6), and stroke (39.0). Complications occurred across all age groups but increased in frequency with age; notably, acute kidney injury was 69.7 times more frequent among ages 65+ than ages 0–15 (p < 0.001). Follow‐up per‐patient‐per‐month HCRU also increased with age; however, all‐cause healthcare costs were similarly high for all age groups and were driven primarily by inpatient stays. Patients with SCD across the age spectrum have a high burden of complications with the use of current treatments, suggesting unmet needs for treatment management.