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Increased fetal hemoglobin (HbF) levels reduce the symptoms of sickle cell disease (SCD) and increase the lifespan of patients. Because curative strategies for bone marrow transplantation and gene therapy technologies remain unavailable to a large number of patients, the development of a safe and effective pharmacological therapy that increases HbF offers the greatest potential for disease intervention. Although hydroxyurea increases HbF, a substantial proportion of patients fail to demonstrate an adequate response. Pharmacological inhibitors of DNA methyltransferase (DNMT1) and lysine-specific demethylase 1A (LSD1), 2 epigenome-modifying enzymes associated with the multiprotein corepressor complex recruited to the repressed γ-globin gene, are powerful in vivo inducers of HbF. The hematological side effects of these inhibitors limit feasible clinical exposures. We evaluated whether administering these drugs in combination could reduce the dose and/or time of exposure to any single agent to minimize adverse effects, while achieving additive or synergistic increases in HbF. The DNMT1 inhibitor decitabine (0.5 mg/kg per day) and the LSD1 inhibitor RN-1 (0.25 mg/kg per day) administered in combination 2 days per week produced synergistic increases in F-cells, F-reticulocytes, and γ-globin messenger RNA in healthy baboons. Large increases in HbF and F-cells were observed in healthy, nonanemic, and anemic (phlebotomized) baboons. Combinatorial therapy targeting epigenome-modifying enzymes could thus be a useful strategy for producing larger increases in HbF to modify the clinical course of SCD., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Study Objective: To review five cases of severe adverse reactions after vaccination with the 23-valent pneumococcal polysaccharide vaccine (PPSV23) in pediatric and adolescent patients with sickle cell disease (SCD), and to evaluate the prevalence of adverse reactions to PPSV23 in patients with SCD by analyzing data from the Vaccine Adverse Event Reporting System (VAERS)., Design: Case series and retrospective analysis of data from the VAERS., Data Sources: Medical records from a tertiary care hospital and the VAERS database., Measurements and Main Results: Five cases of severe adverse reactions after vaccination with PPSV23 in pediatric and adolescent patients with SCD (aged 2-22 years) were reviewed. The adverse reactions occurred within 24 hours after immunization, and all five patients required medical attention. Analysis of data from the VAERS found that PPSV23 was the most commonly reported vaccine causing adverse events in patients with SCD, accounting for 62% of all vaccine-induced adverse events. This rate is significantly higher than the rate of adverse events related to PPSV23 in patients with human immunodeficiency virus (HIV) or asthma (62% vs 16%, p<0.0001). The reported number of adverse reactions in pediatric patients (< 18 years old) with SCD was 4 times higher than that reported in adult patients (18-39 years old) with SCD., Conclusion: The risk of developing severe adverse reactions to PPSV23 is greater in patients with SCD than in patients with HIV or asthma, and especially in pediatric and adolescent patients with SCD compared with their adult counterparts. Health care professionals should closely monitor for potential adverse events after PPSV23 vaccination or revaccination in patients with SCD, adhere to the recommended time interval between PCV13 and PPSV23 administration, and possibly consider avoiding simultaneous administration of other vaccines with PPSV23., (© 2015 Pharmacotherapy Publications, Inc.)

Selective drug delivery to hypoxic tumor niches remains a significant therapeutic challenge that calls for new conceptual approaches. Sickle red blood cells (SSRBCs) have shown an ability to target such hypoxic niches and induce tumoricidal effects when used together with exogenous pro-oxidants. Here we determine whether the delivery of a model therapeutic encapsulated in murine SSRBCs can be enhanced by ex vivo photosensitization under conditions that delay autohemolysis to a time that coincides with maximal localization of SSRBCs in a hypoxic tumor. Hyperspectral imaging of 4T1 carcinomas shows oxygen saturation levels <10% in a large fraction (commonly 50% or more) of the tumor. Using video microscopy of dorsal skin window chambers implanted with 4T1 tumors, we demonstrate that allogeneic SSRBCs, but not normal RBCs (nRBCs), selectively accumulate in hypoxic 4T1 tumors between 12 and 24h after systemic administration. We further show that ex vivo photo-oxidation can program SSRBCs to postpone hemolysis/release of a model therapeutic to a point that coincides with their maximum sequestration in hypoxic tumor microvessels. Under these conditions, drug-loaded photosensitized SSRBCs show a 3-4 fold greater drug delivery to tumors compared to non-photosensitized SSRBCs, drug-loaded photosensitized nRBCs, and free drug. These results demonstrate that photo-oxidized SSRBCs, but not photo-oxidized nRBCs, sequester and hemolyze in hypoxic tumors and release substantially more drug than photo-oxidized nRBCs and non-photo-oxidized SSRBCs. Photo-oxidation of drug-loaded SSRBCs thus appears to exploit the unique tumor targeting and carrier properties of SSRBCs to optimize drug delivery to hypoxic tumors. Such programmed and drug-loaded SSRBCs therefore represent a novel and useful tool for augmenting drug delivery to hypoxic solid tumors., (© 2013.)