Erythropoiesis Stimulating Agents (ESAS) in Supportive Care of Low-Risk Myelodysplastic Syndromes: Recamds Registry FINAL Results

Erythropoiesis stimulating agents (ESAs) are the frontline treatment in low-risk anemic MDS patients and an employment of this therapy in the earlier stage of the disease can delay the need for RBC transfusion, hypothetically by slowing the disease course. It's matter of debate whether the clinical response is a result of proliferation and maturation of the dysplastic clone or stimulation of residual normal erythropoiesis by ESAs. Macrocytosis is one of the cytological hallmarks of dyserithropoiesis in MDS: an analysis of the erythropoietic response to ESAs therapy in a cohort of anemic non trasfusion-dependent MDS patients, enrolled in a retrospective register, RECAMDS, subgroup of Italian register, was performed. 183 patients, treated with standard-dose ESAs, have been retrospectively analyzed. Data analysis was performed, according to IWG 2006 criteria, at the baseline, after 3 and 6 months of continuous treatment, with a subanalysis of the patients according to WHO and R-IPSS risk stratification. ESAs were started at mean Hb concentration of 9.31 g/dl, mean serum EPO concentration: 51 mU/L, after a mean time from diagnosis of 6 months (r.1-118). ORR was 83.6% (153/183), no difference among WHO and IPSS subgroups was found: 132/183 (72.1%) achieved response after 3 months of treatment, while other 21/183 (11.2%) after 6 months. 19 patients with stable disease (non-responders, according to IWG criteria), in which treatment was continued, achieved response after 9 months. In the macrocytic-responders group 83.2% exhibits again macrocytosis after 3 months, while 16.8% become normocytic. In the normocytic-responders group 89.8% exhibits again normocytosis, while 10.2% become macrocytic: in these patients, after 3 months, there was a contemporary worsening in neutropenia and thrombocytopenia, with transfusion-dependence, regarded as first signs of progression of disease. Non-responders were 30/183 (16.3%): in the macrocytic non-responders group 89% exhibit again macrocytosis after 3 months, while 11% become normocytic; in the normocytic group 76% exhibits again macrocytosis, while 24% become normocytic. These preliminary data can suggest that, in the majority of MDS patients responsive to ESAs, the increase of Hb concentration occurs mainly stimulating erythroid production in MDS clones; in the minority of patients probably it happens recruiting residual polyclonal erythropoiesis. It is interesting to note that stimulating effects of ESAs last even when the expression of dysplasia progresses. Figure 1 Figure 1. Disclosures Martinelli: Roche: Consultancy; Stemline Therapeutics: Consultancy; Abbvie: Consultancy; Jazz Pharmaceuticals: Consultancy; Celgene /BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Incyte: Consultancy; Daichii Sankyo: Consultancy; Astellas: Consultancy, Speakers Bureau.

Luspatercept Redistributes Body Iron to the Liver in Transfusion-Dependent-Thalassemia (TDT) during Erythropoietic Response

Introduction: Luspatercept inhibits select ligands of the TGF-β superfamily implicated in thalassemic erythropoiesis and promotes late-stage erythroid maturation (Suragani RN, et al. Nat Med 2014;20:408-414). This leads to greater red blood cell (RBC) output from thalassemic marrow and reduces transfusion dependence in TDT (Cappellini MD, et al. N Engl J Med 2020;382:1219-1231). The underlying mechanisms for this clinical outcome are not well understood in a syndrome involving significant iron overload and cyclical stimulation of erythropoiesis between transfusions. Here we report novel physiological and clinical insights from a BELIEVE trial (NCT02604433) biomarker analysis, which demonstrate that hepcidin and erythropoietic changes in TDT lead to iron redistribution from macrophages to hepatocytes on luspatercept. Methods: 336 TDT patients ≥ 18 years of age who took part in the BELIEVE study, a multicenter, randomized, double-blind, placebo-controlled phase 3 trial (Cappellini et al. 2020), were randomized 2:1 to receive luspatercept or placebo subcutaneously every 21 days for 48 weeks. This ethically approved study was conducted in accordance with the Declaration of Helsinki. Patients provided written informed consent. Transfusion iron loading rate (ILR) was calculated assuming 1 unit = 200 mg Fe. Liver iron content (LIC) was measured by R2 MRI and R2* MRI, and total body iron stores by Angelucci formula. Serum was assayed for ferritin (SF) nephelometrically (Covance lab), and hepcidin, erythroferrone (ERFE), growth differentiation factor (GDF)15, and transferrin receptor (sTfR1) by ELISA at Intertek (San Diego, CA). Median and interquartile ranges are shown; P value < 0.05 was deemed significant. Results: Within 48 weeks on luspatercept, transfusion iron loading fell by 1.6 g (8 RBC units, ILR difference −0.08 mg Fe/kg/d ± 0.07, range −0.4 to 0.2). Regardless of thalassemic genotype, SF fell by 269.3 ± 963.7 and earliest at 12 weeks by 103.6 ± 690.3 µg/L (both P < 0.0001), with no change on placebo, indicating reduced macrophage iron. However, despite unchanged chelation exposure, no reduction in LIC (5.7 to 6.7 mg/g dw) or calculated body iron stores (3.6 to 4.2 g, not significant) occurred on luspatercept, even though saved iron loading from transfusion was 44% (1.6 g/3.6 g) of baseline body iron stores. On luspatercept, but not placebo, hepcidin fell by 53%, while erythropoietin (EPO), ERFE, GDF15, sTfR1, and reticulocytes rose by 93%, 51%, 59%, 66%, and 112%, respectively (all P < 0.0001). 71% (120/169) patients with and 47% without (17/36) ILR reduction had negative SF trends (P < 0.0001). In patients with SF reduction on luspatercept, bilirubin and LDH rose 50% and 67% (P < 0.0001) indicating increased RBC hemolysis from residual (effective and ineffective) erythropoiesis. ILR change correlated with changes in EPO, hepcidin, sTfR1, and bilirubin, but not with changes in ERFE, GDF15, reticulocytes, or LDH (Figure A). Hepcidin reduction was related to LIC increase post splenectomy (Figure B), suggesting a role for the spleen in preventing hemolytic iron redistribution to the liver. Decrease in SF thus associates with erythroid iron incorporation (sTfR1), hence RBC production that reduces transfusion needs (falling ILR) but enhances hemolytic rerouting of iron to the liver. In a mixed-effect linear regression analysis, transfusion, LIC, baseline SF, time, and treatment predicted SF changes in a benchmark model. We found high baseline LIC lessens the SF outcome, and hepcidin, EPO, and bilirubin jointly explained 66% of the treatment effect of luspatercept on SF. Conclusions: Luspatercept-increased ERFE, likely as a result of increased production or higher frequency of late-stage erythroblasts, partially reduces hepcidin production. Lower hepcidin mobilizes iron stores to facilitate bulk hemoglobinization, erythropoietic response, and transfusion burden reduction. Luspatercept leads to SF reduction that marks hepcidin-dependent iron egress from macrophage compartment to plasma. This relocated iron, variably utilized by thalassemic erythron, refluxes back to plasma for hepatocyte and extrahepatic iron uptake, or as heme iron shunts into the liver through hemolytic pathways from intramarrow ineffective erythropoiesis or peripheral breakdown of newly made thalassemic RBC. Macrophage to hepatocyte iron redistribution in TDT appears to be a mechanism of luspatercept. Figure 1 Figure 1. Disclosures Garbowski: Imara: Consultancy; Vifor: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy. Ugidos: Bristol Myers Squibb: Current Employment. Risueño: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Suragani: Acceleron Pharma: Current Employment, Current equity holder in publicly-traded company. Shetty: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Vodala: BMS: Current Employment, Other: stock options. Thakurta: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Schwickart: BMS (Celgene): Current equity holder in publicly-traded company, Ended employment in the past 24 months, Other, Patents & Royalties; Exelixis: Current Employment, Current equity holder in publicly-traded company. Porter: Celgene (BMS): Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Vifor: Honoraria, Membership on an entity's Board of Directors or advisory committees; Silence Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Honoraria; Protagonism: Honoraria; La Jolla Pharmaceuticals: Honoraria; bluebird bio, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.

Novel Fluorescent Timer Tool Enables Characterization of Erythropoietic Differentiation Based on Differential Cell Cycling Speeds

Erythropoietic proliferation and differentiation are coordinated and regulated by a complex compendium of molecular components and networks. Understanding the underlying mechanisms and the dependence of erythroid maturation on cell-cycle behavior can provide a detailed insight into normal and ineffective erythropoiesis. The dynamic cell cycle speed of erythroid progenitors reflects the erythron's response to external stimuli, such as severe anemia or bleeding. Aberrant cell cycle speed also defines pathologic conditions, such as the inability to compensate for anemia in diseases of ineffective erythropoiesis like hemolysis or thalassemia. Current methods to resolve cell cycle length heterogeneity at a single-cell level in real-time present with limitations, including cellular toxicity, insufficient intensity, and dilution over subsequent cell divisions. We utilized a unique live-cell reporter of cell cycle speed using a histone H2B-FT fusion protein containing the color-changing Fluorescent Timer (FT) protein. The FT protein emits blue fluorescence when newly synthesized and matures into a stable red fluorescent protein over 1.2 hours. The fusion protein thus distinguishes faster cycling cells from slower-cycling ones based on the intracellular ratio between blue and red fluorescence. Knock-in mice expressing H2B-FT from a universally active locus under the control of a dox inducible promoter were previously generated and characterized. We successfully characterized the stress erythropoietic response of the spleen and bone marrow (BM) after inducing hemolytic anemia by phenylhydrazine (PHZ) administration in these transgenic mice. Flow cytometric investigation of successive stages of erythroblasts revealed that all stages of erythroblasts maintain rapid cell division after the hemolytic insult (****p<0.0001, Mann-Whitney test) and not only early progenitors, as previously thought. We also observed that stress erythropoiesis in the spleen is stimulated almost immediately after hemolysis. Most importantly, we observed that the last nucleated cell stage, orthochromatic erythroblasts, stop dividing much earlier than normal, allowing them to terminally differentiate into reticulocytes much faster to alleviate the anemia. Blue-red (BR) profiles of the different erythroblasts from the PHZ-treated animals showed a marked distribution into fast-cycling (high blue fluorescence) and slow-cycling (high red fluorescence) subpopulations. Histograms of normalized BR ratios revealed significantly differentially cycling subpopulations in the polychromatic erythroblasts from spleen and orthochromatic erythroblasts from BM under stress. Mass spectrometric analysis of the differentially cycling subpopulations sorted from the respective erythroblasts shows upregulation of genes encoding cell cycle related and phospho-proteins. We are currently performing comparative analyses with openly available proteomic data. With the Erythropoietin (Epo) model for inducing stress erythropoiesis, we do find a modest increase in blue-red ratios for each of the erythroblast populations in Epo-treated timer mice as compared to the PHZ model. A recent study on steroid resistance in DBA reported that dexamethasone (dex) treatment of peripheral blood progenitors caused the specific upregulation of p57Kip2 leading to higher expansion and accelerated erythroid differentiation. We will utilize in vitro human CD34+ primary cell culture to assess the erythropoietic response to known treatments of anemia of chronic kidney disease and Diamond-Blackfan Anemia, like Epo and dex, respectively. These findings shed new light on the normal response to external stress, underscoring the possibility of precise quantification of cell cycle speed in animal models of anemia. We highlight the use of a sophisticated fluorescent system that can help elucidate the role of cell cycle speed in stress hematopoiesis, and determine the mechanistic pathways acting at single-cell or population level. Further phosphoproteomic investigation can lead to identification of discrete molecular targets regulating erythroid cell proliferation and differentiation with potential therapeutic implications. The tool can aid in answering important questions delineating cell cycle dynamics as the cause or consequence of erythroid differentiation in normal and pathophysiological conditions. Disclosures No relevant conflicts of interest to declare.

Morphological and Transcriptional Changes in Human Bone Marrow During Natural Plasmodium vivax Malaria Infections

Background The presence of Plasmodium vivax malaria parasites in the human bone marrow (BM) is still controversial. However, recent data from a clinical case and experimental infections in splenectomized nonhuman primates unequivocally demonstrated the presence of parasites in this tissue. Methods In the current study, we analyzed BM aspirates of 7 patients during the acute attack and 42 days after drug treatment. RNA extracted from CD71+ cell suspensions was used for sequencing and transcriptomic analysis. Results We demonstrated the presence of parasites in all patients during acute infections. To provide further insights, we purified CD71+ BM cells and demonstrated dyserythropoiesis and inefficient erythropoiesis in all patients. In addition, RNA sequencing from 3 patients showed that genes related to erythroid maturation were down-regulated during acute infections, whereas immune response genes were up-regulated. Conclusions This study thus shows that during P. vivax infections, parasites are always present in the BM and that such infections induced dyserythropoiesis and ineffective erythropoiesis. Moreover, infections induce transcriptional changes associated with such altered erythropoietic response, thus highlighting the importance of this hidden niche during natural infections.

Iron supplementation for lambs experimentally infected by Haemonchus contortus: response to anemia and iron store in the bone marrow

ABSTRACT: To evaluate the effect of supplementation of iron dextran on blood variables and iron metabolism in lambs experimentally infected by Haemonchus contortus, four experimental groups were used: uninfected and non-supplemented animals (GI); infected animals supplemented with iron (GII); uninfected animals supplemented with iron (GIII); and infected non-supplemented animals (GIV). Groups II and IV received 10,000 larvae (L3) of Haemonchus contortus, and groups II and III received three doses of iron dextran (20mg/kg) intramuscularly with seven days of interval. Blood and faeces samples were collected on days 10 (D10), 17 (D17), 24 (D24), and 31 (D31), in order to determine red blood cell counts, iron metabolism, and EPG. Infected animals developed anemia from D24 and anemia was more severe on D31. Animals from GII had higher hematocrit and hemoglobin concentration compared to animals of GIV on D31. Iron stores in the bone marrow were higher in GII and GIII compared to GI and GIV. The GIV showed lower seric levels of iron on D24 compared to the other groups. The iron supplementation reduces the severity of the anemia caused by infection with Haemonchus contortus in lambs, improving erythropoietic response after blood loss.

Fyn is Involved in Erythropoietin Signaling Pathway and Interfaces Oxidation to Regulate Erythropoiesis

ABSTRACTErythropoiesis is a complex multistep process responsible of the production of circulating mature erythrocytes and involved the production of reactive oxygen species (ROS) during erythroid differentiation. Here, we document that Fyn, a Src-family-kinase, participates in erythropoietin (EPO) signaling pathway, by the reducing extent of Tyr-phosphorylation of EPO-R and by decreasing STAT5 activity. The importance of Fyn in EPO cascade is also supported by the increased sensitivity of Fyn−/−mice to stress erythropoiesis. Fyn−/−mouse erythroblasts adapt to the induced stress by the activation of the redox-related-transcription-factor Nrf2. However, the absence of the Nrf2 physiologic repressor Fyn resulted in the persistent activation of Nrf2 and accumulation of non-functional proteins. This is paralleled by ROS induced over-activation of Jak2-Akt-mTOR pathway and repression of autophagy and perturbation of lysosomal-clearance during Fyn−/−reticulocyte maturation. Treatment with Rapamycin, a mTOR inhibitor and autophagy activator, ameliorates Fyn−/−mouse baseline erythropoiesis and restored the erythropoietic response to phenylhydrazine. Taken together these findings have enabled to identify the novel multimodal action of Fyn in the developmental program of erythropoiesis.

Inhibition ofex vivoerythropoiesis by secreted and haemozoin-associatedPlasmodium falciparumproducts

It has been estimated that up to a third of global malaria deaths may be attributable to malarial anaemia, with children and pregnant women being those most severely affected. An inefficient erythropoietic response to the destruction of both infected and uninfected erythrocytes in infections withPlasmodiumspp. contributes significantly to the development and persistence of such anaemia. The underlying mechanisms, which could involve both direct inhibition of erythropoiesis by parasite-derived factors and indirect inhibition as a result of modulation of the immune response, remain poorly understood. We found parasite-derived factors in conditioned medium (CM) of blood-stagePlasmodium falciparumand crude isolates of parasite haemozoin directly to inhibit erythropoiesis in anex vivomodel based on peripheral blood haematopoietic stem cells. Erythropoiesis-inhibiting activity was detected in a fraction of CM that was sensitive to heat inactivation and protease digestion. Erythropoiesis was also inhibited by crude parasite haemozoin but not by detergent-treated, heat-inactivated or protease-digested haemozoin. These results suggest that the erythropoiesis-inhibiting activity in both cases is mediated by proteins or protein-containing biomolecules and may offer new leads to the treatment of malarial anaemia.