Complement C3dg-mediated erythrophagocytosis: implications for paroxysmal nocturnal hemoglobinuria.

The clinical management of paroxysmal nocturnal hemoglobinuria (PNH), a rare but life-threatening hematologic disease, has fundamentally improved with the introduction of a therapeutic that prevents complement-mediated intravascular hemolysis. However, a considerable fraction of PNH patients show insufficient treatment response and remain transfusion dependent. Because the current treatment only prevents C5-induced lysis but not upstream C3 activation, it has been speculated that ongoing opsonization with C3 fragments leads to recognition and phagocytosis of PNH erythrocytes by immune cells. Here, for the first time, we provide experimental evidence for such extravascular hemolysis and demonstrate that PNH erythrocytes from anti-C5-treated patients are phagocytosed by activated monocytes in vitro. Importantly, we show that this uptake can be mediated by the end-stage opsonin C3dg, which is not traditionally considered a phagocytic marker, via interaction with complement receptor 3 (CR3). Interaction studies confirmed that C3dg itself can act as a ligand for the binding domain of CR3. The degree of C3dg-mediated erythrophagocytosis in samples from different PNH patients correlated well with the individual level of C3dg opsonization. This finding may guide future treatment options for PNH but also has potential implications for the description and management of other complement-mediated diseases.

Peptide inhibitors of C3 activation as a novel strategy of complement inhibition for the treatment of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated intravascular hemolysis due to the lack of CD55 and CD59 on affected erythrocytes. The anti-C5 antibody eculizumab has proven clinically effective, but uncontrolled C3 activation due to CD55 absence may result in opsonization of erythrocytes, possibly leading to clinically meaningful extravascular hemolysis. We investigated the effect of the peptidic C3 inhibitor, compstatin Cp40, and its long-acting form (polyethylene glycol [PEG]-Cp40) on hemolysis and opsonization of PNH erythrocytes in an established in vitro system. Both compounds demonstrated dose-dependent inhibition of hemolysis with IC50 ∼4 µM and full inhibition at 6 µM. Protective levels of either Cp40 or PEG-Cp40 also efficiently prevented deposition of C3 fragments on PNH erythrocytes. We further explored the potential of both inhibitors for systemic administration and performed pharmacokinetic evaluation in nonhuman primates. A single intravenous injection of PEG-Cp40 resulted in a prolonged elimination half-life of >5 days but may potentially affect the plasma levels of C3. Despite faster elimination kinetics, saturating inhibitor concentration could be reached with unmodified Cp40 through repetitive subcutaneous administration. In conclusion, peptide inhibitors of C3 activation effectively prevent hemolysis and C3 opsonization of PNH erythrocytes, and are excellent, and potentially cost-effective, candidates for further clinical investigation.

Urokinase receptor and CXCR4 are regulated by common microRNAs in leukaemia cells.

The urokinase-type plasminogen activator (uPA) receptor (uPAR) focuses uPA proteolytic activity on the cell membrane, promoting localized degradation of extracellular matrix (ECM), and binds vitronectin (VN), mediating cell adhesion to the ECM. uPAR-bound uPA and VN induce proteolysis-independent intracellular signalling, regulating cell adhesion, migration, survival and proliferation. uPAR cross-talks with CXCR4, the receptor for the stroma-derived factor 1 chemokine. CXCR4 is crucial in the trafficking of hematopoietic stem cells from/to the bone marrow, which involves also uPAR. Both uPAR and CXCR4 are expressed in acute myeloid leukaemia (AML), with a lower expression in undifferentiated and myeloid subsets, and higher expression in myelomonocytic and promyelocytic subsets. We hypothesized a microRNA (miR)-mediated co-regulation of uPAR and CXCR4 expression, which could allow their cross-talk at the cell surface. We identified three miRs, miR-146a, miR-335 and miR-622, regulating the expression of both uPAR and CXCR4 in AML cell lines. Indeed, these miRs directly target the 3'untranslated region of both uPAR- and CXCR4-mRNAs; accordingly, uPAR/CXCR4 expression is reduced by their overexpression in AML cells and increased by their specific inhibitors. Overexpression of all three miRs impairs migration, invasion and proliferation of myelomonocytic cells. Interestingly, we observed an inverse relationship between uPAR/CXCR4 expression and miR-146a and miR-335 levels in AML blasts, suggesting their possible role in the regulation of uPAR/CXCR4 expression also in vivo.

Polymorphism of the complement receptor 1 gene correlates with the hematologic response to eculizumab in patients with paroxysmal nocturnal hemoglobinuria.

Complement blockade by eculizumab is clinically effective in hemolytic paroxysmal nocturnal hemoglobinuria. However, the response is variable and some patients remain dependent on red blood cell transfusions. In 72 patients with hemolytic paroxysmal nocturnal hemoglobinuria on eculizumab we tested the hypothesis that response may depend on genetic polymorphisms of complement-related genes. We found no correlation between the complement component C3 genotypes and the need for blood transfusions. On the other hand, we found a significant correlation with the HindIII polymorphism of a complement regulatory gene, the complement receptor 1 (CR1) gene. At this locus two co-dominant alleles are known, of which H (common) is associated with high expression, whereas L (rare) is associated with low expression of CR1 on red blood cells. Patients who still needed blood transfusion on eculizumab accounted for 18% of the H/H homozygotes, 33% of the H/L heterozygotes and 68% of the L/L homozygotes (P=0.016). Thus, patients with paroxysmal nocturnal hemoglobinuria who have the L/L genotype are seven times more likely to be sub-optimal responders to eculizumab. Both in vitro and in vivo we found that the CR1 HindIII genotype correlates with the abundance of paroxysmal nocturnal hemoglobinuria red cells that have bound C3, and with the kinetics of C3 binding. These results are consistent with the notion that by affecting C3 binding the CR1 genotype influences the response to eculizumab treatment, and this emerges as a novel example of pharmacogenetics.

Modeling Inflammatory Bowel Disease by Intestinal Organoids.

Inflammatory bowel disease (IBD) is a chronic and relapsing disease caused by a dysregulated immune response to host intestinal microbiota that occurs in genetically predisposed individuals. IBD encompasses two major clinical entities: ulcerative colitis (UC), limited to the colonic mucosa, and Crohn's disease (CD), which might affect any segment of the gastrointestinal tract. Despite the prevalence of IBD increasing worldwide, therapy remains suboptimal, largely because of the variability of causative mechanisms, raising the need to develop individualized therapeutic approaches targeted to each individual patient. In this context, patients-derived intestinal organoids represent an effective tool for advancing our understanding of IBD's pathogenesis. Organoid 3D culture systems offer a unique model for dissecting epithelial mechanisms involved IBDs and testing individualized therapy, although the lack of a functional immune system and a microbiota, two driving components of the IBD pathogenesis, represent a major barrier to their exploitation in clinical medicine. In this review, we have examined how to improve the translational utility of intestinal organoids in IBD and how co-cultures of 3D or 2D organoids and immune cells and/or intestinal microbiota might help to overcome these limitations.

Environmental quality improvement of a mariculture plant after its conversion into a multi-trophic system.

Integrated Multitrophic Aquaculture (IMTA) seems to be one of the best solutions for sustainable aquaculture. Within the Remedia LIFE Project, an experimental IMTA plant was put in place in the Mar Grande of Taranto (Mediterranean Sea, Southern Italy). The polyculture of several bioremediating organisms, such as mussels, tubeworms, sponges, and seaweeds, was combined with a coastal cage fish farm, in order to remove organic and inorganic wastes coming from the fish's metabolism. To verify the effectiveness of the system, the ex ante measurement of chemical-physical variables, trophic status, microbial contamination, and zoobenthos community health was compared with the results of the same measurement performed one year and two years after the implementation of the experimental IMTA plant. The results were encouraging, since a reduction in total nitrogen concentration in the seawater (from 43.4 ± 8.9 to 5.6 ± 3.7 µM/l), a reduction in microbial pollution indicators in the seawater (total coliforms: from 280 ± 18 MPN/100 mL to 0; E. coli: from 33 ± 1.3 MPN/100 mL to 0) and in the sediments (total coliforms: from 230 ± 6.2 MPN/100 g to 170 ± 9; E. coli: from 40 ± 9.4 MPN/100 g to 0), an enhancement of the trophic status (TRIX: from 4.45 ± 1.29 to 3.84 ± 0.18), and an increase in the zoobenthic quality indices and biodiversity were recorded (AMBI: from 4.8 to 2.4; M-AMBI: from 0.14 to 0.7). These results prove that the Remedia LIFE project's purpose was achieved. The selected bioremediators worked synergistically, improving water and sediments quality within the fish farm area. Moreover, bioremediating organisms increased their weight as a result of wastes uptake, producing, as co-products, large amounts of additional biomass. This could be commercially exploited, thus being an added value of the IMTA plant. Based on our findings, the promotion of eco-friendly practices to ameliorate ecosystem health should be encouraged.

Defective Bile Acid Signaling Promotes Vascular Dysfunction, Supporting a Role for G-Protein Bile Acid Receptor 1/Farnesoid X Receptor Agonism and Statins in the Treatment of Nonalcoholic Fatty Liver Disease.

BACKGROUND: Patients with nonalcoholic fatty liver disease are at increased risk to develop atherosclerotic cardiovascular diseases. FXR and GPBAR1 are 2 bile acid-activated receptors exploited in the treatment of nonalcoholic fatty liver disease: whether dual GPBAR1/FXR agonists synergize with statins in the treatment of the liver and cardiovascular components of nonalcoholic fatty liver disease is unknown. METHODS AND RESULTS: Investigations of human aortic samples obtained from patients who underwent surgery for aortic aneurysms and Gpbar1-/-, Fxr-/-, and dual Gpbar1-/-Fxr-/- mice demonstrated that GPBAR1 and FXR are expressed in the aortic wall and regulate endothelial cell/macrophage interactions. The expression of GPBAR1 in the human endothelium correlated with the expression of inflammatory biomarkers. Mice lacking Fxr and Gpbar1-/-/Fxr-/- display hypotension and aortic inflammation, along with altered intestinal permeability that deteriorates with age, and severe dysbiosis, along with dysregulated bile acid synthesis. Vasomotor activities of aortic rings were altered by Gpbar1 and Fxr gene ablation. In apolipoprotein E-/- and wild-type mice, BAR502, a dual GPBAR1/FXR agonist, alone or in combination with atorvastatin, reduced cholesterol and low-density lipoprotein plasma levels, mitigated the development of liver steatosis and aortic plaque formation, and shifted the polarization of circulating leukocytes toward an anti-inflammatory phenotype. BAR502/atorvastatin reversed intestinal dysbiosis and dysregulated bile acid synthesis, promoting a shift of bile acid pool composition toward FXR antagonists and GPBAR1 agonists. CONCLUSIONS: FXR and GPBAR1 maintain intestinal, liver, and cardiovascular homeostasis, and their therapeutic targeting with a dual GPBAR1/FXR ligand and atorvastatin holds potential in the treatment of liver and cardiovascular components of nonalcoholic fatty liver disease.

Discovery of BAR502, as potent steroidal antagonist of leukemia inhibitory factor receptor for the treatment of pancreatic adenocarcinoma.

Introduction: The leukemia inhibitory factor (LIF), is a cytokine belonging to IL-6 family, whose overexpression correlate with poor prognosis in cancer patients, including pancreatic ductal adenocarcinoma (PDAC). LIF signaling is mediate by its binding to the heterodimeric LIF receptor (LIFR) complex formed by the LIFR receptor and Gp130, leading to JAK1/STAT3 activation. Bile acids are steroid that modulates the expression/activity of membrane and nuclear receptors, including the Farnesoid-X-Receptor (FXR) and G Protein Bile Acid Activated Receptor (GPBAR1). Methods: Herein we have investigated whether ligands to FXR and GPBAR1 modulate LIF/LIFR pathway in PDAC cells and whether these receptors are expressed in human neoplastic tissues. Results: The transcriptome analysis of a cohort of PDCA patients revealed that expression of LIF and LIFR is increased in the neoplastic tissue in comparison to paired non-neoplastic tissues. By in vitro assay we found that both primary and secondary bile acids exert a weak antagonistic effect on LIF/LIFR signaling. In contrast, BAR502 a non-bile acid steroidal dual FXR and GPBAR1 ligand, potently inhibits binding of LIF to LIFR with an IC50 of 3.8 µM. Discussion: BAR502 reverses the pattern LIF-induced in a FXR and GPBAR1 independent manner, suggesting a potential role for BAR502 in the treatment of LIFR overexpressing-PDAC.

Activation of GPBAR1 attenuates vascular inflammation and atherosclerosis in a mouse model of NAFLD-related cardiovascular disease.

While patients with nonalcoholic fatty liver disease (NAFLD) are at increased risk to develop clinically meaningful cardiovascular diseases (CVD), there are no approved drug designed to target the liver and CVD component of NAFLD. GPBAR1, also known as TGR5, is a G protein coupled receptor for secondary bile acids. In this study we have investigated the effect of GPBAR1 activation by BAR501, a selective GPBAR1 agonist, in Apolipoprotein E deficient (ApoE-/-) mice fed a high fat diet and fructose (Western diet), a validated model of NAFLD-associated atherosclerosis. Using aortic samples from patients who underwent surgery for abdominal aneurism, and ex vivo experiments with endothelial cells and human macrophages, we were able to co-localize the expression of GPBAR1 in CD14+ and PECAM1+ cells. Similar findings were observed in the aortic plaques from ApoE-/- mice. Treating ApoE-/- mice with BAR501, 30 mg/kg for 14 weeks, attenuated the body weight gain while ameliorated the insulin sensitivity by increasing the plasma concentrations of GLP-1 and FGF15. Activation of GPBAR1 reduced the aorta thickness and severity of atherosclerotic lesions and decreased the amount of plaques macrophages. Treating ApoE-/- mice reshaped the aortic transcriptome promoting the expression of anti-inflammatory genes, including IL-10, as also confirmed by tSNE analysis of spleen-derived macrophages. Feeding ApoE-/- mice with BAR501 redirected the bile acid synthesis and the composition of the intestinal microbiota. In conclusion, GPBAR1 agonism attenuates systemic inflammation and improve metabolic profile in a genetic/dietetic model of atherosclerosis. BAR501 might be of utility in the treatment for NAFLD-related CVD.

Immunomodulatory functions of FXR.

The Farnesoid-x-receptor (FXR) is a bile acids sensor activated in humans by primary bile acids. FXR is mostly expressed in liver, intestine and adrenal glands but also by cells of innate immunity, including macrophages, liver resident macrophages, the Kupffer cells, natural killer cells and dendritic cells. In normal physiology and clinical disorders, cells of innate immunity mediate communications between liver, intestine and adipose tissues. In addition to FXR, the G protein coupled receptor (GPBAR1), that is mainly activated by secondary bile acids, whose expression largely overlaps FXR, modulates chemical communications from the intestinal microbiota and the host's immune system, integrating epithelial cells and immune cells in the entero-hepatic system, providing a mechanism for development of a tolerogenic state toward the intestinal microbiota. Disruption of FXR results in generalized inflammation and disrupted bile acids metabolism. While FXR agonism in preclinical models provides counter-regulatory signals that attenuate inflammation-driven immune dysfunction in a variety of liver and intestinal disease models, the clinical relevance of these mechanisms in the setting of FXR-related disorders remain poorly defined.

An Integrated Monitoring Approach to the Evaluation of the Environmental Impact of an Inshore Mariculture Plant (Mar Grande of Taranto, Ionian Sea).

The results of an ex-ante survey aiming to assess the impact of a fish farm in the Mar Grande of Taranto (southern Italy, Mediterranean Sea) on the surrounding environment are reported. There, the implementation of an innovative IMTA plant was planned, with the goals of environment bioremediation and commercially exploitable biomass production. Analyses were conducted in February and July 2018. Both seawater and sediments were sampled at the four corners of the fish farm to detect the existing biological and physico-chemical features. The investigation was performed to identify the best area of the farming plant for positioning the bioremediating system, but also to obtain a data baseline, to compare to the environmental status after the bioremediating action. Data were also analyzed by canonical analysis of principal coordinates (CAP). All the measurements, in particular, microbiology and macrobenthic community characterization using AZTI's Marine Biotic Index (AMBI) and the Multivariate-AMBI (M-AMBI) indices, suggest that the effect of fish farm waste was concentrated and limited to a small portion of the investigated area in relation to the direction of the main current. A site named A3, which was found to be the most impacted by the aquaculture activities, especially during the summer season, was chosen to place the bioremediation system.

Complement fraction 3 binding on erythrocytes as additional mechanism of disease in paroxysmal nocturnal hemoglobinuria patients treated by eculizumab.

In paroxysmal nocturnal hemoglobinuria (PNH) hemolytic anemia is due mainly to deficiency of the complement regulator CD59 on the surface of red blood cells (RBCs). Eculizumab, an antibody that targets complement fraction 5 (C5), has proven highly effective in abolishing complement-mediated intravascular hemolysis in PNH; however, the hematologic benefit varies considerably among patients. In the aim to understand the basis for this variable response, we have investigated by flow cytometry the binding of complement fraction 3 (C3) on RBCs from PNH patients before and during eculizumab treatment. There was no evidence of C3 on RBCs of untreated PNH patients; by contrast, in all patients on eculizumab (n = 41) a substantial fraction of RBCs had C3 bound on their surface, and this was entirely restricted to RBCs with the PNH phenotype (CD59(-)). The proportion of C3(+) RBCs correlated significantly with the reticulocyte count and with the hematologic response to eculizumab. In 3 patients in whom (51)Cr labeling of RBCs was carried out while on eculizumab, we have demonstrated reduced RBC half-life in vivo, with excess (51)Cr uptake in spleen and in liver. Binding of C3 by PNH RBCs may constitute an additional disease mechanism in PNH, strongly enhanced by eculizumab treatment and producing a variable degree of extravascular hemolysis.

The identification of farnesoid X receptor modulators as treatment options for nonalcoholic fatty liver disease.

INTRODUCTION: The farnesoid-x-receptor (FXR) is a ubiquitously expressed nuclear receptor selectively activated by primary bile acids. AREA COVERED: FXR is a validated pharmacological target. Herein, the authors review preclinical and clinical data supporting the development of FXR agonists in the treatment of nonalcoholic fatty liver disease. EXPERT OPINION: Development of systemic FXR agonists to treat the metabolic liver disease has been proven challenging because the side effects associated with these agents including increased levels of cholesterol and LDL-c and reduced HDL-c raising concerns over their long-term cardiovascular safety. Additionally, pruritus has emerged as a common, although poorly explained, dose-related side effect with all FXR ligands, but is especially common with OCA. FXR agonists that are currently undergoing phase 2/3 trials are cilofexor, tropifexor, nidufexor and MET409. Some of these agents are currently being developed as combination therapies with other agents including cenicriviroc, a CCR2/CCR5 inhibitor, or firsocostat an acetyl CoA carboxylase inhibitor. Additional investigations are needed to evaluate the beneficial effects of combination of these agents with statins. It is expected that in the coming years, FXR agonists will be developed as a combination therapy to minimize side effects and increase likelihood of success by targeting different metabolic pathways.

Bile acid-activated receptors and the regulation of macrophages function in metabolic disorders.

Bile acids are produced in the liver by the cholesterol breakdown and further metabolized by the intestinal microbiota to generate a group of chemically heterogeneous steroids that bind and activate a family of cells surface and nuclear receptors, collectively known as the bile acid-activated receptors (BARs). The two best characterized members of this family are the farnesoid-x-receptor (FXR) and G protein Bile Acid Receptor (GPBAR1). Both receptors are expressed by cells of innate immunity including liver-resident and intestinal-resident macrophages and monocytes-derived macrophages. Because FXR and GPBAR1 knockout mice are biased toward a pro-inflammatory phenotype, it appears the both receptors might have a role in the development and maintenance of a tolerogenic phenotype. FXR and GPBAR1 ligands have been proven effective in the treatment in inflammatory and metabolic disorders and ligands for these receptors are currently under development for the treatment of non-alcoholic steato-hepatitis and diabetes.

Opposite effects of the FXR agonist obeticholic acid on Mafg and Nrf2 mediate the development of acute liver injury in rodent models of cholestasis.

The farnesoid-X-receptor (FXR) is validated target in the cholestatic disorders treatment. Obeticholic acid (OCA), the first in class of FXR agonist approved for clinical use, causes side effects including acute liver decompensation when administered to cirrhotic patients with primary biliary cholangitis at higher than recommended doses. The V-Maf avian-musculoaponeurotic-fibrosarcoma-oncogene-homolog-G (Mafg) and nuclear factor-erythroid-2-related-factor-2 (Nrf2) mediates some of the downstream effects of FXR. In the present study we have investigated the role of FXR/MafG/NRF2 pathway in the development of liver toxicity caused by OCA in rodent models of cholestasis. Cholestasis was induced by bile duct ligation (BDL) or administration of α-naphtyl-isothiocyanate (ANIT) to male Wistar rats and FXR-/- and FXR+/+ mice. Treating BDL and ANIT rats with OCA exacerbated the severity of cholestasis, hepatocytes injury and severely downregulated the expression of basolateral transporters. In mice, genetic ablation FXR or its pharmacological inhibition by 3-(naphthalen-2-yl)-5-(piperidin-4-yl)-1,2,4-oxadiazole rescued from negative regulation of MRP4 and protected against liver injury caused by ANIT. By RNAseq analysis we found that FXR antagonism effectively reversed the transcription of over 2100 genes modulated by OCA/ANIT treatment, including Mafg and Nrf2 and their target genes Cyp7a1, Cyp8b1, Mat1a, Mat2a, Gss. Genetic and pharmacological Mafg inhibition by liver delivery of siRNA antisense or S-adenosylmethionine effectively rescued from damage caused by ANIT/OCA. In contrast, Nrf2 induction by sulforaphane was protective. CONCLUSIONS: Liver injury caused by FXR agonism in cholestasis is FXR-dependent and is reversed by FXR and Mafg antagonism or Nrf2 induction.

[Preliminary experience on the application of metallic stents for treatment of colorectal malignant stenosis]. / Esperienza preliminare nell'applicazione degli stent metallici autoespandibili per il trattamento delle stenosi maligne colo-rettali.

OBJECTIVE: Application of SEMS in treating colorectal obstruction caused by both intrinsic and extrinsic tumours. METHODS: From December 2007 to February 2008 two patient underwent colorectal stenting. The first patient was affected by sigma neoplasia with multiple lung and liver metastases; the second one had a distal colonic obstruction caused by pelvic relapse of endometrial adenocarcinoma. RESULTS: In both patients successful decompression, defined as complete relief of bowel obstruction as judged by clinical symptoms and radiographic observation, was achieved. The first patient died 1 month later for disease progression after the I cycle with Capecitabine. The second patient is undergoing the II cycle with Adriamicina and Cisplatino. DISCUSSION: In our experience no precocious or posthumous complications were observed and we evaluated that SEMSs are useful in both intrinsic and extrinsic colorectal malignancies. CONCLUSIONS: SEMSs allow a rapid decompression, reduce the number of emergency surgical procedures--and also the need for stomas--in poor general condition patients, achieving a better quality of life for patient with a short estimated life and a one-stage elective surgery for patient with resectable disease.

Divergent Effectiveness of Multispecies Probiotic Preparations on Intestinal Microbiota Structure Depends on Metabolic Properties.

A growing body of evidence suggests that probiotic functionality is not accurately predicted by their taxonomy. Here, we have set up a study to investigate the effectiveness of two probiotic formulations containing a blend of seven bacterial species in modulating intestinal inflammation in two rodent models of colitis, induced by treating mice with 2,4,6-Trinitrobenzenesulfonic acid (TNBS) or dextran sodium sulfate (DSS). Despite the taxonomy of the bacterial species in the two probiotic formulations being similar, only one preparation (Blend 2-Vivomixx) effectively attenuated the development of colitis in both models. In the TNBS model of colitis, Blend 2 reduced the expression of pro-inflammatory genes while increasing the production of anti-inflammatory cytokines, promoting the expansion M2 macrophages and the formation of IL-10-producing Treg cells in the colon's lamina propria. In the DSS model of colitis, disease attenuation and Treg formation was observed only in mice administered with Blend 2, and this effect was associated with intestinal microbiota remodeling and increased formation of lactate, butyrate, and propionate. None of these effects were observed in mice administered with Blend 1 (VSL#3). In summary, we have shown that two probiotic mixtures obtained by combining taxonomically similar species produced with different manufacturing methods exert divergent effects in mouse models of colitis.

Eltrombopag for post-transplant cytopenias due to poor graft function.

Persistent cytopenia due to poor graft function (PoGF) is a relatively common complication which may affect up to 20% of patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Treatment options for PoGF remain limited, and reinfusion of additional HSC is often the only way to rescue hematopoiesis. Here we describe a retrospective single-center experience with the thrombopoietin-mimetic agent eltrombopag for the treatment of PoGF. Thirteen patients have received eltrombopag for either PoGF (n = 12) or primary graft failure (n = 1). In the 12 PoGF patients eltrombopag was started at the median time of 79 days after HSCT, due to persistent thrombocytopenia, with concomitant anemia and neutropenia in 7 and 3 patients, respectively. The treatment was started at the dose of 50 mg per day, and eventually increased up to 150 mg in case of lack of response. Hematological response was seen in 7 patients, with 6 complete responses. Hematological responses were seen both in patients with evidence of immune-mediated pathophysiology, and with possible infectious/iatrogenic causes. In responding patients, eltrombopag was discontinued in 6/7 patients without further relapse. These results suggest that eltrombopag is safe and possibly effective in the setting of the treatment of PoGF, and pave the way for future prospective studies.