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RAP-011, an activin receptor ligand trap, increases hemoglobin concentration in hepcidin transgenic mice.

ABSTRACT: Over expression of hepcidin antimicrobial peptide is a common feature of iron-restricted anemia in humans. We investigated the erythroid response to either erythropoietin or RAP-011, a "murinized" ortholog of sotatercept, in C57BL/6 mice and in hepcidin antimicrobial peptide 1 over expressing mice. Sotatercept, a soluble, activin receptor type IIA ligand trap, is currently being evaluated for the treatment of anemias associated with chronic renal disease, myelodysplastic syndrome, ?-thalassemia, and Diamond Blackfan anemia and acts by inhibiting signaling downstream of activin and other Transforming Growth Factor-? superfamily members. We found that erythropoietin and RAP-011 increased hemoglobin concentration in C57BL/6 mice and in hepcidin antimicrobial peptide 1 over expressing mice. While erythropoietin treatment depleted splenic iron stores in C57BL/6 mice, RAP-011 treatment did not deplete splenic iron stores in mice of either genotype. Bone marrow erythroid progenitors from erythropoietin-treated mice exhibited iron-restricted erythropoiesis, as indicated by increased median fluorescence intensity of transferrin receptor immunostaining by flow cytometry. In contrast, RAP-011-treated mice did not exhibit the same degree of iron-restricted erythropoiesis. In conclusion, we have demonstrated that RAP-011 can improve hemoglobin concentration in hepcidin antimicrobial peptide 1 transgenic mice. Our data support the hypothesis that RAP-011 has unique biologic effects which prevent or circumvent depletion of mouse splenic iron stores. RAP-011 may, therefore, be an appropriate therapeutic for trials in human anemias characterized by increased expression of hepcidin antimicrobial peptide and iron-restricted erythropoiesis.

SUBMITTER: Langdon JM

PROVIDER: S-EPMC4276439 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Project description:Lessons learnedPatients with hepatocellular carcinoma (HCC) often have limited therapeutic responses to the vascular endothelial growth factor (VEGF) tyrosine kinase inhibitor sorafenib, which is standard of care in advanced HCC. Targeting the activin receptor-like kinase 1 (ALK1) and VEGF pathways simultaneously by combining the ALK1 ligand trap dalantercept with sorafenib may result in more effective angiogenic blockade and delay tumor progression in patients with advanced HCC.Although the combination was generally well tolerated, there was no additive antitumor activity with the combination of dalantercept plus sorafenib in patients with advanced HCC. No complete or partial responses were observed, and overall survival ranged from 1.9 to 23.3 months.These results suggest that, in this patient population, further development of the possible limited benefits of combination therapy with dalantercept plus sorafenib is not warranted.BackgroundTargeting the activin receptor-like kinase 1 (ALK1) and vascular endothelial growth factor (VEGF) pathways may result in more effective angiogenic blockade in patients with hepatocellular carcinoma (HCC).MethodsIn this phase Ib study, patients with advanced HCC were enrolled to dose-escalation cohorts, starting at 0.6 mg/kg dalantercept subcutaneously every 3 weeks plus 400 mg sorafenib orally once daily, or to a dose expansion cohort. The primary objective was to determine the safety and tolerability and the dalantercept maximum tolerated dose (MTD) level. Secondary objectives were to assess the preliminary activity and the association of pharmacodynamic biomarkers with tumor response.ResultsA total of 21 patients were enrolled in the study. Five patients received 0.6 mg/kg dalantercept in the first dose escalation cohort. Based on the initial safety results, the dose level was de-escalated to 0.4 mg/kg in the second cohort (n = 6). The MTD was identified as 0.4 mg/kg and used for the dose expansion cohort (n = 10). At this dose level, the combination was generally well tolerated. Overall survival ranged from 1.9 to 23.3 months, and the best overall response was stable disease.ConclusionThe addition of dalantercept to sorafenib did not improve antitumor activity in patients with HCC. The dalantercept program in this population was discontinued.

Project description:Hepcidin, a peptide hormone that decreases intestinal iron absorption and macrophage iron release, is a potential drug target for patients with iron overload syndromes because its levels are inappropriately low in these individuals. Endogenous stimulants of Hepcidin transcription include bone morphogenic protein 6 (BMP) and interleukin-6 (IL-6) via effects on Smad4 or Stat3, respectively. We conducted a small-scale chemical screen in zebrafish embryos to identify small molecules that modulate hepcidin expression. We found that treatment with the isoflavone genistein from 28−52 hours post-fertilization in zebrafish embryos enhanced Hepcidin transcript levels as assessed by whole mount in situ hybridization and quantitative realtime RT-PCR. Genistein’s stimulatory effect was conserved in human hepatocytes: genistein treatment of HepG2 cells increased both Hepcidin transcript levels and Hepcidin promoter activity. We found that genistein’s effect on Hepcidin expression did not depend on estrogen receptor signaling or increased cellular iron uptake, but was impaired by mutation of either the BMP response elements or the Stat3 binding site in the Hepcidin promoter. RNA-sequencing of transcripts from genistein-treated hepatocytes indicated that genistein upregulated 68% of the transcripts that were upregulated by BMP6, however genistein raised the levels of several transcripts involved in Stat3 signaling that were not upregulated by BMP6. Chromatin-immunoprecipitation and ELISA experiments revealed that genistein enhanced Stat3 binding to the Hepcidin promoter and increased phosphorylation of Stat3 in HepG2 cells. CONCLUSION: Genistein is the first small molecule experimental drug that stimulates Hepcidin expression in vivo and in vitro. These experiments demonstrate the feasibility of identifying and characterizing small molecules that increase Hepcidin expression. Genistein and other candidate molecules may subsequently be developed into new therapies for iron overload syndromes. RNA-seq of HepG2 cells treated with DMSO 1%, BMP6 50 ng/ml, or genistein 10 micromolar. The numbers of biological replicates were 3, 2, and 3.

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RAP-011, an activin receptor ligand trap, increases hemoglobin concentration in hepcidin transgenic mice.

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