Lentiviral Gene Therapy for the Correction of Congenital Dyserythropoietic Anemia Type II

Congenital dyserythropoietic anemias (CDAs) are a group of inherited anemias that affect the development of the erythroid lineage. CDA type II is the most common one: it accounts for around 60% of all cases, and more than 600 cases have been reported so far. CDA II is caused by biallelic mutations in the SEC23B gene and is characterized by ineffective erythropoiesis with morphologic abnormalities of erythroblasts, hemolysis, and secondary iron overload, which is the most frequent complication. Patients usually suffer from variable degrees of jaundice, splenomegaly, and absolute reticulocyte count inadequate depending on the degree of anemia. Hydrops fetalis, aplastic crisis and gallstones are other associated clinical signs. CDA II bone marrow is characterized by the presence of more than 10% mature binucleated erythroblasts. Another distinctive feature of CDA II erythrocytes is hypoglycosylation of membrane proteins. The management of CDA II is generally limited to blood transfusion and iron chelation. Splenectomy has proved to reduce the number of transfusions in CDA II patients. However, allogenic hematopoietic stem cell transplant (HSCT) represents the only curative option for this disease. Autologous HSCT of genetically corrected cells will mean a definitive treatment for CDA II, overcoming the limitations of allogeneic HSCT, such as limited availability of HLA-matched donors, infections linked to immunosuppression or development of graft versus host disease. This strategy has been used to treat many inherited hematological diseases, including red blood cell diseases such as β-thalassemia, sickle cell disease or pyruvate kinase deficiency. Therefore, we have addressed a similar strategy to be applied to CDAII patients. Two different lentiviral vectors carrying either wild type or codon optimized versions of SEC23B cDNA (wtSEC23B LV or coSEC23B LV, respectively) under the control of human phosphoglycerate kinase promoter (PGK) have been developed. Taking advantage of a CDA II model, in which SEC23B knock-out was done in human hematopoietic progenitors through gene editing, we have determined the most effective SEC23B LV version and the most suitable multiplicity of infection (MOI) to compensate protein deficiency. SEC23B knock out human hematopoietic progenitors (CD34 + cells; 80% frame shift mutations; SEC23BKO) showed a sharp reduction in SEC23B protein level. Those SEC23BKO hematopoietic progenitors were transduced with both lentiviral vectors at MOIs ranged from 3 to 25. We observed that SEC23B protein reached physiological or even supraphysiological levels. In addition, the reduction in the number of erythroid colony forming units (CFUs) identified in SEC23BKO CD34 + cells, was partially restored in the LV transduced SEC23BKO progenitors. Significantly, we observed a clear correlation between the used MOI and the vector copy number (VCN) in the CFUs derived from transduced SEC23BKO CD34 + cells. Furthermore, SEC23BKO hematopoietic progenitors were subjected to an in vitro erythroid differentiation protocol. A sharp decrease in the cell growth throughout erythroid differentiation was observed in SEC23BKO condition. However, the transduction with any of SEC23B LVs at MOIs above 10 was able to recover cell expansion to values equal to wild type cells. Interestingly, total level of protein glycosylation during erythroid differentiation was enhanced after SEC23B LV transduction. Glycosylation level in wtSEC23B LV transduced SEC23BKO cells was most similar to the level in wild type cells. Then, we transduced peripheral blood-derived hematopoietic progenitors (PB-CD34 + cells) from a CDA II patient with wtSEC23B LV at MOI 25 and differentiated in vitro to erythroid cells. A complete restauration of SEC23B protein expression and a cell growth increase of wtSEC23B transduced CDAII was observed with vector copy numbers of 0.3 after 14 days under erythroid conditions. More importantly, we could find a decrease in the percentage of bi-/multinucleated erythroid cells generated in vitro after wtSEC23B LV transduction. In summary, SEC23B LV compensate the SEC23B deficiency in SEC23BKO and in CDAII hematopoietic progenitor cells, paving the way for gene therapy of autologous hematopoietic stem and progenitor cell as an alternative and feasible treatment for CDA II. Disclosures Bianchi: Agios pharmaceutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Sanchez: Bloodgenetics: Other: Co-Founder and promoter; UIC: Current Employment. Ramirez: VIVEBiotech: Current Employment. Segovia: Rocket Pharmaceuticals, Inc.: Consultancy, Research Funding. Quintana Bustamante: Rocket Pharmaceuticals, Inc.: Current equity holder in publicly-traded company.

Modelling Congenital Dyserythropoietic Anemia Type II through Gene Editing in Hematopoietic Stem and Progenitor Cells

Congenital dyserythropoietic anemias (CDAs) are a group of inherited anemias that affect the development of the erythoid lineage. They are characterized by ineffective erythropoiesis with distinct morphologic abnormalities of erythroblasts, a degree of hemolysis, and secondary hemochromatosis. Patients usually present with congenital anemia, jaundice, splenomegaly, and an absolute reticulocyte count inadequate for the degree of anemia. CDA type II (CDAII) is the most frequent type. CDAII patients show anemia of variable degrees, and 20% are transfusion dependent. The most specific finding of CDAII marrow is the presence of more than 10% mature binucleated erythroblasts with two nuclei at the same erythroid maturation stage. Treatment of CDAII patients may involve blood transfusions, iron chelation therapy and splenectomy. The only described definitive therapy is allogeneic bone marrow transplantation, which implies additional side effects for these patients. Therefore, new therapeutic approaches are needed. CDA II is caused by mutations in the SEC23B gene. SEC23B is part of coat protein complex II (COPII). COPII is involved in protein processing and Golgi-reticulum trafficking. However, how mutations in SEC23B cause CDA II is not known yet. Therefore, studying the role of SEC23B in the erythropoiesis will help to elucidate the underlying mechanism of CDA II and to develop new therapeutic approaches for the disease. We have developed a CDA II model in human cells through the introduction of genomic mutations in the gene using the CRISPR/Cas9 gene editing system. Different single guides RNAs (sgRNA) targeting the start of the coding sequence of human SEC23B gene were designed and tested in human erythroleukemia K562 cell line and in healthy human cord blood hematopoietic stem and progenitors (hCB-CD34+). The gene editing outcome at SEC23B gene was assessed at: i) genomic level through Sanger sequencing, Inference of CRISPR Edits (ICE) and Next-Generation Sequencing (NGS). ii) Protein level through Western-blot analysis. iii) Functional level through morphological analysis and erythroid differentiation either in vitro or in vivo in human hematopoietic chimeras in NOD.Cg-KitW-41JTyr+PrkdcscidIl2rgtm1Wjl/ThomJ (NBSGW) mice. K562 cells were nucleofected with three different sgRNAs, as ribonucleoprotein (RNP), independently or in combination. Afterwards, seventy five K562 clones were established from the cells nucleofected with the most efficient sgRNA or with the combination of the three sgRNAs. Forty per cent of them showed a high efficiency of knock-out (higher than 50% of alleles). Eight SEC23BKO clones were selected for further analysis. All of those eight clones showed a reduction in SEC23B protein and six of them had a lower proliferation than control cells and morphological abnormalities, such as presence of bi/multinucleated cells. Moreover, when CB-CD34+ cells were nucleofected with the most efficient sgRNA or with the combination of the three sgRNAs, up to 80% of knock-out efficiency and close to 90% reduction of SEC23B protein were obtained. Interestingly, when those gene edited hematopoietic progenitors were differentiated in vitro to erythroid cells, their terminal differentiation was hampered, with a reduce percentage of enucleated cells and the presence of high number of bi/multinucleated cells. Similarly, the in vivo erythroid differentiation of these gene edited progenitors two months after HSPC transplant into NBSGW mice showed again an impairment of terminal erythroid differentiation with an increment in the percentage of erythroid bi/multinucleated cells without altering other human hematopoietic lineages. In summary, CRISPR/Cas9 system has been used to model CDA II in a human cell line and in human hematopoietic progenitors through the knock-out of SEC23B gene. Our system reproduced the most relevant feature characteristic of CDA II pathology. This gene editing based CDA II model will allow the study of how mutations in SEC23B cause CDA II and the development of new therapeutic strategies to cure this disease. Disclosures Tornador: Bloodgenetics: Current Employment. Sanchez:Bloodgenetics: Current Employment. Segovia:Rocket Pharmaceuticals, Inc.: Consultancy, Current equity holder in publicly-traded company, Other: Consultant for Rocket Pharmaceuticals, Inc. and has licensed medicinal products and receives research funding and equity from the Company., Patents & Royalties, Research Funding.

RAP-011 Rescues the Disease Phenotype in a Cellular Model of Congenital Dyserythropoietic Anemia Type II by Inhibiting the SMAD2-3 Pathway

Congenital dyserythropoietic anemia type II (CDA II) is a hypo-productive anemia defined by ineffective erythropoiesis through maturation arrest of erythroid precursors. CDA II is an autosomal recessive disorder due to loss-of-function mutations in SEC23B. Currently, management of patients with CDA II is based on transfusions, splenectomy, or hematopoietic stem-cell transplantation. Several studies have highlighted benefits of ACE-011 (sotatercept) treatment of ineffective erythropoiesis, which acts as a ligand trap against growth differentiation factor (GDF)11. Herein, we show that GDF11 levels are increased in CDA II, which suggests sotatercept as a targeted therapy for treatment of these patients. Treatment of stable clones of SEC23B-silenced erythroleukemia K562 cells with the iron-containing porphyrin hemin plus GDF11 increased expression of pSMAD2 and reduced nuclear localization of the transcription factor GATA1, with subsequent reduced gene expression of erythroid differentiation markers. We demonstrate that treatment of these SEC23B-silenced K562 cells with RAP-011, a “murinized” ortholog of sotatercept, rescues the disease phenotype by restoring gene expression of erythroid markers through inhibition of the phosphorylated SMAD2 pathway. Our data also demonstrate the effect of RAP-011 treatment in reducing the expression of erythroferrone in vitro, thus suggesting a possible beneficial role of the use of sotatercept in the management of iron overload in patients with CDA II.

Biallelic Mutations in PARP4 Are Linked to a Variant Form of Congenital Dyserythropoietic Anemia

Congenital dyserythropoietic anemia (CDA) type II is the most frequent type of congenital dyserythropoietic anemia; it is transmitted in an autosomal recessive fashion and is characterized by ineffective erythropoiesis, peripheral hemolysis, bi-multinuclearity in the erythroblasts, and hypoglycosylation of red blood cell (RBC) membrane proteins such as band 3. The disease is generally caused by biallelic mutations in the SEC23B gene. However, there are a small portion of patients with clinical and hematologic features of CDA II that are negative for mutations in SEC23B, suggesting that alternative etiologies for such disturbed erythropoiesis exist. We identified two siblings of Italian origin who had dyserythropoiesis with a chronic macrocytic anemia. Their parents were healthy with normal hematologic parameters. No history of consanguinity for at least three generations was noted. The affected siblings had anisopoikylocytosis on peripheral blood smear with stomatocytes (8-9%), spherocytes (4-5%), rare ovalocytes, and dacryocytes. RBCs osmotic fragility was increased but the red cells had normal eosin-5-maleimide (EMA)-binding. Serum ferritin and transferrin saturation were increased in only one sibling. Bone marrow morphology revealed erythroid hyperplasia (myeloid: erythroid ratio = 0.6) with binuclearity and megaloblastic changes, as well as occasional cytoplasmic bridging between cells at different stage of maturation; electron microscopy of bone marrow erythroblasts showed multiple membranes that ran parallel to the plasma membrane or that were grouped in stacked segments, possibly attributable to residual endoplasmic reticulum (ER) cisternae. SDS-PAGE analysis of RBC ghosts from both siblings demonstrated hypoglycosylation of band 3 and GLUT1, as well as residual residual Protein Disulphide Isomerase (PDI) positive ER remnants, as observed in classical CDA II cases. However, in contrast to CDAII, the Ham's test performed with 15 normal serum samples was negative, and no mutations were detected in the SEC23B gene. To uncover the underlying etiologies, whole-exome sequencing was conducted on all available family members. After filtering for common variants, only a single gene had biallelic mutations in the affected siblings, which were transmitted from the unaffected heterozygous parents. The identified mutations resided in the PARP4 gene, which encodes a poly-ADP ribose polymerase enzyme, and were predicted to be deleterious. We demonstrate that knockdown of PARP4 using shRNA in primary human erythroid progenitors results in impaired erythroid differentiation and increased apoptosis. In addition, morpholino-mediated knockdown of the PARP4 orthologue in the zebrafish resulted in dyserythropoiesis and anemia in developing embryos. Sequencing of PARP4 in additional rare cases of CDA II without an identified molecular basis will help to uncover the frequency and spectrum of PARP4 mutations leading to dyserythropoiesis. The finding of a new gene implicated in a similar type of CDA with features such as redundant ER membranes offers the potential for more mechanistic dissection of the role of both SEC23B and PARP4 in erythroid development and suggests that new insight can be gained into the underlying pathophysiology of both normal and disordered erythropoiesis through the study of such rare cases. Disclosures No relevant conflicts of interest to declare.

Successful Allogeneic Hematopoietic Stem Cell Transplantation of a Patient Suffering from Type II Congenital Dyserythropoietic Anemia A Rare Case Report from Western India

The most frequent form of congenital dyserythropoiesis (CDA) is congenital dyserythropoietic anemia II (CDA II). CDA II is a rare genetic anemia in humans, inherited in an autosomally recessive mode, characterized by hepatosplenomegaly normocytic anemia and hemolytic jaundice. Patients are usually transfusion-independent except in severe type. We are here reporting a case of severe transfusion-dependent type II congenital dyserythropoietic anemia in a 5-year-old patient who has undergone allogeneic hematopoietic stem cell transplantation (HSCT) at our bone marrow transplantation centre. Patient has had up until now more than 14 mL/kg/month of packed cell volume (PCV), which he required every 15 to 20 days to maintain his hemoglobin of 10 gm/dL and hematocrit of 30%. His pre-HSCT serum ferritin was 1500 ng/mL and he was on iron chelating therapy. Donor was HLA identical sibling (younger brother). The preparative regimen used was busulfan, cyclophosphamide, and antithymocyte globulin (Thymoglobulin). Cyclosporine and short-term methotrexate were used for graft versus host disease (GVHD) prophylaxis. Engraftment of donor cells was quick and the posttransplant course was uneventful. The patient is presently alive and doing well and he has been transfusion-independent for the past 33 months after HSCT.

Low-Dose Uroacitides(CDA-II) Downregulates Telomerase Activity and Inhibits Proliferation in the Telomerase-Expressing Maliganant Cell Lines Through Inactivation of Akt Signaling Pathway

Abstract 4920 Uroacitides, another name CDA-II (cell differentiation agent II), is a mixture product and isolated from healthy human urine in China. It is characterized as a novel molecular targeting agent for cancer therapy. Multiple active components, such as peptides (MW 400–2800), organic acids, pigments and phenylacetylglutamine, with different mechanisms of action act concurrently to contribute to the anticancer effect of CDA-II. We have reported that high-dose CDA-II could induce acute myeloid leukemia (AML) cell apoptosis. Here, in the light of the important role of telomerase in malignant transformation. We evaluated the effect of low-dose CDA-II on telomerase activity (TA) and regulation in various malignant cell lines. CDA-II caused a dose-dependent inhibition of TA (up to 80% at a concentration of 0. 5 mg/mL) in Hela (cervix uteri cancer), MCF-7(breast cancer), SW480(colon cancer), RPMI8226(myeloma), HL-60 (AML), Raji (Burkitt lymphoma), L428 (Hodgkin's disease). Low-dose CDA-II did not affect the activity of other DNA polymerases. Inhibition of TA was associated with 60% inhibition of proliferation. The inhibition of proliferation was associated with a decrease in the S phase of the cell cycle and an accumulate of cells in G1 phase. No apoptosis was observed. Inhibition of TA was caused by dephosphorylation of Akt and by early downregulation of hTERT transcription. Other steps of telomerase regulation were not affected by low-dose CDA-II. This study demonstrated an additional cellular target of low-dose CDA-II that causes inhibition of TA and cell proliferation. Disclosures: No relevant conflicts of interest to declare.