Gene Therapy in Patients with Transfusion-Dependent β-Thalassemia

In the paper

“The risks of serious complications from transfusion-related iron toxicity and viral infections persist despite improvements in care.10,11”

What the sources say

• Supported

  The Transfusion-Associated Iron Deposition section says iron overload remains a major cause of mortality despite improvements in monitoring and treatment. The Transfusion-associated infections section recommends continued viral surveillance, reports hepatitis C seropositivity, and notes that fewer young patients now seroconvert. Page numbers are unavailable in our copy. (LLM, conf=0.91)

  cites [10] 10. Tubman VN, Fung EB, Vogiatzi M, et al. Guidelines for the standard monitoring of patients with thalassemia: report of the Thalassemia Longitudinal Cohort. J Pedi- atr Hematol Oncol 2015; 37(3): e162-e169. source
• ?Not checked — no full text of the sourcecites [11] 11. Bonifazi F, Conte R, Baiardi P, et al. Pattern of complications and burden of disease in patients affected by beta thal- assemia major. Curr Med Res Opin 2017; 33: 1525-33. source

In the paper

“Thus, the current standard of care for patients with β-thalassemia consists of lifelong, regular red-cell transfusions and iron chelation.9”

What the sources say

• ?Could not verify

  The Introduction mentions thalassemia as an inherited blood disease but does not describe its standard care. Searches for regular transfusions, iron chelation, and thalassemia treatment found relevant titles in the References, not a passage in the cited paper stating the claimed regimen. (LLM, conf=0.74)

  cites [9] 9. Engert A, Balduini C, Brand A, et al. The European Hematology Association Roadmap for European Hematology Re- search: a consensus document. Haemato- logica 2016; 101: 115-208. sourceExperimental — accuracy not yet measured

In the paper

“Limited changes in the LentiGlobin vector (HPV569 vs. BB305) did not significantly alter the expression of β A-T87Q -globin per integrated vector copy, but they contributed (along with changes in vector manufacturing) to an increase in vector titers by a factor of approximately 4. 14,24,37”

What the sources say

• Partly supported

  The BB305 lentiviral vector section says BB305 is identical to HPV569 after integration except for removal of the cHS4 insulator, whose effect on transgene expression was limited. It does not report a direct comparison of βA-T87Q-globin expression per integrated vector copy or establish that the difference was statistically nonsignificant. No page number is available in our copy. (LLM, conf=0.78)

  cites [14] 14. Negre O, Eggimann AV, Beuzard Y, et al. Gene therapy of the β-hemoglobin- opathies by lentiviral transfer of the β(A(T87Q))-globin gene. Hum Gene Ther 2016; 27: 148-65. sourceExperimental — accuracy not yet measured
• Supported

  The Results section on primary-transplant β-thalassemia mice states that expression per vector copy was similar for BB305 and HPV569, citing in vitro studies in human CD34+ cells. The vector-design Results section also says the integrated βA-T87Q-globin expression cassette was identical in the two vectors. Page numbers are not available in our copy. (LLM, conf=0.92)

  cites [24] 24. Negre O, Bartholomae C, Beuzard Y, et al. Preclinical evaluation of efficacy and safety of an improved lentiviral vector for the treatment of β-thalassemia and sickle cell disease. Curr Gene Ther 2015; 15: 64-81. source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [37] 37. Walters MC, Thompson A, Hongeng S, et al. A phase 3 study to evaluate safety and efficacy of LentiGlobin gene therapy for transfusion-dependent beta-thalassemia in patients with non-beta0/beta0 geno- types: the Northstar-2 (HGB-207) trial. Haematologica 2017; 102: 335. abstract.

In the paper

“Limited changes in the LentiGlobin vector (HPV569 vs. BB305) did not significantly alter the expression of β A-T87Q -globin per integrated vector copy, but they contributed (along with changes in vector manufacturing) to an increase in vector titers by a factor of approximately 4. 14,24,37”

What the sources say

• Partly supported

  The BB305 lentiviral vector section (page unavailable) reports that changes from HPV569 to BB305 increased vector titers 3–4-fold, supporting the approximate fourfold figure. The Production of lentiviral vectors section describes manufacturing, but does not say manufacturing changes contributed to that increase. (LLM, conf=0.86)

  cites [14] 14. Negre O, Eggimann AV, Beuzard Y, et al. Gene therapy of the β-hemoglobin- opathies by lentiviral transfer of the β(A(T87Q))-globin gene. Hum Gene Ther 2016; 27: 148-65. sourceExperimental — accuracy not yet measured
• Supported

  The Results section reports that BB305 harvest titers were approximately 3–4 times higher than HPV569 titers. The Introduction says the vector redesign also reduced the number of plasmids required for production and improved vector yield. Page numbers were not provided in our copy. (LLM, conf=0.91)

  cites [24] 24. Negre O, Bartholomae C, Beuzard Y, et al. Preclinical evaluation of efficacy and safety of an improved lentiviral vector for the treatment of β-thalassemia and sickle cell disease. Curr Gene Ther 2015; 15: 64-81. source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [37] 37. Walters MC, Thompson A, Hongeng S, et al. A phase 3 study to evaluate safety and efficacy of LentiGlobin gene therapy for transfusion-dependent beta-thalassemia in patients with non-beta0/beta0 geno- types: the Northstar-2 (HGB-207) trial. Haematologica 2017; 102: 335. abstract.

In the paper

“The feasibility of the addition of a gene to autologous hematopoietic cells using a lentiviral vector was shown previously in a single patient with β-thalassemia who safely discontinued transfusions for more than 6 years with ongoing, sustained β A-T87Q -globin expression.14,20”

What the sources say

• Supported

  Split into 2 atoms — 2 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

  cites [14] 14. Negre O, Eggimann AV, Beuzard Y, et al. Gene therapy of the β-hemoglobin- opathies by lentiviral transfer of the β(A(T87Q))-globin gene. Hum Gene Ther 2016; 27: 148-65. source
• ?Not checked — no full text of the sourcecites [20] 20. Cavazzana-Calvo M, Payen E, Negre O, et al. Transfusion independence and HMGA2 activation after gene therapy of human β-thalassaemia. Nature 2010; 467: 318-22. source

In the paper

“A patient with a severe β E /β 0 genotype safely discontinued transfusions for more than 6 years with sustained β A-T87Q -globin expression.13,20”

What the sources say

• Partly supported

  The Phase I Clinical Trials section reports a patient whose vector-derived globin contributed to transfusion independence and whose clinically beneficial clone persisted for seven years. It does not identify that patient as having a βE/β0 genotype; it describes a β+ form of the disease. Calling the outcome unqualifiedly safe also omits the reported adverse clonal expansion, although the clone did not progress to leukemia. (LLM, conf=0.88)

  cites [13] 13. Mansilla-Soto J, Riviere I, Boulad F, Sadelain M. Cell and gene therapy for the beta-thalassemias: advances and pros- pects. Hum Gene Ther 2016; 27: 295-304. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [20] 20. Cavazzana-Calvo M, Payen E, Negre O, et al. Transfusion independence and HMGA2 activation after gene therapy of human β-thalassaemia. Nature 2010; 467: 318-22. source

In the paper

“The remaining 3 patients with a β 0 /β 0 genotype or two copies of the IVS1-110 mutation had not received transfusions for 14 to 20 months”

In the paper

“With follow-up extending to 3 years (median, 26 months) after infusion, no serious adverse events related to the drug product have been detected, and there were no significant unexpected safety issues.”

In the paper

“With follow-up extending to 3 years (median, 26 months) after infusion, no serious adverse events related to the drug product have been detected, and there were no significant unexpected safety issues.”

In the paper

“and red-cell transfusions were discontinued in 3 patients.”

In the paper

“in the HGB-204 study, among the 8 patients with a β 0 /β 0 genotype (for whom the threshold HbA T87Q level that was necessary for discontinuation of red-cell transfusion was higher in the absence of endogenous production of β-like globin chains), transfusion support after treatment was reduced but not eliminated in 6 patients”

In the paper

“the patient with two copies of the IVS1-110 mutation, in whom the clinical severity mirrored that of patients with a β 0 /β 0 genotype, has also discontinued receiving transfusions.”

In the paper

“Gene therapy with autologous CD34+ cells transduced with the BB305 vector reduced or eliminated the need for long-term red-cell transfusions in 22 patients with severe β-thalassemia without serious adverse events related to the drug product.”

In the paper

“serial monitoring of vector integration sites in blood samples has consistently shown polyclonal profiles of unique integration sites without domi-nant clones.”

In the paper

“the levels of total hemoglobin ranged from 8.2 to 13.7 g per deciliter”

In the paper

“Correction of biologic markers of dyserythropoiesis was achieved in evaluated patients with hemoglobin levels near normal ranges.”

In the paper

“At a median of 26 months (range, 15 to 42) after infusion of the gene-modified cells, all but 1 of the 13 patients who had a non-β 0 /β 0 genotype had stopped receiving red-cell transfusions”

In the paper

“In 9 patients with a β 0 /β 0 genotype or two copies of the IVS1-110 mutation, the median annualized transfusion volume was decreased by 73%”

In the paper

“In the two studies, the vector copy number in the drug product was found to correlate with the vector copy number in PBMCs, which in turn correlated with the production of vector-encoded β A-T87Q -globin.”

In the paper

“Consequently, the vector copy number in the drug product appears to be a key determinant of HbA T87Q levels in blood, which were similar across β-thalassemia genotypes.”

In the paper

“Of the 22 treated patients, 7 expressed at least 8 g per deciliter of HbA T87Q , including 3 patients with a β 0 /β 0 genotype or the severe IVS1-110 mutation; all have been free from transfusion for more than 1 year.”

In the paper

“No replication-competent lentivirus has been detected in the patients in either study”

In the paper

“These patients had a vector copy number of more than 0.6 in the drug product.”

In the paper

“and normal or nearly normal total hemoglobin levels in several patients (Table 2).”

In the paper

“In a pooled analysis, there was significant correlation between the vector copy number in PBMCs at 6 months and the initial vector copy number in the drug product (r 2 = 0.69, P<0.001)”

In the paper

“In the 2 years before enrollment, the median red-cell transfusion volume was 182 ml per kilogram per year (range, 139 to 197).”

In the paper

“In the two studies, blood HbA T87Q levels correlated with blood vector copy number levels (r 2 = 0.75, P<0.001)”

In the paper

“In addition, the plasma ratio of hepcidin to ferritin increased substantially over time in these patients.”

In the paper

“and biologic hallmarks of dyserythropoiesis were largely eliminated.”

In the paper

“clinical outcomes appeared to vary according to the underlying genotype.”

In the paper

“Preliminary assessments of dyserythropoiesis in the 3 patients with a β E /β 0 genotype who were enrolled in HGB-205 showed stabilization and then correction of hemolysis”

In the paper

“No safety issues were attributed to the BB305 vector in either study.”

In the paper

“the levels of HbA T87Q ranged from 3.4 to 10.0 g per deciliter”

In the paper

“In the two studies, the vector copy number in the drug product was found to correlate with the vector copy number in PBMCs, which in turn correlated with the production of vector-encoded β A-T87Q -globin.”

In the paper

“No clonal dominance related to vector integration was observed.”

In the paper

“Treatment-related adverse events were typical of those associated with autologous stem-cell transplantation.”

In the paper

“All 12 patients with a non-β 0 /β 0 genotype who achieved and maintained a vector copy number of more than 0.1 in PBMCs, including the 9 patients with a β E /β 0 genotype, stopped receiving red-cell transfusions”

In the paper

“The normalization in markers of dyserythropoiesis correlated with the hemoglobin levels that were achieved.”

In the paper

“In the HGB-204 and HGB-205 studies, no clonal dominance was detected in any patient at any time point.”

In the paper

“At the time of the last study visit, the patients' hemoglobin levels were stable, despite a cumulative phlebotomy volume of more than 1 liter per patient.”

In the paper

“Plasma levels of two markers of ineffective erythropoiesis or erythroid expansion, soluble transferrin receptor 32 and erythroid protoporphyrin IX, 33 were within normal ranges for the 3 patients with a β E /β 0 genotype after they had stopped receiving transfusions.”

What the sources say

• ?Not checked — no full text of the sourcecites [32] 32. Ricchi P, Ammirabile M, Costantini S, et al. Soluble form of transferrin receptor as a biomarker of overall morbidity in patients with non-transfusion-dependent thalassaemia: a cross-sectional study. Blood Transfus 2016; 14: 538-40. source
• ?Not checked — no full text of the sourcecites [33] 33. Graham EA, Felgenhauer J, Detter JC, Labbe RF. Elevated zinc protoporphyrin as- sociated with thalassemia trait and hemo- globin E. J Pediatr 1996; 129: 105-10. source

In the paper

“Other factors, such as age, genotype, and splenectomy status, did not appear to correlate with gene expression.”

In the paper

“One patient (Patient 1202) who no longer had any evidence of dyserythropoiesis and iron overload was able to discontinue both iron chelation therapy and therapeutic phlebotomy.”

In the paper

“Gene therapy with autologous CD34+ cells transduced with the BB305 vector reduced or eliminated the need for long-term red-cell transfusions in 22 patients with severe β-thalassemia without serious adverse events related to the drug product.”

In the paper

“and 2 of these patients have stopped receiving transfusions.”

In the paper

“In HGB-204, five mild adverse effects (all grade 1) were characterized as related or possibly related to the drug product.”

In the paper

“In contrast, complete normalization of biologic markers of ineffective erythropoiesis was not observed in Patient 1203 (IVS1-110 homozygote)”

In the paper

“and a positive correlation with hepcidin levels and hepcidin:ferritin ratios (Spearman r = 0.57, P = 0.01 for both calculations).”

In the paper

“and erythroid protoporphyrin IX levels in red cells (Spearman r = -0.85,P<0.001)”

In the paper

“The safety profile after infusion was consistent with that associated with myeloablative conditioning with single-agent busulfan.”

In the paper

“In a pooled analysis, there was significant correlation between the VCN in the drug product and the VCN in PBMCs at 6 months (Panel C).”

In the paper

“Hemoglobin levels had a negative correlation with soluble TFR levels (Spearman r = -0.63,P<0.001)”

In the paper

“Blood HbA T87Q levels correlated with VCN values in PBMCs at 6 months (Panel C).”

In the paper

“In the HGB-204 and HGB-205 studies, no clonal dominance was detected in any patient at any time point.”

In the paper

“the numbers of unique integration sites that were found in the patients in HGB-204 and HGB-205 were higher by a factor of 150 to 500 than the numbers of sites in patients who were enrolled in the LG001 study at the same time points.”

In the paper

“Lentiviral vectors have the ability to transfer complex genetic structures into quiescent hematopoietic stem cells.16”

What the sources say

• ?Not checked — no full text of the sourcecites [16] 16. Naldini L, Blömer U, Gallay P, et al. In vivo gene delivery and stable transduction of nondividing cells by a lentiviral vector. Science 1996; 272: 263-7. source

In the paper

“After establishing that β-globin lentiviral vectors had successfully corrected models of β-thalassemia and sickle cell disease in mice, 17,18 we initiated a human clinical study of ex vivo gene therapy for the β-hemoglobinopathies”

What the sources say

• ?Not checked — no full text of the sourcecites [17] 17. May C, Rivella S, Callegari J, et al. Therapeutic haemoglobin synthesis in beta- thalassaemic mice expressing lentivirus- encoded human beta-globin. Nature 2000; 406: 82-6. source
• ?Not checked — no full text of the sourcecites [18] 18. Pawliuk R, Westerman KA, Fabry ME, et al. Correction of sickle cell disease in transgenic mouse models by gene therapy. Science 2001; 294: 2368-71. source

In the paper

“Because complete myeloablation is essential for high-level engraftment with ex vivo transduced hematopoietic stem cells 27,28 and increased busulfan metabolism had been reported in some patients with β-thalassemia, 29 plasma busulfan pharmacokinetic analysis was performed in all the patients”

What the sources say

• ?Not checked — no full text of the sourcecites [27] 27. Hayakawa J, Ueda T, Lisowski L, et al. Transient in vivo beta-globin production after lentiviral gene transfer to hemato- poietic stem cells in the nonhuman pri- mate. Hum Gene Ther 2009; 20: 563-72. source
• ?Not checked — no full text of the sourcecites [28] 28. Chandrasekaran D, Nakamoto B, Watts KL, Kiem HP, Papayannopoulou T. Model- ing promising nonmyeloablative condi- tioning regimens in nonhuman primates. Hum Gene Ther 2014; 25: 1013-22. source

In the paper

“The studies were not powered to conclusively assess determinants of response.”

In the paper

“increased busulfan metabolism had been reported in some patients with β-thalassemia, 29”

What the sources say

• ?Not checked — no full text of the sourcecites [29] 29. Shteyer E, Nitzan I, Godfarb A, Hemed N, Revel-Vilk S. Activity of cyto- chrome P450 1A2 in relation to hepatic iron accumulation in transfusion-depen- dent β-thalassaemia major patients. Vox Sang 2015; 108: 268-73. source

In the paper

“The relative clonal dominance at the HMGA2 locus that was initially observed in 1 patient in the LG001 study of the HPV569 vector spontaneously subsided while that patient maintained stable HbA T87Q levels.”

What the sources say

• ?Not checked — no full text of the sourcecites [20] 20. Cavazzana-Calvo M, Payen E, Negre O, et al. Transfusion independence and HMGA2 activation after gene therapy of human β-thalassaemia. Nature 2010; 467: 318-22. source

In the paper

“Together, these results point to the elimination of dyserythropoiesis in the 3 patients with a β E /β 0 genotype who were treated.”

In the paper

“Consequently, the vector copy number in the drug product appears to be a key determinant of HbA T87Q levels in blood, which were similar across β-thalassemia genotypes.”

In the paper

“These results suggest that achieving transfusion independence is an attainable goal for most patients with a β 0 /β 0 genotype if the rates of hematopoietic-cell transduction can be further improved.”

In the paper

“The number of patients who were treated remains relatively small, so extended follow-up is required to establish the durability of transduction hematopoietic stem cells and progenitor cells after a single infusion.”

In the paper

“The very low dose of vector-transduced hematopoietic cells that was received by Patient 1003 in the LG001 study was a major contributor to the development of oligoclonality.”

In the paper

“In conclusion, we found that gene therapy with LentiGlobin drug product succeeded in overcoming a principal limitation of allogeneic hematopoietic-cell transplantation, which is a lack of a histocompatible donor.”