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4875 Erythroid-Specific Chimerism Analysis after Allogeneic-Hematopoietic Stem Cell Transplantation Using a Human Leukocyte Antigen-Identical Sibling Donor in Sickle Cell Disease Patients

Program: Oral and Poster Abstracts
Session: 721. Allogeneic Transplantation: Conditioning Regimens, Engraftment, and Acute Toxicities: Poster III
Hematology Disease Topics & Pathways:
Clinical Practice (Health Services and Quality)
Monday, December 9, 2024, 6:00 PM-8:00 PM

Gonzalo De Luna, MD1*, Nicolas Hebert, PhD2*, Ivan Sloma, PhD3*, Florence Beckerich, MD4*, Rabah Redjoul, MD4*, Anoosha Habibi, MD1, Mathieu Leclerc, MD, PhD4*, Vincent Parinet, MD4*, Christine Robin, MD4*, Cécile Pautas, MD4*, Stephane Moutereau, MD5*, Fatima Bensiradj, MD1*, Meghan Perkins, PhD2*, France Pirenne, MD, PhD6,7, Dehbia Menouche, MD8*, Pablo Bartolucci, MD, PhD1,2* and Sébastien Maury, MD, PhD4*

1Sickle Cell Referral Center, UMGGR, Department of Internal Medicine, Henri-Mondor University Hospital- UPEC, AP-HP, Créteil, France
2Université Paris-Est Créteil, INSERM U955, IMRB, Laboratory of excellence LABEX GRex, Créteil, France
3Hematology and Immunology Department, Henri Mondor University Hospital, UPEC, IMRB, Assistance Publique Hopitaux de Paris, Créteil, France
4Hematology Department, Henri Mondor University Hospital, UPEC, IMRB, Assistance Publique Hopitaux de Paris, Créteil, France
5Department of Biochemistry, Henri-Mondor University Hospital- UPEC, AP-HP, Creteil, France
6Transfusion et maladies du globule rouge - Equipe Pirenne, Institut Mondor de Recherche Biomedicale (IMRB), Creteil, France
7Etablissement Francais Du Sang - Université Paris-Est Créteil Hospital, Creteil, France
8Apheresis, Hopital Henri Mondor, Créteil, France

Introduction: Allogeneic-hematopoietic stem cell transplantation (HSCT) using a human leukocyte antigen (HLA)-identical sibling donor is a proven cure for Sickle Cell disease (SCD). At least 20% donor myeloid chimerism in peripheral blood (PB) may be sufficient to reverse the sickle phenotype after HSCT. Here, we sought to implement an erythroid-specific chimerism analysis in order to decipher kinetics of lineage-specific engraftments and correlated biological and clinical phenotypes.

Method: Adult SCD patients who underwent an allogeneic non-myeloablative HSCT from HLA-matched related donors were included between 2020-2024 in our referral center Henri Mondor Hospital. Data were analyzed at 6 months post HSCT. Erythroid-specific chimerism was assessed in PB by flow cytometry using specific anti-Human-bS-globin and anti-Human-b-globin fluorescent monoclonal antibodies. Erythroid-specific chimerism was assessed in mature CD71-negative red blood cells (RBC) and in CD71+ reticulocytes. In parallel, donor chimerism was assessed in total white blood cells (WBC) and sorted CD3+ lymphocytes. Hemolytic follow-up included Hb level, reticulocytes count, plasma lactate dehydrogenase (LDH); an extended panel was proposed with measures of free plasma-Hb, heme and hemopexin by spectrophotometric assays. Event-free survival (EFS) at 6 months was defined as the probability of being alive with sustained donor cell engraftment (HbS<30%) and no vaso-occlusive event (VOE).

Assuming that donor CD 71+ is correlated with level of erythroid engraftment, patients with a sustained donor engraftment (HbS<30%) was classified as total (>80% donor CD71+ chimerism) or partial engraftment (20-80% donor CD71+ chimerism). Graft failure (GF), graft-versus-host disease (GVHD), [HbS] and overall survival (OS) were also analyzed.

Results: Eleven patients were analyzed at 6 months post-HSCT. Homozygous SS genotype was showed in 82%; median age at transplantation was 35 years-old [28-42]. Patients had been previously treated with Hydroxycarbamide (92%) and/or chronic transfusion therapy (42%). Indications of HSCT were repetitive VOE in 83% and/or intra-cranial cerebral vasculopathy in 25% of patients. GF occurred in one S-beta0 Thal patient at 12 months (donor chimerism WBC at 17%; HbS at 35%) and VOEs reoccurrence. In this case, GF could be predicted by donor CD71+ chimerism at 1-month post-HSCT (20%) but not with donor chimerism measured at the same date in WBC (69%) and CD3 + (40%).

Median period of aplasia was 7.5 days [5.7-13.5] based on neutrophil count (>0.5×109/L); platelet count was never observed below 20x109/L. No VOE was observed except for the GF patient. Probabilities of EFS and OS at 6 months post-HSCT were 92% and 100%. One acute GVHD stade II was observed.

At 6 months post HSCT, median RBC and reticulocyte CD71+ donor chimerism was 99% [97-100] (n=12) and 98% [42-100] (n=12) respectively; median donor chimerism in total WBC was 87% [50-96] (n=12) and 23% [8-50] in CD3+ cells (n=10). Median HbS was 14.6% [0.8-36.3]. Hb was 11.8 g/dL [9.9-12.2] at 6 months of follow-up; reticulocyte count was 42x109/L [36-61]; LDH was 342 U/L [274-479]. Extended hemolysis panel at last follow-up 24.8 months [6.0-34.1] showed plasma free-Hb, heme and hemopexin median concentration at 4,4 µM (3.4-11), 0.15 µM (0.1-0.24) and 4.3 µM (1.4-8.8). Hemopexin was lower in partial engraftment group (p<0.05); no differences were observed between total and partial engraftment groups as regards to plasma free-Hb and heme concentrations (p>0.05).

Among HSCT with sustained donor cell engraftment at 6 months (n=11), total engraftment (donor CD71+ >80%) was observed in 9/11 (82%) with median donor chimerism in CD71+ at 99% [94-100], 100% [99-100] in RBC and 94% [84-97] in WBC. Two patients were considered as “partial” engraftment (donor CD71+ chimerism between 20-80%) with median donor chimerism of 28% in CD71+ (n=2), 95% in RBC (n=2) and 41% in WBC (n=2). Donor chimerism measured in RBCs was >95% in all patients included partial engraftment. Donor WBC chimerism was significantly correlated with donor CD71+ chimerism (r= 0.77; p<0.001).

Conclusion: Erythroid specific donor chimerism measured in immature CD71-positive reticulocytes could be a good predictor of engraftment in SCD patients who underwent an allogeneic non-myeloablative HSCT. Hemolytic-long-term follow-up is required especially in patients with partial engraftment.

Disclosures: De Luna: Pfizer: Other: Sponsor HEMOPROVE trial NCT05199766; Vertex: Consultancy. Habibi: Theravia: Honoraria; Novartis: Consultancy. Bartolucci: Innovhem: Other: Founder; Addmedica: Consultancy, Other: member advisory board; Bluebird: Consultancy; JazzPharma: Consultancy; Pfizer: Consultancy; Roche: Consultancy; Emmaus: Consultancy; Novartis: Consultancy, Other: member advisory board and member steering commitee.

*signifies non-member of ASH