Haploidentical BMT with a Post-Infusion of Stem Cells Cyclophosphamide Approach is Feasible and Leads to a High Rate of Donor Engraftment in Haemoglobinopathies Allowing Universal Application of Transplantation Vimal Kumar 1, Farah O’Boyle 1,2, Y. Harrington 1, A. Bradshaw 2, Sandra Hing 1,2, Marc Arca 1, Richard Szydlo 2, B. Inusa 3, P. Telfer 4, Leena Karnik 1,2 and J. de la Fuente 1,2 1 Department of Paediatrics, 2 Department of Haematology, Imperial College London, 3 Department of Paediatrics, Evelina Children's Hospital, 4 Department of Paediatrics, Royal London Hospital, London, United Kingdom

BACKGROUND  BMT is the only proven curative treatment available for haemoglobinopathies Role of Haploidentical BMT: Lack of HLA-matched related donors not suffering from the condition Limited number of unrelated donors available for the ethnic groups in which these conditions are prevalent [1]

Post transplantation Cyclophosphamide Modulates alloreactivity associated with partially matched donors in animals and humans [2] Highly toxic to lymphocytes but spares hematopoietic stem cells because of their high levels of aldehyde dehydrogenase Heightened cytotoxic sensitivity of proliferating, alloreactive T cells over nonalloreactive, resting T cells [3] Similar rates of GVHD and long-term immune reconstitution as seen with matched sibling donor BMT [4]

METHODS Study period : June 2013 to March 2016 at St Mary’s Hospital, London No. of haploidentical BMT: 23 children (18 HbSS, 5 β-Thalassaemia Major) Median age – 10 years (range 3 to 18 years) Donor – Parent (22 cases), Sibling (1 case) Criteria for considering haploidentical donor: No HLA matched related donor No 10/10 or 9/10 matched unrelated donor

Suppression of endogenous haemopoiesis Hyper transfusion (Hb for HbSS, for β thalassaemia) Hydroxycarbamide 30mg/kg + Azathioprine 3mg/kg (At least for 2 months pre-transplant)

METHODS CONDITIONING ATG 4.5mg/kg THIOTEPA 10mg/kg FLUDARABINE 150mg/m2 TBI 2Gy Cy 29mg/kgCy 100 mg/kg BM INFUSION SIROLIMUS MMF G-CSF

SOURCE OF STEM CELLS  G-CSF primed Bone marrow harvest Median TNC – 9.66 x 10 8 /kg (2.35 – x 10 8 /kg) Median CD34 – 3.46 x 10 6 /kg (1.12 – 9.21 x 10 6 /kg)

SUPPORTIVE CARE Anti-microbial prophylaxis: Ciprofloxacin, Aciclovir, Itraconzole, Pentamidine Irradiated blood products Viral monitoring: twice weekly CMV until day +90, then once weekly; once weekly adenovirus and EBV, twice weekly if PCR positive

RESULTS Total: 23 3 transplant related mortality D+36-primary graft failure, septic shock, meningitis D+90-secondary graft failure, sepsis, IPS D+148-IPS 20 cured Transfusion independent

RESULTS Neutrophil engraftment – Median: 17 days (range 15 – 29 days) Platelet engraftment – Median 35.5 days (range 20 – 64 days) Cessation of immune suppression – Median days Follow-up: Median 10.7 months (range 0.7 – 23 months) Increased incidence of infective complications, macrophage activation syndrome 1 child had VOD following autologous rescue for secondary graft failure

Acute GVHD Grade I – 7 patients (30.4%) >= Grade II – 2 patients (8.7%) Cumulative incidence of acute graft versus host disease ≥grade 2

Chronic GVHD Limited – 2 patients (8.7%)  Day +320 skin  Day +259 liver, treated with steroids Extensive – 3 patients (13%)  Day +187 lung, day +308 skin, day +320 musculoskeletal  Day +257 skin and liver  Day +180 gut, treated with MSC

D+28 CHIMERISM

D+180 CHIMERISM

RESULTS DFS: 87% OS: 87% Graft failure: 2 (8.7%) Mortality: 3 (13%) Kaplan-Meier curve showing OS (blue) and DFS (green), n=23

DISCUSSION Haploidentical transplantation with a post-infusion of stem cells cyclophosphamide, for young adults, whilst well tolerated, has resulted in high rates of rejection and need for prolonged immunosuppression [1] A more myelosuppressive approach by adding thiotepa, has resulted in better outcomes, reducing the graft failure rates with acceptable incidence of GVHD, albeit a long term follow up is needed.

CONCLUSION Related haploidentical transplantation providing sufficient myelosuppression to avoid rejection is feasible, leading to outcomes which approach the results for unrelated transplantation Allows all patients with haemoglobinopathies requiring a transplant to benefit from such treatment

REFERENCES 1.Bolaños-Meade J, Fuchs EJ, Luznik L, Lanzkron SM, Gamper CJ, Jones RJ, Brodsky RA. HLA-haploidentical bone marrow transplantation with posttransplant cyclophosphamide expands the donor pool for patients with sickle cell disease. Blood Nov 22;120(22): Brodsky RA, Luznik L, Bolan˜os-Meade J, Leffell MS, Jones RJ, Fuchs EJ. Reduced intensity HLA haploidentical BMT with post transplantation cyclophosphamide in nonmalignant hematologic diseases. Bone Marrow Transplant. 2008;42(8): Luznik L, Jones RJ, Fuchs EJ. High-dose cyclophosphamide for graft-versus-host disease prevention. Curr Opin Hematol. 2010;17(6): Luznik L, O’Donnell PV, Symons HJ, et al. HLA haploidentical bone marrow transplantation for hematologic malignancies using nonmyeloablative conditioning and high-dose, posttransplantation cyclophosphamide. Biol Blood Marrow Transplant. 2008;14(6):