BackgroundAllogeneic HSCT from either an HLA-identical sibling or an unrelated donor is a potentially curative treatment for patients with hemoglobinopathies and erythroid disorders (ED), such as Thalassemia Major (TM), Sickle Cell Disease (SCD) and Diamond-Blackfan Anemia (DBA). Bertaina et al (Blood, 2014) have previously shown that α/β TCR T cell depleted haplo-transplantation in children with multiple types of non-malignant disorders was feasible. An ongoing Phase I/II trial evaluates the safety and effi cacy of post-transplant infusion of donor T-cells transduced with the iC9 suicide gene (BPX-501 cells) in order to further optimize the recovery of adaptive immunity, (ClinicalTrials.gov identifi er: NCT02065869). The iC9 gene contains sequence for the CD19 marker, so that the BPX-501 cells (CD3+/CD19+) can be easily tracked in peripheral blood. We report on 12 children with hemoglobinopathies, sickle cell disease and Diamond Blackfan Anemia treated at OPBG.

Methods and TechnologyAll patients were transplanted from a carrier parent. Median number of CD34+ and αβ+ T-cells infused was 22.5 x 106/kg and 0.3 x 105/kg, respectively. In all patients, conditioning regimen included i.v. busulfan (dose adjusted according to weight), thiotepa (10 mg/Kg) and fl udarabine (160 mg/m2). Rabbit ATG (12 mg/Kg over 3 days, from day -4 to day -2) was administered to prevent graft-versus-host disease (GvHD) and graft failure and Rituximab (200 mg/m2 on day -1) was administered to prevent EBV-related lymphoproliferative disorders. No post-transplantation pharmacological GvHD prophylaxis was given. Median follow-up is 301 days (range 41-420 days). Basic phenotyping of circulating lymphocytes was assessed by fl ow cytometry on fresh heparinized peripheral blood samples at 10, 20, 30, 60, 90, 120 and 150 days post haplo-HSCT.

Demographics

Demographics■ Five patients were males and 7 were females.■ Median age at HSCT was 7.9 years (range 2.5-11.9). ■ 2 patients had DBA and 1 had SCD. ■ All 9 TM patients were β0/β0. ■ All 12 patients were transfusion-dependent and receiving iron-chelation

therapy before haplo-HSCT.

BPX-501 Technology■ GMP BPX-501 T cells are derived from non-mobilized donor leukapheresis and

are expanded, transduced and selected for the iC9 gene, cryopreserved and shipped back to the clinical site.

Haplo-Transplant Outcome■ 11/12 patients maintained full donor chimerism. The patient with secondary graft

failure was re-transplanted from the same donor, attaining full donor chimerism. ■ No TRM – all patients alive and well.■ Initial discharge at median of 21 days (14-55) and there were no re-

hospitalizations.■ Grade I/II skin acute GvHD occurred in 2 patients (31 & 59 days after HSCT,

respectively, which was successfully treated with steroids) and no chronic GVHD occurred.

Hematopoietic Recovery■ Median time to neutrophil recovery was 14 days (range 11-32 days). ■ Median time to platelet recovery was 11 days (range 9-12 days). ■ Median time to last RBC transfusion was 6.5 days (4 – 33 days).

Hemoglobin Levels

Immune Reconstitution■ Median time of infusion of 1x106 BPX-501 T cells/kg was 14 days after HSCT

(range 10-26). ■ BPX-501 cells expanded after infusion and still persist in all patients.■ Immune reconstitution with normal cellular and humoral immunity at

180 days.

ConclusionsChildren with hemoglobinopathies, sickle cell disease and DBA can benefi t from curative haplo-HSCT after depletion of α/β T-cells followed by infusion of BPX-501 cells, which, expanding and persisting over time, contribute to the overall immune reconstitution and transplant outcomes.

Clinical outcome and immune recovery aft er adopti ve infusion of BPX-501 cells (donor T cells transduced with iC9 suicide gene) in children with Hemoglobinopathies and Diamond-Blackfan

Anemia given α/β T-cell depleted HLA-haploidenti cal stem cell transplantati on (HSCT)Bertaina A, Merli P, Pagliara D, Li Pira G, De Angelis B, Brescia LP, Strocchio L, Del Bufalo F, Montanari M, Lucarelli B, Algeri M, Moseley A, Locatelli F.

1250

Time from HSCT (days)

cell

s/m

cl

1000

750

500

250

030 90 180 270 360

30 90 180 270 360

30 90 180 270 360

CD3+

1000

Time from HSCT (days)

500

-250

CD3+ Subsets

50

Time from HSCT (days)

cell

s/m

cl

20

-10

CD3+ CD19+

CD4+CD8+

cell

s/m

cl

40

30

0

10

750

0

250

IgA

Ig Level (mg/dL)0 200 400 600 800

IgGIgMIgAIgGIgM

IgAIgGIgM

35

35

35

500

500

500

6 M

on

th9

Mo

nth

12 M

on

th

Time Point Median HgB (g/dL) Range

At Discharge 9.1 (7.0 - 11.4)

100 days 10.5 (9.8 - 13.9)

180 days 11 (10.1 - 13.4)

Bertaina A, Merli P, Pagliara D, Li Pira G, De Angelis B, Brescia LP, Strocchio L, Del Bufalo F, Montanari M, Lucarelli B, Algeri M, Locatelli F. (Ospedale Pediatricio Bambino Gesu)There are no relevant confl icts of interest to disclose.Moseley A –Bellicum Pharmaceuti cals

All patients who have reached 6 month follow-up remain transfusion free with median hemoglobin of 11 g/dL (range 10-13).

Patient 016Patient 032Patient 047Patient 061Patient 025Patient 034Patient 051Patient 066Patient 026Patient 036Patient 058

16

Time from HSCT (days)

g/dL

14

10

8

4

10 30 60 90 100

12

6

0

2

180 270 360

Patient 075

Subject Age (Yrs) Diagnosis

016 11 THALASSEMIA MAJOR

025 10 THALASSEMIA MAJOR

026 10 THALASSEMIA MAJOR

032 3 SICKLE CELL DISEASE

034 3 THALASSEMIA MAJOR

036 9 DIAMOND BLACKFAN ANEMIA

047 8 THALASSEMIA MAJOR

051 5 THALASSEMIA MAJOR

058 9 THALASSEMIA MAJOR

061 4 DIAMOND BLACKFAN ANEMIA

066 2 THALASSEMIA MAJOR

075 5 THALASSEMIA MAJOR