Methods
Ten pediatric patients with TM (5 males and 5 females, 5 - 14 years old)
were enrolled in the study (Table 1). The study was done in accordance
with the principles of Good Clinical Practice, the Declaration of
Helsinki, and all local regulations (approved by the Independent Ethics
Committee of the Dmitry Rogachev National Medical Research Center of
Pediatric Hematology, Oncology and Immunology. All of the parents of the
patients signed a written informed consent).
The inclusion criteria were as follows: an established diagnosis of TM,
a high blood transfusion-dependency (at least one unit of RBC every 2-3
weeks for at least 1 year) and an enlarged spleen.
The exclusion criteria were as follows: platelet count < 75 ×
109/L, an absolute neutrophil count < 1.5 ×
109/L; a cardiac ejection fraction of < 50%
or impaired renal, hepatic or gastrointestinal functions.
All patients were heavily transfused and had moderately severe iron
overload. Liver iron concentration was measured by MRI (GE Signa 1.5).
Chelation therapy continued during the study. All patients had very low
pre-transfusion Hb level (<80 g/L) before enrolling in this
study, heralding severe IE.
The dose of ruxolitinib was age-adjusted and based on previously
published reports on ruxolitinib pharmacokinetics in children: for
patients younger than 11 years it was 40-100 mg/m2total dose three times daily; for patients older than 12 years it was 20
- 30 mg/m2 total dose twice daily. Toxicities were
graded according to the Common Terminology Criteria for Adverse Events
version 4.0 (http://ctep.cancer.gov).
Eight patients received ruxolitinib for 6 months, while patient 1 and 9
received ruxolitinib for 1 and 1.5 years, respectively.
HSCT was performed in 8 out of 10 patients. The source of stem cells was
bone marrow from matched sibling donor (MSD; n = 2), bone marrow from
matched unrelated donor (MUD; n = 1) and peripheral blood from MUD (n=1)
or haploidentical related donor (MMRD; n = 2). Two of the patients (2
and 4) have not received HSCT.
Conditioning regimen for the first transplant was treosulfan (42
g/m2 total dose; days -4, -3 and -2), thiotepa and
(300 mg/m2 total dose; day - 5) and fludarabine (150
mg/m2 total dose; days -5, -4, -3, and -2). In
addition patients received serotherapy with rabbit antithymocyte
globulin (ATG;) (5 mg/kg total dose); days -5 and -4). On day -7 and - 1
patients received 375 mg/m2 rituximab for reducing the
risk of Epstein-Barr virus related post-transplant lymphoproliferative
disease. Grafts from MUD and MMRD (n=5) were
TCRab+/CD19+ depleted by using an
immunomagnetic method in accordance with the manufacturer’s instructions
(Miltenyi Biotec, Bergisch Gladbach, Germany). Donor-specific anti-HLA
antibodies were not detected in any of patients.
A decrease in spleen volume as assessed by MRI was chosen as the main
criterion of ruxolitinib suppression of IE. Additional efficacy criteria
were as follows: a decrease of soluble transferrin receptor (sTfR)
concentration, a decline in proerythroblast (CD45-/CD71+/CD117+) and
erythroblast (CD45-/CD71+/CD235+) count in the bone marrow, assessed by
flow cytometry. Data obtained from previously published studies were
used for interpreting the results.27-29 Also
percentage changes of RBC transfusion volume (ml/kg) which was required
to maintain Hb at 11.0 – 12.0 g/L compared to baseline and graft
failure/rejection rate were used for efficacy evaluation.