Successful unrelated umbilical cord bloodtransplantation for class 3 b-thalassemiamajor using a reduced-toxicity regimen

Soni S, Breslin N, Cheerva A. Successful unrelated umbilical cordblood transplantation for class 3 b-thalassemia major using a reduced-toxicity regimen.

Abstract: Unrelated umbilical CB transplant for class 3 b-thalassemiamajor is associated with an increased risk of mortality and non-engraftment. We describe two patients who underwent successfulunrelated umbilical CB transplant using a novel reduced-toxicitypreparative regimen. This regimen may be sufficientlyimmunosuppressive and myeloablative to ensure engraftment withreduced risks of toxicity and mortality. Close monitoring of HHV-6viral load is advised for patients undergoing transplant with thisregimen.

Sandeep Soni1, Nancy Breslin2 andAlexandra Cheerva21Division of Heme/Onc/BMT, Nationwide Children’sHospital, The Ohio State University, Columbus, OH,USA, 2Division of Heme/Onc/BMT, Kosair Children’sHospital, University of Louisville, Louisville, KY, USA

Key words: thalassemia major – stem celltransplant – umbilical cord blood

Sandeep Soni, Director of Hematology/BMT,bluebird bio, Inc., 840 Memorial Dr. Cambridge, MA02139, USATel.: 617 588 3386Fax: 617 576 2421E-mail: ssoni@bluebirdbio.com

Accepted for publication 31 October 2013

Allogeneic HSCT is the only curative therapycurrently available for b-thalassemia major.According to the Pesaro classification, patientswith transfusion-dependent thalassemia majorcan be categorized into three classes based onrisk for HSCT (1). Patients classified as class 3have pre-existing evidence of organ damage fromtransfusion related iron overload and are morelikely to experience TRM and failure of donorengraftment (2, 3). Also an OS of 62% and a dis-mal DFS of 21% have been reported for childrenundergoing unrelated CB transplants in a largeregistry study (4). Primary graft failure was themain cause of treatment failure occurring in 20of 35 patients with thalassemia and was also themajor cause of TRM.Non-myeloablative and RIC regimens are only

partially successful in HSCT for b-thalassemia

major, as the decrease in the incidence of TRMis often offset by an increased risk of primaryand secondary graft failures (5–7). Increased my-eloablation and immunosuppression to ensureengraftment increase the risk of toxicity, infec-tions and TRM. Also, the long-term effects ofincreased intensity of myeloablative and immu-nosuppressive regimens on organs and fertilityare well known. Therefore, a reduced-toxicityregimen that leads to durable engraftment withCB is required for greater acceptance of unre-lated donor HSCT for hemoglobinopathies.In the current report, we describe two patients

with class 3 b-thalassemia major (based on irreg-ular chelation and presence of portal fibrosis onpretransplant liver biopsy) who were successfullytransplanted with CB using a reduced-toxicityregimen described in Fig. 1.

Abbreviations: ANC, absolute neutrophil count; CB, cordblood; DFS, disease-free survival; G-CSF, Granulocyte col-ony-stimulating factor; GM-CSF, granulocyte macrophagecolony-stimulating factor; GVHD, graft versus host disease;HHV-6, human herpes virus 6; HSCT, hematopoietic stemcell transplantation; MMF, mycophenolate mofetil; OS,overall survival; RIC, reduced-intensity conditioning; TNC,total nucleated cell count; TRM, transplant relatedmortality.

Days pre-infusion–21–20–19 –8–7–6–5–4 –3 –2 0

Fludarabine 30 mg/m2 x 5 daysAlemtuzumab 48 mg total Thiotepa 10 mg/kg on day –3

Melphalan 140 mg/m2 on day –2

Fig. 1. Conditioning regimen.

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Pediatr Transplantation 2014: 18: E41–E43 © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Pediatric TransplantationDOI: 10.1111/petr.12201

Case 1

A five-yr-old girl of Laotian origin (CMV IgG+),who was receiving chronic transfusions sinceone yr of age and in Pesaro stage 3. She receiveda reduced-intensity regimen consisting of fludara-bine (150 mg/m2), melphalan (140 mg/m2) andrabbit-ATG (thymoglobulin, three doses,2.5 mg/kg/dose) and received an unrelated CBinfusion (6/6 HLA match, TNC 3.8 9 107/kg).Although the transplant course was uneventful,she had autologous recovery and was 100% reci-pient on day +44. After a gap of nine months,she underwent a second HSCT with the prepara-tive regimen as outlined in Fig. 1. She receivedanother 6/6 matched unrelated CB unit with acell dose of TNC 7.6 9 107/kg and CD34+ of2 9 105/kg in December of 2004. GVHD pro-phylaxis consisted of tacrolimus and MMF.GM-CSF was administered starting day +1 untilANC was >3000. She tolerated the regimen wellwithout any major organ toxicity. She developedfever and skin rash on day +12 that was attrib-uted to HHV-6 reactivation (PCR method), andshe received iv foscarnet for 14 days (Fig. 2). NoCMV, EBV, adenovirus and BK virus reactiva-tions were detected on serial monitoring. Neutro-phil and platelet engraftment occurred on days+23 and day +34, respectively. She was 100%donor on day +30 (RFLP analysis). No acuteGVHD was noted, and MMF was stopped onday +60. Tacrolimus was tapered and discontin-ued by day +100. She was continued on a post-transplant prophylaxis regimen of voriconazole,valgancyclovir (in view of HHV-6 reactivation),penicillin and dapsone till day +100, when theresults of immune reconstitution studies showedher CD3, CD4 and CD8 counts to have recov-ered (CD3 2321, CD4 571, CD8 1750/mm3).Subcutaneous desferal and phlebotomy werecontinued post-transplant until the ferritin levels

decreased to <2000 ng/mL. No chronic GVHDwas noted on follow-up. She remains transfusionindependent and maintains 100% donor statuseight yr post-transplant. No major long-termtoxicities have been observed.

Case 2

A seven-yr-old boy (CMV IgG+) of Chinese ori-gin, transfusion dependent since 10 months of ageand Pesaro class 3, who underwent an allogeneicHSCT using the same preparative regimen(Fig. 1). A 5/6 matched (mismatch at HLA Blocus) unrelated umbilical CB unit (TNC4.2 9 107/kg and CD34 + 2.2 9 105/kg) wasinfused in November of 2006. GVHD prophylaxiswas with tacrolimus and MMF, and G-CSF wasgiven starting day +1 until ANC >3000 wasachieved. He also tolerated the regimen well withno organ toxicities and minimal mucositis.Increased HHV-6 viral copies were noted on day+11, and this was preemptively treated with intra-venous foscarnet for seven days (Fig. 2). Neutro-phil and platelet engraftment was achieved on day+18 and on day +32, respectively. He was 100%donor on day +30 (RFLP) and has maintainedcomplete donor chimerism since then. No evi-dence of GVHD was noted, and MMF wasstopped on day +30; tacrolimus was tapered andstopped by day +120; immune reconstitution wascomplete on day +130 (based on CD3/CD4 andCD8 quantitative estimates). A post-transplantregimen of desferral and phlebotomy was contin-ued for one yr for iron overload. He also remainstransfusion independent and maintains 100%donor chimerism six yr post-transplant, with nomajor long-term toxicities.

Discussion

Increased incidence of rejection is well known inHSCT for class 3 b-thalassemia major, especiallyin the unrelated donor setting, with RIC regi-mens and with the use of CB. Difficulty inengraftment of unrelated donor cells is thoughtto be due to several factors including:

1 Increased antibody production (anti-HLAantibodies) and persistent B-cell clones due torepeated transfusion exposure (8).

2 Increased erythroid compartment due to “ex-tramedullary hematopoiesis” and thereforedifficulty in completely eradicating the recipi-ent myeloid compartment, especially withreduced-intensity regimens (6, 7).

Attempt to overcome this resistance by increas-ing myeloablation and immunosuppression

0100 000200 000300 000400 000500 000600 000700 000800 000900 000

1 000 000

9 2 5 12 15 19 21 27 35 47 60– –

Cop

ies

Days

HHV-6 PCR

i.v Foscarnet start day

Patient 1Patient 2

Fig. 2. HHV-6 titers and response to treatment.

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Soni et al.

results in high TRM due to organ toxicity andinfections, especially in the unrelated donor set-ting (9, 10).The core part of the regimen has been pub-

lished previously by Shenoy et al. (11) We hadadded thiotepa to the preparative regimen toincrease the myeloablative and immunosuppres-sive potential. Alemtuzumab given early on day�21 in this protocol depletes host T, NK and Bcells and hence may improve engraftment bydecreasing the pool of preformed alloantibodiesthat mediate rejection. With the early administra-tion of alemtuzumab, the immune reconstitutionis not delayed post-HSCT, as the blood levels ofalemtuzumab are undetectable on day 0 of theHSCT, resulting in minimal in vivo depletion ofdonor T or B cells.Both melphalan and thiotepa were added to

the regimen to effectively eradicate the myeloidcompartment using two agents at reduced dosesbut with non-overlapping toxicities. Therefore,this regimen is effectively myeloablative, but withreduced toxicity. Both patients tolerated the regi-men well without any immediate and long-termtoxicities on follow-up.The major complication of alemtuzumab and

fludarabine combination for effective recipientimmunosuppression was the viral reactivation,especially HHV-6 virus. Both the patients wereHHV-6 IgG positive prior to transplant andtherefore we monitored them closely for HHV-6reactivation by quantitative PCR assay (Viracor,Kansas City, KS, USA). Both the patients devel-oped HHV-6 reactivation early in the course oftransplant. Patients were given iv foscarnet (priorto engraftment) and then switched to valganci-clovir as soon as they were able to tolerate oralmedications. This may also be the reason for lowincidence of CMV or adenovirus reactivations inboth these patients.This regimen is very well tolerated with mini-

mal toxicity and risk of TRM and may be suffi-ciently myeloablative and immunosuppressive toensure long-term donor engraftment in class 3 b-thalassemia major patients using unrelated CB

with adequate cell doses. A multicenter study iscurrently underway to investigate the feasibilityand outcomes of a similar regimen (NCT01005576) for thalassemia.

Authors’ contributions

SS designed the protocol and wrote the initial draft, NB wasinvolved in data collection and AC reviewed the manu-script.

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