Hematopoietic Cell Transplantation for Inborn Errors of Immunity Other Than Severe Combined Immunodeciency in Japan: Retrospective Analysis for 1985–2016

Purpose Hematopoietic cell transplantation (HCT) is a curative therapy for most patients with inborn errors of immunity (IEI). We conducted a nationwide study on HCT for patients with IEI other than severe combined immunodeciency (non-SCID) in Japan. Methods Data from the Japanese national database (Transplant Registry Unied Management Program, TRUMP) for 567 patients with non-SCID IEI, who underwent their rst HCT between 1985 and 2016, were retrospectively analyzed. Results was and The 10-year OS for from matched-sibling a of but robust engraftment. The with recovery, or retransplantation Multivariate analyses of data on those receiving HCT during the 2006–2016 period revealed that respiratory impairment at HCT was associated with poor OS (hazard P and than MSD were associated with poor EFS. acute GVHD and (h) chronic GVHD according to donor type are also shown. HCT, hematopoietic cell transplantation; MSD, matched sibling donor; URCB, unrelated cord blood; URBM, unrelated bone marrow; ORD, other related donor; CID, combined immunodeciency; WAS, Wiskott–Aldrich syndrome; HPS, hemophagocytic syndrome; PCD, phagocytic disorder; MAC, myeloablative conditioning; RIC, reduced-intensity conditioning; GVHD, graft-versus-host disease.


Introduction
Inborn errors of immunity (IEI) consist of heterogeneous hereditary disorders affecting various components of innate and acquired immunity including T and B lymphocytes, natural killer cells, phagocytes, macrophages, and complement proteins. Clinical manifestations of IEI are broad, such as susceptibility to serious or opportunistic infections, autoimmunity, autoin ammation, allergic diseases, lymphoproliferation, and malignancies. They are increasingly being de ned owing to recent advances in genetics and molecular sciences. In the most recent classi cation by the International Union of Immunological Societies (IUIS), 416 diseases have been enrolled as IEI [1]. In the present scenario, the collective prevalence of IEI is estimated to be at least 1 in 1,000 to 5,000 [2].
Hematopoietic cell transplantation (HCT) was rstly performed for a patient with severe combined immunode ciency (SCID) in 1968 [3]. Since then, HCT has been widely applied as a curative therapy for patients with IEI, especially for those with severe defects or dysregulation in cellular immunity. Unrelated cord blood (URCB) is commonly used in Japan and accounted for 33% of all allogenic HCTs during the period from 2009 to 2018 [4]. We previously performed a nationwide survey in Japan involving 88 patients with IEI who underwent unrelated cord blood transplantation (URCBT) and demonstrated an overall survival (OS) of 69% over 5 years [5]. However, no study has covered all HCTs for patients with IEI in Japan. Recently, we conducted a retrospective analysis of HCT for SCID in Japan. In this study, we conducted a nationwide retrospective analysis of HCT for patients with non-SCID IEI to provide an overview of the status and outcomes of HCTs and to develop strategies for HCT in Japan.

Data Collection
This study was approved by the Institutional Ethics Committee of Tokyo Medical and Dental University. The participants (and/or their guardians) provided written informed consents and were registered in the Transplant Registry Uni ed Management Program (TRUMP), an electronic database of all HCTs performed in Japan established by the Japanese Society for Transplantation and Cellular Therapy (JSTCT) [6]. The patients with non-SCID IEI who underwent their rst HCT were included. The diagnoses of patients were collected according to the IUIS 2017 classi cation [7]. All transplant data were obtained from the TRUMP.

Study Endpoints
Event-free survival (EFS), de ned as the period from HCT to death or retransplantation, was calculated to assess survival without graft failure. The diseases were classi ed into the following categories: combined immunode ciency (CID; CD40 ligand de ciency, DOCK8 de ciency, ZAP-70 de ciency, bare lymphocyte syndrome, and unspeci ed CID), Wiskott-Aldrich syndrome (WAS), hemophagocytic syndrome (familial hemophagocytic lymphohistiocytosis (FHL), Chediak-Higashi syndrome, and X-linked lymphoproliferative disease), phagocytic disorder (chronic granulomatous disease [CGD], severe congenital neutropenia [SCN], leukocyte adhesion de ciency, Shwachman-Diamond syndrome, and GATA2 de ciency), and others (see Tables 1 and S1). The conditioning regimens were classi ed into myeloablative conditioning (MAC) and reduced-intensity conditioning (RIC). Regimens containing one of the following were classi ed as MAC; total-body irradiation at a total dose of ≥ 800 cGy, busulfan at a total dose of ≥12 mg/kg, or melphalan at a total dose of ≥150 mg/m 2 , according to the Center for International Blood and Marrow Transplant Research criteria [8] and previous studies [9,10]. Other regimens were classi ed as RIC, including those in which the patient did not receive any chemotherapy or radiation. HLA matching was determined by serology for patients from the initial years and by genotype for those in the more recent years. We used the term "matched" to refer to those 8/8, or 6/6 matched and who lacked the HLA-C loci data, especially among patients from the initial years. The donor type was de ned as follows: matched sibling donor (MSD), other related donor (ORD), URCB, and unrelated bone marrow (URBM). Neutrophil recovery was de ned as the achievement of an absolute neutrophil count of ≥0.5×10 9 /L for 3 consecutive days. Platelet recovery was The HCT from MSD accounted for 117 (21%) cases. Among 376 (66%) cases of HCT from unrelated donors, 157 (28%) were URCB and 219 (39%) were URBM. All URCBTs were a single unit. Among 61 (11%) cases of HCT from ORD, 2 patients (CGD and CTLA4 de ciency) received post-transplant cyclophosphamide, and none received TCRαβ + /CD19 + depletion. The presence of respiratory impairment at HCT was observed in 41 (9%) cases whereas active bacterial or fungal infection at HCT was noted in 95 (21%) cases. There was a strong correlation between respiratory impairment and bacterial or fungal infection at HCT (P < 0.001).
Notably, more patients received RIC, tacrolimus, and URBM as a donor source than the others, and patients with phagocytic disorder received HCT more frequently than the other categories in the later period (Table  S2).

Overall Survival and Event-free Survival
The summary of the transplant outcomes over the entire period is shown in Table 2. The OS and the EFS for 10 years were 74% [69-78%] and 64% [60-69%], respectively. We did not observe any signi cant difference over time in OS or EFS (Fig. 1a, b).
There were signi cant differences in 10-year OS because of respiratory impairment at HCT (61% [41%-75%] for patients with respiratory impairment vs. 78% [73-83%] for those without, Fig. 1c, P = 0.01), but not because of bacterial or fungal infection at HCT, or because of conditioning (Fig. 1d, Fig. 1g). The patients with hemophagocytic syndrome (65% [55-73%]) had worse OS than those with other disease categories (Fig. 1h). We did not observe any statistical difference in OS according to HLA disparities in URBM, as well as in URCB (Fig. S2a, b). Additional survival curves in each disease category are shown in Fig S3 a- Fig. S2c). The HLA disparities in URCBT were associated with a tendency for higher incidence of retransplantation ( Fig. S2d). Patients with hemophagocytic syndrome had slower hematologic recovery than those with other diseases (neutrophil recovery at day 60: 87% [79-92%]; P = 0.06; Fig. 2c; platelet recovery at day 60: 63% [54-71%]; P < 0.001; Fig. 2d); however, they did not show any signi cant difference in the cumulative incidence of retransplantation (Fig. S4b). Platelet recovery was faster in the patients who received RIC conditioning, although retransplantation was not correlated with the intensity of conditioning (Fig. 2 f, and Fig. S4c). We added the analyses for retransplantation in each disease category ( Fig. S3 g-l), and found that URCBT was associated with a higher incidence of retransplantation in patients with hemophagocytic syndrome (P = 0.03) or phagocytic disorder (P < 0.001), but not in those with WAS. The intensity of conditioning regimen was not associated with any signi cant difference in the incidence of retransplantation in each of the disease categories.

Chimerism
More robust donor chimerism was achieved in patients who received HCT from MSD or URBM than in those who received HCT from ORD or URCB (Fig. S5a). The donor dominance in chimerism was not signi cantly different between MAC and RIC regimens (Fig. S5b). The HLA disparity in URBM or URCB, and disease category did not show a signi cant difference in terms of donor chimerism (data not shown).
Other HCT-related complications are shown in Table 4. Among the patients evaluated, viral and fungal infection was observed in 21% and 12%, respectively. URCBT was signi cantly associated with a higher incidence of post-HCT bacterial infection (P = 0.03), but not with post-HCT viral infection (Table S4). In terms of long-term toxicities, 14 (3%) patients developed malignancy, most of which were associated with post-transplant lymphoproliferation. Short stature was most commonly seen, occurring in 19% of the patients. We did not observe statistical association of MAC regimens and the incidence of these complications (data not shown).

Cause of Death
Death from infection was the most common, accounting for 43 (33%) cases (Table 5). Among the patients who died, MAC regimen was commonly associated with death from infection (P = 0.0496, Table S5). The donor type or disease category was not correlated with differences in the cause of death (data not shown).
We demonstrated the effect of URBM and URCB on the outcome of HCT for non-SCID IEI in Japan. The HCT from URBM was the most frequently performed, showing comparable 10-year OS to that for HCT from MSD (79% vs 81%, respectively). The equivalent outcome for HCT from URBM and MSD has also been reported from other countries [12,13]. Although the incidence of aGVHD was high with HCT from URBM, the excellent survival was partly due to robust hematologic recovery, low retransplantation incidence, and su cient donor chimerism. The preparation for HCT from URBM takes several months in Japan and is not suitable for urgent transplantation, but our analysis recon rms that URBM can be considered as a useful alternative donor source for stable patients who have enough time to prepare for HCT.
The OS for URCBT over 10 years was 69%. Although the OS was inferior to that for HCT from MSD, this might be acceptable for patients who require urgent transplantation and do not have MSD. A similar incidence of GVHD in URCBT and HCT from MSD also suggested its utility in Japan. However, the engraftment after URCBT was not robust, as evident from a slow hematologic recovery, high retransplantation incidence, and low donor chimerism. Furthermore, multivariate analyses demonstrated that URCB was an independent risk for poor EFS and retransplantation. Although URCBT for SCID patients in Japan showed excellent outcome, including OS, hematologic recovery, and stable engraftment [submitted], the disadvantage for engraftment is well known in the HCT for hematologic disorders other than SCID [16][17][18][19][20]. Despite the ready availability and feasibility of URCBT, we recognize the risk for poor engraftment for non-SCID IEI as a whole.
For patients who received HCT from ORD, we observed a poor OS/EFS, as well as poor engraftment and a high incidence of cGVHD. In our cohort, post-transplant cyclophosphamide or TCRαβ + /CD19 + depletion, Page 9/30 which are beginning to be adopted in haploidentical HCTs for IEIs worldwide [21][22][23][24][25][26] as well as in Japan [27], was not used in most of the cases. The introduction of these novel techniques can expectedly help exploit more available donors and also improve the outcome of HCT from ORD in the coming decades. Furthermore, gene therapy (GT) for numerous IEIs, including SCID, WAS, CGD, and leukocyte adhesion de ciency, is being developed [28]. Promising results for these novel approaches should improve the prognosis of IEI patients without suitable donors.
We analyzed the association of conditioning regimens and the outcomes of HCT. In the recent decade, RIC regimens have been commonly chosen. The OS, retransplantation incidence, and donor chimerism for RIC regimens were not signi cantly different from those for MAC regimens, indicating su cient e cacy of RIC regimens. This was also true in the analysis for each disease category. Although we did not observe a difference in HCT-related complications between the two regimens, MAC regimens were more commonly associated with death from infection; and we speculate that strong tissue injury associated with MAC, such as mucosal damage, probably contributed to it. RIC regimens potentially reduce short-and/or long-term conditioning-related toxicities and are considered suitable in HCT for IEI.
We also demonstrate that respiratory impairment at HCT was an independent risk for OS. The strong association between respiratory impairment and infection implied that the infection was responsible for dyspnea in most of the patients. Unlike for SCID patients in western countries [10,12] and Japan [submitted], the presence of infection alone was not associated with poor survival, but infection and subsequent pulmonary damage could be a risk. The management of non-infectious manifestations is equally important as the control of infectious events before HCT. For instance, it is well known that the remission status of hemophagocytic syndrome is associated with good survival after HCT [29,30]. Several targeted therapies have been developed for IEI in recent years, such as anti-interferon-γ antibody for hemophagocytic lymphohistiocytosis [31], JAK inhibitor for hemophagocytic lymphohistiocytosis [32], or STAT1 or STAT3 gain-of-function [33], CTLA4-Fc fusion protein for CTLA4 haploinsu ciency [34] or LRBA de ciency [35], and PI3K inhibitor for activated PI3Kδ syndrome [36]. Those novel pharmacological treatments are expected to control the disease activity as bridging therapies before HCT.
Besides the results for non-SCID IEI as a whole, IEI comprises heterogeneous diseases and each disorder is associated with a different background of the patients (Fig. S1 and Table S1) or outcome of HCT (Fig. S3).
In patients with WAS, the similar outcomes for URBM and MSD con rmed that URBM was preferable as an alternative donor. We also show that OS or incidence of retransplantation after URCBT for WAS patients was not different from that for HCT from MSD, suggesting the potential of URCB as a candidate donor as well.
The availability of URCB for WAS patients was consistent with the nding from studies from western countries [37,38]. Busulfan-based RIC regimen is effective for WAS patients in terms of survival and donor engraftment [37], and our results are consistent with this nding.
The interval between diagnosis and HCT was the shortest for patients with hemophagocytic syndrome compared with that for patients with other diseases, indicating the urgency for HCT. URCB was the most commonly chosen for these diseases probably owing to rapid availability. The 10-year OS for URCBT was 58%, which was similar to that reported from Europe [39] and Japan [40]; however, it was not satisfactorily compared to the 10-year OS for HCT from MSD (79%), and the incidence of retransplantation was higher in URCBT than for HCT from MSD. Further approaches, including optimal conditioning regimen, exploring indication of haplo-HCT with post-transplant cyclophosphamide [41], or better pre-HCT disease control using molecular-targeted therapies [31,32], would be necessary for improving the management of HCT in the coming decades.
In patients with phagocytic disorder, the outcome for HCT from URBM and MSD was equivalent. Moreover, this disease category showed a risk for retransplantation as well as poor EFS, and URCBT for these diseases showed a signi cant risk for retransplantation. The patients were more commonly complicated with infection or respiratory impairment at HCT (Table S1), which may also pose a risk for infection, concerning poor engraftment in URCBT. URCBT for CGD patients is reported to have poor engraftment in studies from Japan [42] and European countries [43], which is consistent with our results. Because the time between diagnosis and HCT was relatively long and urgent HCT is considered rare, URCB may be used for these diseases only on limited occasions. We also observed the non-inferiority of the RIC regimen to MAC regimen for phagocytic disorders. Recently, the prospective clinical trials have shown that a udarabine/busulfanbased RIC regimen is effective in CGD patients [44,45]. To reduce regimen-related toxicity, especially in recipients with concomitant infection, RIC is recommended for these diseases.
We provided some insights for preferred management of HCT for some disease categories. To establish a better disease-speci c management, it is important to conduct a precise evaluation for each disease through retrospective analyses, or possibly through prospective studies. Moreover, novel therapeutic modalities including GVHD prophylaxis, GT, or molecular targeted approaches are being established with a su cient number of patients, requiring revision of the current strategies for each IEI.
Our study has several limitations. First, some important information, such as precise genotype of the diseases was not available in the TRUMP registry for the patients who received HCT in the earlier period, which might have reduced the sample size and affected the analyses. Second, the TRUMP registry was not oriented for the HCT for IEI; some disease-speci c complications that might affect the outcome of HCT were missing (e.g., colitis for WAS, CGD, or XIAP de ciency, and autoimmunity for WAS or CTLA4 haploinsu ciency). The data of immunologic reconstitution after HCT, such as lineage speci c chimerism or discontinuation of immunoglobulin were also unavailable. Third, a precise analysis of each disease was not performed. For further detailed analysis, we have already published retrospective studies for each IEI from Japan [42,46,47] and will also perform such studies for other diseases in the future on behalf of the Hereditary Disorder Working Group of the JSTCT, collaborating with the Primary Immunode ciency Database in Japan [48] and the TRUMP.
In conclusion, we present an overview of the backgrounds and outcome of HCT for non-SCID IEIs in Japan with a large number of patients for su cient statistical power. We demonstrate that the OS for HCT from URBM and MSD was almost equivalent in Japan, con rming URBM as an alternative donor source in HCT for non-SCID IEI. URCBT, which was also commonly performed in Japan, showed substantial applicability for some diseases but has a high risk for poor engraftment. We also demonstrate the e cacy of RIC regimens and highlight the importance of disease control before HCT. These results should contribute to the development of future management strategies for IEIs in Japan. Furthermore, detailed evaluation for individual IEI, along with recent advances in novel therapeutic approaches, needs to be addressed for establishing an optimal HCT strategy for each disease. Con icts of interest/Competing interests: All authors declare that there are no con icts of interest to disclose concerning this study.
Ethics approval: The studies involving human participants were reviewed and approved by the Institutional Review Boards at the Japanese Society for Transplantation and Cellular Therapy (JSTCT) and Tokyo Medical and Dental University.
Consent to participate/publication: All participants (and/or their guardians) provided written informed consent for research use of their data and publication.
Availability of data and material: The datasets presented in this article are not readily available because they belong to the JSTCT and the Japanese Data Center for Hematopoietic Cell Transplantation (JDCHCT).
Requests to access the datasets should be directed to http://www.jdchct.or.jp/.
Code availability: All statistical analyses were performed using the Stata software v16.1 and EZR 1.42.

Acknowledgment
We thank the Japan Marrow Donor Program, the cord blood banks in Japan, and the staff at the participating hospitals who attended to the patients and provided information for the TRUMP registry. We also thank Soichi Adachi, Shunichi Kato, Yasuo Horikoshi, Miharu Yabe, Nao Yoshida, Hiromitsu Takakura   a These diseases were classi ed as "combined immunode ciency" in this study.
b Two patients were registered as "X-linked thrombocytopenia" in the TRUMP and classi ed as "WAS" in this study.
c These diseases were classi ed as "others" in this study. d These diseases were classi ed as "hemophagocytic syndrome" in this study. e These diseases were classi ed as "phagocytic cell disorder" in this study.
No., number; def., de ciency; CID, combined immunode ciency; XLP, X-linked lymphoproliferative disease; EDA-ID, Anhidrotic ectodermal dysplasia with Immunode ciency; GOF, gain of function     Cumulative incidence of hematologic recovery and graft-versus-host disease The cumulative incidences of neutrophil recovery and platelet recovery according to (a and b, respectively) donor type, (c and d, respectively) disease category, and (e and f, respectively) conditioning regimen are shown. The patients who received no conditioning were excluded from these analyses. The cumulative incidences of (g) grade II-IV acute GVHD and (h) chronic GVHD according to donor type are also shown. HCT, hematopoietic cell transplantation; MSD, matched sibling donor; URCB, unrelated cord blood; URBM, unrelated bone marrow; ORD, other related donor; CID, combined immunode ciency; WAS, Wiskott-Aldrich syndrome; HPS, hemophagocytic syndrome; PCD, phagocytic disorder; MAC, myeloablative conditioning; RIC, reducedintensity conditioning; GVHD, graft-versus-host disease.

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