Second allogeneic hematopoietic stem cell transplantation in patients with inborn errors of immunity

Rationale, implementation considerations, delineation and planning target objective recommendations for volumetric modulated arc therapy and helical tomotherapy total body irradiation, total marrow irradiation, total marrow and lymphoid irradiation and total lymphoid irradiation

As a component of myeloablative conditioning before allogeneic hematopoietic stem cell transplantation (HSCT), Total Body Irradiation (TBI) is employed in radiotherapy centers all over the world. In recent and coming years, many centers are changing their TBI setup to a conformal isocentric technique, providing superior homogeneity and control of the target prescription dose, and more freedom for individualized organ-at-risk sparing or dose-escalation. Also, more specifically bone-marrow- and/or lymphatics-targeted therapies such as Total Marrow (+ Lymphoid) Irradiation (TMI / TMLI), and Total Lymphoid Irradiation (TLI) are established and prospectively evaluated in several centers. With each center developing their own methods, a new practice heterogeneity is arising, as was the case for decades with conventional TBI. To provide a ground base - and therefore more options for more homogeneous and comparable practice - for centers who are implementing conformal isocentric techniques, a group of early adopters of isocentric conformal TBI and TM(L)I came together to convey issues they encountered during clinical implementation, and form consensus recommendations for delineation and planning targets, based on available literature evaluation and shared experience. These recommendations follow previously published recommendations regarding technical setup of conformal isocentric TBI / TM(L)I techniques.

Bidirectional Communication Between the Innate and Adaptive Immune Systems

Effective bidirectional communication between the innate and adaptive immune systems is crucial for tissue homeostasis and protective immunity against infections. The innate immune system is responsible for the early sensing of and initial response to threats, including microbial ligands, toxins, and tissue damage. Pathogen-related information, detected primarily by the innate immune system via dendritic cells, is relayed to adaptive immune cells, leading to the priming and differentiation of naive T cells into effector and memory lineages. Memory T cells that persist long after pathogen clearance are integral for durable protective immunity. In addition to rapidly responding to reinfections, memory T cells also directly instruct the interacting myeloid cells to induce innate inflammation, which resembles microbial inflammation. As such, memory T cells act as newly emerging activators of the innate immune system and function independently of direct microbial recognition. While T cell-mediated activation of the innate immune system likely evolved as a protective mechanism to combat reinfections by virulent pathogens, the detrimental outcomes of this mechanism manifest in the forms of autoimmunity and other T cell-driven pathologies. Here, we review the complexities and layers of regulation at the interface between the innate and adaptive immune systems to highlight the implications of adaptive instruction of innate immunity in health and disease.

Dual in vivo T cell depleted haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide and anti-thymocyte globulin as a third salvage transplant for leukocyte adhesion deficiency with graft failure: a case report

Background

With recent advances in clinical practice, including the use of reduced-toxicity conditioning regimens and innovative approaches such as ex vivo TCRαβ/CD19 depletion of haploidentical donor stem cells or post-transplant cyclophosphamide (PTCY), hematopoietic stem cell transplantation (HSCT) has emerged as a curative treatment option for a growing population of patients with inborn errors of immunity (IEI). However, despite these promising developments, graft failure (GF) remains a significant concern associated with HSCT in these patients. Although a second HSCT is the only established salvage therapy for patients who experience GF, there are no uniform, standardized strategies for performing these second transplants. Furthermore, even less data is available regarding the outcomes and best practices for a third HSCT as a salvage measure when a second HSCT fails to achieve engraftment.

Case presentation

A 6-year-old boy with leukocyte adhesion deficiency type I (LAD-I) experienced GF after the first and second HSCT from a matched unrelated donor. As a salvage measure, the patient received a dual in vivo T-cell depleted haploidentical HSCT. The conditioning regimen for this third HSCT included anti-thymocyte globulin (ATG) and PTCY. Complete donor chimerism was assessed using the short tandem repeat (STR) PCR technique. By day +28 after the transplant, the expression of the leukocyte adhesion molecules CD18, CD11b, and CD11c on the patient's peripheral blood neutrophils had recovered to over 99%. It remained stable throughout the 18-month follow-up period.

Conclusion

T-cell replete haploidentical HSCT with ATG and PTCY may be a viable salvage option for LAD patients who have rejected prior HSCT.

Emapalumab therapy for hemophagocytic lymphohistiocytosis before reduced-intensity transplantation improves chimerism

ABSTRACT

Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder driven by interferon gamma (IFN-γ). Emapalumab, an anti-IFN-γ antibody, is approved for the treatment of patients with primary HLH. Hematopoietic stem cell transplantation (HSCT) is required for curing HLH. Reduced-intensity conditioning (RIC) HSCT is associated with improved survival but higher incidences of mixed chimerism and secondary graft failure. To understand the potential impact of emapalumab on post-HSCT outcomes, we conducted a retrospective study of pediatric patients with HLH receiving a first RIC-HSCT at our institution between 2014 and 2022 after treatment for HLH, with or without this agent. Mixed chimerism was defined as <95% donor chimerism and severe mixed chimerism as <25% donor chimerism. Intervention-free survival (IFS) included donor lymphocyte infusion, infusion of donor CD34-selected cells, second HSCT, or death within 5 years after HSCT. Fifty patients met the inclusion criteria; 22 received emapalumab within 21 days before the conditioning regimen, and 28 did not. The use of emapalumab was associated with a markedly lower incidence of mixed chimerism (48% vs 77%; P = .03) and severe mixed chimerism (5% vs 38%; P < .01). IFS was significantly higher in patients receiving emapalumab (73% vs 43%; P = .03). Improved IFS was even more striking in infants aged <12 months, a group at the highest risk for mixed chimerism (75% vs 20%; P < .01). Although overall survival was higher with emapalumab, this difference was not significant (82% vs 71%; P = .39). We show that the use of emapalumab for HLH before HSCT mitigates the risk of mixed chimerism and graft failure after RIC-HSCT.

Hematopoietic cell transplantation for inborn errors of immunity: an update on approaches, outcomes and innovations

PURPOSE OF REVIEW

Allogeneic hematopoietic cell transplantation (HCT) is a curative option for many for inborn errors of immunity (IEI). This review highlights recent progress in the field of HCT for IEI.

RECENT FINDINGS

Alternative donor transplantation continues to expand donor options for patients with IEI. Reduced intensity and reduced toxicity conditioning approaches are being investigated and optimized. Immunomodulatory bridging therapies are yielding impressive progress in outcomes for primary immune regulatory disorders (PIRD) but require further study in prospective trials. Single-institution, multicenter and consortium studies have improved our understanding of factors that affect overall outcomes in IEI and outcomes in Wiskott-Aldrich syndrome (WAS), chronic granulomatous disease (CGD) and PIRD in particular. Data show that second HCT offers a viable chance of cure to some IEI patients. Late effects in IEI HCT survivors are being better characterized. Preclinical studies of chemo(radiation)-free HCT strategies hold promise for decreasing HCT toxicity.

SUMMARY

Improvements in our understanding of HCT donor choice, conditioning regimen, immunomodulatory bridging therapies, diagnostic and post-HCT surveillance testing and late effects continue to yield advancements in the field of HCT for IEI.

Pediatric adapted risk index to predict 2-year transplant-related mortality post-HSCT in children

ABSTRACT

Several attempts have been made to optimize pretransplant risk assessment to improve hematopoietic stem cell transplantation (HSCT) decision-making and to predict post-HSCT outcomes. However, the relevance of pretransplant risk assessment to the pediatric population remains unclear. We report the results of revalidation of the hematopoietic cell transplantation comorbidity index (HCT-CI) in 874 children who received 944 HSCTs for malignant or nonmalignant diseases at a single center. After finding the HCT-CI invalid in our patient population, we proposed a modified pediatric adapted scoring system that captures risk factors (RFs) and comorbidities (CoMs) relevant to pediatrics. Each RF/CoM was assigned an integer weight based on its hazard ratio (HR) for transplant-related mortality (TRM): 0 (HR < 1.2), 1 (1.2 ≥ HR < 1.75), 2 (1.75 ≥ HR < 2.5), and 3 (HR ≥ 2.5). Using these weights, the pediatric adapted risk index (PARI) for HSCT was devised, and patients were divided into 4 risk groups (group 1: without RF/CoM; group 2: score 1-2; group 3: score 3-4; and group 4: score ≥5). There was a linear increase in 2-year TRM from group 1 to 4 (TRM, 6.2% in group 1, 50.9% in group 4). PARI was successfully validated on an internal and external cohort of pediatric patients. Comparing models using c-statistics, PARI was found to have better performance than HCT-CI in predicting 2-year TRM in children, with Akaike and Schwarz Bayesian information criteria values of 1069.245 and 1073.269, respectively, using PARI, vs 1223.158 and 1227.051, respectively, using HCT-CI. We believe that PARI will be a valuable tool enabling better counseling and decision-making for pediatric patients with HSCT.

Outcome of Second Allogeneic HSCT for Patients with Inborn Errors of Immunity: Retrospective Study of 20 Years' Experience

A significant complication of HSCT is graft failure, although few studies focus on this problem in patients with inborn errors of immunity (IE). We explored outcome of second HSCT for IEI by a retrospective, single-centre study between 2002 and 2022. Four hundred ninety-three patients underwent allogeneic HSCT for severe combined immunodeficiency (SCID; n = 113, 22.9%) or non-SCID IEI (n = 380, 77.1%). Thirty patients (6.0%) required second HSCT. Unconditioned infusion or no serotherapy at first HSCT was more common in patients who required second transplant. Median interval between first and second HSCT was 0.97 years (range: 0.19-8.60 years); a different donor was selected for second HSCT in 24/30 (80.0%) patients. Conditioning regimens for second HSCT were predominately treosulfan-based (with thiotepa: n = 18, 60.0%; without, n = 6, 20.0%). Patients received grafts from peripheral blood stem cell (n = 25, 83.3%) or bone marrow (n = 5, 16.7%) with median stem cell dose 9.5 × 106 CD34 + cells/kilogram (range: 1.4-32.3). Median follow-up was 1.92 years (0.22-16.0). Overall survival was 80.8% and event-free survival was 64.7%. Four patients died, two of early-transplant related complications, and two of late sepsis post-second HSCT. Three patients required third HSCT; all are alive with 100% donor chimerism. Cumulative incidence of acute graft-versus-host disease was 28.4%, (all grade I-II). Viral reactivation was seen in 13/30 (43.3%) patients, including HHV6 (n = 6), CMV (n = 4), and adenovirus (n = 2). At latest follow-up, 25/26 surviving patients have donor chimerism ≥ 90% and 16/25 (64.0%) have discontinued immunoglobulin replacement. Second HSCT offers IEI patients with graft failure curative treatment with good overall survival and immunological recovery.

Allogeneic Hematopoietic Stem Cell Transplantation Activity in Inborn Errors of Immunity in Russian Federation

PURPOSE

Allogeneic hematopoietic stem cell transplantation (HSCT) is an established therapy for many inborn errors of immunity (IEI). The indications for HSCT have expanded over the last decade. The study aimed to collect and analyze the data on HSCT activity in IEI in Russia.

METHODS

The data were collected from the Russian Primary Immunodeficiency Registry and complemented with information from five Russian pediatric transplant centers. Patients diagnosed with IEI by the age of 18 years and who received allogeneic HSCT by the end of 2020 were included.

RESULTS

From 1997 to 2020, 454 patients with IEI received 514 allogeneic HSCT. The median number of HSCTs per year has risen from 3 in 1997-2009 to 60 in 2015-2020. The most common groups of IEI were immunodeficiency affecting cellular and humoral immunity (26%), combined immunodeficiency with associated/syndromic features (28%), phagocyte defects (21%), and diseases of immune dysregulation (17%). The distribution of IEI diagnosis has changed: before 2012, the majority (65%) had severe combined immunodeficiency (SCID) and hemophagocytic lymphohistiocytosis (HLH), and after 2012, only 24% had SCID and HLH. Of 513 HSCTs, 48.5% were performed from matched-unrelated, 36.5% from mismatched-related (MMRD), and 15% from matched-related donors. In 349 transplants T-cell depletion was used: 325 TCRαβ/CD19+ depletion, 39 post-transplant cyclophosphamide, and 27 other. The proportion of MMRD has risen over the recent years.

CONCLUSION

The practice of HSCT in IEI has been changing in Russia. Expanding indications to HSCT and SCID newborn screening implementation may necessitate additional transplant beds for IEI in Russia.