Emerging role of CD20 blockade in allogeneic hematopoietic cell transplantation

Applying Rituximab During the Conditioning Regimen Prevents Epstein-Barr Virus Infection Following Allogeneic Hematopoietic Stem Cell Transplant in a Children's Cohort: A Retrospective Case-Control Study

INTRODUCTION

Since hematopoietic stem cell transplant (HSCT) is an important therapy for malignant and non-malignant pediatric diseases, improving transplant-related mortality remains a challenge. Currently, rituximab, a monoclonal antibody of anti-CD20, is widely used for several post-HSCT complications. However, few studies have focused on the application of rituximab before HSCT.

METHODS

We conducted a retrospective case-control study from January 2019 to July 2021 to determine this effect in a single center. Forty-eight patients were included in the rituximab group, with a one-to-one ratio matched to the control group.

RESULTS

Both the occurrence rate and cumulative incidence rate of Epstein-Barr virus (EBV) infection were significantly lower in the rituximab group than in the without-rituximab group (10.4% vs. 33.3%, p = 0.014 and 12.2% vs. 39.3% p = 0.0026, respectively). Furthermore, without the application of rituximab was identified as a risk factor for post-HSCT EBV infection via both univariate [hazard ratio (HR) = 4.17, 95%CI (1.52-11.43), p = 0.005] and multivariate analyses [HR = 4.65, 95%CI (1.66-13.0), p = 0.003]. Although the overall survival (OS) probability of the rituximab group was comparable to the without-rituximab group, a markedly improved OS of the rituximab group was found in the malignant disease subgroup (78.9% vs. 42.1%, p = 0.032). The outcomes of graft-versus-host disease, neutrophil and platelet engraftment, other viral infections, and the reconstitution of lymphocytes showed no significant differences between the two groups.

CONCLUSIONS

The administration of rituximab before HSCT may prevent EBV infection following HSCT.

Immunological considerations and challenges for regenerative cellular therapies

The central goal of regenerative medicine is to replace damaged or diseased tissue with cells that integrate and function optimally. The capacity of pluripotent stem cells to produce unlimited numbers of differentiated cells is of considerable therapeutic interest, with several clinical trials underway. However, the host immune response represents an important barrier to clinical translation. Here we describe the role of the host innate and adaptive immune responses as triggers of allogeneic graft rejection. We discuss how the immune response is determined by the cellular therapy. Additionally, we describe the range of available in vitro and in vivo experimental approaches to examine the immunogenicity of cellular therapies, and finally we review potential strategies to ameliorate immune rejection. In conclusion, we advocate establishment of platforms that bring together the multidisciplinary expertise and infrastructure necessary to comprehensively investigate the immunogenicity of cellular therapies to ensure their clinical safety and efficacy.

Control of graft-versus-host disease with rabbit anti-thymocyte globulin, rituximab, and bortezomib in TCRαβ/CD19-depleted graft transplantation for leukemia in children: a single-center retrospective analysis of two GVHD-prophylaxis regimens

Both acute GVHD and chronic GVHD remain the leading cause of morbidity and death after allogeneic HSCT. We conducted a retrospective analysis comparing two GVHD-prophylaxis regimens: 35 patients received "Regimen 1" (horse ATG, tacrolimus, and methotrexate) and 46 "Regimen 2" (rabbit ATG, rituximab, and peritransplant bortezomib). All 81 patients with a median age of 9 (0.6-23) years with ALL (n = 31) or AML (n = 50) in complete remission received TCRαβ/CD19-depleted transplants between May 2012 and October 2016, from 40 HLA-matched unrelated and 41 haploidentical donors. After a median follow-up of 3.9 years, the CI of acute GVHD II-IV was 15% (95% CI: 7-30) in the "Regimen 2" group and 34% (95% CI: -54) in the "Regimen 1" group, P = .05. "Regimen 2" was also more effective in the prevention of chronic GVHD; the CI at 1 year after HSCT was 7% (95% CI: 2-19) vs 31% (95% CI: 19-51), P = .005. The CI of relapse at 3 years adjusted for the GVHD-prophylaxis regimen groups 31% (95% CI: 19-51) for the "Regimen 1" vs 21% (95% CI: 11-37) for the "Regimen 2", P = .3. The retrospective observation suggests that the use of the rATG, rituximab, and bortezomib was associated with significantly lower rate of GVHD without the loss of anti-leukemic activity.

Virotherapy as Potential Adjunct Therapy for Graft-Vs-Host Disease

PURPOSE OF REVIEW

This review discusses the pathophysiology, risk factors, and the advances in the prevention or treatment of graft-vs-host disease (GvHD) by exploiting adjunct virotherapy. In addition, nonviral adjunct therapeutic options for the prevention of GvHD in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) are discussed. The role of oncolytic viruses to treat different HSCT-eligible hematological cancers is also considered and correlated with the issue of GvHD in the context of allo-HSCT.

RECENT FINDINGS

Emerging therapies focused on the prevention or treatment of GvHD include the use of regulatory T cells (Tregs), mesenchymal stem cells (MSCs), microbiome manipulation, B cell inhibitors, among others. Our lab and others have reported that an oncolytic DNA virus from the Poxviridae family, called myxoma virus (MYXV), not only exhibits oncolytic activity against various hematologic malignancies like multiple myeloma (MM) or acute myeloid leukemia (AML) but also, in addition, ex vivo MYXV treatment of human allogeneic-bone marrow transplants (allo-BMT), or allo-peripheral blood mononuclear cell (allo-PBMC) transplants can abrogate GvHD in xenografted mice without impairing graft-vs-tumor (GvT) effects against residual cancer. To date, this is the first and the only oncolytic virus with a dual potential of mediating oncolysis against a residual cancer target and also inhibiting or preventing GvHD following allo-HSCT.

SUMMARY

This review discusses how oncolytic virotherapy can be applied as a potential adjunct therapy for the potential treatment of GvHD. In addition, we highlight major emerging nonviral therapies currently studied for the treatment or prevention of GvHD. We also review the emerging oncolytic virotherapies against different hematological cancers currently eligible for allo-HSCT and highlight the potential role of the oncolytic virus MYXV to decrease GvHD while maintaining or enhancing the positive benefits of GvT.

Risk of graft-versus-host disease with rituximab-containing conditioning regimens in allogeneic hematopoietic stem cell transplant

Graft-versus-host disease represents a major cause of morbidity and mortality in allogeneic hematopoietic stem cell transplant patients. There is growing evidence that B lymphocytes may play a role in the pathogenesis of acute graft-versus-host disease. The purpose of this retrospective cohort study was to evaluate the efficacy of rituximab-containing conditioning regimens in decreasing graft-versus-host disease in allogeneic hematopoietic stem cell transplant patients who received standardized tacrolimus-based graft-versus-host disease prophylaxis regimens. Patients were divided into two cohorts, based on the presence (RTX, n = 54) or absence (No-RTX, n = 105) of rituximab in the conditioning regimen and were matched 1:2 for major graft-versus-host disease risk factors. The incidence of grade II-IV acute graft-versus-host disease was not different between the two groups (37% vs. 26%, p = 0.147). When restricting the analysis to recipients of peripheral blood hematopoietic stem cell transplants, the RTX group had a higher incidence of grade II-IV acute graft-versus-host disease, relapse, or death prior to day 100 (55% vs. 36%, p = 0.037). The median time to the onset of acute graft-versus-host disease was no different between the RTX and No-RTX groups (67 vs. 74 days, respectively, p = 0.141). Inhibition of antigen presentation by B cells with rituximab-based conditioning regimens does not appear to reduce the incidence of acute graft-versus-host disease in allogeneic hematopoietic stem cell transplant recipients.

Chronic graft-versus-host disease presenting as eosinophilic fasciitis: therapeutic challenges and an additional case

Chronic graft-versus-host disease (cGVHD) is one of the main late complications of allogeneic hematopoietic stem cell transplant and a major contributor to the mortality and morbidity in surviving recipients. Skin is the most common involved organ in cGVHD and may mimic a wide spectrum of dermatological conditions in its clinical and histopathologic manifestations. Some of the commonly simulated diseases are scleroderma, morphea, and lichen sclerosus. Chronic GVHD simulating eosinophilic fasciitis (EF) is relatively rare, frequently presenting with skin induration, a typical "peau d'orange" appearance, peripheral blood eosinophilia, myalgia, arthralgia, and arthritis leading to joint contractures in severe cases.Diagnosis is based on clinical manifestations and histopathology. Treatment is challenging because most cases are refractory to first-line therapy of glucocorticoids and calcineurin inhibitors (CNIs), and there is no standard second-line therapy.We report a comprehensive review of literature on all reported cases of CGVHD presenting as EF. We also describe an additional interesting case of cGVHD presenting as EF that was resistant to traditional therapy of high-dose glucocorticoids and cyclosporin A, but showed complete resolution of skin manifestations after addition of imatinib.Chronic GVHD presenting as EF is a rare variant of sclerodermatous cGVHD. Diagnosis is difficult, and treatment of cGVHD mimicking EF remains a therapeutic challenge because of obscure pathogenesis and poor response to traditional immunosuppressive medications. Emerging insights into the pathogenesis of cGVHD have resulted in the development of novel targeted therapies, which may improve outcomes and should be attempted in this subset of the disease. Larger studies are warranted to substantiate these preliminary findings.

Phase II study of CD4+-guided pentostatin lymphodepletion and pharmacokinetically targeted busulfan as conditioning for hematopoietic cell allografting

One limitation of reduced-intensity preparative regimens is potential for graft failure. We have developed a regimen that targets CD4(+) lymphodepletion to ensure early and durable engraftment. The primary endpoint was achievement of ≥50% CD3(+) donor chimerism by day +28. Forty-two patients (median age, 53 years; range, 29 to 73 years) received pentostatin 4 mg/m(2) i.v. on days -28, -21, and -14 when the CD4(+) cell count was >100 cells/μL and on days -4 and -3 regardless of CD4(+) level. Rituximab 375 mg/m(2) was administered to patients with CD20(+) malignancies on days -21, -14, -7, +1, and +8. Busulfan 200 mg/m(2) i.v. was administered on days -4 and -2 at a dose to target a cumulative AUC dose of 16,000 (±10%) μmol·min/L. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus plus methotrexate in 86% of patients. Donors were matched-related (47%), matched unrelated (43%), or mismatched unrelated (10%). Chronic lymphocytic leukemia (45%) and follicular non-Hodgkin lymphoma (14%) were the most common diagnoses. Disease status at initiation of the preparative regimen was complete remission in 22%, partial response in 55%, and stable/progression in 24%. The median percent CD4(+) cell count decrease from baseline (day -28) was 52% to day -21, 66% to day -14, 62% to day -7, and 91% to day 0. At day +28, all 42 patients (100%) had ≥50% CD3(+) donor chimerism. No patient experienced graft failure. Overall response rate was 82% (complete remisson, 67%). The day +100 cumulative incidence of grade II-IV acute GVHD was 59% (grade III-IV acute GVHD, 19%), and the 2 year cumulative incidence of chronic GVHD was 69% (moderate/severe, 58%). Nonrelapse mortality was 2% at day +100 and 17% at 2 years. Two-year PFS was 55%, and OS was 68%. This regimen ensures durable engraftment, is effective against persistent disease, and results in relatively low mortality from causes other than relapse.

Monoclonal antibodies in conditioning regimens for hematopoietic cell transplantation

Monoclonal antibodies are increasingly being incorporated in conditioning regimens for autologous or allogeneic hematopoietic cell transplantation (HCT). The benefit of adding rituximab to autologous HCT regimens is purportedly related to in vivo purging of clonal B cells. Randomized trials comparing the addition (or not) of rituximab to high-dose therapy regimens are lacking. No benefit of standard-dose radioimmunotherapy-based regimens for autografting in aggressive lymphomas was seen in a randomized controlled study. The incorporation of rituximab into allogeneic HCT regimens aims to improve responses while reducing nonrelapse mortality resulting from acute graft-versus-host disease. The optimal dose and administration schedule of rituximab in this setting are unknown, and potentially serious complications from increased infections owing to prolonged (and profound) cytopenias or persistent hypogammaglobulinemia are of concern. Radioimmunotherapy-based conditioning for allografting holds promise as a modality to optimize tumor control and synergize adoptive immunotherapy effects, but it remains experimental at this time. The addition of alemtuzumab to allogeneic HCT regimens is associated with prolonged lymphopenia and impaired immune reconstitution, high relapse rates, and serious infections. The optimal dose and schedule of alemtuzumab to avoid prolonged immune paresis remain elusive. It is anticipated that additional monoclonal antibodies will soon become available that can be incorporated into HCT regimens after safety and clinical efficacy are demonstrated.

H-Y antigen-binding B cells develop in male recipients of female hematopoietic cells and associate with chronic graft vs. host disease

B cells are known to play an important role in pathogenesis of human chronic graft vs. host disease (cGVHD). Our group has previously shown that IgG allo-antibodies recognize Y chromosome-encoded proteins (H-Y) and a dominant H-Y epitope, DEAD box protein (DBY-2) detectable 6-12 mo after transplant in male patients who receive grafts from female donors (F→M) hematopoietic cell transplantation (HCT). Here we present FACS studies of peripheral blood mononuclear cells collected 6 mo after transplant showing that 16 of 28 (57%) F→M HCT patients have circulating donor B cells that express B-cell receptor (mainly IgM and Igλ) specific for DBY-2. The detection of these DBY-2 B cells 6 mo after HCT are associated with cGVHD development (P = 0.004). Specifically, 15 of 16 F→M with DBY-2 B cells developed cGVHD. In contrast, cGVHD developed in only 5 of the 12 who did not have DBY-2 B cells detected. This demonstrates circulating human B cells binding an alloantigen (DBY-2) and that these DBY-2-specific B cells appear before development of cGVHD in roughly half of the F→M patients. Our study suggests that detection of anti-DBY-2 B cells may predict cGVHD and that this prediction may have clinical utility. Validation of this hypothesis will require larger prospective studies.

Treatment of chronic graft-versus-host disease in 2011

PURPOSE OF REVIEW

This article summarizes recent reports on the risks, pathogenesis and treatment of chronic graft-versus-host disease (GVHD).

RECENT FINDINGS

Chronic GVHD remains an elusive disorder to characterize and to treat. Recent evidence on tolerance induction by regulatory T-cells and on B-cell involvement shed some insights into the pathogenesis of chronic GVHD. In a recent large comparative study, the overall risk profiles for acute and for chronic GVHD were similar, but risk factors were not changed after adjustment for prior acute GVHD, supporting the concept that chronic GVHD is not an end stage of acute GVHD. Glucocorticoids remain the standard initial treatment of chronic GVHD, but the outcomes are not satisfactory, particularly for patients with high-risk features. Many treatments for chronic GVHD including extracorporeal photopheresis, rituximab, sirolimus, mycofenolate mofetil, imatinib, pentostatin and infusion of mesenchymal stem cells have been reported in several retrospective and relatively small phase I/II studies with a wide range of overall responses.

SUMMARY

No current therapies used for chronic GVHD have been approved by the US Food and Drug Administration. Large well designed prospective studies are warranted to establish better treatments. Targeted therapies based on the pathogenesis of chronic GVHD may lead to better outcomes.

Effectiveness of subcutaneous low-dose alemtuzumab and rituximab combination therapy for steroid-resistant chronic graft-versus-host disease

BACKGROUND

Chronic graft-versus-host disease is a common late complication of allogeneic hematopoietic stem cell transplantation. Corticosteroids are the standard initial treatment. Second-line treatment has not been well defined. We evaluated the effectiveness and safety of low doses of alemtuzumab plus low doses of rituximab in the treatment of steroid-refractory chronic graft-versus-host disease.

DESIGN AND METHODS

Ten men and 5 women were prospectively included in the study. All patients received one cycle of subcutaneous alemtuzumab 10 mg/day/3 days and intravenous rituximab 100 mg on Days +4, +11, +18 and +25. The therapeutic response was measured on Days +30, +90 and +365 of the protocol.

RESULTS

Median age was 41 years. The main site involved was the oral mucosa (86.7%) followed by the eyes (66.7%), liver (60%), skin (53%), lungs (13.3%) and intestinal tract (6.7%). The overall response was 100% at Day +30 evaluation: 10 patients (67%) had partial remission, 5 (33%) had complete remission. At Day +90 evaluation, 7 (50%) patients had partial remission, 4 (28%) had complete remission; 3 (21%) had relapsed chronic graft-versus-host disease and one patient did not reach the evaluation time point. So far, 5 patients have reached the Day +365 follow-up evaluation; 2 (40%) had partial remission, 2 had complete remission and one experienced chronic graft-versus-host disease progression. Adverse effects were mainly infections in 67% of patients; these were all quickly solved, except for one patient who died from pneumonia.

CONCLUSIONS

This combination therapy appears to be an efficacious and safe treatment for steroid-refractory chronic graft-versus-host disease. Longer follow up to determine the durability of response and survival is required (ClinicalTrials.gov: NCT01042509).

Strategies to prevent EBV reactivation and posttransplant lymphoproliferative disorders (PTLD) after allogeneic stem cell transplantation in high-risk patients

Epstein-Barr virus (EBV)-associated postallogeneic stem cell transplantation (SCT) lymphoproliferative disorder (PTLD) is often life threatening. The risk of EBV reactivation is highest in older patients, T cell-depleted SCT (in vivo or vitro), and in unrelated or mismatched SCT. Cumulative numbers of patients with EBV reactivation and PTLD are rising as more patients at high risk for EBV reactivation and PTLD are receiving allo-SCT. Novel but easily applicable strategies are needed to prevent EBV reactivation and PTLD to serve the needs of the increasingly enlarging population of high-risk SCT recipients across the globe.

In vivo B-cell depletion with rituximab for alternative donor hemopoietic SCT

We retrospectively analyzed 55 patients given a fixed dose of rituximab (200 mg) on day+5 after an alternative donor transplant, to prevent EBV DNA-emia; 68 alternative transplants who did not receive prophylactic rituximab served as controls. The two groups were comparable for donor type, and all patients received anti-thymocyte globulin in the conditioning regimen. Rituximab patients had a significantly lower rate of EBV DNA-emia 56 vs 85% (P=0.0004), a lower number of maximum median EBV copies (91 vs 1321/10(5) cells, P=0.003) and a significantly lower risk of exceeding 1000 EBV copies per 10(5)cells (14 vs 49%, P=0.0001). Leukocyte and lymphocyte counts were lower on day +50 and+100 in rituximab patients, whereas Ig levels were comparable. The cumulative incidence of grade II-IV acute GvHD was significantly reduced in rituximab patients (20 vs 38%, P=0.02). Chronic GvHD was comparable. There was a trend for a survival advantage for patients receiving rituximab (46 vs 40%, P=0.1), mainly because of lower transplant mortality (25 vs 37%, P=0.1). Despite the drawback of a retrospective study, these data suggest that a fixed dose of rituximab on day +5 reduces the risk of a high EBV load, and also reduces acute GvHD.

Concise review: hitting the right spot with mesenchymal stromal cells

Mesenchymal stromal cells or mesenchymal stem cells (MSCs) have captured considerable scientific and public interest because of their potential to limit physical and immune injury, to produce bioactive molecules and to regenerate tissues. MSCs are phenotypically heterogeneous and distinct subpopulations within MSC cultures are presumed to contribute to tissue repair and the modulation of allogeneic immune responses. As the first example of efficacy, clinical trials for prevention and treatment of graft-versus-host disease after hematopoietic cell transplantation show that MSCs can effectively treat human disease. The view of the mechanisms whereby MSCs function as immunomodulatory and reparative cells has evolved simultaneously. Initially, donor MSCs were thought to replace damaged cells in injured tissues of the recipient. More recently, however, it has become increasingly clear that even transient MSC engraftment may exert favorable effects through the secretion of cytokines and other paracrine factors, which engage and recruit recipient cells in productive tissue repair. Thus, an important reason to investigate MSCs in mechanistic preclinical models and in clinical trials with well-defined end points and controls is to better understand the therapeutic potential of these multifunctional cells. Here, we review the controversies and recent insights into MSC biology, the regulation of alloresponses by MSCs in preclinical models, as well as clinical experience with MSC infusions (Table 1) and the challenges of manufacturing a ready supply of highly defined transplantable MSCs.