Novel approaches for preventing acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Practical considerations of promising zone design for interim sample size Re-estimation: An application to GRAPHITE for graft vs host disease

BACKGROUND

Sample size calculation and power estimate are an integral part of clinical trials. With accelerated development to address the unmet medical needs, the fast-paced development may lead to uncertainties in initial planning and assumptions of clinical trials. Promising zone design presents sponsors an opportunity to re-estimate the sample size based on the interim data to mitigate risks, reduce uncertainties, and increase probability of trial success.

METHODS

This paper aims to use the GRAPHITE trial (NCT03657160) as a real data application to showcase the practical considerations in implementation of promising zone design for interim sample size re-estimation (SSR), in light of sample size adaptation rules, maximum sample size allowed, multiplicity adjustment, and sponsor access to interim results. GRAPHITE is a phase 3 trial with vedolizumab for prophylaxis of acute graft vs host disease (aGvHD) after allogeneic hematopoietic stem cell transplant (allo-HSCT). The primary efficacy endpoint is lower intestinal aGVHD-free survival by Day +180 after allo-HSCT. A simulation study was conducted to demonstrate the evaluation of operating characteristics by various true underlying treatment effects at the design stage.

CONCLUSION

The application of promising zone design for interim SSR is novel and has successfully helped the sponsor achieve the balance between minimizing the risks and maintaining scientific integrity. This work aims to highlight the necessity of empirical guidance to gain better insights for clinical researchers in practice and is expected to facilitate the understanding and implementation of promising zone design for interim SSR in phase 3 trials.

Pathophysiology and preclinical relevance of experimental graft-versus-host disease in humanized mice

Graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantations (allo-HCT) used for the treatment of hematological malignancies and other blood-related disorders. Until recently, the discovery of actionable molecular targets to treat GVHD and their preclinical testing was almost exclusively based on modeling allo-HCT in mice by transplanting bone marrow and splenocytes from donor mice into MHC-mismatched recipient animals. However, due to fundamental differences between human and mouse immunology, the translation of these molecular targets into the clinic can be limited. Therefore, humanized mouse models of GVHD were developed to circumvent this limitation. In these models, following the transplantation of human peripheral blood mononuclear cells (PBMCs) into immunodeficient mice, T cells recognize and attack mouse organs, inducing GVHD. Thereby, humanized mice provide a platform for the evaluation of the effects of candidate therapies on GVHD mediated by human immune cells in vivo. Understanding the pathophysiology of this xenogeneic GVHD is therefore crucial for the design and interpretation of experiments performed with this model. In this article, we comprehensively review the cellular and molecular mechanisms governing GVHD in the most commonly used model of xenogeneic GVHD: PBMC-engrafted NOD/LtSz-PrkdcscidIL2rγtm1Wjl (NSG) mice. By re-analyzing public sequencing data, we also show that the clonal expansion and the transcriptional program of T cells in humanized mice closely reflect those in humans. Finally, we highlight the strengths and limitations of this model, as well as arguments in favor of its biological relevance for studying T-cell reactions against healthy tissues or cancer cells.

Multi-parametric MRI in the diagnosis and scoring of gastrointestinal acute graft-versus-host disease

OBJECTIVES

Acute gastrointestinal graft-versus-host disease (GI-aGVHD) is a severe complication of allogeneic hematopoietic stem cell transplantation (HSCT). Diagnosis relies on clinical, endoscopic, and pathological investigations. Our purpose is to assess the value of magnetic resonance imaging (MRI) in the diagnosis, staging, and prediction of GI-aGVHD-related mortality.

METHODS

Twenty-one hematological patients who underwent MRI for clinical suspicion of acute GI-GVHD were retrospectively selected. Three independent radiologists, blinded to the clinical findings, reanalyzed MRI images. The GI tract was evaluated from stomach to rectum by analyzing fifteen MRI signs suggestive of intestinal and peritoneal inflammation. All selected patients underwent colonoscopy with biopsies. Disease severity was determined on the basis of clinical criteria, identifying 4 stages of increasing severity. Disease-related mortality was also assessed.

RESULTS

The diagnosis of GI-aGVHD was histologically confirmed with biopsy in 13 patients (61.9%). Using 6 major signs (diagnostic score), MRI showed 84.6% sensitivity and 100% specificity in identifying GI-aGVHD (AUC = 0.962; 95% confidence interval 0.891-1). The proximal, middle, and distal ileum were the segments most frequently affected by the disease (84.6%). Using all 15 signs of inflammation (severity score), MRI showed 100% sensitivity and 90% specificity for 1-month related mortality. No correlation with the clinical score was found.

CONCLUSION

MRI has proved to be an effective tool for diagnosing and scoring GI-aGVHD, with a high prognostic value. If larger studies will confirm these results, MRI could partly replace endoscopy, thus becoming the primary diagnostic tool for GI-aGVHD, being more complete, less invasive, and more easily repeatable.

KEY POINTS

• We have developed a new promising MRI diagnostic score for GI-aGVHD with a sensitivity of 84.6% and specificity of 100%; results are to be confirmed by larger multicentric studies. • This MRI diagnostic score is based on the six MRI signs most frequently associated with GI-aGVHD: small-bowel inflammatory involvement, bowel wall stratification on T2-w images, wall stratification on post-contrast T1-w images, ascites, and edema of retroperitoneal fat and declivous soft tissues. • A broader MRI severity score based on 15 MRI signs showed no correlation with clinical staging but high prognostic value (100% sensitivity, 90% specificity for 1-month related mortality); these results also need to be confirmed by larger studies.

Highlighting the interaction between immunomodulatory properties of mesenchymal stem cells and signaling pathways contribute to Graft Versus Host Disease management

Background Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) has been increasingly used as a therapeutic approach for hematological malignancies. Several potential strategies have been developed for treating or preventing allo-HSCT complications, specifically graft-versus-host disease (GVHD). GVHD could significantly affect the morbidity and mortality of patients after allo-HSCT. Curative treatment and prophylaxis regimens for GVHD could reduce GVHD incidence and improve survival rate. Among these therapeutic strategies, mesenchymal stem cell (MSCs) mediated immunomodulation has been explored widely in clinical trials. MSCs immunomodulation ability in GVHD correlates with the interactions of MSCs with innate and adaptive immune cells. However, signaling pathways responsible for MSCs' impact on GVHD regulation, like JAK/STAT, NOTCH, MAPK/ERK, and NFκβ signaling pathways, have not been clearly described yet. This review aims to illuminate the effect of MSCs-mediated immunomodulation in GVHD management after allo-HSCT representing the role of MSCs therapy on signaling pathways in GVHD. Conclusion MSCs could potentially modulate immune responses, prevent GVHD, and improve survival after allo-HSCT. Previous studies have investigated different signaling pathways' contributions to MSCs immunoregulatory ability. Accordingly, targeting signaling pathways components involved in MSCs related GVHD regulation is proven to be beneficial.

Preventive and Therapeutic Effects of a Novel JAK Inhibitor SHR0302 in Acute Graft-Versus-Host Disease

Acute graft-versus-host disease (aGVHD) is one of the most common complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Janus kinase (JAK) inhibitors are considered as reliable and promising agents for patients with aGVHD. The prophylactic and therapeutic effects of SHR0302, a novel JAK inhibitor, were evaluated in aGVHD mouse models. The overall survival (OS), progression-free survival (PFS), bodyweight of mice, GVHD scores were observed and recorded. The bone marrow and spleen samples of diseased model mice or peripheral blood of patients were analyzed. SHR0302 could prevent and reverse aGVHD in mouse models with preserving graft-versus-tumor effect. Functionally, SHR0302 improved the OS and PFS, restored bodyweight, reduced GVHD scores, and reduced immune cells infiltrated in target tissues. SHR0302 treatment also enhanced the hematopoietic reconstruction compared to the control group. Mechanistically, our results suggested that SHR0302 could inhibit the activation of T cells and modulate the differentiation of helper T (Th) cells by reducing Th1 and increasing regulatory T (Treg) cells. In addition, SHR0302 decreased the expression of chemokine receptor CXCR3 on donor T cells and the secretion of cytokines or chemokines including interleukin (IL)-6, interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), CXCL10, etc. thereby destroying the IFN-γ/CXCR3/CXCL10 axis which promotes the progression of GVHD. Besides, SHR0302 decreased the phosphorylation of JAK and its downstream STATs, AKT and ERK1/2, which ultimately regulated the activation, proliferation, and differentiation of lymphocytes. Experiments on primary cells from aGVHD patients also confirmed the results. In summary, our results indicated that JAK inhibitor SHR0302 might be used as a novel agent for patients with aGVHD.

Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT.

Broad-Spectrum Antibiotics and Risk of Graft-versus-Host Disease in Pediatric Patients Undergoing Transplantation for Acute Leukemia: Association of Carbapenem Use with the Risk of Acute Graft-versus-Host Disease

Variation in the gastrointestinal (GI) microbiota after hematopoietic cell transplantation (HCT) has been associated with acute graft-versus-host disease (aGVHD). Because antibiotics induce dysbiosis, we examined the association of broad-spectrum antibiotics with subsequent aGVHD risk in pediatric patients undergoing HCT for acute leukemia. We performed a retrospective analysis in a dataset merged from 2 sources: (1) the Center for International Blood and Marrow Transplant Research, an observational transplantation registry, and (2) the Pediatric Health Information Services, an administrative database from freestanding children's hospitals. We captured exposure to 3 classes of antibiotics used for empiric treatment of febrile neutropenia: (1) broad-spectrum cephalosporins, (2) antipseudomonal penicillins, and (3) carbapenems. The primary outcome was grade II-IV aGVHD; secondary outcomes were grade III-IV aGVHD and lower GI GVHD. The adjusted logistic regression model (full cohort) and time-to-event analysis (subcohort) included transplantation characteristics, GVHD risk factors, and adjunctive antibiotic exposures as covariates. The full cohort included 2550 patients at 36 centers; the subcohort included 1174 patients. In adjusted models, carbapenems were associated with an increased risk of grade II-IV aGVHD in the full cohort (adjusted odds ratio [aOR], 1.24; 95% confidence interval [CI], 1.02 to 1.51) and subcohort (sub hazard ratio [HR], 1.31; 95% CI, 0.99 to 1.72), as well as with an increased risk of grade III-IV aGVHD (subHR, 1.77; 95% CI, 1.25 to 2.52). Early carbapenem exposure (before day 0) especially impacted aGVHD risk. For antipseudomonal penicillins, the associations with aGVHD were in the direction of increased risk but were not statistically significant. There was no identified association between broad-spectrum cephalosporins and aGVHD. Carbapenems, more than other broad-spectrum antibiotics, should be used judiciously in pediatric HCT recipients to minimize aGVHD risk. Further research is needed to clarify the mechanism underlying this association.

How to Make an Immune System and a Foreign Host Quickly Cohabit in Peace? The Challenge of Acute Graft-Versus-Host Disease Prevention After Allogeneic Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (alloHCT) has been used as cellular immunotherapy against hematological cancers for more than six decades. Its therapeutic efficacy relies on the cytoreductive effects of the conditioning regimen but also on potent graft-versus-tumor (GVT) reactions mediated by donor-derived immune cells. However, beneficial GVT effects may be counterbalanced by acute GVHD (aGVHD), a systemic syndrome in which donor immune cells attack healthy tissues of the recipient, resulting in severe inflammatory lesions mainly of the skin, gut, and liver. Despite standard prophylaxis regimens, aGVHD still occurs in approximately 20–50% of alloHCT recipients and remains a leading cause of transplant-related mortality. Over the past two decades, advances in the understanding its pathophysiology have helped to redefine aGVHD reactions and clinical presentations as well as developing novel strategies to optimize its prevention. In this review, we provide a brief overview of current knowledge on aGVHD immunopathology and discuss current approaches and novel strategies being developed and evaluated in clinical trials for aGVHD prevention. Optimal prophylaxis of aGVHD would prevent the development of clinically significant aGVHD, while preserving sufficient immune responsiveness to maintain beneficial GVT effects and immune defenses against pathogens.

Oral Dysplastic Complications after HSCT: Single Case Series of Multidisciplinary Evaluation of 80 Patients

Oral squamous cell carcinoma (OSCC) is the most common secondary solid malignancy after hematopoietic stem-cell transplantation (HSCT). OSCC following HSCT is frequently preceded by chronic graft-versus-host disease (cGVHD). The aim of this study was to describe a cohort of post-HSCT patients and to evaluate the onset of oral epithelial dysplasia and/or OSCC over time. In this retrospective cohort study, we present a cohort of hematological patients that underwent HSCT. Demographic variables, clinical hematological data, data regarding acute graft-versus-host disease (aGVHD) and cGVHD, and oral clinical features were analyzed. We focused on clinicopathological features of a subgroup of 22 patients with oral cGVHD and OSCC after HSCT. Among 80 included patients, 46 patients (57.5%) developed aGVHD and 39 patients (48.7%) developed cGVHD. Oral mucosa was involved in 17 patients with aGVHD (36.9%) and in 22 patients (56.4%) with cGVHD. Out of a total of 22 oral biopsies, roughly 40% revealed mild to moderate dysplasia, and 32% were OSCC. In the absence of international agreement on the best timing of oral follow-up after HSCT, it is mandatory to establish a close multidisciplinary evaluation in order to prevent the onset of HSCT-related OSCC and to reduce post-transplant mortality due to secondary tumors.

Vedolizumab for prevention of graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGVHD) remains a significant complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Vedolizumab could help prevent aGVHD by inhibiting the migration of both naive and activated lymphocytes into gut-associated lymphoid tissues and the lamina propria. We carried out a phase 1b, open-label, dose-finding study in adults undergoing allo-HSCT to evaluate the tolerability, safety, and pharmacokinetics of vedolizumab, and its effectiveness in reducing aGVHD. IV vedolizumab was administered on day -1, +13, and +42 with respect to allo-HSCT, starting at 75 mg and with dose escalation guided by tolerability and pharmacokinetics. A total of 24 participants was enrolled, and no dose-limiting toxicities were observed in either the 75-mg cohort (n = 3) or the dose-escalated 300-mg cohort (n = 21). Treatment-emergent adverse events related to vedolizumab occurred in 8 participants. Overall, 4 deaths occurred during the 12 months following allo-HSCT. No participants in the 75-mg cohort developed modified Glucksberg grade II to IV aGVHD by 100 days after allo-HSCT. Four participants (19.0%) in the 300-mg cohort developed grade II to IV aGVHD by 100 days after allo-HSCT, including 3 participants who developed stage 1 aGVHD of the lower-intestinal tract. Vedolizumab IV 300 mg was well tolerated as aGVHD prevention, and the incidence of overall and lower-intestinal aGVHD was low. These findings support further evaluation of vedolizumab in this patient population. This trial was registered at www.clinicaltrials.gov as #NCT02728895.

CCR5 inhibitor as novel acute graft versus host disease prophylaxis in children and young adults undergoing allogeneic stem cell transplant: results of the phase II study

We report results of a phase II study of maraviroc to prevent acute graft versus host disease (GVHD) in children undergoing allogeneic hematopoietic stem cell transplant (HSCT). Oral maraviroc was added to standard GVHD prophylaxis of a calcineurin inhibitor with either mycophenolate mofetil, methotrexate or steroids from day -3 until day +30 after HSCT. Maraviroc trough levels were analyzed on day 0, +7, 14, and 21. We assessed functional CCR5 blockade by our previously described pharmacodynamic assay. In total, 17 patients were enrolled prospectively. No patient had liver GVHD by day +100. Four patients developed gastrointestinal (GI) GVHD (Grade II upper GI GVHD n = 2, grade III lower GI GVHD n = 2). No adverse effects of maraviroc were observed. Seven patients discontinued maraviroc at a median of day +14 (range day +1-day +29) due to study rules regarding hepatotoxicity (n = 5), renal function decline (n = 1) and withdrawal from study (n = 1). Maraviroc administration led to CCR5 inhibition but was limited by study rules defining hepatotoxicity, leading to frequent drug discontinuation. We cannot comment on the efficacy of maraviroc with our data but speculate that it could have a role in prevention of acute GI GVHD, with adequate compliance.

Transient antibody targeting of CD45RC inhibits the development of graft-versus-host disease

Allogeneic bone marrow transplantation (BMT) is a widely spread treatment of many hematological diseases, but its most important side effect is graft-versus-host disease (GVHD). Despite the development of new therapies, acute GVHD (aGVHD) occurs in 30% to 50% of allogeneic BMT and is characterized by the generation of effector T (Teff) cells with production of inflammatory cytokines. We previously demonstrated that a short anti-CD45RC monoclonal antibody (mAb) treatment in a heart allograft rat model transiently decreased CD45RChigh Teff cells and increased regulatory T cell (Treg) number and function allowing long-term donor-specific tolerance. Here, we demonstrated in rat and mouse allogeneic GVHD, as well as in xenogeneic GVHD mediated by human T cells in NSG mice, that both ex vivo depletion of CD45RChigh T cells and in vivo treatment with short-course anti-CD45RC mAbs inhibited aGVHD. In the rat model, we demonstrated that long surviving animals treated with anti-CD45RC mAbs were fully engrafted with donor cells and developed a donor-specific tolerance. Finally, we validated the rejection of a human tumor in NSG mice infused with human cells and treated with anti-CD45RC mAbs. The anti-human CD45RC mAbs showed a favorable safety profile because it did not abolish human memory antiviral immune responses, nor trigger cytokine release in in vitro assays. Altogether, our results show the potential of a prophylactic treatment with anti-human CD45RC mAbs in combination with rapamycin as a new therapy to treat aGVHD without abolishing the antitumor effect.

PRMT5 regulates T cell interferon response and is a target for acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is a T cell-mediated immunological disorder and the leading cause of nonrelapse mortality in patients who receive allogeneic hematopoietic cell transplants. Based on recent observations that protein arginine methyltransferase 5 (PRMT5) and arginine methylation are upregulated in activated memory T cells, we hypothesized that PRMT5 is involved in the pathogenesis of aGVHD. Here, we show that PRMT5 expression and enzymatic activity were upregulated in activated T cells in vitro and in T cells from mice developing aGVHD after allogeneic transplant. PRMT5 expression was also upregulated in T cells of patients who developed aGVHD after allogeneic hematopoietic cell transplant compared with those who did not develop aGVHD. PRMT5 inhibition using a selective small-molecule inhibitor (C220) substantially reduced mouse and human allogeneic T cell proliferation and inflammatory IFN-γ and IL-17 cytokine production. Administration of PRMT5 small-molecule inhibitors substantially improves survival, reducing disease incidence and clinical severity in mouse models of aGVHD without adversely affecting engraftment. Importantly, we show that PRMT5 inhibition retained the beneficial graft-versus-leukemia effect by maintaining cytotoxic CD8+ T cell responses. Mechanistically, we show that PRMT5 inhibition potently reduced STAT1 phosphorylation as well as transcription of proinflammatory genes, including interferon-stimulated genes and IL-17. Additionally, PRMT5 inhibition deregulates the cell cycle in activated T cells and disrupts signaling by affecting ERK1/2 phosphorylation. Thus, we have identified PRMT5 as a regulator of T cell responses and as a therapeutic target in aGVHD.

CCR5 inhibitor as novel acute graft versus host disease prophylaxis in children and young adults undergoing allogeneic stem cell transplant: results of the phase II study

We report results of a phase II study of maraviroc to prevent acute graft versus host disease (GVHD) in children undergoing allogeneic hematopoietic stem cell transplant (HSCT). Oral maraviroc was added to standard GVHD prophylaxis of a calcineurin inhibitor with either mycophenolate mofetil, methotrexate or steroids from day -3 until day +30 after HSCT. Maraviroc trough levels were analyzed on day 0, +7, 14, and 21. We assessed functional CCR5 blockade by our previously described pharmacodynamic assay. In total, 17 patients were enrolled prospectively. No patient had liver GVHD by day +100. Four patients developed gastrointestinal (GI) GVHD (Grade II upper GI GVHD n = 2, grade III lower GI GVHD n = 2). No adverse effects of maraviroc were observed. Seven patients discontinued maraviroc at a median of day +14 (range day +1-day +29) due to study rules regarding hepatotoxicity (n = 5), renal function decline (n = 1) and withdrawal from study (n = 1). Maraviroc administration led to CCR5 inhibition but was limited by study rules defining hepatotoxicity, leading to frequent drug discontinuation. We cannot comment on the efficacy of maraviroc with our data but speculate that it could have a role in prevention of acute GI GVHD, with adequate compliance.

Comparison of HLA-matched sibling and unrelated donor transplantation in adult patients with acquired severe aplastic anemia

The recent improvements in the outcomes of severe aplastic anemia (SAA) patients who received allogeneic stem cell transplantation (SCT) from unrelated donors (URD) suggest the possibility of its alternative first-line treatment. To address this issue, results of adult SAA patients receiving allogeneic SCT were compared between the following three donor-type groups: 8/8-matched sibling (MSD; n = 153), 8/8 well-matched unrelated (WM-URD; n = 72), and 6-7/8 partially matched unrelated (PM-URD; n = 33). Proportion of patients who experienced immunosuppressive treatment failures was significantly higher in the URD groups than in the MSD group (P< 0.01). The incidences of graft failure and transplant-related mortality, and graft-vs.-host disease-free, failure-free survival rates of the MSD, WM-URD, and PM-URD groups were 14.6, 0, and 0% (P< 0.01); 6.1, 10.3, and 21.7% (P= 0.03); and 76.7, 55.5, and 51.5% (P< 0.01), respectively. The overall survival (OS) rate of the MSD group (93.9%) was higher than that of the PM-URD (78.3%; P < 0.01) group, but not to that of the WM-URD (86.2%; P= 0.18) group. Our study showed comparable OS between the MSD group and WM-URD group, which suggest that the URD-SCT can be used as a first-line treatment for adult SAA patients with WM-URD.

Can we prevent or treat graft-versus-host disease with cellular-therapy?

Acute and chronic graft-versus-host disease (GvHD) are the most important causes of treatment-related morbidity and mortality after allogeneic hematopoietic cell transplants for various diseases. Corticosteroids are an effective therapy in only about one-half of affected individuals and new therapy options are needed. We discuss novel strategies to treat GvHD using cellular-therapy including adoptive transfer of regulatory T-cells (T_regs), mesenchymal stromal cells (MSCs), cells derived from placental tissues, invariant natural killer T-cells (iNKTs), and myeloid-derived suppressor cells (MDSCs).These strategies may be more selective than drugs in modulating GvHD pathophysiology, and may be safer and more effective than conventional pharmacologic therapies. Additionally, these therapies have not been observed to substantially compromise the graft-versus-tumor effect associated with allotransplants. Many of these strategies are effective in animal models but substantial data in humans are lacking.

Drug-drug interactions in patients receiving hematopoietic stem cell transplantation

INTRODUCTION

Recipients of hematopoietic stem cell transplantation (HSCT) are exposed to numerous drugs in both pre- and post-transplantation period, which creates an opportunity for drug-drug interactions (DDIs); if clinically relevant DDIs happen, the risk of adverse treatment outcomes is increased. Areas covered: This review is focused on DDIs in recipients of HSCT that were observed and published as clinical trials, case series or case reports. Relevant publications were found by the systematic search of the following online databases: MEDLINE, SCOPUS, EBSCO, and SCINDEX. Expert opinion: The most important DDIs involve cytostatic or immunosuppressant drug on one side, and antimicrobial drugs on the other. The majority of clinically relevant interactions have pharmacokinetic character, involving drug metabolizing enzymes in the liver. Antifungal azoles inhibit metabolism of many cytostatic and immunosuppressant drugs at cytochromes and increase their plasma concentrations. Macrolide antibiotics and fluoroqunolones should be avoided in HSCT recipients, as they have much larger potential for DDIs than other antibiotic groups. HSCT recipients increasingly receive new immunomodulating drugs, and further observational studies are needed to reveal unsuspected DDIs with clinical relevance.

Why is a 3-year NRM following allogeneic transplantation still stuck at approximately 20%?

Whether and when to recommend an allogeneic stem cell transplant (SCT) for a patient with leukemia is a treatment decision that rests on determining whether the transplant or non-transplant option carries the greatest probability of 3-5-year survival. While SCT confers a greater possibility of leukemia cure, the decision to transplant has to be made in the light of the high chance of treatment-related mortality (TRM) that follows the allograft. Here we identify that current estimates of a 20% 3-year TRM hold largely true for a variety of leukemias, diverse types of conditioning regimen, and varied donor-recipient compatibility across a wide age-range. While there is a wide spectrum of causes of death in the first few months after SCT, they usually stem from a limited set of immediate post-transplant complications, including those induced by the conditioning regimen, post-transplant endovascular damage, gut dysbiosis, graft-versus-host disease, and immunodeficiency causing viral reactivation. As we better understand and improve preventative treatments for these initiating events there is a real expectation that TRM will continue to fall to levels well below 10% within the next decade.

In Vitro Th17-Polarized Human CD4+ T Cells Exacerbate Xenogeneic Graft-versus-Host Disease

Acute graft-versus-host disease (aGVHD) is a severe complication of allogeneic hematopoietic stem cell transplantation. The role of Th17 cells in its pathophysiology remains a matter of debate. In this study, we assessed whether enrichment of human peripheral blood mononuclear cells (PBMCs) with in vitro Th17-polarized CD4⁺ T cells would exacerbate xenogeneic GVHD (xGVHD) into NOD-scid IL-2Rγ null (NSG) mice. Naive human CD4⁺ T cells were stimulated under Th17-skewing conditions for 8 to 10 days and then coinjected in NSG mice with fresh PBMCs from the same donor. We observed that Th17-polarized cells engrafted and migrated toward xGVHD target organs. They also acquired a double-expressing IL-17A⁺IFNγ⁺ profile in vivo. Importantly, cotransfer of Th17-polarized cells (1 × 10⁶) with PBMCs (1 × 10⁶) exacerbated xGVHD compared with transplantation of PBMCs alone (2 × 10⁶). Furthermore, PBMC cotransfer with Th17-polarized cells was more potent for xGVHD induction than cotransfer with naive CD4⁺ T cells stimulated in nonpolarizing conditions (Th0 cells, 1 × 10⁶ + 1 × 10⁶ PBMCs) or with Th1-polarized cells (1 × 10⁶ + 1 × 10⁶ PBMCs). In summary, our results suggest that human Th17-polarized cells can cooperate with PBMCs and be pathogenic in the NSG xGVHD model.

Low-Dose Anti-T Lymphoglobulin as Prophylaxis for Graft-versus-Host Disease in Unrelated Donor Transplantations for Acute Leukemias and Myelodysplastic Syndromes

Chronic graft-versus-host disease (cGVHD) is a major complication after stem cell transplantation (HSCT). Several randomized studies already demonstrated that anti-T lymphoglobulin (ATLG) is effective in preventing GVHD after myeloablative unrelated and HLA-identical sibling transplants. However, the issue of doses and the potential increase of relapses still remain unsolved. Here we report data on 190 patients with acute leukemia and myelodysplastic syndrome who underwent an unrelated HSCT with low-dose ATLG (15 to 30 mg/kg) given at an earlier timing (days -6 to -2). HSCT was performed from HLA 10/10 (n = 62, 33%), 9/10 (n = 91, 48%), 8/10 (n = 30, 16%), and <8/10 (n = 7, 4%) identical unrelated donor. Peripheral blood was the stem cell source in 42% (n = 80). Median follow-up was 51 months. Grades II to IV and III to IV acute GVHD were 26% and 9%, respectively, and 2-year overall and moderate to severe cGVHD were 23% and 14%, respectively. The 3-year incidences of relapse and nonrelapse mortality were 26% and 18%, respectively. The rates of 3-year overall survival (OS), disease-free survival (DFS), and GVHD-free and relapse-free survival (GRFS) were 60%, 56% and 44%, respectively. Factors such as younger donor, good performance status, and early disease were associated with better outcome in terms of OS, DFS, and GRFS. Our data indicate that doses of ATLG lower that those used in randomized clinical trials can be used for GVHD prevention, even in the adult setting, without clear increases in relapse and infections; these findings need to be further validated by a prospective randomized study.

Infusion of bone marrow derived multipotent mesenchymal stromal cells for the treatment of steroid-refractory acute graft-versus-host disease: a multicenter prospective study

The prognosis of steroid-refractory acute graft-versus-host disease (aGVHD) remains poor and better treatments are urgently needed. Multipotent mesenchymal stromal cell (MSC)-based therapy emerged as a promising approach but response rates were highly variable across studies. We conducted a multicenter prospective study assessing the efficacy of 1-2 infusion(s) of cryopreserved, third-party donor bone marrow-derived MSCs for treating grade II-IV steroid-refractory or -dependent aGVHD in a series of 33 patients. MSCs were produced centrally and distributed to 8 hospitals throughout Belgium to be infused in 2 consecutive cohorts of patients receiving 1-2 or 3-4 × 106 MSCs/kg per dose, respectively. All patients received MSCs as the first rescue therapy after corticosteroids, with the exception for one patient who received prior treatment with mycophenolate mofetil (that was still ongoing by the time of MSC therapy). In these conditions, MSC therapy resulted in at least a partial response in 13 patients (40.6%) at day 30 and in 15 patients (46%) within 90 days after first MSC infusion. The corresponding complete response rates were 21.6% (7 patients) and 30% (10 patients), respectively. Only 5 patients achieved a sustained complete response, lasting for at least 1 month. The 1-year overall survival was 18.2% (95% CI: 8.82-37.5%). Higher response and survival rates were observed among patients receiving 3-4 × 106 MSCs/kg for first infusion, as compared with patients receiving 1-2 × 106 MSCs/ kg. Response and survival with MSC therapy for SR/SD-aGVHD remains to be optimized.

CD28 Blockade Ex Vivo Induces Alloantigen-Specific Immune Tolerance but Preserves T-Cell Pathogen Reactivity

Donor T-cells contribute to reconstitution of protective immunity after allogeneic hematopoietic stem cell transplantation (HSCT) but must acquire specific tolerance against recipient alloantigens to avoid life-threatening graft-versus-host disease (GvHD). Systemic immunosuppressive drugs may abrogate severe GvHD, but this also impedes memory responses to invading pathogens. Here, we tested whether ex vivo blockade of CD28 co-stimulation can enable selective T-cell tolerization to alloantigens by facilitating CD80/86-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) signaling. Treatment of human allogeneic dendritic cell/T-cell co-cultures with a human CD28 blocking antibody fragment (α-huCD28) significantly abrogated subsequent allospecific immune responses, seen by decreased T-cell proliferation and of type 1 cytokine (IFN-γ and IL-2) expression. Allo-tolerization persisted after discontinuation of CD28 blockade and secondary alloantigen stimulation, as confirmed by enhanced CTLA-4 and PD-1 immune checkpoint signaling. However, T-cells retained reactivity to pathogens, supported by clonotyping of neo-primed and cross-reactive T-cells specific for Candida albicans or third-party antigens using deep sequencing analysis. In an MHC-mismatched murine model, we tolerized C57BL/6 T-cells by ex vivo exposure to a murine single chain Fv specific for CD28 (α-muCD28). Infusion of these cells, after α-muCD28 washout, into bone marrow-transplanted BALB/c mice caused allo-tolerance and did not induce GvHD-associated hepatic pathology. We conclude that selective CD28 blockade ex vivo can allow the generation of stably allo-tolerized T-cells that in turn do not induce graft-versus-host reactions while maintaining pathogen reactivity. Hence, CD28 co-stimulation blockade of donor T-cells may be a useful therapeutic approach to support the immune system after HSCT.

Azacytidine prevents experimental xenogeneic graft-versus-host disease without abrogating graft-versus-leukemia effects

The demethylating agent 5-azacytidine (AZA) has proven its efficacy in the treatment of myelodysplastic syndrome and acute myeloid leukemia. In addition, AZA can demethylate FOXP3 intron 1 (FOXP3i1) leading to the generation of regulatory T cells (Treg). Here, we investigated the impact of AZA on xenogeneic graft-vs.-host disease (xGVHD) and graft-vs.-leukemia effects in a humanized murine model of transplantation (human PBMCs-infused NSG mice), and described the impact of the drug on human T cells in vivo. We observed that AZA improved both survival and xGVHD scores. Further, AZA significantly decreased human T-cell proliferation as well as IFNγ and TNF-α serum levels, and reduced the expression of GRANZYME B and PERFORIN 1 by cytotoxic T cells. In addition, AZA significantly increased Treg frequency through hypomethylation of FOXP3i1 as well as increased Treg proliferation. The latter was subsequent to higher STAT5 signaling in Treg from AZA-treated mice, which resulted from higher IL-2 secretion by conventional T cells from AZA-treated mice itself secondary to demethylation of the IL-2 gene promoter by AZA. Importantly, Tregs harvested from AZA-treated mice were suppressive and stable over time since they persisted at high frequency in secondary transplant experiments. Finally, graft-vs.-leukemia effects (assessed by growth inhibition of THP-1 cells, transfected to express the luciferase gene) were not abrogated by AZA. In summary, our data demonstrate that AZA prevents xGVHD without abrogating graft-vs.-leukemia effects. These findings could serve as basis for further studies of GVHD prevention by AZA in acute myeloid leukemia patients offered an allogeneic transplantation.

Limited Impact of Imatinib in a Murine Model of Sclerodermatous Chronic Graft-versus-Host Disease

BACKGROUND

Sclerodermatous chronic Graft-versus-Host Disease (scl-cGVHD) is one of the most severe form of cGVHD. The Platelet-derived Grotwth Factor (PDGF) and the Transforming Growth Factor-β (TGF-β) play a significant role in the fibrosing process occurring in scl-cGVHD. This prompted us to assess the impact of the PDGF-r and c-Abl tyrosine kinase inhibitor imatinib on scl-cGVHD.

METHODS

To assess the impact of imatinib on T cell subset proliferation in vivo, Balb/cJ recipient mice were lethally (7 Gy) irradiated and then injected with 10x106 bone marrow cells from B10.D2 mice on day 0. Fourteen days later, 70x106 carboxyfluorescein succinimidyl ester (CFSE)-labeled splenocytes from B10.D2 mice were infused and imatinib or sterile water was administered for 5 days. To induce severe scl-cGVHD, Balb/cJ mice were injected i.v. with 10.106 bone marrow cells and 70.106 splenocytes from B10.D2 donor mice after 7 Gy irradiation. Mice were then given sterile water or imatinib from day +7 after transplantation to the end of the experiment (day +52).

RESULTS

Imatinib decreased the proliferation of total T cells (P = 0.02), CD8+ T cells (P = 0.01), and of regulatory T cells (Tregs) (P = 0.02) in the spleen. In the severe scl-cGVHD model, imatinib-treated mice had significantly lower levels of PDGF-r phosphorylation than control mice on day 29 after transplantation (P = 0.008). However, scl-cGVHD scores were similar between vehicle- and imatinib-treated mice during the whole experiment, while there was a suggestion for less weight loss in imatinib-treated mice that reached statistical significance at day +52 following transplantation (P = 0.02).

CONCLUSIONS

Imatinib had a limited impact in murine scl-cGVHD despite significant inhibition of PDGF-r.