Biomarkers for Early Complications of Endothelial Origin After Allogeneic Hematopoietic Stem Cell Transplantation: Do They Have a Potential Clinical Role?

Hemostasis and complement in allogeneic hematopoietic stem cell transplantation: clinical significance of two interactive systems

Hematopoietic stem cell transplantation (HCT) represents a curative treatment option for certain malignant and nonmalignant hematological diseases. Conditioning regimens before HCT, the development of graft-versus-host disease (GVHD) in the allogeneic setting, and delayed immune reconstitution contribute to early and late complications by inducing tissue damage or humoral alterations. Hemostasis and/or the complement system are biological regulatory defense systems involving humoral and cellular reactions and are variably involved in these complications after allogeneic HCT. The hemostasis and complement systems have multiple interactions, which have been described both under physiological and pathological conditions. They share common tissue targets, such as the endothelium, which suggests interactions in the pathogenesis of several serious complications in the early or late phase after HCT. Complications in which both systems interfere with each other and thus contribute to disease pathogenesis include transplant-associated thrombotic microangiopathy (HSCT-TMA), sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), and GVHD. Here, we review the current knowledge on changes in hemostasis and complement after allogeneic HCT and how these changes may define clinical impact.

Safety and efficacy of G-CSF after allogeneic hematopoietic cell transplantation using post-transplant cyclophosphamide: clinical and in vitro examination of endothelial activation

Since 2021 the use of G-CSF was implemented in allo-HCT with PTCY-based prophylaxis with the aim of shortening the aplastic phase and reducing infectious complications. This study investigates the effectiveness of this change in protocol performed at our institution. One-hundred forty-six adults undergoing allo-HCT with PTCY-based prophylaxis were included, and among them, 58 (40%) received G-CSF. The median of days to neutrophil engraftment was shorter in the G-CSF group (15 vs. 20 days, p < 0.001). Patients receiving G-CSF had a lower incidence of day +30 bacterial bloodstream infections (BSI) than the rest (20.7% vs. 47.7%, p < 0.001). GVHD, SOS, and TA-TMA incidences were comparable between groups, and using G-CSF did not impact on survival. Endothelial activation was investigated using EASIX and by the measurement of soluble biomarkers in cryopreserved plasma samples obtained on days 0, +7, +14 and +21 of 39 consecutive patients (10 received G-CSF) included in the study. EASIX, VWF:Ag, sVCAM-1, sTNFRI, ST2, REG3α, TM and NETs medians values were comparable in patients receiving G-CSF and those who did not. Compared with allo-HCT performed without G-CSF, the addition of G-CSF to PTCY-based allo-HCT accelerated neutrophil engraftment contributing on decreasing BSI incidence, and without inducing additional endothelial activation.

D-dimer and sinusoidal obstructive syndrome-novel poor prognostic features of thrombotic microangiopathy in children after hematopoietic cellular therapy in a single institution prospective cohort study

Transplant-associated thrombotic microangiopathy (TA-TMA) is a common, severe complication of allogeneic hematopoietic cellular therapy (HCT). Even when treated in many studies, morbidity and mortality rates are high. This prospective single-institution cohort study serially enrolled all allogeneic HCT recipients from August 2019-August 2022. Patients were universally screened for TA-TMA and intermediate and high-risk patients were immediately treated with eculizumab. Sub-distribution cox-proportional hazards models were used to identify sub-distribution hazard ratios (sHR)  for multi-organ dysfunction (MOD) and non-relapse-related mortality (NRM). Of 136 patients, 36 (26%) were diagnosed with TA-TMA and 21/36 (58%) developed MOD, significantly more than those without TA-TMA, (p < .0001). Of those with TA-TMA, 18 (50%) had high-risk TA-TMA (HR-TA-TMA), 11 (31%) had intermediate-risk TA-TMA (IR-TA-TMA), and 8 (22%) had standard risk (SR-TA-TMA). Twenty-six were treated with eculizumab (1/8 SR, 7/11 IR, and 18/18 HR). Elevated D-dimer predicted the development of MOD (sHR 7.6, 95% confidence interval [CI] 1.8-32.3). Children with concurrent sinusoidal obstructive syndrome (SOS) and TA-TMA had an excess risk of MOD of 34% and data supported a biologic interaction. The adjusted NRM risk was significantly higher in the TA-TMA patients (sHR 10.54, 95% CI 3.8-29.2, p < .0001), despite prompt treatment with eculizumab. Significant RF for NRM in TA-TMA patients included SOS (HR 2.89, 95% 1.07-7.80) and elevated D-dimer (HR 3.82, 95% CI 1.14-12.84). An unrelated donor source and random urine protein to creatine ratio ≥2 mg/mg were significantly associated with no response to eculizumab (odds ratio 15, 95% CI 2.0-113.6 and OR 6.5, 95% CI 1.1-38.6 respectively). TA-TMA was independently associated with NRM despite early diagnosis and treatment with eculizumab in this large pediatric transplant cohort. Prognostic implications of D-dimer in TA-TMA merit further investigation as this is a readily accessible biomarker. Concurrent SOS is an exclusion criterion of many ongoing clinical trials, but these data highlight these patients could benefit from novel therapeutic approaches. Multi-institutional clinical trials are needed to understand the impact of TA-TMA-targeted therapies.

Endothelial Activation and Stress Index in adults undergoing allogeneic hematopoietic cell transplantation with post-transplant cyclophosphamide-based prophylaxis

BACKGROUND AIMS

Post-transplant cyclophosphamide (PTCY)-based prophylaxis is becoming widespread for allogeneic hematopoietic cell transplantation (allo-HCT) performed independently of the selected donor source. In parallel, use of the Endothelial Activation and Stress Index (EASIX)-considered a surrogate parameter of endothelial activation-for predicting patient outcomes and clinical complications is gaining popularity in the allo-HCT setting.

METHODS

We first investigated whether the dynamics of EASIX after allo-HCT differ between patients receiving PTCY and patients receiving other prophylaxis. We then investigated whether the predictive capacity of EASIX persists in PTCY-based allo-HCT. A total of 328 patients transplanted between 2014 and 2020 were included, and 201 (61.2%) received PTCY.

RESULTS

EASIX trends differed significantly between the groups. Compared with patients receiving other prophylaxis, patients receiving PTCY had lower EASIX on day 0 and higher values between day 7 and day 100. In patients receiving PTCY, higher EASIX correlated significantly with higher non-relapse mortality (NRM) and lower overall survival (OS) when measured before and during the first 180 days after allo-HCT. In addition, higher EASIX scores measured at specific time points were predictors of veno-occlusive disease (VOD), transplant-associated thrombotic microangiopathy (TA-TMA) and grade 2-4 acute graft-versus-host disease (aGVHD) risk.

CONCLUSIONS

This study demonstrates how EASIX trends vary during the first 180 days after allo-HCT in patients receiving PTCY and those not receiving PTCY and validates the utility of this index for predicting NRM, OS and risk of VOD, TA-TMA and grade 2-4 aGVHD in patients receiving PTCY.

Chemotherapy-Associated Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a syndrome of microangiopathic hemolytic anemia and thrombocytopenia with end-organ dysfunction. Although the advent of plasma exchange, immunosuppression, and complement inhibition has improved morbidity and mortality for primary TMAs, the management of secondary TMAs, particularly drug-induced TMA, remains less clear. TMA related to cancer drugs disrupts the antineoplastic treatment course, increasing the risk of cancer progression. Chemotherapeutic agents such as mitomycin-C, gemcitabine, and platinum-based drugs as well as targeted therapies such as antiangiogenesis agents and proteasome inhibitors have been implicated in oncotherapy-associated TMA. Among TMA subtypes, drug-induced TMA is less well-understood. Treatment generally involves withdrawal of the offending agent and supportive care targeting blood pressure and proteinuria reduction. Immunosuppression and therapeutic plasma exchange have not shown clear benefit. The terminal complement inhibitor, eculizumab, has shown promising results in some cases of chemotherapy-associated TMA including in re-exposure. However, the data are limited, and unlike in primary atypical hemolytic uremic syndrome, the role of complement in the pathogenesis of drug-induced TMA is unclear. Larger multicenter studies and unified definitions are needed to elucidate the extent of the problem and potential treatment strategies.

Biomarkers for early complications post hematopoietic cell transplantation: Insights and challenges

Hematopoietic cell transplantation is an established curative treatment option for various hematological malignant, and non-malignant diseases. However, the success of HCT is still limited by life-threatening early complications post-HCT, such as Graft Versus Host Disease (GVHD), Sinusoidal Obstruction Syndrome (SOS), and transplant-associated microangiopathy, to name a few. A decade of research in the discovery and validation of novel blood-based biomarkers aims to manage these early complications by using them for diagnosis or prognosis. Advances in this field have also led to predictive biomarkers to identify patients' likelihood of response to therapy. Although biomarkers have been extensively evaluated for different complications, these are yet to be used in routine clinical practice. This review provides a detailed summary of various biomarkers for individual early complications post-HCT, their discovery, validation, ongoing clinical trials, and their limitations. Furthermore, this review also provides insights into the biology of biomarkers and the challenge of obtaining a universal cut-off value for biomarkers.

The Importance of New EBMT Criteria on the Diagnosis of Veno-Occlusive Liver Disease in Children

BACKGROUND

Early recognition and specific therapy facilitate a favorable disease course in hepatic venous-occlusive disease (HVOD) following hematopoietic stem cell transplantation (HCT). Diagnostic and classification criteria, published by the European Society for Blood and Marrow Transplantation (EBMT), better account for clinical differences in disease presentation in pediatric populations.

OBJECTIVES

To compare the course of HVOD in children before and after the implementation of new EBMT criteria.

MATERIAL AND METHODS

The study retrospectively evaluates 26 HVODs in 179 children treated in a single HCT unit (Slovakia) comparing the period of 2014-2017 using the Baltimore and modified Seattle criteria with the period of 2018-2021, when new EBMT criteria were adopted.

RESULTS

No difference in HVOD incidence (11.2% vs. 14.8%, p = 0.46) and in time of diagnosis post-HCT (15.6 days vs. 15.7 days, p = 0.75) was found. With EBMT criteria we observed more frequent anicteric disease at diagnosis (50% vs. 87.5%, p = 0.04), lower serum bilirubin at diagnosis (3.4 mg/dL vs. 1.23 mg/dL, p = 0.045), and non-significant trends of shorter defibrotide treatment (21.7 days vs. 15.6 days, p = 0.73), decreased mortality (30% vs. 6.2%, p = 0.10) and shorter hospitalization (73.1 days vs. 59.6 days, p = 0.54).

CONCLUSIONS

Different time periods around the implementation of new criteria are evaluated, underling that pediatric EBMT criteria for post-transplant HVOD diagnosis appear more sensitive.

Low Plasma Levels of Hyaluronic Acid Might Rule Out Sinusoidal Obstruction Syndrome after Hematopoietic Stem Cell Transplantation

Background

Sinusoidal obstructive syndrome (SOS) is a potentially fatal complication secondary to hematopoietic stem cell transplant (HSCT) conditioning. Endothelial damage plasma biomarkers such as plasminogen activator inhibitor-1 (PAI-1), hyaluronic acid (HA), and vascular adhesion molecule-1 (VCAM1) represent potential diagnostic tools for SOS.

Methods

We prospectively collected serial citrated blood samples (baseline, day 0, day 7, and day 14) in all adult patients undergoing HSCT at La Paz Hospital, Madrid. Samples were later analyzed by ELISA (enzyme-linked immunosorbent assay) for HA, VCAM1, and PAI-1 concentrations.

Results

During sixteen months, we prospectively recruited 47 patients. Seven patients (14%) were diagnosed with SOS according to the EBMT criteria for SOS/VOD diagnosis and received treatment with defibrotide. Our study showed a statistically significant elevation of HA on day 7 in SOS patients, preceding clinical SOS diagnosis, with a sensitivity of 100%. Furthermore, we observed a significant increase of HA and VCAM1 levels on day 14. Regarding risk factors, we observed a statistically significant association between SOS diagnosis and the fact that patients received 3 or more previous lines of treatment before HSCT.

Conclusions

The early significant increase in HA levels observed opens the door to a noninvasive peripheral blood test which could have the potential to improve diagnosis and facilitate prophylactic and therapeutic management of SOS before clinical/histological damage is established.

Role of therapeutic drug monitoring of intravenous Busulfan for prevention of sinusoidal obstructive syndrome in children

BACKGROUND

Therapeutic drug monitoring (TDM) of intravenous busulfan (Bu) has been recommended for safe engraftment and decreased toxicity in children undergoing hematopoietic stem cell transplantation (HSCT). This study aims to compare HSCT-related outcomes, such as acute or chronic graft-versus-host disease (GvHD), sinusoidal obstructive syndrome (SOS), event-free survival (EFS), and overall survival (OS) in children with and without TDM for busulfan.

METHODS

This retrospective study conducted between February 2012 and February 2021 at our Bone Marrow Transplantation Unit included 172 patients (34% girls) with a median age of 4.70 years (IQR 2.41-10.01). Group A consisted of 46 patients whose Bu doses were adjusted according to actual body weight, and group B consisted of 126 patients whose Bu dose adjustments made according to TDM.

RESULTS

Totally, 32 patients (19%) developed moderate or severe SOS. The incidence of SOS was significantly higher in the group without TDM (29% vs. 15%, p = .041). A multivariable analysis showed that the presence of acute GvHD and one alkylating drug-containing conditioning regimen compared with two or three were associated with SOS (p = .03 and p = .002, respectively). In patients with TDM, cumulative Bu dose and area under curve also were not associated with SOS. Other HSCT-related outcomes such as acute or chronic GvHD, relapse and graft rejection rates, OS and EFS rates did not differ between the groups.

CONCLUSIONS

TDM and making dose adjustments with Bayesian forecasting over four days of Bu therapy optimizes exposure and reduces the risk of SOS in children undergoing HSCT.

Endocan in Acute Leukemia: Current Knowledge and Future Perspectives

Endocan is a soluble dermatan sulfate proteoglycan expressed by endothelial cells and detected in serum/plasma. Its expression is increased in tumors/tumor vessels in several human malignancies, and high expression (high serum/plasma levels or tumor levels) has an adverse prognostic impact in several malignancies. The p14 endocan degradation product can also be detected in serum/plasma, but previous clinical studies as well as previously unpublished results presented in this review suggest that endocan and p14 endocan fragment levels reflect different biological characteristics, and the endocan levels seem to reflect the disease heterogeneity in acute leukemia better than the p14 fragment levels. Furthermore, decreased systemic endocan levels in previously immunocompetent sepsis patients are associated with later severe respiratory complications, but it is not known whether this is true also for immunocompromised acute leukemia patients. Finally, endocan is associated with increased early nonrelapse mortality in (acute leukemia) patients receiving allogeneic stem cell transplantation, and this adverse prognostic impact seems to be independent of the adverse impact of excessive fluid overload. Systemic endocan levels may also become important to predict cytokine release syndrome after immunotherapy/haploidentical transplantation, and in the long-term follow-up of acute leukemia survivors with regard to cardiovascular risk. Therapeutic targeting of endocan is now possible, and the possible role of endocan in acute leukemia should be further investigated to clarify whether the therapeutic strategy should also be considered.

Endothelial Dysfunction after Hematopoietic Stem Cell Transplantation: A Review Based on Physiopathology

Endothelial dysfunction (ED) is frequently encountered in transplant medicine. ED is an argument of high complexity, and its understanding requires a wide spectrum of knowledge based on many fields of basic sciences such as molecular biology, immunology, and pathology. After hematopoietic stem cell transplantation (HSCT), ED participates in the pathogenesis of various complications such as sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), graft-versus-host disease (GVHD), transplant-associated thrombotic microangiopathy (TA-TMA), idiopathic pneumonia syndrome (IPS), capillary leak syndrome (CLS), and engraftment syndrome (ES). In the first part of the present manuscript, we briefly review some biological aspects of factors involved in ED: adhesion molecules, cytokines, Toll-like receptors, complement, angiopoietin-1, angiopoietin-2, thrombomodulin, high-mobility group B-1 protein, nitric oxide, glycocalyx, coagulation cascade. In the second part, we review the abnormalities of these factors found in the ED complications associated with HSCT. In the third part, a review of agents used in the treatment of ED after HSCT is presented.

Extracellular Vesicles as Biomarkers of Acute Graft-vs.-Host Disease After Haploidentical Stem Cell Transplantation and Post-Transplant Cyclophosphamide

Even with high-dose post-transplant cyclophosphamide (PT-Cy) which was initially introduced for graft-versus-host disease (GvHD) prevention in the setting of HLA-haploidentical transplantation, both acute and chronic GvHDs remain a major clinical challenge. Despite improvements in the understanding of the pathogenesis of both acute and chronic GvHDs, reliable biomarkers that predict their onset have yet to be identified. We recently studied the potential correlation between extracellular vesicles (EVs) and the onset of acute (a)GvHD in transplant recipients from related and unrelated donors. In the present study, we further investigated the role of the expression profile of membrane proteins and their microRNA (miRNA) cargo (miRNA100, miRNA155, and miRNA194) in predicting the onset of aGvHD in haploidentical transplant recipients with PT-Cy. Thirty-two consecutive patients were included. We evaluated the expression profile of EVs, by flow cytometry, and their miRNA cargo, by real-time PCR, at baseline, prior, and at different time points following transplant. Using logistic regression and Cox proportional hazard models, a significant association between expression profiles of antigens such as CD146, CD31, CD140a, CD120a, CD26, CD144, and CD30 on EVs, and their miRNA cargo with the onset of aGvHD was observed. Moreover, we also investigated a potential correlation between EV expression profile and cargo with plasma biomarkers (e.g., ST2, sTNFR1, and REG3a) that had been associated with aGVHD previously. This analysis showed that the combination of CD146, sTNFR1, and miR100 or miR194 strongly correlated with the onset of aGvHD (AUROC >0.975). A large prospective multicenter study is currently in progress to validate our findings.

Early vascular endothelial complications after hematopoietic cell transplantation: Role of the endotheliopathy in biomarkers and target therapies development

This work aims to review the role of endothelial dysfunction underlying the main complications appearing early after autologous and allogeneic hematopoietic cell transplantation (HCT). The endothelial damage as the pathophysiological substrate of sinusoidal obstruction syndrome (SOS) is well established. However, there is growing evidence of the involvement of endothelial dysfunction in other complications, such as acute graft-versus-host disease (aGVHD) and transplant-associated thrombotic microangiopathy (TA-TMAs). Moreover, HCT-related endotheliopathy is not only limited to the HCT setting, as there is increasing evidence of its implication in complications derived from other cellular therapies. We also review the incidence and the risk factors of the main HCT complications and the biological evidence of the endothelial involvement and other linked pathways in their development. In addition, we cover the state of the art regarding the potential use of the biomarkers of endotheliopathy in the prediction, the early diagnosis, and the follow-up of the HCT complications and summarize current knowledge points to the endothelium and the other linked pathways described as potential targets for the prevention and treatment of HCT-complications. Lastly, the endothelium-focused therapeutic strategies that are emerging and might have a potential impact on the survival and quality of life of post-HCT-patients are additionally reviewed.