Review of Haploidentical Hematopoietic Cell Transplantation

Donor's age influences outcome in haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide - a single center experience

Haploidentical stem cell transplantation (haplo-SCT) using post-transplantation cyclophosphamide (post-Cy) is considered a reasonable therapeutic option for patients who lack matched donor or who urgently need transplant procedure due to high risk disease. We analyzed the results of haplo-SCT performed in years 2018-2023. Eighty one patients (46 males) at median age of 52 years underwent haplo-SCT using peripheral blood as a stem cell source in most cases. Indications included hematological malignancies (acute leukemias in 88% of cases). In 25 cases (31%) transplantation was performed in relapsed/refractory disease. Majority of patients (61%) presented with very high and high disease risk index (DRI). Conditioning regimens were as follows: nonmyeloablative - 46 cases (57%), myeloablative - in 18 (22%) and reduced intensity - 17(20%). 90% of patients engrafted. All patients received unified immunosuppressive treatment (post-Cy/TAC/MMF). Median follow-up time was 12 months The cumulative incidence of acute and chronic GVHD was 37.5% and 37.6%, respectively. Estimated 2-year overall survival (OS) was 43.1% and donor's age was the only factor influencing survival. The 2-year progression-free survival (PFS) was 42.5%, whereas relapse incidence (RI) - 35%. The cumulative incidence of non-relapse mortality (NRM) was 44% and was mostly due to infections. Haplo-SCT is a feasible treatment option for hematological patients. Younger donor improves post-transplant survival. Strategies to reduce infection-related mortality and relapse rate remain a challenge.

Clinical and Economic Impact of CMV Infection in Allogeneic Hematopoietic Stem Cell Transplantation: Perspectives from a Middle-Income Nation

BACKGROUND

Cytomegalovirus infection (CMV) is a common complication after allogeneic hematopoietic stem cell transplantation (AHSCT). CMV infection increases transplantation costs; however, the extent of the financial burden may vary in different countries. This study aims to determine the clinical and economic impact of CMV infection in patients undergoing AHSCT in a middle-income country.

METHODS

A total of 150 adult and pediatric patients post-AHSCT were included for analysis. In addition to incidence of CMV infections, data on graft versus host disease (GVHD) were also collected. Standard hospital charges for AHSCT and any additional transplantation-related expenditure within 12 months were also retrieved in 104 patients.

RESULTS

CMV infection, acute GVHD and chronic GVHD occurred in 38.7%, 60.7%, and 22.0% of patients, respectively. Patients with CMV infections had higher readmission rates compared to those who did not (67.2% vs. 47.8%; p = 0.020). Additional expenditure was seen in HLA-haploidentical AHSCT and CMV infection (MYR11 712.25/USD2 504.49; p < 0.0001 and MYR5 807.24/USD1 241.79; p = 0.036), respectively.

CONCLUSION

This single-center study demonstrated that patients who underwent HLA-haploidentical AHSCT and subsequently developed CMV infection had higher transplantation expenditures compared to those who had matched-related transplantation. Further studies should be conducted to evaluate if primary prophylaxis against CMV is cost-effective, especially in patients who undergo HLA-haploidentical AHSCT.

Posterior reversible encephalopathy syndrome in immunocompromised children - A single-center study from South India

This study describes the profile of children diagnosed with posterior reversible encephalopathy syndrome (PRES) in the pediatric hematology oncology unit and highlights the clinical features of PRES in immunosuppressed children. This retrospective study included 10 children diagnosed with PRES with a mean age of 6.8 years. Acute lymphoblastic leukemia was the most common primary diagnosis followed by post-hematopoietic stem cell transplant patients. Most cases of PRES occurred within one month of treatment initiation. Hypertension was noted in all at the time of diagnosis. Neuroimaging revealed bilateral lesions with parietal and occipital lobe involvement being the most common. All patients received corticosteroids as part of treatment for primary diagnosis. Controlling blood pressure was critical in managing PRES. Consideration of PRES as a clinical possibility in pediatric hematology oncology unit in children presenting with symptoms such as headache, seizures, and visual disturbances will aid in early diagnosis after ruling out other causes of these symptoms.

Nephrons and non-relapse mortality: simplified comorbidity index and acute kidney injury are associated with NRM in adults undergoing allogeneic hematopoietic cell transplant

The Simplified Comorbidity Index (SCI) is a recently published 5-component, pre-transplant tool to predict non-relapse mortality (NRM) in allogeneic hematopoietic cell transplantation (alloHCT) patients. The SCI captures chronic kidney disease (CKD) using estimated glomerular filtration rate (eGFR) based on the CKD-EPI equation (KDIGO 2021 CKD-EPI), which may be more sensitive to predict risk of NRM than the creatinine cut-off in the 16-component, Hematopoietic Cell Transplant-Comorbidity Index (HCT-CI). We retrospectively assessed the ability of the SCI to risk-stratify patients and the impact of acute kidney injury (AKI) to NRM in adults who underwent alloHCT at the University of Minnesota. We included 373 patients who underwent their first alloHCT between 2015 and 2019. Through multivariate analysis, we found that patients with an SCI of greater than 4 had a higher risk of NRM. Additionally, we noted that AKIs stages 2-3 prior to day +100 was independently associated with a 3-fold greater NRM than patients who did not experience clinically significant AKI.

Low-dose anti-thymocyte globulin plus low-dose post-transplant cyclophosphamide-based regimen for prevention of graft-versus-host disease after haploidentical peripheral blood stem cell transplants: a large sample, long-term follow-up retrospective study

Introduction

The novel low-dose anti-thymocyte (ATG, 5 mg/kg) plus low-dose post-transplant cyclophosphamide (PTCy, 50 mg/kg) (low-dose ATG/PTCy)-based regimen had promising activity for prevention of graft-versus-host disease (GVHD) in haploidentical-peripheral blood stem cell transplantation (haplo-PBSCT), but its impacts on long-term outcomes remain to be defined.

Methods

We performed a large sample, long-term follow-up retrospective study to evaluate its efficacy for GVHD prophylaxis.

Results

The study enrolled 260 patients, including 162 with myeloid malignancies and 98 with lymphoid malignancies. The median follow-up time was 27.0 months. For the entire cohort, the cumulative incidences (CIs) of grade II-IV and III-IV acute GVHD (aGVHD) by 180 days were 13.46% (95% CI, 9.64%-17.92%) and 5.77% (95% CI, 3.37%-9.07%); while total and moderate/severe chronic GVHD (cGVHD) by 2 years were 30.97% (95% CI, 25.43%-36.66%) and 18.08% (95% CI, 13.68%-22.98%), respectively. The 2-year overall survival (OS), relapse-free survival (RFS), GVHD-free, relapse-free survival (GRFS), non-relapse mortality (NRM), and CIs of relapse were 60.7% (95% CI, 54.8%-67.10%), 58.1% (95% CI, 52.2%-64.5%), 50.6% (95% CI, 44.8-57.1%), 23.04% (95% CI, 18.06%-28.40%), and 18.09% (95% CI, 14.33%-23.97%, respectively. The 1-year CIs of cytomegalovirus (CMV) and Epstein-Barr virus (EBV) reactivation were 43.46% (95% CI, 37.39%-49.37%) and 18.08% (95% CI, 13.68%-22.98%), respectively. In multivariate analysis, the disease status at transplantation was associated with inferior survivor outcomes for all patients and myeloid and lymphoid malignancies, while cGVHD had superior outcomes for all patients and myeloid malignancies, but not for lymphoid malignancies.

Discussion

The results demonstrated that the novel regimen could effectively prevent the occurrence of aGVHD in haplo-PBSCT.

Haploidentical stem cell transplantation with post-transplant cyclophosphamide challenges and outcome from a tertiary care center in Lebanon

This letter describes the experience of the American University of Beirut Medical Center in Lebanon with haploidentical stem cell transplant (haplo-SCT) for hematological malignancies in adult patients. Haplo-SCT made it possible through universal and rapid donor availability for most of the adult patients with leukemia or lymphoma not only in the Middle East but also globally. Moreover, the use of post-transplant cyclophosphamide (PTCy) and reduced intensity conditioning (RIC) regimens when indicated improved the outcome and decreased the toxicity of haploidentical stem cell transplant.RIC regimens also allowed its use in the elderly population. Patients from throughout the Middle East come to our center, the American university of Beirut Medical Center, to receive this transformative type of stem cell transplant. In this paper, we discuss the results of haplo-SCT with PTCy done on adult patients with hematological malignancies in our center from 2015 to 2021. The results are encouraging and show that haplo-SCT should be considered more often in the Middle Eastern countries. The subgroup analysis showed the importance of achieving complete remission of the disease prior to transplant to improve outcomes in our center. There is a paucity of literature on the outcomes of haplo-SCT in the Middle East which may contribute to the limited number of centers that offer this type of SCT. Herein, we aim to fill this gap in the hopes of encouraging the implementation of this potentially curative modality of treatment to a larger extent in the Middle East.

Clinical Outcomes of Unrelated Umbilical Cord Blood Graft vs. Haploidentical Donor Transplantation: Critical Issues for an Adequate Comparison

Unrelated umbilical cord blood (UCB) and haploidentical grafts have been used for allogeneic hematopoietic stem and progenitor cell (HSPC) transplantation in patients without a related or non-related human leukocyte antigen (HLA)-matched donor. The less stringent HLA-matching requirement in both sources raises an important possibility for patients in need of urgent transplantation to treat any hematological disease. Selection of the best alternative donor is a difficult task that will depend on donor criteria, center experience, patient disease conditions, and risk, among others. Most comparisons available in scientific publications between both graft sources are obtained from retrospective analysis in wide time windows and a heterogeneous number of patients, types of disease, disease stages, previous treatments, graft source, conditioning regimen, graft vs. host disease (GVHD) approach, and evaluable endpoints. There is also an evident impact of the economic traits since low-income countries must consider less expensive treatments to satisfy the needs of the patients in the most effective possible path. Therefore, haploidentical transplantation could be an appealing option, even though it has not been completely established if any chronic treatment derived from the procedure could become a higher cost. In Colombia, there is a huge experience in UCB transplantation especially in units of pediatric transplantation where benign indications are more common than in adults. Due to the availability of a public UCB bank and HLA high-resolution typing in Colombia, there is a wider inventory of cord blood donors. Unfortunately, we do not have an unrelated bone marrow donor registry, so UCB is an important source along with haploidentical transplantation to consider in decision-making. This minireview focuses on comparing the main issues associated with the use of both HSCP sources and provides tools for physicians who face the difficult decision between these alternative donor sources.

Use of high-dose mesna and hyperhydration leads to lower incidence of hemorrhagic cystitis after posttransplant cyclophosphamide-based allogeneic transplantation

Currently, there is no consensus on best practices to prevent hemorrhagic cystitis (HC) in patients receiving posttransplant cyclophosphamide (PTCy). We retrospectively reviewed 194 patients undergoing their first hematopoietic cell transplant (HCT) who received PTCy from 2014 to 2018 to describe the incidence and severity of HC, identify potential risk factors, and impact of HC on HCT outcomes. Standard HC prophylaxis was hyperhydration with forced diuresis and mesna at 320% the daily dose of PTCy. Incidence of HC was 31.4% at day +100 of HCT. Median onset of HC was 12 days with 11.5% grade 3 HC and no Grade 4 HC. Patients with chemical HC experienced earlier onset (7 days vs. 34 days, p < 0.001) with a shorter median resolution time (5 days vs. 14 days, p = 0.001) when compared to BK-associated HC. In multivariate analysis, age above 60 years (HR 4.16, p = 0.006) and myeloablative conditioning (HR 2.44, p = 0.054) were associated with higher risk for HC, but overall, HC did not affect nonrelapse mortality or overall survival. In conclusion, hyperhydration with forced diuresis combined with aggressive mesna dosing is an effective strategy in preventing severe PTCy-associated HC, subsequently preventing any negative impact on transplant outcome.

Pre-infusion single-dose mesenchymal stem cells promote platelet engraftment and decrease severe acute graft versus host disease without relapse in haploidentical peripheral blood stem cell transplantation

Background

Mesenchymal stem cells (MSCs) may be used to treat steroid-refractory graft versus host disease (GVHD). However, the effects of MSCs in haploidentical peripheral blood stem cell transplantation (haplo-PBSCT) have not been confirmed in randomized studies.

Methods

We conducted a randomized clinical study to investigate the effects of pre-infusion (1 × 10⁶ cells/kg) MSCs on hematopoietic recovery, Epstein–Barr and cytomegalovirus infection, GVHD, and relapse in patients undergoing haplo-PBSCT. Fifty patients with acute leukemia or myelodysplastic syndrome were randomly divided into an MSC group administered 1 × 10⁶ MSCs/kg 4 to 6 hours before infusion of peripheral stem cells and a control group without MSCs.

Results

Mean platelet engraftment time was significantly faster in the MSC compared with the control group (12.28 vs 13.29 days). The mean neutrophil engraftment time was comparable in both groups (10.76 ± 2.40 vs. 10.29 ± 1.72 days). Grade II or above acute GVHD was significantly decreased in the MSC compared with the control group (12% vs. 36%). There were no significant differences in relapse rate or overall survival between the groups.

Conclusion

These results suggest that pre-infusion single-dose MSCs promote platelet engraftment and decrease severe acute GVHD without increasing relapse rate.

Key Aspects of the Immunobiology of Haploidentical Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation from a haploidentical donor is increasingly used and has become a standard donor option for patients lacking an appropriately matched sibling or unrelated donor. Historically, prohibitive immunological barriers resulting from the high degree of HLA-mismatch included graft-vs.-host disease (GVHD) and graft failure. These were overcome with increasingly sophisticated strategies to manipulate the sensitive balance between donor and recipient immune cells. Three different approaches are currently in clinical use: (a) ex vivo T-cell depletion resulting in grafts with defined immune cell content (b) extensive immunosuppression with a T-cell replete graft consisting of G-CSF primed bone marrow and PBSC (GIAC) (c) T-cell replete grafts with post-transplant cyclophosphamide (PTCy). Intriguing studies have recently elucidated the immunologic mechanisms by which PTCy prevents GVHD. Each approach uniquely affects post-transplant immune reconstitution which is critical for the control of post-transplant infections and relapse. NK-cells play a key role in haplo-HCT since they do not mediate GVHD but can successfully mediate a graft-vs.-leukemia effect. This effect is in part regulated by KIR receptors that inhibit NK cell cytotoxic function when binding to the appropriate HLA-class I ligands. In the context of an HLA-class I mismatch in haplo-HCT, lack of inhibition can contribute to NK-cell alloreactivity leading to enhanced anti-leukemic effect. Emerging work reveals immune evasion phenomena such as copy-neutral loss of heterozygosity of the incompatible HLA alleles as one of the major mechanisms of relapse. Relapse and infectious complications remain the leading causes impacting overall survival and are central to scientific advances seeking to improve haplo-HCT. Given that haploidentical donors can typically be readily approached to collect additional stem- or immune cells for the recipient, haplo-HCT represents a unique platform for cell- and immune-based therapies aimed at further reducing relapse and infections. The rapid advancements in our understanding of the immunobiology of haplo-HCT are therefore poised to lead to iterative innovations resulting in further improvement of outcomes with this compelling transplant modality.