Why Are Patients Not Getting a Graft? An Intent-to-Transplant Analysis in the Times of Universal Coverage and Haploidentical Donors

Introduction: Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a potentially curative option for patients with hematologic diseases. When considered candidates, patients face barriers to receive a transplant. Therefore, we aimed to analyze factors that limit or favor access to an alloHSCT in a population that has been HLA typed and therefore with a potential intent-to-transplant. Method(s): We retrospectively reviewed records from 2015 until the start of the COVID19 pandemic in two Mexican government- funded transplant centers and one private that have in-house HLA typing;in two of them, an outpatient transplant strategy is followed for most patients. HLA-typed patients who were potentially eligible for transplantation were included and their outcomes were assessed in an intent-to-transplant basis. We compared the outcomes of patients who underwent transplantation to those who did not and evaluated contributing barriers to access alloHSCT with multivariate logistic regression. Result(s): A total of n=374 patients were analyzed. The median age at HLA-typing was 35 years (IQR 23-47);59.3% had acute(Table Presented) leukemia, 17.4% bone marrow failure or myelodysplastic neoplasms, 13.1% lymphoma, 8% myeloproliferative neoplasms, 1.1% chronic lymphocytic leukemia and 1.1% multiple myeloma. Most patients (55.9%) had government insurance coverage. Median time from diagnosis to HLA-typing was 8 months (IQR 3-19). The majority had a potential donor (94.4%): 56.4% haploidentical, 37.4% a matched sibling donor and 0.5% an unrelated donor. Almost half of them received a transplant (n=185, 49.5%), the median time from HLA-typing to alloHSCT was 2 months (IQR 1-5.5). Disease activity or progression was the biggest barrier for transplantation;Table 1. Donor availability limited transplant access for 12.1% of patients. Access to transplantation was favored by private/out-of-pocket payment (OR 2.1 95% CI 1.3-3.4), and receiving care in the outpatient center (OR 6.4 95% CI 4-10.0), while HLA matching was not (OR 1.2 95% CI 0.8-1.8). Non-relapse mortality in alloHSCT was 21%. Median overall survival (OS) from the intent-to-transplant cohort was 16 months (CI 95% 12.4-19.6). An OS landmark analysis for patients alive at or beyond 2 months (the median time from HLA-typing to alloHSCT) showed prolonged survival in alloHSCT (30 vs 12 months, p <.001), Figure 1. By the time of the analysis 159 patients (42.5%) were still alive and 115 (30.7%) were event-free.(Figure Presented)Conclusion: The most frequent barrier to transplantation was the disease itself, followed by the transplant waitlist and comorbidities. Access to resources and an outpatient strategy or "center effect" favored alloHSCT. In the era of haploidentical transplantation, donor availability was a smaller issue. Efforts to improve timely referrals and access to effective pre-transplant therapies should be undertaken.Copyright © 2023 American Society for Transplantation and Cellular Therapy

Anaphylaxis to Cyclophosphamide Metabolites during Lymphodepletion for CAR-T Therapy

Background: Cyclophosphamide (Cy) is used in hematopoietic stem cell transplant (HSCT) preparative regimens and lymphodepletion for chimeric antigen receptor T-cell (CAR-T) therapy. We describe a case of cyclophosphamide hypersensitivity in a pediatric patient during CAR-T therapy. Case description: A 13 year old boy was diagnosed with very high risk ALL in 2015 and had 2 isolated CNS relapses treated with intensified chemotherapy (chemo) and cranial radiation (1st relapse) and Blinatumomab with intrathecal (IT) chemo followed by sibling donor HSCT (2nd relapse). At age 19, and 18 months after HSCT, he had a 3rd CNS relapse treated with IT chemo and referral for CAR-T therapy. At our center, leukapheresis and CAR-T production (Novartis) were performed. Later, during lymphodepletion with fludarabine (Flu) and Cy, physiologic replacement hydrocortisone (HC) was briefly held to prevent interference with CAR-T function. After 3 days of Flu/Cy, he developed fever and hypotension requiring inotropic support. Hypotension and fever resolved with stress dose HC and antibiotics and was attributed to culture-negative sepsis and adrenal crisis. CAR-T infusion was subsequently delayed by skin GVHD requiring glucocorticoids and COVID-19 infection treated with convalescent plasma and nirmatrelvir/ritonavir. Physiologic HC replacement was continued when he was re-admitted for CAR-T therapy, but he again developed fever, diffuse erythema and shock in hours following the first dose of Cy necessitating stress dose HC, antibiotics, inotropes, and mechanical ventilation. Negative blood cultures and ongoing physiologic HC replacement suggested an alternative explanation for shock. Case reports of anaphylaxis to Cy metabolites implicated Cy as the causative agent so it was discontinued. After recovery, CAR-T cells were infused without complications. In the following weeks, he had no evidence of recurrent leukemia but was persistently pancytopenic. A sibling donor stem cell boost was proposed but the patient accepted only palliative care. He had several opportunistic infections before succumbing to E. coli sepsis. Discussion(s): The first episode of shock was initially attributed to adrenal crisis and sepsis, although no organism was identified. The second episode appeared anaphylactic in timing and clinical presentation with adequate HC replacement and negative cultures, suggesting Type I hypersensitivity. The patient previously received Cy uneventfully before HSCT, suggesting that the donor-derived immune system was the source of new Cy hypersensitivity. Onset of anaphylaxis within hours rather than minutes after Cy administration supports hypersensitivity to Cy metabolites rather than to the drug itself. This case highlights the importance of consideration of sensitivity to Cy metabolites as well as acquired donor-specific allergy even when alternative explanations are likely.Copyright © 2023 American Society for Transplantation and Cellular Therapy

OUTCOME OF ADULT HEMATOPOIETIC TRANSPLANT RECIPIENTS AFTER ADMISSION TO INTENSIVE CARE UNIT (ICU): SINGLE CENTRE EXPERIENCE

Background: Intensive care unit (ICU) admission during hematopoietic stem cell transplant (HSCT) is associated with poor prognosis1,2. Published series report a range of ICU admission rates from 24-40% of transplant patients, most frequent reasons involving septic shock, respiratory failure and veno-occlusive disease3. In addition, patients undergoing HSCT are at a high risk of severe morbidity and mortality associated with COVID-194. Aims: The aim of this study was to analyze outcome of HSCT patients requiring ICU admission in our center. Methods: We retrospectively analysed outcome of 752 patients who underwent HSCT in our centre from January/2008 to June/2021. Data were collected from patients' clinical histories. Results: 103 (14%) patients required ICU admission (baseline and HSCT characteristics on table). Median time to ICU admission was 42 days (-2-1765). Seven of these patients were admitted to ICU on two occasions giving a total of 110 consecutive ICU admissions available for analysis. Main reason for ICU admission was respiratory distress (74;67%), mainly due to pneumonia (53%) including a 3% caused by COVID19, pulmonary edema (26%) and pulmonary haemorrhage (8%). Septic shock was second most common cause for ICU admission (26;24%) due to gram-negative bacilli (47%), fungal (15%) gram-positive bacteria (13%), virus (10%) and others/idiopathic (16%). Other less frequent causes were veno-occlusive disease (11;10%), hepatic failure/encephalopathy (8;7%), haemorrhagic complications (6;5%), cardiorespiratory arrest (2%), GVHD (2%), cardiogenic shock (2%). Of the 110 ICU admissions, 37 (34%) required hemofiltration, of which 30 (81%) died;and 77 (70%) required orotracheal intubation, of which 59 (77%) died. During the 110 ICU admissions, 67 patients (61%) died in the ICU;of these, 40 (37%) received unrelated donor HSCT, 36 (33%) sibling donor, 16 (15%) haploidentical and 17 (16%) autologous. Median ICU length of stay of these patients was 13 days (range 1-76). The cause of death was the same reason for ICU admission. Eighteen (16%) patients were discharged from ICU and died prior to Hospital discharge and 24 (22%) survived to Hospital discharge and were classified as post-discharge survivors. Of these 24 cases, 19 (79%) remain alive while the others (5;21%) succumbed to underlying disease or complications post-HSCT. Off note, both patients with COVID19 pneumonia (haploidentical and autologous HSCT respectively) were discharged from ICU and remain alive to date, without major complications. Summary/Conclusion: In our study 14% of transplant recipients required ICU admission, slightly lower than previous reports. Most common cause of admission was respiratory failure, consistent with reported. Mortality rate during ICU admission was 61%;higher death rate observed in allogeneic transplantation and those requiring aggressive ICU treatments such as mechanical ventilation or hemofiltration. Although patients with COVID19 pneumoniae who require ICU admission are usually associated with adverse outcome, in our series they responded successfully to intensive treatment. ICU admission following HSCT is associated with poor prognosis, but should not be considered futile. (Table Presented).

TRANSPLANT-ASSOCIATED THROMBOTIC MICROANGIOPATHY SUCCESSFULLY TREATED WITH RAVULIZUMAB

Background: Transplant-associated thrombotic microangiopathy (TA-TMA) is an increasingly recognized complication of hematopoietic stem cell therapy (HSCT) with incidence rates ranging from 10-35%. The predominant mechanism leading to TA-TMA is endothelial cell damage leading to complement dysregulation and microvascular hemolysis. Complement dysregulation is particularly important in the pathophysiology of TA-TMA as initial trials have shown response to complement blockade using eculizumab, a humanized monoclonal antibody targeting the terminal complement pathway. Ravulizumab is a longer acting monoclonal antibody with the same target as eculizumab that is increasingly used for treatment of atypical hemolytic uremic syndrome. Herein, we describe the case of an African American female with relapsed/refractory infantile B-cell acute lymphoblastic leukemia (B-ALL) who underwent 10/10 HLA-matched sibling donor allogeneic transplant (conditioning: busulfan/fludarabine/thiotepa;GVHD prophylaxis: tacrolimus/methotrexate) who developed TA-TMA marked by pericardial effusion, elevated LDH, proteinuria, hypertension, thrombocytopenia, anemia, and evidence of microangiopathy. Upon diagnosis, as ravulizumab was on formulary and readily available unlike eculizumab, she was treated with ravulizumab instead of eculizumab. Objectives: To describe the therapeutic response to ravulizumab in one patient diagnosed with TA-TMA. Design/Method: A retrospective chart review was performed regarding this patient's ravulizumab treatment course, and direct discussions were had with the patient's care team. Results: Ravulizumab (loading dose of 600 mg followed 2 weeks later by maintenance dosing of 600 mg every 4 weeks) was administered. Pre-treatment CH50 was >75 U/mL (range: 30-75 U/mL) with sC5b9 and C3 complement levels at the upper limit of normal at 220 ng/mL (range: ≤244 ng/mL) and 143 mg/dL (range: 72-164 mg/dL), respectively. Clinical normalization of the patient's TA-TMA was achieved two weeks after loading dose administration with normalization of LDH and blood pressure values, improved proteinuria, decreased transfusion requirements, absence of schistocytes on peripheral smear, and complete resolution of pericardial effusion. A total of 5 maintenance doses of ravulizumab were administered approximately every 4 weeks with CH50 ranging <3-33 U/mL during this time period. Five maintenance doses were administered as the optimal duration was unknown and the patient's TA-TMA treatment course was complicated by COVID-19 infection, for which there was concern could lead to TA-TMA reactivation (which did not occur). The ravulizumab was well tolerated throughout with amoxicillin used for meningococcal prophylaxis. Conclusion: While studies evaluating ravulizumab for treatment of TA-TMA are ongoing, ravulizumab successfully led to complement blockade and clinical improvement in this patient with TA-TMA.

A prospective phase 2 study testing high dose post-transplant cyclophosphamide as sole GHVD prophylaxis after matched allotransplant using baltimore-based reducedintensity conditioning regimens and PBSC as source of graft

Introduction: The use of high-dose post-transplant cyclophosphamide (PTCY) has revolutionized graft-versus-host disease (GVHD) prophylaxis and allowed to successfully reconsider haplotransplant in recent years. As this strategy significantly reduces the incidence of both acute and chronic GVHD, PTCY has been thereafter considered not only in matched settings but also as sole GVHD prophylaxis, at least when considering myeloablative allotransplant using matched sibling (MSD) or unrelated (MUD) donors and bone marrow as source of graft. Here, PTCY, as a sole GVHD prophylaxis, was tested in a reduced-intensity conditioning (RIC) setting, using peripheral blood stem cells (PBSC) as source of graft considering that this platform is currently broadly used worldwide in adults. Methods: This prospective monocentric phase 2 study was designed with the main objective to demonstrate the feasibility and safety of using only PTCY (without cyclosporine A nor mycophenolate mofetyl after transplant) in adults (18-70 years old) eligible for a RIC PBSC transplant with MSD or MUD. The Baltimore platform with 2 days of PTCY 50mg/kg/day on days 3 and 4 post infusion was considered as conditioning regimen, using fludarabine for lymphoid disease or clofarabine for myeloid disease. The primary objective was to appreciate the incidence of corticosteroid-resistant acute grade 3-4 GVHD (CR 3-4 GVHD) within 100 days post-transplant. According to statistical rules, patients have to be included in a step by step fashion (3, 3, 6, 15, 15 and 17 patients) for a total of 59 evaluable patients (meaning having received PTCY), in order to stop the protocol soon enough in case of excessive rate of deleterious severe acute GVHD (graded according to Mount Sinai International Consortium). Thus, the trial had to be stopped in case of documentation of > 2 CR 3-4 GVHD for the first 3 patients, >3 CR 3-4 GVHD for the first 6 patients, > 4 CR 3-4 GVHD for the first 12 patients, > 6 3-4 CR GVHD for the first 27 patients, > 8 CR 3-4 GVHD for the first 42 patients and finally as soon as > 9 CR 3-4 GVHD for the last included patients. All patients gave informed consent. The trial was registered at ClinicalTrials.gov Identifier: NCT03263767. Results: The results of the first 27 first patients (males n=17 and female n=10;median age: 59 years old (yo), range: 26-70) are reported here. They were included between February 2018 and November 2020. Diagnoses were AML (N=8), MDS (N=5), CMML (N=2), myelofibrosis (N=5), CML (N=1), DLBCL (N=1), T-cell lymphoma (N=1), Philadelphia positive B-ALL (N=1), CLL (N=1), lymphoblastic lymphoma (N=1) and mixed phenotype acute leukemia (N=1). Donors were MSD in 10 cases and MUD in 17. Only one primary graft failure was documented in a 61 yo MDS patient with active disease at transplant. He is however still alive in response after autologous reconstitution. With a median follow-up of 17.6 months (range: 10-42) for alive patients at the time of analysis (July 2021), 1-year and 2-year survivals were 80.9+7% and 74.7+9%, respectively, for both OS et DFS. GVHD-free/relapse-free survival (GRFS) at 1-year and 2-year was 58.7+9% and 52.2+10%, respectively. Three relapses (11%) and 6 deaths occurred. Deaths were due to acute GVHD in 4 patients (including 1 with sepsis and 1 with SARS-COVID 19 infection) and relapse in 2. Grade 2, 3 and 4 acute GVHD occurred in 11, 1 and 4 patients, respectively, for a total of 59% of grade 2-4 acute GVHD. CR 3-4 GVHD was observed in all of 5 patients with acute grade 3-4 GVHD and 4 died related to GVHD. Moderate/severe chronic GVHD occurred in 5/22 (22.7%) evaluable patients, including 4 still on immunosuppressive therapy at 40, 28, 25 and 16 months post-transplant. Overall non-relapse mortality (NRM) was 14.8% and related to acute GVHD. However, the number of cases conducting to stop the protocol was not reached. Conclusion: PTCY as a sole GVHD prophylaxis is here demonstrated as possible and relatively safe for adults receiving a matched PBSC Baltimore-based RIC allograft. The very good survivals reported he e may be related to a strong GVL effect associated with the high incidence of acute GVHD. However, because of this high incidence and the fact that NRM was related to GVHD after this first analysis, we have now made an amendment to test the addition to PTCY of one day of anti-thymoglobulin (ATG) 2.5 mg/kg on day-2 for the next 32 patients to be included. This second cohort receiving PTCY+ATG as a sole prophylaxis is ongoing.

Successful tolerance induction by combined kidney and hematopoietic stem cell transplantation

Background: Induction of immunological tolerance has been the holy grail of transplantation immunology for decades. The only successful approach in the clinical situation has been a combined kidney and hemato-poietic stem cell transplantation from the same living donor. Here, we report the first three patients included in this first European trial to induce tolerance by mixed lymphohematopoietic chimerism. Methods: The protocol followed previous studies at Stanford University: kidney transplantation was performed on day 0 including induction with anti-thymocyte globulin followed by conditioning with 10x1.2 Gy total lymphoid irradiation and the transfusion of CD34+ stem cells together with a body weight-adjusted dose of donor T cells. Immunosuppression consisted of cyclosporin and steroids for 10 days, cyclosporin and mycofenolate mofetil for 1 month, and then cyclosporin monotherapy with tapering over 9-20 months. Results: Two female and one male patients were transplanted with a kidney and peripherally mobilized hematopoietic stem cells from their HLA-identical sibling donor. No rejection or graft-versus-host disease occurred in these patients, which are currently off immunosuppression since 31, 18 and 6 months. Chimerism was stable in the first, but slowly declining in the other two patients. A molecular microscope analysis in patient 2 revealed the genetic profile of a normal kidney. No relevant infections were observed, and the quality of life in all three patients is excellent. During the SARS-CoV2 pandemic, all three patients were vaccinated with the mRNA vaccine, and they showed excellent humoral and cellular SARS-CoV2-specific immunity. Conclusions: Combined kidney and hematopoietic stem cell transplantation is a feasible and successful approach to induce specific immuno-logical tolerance in the setting of HLA-matched living kidney donation while maintaining immune responsiveness to a viral vaccine.

Acquired Aplastic Anemia in Immunocompetent Pediatric Patients with Asymptomatic COVID-19 Infection: A Case Series

Background: In pediatrics, acquired aplastic anemia (AA) is most commonly due to infection, particularly viruses, when a cause can be identified. Coronavirus disease 2019 (COVID-19) has affected more than 197 million people worldwide, and children typically experience a less severe disease course. COVID-19 is known to cause transient hematologic abnormalities, including leukopenia, lymphopenia, anemia and thrombocytosis or thrombocytopenia in severe cases. Objectives: Describe three cases of COVID-19 associated acquired aplastic anemia in immunocompetent pediatric patients. Design/Methods: Case series established by retrospective review of the electronic medical record. Results: Case 1: An 8-year-old Hispanic male presented with a three-week history of increased bruising and a one-week history of progressive exercise intolerance, shortness of breath, pallor and fatigue. Labs showed pancytopenia. Bone marrow aspirate and biopsy was markedly hypocellular at 5-10% consistent with aplastic anemia (Figure 1). Work-up for the etiology of his aplastic anemia was only significant for positive SARS-COV-2 antibodies and a SEC23B variant of unknown significance on a comprehensive bone marrow failure (BMF)/myelodysplastic syndrome (MDS)/leukemia panel from the Children's Hospital of Philadelphia (CHOP). He was treated with eltrombopag olamine and then proceeded to immunotherapy with cyclosporine (CsA) and horse antithymocyte globulin (ATG) when a sibling match was not identified for hematopoietic stem cell transplant (HSCT). Three months later, his peripheral blood counts have improved, and he is no longer transfusion-dependent. Repeat bone marrow aspirate and biopsy continues to show markedly hypocellularity at <5%. Case 2: A 5-year-old non-Hispanic white female presented with a two-week history of easy bruising, petechial rash, fatigue and bone pain. Labs showed pancytopenia, and bone marrow aspirate and biopsy showed marked hypocellularity at 5-10% consistent with aplastic anemia (Figure 2). Her aplastic anemia work-up was significant for positive SARS-COV-2 antibodies and subclinical RBC and WBC paroxysmal nocturnal hemoglobinuria (PNH) clones. She was started on eltrombopag olamine and then proceeded to immunotherapy with CsA and ATG when a matched sibling donor was not identified. Three months later, she continues to be severely neutropenic, anemic and thrombocytopenic requiring multiple transfusions. Repeat bone marrow aspirate and biopsy showed variable cellularity with some areas 10-20% and others 70% with an overall cellularity of 50%. Case 3: An 8-year-old non-Hispanic white female presented with a 10-day history of fatigue, bilateral leg pain and pallor. Labs showed pancytopenia, elevated inflammatory markers and elevated hemoglobin F. Bone marrow aspirate and biopsy demonstrated mild-moderate hypocellularity at 40-50%, left-shifted myelopoiesis and dyspoiesis in the erythroid and megakaryocytic cell lines (Figure 3). MDS and acute lymphoblastic leukemia (ALL) fluorescence in situ hybridization (FISH) panels were negative. Additional work-up revealed positive SARS-COV-2 antibodies. Her pancytopenia resolved within two weeks of her initial hospitalization. Four months later, she presented with increased bruising and fatigue. Labs showed leukocytosis, thrombocytopenia, anemia and circulating peripheral blasts. Bone marrow aspirate and biopsy was consistent with B-cell ALL. She is receiving chemotherapy on study COG AALL1732. Conclusion: Severe aplastic anemia (SAA) has high morbidity and mortality, and timely diagnosis is needed for appropriate treatment. Multiple different viral infections have been known to cause acquired aplastic anemia. Data on all the sequelae of COVID-19 infection is still emerging, but it is plausible that COVID-19 infection may cause SAA. All three patients were found to have positive COVID-19 antibodies but did not have any evidence of previous COVID-19 infection. Further research and follow-up is needed to determine if previous COVID-19 infection is indeed a risk factor for development of S A. [Formula presented] Disclosures: No relevant conflicts of interest to declare.

Implementation of a High-Dose Cytarabine Outpatient Program for Acute Myeloid Leukemia Patients in a Limited-Source Setting

Background: The management of acute myeloid leukemia (AML) patients usually requires long inpatient treatments that can affect the limited care facilities, the quality of life, and increases healthcare costs. Additionally, leukemia treating centers in developing countries face limited sources to deliver high-dose chemotherapies as inpatient treatments. Therefore, several reports have established the feasibility and safety of outpatient consolidation. We aimed to implement a high-dose cytarabine outpatient program for AML in a limited-source institution at a public center in Peru.Methods: We conducted a prospective pilot study starting in January 2019 and ending before the COVID-19 Pandemic in March 2020. Eligible patients were ≥ age 14, met inclusion criteria for inpatient induction regimens, were without active infection, and had the following: normal chest x-ray and biochemistry, complete remission after one cycle of 7+3 induction. Logistical requirements included a 3-hours distance residence near the treatment center, caregiver support, trained nursing staff, infusion room capacity, and participation in follow-up. Patients received prophylactic antimicrobials such as oral levofloxacin, fluconazole, and acyclovir and were admitted to the hospital for predetermined complications of therapy (fever, G3-4 toxicity, febrile neutropenia, bleeding or refractory thrombocytopenia). Risk stratification was based on conventional cytogenetics and multiplex PCR using Leukemia.net criteria. Results: Forty-two patients were included during the study period. The median age was 38 years (16-63) and Female/Male ratio 4:3. According to Leukemia.net, 24% were classified as high, 50% intermediate and 26% as low risk group. Including FLT3 mutations in 26% of cases. Twenty-two and 20 subjects received 1-2 and 3-4 cycles of ambulatory HiDAC, respectively. About one-third of cases had emergency admissions during consolidation and 74% complete at least 3 cycles of cytarabine. Only 4 patients underwent sibling-donor allo-SCT. Sixty-four percent experienced relapses, and at 2 years follow-up only 21 subjects were alive. Median OS was 15 months, a better survival was shown among patients who received 3-4 cycles of ambulatory HiDAC (2-year OS 18 vs 23%, p=0.031). Conclusion: Our pilot study shows the feasibility to deliver HiDAC as outpatient consolidation in selected AML cases in a limited setting. Additionally, a high rate of relapses and poor survival was noted in our cohort that requires further consideration. Disclosures: No relevant conflicts of interest to declare.