A registry-based, observational safety study of inotuzumab ozogamicin (InO) treatment in patients (pts) with B-cell precursor acute lymphoblastic leukemia (ALL) who proceeded to hematopoietic stem cell transplant (HSCT).

7017 Background: InO is a CD22-directed antibody-drug conjugate indicated for treatment of relapsed/refractory (R/R) ALL. InO has been associated with hepatotoxicity and hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), particularly post-HSCT. Registry data (Center for International Blood and Marrow Transplant Research [CIBMTR]) was analyzed to assess toxicity in pts with ALL who received InO prior to HSCT. Methods: CIBMTR patient data are being collected for a 5-year period after US approval of InO (Aug 2017 – Aug 2022). Data from US pts age ≥18 y treated with InO who proceeded to allogeneic HSCT were included. Using interim data at 3 y, we evaluated post-HSCT outcomes, including clinical status, overall survival, transplant-related (non-relapse) mortality (NRM), relapse, death after relapse (time from HSCT to death after the first 28 d from any cause with prior relapse/progression post-HSCT), and investigator-defined adverse events, including hepatic VOD/SOS. All statistical analyses are descriptive. Results: Data accrued from 18 Aug 2017 to 17 Aug 2020 for 131 adult pts (median age 40 y) who proceeded to first allogeneic HSCT: 31% in first complete remission (CR1), 46% in CR2, 13% in ≥CR3, 5% in 1st relapse, 2% in ≥3rd relapse, and 3% in primary induction failure. A majority (70%) had transplants from peripheral blood stem cells, and 47% involved an HLA-identical sibling or other related donor. Nearly half received myeloablative conditioning regimens. Before HSCT, 36% of pts received 1 cycle of InO, 46% had 2 cycles, and 17% had ≥3 cycles. Half (48%) received InO as a single agent. Median time from last dose of InO to HSCT was 2.0 mo (range: 0.4–26.2). At time of data-lock (11 Nov 2020), post-transplant data were available for 131 pts. Outcomes for these pts are shown in the Table. Among a subgroup of adults with active R/R ALL (n = 91) at time of HSCT (median of 4 lines prior therapy), VOD/SOS incidence within 100 d of HSCT was 18%. Conclusions: Incidence of VOD/SOS after first HSCT in InO-treated pts with R/R ALL in this study was similar to the 18–19% reported in pooled analyses of 2 clinical trials among InO-treated pts with R/R ALL (Marks et al, Biol Blood Marrow Transplant 2019) and in the INOVATE study (Kantarjian et al, Lancet Haematol 2017). The NRM at 1 y of 21% (23% R/R ALL) is lower than the NRM at 1 y of 38% reported in the pooled analyses of R/R ALL InO recipients.[Table: see text]

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A Phase I study of inotuzumab ozogamicin in pediatric relapsed/refractory acute lymphoblastic leukemia (ITCC-059 study)

Blood ◽

10.1182/blood.2020007848 ◽

2020 ◽

Author(s):

Erica Brivio ◽

Franco Locatelli ◽

Marta Lopez-Yurda ◽

Andrea Malone ◽

Cristina Diaz de Heredia ◽

...

Keyword(s):

Acute Lymphoblastic Leukemia ◽

Phase I ◽

Phase I Study ◽

Residual Disease ◽

Lymphoblastic Leukemia ◽

Sinusoidal Obstruction Syndrome ◽

Cell Transplant ◽

Antibody Drug Conjugate ◽

Inotuzumab Ozogamicin ◽

Hematopoietic Stem

This Phase I study investigated the recommended Phase II dose (RP2D) of inotuzumab ozogamicin (InO), a CD22-directed antibody-drug conjugate, in pediatric patients with multiple-relapsed/refractory (R/R) CD22-positive acute lymphoblastic leukemia (ALL). Patients (≥1-<18 years) received three InO doses (Days 1, 8, 15) per course. Dose-escalation was based on dose-limiting toxicities (DLT) during Course 1 . Dose level 1 (DL1)=1.4 mg/m2 (0.6-0.4-0.4 mg/m2); DL2=1.8 mg/m2 (0.8-0.5-0.5 mg/m2). Secondary endpoints included safety, anti-leukemic activity, and pharmacokinetics. Twenty-five patients (23 evaluable for DLT) were enrolled. In Course 1, first cohort, 1/6 (DL1) and 2/5 (DL2) patients experienced DLTs; subsequent review considered DL2 DLTs to be non-dose-limiting. Dose was de-escalated to DL1 while awaiting protocol amendment to re-evaluate DL2 in a second cohort, where 0/6 (DL1) and 1/6 (DL2) patients had a DLT. Twenty-three patients experienced Grade 3-4 adverse events; hepatic sinusoidal obstruction syndrome was reported in two patients after subsequent chemotherapy. Overall response rate after Course 1 was 80% [95% CI: 59-93%] (20/25 patients; DL1=75% [43-95%], DL2=85% [55-98%]); 84% [60-97%] of responders obtained minimal residual disease-negative CR; 12-month overall survival was 40% [95% CI: 25-66%]. Nine patients received hematopoietic stem cell transplant or chimeric-antigen receptor T-cells after InO. InO median maximum concentrations were comparable to simulated adult concentrations. InO was well tolerated, demonstrating anti-leukemic activity in heavily pre-treated children with CD22-positive R/R ALL. RP2D was established as 1.8 mg/m2/course, as in adults.

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Inotuzumab ozogamicin in pediatric patients with relapsed/refractory acute lymphoblastic leukemia (R/R ALL).

Journal of Clinical Oncology ◽

10.1200/jco.2017.35.15_suppl.10512 ◽

2017 ◽

Vol 35 (15_suppl) ◽

pp. 10512-10512 ◽

Cited By ~ 8

Author(s):

Deepa Bhojwani ◽

Richard Sposto ◽

Nirali Shah ◽

Vilmarie Rodriguez ◽

Maureen Megan O'Brien ◽

...

Keyword(s):

Pediatric Patients ◽

Lymphoblastic Leukemia ◽

Single Agent ◽

Sinusoidal Obstruction Syndrome ◽

Cell Transplant ◽

Inotuzumab Ozogamicin ◽

T Cell Therapy ◽

Hematopoietic Stem ◽

Heavily Pretreated ◽

Grade 3

10512 Background: Inotuzumab ozogamicin (InO), a CD22-targeting antibody linked to calicheamicin demonstrated exceptional activity in R/R ALL in adults. InO has been available to pediatric patients with R/R ALL via a compassionate access program. Methods: Participating international pediatric oncology centers received IRB approval to submit retrospective demographic, outcome and toxicity data on pediatric patients who received at least one dose of InO. Results: Thirty-four patients, age 2.3-21.4 yrs (median 11.7) received 1-4 cycles (3 weekly doses) of InO. Patients were heavily pretreated in 1st-5threlapse; 28 were refractory to their preceding regimen. Thirteen patients had prior hematopoietic stem cell transplant (HSCT), 27 received prior CD19 and 8 prior CD22-directed therapy. Pre-InO disease was M3 ( > 25% blasts) in 26 patients, M2 (5-25%) in 3, and MRD only in 5 (1 with extramedullary disease). Of 29 patients with M2/M3 disease at baseline, 18 (62%) achieved a complete remission (CR), 13 of whom were MRD negative. Post-InO, 15 patients proceeded to HSCT and 5 to CAR T-cell therapy. Alterations in CD22 expression at subsequent relapse were noted in two patients with available blasts samples. No deaths were attributed to InO during therapy. The incidence of grade 3/4 infections was 38% and were of the expected types. Grade 1-4 hepatic toxicity was noted in 11/34 (32%) patients, primarily asymptomatic elevations in transaminases/bilirubin. There was no sinusoidal obstruction syndrome (SOS) during InO therapy but 8/15 patients who received HSCT post-InO developed SOS. One patient died from SOS, but the others recovered. The incidence of SOS was higher in patients who had undergone prior HSCT (6/8) versus no prior HSCT (2/7). SIRS (1), neurotoxicity (2) and hemorrhage (3) were infrequent. Three patients had musculoskeletal pain associated with edema. Conclusions: Single agent InO had a CR rate of 62% in heavily pretreated pediatric patients. Toxicities were similar to adults with hepatic and infectious toxicity being the most common. Overall InO was well tolerated, but the incidence of SOS was high in patients who underwent HSCT post-InO, particularly in those who had undergone a prior HSCT.

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Multi-Agent Phase I Trials in Childhood Acute Lymphoblastic Leukemia (ALL).

Blood ◽

10.1182/blood.v108.11.4528.4528 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4528-4528

Author(s):

Richard Sposto ◽

Elizabeth A. Raetz ◽

Charles P. Reynolds ◽

Paul S. Gaynon

Keyword(s):

Phase I ◽

Phase I Trial ◽

Lymphoblastic Leukemia ◽

Single Agent ◽

Complete Response ◽

Maximum Tolerated Dose ◽

Cell Transplant ◽

Phase I Trials ◽

Hematopoietic Stem ◽

The Impact

Abstract Background: Single agent phase I trials with conventional methodology may not be suitable for children with relapsed leukemia. Accrual of children with ALL in relapse to single-agent phase I trials is poor due to clinical urgency and a > 30% likelihood of complete response (CR) with a variety conventional agents combinations (Br J Haematol.2005; 131(5): 579) with the option of hematopoietic stem cell transplant in remission. As most drugs are ultimately used in combination, a Phase I trial testing a new agent in combination with conventional agents would seem most useful and might increase accrual. However, with conventional phase I methodologies determination of a maximum tolerated dose is complicated by the toxicities of the accompanying conventional agents and by the background morbidity of relapsed leukemia. Methods: The Children’s Oncology Group (COG) study, AALL01P2, employed vincristine, prednisone, doxorubicin, and pegylated asparaginase for children with ALL in first marrow relapse. We determined the incidence of conventional non-hematologic dose limiting toxicities (DLT’s) and modeled the impact on a hypothetical phase I trial of a candidate agent with no additional toxicity. Results: Among 111 patients on AALL01P2, 19% had conventional non-hematologic DLT’s. Induction therapy was judged clinically acceptable. With a traditional Phase I escalation scheme that accepts 0/3 and 1/6 DLT’s at a dose-level and rejects 2/3 and 2/6 DLT’s, an agent that adds no morbidity would be rejected as too toxic at any dose 30% of the time. Conclusion: Background morbidity confounds identification of an acceptable dose of a non-toxic new agent tested in combination with conventional drugs for recurrent ALL. We propose a modification to the traditional Phase I design that increases the DLT thresholds to 1/3 and 2/6, which effectively compensates for background toxicity and reduces the chance of falsely rejecting an acceptable agent.

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Myeloablative Chemo-Conditioning for First Hematopoietic STEM CELL Transplantation in Children with ACUTE Lymphoblastic Leukemia in First or Second Remission

Blood ◽

10.1182/blood.v124.21.546.546 ◽

2014 ◽

Vol 124 (21) ◽

pp. 546-546 ◽

Cited By ~ 1

Author(s):

Christina Peters ◽

Jean-Hugues Dalle ◽

Stelios Graphakos ◽

Petr Sedlacek ◽

Antonio Campos ◽

...

Keyword(s):

Bone Marrow ◽

Stem Cell ◽

Lymphoblastic Leukemia ◽

Peripheral Blood Stem Cells ◽

Hematopoietic Stem ◽

Allogeneic Hsct ◽

Donor Type ◽

Blood Stem Cells

Abstract Christina Peters, Petr Sedlacek, Jean Hugues Dalle, Stelios Graphakos, Antonio Campos, Akif Yesilipek, Jacek Wachowiak, Arjan Lankester, Andrea Pession, Amir Ali Hamidieh, Marianne Ifversen, Jochen Büchner, Gergely Krivan, Franca Fagioli, Arnaud Dalissier; Myriam Labopin; Peter Bader on behalf of the EBMT Pediatric Diseases Working Party Most children with acute lymphoblastic leukemia (ALL) with indication for allogeneic hematopoietic stem cell transplantation (HSCT) receive myeloablative conditioning with a total body irradiation (TBI)-containing regimen. To investigate the outcomes of patients (pts) who did not undergo TBI, we performed a retrospective registry based study on children below 18 years who received a myeloablative chemo-conditioning for a first allogeneic HSCT from different donors between 2000 and 2012. In this analysis, only chemotherapeutic regimens with more than 30 applications were included. In total, 732 pts were included: 313 pts who received bone marrow (BM) or peripheral blood stem cells (PBSC) in 1st CR, 247 pts with BM/PBSC transplantation in CR2, 85 pts and 52 pts who received umbilical cord blood (CB) in 1st or 2nd CR, respectively. The most commonly applied myeloablative chemo-combinations were: Busulfan (Bu)/Cyclophosphamide (Cy) (n=202), Bu/Cy/Etoposide (VP) (n=189), Bu/Cy/Melphalan (Mel) (n=93), Bu/AraC/Mel (n=80), Bu/Fludarabine (Flu)/Thiotepa (Thio) (n=62), Bu/Cy/Thio (n=53, Bu/Cy/Thio (n=53), and Bu/Flu (n=53). 313 pts received either BM or PBSC in CR1 with a median follow up of 26 months (1-156) and we compared Bu/Cy/VP vs the other chemo-conditioning regimens. The Bu/Cy/VP cohort had a longer follow up (med 37 vs. 20 months, p=0.002), pts were younger (med 3,6 vs. 6,5 years, p=0.003) and the median year of transplant was earlier (med 2009 vs. 2010, p=0.03). Donor type, CMV match, gender match, stem cell were comparable. In univariate analysis, conditioning with Bu/Cy/VP was better than all other combinations: relapse incidence (RI) 21% vs 32% (p=0.05), leukemia-free survival (LFS) 72 vs 54% (p=0.004), overall survival (OS) 79 vs 68% (p=0.03) and chronic GVHD (cGVHD) 9% vs 19% (p=0.014). Engraftment and incidence and severity of acute GVHD were similar and non- relapse mortality (NRM) was 7% vs 13% (p=0.10). Other significant influencing factors were: interval between diagnosis and transplantation below or beyond 208 days (NRM 6% vs 16%, p=0.015), donor sibling vs other (RI 35% vs 23%, p=0.01, NRM 5% vs 16%, p=0.001) and in vivo T cell depletion (TCD) vs no TCD (RI 35% vs. 19%, p=0.003; NRM 20% vs 4%, p=0.0001). In the cox model, conditioning type (Bu/CY/VP vs other), age, year of transplantation, interval from diagnosis to transplant, donor type, stem cell source and in vivo TCD were evaluated. For LFS only BU/CY/VP was associated with better outcome (p=0.004, HR .52), RI was lower after Bu/Cy/VP (HR .54, p=0.02), NRM was higher in pts older than 4,6 years (p=0.02, HR 2,48) and after TCD HSCT (p=0.01, HR 9,13) and OS was best after Bu/Cy/VP (p=0.03, HR 0.57). We conclude that omission of TBI is feasible for children who undergo first allogeneic HSCT in first or second complete remission. The combination of busulfan, cyclophosphamide and etoposide resulted in better LFS and OS with less NRM and RI for children who received bone marrow or peripheral blood stem cells in CR1. These observations should be the basis for prospective trials in homogenous patient groups. Disclosures No relevant conflicts of interest to declare.

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Mucormycosis Leading to Cerebral Edema and Cerebellar Tonsillar Herniation after Allogeneic Bone Marrow Transplant: A Case Report

Case Reports in Infectious Diseases ◽

10.1155/2019/5138198 ◽

2019 ◽

Vol 2019 ◽

pp. 1-5

Author(s):

Chetan Jeurkar ◽

Lauren Margetich ◽

Ziver Sahin

Keyword(s):

Cerebral Edema ◽

Marrow Transplant ◽

Cell Transplant ◽

Allogeneic Bone ◽

Tonsillar Herniation ◽

Hematopoietic Stem ◽

Allogeneic Hsct ◽

Pulmonary Mucormycosis ◽

Increased Risk ◽

High Level

Introduction. Mucormycosis following hematopoietic stem cell transplant (HSCT) carries a very high mortality rate. Pulmonary mucormycosis often leads to systemic dissemination and eventual death. It is imperative for transplant providers to have a high level of suspicion for mucormycosis and initiate early treatment. Here, we present a 64-year-old woman who died of disseminated mucormycosis 13 days following her allogeneic HSCT. Case Presentation. A 64-year-old female with a history of acute myeloid leukemia (AML) presented for allogeneic HSCT and passed away from intracerebral hemorrhage secondary to mucormycosis infection 13 days following her transplant. On autopsy, it was found she had angioinvasive mucormycosis in her frontal lobe leading to cerebral edema which eventually led to tonsillar herniation and brainstem infarction. Her lungs were the likely source of infectious dissemination. Discussion. This case represents an unusual course of events following HSCT in that no other published case shows tonsillar herniation resulting from mucormycosis-related intracerebral swelling. We also report this case because it is believed mucormycosis in HSCT patients is underreported. Additionally, our case highlights the importance of increased vigilance for mucormycosis in patients with prolonged neutropenia prior to HSCT and the potential link of voriconazole prophylaxis and increased risk for mucormycosis.

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Marqibo® (vincristine sulfate liposomes injection; VSLI) In the Treatment of Adult Patients with Advanced, Relapsed/Refractory Acute Lymphoblastic Leukemia (ALL): A Combined Analysis of the VSLI-06 and RALLY Studies

Blood ◽

10.1182/blood.v116.21.2143.2143 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2143-2143

Author(s):

Susan O'Brien ◽

Deborah A Thomas ◽

Leonard T Heffner ◽

Wendy Stock ◽

Gerald L. Messerschmidt ◽

...

Keyword(s):

Salvage Therapy ◽

Response Rate ◽

Lymphoblastic Leukemia ◽

Single Agent ◽

Complete Response ◽

Adult Patients ◽

Cell Transplant ◽

Vincristine Sulfate ◽

Hematopoietic Stem ◽

To Receive

Abstract Abstract 2143 Background: The outcome of adults with relapsed/refractory ALL, and of those whose disease recurs after first salvage, in particular, is extremely poor. Second salvage therapy with single agents has historically produced a complete response (CR) in only 4% of patients. (O'Brien, S, et al. Cancer 2008; 113:3186-3191). Third salvage therapy has not been studied but would be expected to be even less effective. Conventional vincristine sulfate (VCR) is an effective anti-leukemia agent, widely used in the treatment of ALL as part of several intensive regimens. VCR is dosed at 1.4 mg/m2 with a 2 mg cap due to early onset of peripheral neuropathy. VSLI (Marqibo) is a nano-particle encapsulated formulation of VCR designed to facilitate dose intensification, improve duration of drug exposure, and enhance cancer and bone marrow drug delivery. Methods: Two distinct studies investigated VSLI in adult patients with advanced, relapsed/refractory ALL. Study VSLI-06 was a Phase 1/2, multi-center, 36 patient, dose-escalation study to determine safety, maximum tolerated dose, and anti-leukemia activity. Patients received VSLI intravenously (IV) weekly at doses of 1.5, 1.825, 2.0, 2.25 or 2.4 mg/m2 with no dose cap plus dexamethasone 40 mg on days 1–4 and 11–14 of each 4 week cycle. The RALLY Study was a Phase 2, multi-national, 65 patient study of single-agent VSLI (2.25 mg/m2 IV weekly without dose cap) in adults with ALL in second relapse or who had progressed following at least two prior lines of anti-leukemia therapy. All subjects had been previously treated with VCR, and all received at least one dose of VSLI. The median age in both studies was 32 years with a combined range of 19 to 83 years. Other than one subject in VSLI-06, all subjects were Philadelphia chromosome negative. Results: The combined overall response rate was 31% (31 of 101). The combined complete response (CR) rate including CR with incomplete platelet (CRp) or hematologic (CRi) recovery was 20% (20/101). This response rate was consistent across the studies (19.4% and 20%, respectively). Hematologic improvement (HI) was achieved in 4 patients (11%) in VSLI-06 and 9 (14%) in RALLY, thus reducing transfusions and hospital visits. Five patients were able to receive a post-VSLI hematopoietic stem cell transplant (HSCT) in VSLI-06, and 10 patients were able to receive a post-VSLI HSCT in RALLY. The table below summarizes key study characteristics. The most commonly reported safety events in the studies were similar and included constipation, neuropathy, fatigue, nausea, pyrexia, febrile neutropenia, and anemia. Conclusion: These two studies totaling 101 patients with similar populations of advanced relapsed/refractory ALL showed a combined 20% CR/CRp/CRi rate, dwarfing the rate in historical studies. This is particularly encouraging, given that 100% of subjects had received prior VCR and that historical control data were largely in a less heavily pre-treated population. Both VSLI alone and combined with pulse dexamethasone appear to be highly active. In total, 15% of combined study patients were able to “bridge” to HSCT. Use of VSLI in the frontline setting and in combination regimens should further improve ALL patient outcomes. Disclosures: Messerschmidt: Hana Biosciences, Inc.: Employment. Hagey: Hana Biosciences, Inc.: Employment. Deitcher: Hana Biosciences: Employment. Kantarjian: Hana Biosciences, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees.

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Empiric or Presumptive Anti-Aspergillus Treatments for Allogeneic Hematopoietic Stem Cell Transplant Recipients with Sustained Febrile Neutropenia.

Blood ◽

10.1182/blood.v108.11.5288.5288 ◽

2006 ◽

Vol 108 (11) ◽

pp. 5288-5288

Author(s):

Kumi Oshima ◽

Yoshinobu Kanda ◽

Yuki Asano-Mori ◽

Hiroyuki Sato ◽

Takuro Watabane ◽

...

Keyword(s):

Stem Cell ◽

Febrile Neutropenia ◽

Hematopoietic Stem Cell ◽

Controlled Trial ◽

Invasive Pulmonary Aspergillosis ◽

Cell Transplant ◽

Peripheral Blood Stem Cells ◽

Hematopoietic Stem ◽

Allogeneic Hsct ◽

Clinical Records

Abstract Background: Although the onset of invasive pulmonary aspergillosis (IPA) after allogeneic hematopoietic stem cell transplantation (HSCT) was bimodal, IPA early after HSCT has become less frequent, partly due to the shortening of neutropenic periods by the use of peripheral blood stem cells or colony-stimulating factors. Therefore, the validity of empiric anti-Aspergillus treatments based on sustained febrile neutropenia according to the IDSA guideline should be re-evaluated. Patients and Methods: We retrospectively reviewed the clinical records of 114 adult patients who underwent allogeneic HSCT between September 2002 and December 2005 in HEPA-filtered clean rooms at the University of Tokyo Hospital. Fluconazole at 200 mg/day was given as anti-Candida prophylaxis. In general, anti-Aspergillus agents were not started empirically, but presumptively started after the detection of positive Aspergillus antigen, positive beta-D-glucan, halo-sign on chest X-ray or CT-scan, and so on, associated with sustained febrile neutropenia. For the definition of early IPA, we employed proven or probable IPA according to the EORTC/MSG criteria that developed between the day of HSCT and seven days after engraftment. Results: All but two who experienced early death showed neutrophil engraftment at a median of 16.5 days after HSCT. Although 15 patients developed IPA after HSCT, early IPA was observed only in 2 (1.8 %) patients. Among 73 patients who experienced sustained febrile neutropenia for more than 7 days before engraftment, we empirically started anti-Aspergillus agents in 13 patients a median of 9 days after the development of febrile neutropenia, whereas fluconazole was continued in 60 patients who had febrile neutropenia for 15 days in median. Four of the 60 patients received presumptive anti-Aspergillus therapy, one of whom developed probable IPA after the initiation of treatment. There was another patient who received anti-Aspergillus treatment only after the development of probable IPA because he showed no prior signs for presumptive therapy. There was no difference in the incidence of early IPA between patients who received empiric anti-Aspergillus therapy and those who did not (0% vs. 3.3%, P>0.99). The two patients who developed early probable IPA were successfully treated with anti-Aspergillus agents. Conclusions: These findings throw doubt on the validity of empiric anti-Aspergillus treatments for allogeneic HSCT recipients with sustained febrile neutropenia, provided that they are treated in clean units with anti-Candida prophylaxis. A randomized controlled trial is warranted to compare empiric and presumptive anti-Aspergillus treatments for allogeneic HSCT recipients with sustained febrile neutropenia.

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Defibrotide Inhibits Endothelial Cell Injury Induced By Plasmas of Patients with Thrombotic Microangiopathies

Blood ◽

10.1182/blood-2019-124158 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3676-3676

Author(s):

Jeffrey Laurence ◽

Sonia Elhadad

Keyword(s):

Endothelial Cell ◽

Cancer Chemotherapy ◽

Inflammatory Cytokine ◽

Marrow Transplant ◽

Caspase 8 ◽

Cell Transplant ◽

Thrombotic Microangiopathies ◽

Hematopoietic Stem ◽

Allogeneic Hsct

Introduction: Defibrotide is a polydisperse mixture of predominantly single-stranded polydeoxyribonucleotide sodium salts derived from porcine intestinal mucosa. It is currently the only therapy FDA-approved to treat hematopoietic stem cell transplant (HSCT)-associated hepatic veno-occlusive disease (VOD) with multi-organ dysfunction. Its mechanisms of action are complex and incompletely understood. In vitro, defibrotide can: promote endothelial cell (EC) mitogenesis via interaction with basic fibroblast growth factor; inhibit platelet adhesion and aggregation; reduce calcineurin inhibitor-induced EC apoptosis; and block pro-inflammatory cytokine activity, in the absence of anticoagulant effects (Blood Adv 2018;2:1495-1509). Given the critical role of EC injury with impaired regulation of thrombo-fibrinolytic pathways in both transplant-associated VOD and thrombotic microangiopathies (TMA), defibrotide has been used off-label to treat TMAs post-allogeneic HSCT. Significant clinical responses occurred in the majority of cases not complicated by renal failure (Bone Marrow Transplant 2019;54:142-145). It is known that conditioning regimens for autologous HSCT involve activation of pro-inflammatory pathways in EC which can be blocked by defibrotide (Biol Blood Marrow Transplant 2011;17:497-506). We sought to determine whether clinically relevant concentrations of defibrotide could block activation of caspase 8 in EC, an early step in apoptotic injury, as induced by plasmas from patients with TMAs secondary to thrombotic thrombocytopenic purpura (TTP), cancer/chemotherapy, and allogeneic HSCT. Methods: We utilized plasmas from individuals with acute TMAs: 13 with TTP; 5 with an atypical hemolytic-uremic syndrome (HUS)-type of TMA in the setting of cancer chemotherapy, persisting after withdrawal of chemotherapy; and 10 with TMAs following alloHSCT, persisting after withdrawal of GvHD prophylaxis. The in vitro model system was previously published by our lab, documenting the ability of plasmas from acute TTP patients to activate caspase 8 in EC, followed by apoptotic EC death (Blood 2008;112:340-349). This effect was dependent on plasma-based proinflammatory cytokines capable of down-regulating EC cytoprotective factors. Briefly, 5 x 105 primary human neonatal microvascular endothelial cells of dermal origin were plated in 1ml culture medium/well of 12 well polystyrene plates (3.6cm2/well) pre-coated with 1% fibronectin. 2% (v/v) patient or control plasma was added, alone or with varying concentrations of defibrotide (0.5-10μg/ml), for 3hrs at 37ºC. Cells were then harvested and a commercial colorimetric kit (Millipore) was used to assess caspase 8 enzyme activity. Results: Initial dose-response curves showed a plateau effect for defibrotide-mediated inhibition of caspase 8 activation at 5μg/ml; subsequent experiments utilized that dose. To control for the possibility of direct inhibition of caspase 8 by defibrotide, we found that caspase 8 activity initiated by staurosporine (1μM) was unaffected by defibrotide (Fig.) >50% inhibition of caspase 8 was seen for 3/5 cancer/chemotherapy-linked TMA patient plasmas, 7/13 TTP plasmas, and 0/10 TA-TMA plasmas. >20% suppression of such activation was seen for 5/5 cancer/chemotherapy TMA plasmas, 12/13 TTP plasmas, and 4/10 TA-TMA plasmas. Representative examples are shown in the Fig., including defibrotide blocking caspase 8 activity induced by plasmas from a patient with cancer/chemotherapy linked TMA (patient 18) or TTP (patient 41), but not from another TTP patient (patient 17). Conclusions: Interventions with high degrees of therapeutic success are available for TMAs related to TTP and primary aHUS. However, TMAs complicate 20% of alloHSCT, and though half may resolve when GvHD immunoprophylaxis is discontinued, three year survival rates for those in whom the TMA persists are as low as 11%. Based on multiple case reports, defibrotide may represent an important resource in those cases, and in other TMAs refractory to conventional treatment. Further studies are required to see if defibrotide-mediated blockade of plasma-induced EC activation and injury which we demonstrate in vitro correlates with in vivo responses, and if the mechanism involves suppression of pro-inflammatory cytokine-mediated cell activation. Disclosures No relevant conflicts of interest to declare.

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