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Chronic graft-versus-host disease (cGVHD) is a complication of allogeneic hematopoietic cell transplantation (allo-HCT) and is the main cause of late non-relapse mortality (NRM). Three new agents are now approved to treat cGVHD, of which belumosudil has a unique and dual mechanism of action of i) targeting the Rho-GTPase-associated coiled-coil kinase 2 (ROCK2) in T helper follicular cells (TFH) and TH17 cells, this results in downregulation of proinflammatory cytokines (interleukin -21 and 17), the former in a STAT3-dependent mechanism, ii) inhibition of tissue fibrosis by targeting stress-induced polymerization of G-actin fibrils by inhibiting the Rho-ROCK-MRTF pathway.In this review we describe the epidemiology of cGVHD, its cardinal symptoms, preventive and therapeutic options, including second-line approved therapies in the United States (US). Clinical trial data that led to approval of belumosudil is discussed, in addition to the clinical scenarios in which the approved drugs may be most applicable.Belumosudil is approved for treatment of adult and pediatric patients ≥ 12 years with cGVHD after failing two lines of therapy based on results of the ROCKstar study that showed high overall response rates (ORR), favorable adverse effect profiles, and low rates of severe infections. With the availability of three new agents for treatment of cGVHD, treating physicians have more therapeutic options for patients and have additional options of development new clinical trials using a combination of recently approved drugs.

Purpose:A phase I/II study evaluating the safety and activity of memory-enriched CD19-directed chimeric antigen receptor (CD19-CAR) T cells in adults with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL).Patients and Methods:In phase I, we tested sequentially two cell populations for CAR transduction: (i) central memory (Tcm) or (ii) naïve, stem, and central memory (Tn/mem) T cells. The study employed an activity constrained for toxicity design to determine the recommended phase II dose (RP2D), which was tested in phase II.Results:The Tcm cohort was closed early due to lack of activity. The 200 ×106 Tn/mem-derived CD19-CAR T-cell dose was found to be safe and active, and was declared the RP2D. At RP2D, 58 participants underwent leukapheresis and 46 received CD19-CAR T cells. Median age for treated participants was 38 years (range, 22–72). Twenty-nine (63%) participants had relapsed post-allogeneic hematopoietic cell transplantation (alloHCT), 18 (39%) had Philadelphia-like (Ph-like) genotype, and 16 (35%) had extramedullary disease (EMD) at lymphodepletion (LD). Three (7%) participants had grade 3 cytokine release syndrome (CRS), and none had grade ≥ 4 CRS. Eight (17%) participants had grade ≥ 3 neurotoxicity, including one fatal cerebral edema. Forty (87%) patients achieved complete remission (CR)/CR with incomplete hematologic recovery, 2 (4%) progressed, and 4 (9%) were unevaluable for response. Among 42 response-evaluable participants, 16/17 with Ph-like ALL and 13/15 with EMD at LD responded. Twenty-one (53%) responders underwent alloHCT consolidation, which was associated with improved relapse-free survival (adjusted HR = 0.16; 95% confidence interval, 0.05–0.48; P = 0.001).Conclusions:Tn/mem-derived CD19-CAR T cells were safe and active, including in Ph-like ALL and EMD.See related commentary by El Marabti and Abdel-Wahab, p. 694

Toxicity management algorithms

Extramedullary disease at time of lymphodepletion

Purpose:A phase I/II study evaluating the safety and activity of memory-enriched CD19-directed chimeric antigen receptor (CD19-CAR) T cells in adults with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL).Patients and Methods:In phase I, we tested sequentially two cell populations for CAR transduction: (i) central memory (Tcm) or (ii) naïve, stem, and central memory (Tn/mem) T cells. The study employed an activity constrained for toxicity design to determine the recommended phase II dose (RP2D), which was tested in phase II.Results:The Tcm cohort was closed early due to lack of activity. The 200 ×106 Tn/mem-derived CD19-CAR T-cell dose was found to be safe and active, and was declared the RP2D. At RP2D, 58 participants underwent leukapheresis and 46 received CD19-CAR T cells. Median age for treated participants was 38 years (range, 22–72). Twenty-nine (63%) participants had relapsed post-allogeneic hematopoietic cell transplantation (alloHCT), 18 (39%) had Philadelphia-like (Ph-like) genotype, and 16 (35%) had extramedullary disease (EMD) at lymphodepletion (LD). Three (7%) participants had grade 3 cytokine release syndrome (CRS), and none had grade ≥ 4 CRS. Eight (17%) participants had grade ≥ 3 neurotoxicity, including one fatal cerebral edema. Forty (87%) patients achieved complete remission (CR)/CR with incomplete hematologic recovery, 2 (4%) progressed, and 4 (9%) were unevaluable for response. Among 42 response-evaluable participants, 16/17 with Ph-like ALL and 13/15 with EMD at LD responded. Twenty-one (53%) responders underwent alloHCT consolidation, which was associated with improved relapse-free survival (adjusted HR = 0.16; 95% confidence interval, 0.05–0.48; P = 0.001).Conclusions:Tn/mem-derived CD19-CAR T cells were safe and active, including in Ph-like ALL and EMD.See related commentary by El Marabti and Abdel-Wahab, p. 694

Post-transplant cyclophosphamide (PTCy) combined with tacrolimus (TAC) as graft-versus-host disease (GvHD) prophylaxis post-hematopoietic cell transplantation (HCT) is safe and effective. Optimal serum levels of TAC in this combination remain undetermined. We hypothesized that TAC at initial steady state (TISS) of10 ng/mL could promote optimal transplant outcomes and prevent TAC-associated toxicities. We retrospectively analyzed a consecutive case series of 210 patients who received PTCy/TAC-based prophylaxis post-HCT from 1/2013-6/2018. Patients received HCT from haploidentical (n = 172) or mismatched donors (n = 38), and flat dose (FD) or weight-based dose (WBD) TAC. Twenty-four-month overall survival (OS), disease free survival (DFS), and relapse rate (RR) were 61%, 56%, and 22%, respectively, in TISS 10 ng/mL cohort (n = 176), and 50%, 43%, and 35%, respectively, in TISS ≥ 10 ng/mL cohort (n = 34) (OS, P = 0.71; DFS, P = 0.097; RR, P = 0.031). OS, DFS, RR, non-relapse mortality, acute GvHD grade II-IV, grade III-IV or chronic GvHD by TISS were similar in multivariable analysis. TISS ≥ 10 ng/mL conferred increased risk of viral infection (P = 0.003). More patients receiving FD vs. WBD had TISS 10 ng/mL (P = 0.001). Overall, TISS 10 ng/mL early post HCT conferred similar survival outcomes and lowered risk of viral infection and toxicities compared to TISS ≥ 10 ng/mL.

Data on pretransplantation minimal residual disease (MRD) and outcomes of umbilical cord blood transplantation (UCBT) are limited. Out of the 143 patients with acute lymphoblastic leukemia (ALL) who underwent UCBT at the University of Minnesota between 2004 and 2010, we evaluated 86 patients with available MRD assessment data by 4- and 8-color flow cytometry analysis immediately before transplantation. Ten patients (11.6%) were MRD-positive, and 76 were MRD-negative (88.4%). Most of the patients (82%) received myeloablative conditioning. GVHD prophylaxis consisted of cyclosporine and mycophenolate mofetil. In multivariate analysis, age, disease status (complete remission [CR] 1 versus CR2/CR3), disease group (precursor B cell ALL versus Philadelphia chromosome–positive ALL versus T cell ALL), and time to transplantation had no impact on relapse. Patients with MRD before UCBT had a greater incidence of relapse at 2 years (relapse rate, 30%; 95% confidence interval [CI], 4%-56%) and lower 3-year disease-free survival (30%; 95% CI, 7%-58%) compared with those without MRD (relapse rate, 16%; 95% CI, 8%-25%; P = .05; disease-free survival, 55%; 95% CI, 43%-66%; P = .02). Our data suggest that in patients with ALL, achieving an MRD-negative state before UCBT improves outcomes.

Umbilical cord blood (UCB) has increased access to hematopoietic-cell transplantation (HCT) for patients without HLA-matched sibling donors (MSD). We compared outcomes of HCT using MSD (N=38) or UCB (N=60) among older patients (age ≥55 years) with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS). All patients received a reduced intensity regimen consisting of cyclophosphamide, fludarabine and 200 cGy total body irradiation. Median age at HCT was 63 years for MSD and 61 years for UCB recipients. Among UCB recipients, 95% received two UCB units and 88% received 1–2 locus HLA mismatched units to optimize cell dose. Overall survival at 3-years was 37% for MSD and 31% for UCB recipients (P=0.21). On multivariate analysis, donor source (MSD vs. UCB) did not impact risks of overall survival, leukemia-free survival, relapse or treatment-related mortality. UCB is feasible as an alternative donor source for RIC HCT among older patients with AML and MDS who do not have a suitable MSD.

CD20 expression is associated with early recurrence and inferior survival in precursor-B acute lymphoblastic leukemia patients treated with chemotherapy. Whether CD20 influences outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unknown. We analyzed CD20 expression on blasts at diagnosis in 157 patients who underwent allo-HSCT in the first complete remission (57%) or the second complete remission (43%). Of 125 evaluable patients, 71 were ≥ 20 years of age. CD20 expression was observed in 58 patients (46%; 52% of children, 39% of adults). There was no association between age, Ph+ status, white blood cell count at diagnosis, and CD20 positivity. After allo-HSCT, disease-free survival at 5 years was 48% for all patients, 55% (95% confidence interval 40%-67%) for CD20+ patients, and 43% (95% confidence interval 30%-54%) for CD20− patients (P = .15). Relapse did not differ between the groups. These results can serve as a reference to evaluate incorporation of anti-CD20 therapeutics to HSCT for the CD20+ acute lymphoblastic leukemia subset. Clinical trial numbers for www.clinicaltrials.gov are NCT00365287, NCT00305682, and NCT00303719.

Compared to other hematopoietic stem cell sources, UCB carries an increased risk of graft failure (GF), a life-threatening complication of transplant. Timely recognition of GF could help plan potentially curative salvage therapy, such as second grafting [Ruggeri et al, Haematologica 2014]. This study was aimed at identifying patients at high risk of GF. We hypothesized that early chimerism results might be a useful prognosticator. Therefore, we examined the results of day 21 bone marrow (BM) and peripheral blood (PB) chimerism testing in 327 (123 single UCB and 204 double UCB) patients receiving myeloablative conditioning (2000-2013) for various hematological malignancies. Recursive partitioning analysis was used to determine the optimal cut off of day 21 chimerism for neutrophil engraftment. Chimierism ≥85% was observed in 283 and 21 days without evidence of disease relapse the incidence of neutrophil recovery was 92% (95% CI 89-95%) by day 42. However, for those with Disclosures No relevant conflicts of interest to declare.

Abstract 1681 The heterogeneous expression of CD20 antigen on leukemic blasts may harbor prognostic value and therapeutic potential. CD20 positivity (CD20+) has been recently associated with disease recurrence and shorter overall survival in adults with pre-B acute lymphoblastic leukemia (ALL). The influence of CD20 expression on outcomes following allogeneic donor hematopoietic stem cell transplantation (HCT) is not known. Results: We analyzed CD20 expression on pre-B ALL marrow blasts at diagnosis in 157 consecutive patients who underwent allogeneic HCT in first or second complete remission (CR) from 1999–2010. Thirty-two patients with no available flow cytometry data were excluded. Out of 125 evaluable patients, 52 (42%) were < 20 years of age; 73 (58%) were ≥20. All patients had high risk ALL and were in CR at HCT (57% in CR1, 43% in CR2). A majority of patients were Ph+ (60%) and received myeloablative conditioning (84%). Grafts were from sibling (36%), unrelated umbilical cord blood (UCB) (59%) and matched adult URD (5%). CD20+, defined as >20% expression on marrow blasts, was observed in 58 (46%) patients. 55% of children and 39% of adults were CD20+ and expression was similar in CR1 & CR2. Gender, donor source (sibling vs UCB), patient CMV serostatus, cytogenetics (Ph+ vs other), and conditioning (myeloablative vs reduced intensity) was similar in CD20+ and CD20- groups. Disease-free survival (DFS) at 3 years was 48% (95% CI 39–57%) for all patients; 42% (95% CI 30–54%) for CD20- patients, and 55% (95% CI 40–67%) for CD20+ patients (p=0.14). CD20+ expression did not significantly impact relapse rate or DFS in adults (Table) while in patients Conclusion: Pre-B ALL with a CD20+ immunophenotype reportedly confers higher risk of disease recurrence and unfavorable OS with conventional chemotherapy. Our data demonstrates that the poor prognosis associated with CD20+ ALL blasts is overcome by allogeneic HCT. In addition, post-HCT survival is promising in both adults and children, independent of CD20 expression. CD20 targeting monoclonal antibodies may further improve these outcomes. Disclosures: No relevant conflicts of interest to declare.