Shah, Nirali N

Background Hematologic toxicities, including coagulopathy, endothelial activation, and cytopenias, with CD19-targeted chimeric antigen receptor (CAR) T-cell therapies correlate with cytokine release syndrome (CRS) and neurotoxicity severity, but little is known about the extended toxicity profiles of CAR T-cells targeting alternative antigens. This report characterizes hematologic toxicities seen following CD22 CAR T-cells and their relationship to CRS and neurotoxicity. Methods We retrospectively characterized hematologic toxicities associated with CRS seen on a phase 1 study of anti-CD22 CAR T-cells for children and young adults with relapsed/refractory CD22+ hematologic malignancies. Additional analyses included correlation of hematologic toxicities with neurotoxicity and exploring effects of hemophagocytic lymphohistiocytosis-like toxicities (HLH) on bone marrow recovery and cytopenias. Coagulopathy was defined as evidence of bleeding or abnormal coagulation parameters. Hematologic toxicities were graded by Common Terminology Criteria for Adverse Events V.4.0. Results Across 53 patients receiving CD22 CAR T-cells who experienced CRS, 43 (81.1%) patients achieved complete remission. Eighteen (34.0%) patients experienced coagulopathy, of whom 16 had clinical manifestations of mild bleeding (typically mucosal bleeding) which generally subsided following CRS resolution. Three had manifestations of thrombotic microangiopathy. Patients with coagulopathy had higher peak ferritin, D-dimer, prothrombin time, international normalized ratio (INR), lactate dehydrogenase (LDH), tissue factor, prothrombin fragment F1+2 and soluble vascular cell adhesion molecule-1 (s-VCAM-1). Despite a relatively higher incidence of HLH-like toxicities and endothelial activation, overall neurotoxicity was generally less severe than reported with CD19 CAR T-cells, prompting additional analysis to explore CD22 expression in the central nervous system (CNS). Single-cell analysis revealed that in contrast to CD19 expression, CD22 is not on oligodendrocyte precursor cells or on neurovascular cells but is seen on mature oligodendrocytes. Lastly, among those attaining CR, grade 3–4 neutropenia and thrombocytopenia were seen in 65% of patients at D28. Conclusion With rising incidence of CD19 negative relapse, CD22 CAR T-cells are increasingly important for the treatment of B-cell malignancies. In characterizing hematologic toxicities on CD22 CAR T-cells, we demonstrate that despite endothelial activation, coagulopathy, and cytopenias, neurotoxicity was relatively mild and that CD22 and CD19 expression in the CNS differed, providing one potential hypothesis for divergent neurotoxicity profiles. Systematic characterization of on-target off-tumor toxicities of novel CAR T-cell constructs will be vital as new antigens are targeted. Trial registration number NCT02315612 .

Introduction: Cryopreservation of peripheral blood stem cell (PBSC) or bone marrow (BM) grafts is rarely performed, thus information about the effect of cryopreservation on graft characteristics and HCT outcomes is limited. Given the global pandemic leading to changing practices for donor graft collection and increasing utilization of cryopreservation, we evaluated the outcomes of HCT recipients who received either fresh or cryopreserved allogeneic BM or PBSC grafts. The primary endpoint was engraftment. Secondary endpoints were incidence of acute graft-vs.-host disease (aGVHD), relapse, transplant related mortality (TRM), disease free survival (DFS), and overall survival (OS). Methods: We included 7397 patients transplanted between 2013 and 2018. 1883 cryopreserved graft recipients were divided into three cohorts based on graft source and donor type: matched related (MRD) PBSC (n=1,051), matched unrelated (MUD) PBSC (n=678), and matched related or unrelated bone marrow donors (n=154). All patients received conventional calcineurin-based GVHD prophylaxis strategies. Patients who received cryopreserved grafts were matched with 5514 patients who received fresh adjusting for graft type (BM vs. PB), donor source (MRD vs. 8/8 MUD), Disease Risk Index (DRI, low risk vs. intermediate risk vs. high risk), recipient age (within 5-years) and propensity score (within 1 standard deviation from pooled sample). The propensity score was based on age, Karnofsky score, diagnosis, disease risk index, HCT-comorbidity index, and conditioning intensity. The level of statistical significance for the main analyses was p<0.01 due to multiple comparisons. The reason for cryopreservation was available on a subset of URD product recipients. Results: Baseline characteristics for all cohorts are shown in Table 1. CD34+ doses reflect enumeration at infusion. In univariate analyses, rates of graft failure and neutrophil recovery at day 28 were similar for cryopreserved and fresh grafts for BM or related PBSC recipients but differed in cryopreserved vs. fresh MUD PBSC (5% vs 2%, p<0.001 and 87 vs 94%, p<0.001, respectively). Rates of platelet recovery within 28 days were similar in marrow cohorts, but lower with cryopreserved related (92% vs 96%, p<0.001) and MUD PBSC (87 vs 94%, p<0.001) grafts. In matched pair multivariable analyses, there were no significant differences in any outcomes with cryopreserved vs fresh BM grafts, irrespective of donor type. With related donor PBSC, cryopreservation was associated with decreased platelet recovery (HR=0.73, CI=0.68-0.78, p<0.001) and an increased risk of both grade II-IV (HR=1.27, CI=1.09-1.48, p=0.002) and grade III-IV (HR=1.48, CI=1.19-1.84, p<0.001) aGVHD, but had no impact on other outcomes. In contrast, with MUD PBSC grafts, cryopreservation was associated with delayed engraftment of neutrophils (HR=0.77, CI=0.71-0.84, p<0.001) and platelets (HR=0.61, CI=0.56-0.66, p<0.001), an increased risk of TRM (HR=1.4, CI=1.18-1.66, p<0.001) and relapse (HR=1.32, CI=1.11-1.58, p=0.002), and decreased DFS (HR=1.36, CI=1.20-1.55, p<0.001) and OS (HR=1.38, CI=1.22-1.58, p<0.001) but did not affect the incidence of aGVHD. In a subset analysis of 299 URD recipients, the most common reason for cryopreservation was delays due to patient-related events, eg., additional chemotherapy, infection. These recipients had decreased OS compared to products cryopreserved for non-patient reasons (HR=0.65, CI=0.44-0.96, p=0.029). Conclusions: The retrospective nature of this analysis, and the fact that cryopreservation is likely to have been performed in recipients with a different (higher) risk profile compared to those receiving fresh products limits our ability to draw firm confusions. Despite these limitations, we conclude that cryopreservation in some patient populations may have a negative impact on engraftment and transplant outcomes. The decision to cryopreserve donor grafts, particularly PBSC grafts, should be carefully considered and highlights the need for further investigation of the effect of cryopreservation of allogeneic grafts where patient factors can be controlled for. Disclosures Farhadfar: CSL Behring: Research Funding; Incyte pharmaceutical: Other: Member of GVHD advisory forum. Frey:Kite Pharma: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Syntax: Consultancy, Honoraria. Devine:Magenta Therapeutics: Consultancy. Shaw:Orca Bio: Consultancy. Wingard:Shire: Other: Personal Fees - serve on data monitoring committee for clinical trial; Ansun: Other: Personal Fees - serve on data monitoring committee for clinical trial; Merck: Other: Personal Fees - serve on data monitoring committee for clinical trial; Cidara: Other: Personal Fees - serve on data monitoring committee for clinical trial; ReViral: Other: Personal Fees - serve on data monitoring committee for clinical trial.

Background: Early data from anti-CD19 chimeric antigen receptor (CAR) T-cell trials suggest that concurrent infection can lead to poor outcomes. 1,2 The relationship between CAR T-cell mediated inflammatory responses and infections is not well-established. With CAR T-cell therapies more readily available, practitioners must identify which patient, disease and CAR T-cell specific parameters are associated with an increased risk of infection to optimize outcomes. We provide a comprehensive analysis of infection risk within the first 30 days after CAR T-cell infusion across multiple types of CAR T-cell trials targeting distinct antigens. Methods: This was a single-center, retrospective study conducted at the National Cancer Institute analyzing infectious complications in subjects who underwent CAR T-cell therapy on one of four phase I clinical trials, targeting CD19, CD22, B-cell maturation antigen (BCMA) or disialoganglioside (GD2) from 2012 though 2018. Baseline characteristics are in Table 1. The primary objective was to establish the incidence of infections between initiation of lymphodepleting (LD) chemotherapy through day 30 after CAR T-cell infusion. The secondary objective was to identify risk factors for infection. Patients were censored at relapse and/or initiation of alternative therapy, including treatment for relapse or consolidative hematopoietic stem cell transplantation (HSCT). Univariate screening methods were used to identify parameters associated with increased risk of infection Results: Amongst 144 subjects, 52 (36.1%) received anti-CD19 CAR T-cells (CAR-T); 53 (36.8%) received anti-CD22 CAR-T, 26 (18.1%) received anti-BCMA CAR-T; and 13 (9%) received anti-GD2 CAR-T. The median age was 18 years (range: 4 to 66). Sixty-one (42.4%) had undergone at least one prior allogeneic hematopoietic stem cell transplant (HSCT) and 24 (16.7%) had at least one prior autologous HSCT. Sixty-eight (47.2%) had a history of a recent infection within 100 days of initiation of LD chemotherapy, of which 17 were a major chronic infection and 9 were considered severe. Fifty-eight (40.3%) subjects experienced a total of 103 infections from initiation of LD chemotherapy through day 30 post CAR T-cell infusion, with the median time to first infection being 6 days post-CAR infusion. Twenty-eight (19.4%) subjects had more than 1 infection; 20 (13.9%) subjects had C. difficile infection. The 103 infections consisted of 47 (45.6%) distinct episodes of focal bacterial infections (e.g., sinusitis, pneumonia, urinary tract infection), 25 (24.2%) episodes of bacteremia, 22 (21.4%) viral infections, and 9 (8.7%) invasive fungal infections. Fourteen infections (13.6%) occurred between initiation of LD chemotherapy and day 0 (prior to CAR T-cell infusion). Fever and neutropenia, without a source, was documented as a distinct entity in 85 patients (59.0%). Using univariate statistical screening methods, we identified 4 parameters that were individually associated with an increased risk of infection: increasing number of prior therapies (p=0.0034), prior history of recent infection within the past 100 days (p=0.0064), age > 18 (p =0.028), or enrollment on the CD22 CAR trial (p=0.0028). Eliminating the trial, since that is not generalizable, and combining these into a multivariable logistic regression model identified age > 18, prior history of infection and prior lines of therapies jointly associated with an increased risk of infection. Using these parameters, a predictive model was developed, which, when applied to the data set used to develop the model, can correctly predict 69 of 86 patients without an infection (80.3%; CI: 70.3-88.0%) as well as 32 of 58 patients with an infection (55.2%; 95% CI: 41.5- 68.3%). Conclusion: In this retrospective analysis, we provide the largest experience to date analyzing infection in the setting of CAR T-cell therapy across multiple CAR constructs. Our study demonstrates that adult age, prior history of infection, increased number of prior therapies and enrollment on a particular CAR T-cell trial, in this case the CD22 CAR-T trial, may lead to a higher risk of infection than in those without these risk factors. Further investigations are underway to evaluate clinical outcomes with infection which occur in the peri CAR T-cell setting and potential strategies to minimize infection risk. Generalizability of this model will be tested in an independent data set. Disclosures Lee: Kite, a Gilead Company: Research Funding; Harpoon Therapeutics: Consultancy; Juno Therapeutics: Other: External Advisory Board; ACI Clinical on behalf of Celgene:: Other: Independent Central Quality Review Committee. Mackall:Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Kochenderfer:Kite and Celgene: Research Funding; Bluebird and CRISPR Therapeutics: Other: received royalties on licensing of his inventions. OffLabel Disclosure: Conditioning chemotherapy for CAR T-cell therapy; this is a retrospective study that used different lymphodepletion regimens.

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.