ALBERT

Description: Background: Chimeric antigen receptor T-cell (CAR T) immunotherapy is an evolving treatment for relapsed/ refractory non-Hodgkin lymphoma (NHL) and multiple myeloma (MM). There is a growing need to elucidate the infectious complications of BCMA- and CD19-directed CAR T therapy. We performed a single-center retrospective analysis of infection outcomes up to 1-year post BCMA and CD19-directed CAR T treatment. Methods: All patients treated at our institution with a BCMA-directed CAR T therapy for MM or with a CD19-directed CAR T for NHL from 2018-2020 were analyzed for risk factors for infection and infectious complications. Bacterial, viral and fungal infections were recorded if there was a microbiologic or histopathologic diagnosis or if clinical suspicion for infection required empiric treatment. Infection severity was classified as mild, moderate, severe, life-threatening, or fatal as previously described (Young et al. 2016, van Burnik et al. 2007). Infections were identified from the day of the first CAR T-cell infusion up to 1 year after infusion. Observation of infections was terminated at the time of disease progression, initiation of next therapy, or death, whichever occurred first. Fisher's exact test and Wilcoxon rank-sum test were used to compare between cohorts. Poisson mixed effects model with a subject-specific random intercept and an offset to account for the duration at risk was used to identify risk factors for infections. Results: Of the 104 subjects in this study, 55 patients (53%) had MM treated with BCMA CAR T and 49 patients (47%) had NHL treated with CD19 CAR T. Median number of prior therapies was 6 (4 - 9) in the BCMA cohort and 3 (2-4) in the CD19 cohort (Table 1). Prior to starting lymphodepleting (LD) chemotherapy, most patients did not have IgG〈 400, ALC〈 200, or ANC〈 500. Almost all the patients were on antibacterial (99%), antiviral (99%) and antifungal (92%) prophylaxis (ppx), with 18%, 90% and 9% of patients starting this before LD chemotherapy, respectively. Median follow-up time was 5.8 months (95% CI: 4.2-6.4). In total, there were 87 infection events (48 bacterial, 33 viral, and 6 fungal) observed in 56 patients (54%), with 47 infections in 29 (53%) patients in the BCMA CAR T cohort and 40 infections in 27 (55%) patients in the CD19 CAR T cohort (p =0.9). The BCMA cohort had 19 bacterial (40%) vs 29 bacterial (73%) in CD19 cohort (p=0.005), while BCMA cohort had 25 viral (53%) vs 8 viral (20%) in CD19 cohort (p=0.002). Fungal infection rates were comparable between BCMA and CD19 cohorts, 3 (6%) vs 3 (8%) respectively (p=1). Among the infections that occurred, 20 (23%) were high severity occurring in 16 patients (15%) of the overall cohort. Four high severity infections (5%) occurred in 3 patients (5%) in the BCMA cohort while 16 high severity infections (18%) occurred in 13 patients (27%) in the CD19 cohort (p 〈 0.001) (Figure 1). The BCMA cohort had higher rates of respiratory infections (68% vs 50%, p=0.1), while the CD19 cohort had higher rates of bloodstream infections (15% vs 2%, p=0.05) and gastrointestinal infections (10% vs 0%, p=0.04). The rates of grade (Gr) 3-4 neutropenia and IgG 〈 300 in both the cohorts at various time points post CAR T were comparable. At 9-12 months, Gr 3-4 neutropenia was 7% vs 8% (p=1) and IgG 〈 300 was 7% vs 33% (p=0.1) for the BCMA and CD19 cohorts respectively. Adjusting for time periods, risk factors for development of infections were use of steroids (incidence rate ratio [IRR] 1.6, 95% CI: 1.1-2.5, p=0.03) and post CAR T hypogammaglobulinemia (IgG 〈 600) (IRR =2.1, 95% CI: 1.2-3.9, p=0.02). Conclusions: This retrospective study is one of the largest studies to date comparing the post CAR T infections rates between BCMA and CD19 directed CAR T treated patients. While the incidence of infection, use of antimicrobial ppx, and rates of Gr 3-4 neutropenia and hypogammaglobulinemia were comparable between BCMA and CD19 CAR T cohorts, viral infections were more common post BCMA CAR T while bacterial infections were more frequent post CD19 CAR T. Use of steroids as well as post CAR T hypogammaglobulinemia are possible risk factors for development of infections. Further studies are needed to examine the infectious complications post-CAR T treatment, characterize the underlying risk factors, and to establish appropriate prophylactic approaches in patients undergoing CD19- and BCMA-directed CAR T therapy. Disclosures Fakhri: University of California San Francisco: Current Employment. Ai:Nurix Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics, Kymera: Membership on an entity's Board of Directors or advisory committees. Martin:Seattle Genetics: Research Funding; GSK: Consultancy; Sanofi: Research Funding; AMGEN: Research Funding; Janssen: Research Funding. Wolf:Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Shah:BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding; GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy. Andreadis:Genentech: Other: Spouse Employee (salary and stock); Novartis: Research Funding; Celgene/Juno: Research Funding; Amgen: Research Funding; Merck: Research Funding; Gilead/Kite: Other: Advisor; Jazz Pharmaceuticals: Other: Advisor; Astellas: Other: Advisor; Seattle Genetics: Other: Advisor; Karyopharm: Other: Advisor; Incyte: Other. Wong:GSK: Research Funding; Amgen: Consultancy; Sanofi: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Research Funding; Roche: Research Funding; Janssen: Research Funding; Fortis: Research Funding.

Description: Introduction: Adeno-associated virus (AAV) mediated gene transfer is currently evaluated in multiple Phase I/II and Phase III studies for the treatment of hemophilia. However, immune responses to both the AAV capsid and encoded transgene remain major impediments to clinical translation. Several studies have implicated innate immune sensors such as Toll-like receptors (TLR) and their downstream adaptor molecule MyD88 in sensing viral structures. TLR9-MyD88 signaling has been linked to cross-priming of CD8+ T cell responses to capsid and also to transgene product-specific CD8+ T cell responses. However, little is known about other signaling pathways that may lead to immune activation. Previously, our lab has shown that while liver gene transfer is capable of inducing immunological tolerance to AAV encoded transgene products, vector dose and design play a critical role. For instance, low hepatic gene expression levels may elicit a CD8+ T cell response to the AAV encoded transgene, resulting in loss of the model antigen ovalbumin (OVA) in C57BL/6 mice or of FIX expression in hemophilia B mice. We investigated innate immune sensing pathways that may play a role in initiating transgene specific CD8+ T cell response in the hepatic microenvironment. Further, we determined the contribution of hepatic antigen presenting cells (APC) by selectively depleting/neutralizing APCs and evaluating their effect on presentation of transgene product-derived antigen following AAV8-OVA liver gene delivery. Methods: Wild-type (WT) C57BL6 and specific innate sensing knockout mice on the C57BL6 background were intravenously (IV) injected with a predetermined immunogenic dose (1x109vg) of hepatotropic AAV8-OVA vector (Mol Ther 25:880, 2017). PBMCs were quantified at 4 weeks for OVA-specific CD8+ T cells using a class I MHC tetramer. Hepatic APC types [Kupffer cells, neutrophils, CD103+ dendritic cell (DC), CD11c+ DC, XCR1+ DC] involved in transgene specific CD8+ T cell activation were selectively depleted/inactivated by pre-treatment with gadolinium chloride (GdCl3), Ly6G, CD103 antibody respectively, or by administering diphtheria toxin (DT) to CD11c-DTR and XCR1-DTR mice. This was followed by intravenous administration of AAV8-OVA and CellTrace violet labeled OT-1 cells. Results: Similar to WT mice, TLR9-/-, TLR2-/-, TRIF-/-, IFNaR-/- and MDA5-/- mice developed a CD8+ T cell response indicating that these sensors do not play a role in transgene specific CD8+ T cells response. Interestingly, adaptor protein MyD88-/- mice did not elicit CD8+ T cell response to OVA, implying a MyD88 dependent but TLR9 independent response. Since MyD88 is an essential adaptor protein not only for TLR but also for interleukin-1 (IL-1) signaling pathways, we next analyzed IL-1R-/- mice. Similar to MyD88-/- mice, IL-1R-/- mice did not show OVA specific CD8+ T cells (p=0.006, 0.007 respectively), indicating that transgene-specific adaptive responses are mediated by IL-1R/MyD88 signaling. Kupffer cells and DCs are principal APCs in liver and infiltrating neutrophils could also act as APCs under inflammatory conditions in liver microenvironment. Using proliferation of OT-I cells as readout we tested if any of these cell types are required for presentation to transgene specific CD8+ T cells. In naïve control, GdCl3 treated and a-Ly6G antibody treated mice, OT-I cell proliferation reached 60%, 65% and 48% on average, respectively. Depletion of CD11c DCs substantially reduced the proliferation of OT-I cells to ~6% (p

Description: A serious complication in the treatment X-linked bleeding disorder hemophilia A is the formation of inhibitory antibodies against factor VIII (FVIII), which compromise traditional replacement therapy. We previously developed an Oral immunotherapy (OTI) based on repeated uptake of a mixture of lettuce plant cells transgenic for heavy chain (HC) or C2 domain of human FVIII fused to cholera toxin B (CTB) subunit [Blood 124:1659; Plant Biotechnol J. 16:1148]. Fusion proteins were transgenically expressed in the chloroplasts. Repeated oral uptake of a mixture of freeze-dried powder of lettuce cells accomplished antigen delivery to the immune system of the small intestine by targeting of the GM1 receptor that is highly expressed on the surface of the gut epithelium, resulting in induction of regulatory T cells (Treg) that suppress inhibitor formation upon subsequent intravenous (iv) FVIII replacement therapy. An alternative to oral antigen delivery is the oral delivery of immune modulatory antibodies. Here, we compared the plant cell-based method with oral delivery of anti-CD3, which has been successful in murine models of autoimmune disease and is currently evaluated in clinical trials. Unlike in iv administration, oral anti-CD3 does not systemically deplete T cells. Hemophilia A BALB/c mice (F8 e16 gene deletion) received oral gavage of a mixture of CTB-FVIII-HC/-C2 (1.5 µg/antigen) expressing lettuce leaf cells 2x/week for 9 weeks. Starting at 4 weeks into the experiment, 1 IU/mouse of BDD-FVIII (Xyntha) was given iv, once per week for 5 weeks. Alternatively, following a published protocol that was successful in other models, 5 µg of hamster anti-murine CD3 was given by oral gavage daily for 5 straight days, followed by 5 weekly iv injections of BDD-FVIII. Control animals (no OTI) developed inhibitors with an average titer of 18 ± 3 BU/ml (n=16). Of these, 88% were high-titer (i.e 〉5 BU/ml, up to 43 BU/ml). Inhibitor formation was significantly reduced in plant cell-treated mice (10 ± 2.5 BU/ml, n=17), with 47% showing no or low-titer inhibitors (

Description: Introduction : There has been an increase in number of alternative donor [Unrelated donor (UD) or Haploidentical (HIT)] transplants in recent years due to better graft vs. host disease (GVHD) prophylaxis and comparable outcomes with matched sibling transplants. However, viral reactivations frequently complicate these transplants and can lead to organ dysfunction, poor graft function and death. We aimed to analyze incidence, risk factors, and outcomes of viral reactivations in alternative donor transplants at our centre. Methods: All UD or HIT transplants performed between January 1st 2009 and February 29th 2020 were included in this retrospective analysis. Conditioning regimen used were either myeloablative (TBI based) or reduced intensity (fludarabine based). All patients received T cell replete grafts. Calcineurin inhibitors (with methotrexate or mycophenolate mofetil) were used for GVHD prophylaxis. Rabbit anti-thymocyte globulin (ATG) was used in UD transplants and post transplant cyclophosphamide was used in HIT. Cytomegalovirus (CMV) was monitored twice weekly from start of conditioning. Adenovirus (ADV), BK, Epstein Barr virus (EBV) were monitored weekly post engraftment. Monitoring was done by real time quantitative PCR in peripheral blood for CMV, EBV and in blood as well as urine for ADV and BK virus. Parvovirus and Human Herpes virus-6 (HHV-6) were monitored if clinically indicated. Viral reactivation was defined as 2 consecutive readings of 〉150 copies/mL. Monitoring was stopped after withdrawal of immunosuppressants and restarted with onset of GVHD or use of systemic steroids. Ganciclovir (GCV) was usually preferred for pre-emptive treatment of CMV. Cidofovir (CDV), foscarnet (FOS), artesunate (ART) or leflunomide (LEF) were used when GCV failed or was myelotoxic. Cidofovir was used for ADV disease. Intravenous immunoglobulin (IVIg) prophylaxis was used in all patients. Primary objective was to estimate the incidence of viral reactivation. Secondary objectives were to explore various risk factors associated with viral reactivations and determine their strength of association using odds ratio (OR). Results: Of 334 allogeneic transplants performed during this period, 87 were alternative donor transplants (26 UD and 61 HIT). Incidence of CMV reactivation was 80.5 % (92 episodes of CMV reactivations in 70 patients). Two in UD transplant and 4 in HIT developed CMV colitis. Acute GVHD was a significant risk factor for developing CMV reactivation (OR=4.32, 95% CI 1.3-13.6; p=0.013). Pre-emptive 1st line treatment with GCV was used in 59 episodes, ART in 10, LEF in 19, CDV and FOS was used in 1 and 3 episodes each. No deaths were attributed to CMV disease. Incidence of ADV reactivation was 26% (21 episodes in 80 patients tested). Four patients developed ADV disease and were treated with CDV (ADV colitis in 2, ADV cystitis in 1, and 1 had colitis with CNS involvement) of which 2 died. Use of ATG (OR 3.5, 95% CI 1.2 - 10; p=0.03) and presence of acute GVHD (OR 7.9, 95% CI 2.5- 25; p=0.0004) were significant risk factors of ADV reactivation. EBV reactivation was seen in 25 of 68 patients tested (incidence 36.7%).Two patients developed post transplant lymphoproliferative disorder requiring therapy with rituximab, of which 1 died. One out of 15 patients tested by qualitative PCR had HHV 6 reactivation and primary graft failure. BK viral reactivation was seen in 59 of 71 tested (incidence 83.1%). Grade I and II hemorrhagic cystitis (Droller's grading system) was seen in 12 and 11 patients respectively. Foley's catheterization with bladder irrigation was used in 3 patients and intravesical GCSF was given to 1 patient. Parvovirus infection was seen in 2 of 12 patients tested, of which 1 was given IVIg. Cumulative incidence of viral reactivations is shown in Figure 1. Viral reactivation characteristics and risk factors are shown in tables 1 and 2 respectively. Median OS for the cohort of 87 patients was 52 months. There was no statistically significant impact of viral reactivations on OS. Conclusion: Incidence of CMV reactivation is high (80%) in alternative donor HSCT and acute GVHD is a significant risk factor for CMV, ADV and EBV reactivation. Use of ATG is a significant risk factor for ADV reactivation. However, rates of ADV, BK virus, and EBV reactivation requiring intervention were low. Better prophylactic strategies are necessary for prevention of CMV reactivations in alternative donor transplants. Disclosures No relevant conflicts of interest to declare.